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International audience; From the 1980's, Indonesian shrimp production has continuously increased through a large expansion of culturedareas and an intensification of the production. As consequences of diseases and environmental degradations linkedto this development, there are currently 250,000 ha of abandoned ponds in Indonesia. To implement effectiveprocedure to undertake appropriate aquaculture ecosystem assessment and monitoring, an integrated indicatorbased on four criteria using very high spatial optical satellite images, has been developed to discriminate activefrom abandoned ponds. These criteria were: presence of water, aerator, feeding bridge and vegetation. Thisindicator has then been applied to the Perancak estuary, a production area in decline, to highlight the abandonmentdynamic between 2001 and 2015. Two risk factors that could contribute to explain dynamics of abandonmentwereidentified: climate conditions and pond locations within the estuary, suggesting that a spatial approach should beintegrated in planning processes to operationalize pond rehabilitation.

French Mediterranean coastal lagoons have been subject to huge inputs of urban nutrients for decades leading to the eutrophication of these vulnerable ecosystems. In response to new environmental regulations, some of the lagoons have recently been the subject of large-scale management actions targeting the waste water treatment systems located on their watersheds. While the eutrophication of coastal ecosystems is well described, recovery trajectories have only recently been studied. To assess the rapidity and the extent of the effect of the remediation actions, we analysed data from a 14-year time series resulting from the monitoring of nutrients, biomass and the abundance of phytoplankton in the water column of French Mediterranean coastal lagoons covering the whole anthropogenic eutrophication gradient. Following a 50% to 80% reduction in total phosphorus (TP) and total nitrogen (TN) urban loadings from the watershed of hypertrophic and eutrophic ecosystems, the integrative parameters chlorophyll a, TN and TP, provide evidence for a rapid response (1 to 3 years) and for an almost complete recovery, suggesting no hysteresis for the eutrophic lagoon. However, our findings also show that recovery patterns depend on the eutrophication status before remediation and may include feedback responses. The different responses revealed by our results should help stakeholders prioritise remediation actions and identify appropriate restoration goals, especially in light of the targets of the Water Framework Directive (WFD).

International audience; Increases in the intensity of disturbances in coastal lagoons can lead to shifts in vegetation from aquatic angiosperms to macroalgal or phytoplankton communities. Such abrupt and discontinuous responses are facilitated by instability in the equilibrium controlling the trajectory of the community response. We hypothesized that the shift in macrophyte populations is reversible, and that this reversibility is dependent on changes in the pressures exerted on the watershed and lagoon functioning. Biguglia lagoon (Mediterranean Sea, Corsica) is an interesting case study for the evaluation of long-term coastal lagoon ecosystem functioning and the trajectory of submerged macrophyte responses to disturbances, to facilitate the appropriate restoration of ecosystems. We used historical data for a two hundred-year period to assess changes in human activities on the watershed of the Biguglia lagoon. Macrophyte mapping (from 1970) and monitoring data for dynamics (from 1999) were used to investigate the trajectory of the community response. The changes observed in this watershed included a large number of hydrological developments affecting salinity and resulting in changes in macrophyte distribution. Nutrient inputs over the last 40 years have led to a shift in the aquatic vegetation from predominantly aquatic angiosperm community to macroalgae and phytoplankton in 2007 (dystrophic crisis). Changes in hydrological management and improvements in sewage treatment after 2007 led to a significant increase of aquatic angiosperms over a relatively short period of time (4–5 years), particularly for Ruppia cirrhosa and Stuckenia pectinata. There has been a significant resurgence of Najas marina, due to changes in salinity. The observed community shift suggests that Biguglia lagoon is resilient and that the transition may be reversible. The restored communities closely resemble those present before disturbance. These findings demonstrate the need to understand watershed exploitation and ecosystem variability in lagoon restoration.

