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In September 2011, we investigated the distribution and composition of dissolved and particulate phosphorus (P) pools throughout Lake Superior, a large P-limited freshwater ecosystem. Average seston particulate P (PP) concentrations in the deep chlorophyll maximum (DCM; 85 ± 28 nmol L−1) were significantly greater than in the epilimnion (63 ± 22 nmol L−1). In contrast, average particulate organic carbon (POC) : PP (mol : mol) ratios showed the opposite pattern (DCM = 303 : 1 vs. epilimnion = 455 : 1). Mean seston nucleic acid—P concentrations were invariant between the epilimnetic (23 ± 18 nmol L−1) and DCM (26 ± 18 nmol L−1) layers, but significantly greater concentrations of intact polar membrane—derived phospholipids were found in the DCM (6 ± 2 nmol L−1) relative to the epilimnion (4 ± 2 nmol L−1). Phospholipids were a minor proportion of PP (7–14%) and total membrane lipids (< 30%). Rather, our results suggest that microbial flora of Lake Superior substituted non-phosphorus lipids for phospholipids. In the nitrogen (N)—rich waters, N-based betaine lipids dominated (39–42%) the lipid pool, and concentrations were significantly greater in the P-poor epilimnetic seston. Sulfolipids were also abundant and significantly greater in the epilimnion (7 ± 2 nmol L−1) than in the DCM (4 ± 2 nmol L−1), despite low sulfate concentrations relative to marine environments. Our results demonstrate for the first time the importance of plankton producing non-phosphorus lipids for phospholipids as a strategy for reducing cellular P inventories in lacustrine regimes.

SUMMARY 1. Wetland eutrophication increases the susceptibility of native communities to invasion by opportunistic plant species, which then commonly form monotypic stands. Wetland aquatic fauna are negatively affected by associated changes of eutrophication in the physiochemical environment, habitat structural complexity and ecological interactions. In addition to reducing external nutrient loads, it is predicted that efforts that reduce the resilience of the altered ecosystem are required to accelerate ecosystem recovery. 2. We assessed small fish and decapod crustacean responses to a 3-year ecosystem scale experiment that tested the effectiveness of chemical treatment and controlled burning as a management strategy to accelerate the recovery of eutrophic Everglades marsh. The management strategy resulted in the removal, on average, of 91% and 81% of the emergent macrophyte cover in two regions differing in enrichment effects. The resulting open-water habitats were characterised by higher dissolved oxygen concentrations, greater periphyton and submersed aquatic vegetation and increased structural complexity. 3. The average combined density and biomass of small fish and decapod crustaceans did not differ significantly between dense emergent vegetation and created openings but regional and water year differences occurred. More importantly, community composition did differ between treatments, with the crayfish Procambarus fallax dominating in dense vegetation and small fish Gambusia holbrooki, Jordanella floridae and Poecilia latipinna and grass shrimp Palaemonetes paludosus dominating in open water. 4. We compared the whole body carbon (C), nitrogen (N) and phosphorus (P) contents (%) and C:N: P stoichiometry among small fish and decapod crustaceans. Fish had greater whole body C and P contents (low C:P) compared with the two crustaceans. While the management action did not alter the quantity (mg carbon m � 2 ) or energy (kcal m � 2 ) of fauna, the resultant shift in composition was coincident with an increase in the nutrient quality (mg P m � 2 and low C:P) of fauna. 5. Faunal community composition of the created open-water habitats in the eutrophic Everglades was similar to the oligotrophic Everglades; however, density and biomass were significantly lower for the oligotrophic region. Moreover, intraspecific comparisons showed that small fish and decapod crustaceans from the oligotrophic region were smaller and had lower whole body phosphorus contents than organisms from eutrophic regions. This suggests that phosphorus limitation in the Everglades extends beyond autotrophs to include consumers. 6. The high density of emergent macrophytes typically formed in eutrophic wetlands creates a physical barrier to predators, limiting the trophic transfer of energy. The combination of burning and chemical treatment not only maintained the abundance and biomass of aquatic fauna, but produced

