Angelisa F Abrizi

Enzo Goretti

Arthur Compin

Régis Céréghin0

Keywords: macroinvertebrates, functional diversity, bioassessment, freshwaters

In applied river ecology it is implicitly assumed that community structure is a surrogate for functional properties. To test this hypothesis, 26 sites were sampled for macroinvertebrates in a Central Italian stream system impacted by 13 trout farms (1 upstream and 1 downstream site per facility). We used a fuzzy-coding approach of biological traits combined with species distribution analysis. Trout farm locally impacted the structure of macroinvertebrate communities, but seriai disturbances at the stream system scale did not affect the overall regional diversity pattern.

Impacted sites had species with large body size, which fed upon microorganisms and fine detritus, and which showed asexual reproduction. Least impact sites hosted small-sized invertebrates showing sexual reproduction, and feeding upon plant material and/or algae.

Introduction

Anthropogenic disturbances strongly influence biodiversity in freshwater ecosystems [START_REF] Jenkins | Prospects for biodiversity[END_REF], leading to spatial discontinuities of predictable gradients and lasses of taxa [START_REF] Brittain | A review of the effect of river regulation on Mayflies (Ephemeroptera)[END_REF]. In river ecology, biological assessment tools of water policies such as the European Water Framework Directive 2000/60 rely on structural properties of communities (species richness or composition), although the ultimate goal is to preserve and/or restore the functioning of freshwater ecosystems.

However, one may expect functional shifts when species with particular traits are eliminated or replaced by others under the influence of any disturbance type [START_REF] Loreau | Biodiversity and ecosystem functioning: current knowledge and future challenges[END_REF]. Indeed, assuming that the biological assemblages of a river ecosystem integrate the spatial and temporal variability of aquatic habitats (TOWNSEND and HILDREW, 1994), invertebrate species with certain combinations of adaptations are believed to be selected by the local habitat conditions (TOWNSEND et al., 1997; HANQUET et al., 2004).

In freshwater ecosystems, macroinvertebrates constitute an important part of animal production, and are tightly integrated into the structure and function of their habitats ( organic matter processing, nutrient retention, food resource for vertebrates (ÜERTLI, 1993)). Thus, the diversity and functional structure of macroinvertebrate communities are expected to vary consistently in relation to disturbance patterns.

Fish farming represents one of the many economie activities that may have adverse consequences upon freshwater biodiversity. Specifically, fish farming may severely impact water quality downstream the facilities (BERGHEIM and SELMER-ÜLSEN, 1978;[START_REF] Carr | Fish-farm effluents in rivers. II. Effects on inorganic nutrients, algae and the macrophyte Ranunculus penicillatus[END_REF][START_REF] Gowen | Environmental impact of aquaculture activities[END_REF]. The extent of disturbance in the receiving rivers depends on the amount of water which is drained upstream from the farm, and on the effectiveness of the water treatment before the outlet [START_REF] Boaventura | Trout farm effluents: characterization and impact on the receiving streams[END_REF][START_REF] Boyd | Guidelines for aquaculture effluents management at the farm-level[END_REF]. Over the last 30 years, this type of activity has been intensified in Umbria (centralltaly) where 13 trout production units are located, with a production of about 23500 quintals per year, which corresponds to approximately 6% of the national production [START_REF] Goretti | Studio sull'acquacoltura nel territorio della Regione Umbria[END_REF]. These settings provide context to assess longitudinal changes in structural and functional attributes of biological communities in relation to seriai disturbances.

The Seriai Discontinuity Concept [START_REF] Ward | The intermediate-disturbance hypothesis: an explanation for biotic diversity patterns in lotie ecosystems[END_REF] describes the longitudinal modifications in abiotic and/or biotic parameters due to alterations of the river habitat. In the affected river section, the discontinuity can be "negative" (modifications towards upstream conditions) or "positive" (modifications towards downstream conditions). Sorne ecological studies evidenced discontinuities in the longitudinal distribution of the benthic fauna (e.g., [START_REF] Saltveit | E:ffect of a changed temperature regime on the benthos of a Norwegian regulated river[END_REF]CÉRÉGHINO and LAVANDIER, 1998 a, b;[START_REF] Céréghino | Influence of intermittent hydropeaking on the longitudinal zonation patterns of benthic invertebrates in a mountain stream[END_REF]; however, these works relied on the structural properties (species composition and/or species richness) of the studied communities only. Here, we predicted that changes in invertebrate diversity in relation to physical and chemical alterations would affect the biological trait combinations of those benthic communities [START_REF] Usseglio-Polatera | Longitudinal changes in macroinvertebrate assemblages in the meuse river: anthropogenic effects versus natural change[END_REF].

To test this hypothesis, 26 sampling sites were sampled for macroinvertebrates ( 1 upstream and 1 downstream site per fish farm), and for physical and chemical measurements. We used a fuzzy-coding approach of biological traits ( [START_REF] Usseglio-Polatera | Biological and ecological traits of benthic freshwater macroinvertebrates: relationships and definition of groups with similar traits[END_REF] combined with species distribution analysis, to bring out functional shifts in river communities in relation to community structure and habitat alteration. The results are discussed with reference to local-and watershed-scale changes within biological communities.

Methods

Study Area

Trout farming in Umbria is essentially concentrated on the Nera River basin. The Nera has its source in the upper Valnerina Valley (Marche, Italy, elevation 850 rn a.s.l.), and its totallength is 125 km. This karstic river slopes from the north east to the south west, where it flows into the Tevere River (elevation 48 rn a.s.l.). The River Nera stream system drains an area of 4200 km 2 (MEARELLI et al., 1996).

We selected twelve trout farms, along the Nera River and its five tributaries (Campiano, Sordo, Coma, Vigi, Casana), plus one farm located in the Clitunno River, in the catch basin of the Chiascio River. Bath the Nera and the Chiascio rivers are tributaries of the Tevere River (Fig. 1).

Depending on the trout farm, fish production is more or less intensive (150 to 15000 q yr-1 ). Ali trout farms have decantation basins, but only trout farm 9 has mechanical filters to treat the water released to the receiving stream. Their main characteristics are given in Table 1.

Field Data

We investigated 26 sampling sites (spring 2005 (sites 1-12) and spring 2008 (site 13)), i.e., one upstream and one downstream site per trout farm (about 100 rn above and below the facility). The sampling for bath sites of each trout farm was carried out during the same day. At each site, benthic invertebrates were sampled according to the mE protocol. The mE ("Indice Biotico Esteso") is the standardized bio1ogical index used by Italian administrations in charge of environmental surveys (Italian DL152/06); it was adapted by GHETTI (1997) from the "Trent Biotic Index" principle (WoooiWiss, 1964), which was originally designed for Great Britain. Semi-quantitative sampies of macroinvertebrates were taken at each site by intensive sweeping of a dipnet (mesh size 335 J.Lm) through the various microhabitats along a river transect. The total sampling time was 10 minutes for each site as a whole. In the laboratory, macroinvertebrates were sorted, preserved in 70% ethanol, keyed to genus or family, and finally enumerated [START_REF] Campaioli | Manuale peril riconoscimento dei macroinvertebrati delle acque dolci italiane[END_REF][START_REF] Campaioli | Manuale peril riconoscimento dei macroinvertebrati delle acque dolci italiane[END_REF][START_REF] Tachet | Invertébrés d'eau douce. Systématique, biologie, écologie[END_REF].

Samp1ing sites were then characterized using six physical and seven chemical variables. The physical variables were elevation a.s.l. (rn), stream order, distance from the source (km), stream width (rn), mean depth (rn), mean annual discharge (L sec-1 ) for each site (MEARELLI et al., 1996; LoRENZONI et al., 2003). The chemical variables were water temperature (DC), conductivity (IlS cm-1 ), pH, Oxygen (% saturation and mg L-1 ), Total Volatile Solids (TVS mg L-1 ) in the water and TVS% in the sediments for the assessment of organic matter. Temperature, conductivity, pH, and oxygen were measured with field instruments (OXI 320, LF 320 and pH 720 (WTW) probes) at the same time of the macroinvertebrates samplings. Additionally, water (20 litres) and sediment samples (500 grams) were collected to evaluate Total Volatile Solids (TVS) in laboratory.

Statistical Analyses

A Principal Component Analysis (PCA) was performed for the 13 physical -chemical variables recorded at the 26 sites. The aim of the PCA was to set up a first typology of sites based on environmental variables only, and to detect potentia1 discontinuities that could be related to the impact of fish farms. The coordinates of the sites on the most significant axes of the PCA were then used to classify sites into clusters using Ward's algorithm. Sites from each cluster were thus expected to define distinct areas with similar environmental characteristics.