We explored the role of natural and anthropogenic environmental perturbations in shaping the community structure and dynamics of pico- and nanophytoplankton in coastal waters. The distribution patterns of phycoerythrin-rich picocyanobacteria (PE-CYAN) and phycocyanin-rich picocyanobacteria (PC-CYAN), autotrophic picoeukaryotes (PEUK) and nanophytoplankton (NANO) were examined over a period of 3 yr in 24 Mediterranean coastal lagoons displaying wide trophic gradients (from 0.2 to 630 mu g chlorophyll a [chl a] l(-1)) and salinity gradients (from fresh to marine waters). In summer, picoplanktonic abundances reached 3 x 10(8) cells l(-1), 5 x 10(9) cells l(-1) and 6 x 10(10) cells l(-1) for PE-CYAN, PC-CYAN and PEUK, respectively. PE-CYAN and PC-CYAN showed opposing responses to environmental gradients, resulting in a restricted dominance of PE-CYAN in oligotrophic marine lagoons and a dominance of PC-CYAN in some eutrophic brackish lagoons. Most lagoons exhibited steady-state nutrient conditions, giving competitive advantages to small eukaryotic algae, even in eutrophic and hypertrophic waters. Among the picophytoplankton, picoeukaryotes (ca. 2 to 3 mu m) are the most competitive with increasing nutrient availability; in terms of abundance and biomass, their relative and absolute importance tended to increase with increasing total chl a biomass. Freshwater discharges resulted in large pulses of nutrient and more turbulent systems that altered the structure of the phytoplankton community and stimulated fast-growing NANO composed of phytoflagellates and diatoms (ca. 3 to 6 mu m, up to 1.6 x 10(9) cells l(-1)). Members of the microphytoplankton (ca. 20 to 200 mu m) were rarely observed in eutrophic and hypertrophic lagoons and were composed of harmful dinoflagellates in oligotrophic lagoons. These results show that anthropogenic and meteorological changes are highly influential on the composition and size structure of phytoplankton communities.

Full text : http://archimer.ifremer.fr/doc/00136/24775/22959.pdf (Version "auteur", 0.77 Mo); International audience; This paper describes the building of an integrated simulation tool based on a systems approach, and its contribution to local political discussion of the mitigation of microbiological contamination of the water in a coastal area. Local management schemes view water quality as a high-priority environmental objective. In practice, how far this objective is achieved depends on trade-offs between the costs of improved water treatment facilities and the acceptable impacts of water contamination. An in-the-field experiment in collaboration with local managers was carried out in the Thau lagoon on the French Mediterranean coast during the SPICOSA (Science and Policy Integration for Coastal System Assessment) project, from 2007 through 2011. It consisted of building a modeling platform and an integrated assessment framework for simulating exploratory scenarios. The modeling platform combines a dynamic contamination model, which represents the sources of microbiological contamination, wastewater treatment facilities, and physical mechanisms of lagoon contamination, with a prospective economic model, which estimates the patterns of development of economic activities in the area through a holistic approach. Exploratory scenarios are used to assess the risk of water contamination and the efficiency of management measures, under various assumptions about the evolution of the system. The contamination simulations suggest that the work currently planned by local authorities will be inadequate for preventing increased water pollution, and that additional but fairly inexpensive management measures for maintaining the current level of water quality should be considered. The integrated assessment framework estimates the ecological and socio-economic impacts of the various pollution mitigation policies in the broader context of possible local development patterns. The results illustrate how the systems approach may aid in the design of an applicable water policy based on operational objectives and feasible technical options. (C) 2013 Elsevier Ltd. All rights reserved.

Atmospheric concentrations and deposition fluxes of PCDD/F and PCB have been evaluated over a 1-year period in a Mediterranean coastal lagoon (Etang de Thau, France). Indicative PBDE air concentrations in the hot season are also reported in this work. Sigma 2,3,7,8-PCDD/Fs and Sigma 18PCBs (gas + particulate) air concentrations ranged from 67 to 1700 fg m(-3) and from 13 to 95 pg m(-3), respectively whereas Sigma 8PBDEs (gas + particulate) summer time levels varied from 158 to 230 pg m(-3). The PCDD/F and PCB atmospheric occurrence over Thau lagoon and subsequent inputs to the surface waters are determined by an assemble of factors, being the seasonality of atmospheric concentration, the air mass origin and meteorological conditions important drivers. Total (wet + dry) Sigma 2,3,7,8-PCDD/Fs and Sigma 18PCBs deposition fluxes to Thau Lagoon waters are 117 and 715 pg m(-2) d(-1), respectively.