Production of toxic secondary metabolites by cyanobacteria, collectively referred to as cyanotoxins, has been well described for eutrophied water bodies around the world. However, cohesive cyanobacterial mats also comprise a significant amount of biomass in subtropical oligotrophic wetlands. As these habitats generally do not support much secondary production, cyanotoxins, coupled with other physiological attributes of cyanobacteria, may be contributing to the minimized consumer biomass. Periphyton from the Florida Everglades has a diverse and abundant cyanobacterial assemblage whose species produce toxic metabolites; therefore, by screening periphyton representative of the greater Everglades ecosystem, six different cyanotoxins and one toxin (domoic acid) produced by diatoms were identified, ranging in content from 3 × 10−9 to 1.3 × 10−6 (g · g−1), with saxitoxin, microcystin, and anatoxin-a being the most common. While content of toxins were generally low, when coupled with the tremendous periphyton biomass (3–3,000 g · m−2), a significant amount of cyanotoxins may be present. While the direct effects of the toxins identified here on the local grazing community need to be determined, the screening process utilized proved effective in showing the broad potential of periphyton to produce a variety of toxins.

In wetland habitats, periphyton is a common component of open-water areas with species assemblage determined by local water quality. Extracellular polymeric substances (EPS) secreted by algae and bacteria give structure to periphyton, and differences in EPS chemistry affect the functional roles of these polymers. The Florida Everglades provide a unique opportunity to study compositional differences of EPS from distinctive algal assemblages that characterize areas of differing water chemistry. Water conservation area (WCA)-1 is a soft-water impoundment; periphyton was loosely associated with Utricularia stems and amorphous in structure, with a diverse desmid and diatom assemblage, and varying cyanobacterial abundance. Extracellular polymers were abundant and were loosely cell-associated sheaths and slime layers in addition to tightly cell-associated capsules. The EPS were complex heteropolysaccharides with significant saccharide residues of glucose, xylose, arabinose, and fucose. Carboxylic acids were also prominent, while ester sulfates and proteins were small components. Structured, cohesive cyanobacteria-dominated periphyton was observed in WCA-2A, a minerotrophic impoundment, and filaments were heavily encrusted with calcium carbonate and detrital matter. EPS were primarily cell-associated sheaths, and polymer residues were dominated by glucose, xylose, fucose, and galactose, with uronic acids also a significant component of the polymers. Principal components analysis revealed that periphyton community assemblage determined the monosaccharide composition of EPS, which ultimately determines a range of biogeochemical processes within the periphyton.

We studied patterns of production and loss of four different extracellular polymeric substance (EPS) fractions— colloidal carbohydrates, colloidal EPS (cEPS), hot water (HW)‐extracted and hot bicarbonate (HB)‐extracted fractions—and community profiles of active (RNA) bacterial communities by use of Terminal-Restriction Fragment Length Polymorphism (T-RFLP) analysis of reverse transcription‐polymerase chain reaction amplified 16S rRNA in mudflats in the Colne Estuary, United Kingdom, over two tidal emersion‐immersion cycles. Colloidal carbohydrates and intracellular storage carbohydrate (HW) increased during tidal emersion and declined during tidal cover. The dynamics of cEPS and uronic acid content were closely coupled, as were the HB fraction and HB uronic acids. Changes in monosaccharide profiles of HW and HB fractions occurred during the diel period, with some similarity between cEPS and HB fractions. Increasing enzymatic release rates of reducing sugars and increased reducing sugar content were correlated with increased concentrations of colloidal carbohydrate and cEPS during the illuminated emersion period, and with the amount of HB-extracted uronic acids (the most refractory EPS fraction measured). Loss of reducing sugars was high, with sediment concentrations far below those predicted by the measured in situ release rates. T-RFLP analysis revealed no significant shifts in the overall taxonomic composition of the active bacterial community. However, 12 of the 59 terminal restriction fragments identified showed significant changes in relative abundance during the tidal cycle. Changes in the relative abundance of three particular terminal restriction fragments (bacterial taxa) were positively correlated to the rate of extracellular hydrolysis. Losses of chlorophyll a and colloidal and cEPS (up to 50‐60%) occurred mainly in the first 30 min after tidal cover. About half of this may be owing to in situ degradation, with ‘‘wash away’’ into the water column accounting for the remainder.