Heidrun Feuchtmayr
email: feuchtmayr@ceh.ac.uk

Brian Moss

Ian Harvey

Rebecca Moran

Keith Hatton

Les Connor

David Atkinson

Differential effects of warming and nutrient loading on the timing and 2 size of the spring zooplankton peak -an experimental approach with 3 hypertrophic freshwater mesocosms 4 5

Keywords: temperature, Global climate change, Daphnia, plankton, nitrogen, phosphorus, phenology Global climate change, temperature, Daphnia, plankton, nitrogen, phosphorus, 21 phenology 22 23

Differential effects of warming and nutrient loading on the timing and size

Introduction 1 2 Climate change is predicted to have huge impacts on the Earth's ecosystems through temperature 3 increase, changed patterns of precipitation, more frequent extreme weather events, and 4 combinations of these [START_REF] Ipcc | Summary for Policymakers[END_REF]. In temperate regions, temperature is predicted to increase 3 to 5 5°C within the next century. Freshwater lake communities will probably be affected both by 6 temperature and changing hydrology. 7 8 Shallow lakes and ponds are likely to be particularly susceptible to climate change (Mooij et al., 9 2005), as they have a high surface area compared with their volume and thus are very vulnerable to 10 temperature increase. Previous research has shown that warming could exacerbate the impact of 11 eutrophication and that the resulting population and ecosystem changes can include loss of fish due 12 to oxygen starvation [START_REF] Feuchtmayr | Global warming and eutrophication: effects on water chemistry and autotrophic 8 communities in experimental hypertrophic shallow lake mesocosms[END_REF][START_REF] Mckee | Response of freshwater microcosm communities to 45 nutrients, fish, and elevated temperature during winter and summer[END_REF][START_REF] Mooij | The impact of climate change on lakes in the Netherlands: a review[END_REF]Mooij et al., 13 2007; [START_REF] Moran | 6 Influence of simulated climate change and eutrophication on three-spined stickleback 7 populations: a large scale mesocosm experiment[END_REF]. Temperature increase has also been shown to favour the growth of toxic 14 cyanobacteria in some eutrophic lakes, which may lead to problems for a range of organisms, 15 including humans [START_REF] Johnk | 34 Summer heatwaves promote blooms of harmful cyanobacteria[END_REF]. 16 17 Long-term datasets, sediment records, process-based modelling and space-for-time-substitutions 18 along latitudinal or other climatic gradients suggest earlier phytoplankton spring population [START_REF] Rose | Does low temperature constrain the growth rates of 20 heterotrophic protists? Evidence and implications for algal blooms in cold waters[END_REF] increases with increasing temperature. Examples are: Müggelsee [START_REF] Gerten | Climate-driven changes in spring plankton dynamics and the 11 sensitivity of shallow polymictic lakes to the North Atlantic Oscillation[END_REF], Loch 20 Leven [START_REF] Carvalho | Changes in shallow lake functioning: response to climate change 37 and nutrient reduction[END_REF], three large Swedish Lakes [START_REF] Weyhenmeyer | Warmer winters: Are planktonic algal populations in Sweden's largest 45 lakes affected?[END_REF], Lake Erken 21 [START_REF] Weyhenmeyer | Changes of the plankton spring 47 outburst related to the North Atlantic Oscillation[END_REF], Bassenthwaite Lake [START_REF] Elliott | Testing the sensitivity of phytoplankton 1 communities to changes in water temperature and nutrient load, in a temperate lake[END_REF], Plußsee (Müller-Navarra et 22 al., 1997), Lake Washington [START_REF] Winder | Climatic effects on the phenology of lake processes[END_REF], Windermere [START_REF] Thackeray | Long-term change in the phenology of 34 spring phytoplankton: species-specific responses to nutrient enrichment and climatic change[END_REF]) [START_REF] Allen | Linking the global carbon cycle to individual 24 metabolism[END_REF] and Lake Constance [START_REF] Peeters | Earlier onset of the spring 15 phytoplankton bloom in lakes of the temperate zone in a warmer climate[END_REF]. For the deeper of these lakes, however, secondary 24 hydrodynamic factors, stratification periods and mixing depths, can play a major role in seasonal 25 phytoplankton development [START_REF] Diehl | Phytoplankton, light, and nutrients in a 39 gradient of mixing depths: Field experiments[END_REF]. Shallow lakes avoid these complications. 26 27 Further evidence of the influence of climate warming on freshwater systems can be found for 28 zooplankton, a major component of freshwater food-webs, which influences water quality by 29 consuming algae and providing food for fish. Zooplankters, mostly Daphnia spp., generally become 30 very abundant in spring in temperate lakes following peaks in algal abundance. In North American 31 lakes, the timing of maximum Daphnia abundances is linearly related to latitude, with earliest peaks 32 in southern lakes [START_REF] Gillooly | Latitudinal patterns in the size distribution and seasonal 14 dynamics of new world, freshwater cladocerans[END_REF]. [START_REF] Berger | Water temperature and mixing depth affect timing and magnitude 27 of events during spring succession of the plankton[END_REF] found that while experimental 33 cooling of lake enclosures did not affect the timing of the phytoplankton peak, it delayed the peak 34 of Daphnia abundance. However, advances in the timing of the clear water period (presumed to 35 follow the zooplankton peak in abundance), observed in Dutch lakes over 17 years with a water 1 temperature increase of around 0.5°C [START_REF] Scheffer | Climatic warming causes regime 30 shifts in lake food webs[END_REF], may be difficult to attribute wholly to 2 effects of climate warming because of concurrent reductions in nutrient loadings (Van Donk et al., 3 2003). 4 5 An earlier peak abundance of zooplankton has been predicted in warmer years by Scheffer et al. 6 (2001) in a single numerical application of a minimal model, with this model including predation by 7 fish. More recently, [START_REF] Schalau | Temperature is the key factor explaining 25 interannual variability of Daphnia development in spring: a modelling study[END_REF] predicted, using a size-structured Daphnia population 8 model, that temperature rather than food availability is likely to drive inter-annual variability of 9

Daphnia population dynamics during spring: they specifically predicted an advanced timing of peak 10 abundance with warming. In their model, Daphnia grazing and population growth were 11 temperature dependent, but phytoplankton growth was not. In the present experimental study in 12 systems that lacked fish, we predict that peak abundance should occur earlier in response to 13 warming because the growth and grazing of zooplankton is generally more thermally sensitive than 14 is primary production [START_REF] Allen | Linking the global carbon cycle to individual 24 metabolism[END_REF][START_REF] Bissinger | Predicting marine 32 phytoplankton maximum growth rates from temperature: improving on the Eppley curve using 33 quantile regression[END_REF][START_REF] López-Urrutia | Scaling the metabolic 37 balance of the oceans[END_REF]; Rose 15 and Caron, 2007). Another idea, which derives from equilibrium models of populations at carrying 16 capacity [START_REF] Savage | Effects of body 23 size and temperature on population growth[END_REF], but which has not yet been explored in models of transient dynamics, [START_REF] Rolinski | Identifying cardinal dates in phytoplankton 18 time series to enable the analysis of long-term trends[END_REF] is that an increased per capita grazing rate relative to rate of algal production at increased 18 temperatures may reduce the peak standing crop per mass of algal food. 19 20 Timing of peak plankton abundances is also affected by the many other influences on grazer-prey 21 dynamics, including their respective initial abundances at the end of winter, light, and nutrients (e.g. 22 Jäger et al., 2008;[START_REF] Thackeray | Long-term change in the phenology of 34 spring phytoplankton: species-specific responses to nutrient enrichment and climatic change[END_REF]. Trends towards heavier precipitation events with 23 increased frequency will result in altered nutrient run-off into freshwater systems (Jeppesen et al., 24 2009). [START_REF] Thackeray | Long-term change in the phenology of 34 spring phytoplankton: species-specific responses to nutrient enrichment and climatic change[END_REF] concluded that eutrophication and/or climate change induces phenological 25 shifts in phytoplankton and that effects are species dependent. The experimental approach used in 26 the present study can avoid or account for these confounding effects of temperature and nutrients. 27

