RESUMEN
Eutrophication of the Florida Everglades, USA, has altered the characteristics of the ecosystem, but management strategies are being implemented to accelerate recovery. In this study, we described lipid compositional similarities and differences between periphyton, fish, and crustaceans, and explored if eutrophication and creation of new open-water sloughs in phosphorus (P)-impacted regions of a Northern Everglades impoundment resulted in changes in periphyton biomass and lipid composition, and the lipid composition of a ubiquitous omnivore, Gambusia holbrooki. Lipid biomarker analysis provided insight into microbial community composition, quality of basal resources, and potential resources utilized by consumers. Periphyton biomass and phospholipid fatty acid (PLFA) composition differed in response to eutrophication, but not between P-impacted control and treatment plots. Shifts in relative abundances of lipids indicative of diatoms and green algae mirrored known taxonomic shifts due to eutrophication. For fauna, PLFA were a small and relatively distinct component of the overall total lipid make-up, and profiles were similar between control and treatment plots. However, the PLFA profile of G. holbrooki differed between oligotrophic and eutrophic regions. Fish and crustacean lipids contained significantly greater relative abundances of polyunsaturated fatty acids than were found in periphyton, and profiles differed between fish and crustaceans, suggesting organisms were selectively accumulating or elongating and desaturating lipids de novo, to meet physiological needs. This study builds on findings of microbial responses to eutrophication and recent observations that consumer PLFA profiles can also shift with P-enrichment.
Asunto(s)
Lípidos/análisis , Animales , Biomarcadores/análisis , Crustáceos , Eutrofización , Peces , Florida , Perifiton , Estados UnidosRESUMEN
Alterations in microbial community composition, biomass, and function in the Florida Everglades impacted by cultural eutrophication reflect a new physicochemical environment associated with monotypic stands of Typha domingensis. Phospholipid fatty acid (PLFA) biomarkers were used to quantify microbial responses in detritus and surface soils in an active management experiment in the eutrophic Everglades. Creation of open plots through removal of Typha altered the physical and chemical characteristics of the region. Mass of PLFA biomarkers increased in open plots, but magnitude of changes differed among microbial groups. Biomarkers indicative of Gram-negative bacteria and fungi were significantly greater in open plots, reflective of the improved oxic environment. Reduction in the proportion of cyclopropyl lipids and the ratio of Gram-positive to Gram-negative bacteria in open plots further suggested an altered oxygen environment and conditions for the rapid growth of Gram-negative bacteria. Changes in the PLFA composition were greater in floc relative to soils, reflective of rapid inputs of new organic matter and direct interaction with the new physicochemical environment. Created open plot microbial mass and composition were significantly different from the oligotrophic Everglades due to differences in phosphorus availability, plant community structure, and a shift to organic peat from marl-peat soils. PLFA analysis also captured the dynamic inter-annual hydrologic variability, notably in PLFA concentrations, but to a lesser degree content. Recently, use of concentration has been advocated over content in studies of soil biogeochemistry, and our results highlight the differential response of these two quantitative measures to similar pressures.