Correspondence analysis (CA) was used to ordinate the sampling sites according to invertebrate abundances [START_REF] Jongman | Data analysis in community and landscape ecology[END_REF], thus summarizing the variability of the data, and providing insights for the discussion of the subsequent traits analysis. The significance of the axes was determined at P < 0.05 by testing the eigenvalues of the inertia matrix. Plots of the first two ordination axes usually capture most of the variance and consequent! y contain most of the information that is likely to be interpretable [START_REF] Aite | Comparing strengths of geographie and nongeographic classifications of stream benthic macroinvertebrates in the Mid-Atlantic Highlands[END_REF]. Samples which were neighbours in the scatterplots were expected to define habitats with similar species assemblages. Conversely, samples having a large distance to each other were expected to be distant in the feature space, according to macroinvertebrate assemblages. Categories for each biological trait were ordinal or nominal (Table 2). The species traits are: maximal potential size, life cycle duration, potential number of cycles per year, aquatic stages, reproduction, dispersal mode, resistance forms, respiration, locomotion, food, feeding habits, substrate (preferendum), current velocity (preferendum), trophic status (preferendum), temperature (preferendum), and saprobity (see Table 2 for an overview). Species traits information (available in [START_REF] Tachet | Invertébrés d'eau douce. Systématique, biologie, écologie[END_REF] was then structured using a fuzzy-coding technique [START_REF] Chevenet | A fuzzy coding approach for the analysis of long-term ecological data[END_REF]: scores ranged from '0', indicating 'no affinity' to '3' or '5', indicating 'high affmity' for a given species traits category. This matrix was studied by a 'Fuzzy Correspondence Analysis' (FCA) [START_REF] Chevenet | A fuzzy coding approach for the analysis of long-term ecological data[END_REF].

Finally, a simultaneous analysis of the two matrices ( species distributions and species traits matrices) was performed using co-inertia analysis (CoA) [START_REF] Dolédec | Co-inertia analysis: an alternative method for studing speciesenvironment relationships[END_REF]. This analysis studies co-structure by maximizing covariance between faunistic and biological traits ordination scores in the first two analyses [START_REF] Dray | Co-inertia analysis and the linking of ecological data tables[END_REF]. A Permutation test was used to check the significance of the resulting correlation between the two sets of data resulting from the two kind of analyses (CA and FCA) [START_REF] Dolédec | Co-inertia analysis: an alternative method for studing speciesenvironment relationships[END_REF].We carried out 100 co-inertia analyses of the taxonomie and biological traits data sets after random permutation oftheir rows. The RVvalues were calculated and the frequency distribution of the 100 random RV values for co-inertia between the two tables were elaborated. The test was significant when the observed value was in a class containing only few random values among the 100 possible. The objective is to determine the common structure between the two sets of data, and then to interpret differences in sampling sites in terms of combinations of biological traits of their communities [START_REF] Charvet | Biomonitoring through biological traits of benthic macroinvertebrates: perspectives for a general tool in stream management[END_REF]. All analyses were performed with R software [START_REF] Chessel | The ade4 package-!: One-table methods[END_REF]DRAY and DUFOUR, 2007;DRAY et al., 2007).

Results

Environmental Variables

The first two axes of the PCA carried out on environmental variable explained 58.35% of the overall variance (Fig. 2). Ward's algorithm helped to derive three clear clusters of sites (Fig. 2a), which were distributed along the upstream to downstream gradient, according to

... 9o•o• . . •••••••9u•••••: ïëiit•• . . . . . . . . . . . . . . .... ••• llU .t.
li. three types of streams: i) headwaters near the source of the River Clitunno ( cluster A, sites 13U and 13D), ii) small streams (lower stream order within the stream system) (cluster B, sites llU, llD, lU, lD, 2U, 2D, 3U, 3D, 4U, 4D, 5U, 5D, 6U, 6D, 8U, 8D), and iii) large rivers resulting of the junction ofthese streams (cluster C, sites 7U, 7D, 9U, 9D, lOU, lOD, 12U, 12D). Sites in cluster A (headwaters) were characterised by higher pH and conductivity values and higher mean depth. Sites in cluster B (streams) were located at higher elevations and had higher TVS concentrations. Sites in cluster C (ri vers) corresponded to the downstream sections of the system (higher distance from the source and stream order, larger river bed). -+ --+ ---

c:~•\ a ,/ 4U  0 11D  0 ] ••••• o 0  \ /.l !~~ 0 5 D ~U ...... / / .•. •••• 7 U  lOD 12D 12U ) \ 2U  3D 0 lD o  lU ...•. ••••••••• \ ...... o ... 7 •••D •••••••••••••••••••••••••••••••••••••• ....
+ -+ + -------- -+ -+ ---+ --------- -+ + -+ -+ --+ -- + ---+ ------- -+ - + + - + + + - + --- + -----+ -+ --+ ------ -+ -- -+ ----+ + --+ + -------------+ -+ - -+ -------------+ + + --+ + + + + + + + -+ + -+ + --+ -+ + + + + -- -+ + ++-+++++++++-++++-+-+ + + + +- -+ + -+
++++-+++++++++++++ + + + + + + + + + ---+ --+ --------+ -+ + ---+ + -+ + + --+ + + + + + -+ -+ + ---+ + --+ + -+ + -+ -+ -+ + + + + + + + + + + -+ + + + + + + + + + + + + + + + + + + + + + + + + +

--+ + + + -+ -+ ------- +-+---++++++++++ + + ---+ -- +--+-+--+++++-++ + + --+ + -- -+ - -+ + + --+ + + -- +++++++++++ +-+ + + +- -+ - ++-+++++-++++ + ------- +-+++-++++++++++ + ---+ + -- -+ - + -+ - Table 3. (Continued)
Taxa 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 ----+ + ----+ + + + + + + + + + ---+ --

Dinocras cephalotes

----+ -------+ + + + + + + + --+ + -- Isoperla sp.

--+ -+ -+ -+ -+ + + + -+ + -----+ ---Leuctra sp.

---+ ------+ ----------+ ---- Nemoura sp.

-

+ + + + + -+ + + ----+ + ---------- Perla marginata ------------------- - - - + + -- Protonemura sp.
--+ + -+ --+ -----+ -----------Siphonoperla sp.

--+ -----------------------

Heteroptera

Nepa sp.

------------------+ -------

Coleoptera

Elmis sp.

----+ --+ --+ + + + + + + + + + + -+ + -- Esolus sp.

------------+ -----------+ -Gyrinus sp.

-

------------------ - - - - + --
Hydrophilus sp.

--------+ -----------------Limnius sp.

+ + + -+ + + -+ -+ + + + + -+ + + + --+ + --

Me gal optera

Sialis sp.

+ --------------------+ ---- Diptera Atherix sp.

---+ + + -----+ + + + + + + + + --+ + -- Ceratopogonidae undet.

------+ + + + + + -+ + + + + + + + ---+ + Chironomini undet.

+ + --+ + + + + + + + + + + + -+ -+ + + + + -+ Diamesinae undet.

+ -------------------------Dixa sp.

----+ ---------------------Dolichopodidae undet.

+ -------------------------Hexatomini undet.

--------+ ---+ -----+ -----+ -Limoniini undet.

-+ -------------+ + + -+ --+ + -- Orthocladiinae undet.

+ + -+ -+ + + + + ---+ + + ---+ -+ -+ -+ Pediciini undet.

-+ --+ + --+ -----+ + ---+ + -+ + --Ptychopteridae undet.

-+ ------------------------Simuliini undet.

-+ + + + + --+ + + ---+ -+ + + + --+ + -- Stratiomyiidae undet.

--+ -+ -----+ ---------------Tabanidae undet.

--------------------+ ----- Tanypodinae undet.

-+ ----+ -+ + + + + + + + + + ---+ --+ - Tanytarsini undet.

-+ -+ --+ --+ + + --+ + ---+ -+ + --+ Tipulidae undet.

+ + + ---+ -----+ -+ ----------- 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 .•"'ë)'"""" ......... .. The environmental parameters indicating water quality are positively related to the first axis ( oxygen) and negatively related to the second axis (TVS). The first axis (34.04%) was positively correlated with the above-mentioned river types. Because the autodepurative power of the water course limits the pollution load from the facilities, downstream (impacted) sites remained located within the cluster which delineated the corresponding riverine typology. Within a given cluster, the site located downstream from each trout farm is placed, normally, on the left side of the corresponding upstream site. However, the second axis (24.31%) pointed out the worsening of water quality downstream each trout farm generally placing (with the exception of the particular site 13) downstream sites D down to their corresponding upstream sites U in the scatterplot.

"1 -\ 130 •••••••••••• ~-"~0 ~--'--, "1 - ••••••••••••••• llU 13~••• ... 0 •••••••••• ........... ~ ....... :~) ;,::•••~;1 ! o 0 9o j ~-r------------------------~~• •" _ .. _ ... _ .. _ ... _ .. • _•• ~•ñ "n ' r"-"•_ ... ~ .. • ~-----+ [ -l _o _u •õ•12U -7/_ • ~ ~- -2.0 -1.5 Ph ys a . ...-•i•~ su .o • 3 •••u •••••... \ 7U ~LU •••• ••• : : : . . /•• o 4u • su• ••.