Experimental approaches are desirable but are expensive to set up and maintain and are therefore 28 rare. Here we present results from a replicated experiment that manipulated temperature and 29 nutrient availability in the absence of planktivorous fish. Fish-free systems are not only likely to 30 become more common as a result of warming, they are already important components of many 31 temperate landscapes as small ponds that are of particular conservation importance for invertebrates 32 and amphibians [START_REF] Biggs | 15 years of pond 29 assessment in Britain: results and lessons learned from the work of Pond Conservation[END_REF][START_REF] Werner | Amphibian species richness 43 across environmental gradients[END_REF]. Using fish-free systems also allowed 33 elimination of a major top-down effect from the bottom-up effects. In an earlier investigation using the same mesocosm tanks as used here, modest influences of a 3°C 1 temperature increase were observed on phytoplankton, zooplankton, macroinvertebrates and 2 macrophytes [START_REF] Feuchtmayr | Response of 4 macroinvertebrates to warming, nutrient addition and predation in large-scale mesocosm 5 tanks[END_REF][START_REF] Mckee | Response of freshwater microcosm communities to 45 nutrients, fish, and elevated temperature during winter and summer[END_REF][START_REF] Mckee | 48 Effects of simulated climate warming on macrophytes in freshwater microcosm communities[END_REF][START_REF] Moss | How important is climate? Effects of warming, nutrient 10 addition and fish on phytoplankton in shallow lake microcosms[END_REF]. [START_REF] Feuchtmayr | Response of 4 macroinvertebrates to warming, nutrient addition and predation in large-scale mesocosm 5 tanks[END_REF] The former experiments used a temperature slightly above the upper limit of predictions made for a 4 business-as-usual scenario by the Intergovernmental Panel on Climate Change in its Second Report 5 published in 1995, on the grounds that there was a trend of increased warming in the predictions 6 being made. These predictions were indeed revised upwards substantially in the Third Assessment 7 of 2002 and the A2, business-as-usual, scenario predicted a 3°C mean global rise by 2100. For the 8 current experiments we thus chose a 4°C rise in line with the considered most likely A2 (regionally-9 orientated economic development) predictions (2.0-5.4°C) over the twenty-first century. These 10 predictions have again been raised in the Fourth Assessment Report of 2007. Experiments have 11 hitherto not been performed on open air plant-free shallow systems at very high nutrient levels that 12 simulate the sort of lake or pond that has already been strongly affected by eutrophication. [START_REF] Gillooly | Latitudinal patterns in the size distribution and seasonal 14 dynamics of new world, freshwater cladocerans[END_REF] richer organic sediment than in the previous experiment [START_REF] Mckee | Response of freshwater microcosm communities to 45 nutrients, fish, and elevated temperature during winter and summer[END_REF], we ensured high 14 levels of phosphorus released to the water column, and with realistic nitrogen loadings we could 15 focus on plankton growth in turbid shallow lakes [START_REF] Scheffer | Alternative equilibria 28 in shallow lakes[END_REF]. 16 17The current experiment explored the effects of 4°C warming and realistically high external nutrient 18 loading on 8-fold replicated plant-free shallow systems during spring. It allowed us to separate 19 temperature from nutrient impacts on zooplankton abundance and on any change in magnitude and 20 timing of peak abundance. Our objectives were: a) to test the influence of warming and nutrient 21 loading on zooplankton abundance, b) to quantify the extent to which the timing of zooplankton 22 peak abundance might be advanced by 4°C warming and nutrient additions, c) to test whether 23 warming affects the peak abundance of zooplankton per unit chlorophyll, d) to test whether nutrient 24 addition increases the peak abundance of zooplankton and e) to describe the impacts of temperature organic cow manure to simulate a sediment of a eutrophic lake or pond), before being filled with 1 around 3000 L of ground water pumped from a borehole. 2 3 A heating element was placed on top of the sediment either as a "dummy" in 24 non-heated tanks or 4 connected to the heating system in 24 heated tanks. In heated tanks, 60°C hot water could be 5 pumped through submerged pipes to increase the water temperature. Water temperature was 6 measured continuously by sensors at a depth of 45 cm, and a computerised feedback system ensured 7 a 4°C higher water temperature in heated tanks compared with adjacent non-heated tanks. Thus, 8 heated tanks follow daily and seasonal temperature cycles of the ambient temperature tanks plus 9 4°C. Heating was switched on in October 2005 and tanks were allowed to settle until January 2006 10 when sampling and monitoring started. 11 12 Two different nutrient additions were superimposed on the heating treatments in a randomised 13 block design from January 2006, via a standard nutrient addition every 2 weeks. Sixteen tanks did 14 not receive nutrient additions (No), while the other two treatments, of sixteen tanks each, received 15 low (Low) and high (High) nitrogen loading (17.9 µM or 250 µg L -1 and 178.5 µM or 2500 µg L -16 1 ), each combined with a constant phosphorus loading (1.6 µM or 50 µg L -1 ) using sodium nitrate 17 (NaNO 3 ) and potassium dihydrogen orthophosphate (KH 2 PO 4 ). Evaporation losses from the tanks 18 were compensated with deionised water to avoid interference with nutrient levels and ionic 19 composition. The study reported here represents the first, fishless phase (1 st of January to 1 st of June 20 2006) of a longer term experiment, which later included fish additions and macrophyte population 21 (NO 3 -N), ammonium (NH 4 -N)), in addition to conductivity, pH (by electronic meter), chlorophyll-3 a (by a submersible fluorometer Cyclops-7, Turner Designs), and zooplankton counts took place 4 every 2 weeks. Oxygen was measured at mid-water (35 cm) depth with a YSI Model 85 5 submersible system between 10.30 and 12.30 hr BST (termed "mid-day"). Temperature was 6 recorded automatically by the sensors and computer system every 15 minutes throughout the 7 experiment. The phytoplankton community was examined microscopically to determine major 8 components. 9 10 Zooplankton samples were taken after sunset to exploit a more equal distribution of the animals 11 within the water column. Ten-litre integrated water samples were taken with a 1-m long tube, mixed 12 in a bucket and concentrated for later transport to around 3 litres with 100-µm mesh size gauze. [START_REF] Gillooly | Latitudinal patterns in the size distribution and seasonal 14 dynamics of new world, freshwater cladocerans[END_REF] Using the same method, the samples were concentrated down to 50 ml and fixed with sugar-14 formaldehyde the next morning. Sub-samples of at least 100 individuals (cladocerans and 15 copepods) were counted under a microscope. Copepod numbers include copepodid stages. Nauplii 16

were not included in the copepod counts nor were rotifers, nor Daphnia neonates containing egg 17 yolk reserves. 18 19 To estimate the time difference caused by treatment (heated vs. unheated and among nutrient 20 additions) for the phytoplankton and zooplankton peaks we applied two different methods. First, we 21 recorded the date when the greatest number in each tank was reached; secondly, for an estimate 22 between the fortnightly samplings we fitted a curve (Weibull-type function) to data from each tank, 23 providing a method for "peak" curve fitting following [START_REF] Rolinski | Identifying cardinal dates in phytoplankton 18 time series to enable the analysis of long-term trends[END_REF], using the cardidates 24 package of the statistical data analysis system R (R Development Core [START_REF] Team | R: A Language and Environment for Statistical Computing[END_REF]

Statistical methods 1

Wherever model residuals from analyses of untransformed data showed evidence of non normality 2 and heteroscedasticity, data were log transformed before applying two-way ANOVAs with time as 3 repeated measure (see Table 1). All analyses were examined for the influence of outliers by plotting 4

Cook's Distances. One-way ANOVAs were applied to test treatment effects on the timing of peak 5 abundances (see Table 2) along with all other comparisons using SPSS 15.0 for Windows®. The 6 same package was used for pairwise post hoc Bonferroni-corrected tests. was 4°C ± 0.1º C higher (Fig. 1). Throughout the period of observation, one heated mesocosm 14 remained anaerobic with very low pH (by the end of May, pH mean ± SE 4.9 ± 0.17 compared 15 with 7.1 ± 0.01 in the other 47 tanks); this outlier was not included in the analyses. 16 17 Mean oxygen concentration and saturation was significantly lower in heated tanks but increased 18 with nutrient additions (Table 1). Among nutrient treatments, oxygen concentration and saturation 19 were significantly higher in the High treatment, but did not differ between No and Low treatments 20 (post-hoc test, p=1.0). Phosphorus released from the sediment resulted in high TP concentrations 21 (154 to 707 µg L -1 ). TP and SRP concentrations in both nutrient-addition treatments were higher 22 than in tanks without experimental addition (Table 1). The post-hoc test showed a significant 23 increase between No and Low treatments (p=0.05) for TP but no significant differences between 24 other pairs. 25 26 TN concentrations were high, ranging from 1.35 mg L -1 to 4.42 mg L -1 , significantly increasing 27 with nutrient loading treatments (Table 1). With warming, TN concentrations were high at the 28 beginning of the experiment possibly due to release from the sediment, but decreased in February to 29 the concentrations in unheated tanks, resulting in significant differences with temperature over time 30 (Table 1). Added nitrate did not persist long in the water and two weeks after addition was generally 31 only detected in low concentrations except in the high nutrient treatment (see The concentration of chlorophyll a was significantly higher in mesocosms with high nitrogen 4 addition than in those with lower addition (pairwise Bonferroni-corrected comparison), but high 5 variation among replicated tanks prevented detection of significant differences with heating (Table 6 1, Fig. 2a). Phytoplankton biomass consisted mainly of Cryptophyceae (around 90%, averaged over 7 all tanks), followed by Chrysophyceae (around 8%), and minor amounts of all other groups. 8 9 Crustacean zooplankton numbers consisted almost exclusively (84 to 96%) of Daphnia pulex. 10 Daphnia magna appeared in May, but in low abundance (mean 1% of total zooplankton numbers). 11

