Patterns in nutrient limitation and chlorophyll a along an anthropogenic eutrophication gradient in French Mediterranean coastal lagoons

Abstract

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.

Influence of agriculture and aquaculture activities on the response of autotrophic picoplankton in Laguna Macapule, Gulf of California (Mexico)

“…Further investigation is needed to assess the relative importance of biogeochemical rates and biological interactions in this impacted lagoon. From the perspective of this study, our results suggest, in agreement with other research teams (Souchu et al 2010), that a total nutrient-based approach including dissolved organic nitrogen likely constitutes the most appropriate approach for future studies in this region and similar ones around the world.…”

Impact of contaminated-sediment resuspension on phytoplankton in the Biguglia lagoon (Corsica, Mediterranean Sea)

“…We considered only ammonium enrichment in our experiment, as nitrogen is likely to be the most limiting factor for phytoplankton in the Biguglia lagoon. This lagoon is mesotrophic/ eutrophic (Garrido, 2012;Orsoni and Baldi, 2013), and several previous studies (e.g., Downing et al, 1999;Souchu et al, 2010) have shown that phytoplankton growth is mostly limited by nitrogen in nutrient-rich waters. The microcosms were incubated at 40 cm depth in the lagoon (incubation site; Fig.…”

Distribution of picophytoplankton and nanophytoplankton along an anthropogenic eutrophication gradient in French Mediterranean coastal lagoons

“…We also exploited data from a nutrient database, developed by the Lagoon Monitoring Network (Souchu et al 2010), which records concentrations of dissolved inorganic phosphorus (DIP), dissolved inorganic nitrogen (DIN = NO 3 + + NO 2 + + NH 4 + ) and dissolved silicates (DSi). For each lagoon (Souchu et al 2010), the eutrophication status was estimated according to the succession from phanerogams to macroalgae and/or phytoplankton (Schramm 1999) that has allowed us to distinguish 4 levels of trophic status ( Table 1). The oligotrophic lagoons display transparent waters and a dominance of marine phanerogams with associated macroalgae.…”

“…The numerical dominance of PE-CYAN can thus reflect oligo-mesotrophic conditions in marine coastal waters (Jacquet et al 1998, Caroppo 2000, Gin et al 2003. This dominance could be related to the ability of PE-CYAN, such as Synechococcus, to acquire phosphorus (P) when concentrations are very low (Collos et al 2009 and references therein) because P is the limiting nutrient in the oligotrophic lagoons where PE-CYAN dominate (Souchu et al 2010). Conversely, the numerical dominance of PC-CYAN observed in brackish lagoons is consistent with previous studies showing their predominance in estuarine and freshwater systems (Pick 1991, Camacho et al 2003, Murrell & Lores 2004.…”

“…3 to 6 µm), particularly in eutrophic and hypertrophic lagoons. The pulses of NH 4 + , the major source of DIN entering lagoons from sewage treatment plants (Souchu et al 2010), could also favor the significance of small eukaryotic algae because PEUK (Boutière et al 1982, Gobler et al 2002 and NANO (Collos et al 2003, Wafar et al 2004) have the ability to use, and generally prefer, reduced forms of nitrogen for growth. Rain events may support chain-forming diatom blooms in oligo-and mesotrophic lagoons (L, T, GR, BS) where PEUK abundances are restrained.…”