Species Distribution

When a CA was carried out on the species matrix (abundance of 88 taxa (31,166 specimens) belonging to the 26 sites, see Table 3) the frrst two axes contributed 19.46% and 13.68% to the overall variance, respectively (Fig. 3). The scatterplot of the sampling sites (Fig. 3) using the first two axes of the CA had an "arch" shape. Such a pattern (also called Guttman effect) occurs when variables progressively change along an ecological gradient [START_REF] Legendre | Numerical Ecology[END_REF]. Scatterplot of the first two ordination axes indicated that sampling sites were primarily distributed according to their location within the stream system [START_REF] Finn | Variability and convergence in benthic communities along the longitudinal gradients of four physically similar Rocky Mountain streams[END_REF]. Those sites located on the main course (River Nera, pairs of sites 9, 10, 12) and on its main tributary (River Corno, 7U), with a mean discharge ranging from 4 to 5 m 3 s-1 , were grouped in the right-top area of the plot. Sites which were located nearby the river sources were grouped in the left-top area (11, 13), while the remaining sites, which belonged to the Nera tributaries (River Corno 7D, Sordo, Vigi, Campiano), formed an intermediate cluster (Fig. 3a). It should be noted that the impacted site 7D (Corno River), which receives the outlet from the largest trout farm, is included in the intermediate cluster. At this site, the autodepurative power of Corno River is partially impaired even though its flow (5.5 m 3 s-1 ca) is higher than that detected for Nera River below the facilities (Fig. 1). In fact, in this sector of Nera River, the flow value (3.9 m 3 s-1 ca) reflects the water uptake for hydroelectric power.

Finally, the CA showed downstream changes in the longitudinal zonation ofbenthic invertebrate taxa (see Fig. 3b, from right to left), with a typical transition from lotie (Hydrobiidae, Dinocras, Perla, Lepidostoma, Micrasema, Serratella, Epeorus [right]) to lentic taxa (e.g., Physa, Tubificidae, Helobdella, Lymnaea, Sialis [left]) in the stream system.

Spatial Patterns of Macroinvertebrate Traits

A permutation test indicated that the co-inertia between the species distributions and species traits matrices was highly significant (RV = 0.54; P < 0.001). The frrst two axes of the CoA explained 43.14 and 17.71% to the overall variance, respectively. The co-inertia analysis (Fig. 4) of taxa distributions and their biological traits made it possible to derive sorne spatial patterns of species traits combinations within the stream system (UssEGLIO- [START_REF] Usseglio-Polatera | Longitudinal changes in macroinvertebrate assemblages in the meuse river: anthropogenic effects versus natural change[END_REF]. Sorne traits did not appear as clearly structuring (e.g., life cycle duration, dispersal, temperature). However, other traits did well in structuring the scatterplot.

At the right bottom corner of the scatterplot, biological traits cl earl y separated the upstream (5U) and downstream sites (5D) located in the upper Sordo River. These sites, together with pair of sites 4 and site 7D, were chiefly characterized by species, with large bodies (a6, a7), deposit feeders (k2) and absorbers (k1) consuming microorganism G1) and small detritus (a)

... (< 1 mm) (j2), asexual reproduction (e8) and the ability to form cocoons as resistance forms (g2), respiration through tegument (hl), and interstitial microhabitats (i6).

In the right upper corner, pairs of sites 11 and 13 were characterized by parasites (k:8) feeding upon large prey items (j9), mainly attached organisms (i8), ovoviviparity (el), eggs laid as clutches or free ( e5) and preference for substrate with microphytes (16).

Lastly, at the left of the scatterplot, pairs of sites 9, 10, 12 and 7U, showed invertebrates mainly characterised by a body size ranging from 0.25 to 1 cm (a2, a3), < 1 generation per year (cl), respiration with plastrons (h3) and spiracles (h4), herbivorous food habits (k:4), and a preference for medium-high current velocities (>25 cms-1 ), eggs and statoblasts as resistance forms (gl), mainly flier organisms (il), preference for substrate ranging from flags to pebbles (11), habitats low input organic (nl, pl).

Discussion

Scientific studies and regional surveys of stream ecosystems o:ften provide large volumes of site-specifie data [START_REF] Bailey | Bioassessment of freshwater ecosystems using the reference condition approach[END_REF], from which local and regional spatial patterns of biological communities can be derived [START_REF] Hawkins | Development and use of predictive models for assessing the biological integrity of streams[END_REF]. Because of geographie differences in biotic and abiotic characteristics of streams, classification has become an integral part of efforts to study, monitor and manage stream ecosystems at watershed scale [START_REF] Omernik | Ecoregions of the contreminous United States. Map (scale 1 : 7,500,000[END_REF][START_REF] Tate | The ordination of benthic invertebrate communities in the South Platte River Basin in relation to environmental factors[END_REF][START_REF] Sandin | Ecoregions and benthic macroinvertebrate assemblages of Swedish streams[END_REF]. The identification of river sites with similar biological and environmental characteristics may help in selecting reference sites for impact assessments (i.e., fish farm), or to provide results to extrapolate at regionallevel [START_REF] Rohm | Evaluation of an aquatic ecoregion classification of streams in Arkansas[END_REF][START_REF] Finn | Variability and convergence in benthic communities along the longitudinal gradients of four physically similar Rocky Mountain streams[END_REF]. During the last decades, there have been many attempts to produce stream classifications based on features of aquatic communities [START_REF] Céréghino | Predicting the species richness of aquatic insects in streams using a limited number of environmental variables[END_REF]. Freshwater invertebrates were o:ften studied in this context, because understanding the patterns of geographie variation in the structure of benthic assemblages is of crucial importance to develop a comprehensive assessment of ecosystem conditions (BAILEY et al., 2003).

Our multivariate analyses (PCA and CA) described the upstream to downstream gradient of physical characteristics of streams from headwaters to plain, and the resulting community responses. Despite the presence of fish farms in the study stream systems, and regardless to the size of the facilities, the amount of water treated and the impacts upon the physical and chemical environment (in particular, a general increasing of organic matter and decreasing of oxygen in the reaches downstream of the facilities ), our classification of sampling sites based on environmental variables portrayed the downstream gradients in typological conditions, from headwaters to plain areas. Within this framework, the spatial patterns of invertebrate assemblages in our study system fitted with ILLIES (1961) and ILLIES and BoTOSANEANU's well-known zonations [START_REF] Illies | Problèmes et méthodes de classification et de la zonation écologique des eaux courantes, considérées surtout du point de vue faunistique[END_REF] for western Europe. The gradient analysis we performed through a CA subsequently portrayed the graduai downstream changes in the taxonomie structure ( observed during the spring sampling) of invertebrate communities, with respect to the longitudinal gradient in stream characteristics. The distribution of invertebrate taxa commonly tends to partition streams into clear downstream sections, such as springs (or "eucrenon") to fluvial zones (or "potamon") at most downstream sections.

Therefore, even if trout farm locally impacted the structure of macroinvertebrate communities (downstream each trout farm, biological quality of waters (I.B.E.) pointed out a worsening trend (FABRIZI et al., 2005)), these seriai disturbances at the stream system scale did not affect the taxonomie composition of assemblages, suggesting that the benthic fauna recovered from one trout farm to the immediate downstream one.

Nevertheless, the organic load produced by trout farms in Valnerina contributes significantly to generate an elevated eutrophie level of the Piediluco Lake, which is a reservoir whose the Nera River is tributary through a derivation channel (F ABRIZI et al., 2007).

The extent of the observed faunal changes (F ABRIZI et al., 2005) depended both on the local habitat conditions ( downstream section) and on the technical characteristics of the facilities (size, fish production, water treatment), but community diversity was usually affected by the detriment of the pollution sensivite taxa, while pollution tolerant invertebrates increased in density (see also [START_REF] Selong | Impacts of trout culture eftluent on water quality and biotic communities in Virginia headwater streams[END_REF]).