Cyclopoid copepods were relatively abundant until 4 April (mean 11% of total zooplankton 12 numbers), but declined from 18 April onwards (mean 5%) as Daphnia pulex abundances increased. [START_REF] Gillooly | Latitudinal patterns in the size distribution and seasonal 14 dynamics of new world, freshwater cladocerans[END_REF] Non-crustacean zooplankton was dominated by protozoa with little representation of other groups. 14

Total numbers of zooplankters and D. pulex alone increased with nutrient additions, increased 15 significantly with warming and showed strong and significant responses to temperature over time 16 when analysed by 2-way ANOVA with time as repeated measure (Table 1). Crustacean 17 zooplankton abundance continuously increased in heated mesocosms from January to 18 April, and 18 in unheated mesocosms from end of February to 16 May (Fig. 2b). 19 20

The timing of both measured and fitted peak abundances were significantly advanced with heating 21 for total zooplankton, D. pulex-only and for chlorophyll a (see ANOVA results in Table 2, Fig. 3). 22

The measured mean peaks were 24 days, 24 days and 15 days earlier and the fitted mean peaks 23 were 23 days, 22 days and 19 days earlier, respectively. There were also significantly delayed 24 peaks with nutrient addition: 12 days (measured) and 16 days (fitted) for D. pulex and 14 days 25 pulex respectively, Fig. 4a). For nutrient treatments, zooplankton and D. pulex peak abundance was 2 highest in tanks with high nitrogen addition (mean ± SE 1223 ± 174 and mean ± SE 1190 ± 170) 3 compared with low addition (mean ± SE 952 ± 145 and mean ± SE 948 ± 158) and no addition 4 (mean ± SE 992 ± 86 and mean ± SE 968 ± 86), but not significantly different between treatments 5 (F 2,44 = 1.08, p = 0.35, F 2,44 = 0.87, p = 0.43 for total zooplankton and D. pulex respectively, Fig. 6 4b). Chlorophyll a, however, measured on the morning after the zooplankton peak (sampled at 7 night), was lower in the unheated mesocosms than in the heated mesocosms (ANOVA, F 1,44 = 4.77, 8 p = 0.03). Zooplankton per unit chlorophyll a at peak zooplankton abundance was similar in heated 9 and unheated mesocosms (ANOVA, F 1,43 = 1.71, p = 0.2 for zooplankton, F 1,43 = 1.59, p = 0.22 for 10 D. pulex, Fig. 4c) and in the different nutrient treatments (ANOVA, F 2,42 = 2.58, p = 0.09 for 11 zooplankton, F 2,42 = 2.07, p = 0.14 for D. pulex, Fig. 4d) when measured on the morning after the 12 zooplankton peak. 13 suggest that temperature is an important driver of zooplankton growth and its algal food during 21 spring. Our data allowed us: to quantify the extent to which the zooplankton peak abundance in 22 spring is advanced by a 4°C warming, affected by nutrient loading; to test whether high nutrient 23 loadings increase peak zooplankton abundance per unit of food; to test whether 4°C warming 24 reduces peak abundance per unit of food as expected from increased energetic demands; and to 25 explore the consequences for the aquatic system. Surprisingly, temperature and nutrient addition 26 had contrasting impacts on the timing of phytoplankton and zooplankton peak abundances during 27 this early stage of the growth season. days with 4°C warming) or from a linear extrapolation of findings from Lake Müggelsee (47 days 3 for a 4°C increase [START_REF] Adrian | Life-history traits of lake plankton species may 22 govern their phenological response to climate warming[END_REF]). The advance of the zooplankton and Daphnia peak with 4 warming was larger than that of the phytoplankton peak, supporting findings of Schalau et al. 5 (2008), a modelling study suggesting temperature and not food as the dominant factor for 6 determining the timing of spring Daphnia populations. This phenomenon could be explained by the 7 generally higher thermal sensitivity of growth and grazing of heterotrophs compared with primary 8 With climate change, winter precipitation is expected to increase, leading to higher nutrient runoff 12 from the catchment into rivers and lakes (IPCC, 2007), especially in the agricultural lowlands. With 13 higher nutrient availability, phytoplankton growth is less likely to be limited by nitrogen or 14 phosphorus which might result in high phytoplankton division rates leading to earlier peak 15 abundances [START_REF] Thackeray | Long-term change in the phenology of 34 spring phytoplankton: species-specific responses to nutrient enrichment and climatic change[END_REF]. However, phytoplankton abundance is also expected to 16 increase with higher nutrient loading, and similar division rates could lead to higher and thus later 17 peak abundances. Consequently, this might lead to higher and later peak grazer abundances. We 18 found evidence for this hypothesis in our experiment. Chlorophyll a increased with nitrogen 19 addition and the influence of nutrient addition on the date of Daphnia peak abundance was opposite 20 to the temperature effect (Table 2, Fig. 3 controlled by phytoplankton carrying capacity, and hence may correlate with concentration of the 30 limiting nutrient. Our findings confirmed the predicted increased mean chlorophyll a concentrations 31 with nutrient addition (Table 1), but the heights of the zooplankton and D. pulex peaks did not differ 32 between nutrient treatments (see Fig. 4), possibly due to crowding effects. 33 The abundance of Daphnia pulex in the mesocosms was unusually high. Crowding effects of 34 Daphnia are reported to occur at densities of around 150 individuals per litre [START_REF] Burns | Effects of crowding and different food levels on growth and reproductive 35 investment of Daphnia[END_REF] warming, but no difference in heights of the Daphnia abundance peaks with temperature. This lack 5 of a thermal effect could be explained by the occurrence of Daphnia peak abundance at similar 6 temperatures (mean ± SE of 15.3 ± 0.3 °C for unheated and 16.6 ± 0.3°C for heated tanks) 7 irrespective of thermal treatment (also see [START_REF] Gillooly | Latitudinal patterns in the size distribution and seasonal 14 dynamics of new world, freshwater cladocerans[END_REF]. 8 9