International audience; The Thau lagoon, located in southern France, suffers episodically from anoxic crises locally known as 'malaigue'. Such crises mostly occur under warm conditions, low winds leading to a strong eutrophication of the lagoon. The development of a sulphur bacterium sometimes gives locally to the waters a 'milky turquoise' appearance and leads to shellfish mortality. One of the indicators of the eutrophication status of the lagoon can be surveyed by the chlorophyll product provided by remote sensing images such as Medium Resolution Imaging Spectrometer (MERIS). In this paper we compare chl2 (or algal2) estimations provided by MERIS level 2 products and the ground measurements of chlorophyll a concentrations in water and we propose a linear correction of the chl2 MERIS product. The corrected chl2 estimations obtained over four years are analysed to understand the seasonal evolution of the trophic status of the Thau lagoon. We also study the influence of the anoxic crises of summers 2003 and 2006 on the chl2 estimations and we find a strong correlation between chl2 and the oxygen percentage at 1 m depth (0.70 for measurements in summers 2003 and 2006).

A cross-ecosystem comparison of data obtained from 20 French Mediterranean lagoons with contrasting eutrophication status provided the basis for investigating the variables that best predict chlorophyll a (Chl a) concentrations and nutrient limitation of phytoplankton biomass along a strong nutrient enrichment gradient. Summer concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) comprised only a small fraction of total nitrogen (TN) and total phosphorus (TP). On the basis of inorganic nutrient concentrations, the most oligotrophic lagoons appeared to be phosphorus-limited, with a tendency towards the development of nitrogen limitation as eutrophication increased, as evidenced by decreasing DIN:DIP ratios. A weak but significantly positive relationship was found between dissolved silicate (DSi) and Chl a, reflecting DSi accumulation in the water column along the trophic state gradient and implying a progressive shift away from potential Si limitation of phytoplankton growth. Observed concentrations of Chl a were far better explained by TN and TP than by DIN and DIP concentrations, suggesting that a total nutrient based approach is likely to be the most appropriate for managing eutrophication in Mediterranean lagoons and other coastal waters. These results give credence to the idea that marine and freshwater environments respond in a similar fashion to nutrient enrichment., Une comparaison inter-sites des concentrations de nutriments et de chlorophylle a (Chl a) issues de 20 lagunes de Mediterranee francaise de degres divers d'eutrophisation a ete menee afin de rechercher la meilleure variable expliquant le niveau de Chl a et d'explorer la limitation de la production primaire par les nutriments au long d'un fort gradient d'enrichissement en azote et phosphore. En ete, l'azote et le phosphore inorganiques dissous (DIN et PID respectivement) constituaient une faible fraction des concentrations d'azote et de phosphore totaux (TN et TP respectivement). Sur la base des concentrations en nutriments inorganiques, la plupart des lagunes oligotrophes semblaient limitees par le phosphore avec une tendance vers des rapports DIN:DIP decroissants, et donc une limitation par l'azote, lorsque l'eutrophisation augmentait. Une correlation positive mais faible a aussi ete obtenue entre les concentrations de silicates (DSi) et Chl a, indiquant une accumulation de DSi dans la colonne d'eau et donc une diminution de la limitation de la croissance du phytoplancton par la silice au fur et a mesure que l'eutrophisation augmentait. Le fait que Chl a etait beaucoup mieux expliquee par TN et TP que par DIN et DIP suggere meme que l'approche limnologique basee sur l'ensemble des nutriments est vraisemblablement la meilleure pour gerer l'eutrophisation dans les lagunes mediterraneennes et dans d'autres ecosystemes marins cotiers. Ces constats renforcent l'idee que les ecosystemes marins et d'eau douce repondent de facon similaire a l'enrichissement en nutriments.