Only a few biological traits, mostly related to body size and feeding habits, accounted for local disturbance. Fish farming primarily impacts the receiving streams through the input of suspended organic matters. The nutrient inputs corresponding to 30 tons of trout (ca. 1/80 of the annual production in Umbria) are equivalent to those from 93 persans for phosphorus, 263 persans for orthophosphates, and 1039 (ammonia)-16443 for nitrogen (nitrite+ nitrate) [START_REF] Tarazona | Pollution generated by fish farms. A systems dynamics model[END_REF]. These chemical alterations, combined with decreased oxygen concentrations, contribute to generate eutrophie environments. Taxa with large body size, which fed upon microorganisms and fine detritus, and which had asexual reproduction characterized the impacted downstream sites. Those populations are believed to be selected by unstable habitats or by habitats fluctuating in an unpredictable way, and probably ensured space occupancy by channelling much energy into multiplication. Conversely, upstream and least impact sites hosted small-sized invertebrates showing sexual reproduction, and feeding upon, plant material and/or algae. These traits suggest that habitat occupancy and the partitioning of food resource were favoured by small size and by a higher diversity of feeding groups at the least impacted sites. Those populations are believed to be selected by more predictable and structured habitat features allowing interspecific competition and/ or resource partitioning through the spatial segregations of species (BEGON et al., 1996). During the last decade, many studies have evaluated the relationships between freshwater species traits and environmental conditions (e.g., [START_REF] Statzner | Reproductive traits, habitat use and templet theory: a synthesis of world-wide data on aquatic insects[END_REF][START_REF] Townsend | Species traits in relation to temporal and spatial heterogeneity in streams: a test of habitat templet theory[END_REF]. These studies indirectly support the habitat templet concept of stream ecosystems, which relates trends in species traits to habitat variability (TOWNSEND and HILDREW, 1994) as a theoretical framework for assessing and predicting the functional organisation of stream communities (e.g., [START_REF] Schlosser | A conceptual framework for fish communities in small warmwater streams[END_REF][START_REF] Poff | Landscape filters and species traits: towards mechanistic understanding and prediction in stream ecology[END_REF]. From our study, it appeared that species traits did wellin revealing functional changes within communities subjected to disturbance (here trout farming), because species with certain traits were eliminated and/or replaced by others below the facilities. However, although disturbance was regularly repeated from headwaters to plain areas, there was no additive effect upon the species trait composition of the overall regional species pool. In fact, species traits showed seriai discontinuities according to changes in community structure.

Our ability to properly interpret patterns of variation of communities in the context of biomonitoring obviously depends on the spatial scale of observation, because patterns are produced by processes that act at multiple scales, often at scales different from those at which the patterns are observed [START_REF] Boyero | Multiscale patterns of spatial variation of stream macroinvertebrate communities[END_REF]. At the watershed scale, integrated surveys should certainly benefit from considering macroinvertebrate communities through biological and ecological attributes (rather than only in terms of species assemblage sensu stricto), because this is likely to fit with a broader approach since the resulting patterns are not expected to be region-specifie (OBERDORFF et al., 2002; STATZNER et al., 2004) and will implicitly consider adaptations to environmental characteristics, i.e., historical patterns. Conversely, any madel referring only to a region-specifie fauna (i.e., a species list) would be more prone to have local acceptance.

Figure 1 .

 1 Figure 1. Map of the study area and location of the 13 pairs of sampling sites, upstream (U) and downstream (D) of each trout farm.

  •••••"""'8ï)""""""""""" ............... .. . . . . • • • • o su ... F ~............. • .....................

  Figures 2. Principal Component Analysis (PCA) carried out on the 26 sites located upstream (U) and downstream (D) of each trout farm, and on 13 environmental parameters for each site. Sampling sites (a) and environmental parameters (b) are plotted on the fust two PCA axes. Clusters of sites (a) are derived from Ward's algorithm. TVS =Total Volatile Solids (see text).

Figure 3 .

 3 Figure 3. Correspondence analysis carried out on the taxa abundance matrix. (a) Ordination of the 26 sites on the first two CA axes (lU, lD, etc. are sites, U = upstream, D = Downstream of each trout farm); (b) distribution of the taxa in the study system.

Figure 4 .

 4 Figure 4. Co-Inertia analysis of taxa distributions and biological traits matrices (the first two CoA axes). (a) Ordination of the 26 sites, upstream (U) and downstream (D) of each trout farm; (b) distribution of species traits categories.Only structuring traits are illustrated, and the categories are positioned according to the weighted average of their species.

Table 1 .

 1 Main characteristics of trout farms in Umbria Region (Central Italy).

	Trout farm	Stream	Trout farm (flow L s-1 )	Trout species	Production (q yr-1)	Facility type
	(site)
	1	Nera	95	O. mykiss, S. trutta	130	trout hatcheries, trout force-fed
	2	Campiano	95	O. mykiss, S. trutta	1500	trout hatcheries
	3	Campiano	400	O. mykiss, S. trutta	1000	trout force-fed
	4	Campiano	1000	O. mykiss, S. trutta	2000	trout force-fed
	5	Sordo	200	O. mykiss	50	trout hatcheries
	6	Sordo	550	O. mykiss, S. trutta	30	small trout force-fed
	7	Como	3000	O. mykiss	12000	trout force-fed
	8	Vigi	222	O. mykiss	500	trout hatcheries, trout force-fed
	9	Nera	95	S. trutta	170	trout hatcheries, trout force-fed
	10	Nera	3000	O. mykiss, S. trutta	4500	trout force-fed
	11	Cas ana	350	O. mykiss, S. trutta	200	game fishing
	12	Nera	1100	O. mykiss, S. trutta	-*	trout hatcheries, trout force-fed
	13	Clitunno	600	O. mykiss	1400	trout force-fed
	Source: POSATI et al., 2002 (ARPA Umbria) modified
	* datum unknown (small facility)

Table 2 .

 2 Biological and ecological traits and modalities (=categories) of aquatic macroinvertebrates defined in this study.

	Traits	Modalities	Code
	Maximal potential size	>0.25-0.5 cm	a2
		>0.5-1 cm	a3
		>1-2 cm	a4
		>2-4cm	a5
		>4-8 cm	a6
		>8cm	a7
	Life cycle duration	:::::;1 year	bl
		>1 year	b2
	Potential number of cycles per year	<1	cl
		1	c2
		>1	c3
	Aquatic stages	egg	dl
		larva	d2
		nymph	d3
		adult	d4
	Reproduction	ovoviviparity	el
		isolated eggs, free	e2
		isolated eggs, cemented	e3
		clutches, cemented or fixed	e4
		clutches, free	e5
		clutches, in vegetation	e6
		clutches, terrestrial	e7
		asexual reproduction	e8
	Dispersal	aquatic passive	f1
		aquatic active	f2
		aerial passive	f3
		aerial active	f4
	Resistance forms	eggs, statoblasts	gl
		coco ons	g2
		housings against desiccation	g3
		diapause or dormancy	g4
		none	g5
	Respiration	tegument	hl
		gill	h2
		plastron	h3
		spiracle	h4
	Locomotion and substrate relation	flier	il
		surface swimmer	i2
		full water swimmer	i3
		crawler	i4
		burrower	i5
		interstitial	i6
		temporarily attached	i7
		permanently attached	i8
	Food	microorganisms	jl
		detritus(< 1 mm)	j2
		dead plant (2: 1 mm)	j3
		living microphytes	j4
		living macrophytes	j5
		dead animal (2: 1 mm)	j6
		living microinvertebrates	j7
		living macroinvertebrates	j8

  ........................................... ./ •••...... 2D 0 ................................. .

N 2 LL.

Table 3 .

 3 Benthic community (88 taxa) ofthe 26 sites sampled in a stream system ofCentralltaly impacted by 13 trout farms (1 upstream (U) and 1 downstream site (D) per facility).

		Taxa	1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12 13 13
			UDUDUDUDUDUDUDUDUD U DU DU DU D
	Nematoda	Mermithidae undet.
	Nematomorpha	Gordiidae undet.
	Turbellaria	Dendrocoelum sp.
		Dugesia sp.
		Polycelis sp.
	Gastropoda	Ancy/us fluviatilis
		Hydrobiidae undet.
		Lymnaea sp.
		Physa sp.
	Bi val via	Pisidium sp.
	Oligochaeta	Branchiura sowerbyi
		Eiseniella tetraedra
		Haplotaxis gordioides
		Lumbriculidae undet.
		Tubificidae (with capillary setae) undet.
		Tubificidae (without capillary setae) undet.
	Hirudinea	Dina lineata
		Glossiphonia sp.
		Haemopis sanguisuga
		Helobdella stagnalis
	Crustacea	Asellus aquaticus
		Echinogammarus sp.
	Ephemeroptera	Baetis sp.
		Caenis sp.
		Ecdyonurus sp.
		Epeorus sp.
		Ephemera sp.
		Serratella ignita
		Habroleptoides sp.
		Rhithrogena sp.
	Odonata	Calopteryx sp.

  •• ....................

				. ••
	-		su	80 070 ... )
	\ ...• 20 o ••••••••	40	0	.. lu: • u ............... / 30

Acknowledgements

We thank the two anonymous reviewers who provided valuable comments on an earlier version of this paper. This research has been financially supported by "Regione dell'Umbria".