In these organic-rich hypertrophic systems, oxygen concentrations were reduced to critical levels 10 for Daphnia survival in the heated tanks, due to respiration of open-water and sediment biota. 11 [START_REF] Weider | Differential response of Daphnia genotypes to oxygen stress: 41 respiration rates, hemoglobin content and low-oxygen tolerance[END_REF] experimentally identified threshold oxygen concentrations for Daphnia 12 pulex of 0.5 to 1 mg L -1 , below which survival of the animals decreased significantly. In 20 out of 13 23 heated mesocosms, mean oxygen concentrations at mid-depth around the zooplankton peaks 14 were lower than 1 mg L -1 , and Daphnia numbers were surprisingly high (see above). The 15 contribution of macroinvertebrates to total respiration is assumed to be small compared with that of 16 the zooplankton, phytoplankton and bacteria, as in this early stage of the mesocosm experiment, 17 general macroinvertebrate abundances were still low (R.J. Moran et al. unpublished data). Increased 18 total community respiration with warming, along with decreasing phytoplankton is likely to have 19 reduced the oxygen concentrations in heated mesocosms to levels that nonetheless probably limited 20 Daphnia growth and reproduction. 21 22 Implications for freshwater systems of a temperature increase similar to that in our experiment are 23 three-fold. First, an increase of water temperature results in a lower dissolved oxygen saturation in 24 shallow hypertrophic systems, and, together with high respiratory oxygen demands associated with 25 both high heterotroph biomass and warming, can lead to severe oxygen depletion. This can affect 26 not only survival of zooplankters but potentially also other invertebrates and fish (Moran et al., 27 2010). With climate warming, shallow eutrophic lakes might increasingly face problems resulting 28 from very low dissolved oxygen concentrations. Secondly, while zooplankton can react rapidly to 29 changes within their environment, the extent to which taxa from higher trophic levels, with longer 30 generation times, such as invertebrate predators and fish, can adjust and cope with the earlier 31 zooplankton peak needs to be addressed in further studies (match/mismatch hypothesis). As fish 32 larvae and planktivorous fish species are dependent on zooplankton as a food source, climate 33 change could have a detrimental effect on the food web in hypertrophic lakes, not only through very 34 low oxygen concentrations but also because of an advanced timing of the zooplankton peak. 35 Concluding from our results that effects of warming and high nutrient load on timing of peak 1 abundances compensate each other might be misleadingly comforting. Even though nutrient 2 addition delayed the peak abundances, mean concentration of chlorophyll a in High treatments was 3 more than 2-fold higher than other treatments, and consequences of high nutrient loading to 4 ecosystems are generally detrimental. 5 6 Thirdly, owing to increased temperatures and an earlier clear water phase, "non-grazeable" algae, 7 such as cyanobacteria, might establish themselves earlier in the season and could then be able to 8 dominate the community over the summer [START_REF] Jeppesen | Climate 26 Change Effects on Runoff, Catchment Phosphorus Loading and Lake Ecological State, and 27 Potential Adaptations[END_REF]. Results of the PROTECH model 9 suggest that warming will increase phytoplankton biomass dominated by the cyanobacterium 10

Anabaena during the summer bloom along with a loss of phytoplankton biodiversity (Elliott et al., 11 2006). Together with heavy nutrient loads, either already in the system or entering via runoff from 12 the catchment, this could result in a substantial change of the ecosystem. However, through an early 13 zooplankton peak and subsequent clear water phase in shallow lakes, the probability of macrophyte 14 development might increase, decreasing the probability of a high phytoplankton biomass because of 15 competition mechanisms. 16 17 So far however, the general consensus is that establishment and stabilisation of a macrophyte-18 dominated system requires a relative increase in the piscivorous fish stock and a reduction in 19 nutrient levels [START_REF] Gonzalez Sagrario | Does high nitrogen loading prevent clear-water conditions in shallow 17 lakes at moderately high phosphorus concentrations? Freshwat[END_REF]. In our experimental ecosystems, despite the high 20 nutrient levels, and in the absence of fish, macrophytes established themselves in all our mesocosms 21 later that summer even in mesocosms in which planktivorous fish were introduced and became 22 established for a subsequent experiment [START_REF] Feuchtmayr | Global warming and eutrophication: effects on water chemistry and autotrophic 8 communities in experimental hypertrophic shallow lake mesocosms[END_REF]. This indicates the establishment 23 of a clear water state in our experimental mesocosms. However, the present study did not 24 incorporate any influence of fish predation on zooplankton, including the effect of temperature on 25 fish offspring and survival [START_REF] Jeppesen | Climatic warming and regime shifts in lake 29 food webs -some comments[END_REF] which might prevent such high zooplankton 26 numbers from occurring and a clear water state from establishing. 27 28 Our findings that the timing of zooplankton peak abundance was advanced by 4°C warming and 29 that oxygen was strongly depleted especially in heated tanks, together with evidence of differences 30 in thermal sensitivity between autotrophic and heterotrophic rates (e.

  and macroinvertebrates were collected from four ponds within the 25 Botanic Garden and a nearby lake, Rostherne Mere, over several weeks and kept in a large storage 26 tank. In January 2006 the storage tank contents were well mixed and sub-samples added to the 48 27 experimental mesocosms. In addition, D. magna was added to each mesocosm as ephippia from a 28 nearby pond in October 2005, and 150 D. magna adults from the same origin on 20 March 2006. 29 Two and three weeks after inoculation, invertebrates were cross-mixed among tanks via 30 standardised sweep-net samples to ensure similar starting conditions. Routine monitoring for water chemistry was based on Johnes & Heathwaite (1992) (total nitrogen 1 (TN), total phosphorus (TP)) and Mackereth et al (1989) (soluble reactive phosphorus (SRP), nitrate 2

  Data shown 25 for chlorophyll-a peak concentrations excludes seven mesocosms, distributed among the different 26 treatments, where chlorophyll-a peaks developed before the start of our 2-weekly sampling regime 27 preventing us from determining peak concentrations and fitting a curve to the data. For better 28 comparison of the timing of zooplankton, D. pulex and phytoplankton peaks, results determined 29 with fitted Weibull-type functions were standardised and Z-scores calculated (the difference in days 30 between peak occurrence in each tank and the average of all tanks, divided by the overall standard 31 deviation, and averaged for the different treatments). Hence, negative z-scores indicate earlier peaks 32 compared with the average time of peak occurrence, positive values indicate later peaks.

7 8 9 10 11

 810 ResultsWater temperature in ambient tanks increased from 4°C in January to about 18°C during the first 12 half of May 2006, with the greatest change in April 2006, while the temperature in the heated tanks 13

  different. For TN, all post-hoc results of nutrient treatments were significantly 1 different. 2 3

(

  fitted) for total zooplankton between No and High treatments (also see Fig2d). Non-significant 26 delays in chlorophyll-a peak concentrations by the High treatment were 8 days (measured) and19 27 days (fitted) (Table2, Fig2c). Z-scores in Figure3show earlier peaks (negative values) for 28 zooplankton, D. pulex-only and chlorophyll a with heating compared with later peaks (positive 29 values) in ambient treatments, that were delayed with increasing nutrient addition.30 31 To test whether warming or nutrient additions affect the peak abundance of zooplankton we 32 calculated mean plankton peak abundances for each treatment (Fig.4.). Peak abundances of 33 zooplankton and D. pulex in heated tanks (mean ± SE 1170 ± 139 and mean ± SE 1158 ± 140) 34 were higher than in unheated tanks (mean ± SE 940 ± 80 and mean ± SE 910 ± 84), but not 35 F 1,45 = 2.02, p = 0.16, F 1,45 = 2.28, p = 0.14 for total zooplankton and D. 1

  experiment using the same tanks, nutrients had a far greater impact on zooplankton, 18 phytoplankton and macrophytes than temperature[START_REF] Feuchtmayr | Response of 4 macroinvertebrates to warming, nutrient addition and predation in large-scale mesocosm 5 tanks[END_REF][START_REF] Mckee | Response of freshwater microcosm communities to 45 nutrients, fish, and elevated temperature during winter and summer[END_REF] 19 McKee et al., 2002;[START_REF] Moss | How important is climate? Effects of warming, nutrient 10 addition and fish on phytoplankton in shallow lake microcosms[END_REF]. Our results, for a slightly greater temperature increase, 20

28 29Increased

 28 temperature induced an earlier peak of chlorophyll-a and zooplankton. As climate 30 warming continues, the evidence from our experiment and studies so far[START_REF] Berger | Water temperature and mixing depth affect timing and magnitude 27 of events during spring succession of the plankton[END_REF] Gerten 31 and Adrian, 2000;[START_REF] Scheffer | Climatic warming causes regime 30 shifts in lake food webs[END_REF] suggest an earlier zooplankton/Daphnia spring peak and 32 subsequent clear water phase. We calculated an advance in zooplankton and Daphnia peak of 22 to 33 24 days with 4°C warming. The advance in peak zooplankton and Daphnia abundance in the heated 34 tanks was consistent with findings from the Bautzen reservoir (23.2 days for 4°C warming(Wagner 35 2007)) and Plußsee (20 to 24 days earlier for a 4°C increase (Müller-Navarra et al., 1 1997)), but was not as early as expected from the regression model of[START_REF] Scheffer | Climatic warming causes regime 30 shifts in lake food webs[END_REF] (33.6 2

  producers (Allen et al., 2005; Bissinger et al., 2008; López-Urrutia et al., 2006; Rose and Caron,