Time series data have been examined in Thau lagoon (Southern France) from 1972 to 2006 for water temperature, salinity, nutrients and from 1987 to 2006 for phytoplankton. A first main trend identified is an increase in mean annual water temperature (1.5 degrees C over 33 years or 0.045 degrees C/year) that was not evenly distributed among seasons. The highest rate of increase was in the spring (+ 3.0 degrees C over 33 years), followed by summer (+ 2.0 degrees C and fall (+ 1.7 degrees C. In winter, no significant increase over the 33 year period could be found. A second clear trend is a large decrease in soluble reactive phosphorus (SRP) concentration over the same 33 year period (summer values decreased from 10 mu M to 1 mu M. while winter values decreased from 3 mu M to undetectable at present). Nitrate concentrations depended mainly on rainfall events and watershed runoff. Ammonium data were too fragmentary to be useful. N/P ratios expressed the traditional way of DIN/SRP cannot be used for phytoplankton that are not strict autotrophs. The recent and almost simultaneous appearance of both picocyanobacteria (mostly Synechococcus) and the toxic dinoflagellate Alexandrium catenella in Thau seem to be related to reduced nutrient loading and the increase in water temperature. A. catenella blooms occur either in the spring or the fall when water temperature is near 20 degrees C and remains so for several weeks with winds speeds below 2-3 m s(-1). Picocyanobacterial growth is stimulated by increased summer temperatures, and lowered SRP levels provide picocyanobacteria an ecological advantage over other phytoplankton classes, in particular diatoms such as Skeletonema costatum whose cell densities have decreased over the last 8 years in summer and fall, but not in winter. An hypothesis is presented according to which A. catenella is not stimulated by increased temperatures, but is able to use picocyanobacteria for growth, and this provides this organism an additional resource over other strictly autotrophic phytoplankton. On a more general level, our data do not support the hypothesis that increased nutrient loading leads to harmful blooms of dinoflagellates. Instead, a combination of habitat disturbance and species displacement seems to lead to such blooms. (C) 2008 Elsevier B.V. All rights reserved.

Ambient concentrations, congener patterns and multi-media distribution of PCDD/Fs and PCBs were determined in air, water, sediment and mussels in a semi-enclosed marine ecosystem (Thau lagoon, France). Sigma 2,3,7,8-PCDD/F and Sigma 7ICES PCB air concentrations (0.2-1.4 and 31-57 pg m(-3), respectively) were typical of rural areas. Concentrations in the water column were very low for PCDD/Fs (163-476 fg L-1) and low for PCBs (138-708 pg L-1). PCDD/F and PCB concentrations found in surface sediment (0.15-1.6 and 2.5-33 ng g(-1) d.w., respectively) and mussel (13-21 pg g(-1) d.w. and 10-39 ng g(-1) d.w., respectively) were medium levels. PCDD/F congener patterns observed in air, water particulate phase and sediments were similar suggesting direct coupling among these compartments and atmospheric inputs of PCDD/Fs into the lagoon. Conversely, for the same set of samples, similar patterns were not observed for PCBs in the mentioned compartments. (C) 2007 Elsevier Ltd. All rights reserved.

A monitoring program with a weekly sampling frequency over a 15-month period indicates that urea concentrations above a certain threshold level may trigger the blooms of Alexandrium catenella in Thau lagoon. However, urea concentrations were also sometimes related to ammonium and dissolved organic nitrogen concentrations, indicating that the role of urea may not be a direct one. An original approach is used to assess the relative contribution of several nitrogen sources (nitrate, nitrite, ammonium, urea) to growth of A. catenella by comparing nitrogen uptake rates to nitrogen-based growth rates estimated from dilution experiments during four blooms over a 4-year period (2001-2004) in Thau lagoon. Nitrate and nitrite contributed 0.1-14% and 0.1-5% respectively of growth requirements. Ammonium and urea were the main N sources fueling growth of A. catenella (30-100% and 2-59%, respectively). Indirect estimates indicated that an unidentified N source could also contribute significantly to growth at specific times. Concerning ammonium and urea uptake kinetics, half-saturation constants varied between 0.2 and 20 mu gat NL-1 for ammonium and between 0.1 and 44 mu gat N L-1 over the 4-year period, indicating that A. catenella can have a competitive advantage over other members of the phytoplankton even under low concentrations of ammonium and urea. However, the observed large changes in ammonium and urea uptake kinetics on a short time scale (days) during blooms preclude more precise estimates of those contributions to growth and require further investigation. (C) 2007 Elsevier B.V. All rights reserved.