Where is the Punk in Solarpunk? Questioning Tradition and Innovation in an

Eco-optimist Digital Aesthetic? Théo Maligeay -Etudes Montpelliéraines du monde anglophone Journée d'études: "From Cottagecore to solarpunk: new political and aesthetic readings of the pastoral" 17 November 2023

Although solarpunk is "still in its infancy" to quote a 2022 article by Alejandro Rivero-Vadillo, the term is becoming increasingly well-known, and might already be familiar to some of you. Part of the reason why the word, and various solarpunk works are getting traction is because of their controversial nature. One only has to scroll back to 11/11/23, less than a week ago, to find a recent example of this on Reddit's dedicated message board, a community of some 124 000 members. User u/Thatannoyingturtle writes: "This is just a mild pet peeve of mine. It's people [labelling] non-solar punk stuff as solar-punk. Just because it's happy and green, just because it's futuristic doesn't make it solar punk. I see a lot of people label cottage core as solar punk when it makes no use of futuristic or even modern technology. Or people labelling any futuristic setting that isn't cyberpunk and has like, 1 plant as solar punk. Solar punk is greenery, eco friendliness, and anti-consumerism in conjunction with technology." Despite its cantankerous tone, the comment offers a relevant entry point into solarpunk. Not only does it highlight the potentially controversial nature of the solarpunk denomination, it also identifies its most important thematic elements : the omnipresence of vegetation, caring about ecology, anti-capitalism and an optimistic tone ("Just because it's happy and green doesn't make it solar punk"). On a side note, you will surely have noticed that u/Thatannoyingturtle also compares solarpunk to cottagecore, which makes me think that we should really invite them next time Constance. In the comment section, the discussion kicks off with an ambivalent counterargument: "At [the] same time that I want to ridicule your definition by posting pictures of corporations investing heavily in ecological friendly spaces, like Apple, I also want to complain that too many posts here about gatekeeping instead of gardening." This prompts the original poster to disambiguate by stating the clear difference between his version of solarpunk and corporate greenwashing which he goes as far as calling "cosplaying" in reference to popular costuming practices. Later in the thread, multiple users emphasise the fluidity of solarpunk. Just after the previous exchange, u/afraidtobecrate writes "Solarpunk doesn't have a clear definition or aesthetic. Without that, people will just post stuff they think is related that looks cool." Lower down u/Menacebi confirms what we may already have begun to suspect : "People arguing about what is and isn't solarpunk is solarpunk", a comment which u/orthomans takes to its logical conclusion: "Rule 1 of solarpunk is nobody agrees on what solarpunk is." Thankfully however, some definitions are oecumenical enough to offer some frame of reference. First, the moderators of the Reddit solarpunk board give three different definitions in different sections of the website : "Solarpunk is a genre and aesthetic that envisions collective futures that are vibrant with life, as well as all the actions, policies, and technologies that make them real. We are interested in science fiction, social movements, engineering, style, and anything that inspires a future society that is just and in harmony with its ecology"; "Solarpunk is everything from a positive imagining of our collective futures to actually creating it"; and finally "What is Solarpunk? Solarpunk is an aesthetic and a literary genre that has grown out of existing social movements. Fundamentally, solarpunk is about imagining possible good futures and working to create them: just as the earth is made up of different biomes, there is not one definitive solarpunk future. A solarpunk future is one where we've leveraged technology to care for all humans, to restore and tend the ecosystems around us. Solarpunk also aims to undermine the systems currently in place that endanger the future we are working to create. Solarpunk is collectivist: it's about working together for the common good. Solarpunk is polyphonic: one cannot speak for other Solarpunks, only be in dialogue and in chorus with them. While Solarpunk seems utopic, it is grounded in reality and it is not without struggle. Solarpunk aesthetics change depending on how far you look in the future." It is followed by a list of "conflicting concepts": capitalism, ecofascism, greenwashing and anarcho-primitivism and finally, it catalogues 76 ways to get involved depending on your housing situation or the level of commitment you can afford. This definition seems reliable enough since it is invoked as an argument of authority in the thread that we read previously: "the sub [subReddit] literally explains that anarcho-primitivism ISN'T solarpunk". All three of these definitions bring to the fore major aspects of solarpunk, notably its optimism, and its dual, political-artistic nature.

On Reddit, one can also find a link to "Solarpunk: Notes towards a Manifesto", written by essayist Adam Flynn in 2014. The slogan: "We're solarpunks because the only other options are denial or despair." The political references: "Solarpunk draws on the ideal of Jeffersonian yeoman farmer, Gandhi's ideal of swadeshi and subsequent Salt March and countless other traditions of dissent (for what it's worth, both Gandhi and Jefferson were inventors". In the second part of this 600-odd-words long essay, Flynn delineates the core visual influences of solarpunk: "The visual aesthetics of Solarpunk are open and evolving. As it stands, it's a mash-up of the following: -1800s age-of-sail/frontier living (but with more bicycles) -Creative reuse of existing infrastructure (sometimes post-apocalyptic, sometimes present-weird) -Jugaad-style innovation from the developing world -High-tech backends with simple, elegant outputs. Obviously, the further you get into the future, the more ambitious you can get. In the long-term, solarpunk takes the images we've been fed by bright-green blogs and draws them out further, longer, and deeper. Imagine permaculturists thinking in cathedral time. Consider terraced irrigation systems that also act as fluidic computers. Contemplate the life of a Department of Reclamation officer managing a sparsely populated American southwest given over to solar collection and pump storage. Imagine "smart cities" being junked in favor of smart citizenry." A few lines later, he mentions the work of Japanese director and founder of Ghibli Studio Hayao Miyazaki.

Before we dive into some of the critical issues that surface from the works of Flynn and others about solarpunk, I would like to finish this description with a few examples of solarpunk works in art and in the world. First, the Beluga Skysail, a hybrid cargo ship which uses sail power to supplement the ship's engines. It made its maiden voyage in March 2008 making a two-month trip from Germany to Venezuela, the US and Norway, and achieving 20% fuel savings over the course of the trip thanks to the motive power provided by the sail. It was the Beluga Skysail that led the author of the blog "Republic of the Bees" to write the post "From Steampunk to Solarpunk" in May 2008, the earliest known use of the term. In literature, solarpunk thrives in the short story form with collections such as Glass and Gardens: Solarpunk Summers and its sequel Glass and Gardens: Solarpunk Winters edited by New Mexican author Sarena Ulibarri. In the former, Julia K. Patt's "Caught Root" tells the story of a diplomatic encounter between the technophile city of Hillside and the less-industrailised municipality of New-Ur. In the words of Alejandro Rivero-Vadillo "On the one hand, Hillside is depicted as the archetypical technophilic Solarpunk city, with "shining towers [that] reach for the blue sky", building materials that are"recycled, unblemished, new looking", and with heavily automated solar-powered technology and a climate-controlled atmosphere . On the other hand, New-Ur "seems born from the very rock, all adobe and stucco and low-sitting buildings". Everything in the city is built from "reclaimed and reused materials", and even vital infrastructure, such as water purification systems, are made from sustainable materials such as "porous clay". Another story "A Field of Sapphires and Sunshine" by Jaymee Goh recalls the original solarpunk cargo ship as it recounts a young woman's crossing of the Pacific onboard a solar-powered vessel. Finally, "Watch Out Red Crusher!" by Shel Graves addresses the issue of emotional sustainability by depicting a world where nanotechnologies allow humans to change their skin colour to match their emotions. As a fictional setting, solarpunk can easily combine with other fictional genres, as shown by various solarpunk mystery narratives: "Grover: Case #C09920, 'The Most Dangerous Blend'" by Edward Edmonds or the upcoming Murder in the Tool Library by A.E. Marling. In parallel to its development in literature, solarpunk's influence on the visual arts is also growing. Artists such as Rita Fei, illustrator of both the covers of Murder in the Tool Library and Multispecies Cities, Solarpunk Urban Futures have made a style out of solarpunk by developing a visual language fitting its themes and ideas. On the other hand, searching for solarpunk images on Google will lead to a plethoric collection of images, only growing larger as the production and dissemination of images generated by artificial intelligence programs become more prevalent. I would like now to focus on solarpunk's relationship with punk itself, the musical and aesthetic genre invented and popularised by British and American bands such as The Sex Pistols, The Ramones and The Clash. The punk in solarpunk derives from steampunk another subgenre of speculative fiction from which the author of "The Republic of the Bees" explicitly drew his inspiration: "I think the best way to explain solarpunk is by contrasting it to the science fiction and fantasy genre called steampunk, from which the idea of solarpunk derives. Steampunk stories describe alternative futures or worlds in which steam technology (and Victorian technologies in general) were not pushed aside by oil-based technologies." Steampunk itself derives its name from cyberpunk, the original -punk subgenre of science-fiction. Best exemplified by William Gibson's 1984 Neuromancer novel and the two subsequent volumes of the Sprawl trilogy, cyberpunk's origins can also be traced back to Philip K. Dick's Do Androids Dream of Electric Sheeps and its adaptation in film, Blade Runner. Prominent motifs include cybernetic implants, neon architecture, surveillance and Japanese or Far Eastern influences. The most widely accepted definition of dash-punk denominations is that they take the technological and cultural paradigm of one era and stretch it to its limits. For example, the Victorian period for steampunk. Energy sources are particularly important in that perspective. In both solarpunk and steampunk, the steam engine or renewables are central to both aesthetics as they drive the technologies that make them unique. This is also true of other more minor -punk subgenres such as dieselpunk (think Mad Max) or atompunk. As far as that definition offers a fairly solid understanding of emerging fictional practices, the dizzying multiplication of -punk subgenres and the weird concatenations that they produce can sometimes go beyond the reasonable, as shown by Giscardpunk, the creation of French artist Florent Deloison, which I cannot believe is completely serious, especially since it has begun its own digital interactive existence.