  ); the higher the nutrient addition, the later the Daphnia 21 peak abundance occurred. In contrast, model predictions of nutrient effects on transient Daphnia 22 dynamics by Jäger et al. (2008) showed an advanced timing of the Daphnia peak biomass by 23 phosphorus enrichment. Phosphorus additions used in this study and in the experiment by Jäger et 24 al. (2008) were similar; however nitrogen enrichment was not studied by Jäger et al. (2008). 25 26 Jäger et al. (2008) predicted and observed an increase in Daphnia peak biomass with phosphorus 27 enrichment. A nutrient-enhanced increase in peak abundance of Daphnia is also consistent with the 28 prediction of Schalau et al. (2008) who proposed that the height of this peak should be mostly 29

  the mesocosms, Daphnia pulex reached up to 10 fold higher abundances at peak 1 times when food was plentiful. The simulation of Scheffer et al (2001, their Figure3) suggested a 2 lower predicted peak of zooplankton abundance with 3 °C warming, in accordance with the model 3 of Müller-Navarra et al.(1997). We found higher zooplankton and Dapnhia mean abundances with 4

6 7 8

 68 g. López-Urrutia et al., 2006; 31 Rose and Caron, 2007) lead us to propose that an important component of future research on 32freshwater ecosystem responses to warming should include the difference in thermal sensitivities of 33 rates of consumption, metabolism and production between autotrophs and heterotrophs. In contrast 34 to current predictions of earlier peak plankton occurrence based on phosphorus additions, our 35 delay in the timing of peak zooplankton and D. pulex abundances with phosphorus and 1 nitrogen addition in hypertrophic systems suggests that nitrogen might be a more important driver 2 in freshwater systems than currently accepted. Further, the strong influence of nutrient loading on 3 timing and peak abundances reported here suggests studies on climate warming should include the 4 analysis of nutrient effects. 5AcknowledgementsWe are grateful to Jan Hatton, Ratcha Chaichana, Tom Heyes and Mike O´Connor for help with 9 data collection and measurements, and S. Thackeray, S. Diehl and S. Maberly for helpful comments 10 on an earlier draft of the manuscript. We thank S. Thackeray for support with statistical methods. 11 Financial support was provided by the EU-grant Euro-limpacs (EU Contract No. GOCE-CT-2003-12 505540), funded under the EU Sixth Framework Programme Global Change and Ecosystems 13 theme. Part of this work was conducted while DA was in receipt of a Sabbatical Fellowship at the 14 National Center for Ecological Analysis and Synthesis (NCEAS) and latterly a Leverhulme Trust 15 fellowship. NCEAS is funded by NSF (Grant #DEB-0553768), the University of California, Santa 16 Barbara, and the State of California. 17

Figure 1 19 20Figure 2 27 Figure 3 ZFigure 4

 11922734 Figure 1 Mean daily water temperatures averaged over 24 ambient (open circles) and 23 heated 18 (filled circles) mesocosms from January to end of May 2006. 19 20 Figure 2 Mean ± SE of a) chlorophyll a concentrations (µg L -1 ) and b) crustacean zooplankton 21 abundances (L -1 ) from end of January to end of May 2006 in heated and unheated mesocosms. 22 Mean ± SE of c) chlorophyll a concentrations (µg L -1 ) and d) crustacean zooplankton abundances 23 (L -1 ) from end of January to end of May 2006 in mesocosms with no nutrient addition, low nutrient 24 addition (addition of P and low addition of N) and high nutrient addition (addition of P and high 25 addition of N) . 26 27 Figure 3 Z-scores for chlorophyll a (black bars), total zooplankton (white bars) and D. pulex 28 (diagonally lined bars) peak abundance determined with Weibull-type functions (based on Rolinski 29 et al. (2007)), in 47 mesocosms from February to end of May 2006. Negative z-scores indicate 30 earlier peaks compared with the average time of peak occurrence, positive values indicate later 31 peaks (Treatments: UNo -Unheated and No nutrient addition, HNo -Heated and No nutrient 32 addition, ULow -Unheated and Low nutrient addition, HLow -Heated and low nutrient addition, 33 UHigh -Unheated and High nutrient addition, HHigh -Heated and high nutrient addition). 34 35

  Figure 1 151x121mm (600 x 600 DPI)

25 and nutrients on shallow lake ecosystems. 26 27 Method 28 29 Experimental set-up and treatments 30

		F o r
		P
		e
		e r
		R
		e
		v i e
		w
	31	Forty-eight mesocosm tanks, each 1 m deep and 2 m in diameter, sunk in the ground (see McKee et
	32	al., 2000), are located at the University of Liverpool Horticultural and Environmental Research
	33	Station at Ness Botanic Gardens in North West England (53° 16' N, 3° 03' W), United Kingdom. In
	34	October 2005 the tanks were filled with a 20-cm deep sediment mixture containing (by volume)
	35	50% garden loam and 50% organic material (47.5% chopped organic oat straw and 2.5% rotted

Table 1 )

 1 . Nitrate and 32 ammonium concentrations increased with nutrient addition and warming (Table 1) and among 33 nutrient treatments, pairwise comparisons between Low and High and No and High were 34

Table and Figure legends 2 3Table 1 :

 and1 Effects of heating (H) and nutrient (Nu) loading (no addition No; addition of P and low 4

	5	addition of N Low; addition of P and high addition of N High) over time (t) on water chemistry,
	6	zooplankton abundance and chlorophyll a concentration, in 47 mesocosms from beginning of
	7	January 2006 to end of May 2006 (N=10 for all parameters except where N is given). Results are
	8	from a 2-way ANOVA with time (t) as repeated measure. Wherever results were significant, p
	9	values are indicated as * p < 0.05, ** p < 0.01, *** p < 0.001; ns indicates not significant results.
	10

Table 2 :

 2 Effects of heating (H) and nutrient (Nu) loading (no addition No; low addition Low; high 11 addition High) on timing of zooplankton peak abundance, Daphnia pulex peak abundance and 12 chlorophyll a peak abundance, all calculated as julian day with two different methods: 1) peak 13 abundance sampled, and 2) fitting Weibull functions for 47 mesocosms from beginning of January 14 2006 to end of May 2006 wherever possible. ANOVA results are given, p values are indicated as * 15 p < 0.05, ** p < 0.01, *** p < 0.001; ns indicates non-significant results. 16 17

http://mc.manuscriptcentral.com/jplankt Journal of Plankton Research


Dr Alessandro Brunelli
email: brunellialex@gmail.com

Gaetano Rocco

Dirk Van Raemdonck

Gonzalo Varela

Marcel Dahan

Dirk Van Raemdonck

Lessons learned from the European Thoracic Surgery Database: The Composite Performance Score

Keywords: Lung resections, Quality of care, Composite Performance Score, Process of care, Outcome, Database

come   L'archive ouverte pluridisciplinaire

Introduction

Monitoring quality of care has become an important element in our practice. Third parties demand that our profession is scrutinized in order to provide the best care in a costconscious context.

For this reason, there is a growing interest in our specialty in developing and testing indicators of performance [START_REF] Brunelli | Audit, quality control, and performance in thoracic surgery--a European perspective[END_REF][START_REF] Brunelli | Clinical and nonclinical indicators of performance in thoracic surgery[END_REF][START_REF] Tong | Audit, quality control, and performance in thoracic surgery--a North American perspective[END_REF]. The study of surgical quality is clearly more mature in cardiac surgery, due to imposed governmental reporting requirements [START_REF] Keogh | Toward Public Disclosure of Surgical Results: Experience of Cardiac Surgery in the United Kingdom[END_REF]. Organizational cardiac surgery databases are more robust due to a widespread participation of cardiothoracic surgeons, allowing for overall measurement of clinical data, analysis and benchmarking both at the regional and local levels. A similar effort to collect clinical information has been initiated in general thoracic surgery. Both the Society of Thoracic Surgeons (STS) in the USA and the European Society of Thoracic Surgeons (ESTS) in Europe have developed specific registries with the intent to monitor our practice and implement quality initiatives.

The first version of the ESTS Database was launched in 2001. It was an offline registry and data was submitted using ad-hoc software. Twenty-seven units from 14 Countries contributed a total of approximately 3 000 lung resections for lung tumors over a 3 year period (2001)(2002)(2003). These patients were used to build the first European in-hospital mortality risk model (European Society Objective Score-ESOS) [START_REF] Berrisford | The European Thoracic Surgery Database project: modelling the risk of in-hospital death following lung resection[END_REF]. ESOS was subsequently tested to compare the performance of three different thoracic surgery units [START_REF] Brunelli | Multicentric analysis of performance after major lung resections by using the European Society Objective Score (ESOS)[END_REF], with the intention to provide a template for performance monitoring in our specialty.

Although no difference was found between predicted and observed mortality rates in each unit, it appeared obvious that this lack of discrimination was in part due to the inadequacy of the indicator to assess performance when used alone. Mortality is fortunately a rare event in our specialty, which displays a lot of random noise. Large sample size and a long period of accrual are needed to achieve the sufficient number of events to perform reliable It is now recognized that clinical outcomes are only one measure of overall health care quality [START_REF] Brunelli | Clinical and nonclinical indicators of performance in thoracic surgery[END_REF][START_REF] Brunelli | Multicentric analysis of performance after major lung resections by using the European Society Objective Score (ESOS)[END_REF].

In fact, like intelligence or musical ability, quality is an abstract construct that cannot be measured directly and it is characterized by one or more latent (unobserved) variables or traits. To quantify abstract constructs we typically rely upon some combination of measurable surrogates that are thought to be associated with or contribute to that underlying trait.

A recent document from the STS Quality Measurement task force elegantly explained the conceptual framework and the statistical consideration in the development of Composite Performance Scores in Cardiac Surgery [START_REF] Shahian | Society of Thoracic Surgeons task force. Report of the STS Quality Measurement Task Force. Quality measurement in adult cardiac surgery: part 1-Conceptual framework and measure selection[END_REF].

Based on that methodology, ESTS recently developed and published a Composite

Performance Score (CPS) for lung surgery [START_REF] Brunelli | The European Thoracic Database project: Composite Performance Score to measure quality of care major lung resection[END_REF] based on 1656 patients submitted to major lung resections for malignant primary neoplastic disease in the 10 units contributing more than 50 consecutive cases to the European Database.

CPS comprised the following indicators covering all three temporal domains of our practice (preoperative, intraoperative and postoperative):

1.

The proportion of patients with ppoDLCO estimated in the eligible group with a low ppoFEV1 (ppoFEV1<40%) (9,10)

2.

The proportion of patients with systematic lymph nodes dissection according to ESTS published guidelines (11)

3.

Risk-adjusted in-hospital mortality

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Risk-adjusted cardiopulmonary morbidity (pneumonia, atelectasis requiring bronchoscopy, Adult Respiratory Distress Syndrome, mechanical ventilation longer than 24 hours, pulmonary edema, pulmonary embolism, myocardial ischemia, cardiac failure, arrhythmia, stroke, acute renal insufficiency).

The final composite score combined all these four indicators (2 processes and 2 outcomes) into a single comprehensive quality score after rescaling all measures according to their standard deviations.

Interestingly, the individual 4 rescaled scores (processes and outcomes) showed only a poor or moderate correlation between each other, indicating that these measures complement each other rather than being mutually exclusive.

By using the CPS all units changed their position compared to the rank obtained by using mortality alone. One unit moved from the lower half to the upper half of the rating panel and one from the upper half to the lower half. Forty percent of units moved 2 or more positions. It was clear that the CPS provided a much more reliable and comprehensive assessment of quality of care. To assure consistent directionality, (increasingly positive values reflecting better performance), mortality rates were converted to survival rates (risk-standardized survival rate = 100 -risk-standardized mortality rate), and morbidity rates were converted to "absence of morbidity" rates (risk-standardized absence of morbidity rate = 100 -riskstandardized morbidity rate).

To account for any differences in the measurement scales of the domain-specific scores, Risk-adjusted survival rates varied from 91.5% to 100%. Risk-adjused absence of morbidity rates varied from 50.2% to 97.5%. designed to capture all thoracic procedures but with a particular focus on lung procedures, for which a series of additional standardized variables have been included. The purpose of the ESTS Database is to monitor quality of care across Europe and to develop measures to help participating units to improve their performance.

As of February 2010, 45 European units contributed at least 20 cases, for a total of 4303 lung resections captured over a period of 2.5 years. Eighty percent of data come from the 29 units, which contributed more than 100 cases. It is clear that although the participation is ever increasing and recent implementations will improve recruitment, the current data must be interpreted cautiously as they cannot yet provide a complete representation of the European thoracic surgery practice.

The last version of the ESTS Database Annual Report still shows a great variation in practice and case-mix is evident.

For instance, the proportion of elderly patients (>70 years) operated on in different units may vary from 9% to 45%. Social, geographical, cultural and referral patterns may have influenced this data.

Similarly, the rate of pneumonectomy for malignant primary neoplastic disease, which in some National Registries is regarded as a quality indicator, may vary from as low as 5% to as high as 35%.

Even more striking are the differences in risk-adjusted (according to ESOS-5) mortality rates, which can vary from 0 to 13.5%.

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It is clear that, particularly in Europe, where social, cultural, geographical differences couple with different thoracic surgery educational backgrounds and national regulations, reliable instruments to monitor and standardize practice are most needed. These instruments should be provided at an international societal level through collaborative efforts. ESTS is the ideal organization devoted to improve the quality of European thoracic surgical practice through its multifaceted educational activities. Its role is to "enlighten the path, provide the tools, and set the standards for basic quality inspired practice in order to serve and to protect anyone, from trainee to established consultant ( 17)".

Inspired by these principles, we developed an instrument to monitor the institutional performance based on multiple indicators (either processes and risk-adjusted outcomes) incorporated into a single Composite score.

The score is based on the following principles:

1. Quality assessment should be at the level of the program or hospital rather than the individual surgeon.

2. Quality scores should consider structure, process, and outcomes [START_REF] Donabedian | The quality of care. How can it be assessed?[END_REF].

3. Quality scores should assess three temporal domains: preoperative, operative, and postoperative [START_REF] Shahian | Society of Thoracic Surgeons task force. Report of the STS Quality Measurement Task Force. Quality measurement in adult cardiac surgery: part 1-Conceptual framework and measure selection[END_REF].

4. Quality scores should be interpretable and actionable by providers. the quality of care delivered by healthcare providers. This is particularly true in many surgical areas where the small sample size and the low rate of adverse events diminish the statistical utility of outcomes comparisons [START_REF] Dimick | Surgical mortality as an indicator of hospital quality: the problem with small sample size[END_REF]. Thus, composite indicators may provide a quantitative basis for clinicians, organizations, and planners aiming to improve care and the process by which patient care is provided.

We recognize that some important areas of performance may not be addressed or may be relatively undervalued, and aggregation may also obscure individual areas of strength or weakness. The ability to decompose the composite into its individual components is critical. This allows providers to analyze their performance in specific areas and to formulate improvement strategies [START_REF] O'brien | Society of Thoracic Surgeons task force. Report of the STS Quality Measurement Task Force. Quality measurement in adult cardiac surgery: part 2-Statistical Considerations in Composite Measure Scoring and Provider Rating[END_REF]. The CPS developed in this analysis can be easily decomposed and the units may be evaluated according to their individual scores related to preoperative, operative and postoperative domains.

Limitations:

-Data submitted to the ESTS database are not yet audited. A central and independent audit system is to be implemented to assess quality of data for the participating units.

-Determining a set of valid exclusion criteria for process measures has proven challenging in many areas of medicine, and information on contraindications to various process measures is absent in the European Database. As a result, some patients who are appropriately denied a practice owing to a contraindication will be misclassified as representing a process failure. The true overall percentage compliance with process measures will therefore be underestimated because some ineligible patients are included.

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14

-Because certain outcomes (morbidity) are difficult to define precisely, it is possible that variation in coding practices could account for some of the observed differences between providers.

ESTS Quality certification Program:

It is the natural complement of all the other ESTS educational activities (ESTS School, Annual Congress, Itinerant Courses, Scholarships, Traveling Fellowships) and has been developed with the intent to generally improve and standardize practice of care across

Europe. The concept is to provide the participating units with an instrument to monitor their performance and possibly identify areas of potential improvement through reliable, peerdriven, evidence-based recommended practices.

In order to be eligible for the Quality Certification, units must meet some structural, procedural and professional criteria as long. A minimum 2-year period of consecutive submission of high-quality data to the ESTS Database is a pre-requisite for application.

The data submitted to the ESTS database is essential for calculating the Composite Score as all the standardized outcomes and process indicators are elements of the database.

The units must also demonstrate the presence of a quality surveillance activity performed on a regular basis. o

The Head of the unit or the Clinical Audit Lead, responsible for data collection and quality of care audit, must be an ESTS member.

The above-mentioned criteria and random samples of data submitted to the ESTS Database will be subjected to external audit.

The units meeting the recommended criteria will be eligible and rated centrally by using the CPS. Those with a CPS above the 50 th percentile according to the updated reference table (table 4) will be certified.

To this purpose the CPS reference table will be reviewed and published for transparency in the ESTS Database Annual report.