Solarpunk however stands out from all the other punk subgenres because it is more grounded in political criticism and activism. In the words of "The Republic of the Bees": "Obviously, a major difference between solarpunk and steampunk is that solarpunk ideas, and solarpunk technologies, need not remain imaginary, and I indulge a hope of someday living in a solarpunk world. [...] I find it very unlikely that a transition to renewable energy can be accomplished without serious political fights." Here we find once again the importance of hope which ultimately appears as important as renewable energies and sustainable agriculture in defining solarpunk and differentiating it from other -punk subgenres. If we go back to Flynn's "Notes towards a [solarpunk] manifesto" the same idea is emphasised: "Solarpunk is about finding ways to make life more wonderful for us right now, and more importantly for the generations that follow us [...]. Our futurism is not nihilistic like cyberpunk and it avoids steampunk's potentially quasi-reactionary tendencies" Solarpunk's resolute optimism eventually leads to a more complete understanding of the prefix solar-contained in its name. Indeed, in solarpunk the sun is not only present as a source of physical energy, but also as a provider of spiritual and emotional energy in the context of growing climate anxiety. A symbol of hope and life and an affirmation of completeness.

However, this puts it strongly at odds with the original tenets of punk as expressed and practised by impoverished youth in Britain and the United States during the 1970s, and this issue regularly surfaces in solarpunk discussions. For example, immediately after the paragraph extolling optimism as a central component of solarpunk, Adam Flynn defends his position and solarpunk in general against potential criticism: "And yes, there's a -punk there, and not just because it's become a trendy suffix. There's an oppositional quality to solarpunk, but it's an opposition that begins with infrastructure as a form of resistance. We're already seeing it in the struggles of public utilities to deal with the explosion in rooftop solar. "Dealing with infrastructure is a protection against being robbed of one's self-determination," said Chokwe Lumumba, the late mayor of Jackson, MS, and he was right." Similarly, in the comments below u/Thatannoyingturtle's post we find this interesting exchange between u/jjSuper1 : "I think my major misunderstanding with the genre is all the political nonsense. I focus on the tech. However, just about every magazine, pdf, website, video, blog, podcast, and media out there seems to focus on the political aspect because apparently there wasn't a place to discuss the implications of politics." and u/ArmorClassHero: "In order for something to be -punk it has to be axiomatically anti-capitalist and therefore political. What did you think the -punk meant?" The main accusation levelled against solarpunk is that it is too mild, not rebellious enough to be worthy of the punk moniker. Both u/ArmorClassHero and Adam Flynn's silent critics find fault in solarpunk because it is too much an artistic trend and not enough a political movement. This is a very puzzling argument given that punk was born in the music of British rock bands and that the most iconic punk band of the Seventies were the Sex Pistols whose formation was mostly the result of manager Malcolm Mac Laren's commercial strategies: punk was not, originally, a pristine cultural revolution. Nevertheless, although it succeeds in defending solarpunk as a worthy political resistance, Adam Flynn's counter argument does not address another deep-seated opposition between punk and solarpunk. Whereas In conclusion, I would like to point out that although solarpunk can only ever be imperfectly punk, because of that fundamental divergence between optimism and nihilism as their chosen answer to the social challenges they face, one should also bear in mind that solarpunk projects often display very distinctly punk characteristics. The importance of do-it-yourself for example is a major common point between the struggling concert goers of 1970s North London and the practitioners of off-the-grid permaculture nowadays around the world. Furthermore, although solarpunk has been known to sell-out, putting its radical style and ideas at the service of the establishment in pursuit of monetary clout or gain, the solarpunk community has also been able to mobilise and respond to this encroachment of commercial interests on the aesthetic in particularly punk-like fashion. For example in the case of the "Dear Alice" commercial for Chobani yoghurt, the video has been reposted on Youtube without the branding that was present in the original. This anonymous act of cultural guerilla, erasing the stigmatas of corporate greed from the face of our collective dreams point towards an interesting similarity between punk and solarpunk: both manifest over all the struggle for retaining one's autonomy and voice in the context of vastly disadvantageous social configurations.

Works Cited:

Blade Runner, 1982. Chabria, Priya Sarukkai, Taiyo Fujii, et Shweta Taneja. Multispecies

  the latter is optimistic by definition, amplifying the trends of previous British popular culture movements such as the Mods or the Teddies extensively studied by Stuart Hall and the Center for Contemporary Cultural Studies, punk artists promoted nihilistic attitudes. One only has to listen to the shouting outro of the Sex Pistols' controversial "God Save the Queen": "No future No future No future for you No future No future No future for me No future No future No future for you No future No future for you". Nothing could be more antithetic to solarpunk's core values.

  Cities: Solarpunk Urban Futures. World Weaver Press, 2021. Dear Alice, 2021. https://www.youtube.com/watch?v=z-Ng5ZvrDm4. « Dear Alice » Decommodified Edition | Solarpunk anime ambience with no ads, 2021. https://www.youtube.com/watch?v=UqJJktxCY9U. Dick, Philip K. Do Androids Dream of Electric Sheep? Doubleday, 1968. Flynn, Adam. « Solarpunk: Notes towards a manifesto ». Project Hieroglyph (blog), 4 septembre 2014. Gibson, William. Neuromancer. Ace, 1984. Republic of the Bees. « From Steampunk to Solarpunk », 27 mai 2008. Rivero-Vadillo, Alejandro. « Challenging Solarpunk s Technophilia through Degrowth Imaginaries in Julia K. Patt s "Caught Root" and Linda Jordan s "Reclaiming" ». Ecocene: Cappadocia Journal of Environmental Humanities, ://doi.org/10.46863/ecocene.64. The Sex Pistols. « God Save the Queen ». In Never Mind the Bollocks, Here's the Sex Pistols. Virgin Records, 1977. Ulibarri, Sarena, éd. Glass and Gardens: Solarpunk Summers. Albuquerque: World Weaver Press, 2018. ---, éd. Glass and Gardens: Solarpunk Winters. World Weaver Press, 2020.

	Cappadocia	University	3,	n o	1	(20	juin	2022):	41-55.

https


domain: chim chim.mate spi

text:
Anthony Ferri

François Rault
email: francois.rault@ensait.fr

Antonio Da Costa

Cédric Cochrane

Matthieu Boudriaux

Guillaume Lemort

Christine Campagne

Eric Devaux

Christian Courtois

Rachel Desfeux

Local Electrical Characterization of PVDF Textile Filament

Keywords: Poly(vinylidene fluoride) PVDF, melt-spun textile fiber, piezoelectric effect, piezo-force microscopy

la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Over the last decade, textile instrumentation has attracted the attention of several researchers [START_REF] Koncar | Smart Textiles and their Applications[END_REF]. Firstly confined to specific technical areas and dedicated to well-defined users (e.g. tracking for military [START_REF] Scataglini | Proc. 2015 Work Wearable Syst. Appl. Italy[END_REF][START_REF] Nayak | Electronic textiles: Smart Fabrics and Wearable Technology[END_REF], sensors for firefighters [START_REF] Soukup | Proc. of the 5th Electronics System-integration Technology Conference (ESTC) Finland[END_REF][START_REF] Mandal | [END_REF], etc.), this topic increasingly integrates mass-market applications due to the emergence of connected, e-textile or so-called "smart textiles" in various areas such home textiles [START_REF] Brauner | Proc. of the 2017 ACM International Conference on Interactive Surfaces and Spaces United Kingdom[END_REF], fashion [START_REF] Berzowska | [END_REF], sport [START_REF] Zhou | Proc. 2017 IEEE International Conference on Pervasive Computing and Communications Workshops (PerCom Workshops)[END_REF][START_REF] Tama | Proc. XIV Int. Izmir Text. Appar. Symp. Turkey[END_REF], health [START_REF] Pantelopoulos | [END_REF]11], etc. A better integration of "intelligent functions" in textile structures is particularly relevant in the latter sectors, where monitoring of body parameters is of particular interest. Due to the multiplication of sensors, process unit and communicative system, the need of energy and data of sector is substantial. One of the possible solutions is energy harvesting by textile structure itself [11,12]. Some solutions based on the conversion of energy (thermal, mechanical, etc.) to electric voltage are nowadays investigated in laboratories.

Piezoelectric materials show reversible relationships between electric charge and mechanical deformation called converse and direct piezoelectric effect [13]. The latter leading to an electric charge generation during mechanical stress can be used in a wide variety of applications from neural stimulation [14,15], sensors development [16,17] or energy harvesters [13,17]. As a consequence, such materials and more particularly piezoelectric polymers are perfect candidates to solve the main problem for etextiles, i.e.: develop self-sustaining energy sensors. Among the piezoelectric polymers available, fluoropolymers such as poly(vinylidene fluoride) (PVDF) and its copolymers show the better piezoelectric behavior [18]. Although copolymers crystallize in polar form suitable for piezoelectric properties, PVDF is still preferred due to its relative low cost. Nevertheless, depending on the processing conditions it can crystallize in five different structures: α, δ, ε, γ, β [19]. The β phase is the most polar phase [20].

Accordingly, this one is targeted to convert mechanical deformation into electric energy. The development of PVDF textile energy harvesters requires solving many scientific issues such as the generation of the β phase in the fibers but also its evaluation as well as its electromechanical activity.

On one hand, various methods exist to determine the presence of β phase into PVDF. Usually this polar crystalline form is characterized by one or more thermal analysis techniques [21] (differential scanning calorimetry (DSC), modulated DSC [22], dynamic mechanical analysis (DMA) or thermal mechanical analysis (TMA)) as well as X-ray diffraction (XRD) and spectroscopy measurements (FTIR, Raman, NMR) [23]. Depending on the test used, it is easily to evaluate qualitatively and quantitatively the presence of β phase in PVDF fiber. DSC is a fast and controlled characterization method on fiber. However, as in thermal analysis techniques, melting and recrystallization phenomena during the test may disrupt the analysis of the results. Other limitations for easy characterization such as the size, the form and the morphology of produced fibers have to be taken into account in some other tests. Thus, it is often necessary to design special specimen holder for filaments and to consider the orientation of sample during the test [24]. To correlate mechanical stretching and β phase, characterizations can advantageously be made in situ by Xray [25] or spectroscopy measurements [START_REF] Riosbaas | Proc. SPIE 9061, Sensors and Smart Structures Technologies for Civil[END_REF]. Nevertheless, to our knowledge only few studies are made in line with real process conditions [START_REF] Veitmann | 1 st workshop Innovative and Avanced Processing for Polymer[END_REF]. Even if FTIR experiment is easiest ex-situ spectroscopy technique available, the presence of relatively close characteristic peaks requires carefully conclusions and to correlate the results with other tests [START_REF] Khajavi | Abbasipour in "Industrial Applications for Intelligent Polymers and Coatings[END_REF]. Furthermore, this technical analysis presents some limitations for specific multilayer materials.

On the other hand, characterization of piezoelectric behavior is essential to improve the design of textile energy harvester and to understand all important phenomena occurring during the processing of PVDF fiber. Numerous varied experimental methods based on direct or converse effect exist to determine piezoelectricity efficiency [START_REF] Magniez | [END_REF]. Among all these techniques Berlincourt type piezometer is a useful solution for measuring piezoelectric coefficient on films. On textile fabric however, because of its small deformations, this test only allows soliciting the structure and do not give the piezoelectric response of the fiber. The evaluation of piezoelectric behavior of the textile can be made by output voltage measurements under large deformation using DMA for instance [30]. However, processing such structures is time and material consuming and gives only an average value at the fabric scale. Textile structures can be considered as a multi-scale material and a characterization of the piezoelectric behavior at each scale is relevant. Currently, there is no standardized test at the fiber scale for the measurement of piezoelectric coefficients and for the correlation with the β phase. Piezoelectric force microscopy (PFM) characterization is a relevant technical analysis to locally determine the presence of polar phase in the fiber and to evaluate its piezoelectric coefficient [31,32]. PFM analyses have been carried out on materials at the dedicated measuring scale of the apparatus, i.e. on nanofibers [33][34][35][36]. To our knowledge, only one study has been published on the characterization of a textile filament [37]. However, this monofilament with a diameter around 150 μm is not totally representative of the classical diameters used in textile applications. Indeed, in the work described by Soin et al. such large monofilament has been chosen to confer rigidity to the spacer fabric produced [37]. The textile fibers used in the yarns have conventionally diameters of less than 100 μm and consequently a lack of knowledge on electromechanical behavior for such 30 µm diameter fiber is underlined. Thus, the aim of this study is to leverage of PFM analysis for the development of micro-scale PVDF textile fiber by locally probing the physical properties. These first experimental trials on such fibers are particularly interesting. Indeed, they can have important implications for many researchers working on the development of multicomponent piezoelectric fiber systems for energy harvesting where conventional analyses could not be sufficient.

EXPERIMENTAL Materials

Commercial grade of PVDF was obtained by Solvay (PVDF Solef 1006, Solvay, Belgium). The average melt flow index (MFI) is 40 g/10 min (load of 2.16 kg at 230 °C) and the density is 1780 kg.m -3 in the solid state.

Before melt spinning, PVDF is dried in oven for 24 h.

Sample preparation

Multifilament yarns were produced using a spinning device Spinboy 1 from Busschaert Engineering. Four successive temperature of the spinning screw extruder are 80, 190, 200, and 210 °C. A volumetric pump ensured the injection of the molten polymer into two parallel dies each containing 40 holes (diameter of 400 mm) with a flow rate of 35 cm 3 .min -1 in order to obtain a continuous multifilament yarn which was cooled down by air and coated with a surfactant. Finally, the multifilament yarn was hot drawn between two series of rolls. The ratio between rotation speed of the second roll (R2) and the first roll (R1) is called Draw Ratio (DR). Previous study has shown that different DR can be obtained up to a DR of 3 (R1: 150 m.min -1 and R2: 450 m.m -1 ) leading to β-phase higher than 50 %. Due to future works and in particular that the development of multicomponent fibers having layers with different behavior under drawing (use of various polymers with or without fillers), a relatively low DR has been chosen for this study. [38] In addition, this low DR seems to be an appropriate strategy to highlight the powerfull of the PFM tool to detect piezo-activity in such textile fiber with relatively low polar phase content.

Characterization

FTIR

A Thermo Scientific FTIR ATR Nicolet Spectrometer was used for recording the infrared spectra of as-spun (DR = 0) and drawn (DR = 1.5) fibers of PVDF. To perform the tests, fibers are lined up on a ZnSe substrat and analyzed in reflection mode. The samples were scanned eight times in the range of 600 to 1500 cm -1 .

XRD

XRD measurements were carried out using a PANalytical diffractometer with Bragg-Brentano geometry.

The radiation source was Cu Kα with a wavelength of 1.5418 Å. The scan rate was set at 1 second per step of 0.028 (2h).

AFM/PFM

Local characterizations were carried out under environmental conditions with a MFP-3D atomic force microscope from Asylum Research (USA). Surface morphology was characterized in AC mode, while PFM analyses were performed with Pt/Ir conductive tip coating (Nanosensors PPP-EFM probes, k ~2.8 N/m) and ground conductive substrates [39,40]. Dual AC resonance tracking (DART) PFM was employed to enhance the piezoelectric signal [41]. The PFM probe was calibrated by using the GetReal procedure from Asylum Research, where both inverse optical lever sensitivity (InvOLS) and spring constant of the cantilever are calibrated in one step without touch the surface, then we probed our reference sample (Pb(Mg1/3Nb2/3)O3-PbTiO3 thin film) with known d33 piezoelectric coefficient.

RESULTS AND DISCUSSION

Charaterization of polar phase by FTIR and XRD

Absorbance spectra recorded during FTIR experiments for PVDF as-spun fiber (DR = 0) and fiber drawn with a ratio of 1.5 and XRD diffraction patterns of the same fibers are shown in figure 1. In the FTIR spectra, the characteristic peaks of the α phase of PVDF at wavenumbers 760, 795, 855 and 976 cm -1 can be observed for all both fibers. It can be seen from the spectra that drawn fiber (DR = 1.5) has distinct shoulder and peaks at wavenumbers 1234 and 1279 as well as 840 cm -1 . The shoulder suggests the presence of γ-phase while the peaks represent β-phase of PVDF or more generally the polar phase (β/ γ) for this at 840 cm -1 [42]. All these results are in agreement with previously reported studies on influence of drawing during the spinning process of PVDF. Stresses applied during the fiber production can transform the α-phase of PVDF into β and/or γ polar phases [22,38]. Usually XRD patterns are used to confirm the results obtained from FTIR tests. However, in the diffractogram of both fibers (drawn and undrawn) no characteristic diffraction peaks of β (peak at 20.7°) and γ phases are present. The first peaks at 2θ = 17.9° and 2θ = 18.4° corresponds respectively to the (100) and (020) diffraction planes while the last peak at 2θ = 20.1° is linked to the (110) plane. These two conventional analysis techniques show some of their limitations such as a lack of sensitivity and an average analysis of the considered systems. In these cases, the use of specific tools to perform local analyzes can be very relevant.