FINAL COMMENT

Among all stakeholders in health care activities, clinicians are the most interested in quality management programs to ensure that effective practices are implemented in an efficient way in a social environment highly concerned with cost-containment policies.

Professional organizations such scientific societies have a prominent role in promoting evidence based clinical practices and encouraging their members to adopt them and to be involved in programs of continuous improvement of quality of care. The methods depicted in this paper to develop a CPS have been developed under the auspices of the European Society of Thoracic Surgeons and can be adapted to different medical domains. In the future, the CPS will be one of the parameters to be evaluated in the ESTS quality certification program. The following reference table has been derived rating all units with more than 100 lung resections as of January 2010 according to their individual CPS Unit ID

  More sensitive instruments are desirable, which would be capable of providing actionable and timely information and to prevent unnecessary deaths or negative events (2).

8 are

 8 regarded as the outcome rates a unit would have if its case-mix were similar to the average case-mix in the entire population.Determination of Final CompositeScore: Final composite score combined the three process measures with the two risk-adjusted outcome measures into a single comprehensive quality score.

  the scales of measurement were standardized by the reciprocal of their standard deviations (Rescaled score = Original score-Average score of the entire population/ Standard deviation of the entire population). This rescaling method was applied to all the outcome and process indicators before summarizing in the final composite score of each unit. All data was at least 95% complete. Missing data was imputed by averaging the nonmissing values for numerical variables and by taking the most frequent category for categorical variables. All the statistical tests were two-tailed and a significance level of 0.05 was accepted. The analysis was performed by using the STATA 9.0 (Stata Corp., College Station, TX) statistical software M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

Figures 1 to 3

 3 Figures 1 to 3 show the proportion of patients in each unit submitted to the processes of

11 Discussion

 11 Data collection is arguably the most important part of quality assessment.The ESTS database was launched online in July 2007. It is a web-based registry,

5 .

 5 Initial quality reports should focus on lung resection as the most representative operation in our specialty 6. All Quality measures should be available as data elements within The European Thoracic Surgery Database Although quality improvement requires attention to each individual aspect of quality, there are many settings in which the users of quality measures are most interested in the bottom line. Thus, composite indicators seem particularly useful for summarizing and comparing M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 13

The

  ESTS Database Committee and the ESTS Audit and Clinical Excellence ad hoc Committee developed and the ESTS Council approved the following eligibility criteria for the certification (modified in part from the EACTS/ESTS Working Group on Structures in Thoracic Surgery Structure of General Thoracic Surgery in Europe-21) -Structural characteristics: o Dedicated staff and institutional resources.

o- 16 o

 16 operating room per 300-400 major thoracic procedures per year. Access to ICU with experience in thoracic surgical cases. o Dedicated GTS ward, with full supporting paramedical staff and specialized chest physiotherapists. o The size of the unit should reflect the procedural volume and postoperative management policy. o Access to outpatient facilities and radiology. o GTS unit must have easy access to support facilities that must include: hematological, microbiological and biochemical labs, respiratory pathophysiology lab, endoscopic examinations (bronchoscopy, esophagoscopy), cardiologic examination, cardiopulmonary exercise test, radiology including CT scan and PET, cytology, histopathology and frozen section analysis. o In-house facilities for research and education (meeting room, medical libraries, email and internet) -Procedural Volume: o A suggested minimum volume of 150 +/-50 major thoracic procedures per year is recommended. o For esophageal resections a minimum volume of 20 +/-5 procedures per year is recommended. o For lung transplant a minimum volume of 10 procedures per year is recommended. All surgeons must be qualified to perform thoracic surgery according to individual national or European legislation. o The Head of the unit must have a minimum experience of 5 years of clinical practice as qualified thoracic surgeon.

  in patients submitted to major lung resections; Preop invasive mediastinal staging (EBUS, EUS, mediastinoscopy, mediastinotomy, VATS, TEMLA, VAMLA) in patients with clinically suspicious N2 disease (CT scan nodes>1 cm or PET positive nodes); Intraop systematic lymph node dissection in patients submitted to major anatomic lung resections for NSCLC.

  Figure Legend:

Figure 1 :Figure 2 :Figure 3 :

 123 Figure 1: Proportion of patients with DLCO measured before major lung resection in

Table 4

 4 shows the percentile distribution of CPS. The 50% percentile CPS corresponds to 0.404. This reference table has been derived rating all units with more than 100 lung resections as of January 2010 according to their individual CPS.

Table 4 :

 4 Reference table for ESTS Composite Performance Score percentiles (updated as of January 2010)

	Percentiles	CPS score
	25%	-1.004
	50%	0.404
	75%	1.019
	95%	1.24

CONFLICTS OF INTEREST

None of the Authors of the manuscript entitled "Lessons learned from the European Thoracic Surgery Database: The Composite Performance Score" have potential conflicts of interest to declare with the exception to be members of the European Society of Thoracic Surgeons Database Committee.


MD Serge Evrard
email: evrard@bergonie.org

Prof S Evrard

Enhancing Patient Safety and Quality of Surgical Cancer Care: The French National Cancer Plans

Two National Cancer Plans (2003 -2007 and 2009 -2013) have been launched in France to organise the healthcare offer in order to enhance quality and safety. The current Cancer Plan[1] defines regulatory frameworks across the three major areas of cancer therapy: surgery, chemotherapy and radiotherapy. These regulatory frameworks are based on three pillars: transversal requirements for the quality of care; establishment of minimal thresholds for institutions and technical criteria that are required for each type of cancer surgery. Based on adherence to these requirements and following a process of continuous assessment, institutional accreditations (currently being allocated in 2010) will be given for a period of 5 years.

Introduction

The French healthcare system is a plural system. Patients have the choice of being treated in private hospitals, in public non-teaching hospitals, in teaching hospitals or in private hospitals also participating in the public sector. Some structures can be small and quite isolated or, at the opposite end, can be secondary or tertiary referral centres. Specifically for oncology, a special type of hospital exists with the Comprehensive Cancer Centres (CLCC) which are private but also operate in the public sector and which are also teaching Hospitals (20 in France). Given this range in types of institutions, the French Government felt it necessary to ensure minimum standards of care across all institutions offering care to cancer patients, by defining a National Cancer Plan on which institutional accreditations are based.

Prior to the introduction of the first Cancer Plan in 2003, patients with cancer were very dependent on the first practitioner they met in terms of his/her speciality, for example surgeon, medical oncologist, organ specialist or radiotherapist, for the type of care they would receive. The therapeutic proposal was completely up to the practitioner to choose without any obligation to refer to evidence-based medicine, to any medical thesaurus and without any discussion with the other specialists potentially involved in the treatment of the cancer.

Since 2003, two National Cancer Plans (2003 -2007 and 2009 -2013) have been launched to organise the healthcare offer in order to enhance quality and safety, covering three types of cancer treatment: chemotherapy, radiotherapy and surgery. The first plan established the fundamental bases for cancer care in France. The objective of the second plan is to sustain and further the progress achieved by the first plan with a special focus on coordination for post-hospital care, equal access to treatment and innovation. In this paper, we will present the legal requirements surrounding the practice of surgical oncology as determined by these National Cancer plans. It should be noted that oncology is the first medical domain to be discussed and defined as such at a political level which has forced medical professionals to increase the quality of their practices. As an interface between politicians and medical professionals, an Institute was created in 2004, the National Institute for Cancer (INCa) which introduced a new paradigm of medical management in France. As a result of cancer being decreed to be a 'national concern', medical professionals have had to accept limitations on their freedom and to abide by sometimes restrictive rules. INCa has the mission to implement this national policy as the interface between healthcare professionals and the population.

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

4 This process sets the minimum, system-wide, expectations for medical personnel, facilities and services that are required to deliver a consistently high level of care. Accreditation for delivering cancer care services, given for a period of five years, is granted to healthcare institutions (public hospitals, private sector, cancer care centres, etc) and not to individuals, on the condition that they meet and maintain compliance with a number of safety and quality requirements. Healthcare institutions must obtain their accreditation from "regional hospitalisation agencies" (ARH) to be authorised to treat cancer patients. The accreditation allocation process began in November 2008 and has continued throughout 2009 and 2010.

The complete regulatory framework will be fully implemented by the end of 2010. The regulatory framework applicable to all three modalities of cancer treatment including surgery is based on three pillars which will be covered below: transversal requirements, minimum volume thresholds and technical criteria.