[Fig. 1 about here]

Charaterization of piezoresponse

For PFM measurements, fibers were directly deposited on conductive disk with carbon paste in-between and the nano-probe tip was scanning individual fiber, as illustrated on figure 2a. Optical image of an individual fiber with 35 µm in diameter is shown on figure 2b, while the characteristic morphology of the fiber is presented in figure 3a, as measured by AFM. No preferential direction is observed for such low draw ratio (DR = 1.5). The nanoscale tip was used as movable top electrode at the surface of the fiber in order to locally probe both the electromechanical activity and the ferroelectric polarization. The out-of-plane PFM amplitude image shown in figure 3b displays contrasts corresponding to the local deformation of the fiber under electric field. Correspondingly, a strong contrasted out-of-plane PFM phase image is obtained suggesting several orientations for the polarization within the fiber, as seen on figure 3c. The obtained domains present sub-micrometer sizes, which could be correlated by the relatively low content of the β-phase resulting in small crystallites size. Black and white regions can be attributed to the out-ofplane component of the "upward" and "downward" polarization states, respectively, as related to the negative piezoelectric coefficient of the PVDF polymer. The various contrasts observed on both amplitude and phase PFM images reveal randomly oriented as-grown domains, which can be explained by the nonpreferential orientation for polymer chains and crystals in the fiber at low draw ratio [43] correlated by the absence of preferential direction on AFM image. Besides, there is no correspondence between the topographic image (figure 3a) and the PFM signals, indicating that the nature of the contrasted regions is related to the intrinsic electromechanical activity of the fiber and not to the cross-talk with the topography (see figure 3d), to the electrostatic effect or to surface reactions. Therefore, these as-grown domain patterns clearly evidence the local piezo-/ferroelectricity into the fiber, demonstrating the existence of the polar crystalline phase. Besides, it is worth noting that the apparition of electro-active zones is for unpoled polymer fibers, as already observed in such PVDF-based fibers [33][34][35].

[Fig. 2 about here] [Fig. 3 about here] Switching behavior and vibration amplitude were then probed by recording phase and amplitude piezoresponse hysteresis loops, respectively. DC bias voltage applied to the fixed probing tip was swept between ±40 V, i.e. high voltage PFM module was used to switch the polarization since the bulk coercive field of PVDF is known to be large (50 MV/m) [44]. Remnant signal (off-field mode) was measured in order to eliminate electrostatic effect for the benefit of the electromechanical contribution [45,46]. The figure 4 exhibits the piezoloops recorded over the free surface of the fiber. A square hysteretic behavior and two stable states of opposite polarization are observed on the phase loop pointing out the ferroelectric nature of the PVDF fiber. Indeed, a near 180° switching is observed for the domain phase under the DC bias voltage (the slight lower phase shift can be due to a small remaining electrostatic contribution). On the same figure is displayed the amplitude loop simultaneously measured showing a typical butterfly-shaped due to the inverse piezoelectric effect with clear saturation for higher applied voltages. These local PFM spectroscopic measurements reinforce the presence of the polar phase which presents ferro-and piezoelectric properties. As a remark, we note a slight asymmetry in switching process, as indicated by the shift of the piezoloops toward negative voltage values. This asymmetry is characteristic of an imprint behavior and point out the existence of an internal built-in electric field in the fiber [47,48]. The main reason is probably our strong asymmetric configuration, for which the top and bottom electrodes are constituted of Pt-Ir nanometric probe and conductive disk covered with carbon paste respectively, leading to different boundary conditions. We can also note that the shape of the amplitude loop is slightly asymmetric. This asymmetric shape can be also explained by the difference between the work functions of the tip and the bottom electrode, resulting in an internal bias field [49]. From the phase PFM loop, we determine a coercive voltage of 15 V. Considering the fiber diameter of 35 µm, we estimate a coercive field of 430 kV/m. This value is much lower than 50 MV/m in the case of bulk PVDF mentioned above. The difference can be explained by the micrometric size of our fiber which enables to decrease the voltage required to switch the polarization. Indeed, for such electroactive polymers with relatively high coercive field, a possible way to decrease the switching voltage is to synthesize these compounds as thin film form [START_REF] Venimadhav | Advances in Polymer Materials and Technology[END_REF].

In addition, the nanometric size for ferroelectric domains seen on the figure 3c can disturb the cooperative coupling among these domains, leading to a decrease of the spontaneous polarization and thus to a reduction of the coercive voltage [START_REF] Yang | [END_REF]. Also, such small ferroelectric domains are more efficiently switched by external electrical bias, leading to narrow hysteresis loops. On the other hand, we have to keep in mind that the physical processes considered for measuring the coercive field are different when using a movable tip at the nanoscale level and planar electrodes at the macroscopic scale. From the amplitude loop, the higher deformation at the maximum bias voltage is about 600 pm, but it is enhanced by the resonance (DART PFM method). In addition, for such polymer material, the loss is considered as pretty high, which leads to a low quality factor Q of around 10 [52-54]. Considering the amplitude A detected by PFM is proportional to A = d33VacQ, [52,53] and the driving voltage used for the piezoloops measurements was Vac = 5 V, we can estimate the effective piezoelectric coefficient as d33 = 12 pm/V (absolute value). This value is lower than others reported for PVDF-based fibers and determined by similar PFM analyses. Indeed, d33 coefficient of 30 pm/V was measured for β-phase PVDF fiber, which reaches 35 and 54 pm/V when added by carboxyl functionalized multiwall carbon nanotubes (CNTs) and silver decorated CNTs respectively [55]. M. Kanik et al. obtained an effective piezoelectric constant of 58.5 pm/V for γ-PVDF nanoribbons [36] while d33 of 45-50 pm/V was determined for BaTiO3/β-PVDF composite fibers [34].

However, for all these studies, the PVDF-based fibers are in the nanometric size range, which can reasonably explain the higher d33, as compared to the microscopic size of our fibers. It is known that nanoscale confinement induces very high piezoelectric response, mainly due to the larger contribution of the domain wall motion in such nanofibers [36,[56][57][58][59][60]. In addition, the β-phase content in our fibers fabricated at DR = 1.5 is not optimized (the β-phase is estimated around 15%) compared to higher DR [38] limiting the piezo-active volume probed by the AFM tip and leading to lower electromechanical activity. However, beyond this value of 12 pm/V, the PFM technique was shown to be suitable to demonstrate the electromechanical response in such individual micrometer-scale PVDF textile filament, evidencing the existence of β and γ polar phases, which is essential in view of fabrication of complex multicomponent fibers.

[Fig. 4 about here]

CONCLUSIONS

As-spun (DR = 0) and drawn (DR = 1.5) fibers of PVDF have been produced by melt spinning process and characterized during FTIR, XRD and PFM experiments. FTIR spectra revealed small intensity peaks than can be attributed to the polar phase of PVDF for samples having a draw ratio at 1.5. Nevertheless, the presence of such crystalline form could not be confirmed by XRD. It seems that the transformation of α into β phase during the spinning process is too low to present a sensitive signal. The feasibility and the interest of PFM analysis on such fiber was investigated as a first step of the development of more complex piezoelectric fiber, i.e: multicomponent fiber with concentric layers of different polymers around the PVDF. Different problems such as adhesion between the components will limit the drawability of final fiber and the possible conversion of crystalline phases of PVDF. Thus, it is supposed to obtain weak responses of the piezoelectric behavior of PVDF with conventional analyses. In this context, PFM can be relevant for future development of piezoelectric PVDF textile filament. In this work, PFM analyses have revealed phase and amplitude PFM contrasts for pristine regions over the surface of the fiber without correlation with the associated AFM morphology, which are related to the polar β-phase of the PVDF.

From piezoresponse loops, local effective piezoelectric constant of about 12 pm/V was determined, evidencing the electromechanical behavior of the individual fiber at the local scale. These performances are required for considering such micro-scale functional fibers in textile applications.

Figure 1 .

 1 Figure 1. FTIR (bottom) and XRD patterns (up) of as-spun fiber (DR = 0) and fiber drawn with ratio of 1.5.

20

 20

Figure 2 .Figure 3 .

 23 Figure 2. (a) Experimental setup for probing the local electromechanical response of single PVDF fiber (DR

Figure 4 .

 4 Figure 4. Piezoresponse phase and amplitude loops measured on the PVDF fiber (DR = 1.5).

ACKNOWLEDGEMENTS

This work is carried out under the regional program "Projets Emergents" and in the framework of the project entitled "Development of tricomponent piezoelectric polymer fibers for energy harvesting textiles". The authors thank the Region Nord-Pas-de-Calais (France) for its financial support, and also gratefully acknowledge Solvay for the supply of PVDF. The "Région Hauts-de-France" and the "Fonds