TRANSVERSAL REQUIREMENTS

All accredited cancer care providers have to satisfy the following requirements.

Apply the diagnosis "announcement" procedure.

This procedure has been established to announce "bad news" to the patient and his/her family including not only the diagnosis of cancer but also recurrences, aggravation or the necessity of mutilating surgery. Not only is the surgeon implicated but also nurses, psychologists, etc.

Organise multidisciplinary meetings.

Every patient's file has to be discussed by a multidisciplinary team consisting of different specialists like surgeons, organ specialists or medical oncologists, radiotherapists, radiologists, pathologists, etc. Three different specialties are required to be constituent of a multidisciplinary staff meeting. For certain types of difficult surgeries, the physical presence of the surgeon who will do the procedure is mandatory.

Establish an individualized care plan

At the end of the consultation, a document summarising the different steps of the care must be given to the patient.

Implement best practice guidelines

The decision of the multidisciplinary staff meeting must be implemented in reference to good medical practice thesaurus. Two types of thesaurus are available. For chemotherapy, each drug is allowed in specific cases depending on the disease, its stage and the number of therapeutic lines. Secondly, therapeutic algorithms for patient treatment depending on the

Ensure access to supportive care

Every surgical department must participate in a supportive care network.

Enhance access to innovative treatments and clinical trials

The goal for each oncology department is set at including 10% of patients in clinical research programmes. At the same time, all patients asking to participate in a clinical trial should have the possibility to do so. Offers of clinical research programmes are published on different national or regional websites.

MINIMUM VOLUME THRESHOLDS

The second pillar requires that health care institutions meet fixed minimum volume thresholds which are specified for cancer surgery, radiotherapy and chemotherapy. For radiotherapy, the minimum activity threshold for a radiotherapy centre with at least two accelerators is set at 600 patients treated per year. For chemotherapy, each health institution has to treat over 80 patients per year including 50 out-patients. For cancer surgery, the annual minimum activity threshold is fixed at 30 surgical interventions per year for breast cancer, digestive system, urological and thoracic cancers, and at 20 surgical interventions per year for gynaecological, Ear, Nose and Throat (ENT) and maxillofacial cancers.

Despite the fact that all thresholds are fixed at a low level, some healthcare structures will not be accredited for delivering cancer care on the basis that they don't treat enough patients.

However, these healthcare structures treat only a small part of cancer patients, around 5% of the total number of patients.

TECHNICAL CRITERIA

In addition to compliance with these requirements and participation in a regional cancer network, healthcare institutions must also meet certain technical criteria defined by INCa and adopted by its Executive Board in December 2007. The technical standards came into effect at their publication on INCa's official website (www.e-cancer.fr) in June 2008. This detailed set of standards for cancer surgery, radiotherapy and chemotherapy provides comprehensive coverage of critical issues related to the improvement of quality and safety of cancer care.

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

6 Each set of standards has been developed and approved by expert working groups after a comprehensive review of international literature on quality assessment techniques. A consultation took place with key cancer care stakeholders during the drafting of these criteria.

Among these technical standards, some are considered as "fundamental". They consist of specific standards for the implementation of:

-Multidisciplinary approach -Qualification of health professionals (including continuing professional education) -Specific safety rules -Use of self-assessment quality indicators (as defined by INCa) Each discipline; chemotherapy, radiotherapy and surgery, also has specific standards. For surgery, the following technical criteria have been set:

-Surgeons must be qualified in their speciality and justify of sufficient activity in their department even if minimal thresholds are for the centres and not for the surgeon.

-At least one of the surgeons who will participate in the surgery must be present in person or by teleconference at the multidisciplinary meeting.

-Patient files must include at least the report of the multidisciplinary staff meeting, pathologists' reports and an operative report (as defined by INCa).

-Frozen sections of surgical specimen during operations are possible.

-Preservation of pathological specimens in the biobank is organised when needed and following national conventions.

-A training plan is established in the institution for all health professionals involved in surgery.

-Morbidity and mortality survey staff meetings are organised on a regular basis in the institution as part of the quality assurance.

-A self-evaluation of each surgeon's activity is organised yearly. Anonymous data are sent to INCa for national summaries.

In addition, specific requirements exist according to the type of cancer involved in the surgery.

Breast carcinoma

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7

-The practice of oncoplastic surgery and all techniques associated with plastic procedures are possible on the operative platform. The sentinel lymph node detection technique is also available.

-An X-ray of the removed specimen must be done on the operative platform.

-Techniques for the tagging of preoperative lesions are available as is access to a nuclear medicine department.

Digestive surgical oncology -For carcinomas of the oesophagus, the liver, the pancreas, the mid and low rectum, the following rules must be observed at the multidisciplinary staff meeting:

-The patient's file must be discussed and not only recorded.

-The operative strategy must be validated.

-The surgeon who will perform the surgery must be present and be part of the final treatment decision.

-The adequacy of the surgical strategy to the specificities of the technical platform and post-operative follow-up possibilities must be verified.

-Per-operative endoscopy must be available as a technique of interventional radiology. -The patient's file must be discussed and not only recorded.

-The operative strategy must be validated.

-The surgeon who will perform the surgery is present. -Access to coelioscopy is available in the institution ENT surgical oncology -Techniques of endoscopy must be available and collaboration with a maxillo-facial prosthetics laboratory is organised.

Practical implications of the Cancer Plan

A map of the different institutions gaining accreditation for oncological care across the country was published on the INCa website in March 2010 (www.e-cancer.fr). These accreditations will be confirmed after a period of no longer than 18 months. This period can be used by the institutions to verify the conformity of their health care offers to the rules and standards of oncological practice. An accreditation visit will be performed by the Regional Health Agency to finalise the process of certification. After this, the certification is valid for 5 years.

Nationally, 868 health care institutions over 914 geographical sites have received accreditation for at least one therapy: surgery, chemotherapy or radiotherapy [START_REF]Le traitement du cancer dans les établissements de santé en France en[END_REF]. This amounts to a total of 1391 accreditations (more than one per institution). Overall, by far the largest amounts of institutions have been accredited to perform surgery in cancer treatment: 328 institutions are accredited to perform surgery only, 335 to perform surgery and chemotherapy and 90 to perform surgery, chemotherapy and radiotherapy. Twenty four percent (284) of the 1152 hospitals offering such services in 2008 did not meet the criteria for accreditation in 2009. Specifically for surgery, only 754 hospitals of 998 were attributed the label (75%) in 2009. As a consequence, some activities have to be redistributed regionally to institutions that have acquired the authenticating label, particularly for surgery which has the highest rate of redeployment required at 7.8% overall. Percentages of surgical activities to be redeployed per surgery type are shown in Table 1.

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 9

Conclusions

The National Cancer Plan implemented in France serves to continually improve the quality of cancer care offered to patients. Since January 1 st 2010 one last measure to improve oncological surgical safety has been implemented in every French operating theatre. The practice of the surgical check-list [START_REF] Haynes | A surgical safety checklist to reduce morbidity and mortality in a global population[END_REF] is now mandatory before launching a surgical procedure.

To ensure the sustainability of this regulatory framework, evaluation measures will be required in the comings years to check for full adherence to the system from all healthcare professionals involved.

M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT

  M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 stage and the nature of the disease are proposed as standards, options or recommendations due to the level of evidence-based medicine observed.

  Urology surgical oncology -Access to urological interventional radiology is organised and available. Thoracic surgical oncology -The institution allows access to: -tracheo-bronchial endoscopy techniques, -thoracoscopy techniques, -RMN and PET scans. Gynaecological surgical oncology -For ovary carcinoma, requirements of the multidisciplinary staff meeting are as follows:

-

  The adequacy of the surgical strategy to the specificities of the technical platform and post-operative follow-up possibilities must be verified.

Table 1 : Surgical activities process, accredited institutions and activities requiring redeployment over 2008-2009 according to National Cancer Plan accreditations.

 1

	Type of surgery	Number of	Number of	Activities to be
		hospitalisations	health care	redeployed to
			institutions	authorised
				institutions
	Breast	73 735	523	3 671 (5%)
	Digestive	58 919	646	3 595 (5.7%)
	Thoracic	18 151	150	2 099 (11.6%)
	Urology	48 338	462	2 604 (5.3%)
	Gynaecology	17 697	390	3 306 (14.7%)
	ENT	23 668	322	3 489 (14.7%)
	Total	240 508	743	18 528 (7.8%)

Acknowledgements

We wish to thank Pippa McKelvie-Sebileau for help with the English manuscript.