A Molecular and Stable Isotopic Approach to Investigate Algal and Detrital Energy Pathways in a Freshwater Marsh
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The relative importance of algal and detrital energy pathways remains a central question in wetlands ecology. We used bulk stable isotope analysis and fatty acid composition to investigate the relative contributions of periphyton (algae) and floc (detritus) in a freshwater wetland with the goal of determining the inputs of these resource pools to lower trophic-level consumers. All animal samples revealed fatty acid markers indicative of both microbial (detrital) and algal origins, though the relative contributions varied among species. Vascular plant markers were in low abundance in most consumers. Detritivory is important for chironomids and amphipods, as demonstrated by the enhanced bacterial fatty acids present in both consumers, while algal resources, in the form of periphyton, likely support ephemeropteran larvae. Invertebrates such as amphipods and grass shrimp appear to be important resources for small omnivorous fish, while Poecilia latipinna appear to strongly use periphyton and Ephemeroptera larvae as food sources. Both P. latipinna and Lepomis spp. assimilated small amounts of vascular plant debris, possibly due to unintentional ingestion of floc while foraging for invertebrates and insect larvae. Physid snails, Haitia spp., were characterized by considerably different fatty acid compositions than other taxa examined, and likely play a unique role in Everglades’ food webs.
KeywordsFatty acids Stable isotopes Food webs Detritus Algae Everglades
This work was supported by the U. S. National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Grant No. DBI-0620409 and by funds from Cooperative Agreement H5000060104, Task No. J5284060023, between FIU and Everglades National Park. Analytical support through the SERC Stable Isotope Facility is kindly acknowledged. This is SERC contribution #543.
- Bowen S (1984) Evidence of a detritus food-chain based on consumption of organic precipitates. Bulletin of Marine Science 35:440–448Google Scholar
- Browder JA, Gleason PJ, Swift DR (1994) Periphyton in the Everglades: spatial variation, environmental correlates, and ecological implications. In: Davis S, Ogden J (eds) Everglades: the ecosystem and its restoration. St. Lucie Press, Boca Raton, pp 379–418Google Scholar
- Findlay RH, Dobbs FC (1993) Quantitative description of microbial communities using lipid analysis. In: Kemp PF, Sherr BF, Sherr EB, Cole JJ (eds) Handbook of methods in aquatic microbial ecology. Lewis Publishers, Boca RatonGoogle Scholar
- Gaiser E, Childers D, Jones R, Richards J, Scinto L, Trexler J (2006) Periphyton responses to eutrophication in the Florida Everglades: cross-system patterns of structural and compositional change. Limnol Oceanogr: 617–630Google Scholar
- Gaiser E, Scinto L, Richards J, Jayachandran K, Childers D, Trexler J, Jones R (2004) Phosphorus in periphyton mats provides the best metric for detecting low-level P enrichment in an oligotrophic wetland. Water Res: 507–516Google Scholar
- Light SS, Dineen JW (1997) Water control in the Everglades: a historical perspective. In: Davis SM, Ogden JC (eds) Everglades: the ecosystem and its restoration. CRC Press, Boca Raton, pp 47–84Google Scholar
- Loftus WF (1999) Accumulation and fate of mercury in an Everglades aquatic food web. Ph.D. Dissertation, Florida International University, Miami, p 295Google Scholar
- Napolitano GE (1999) Fatty acids as trophic and chemical markers in freshwater ecosystems. In: Arts MT, Wainman B (eds) Lipids in freshwater ecosystems. Springer, New YorkGoogle Scholar
- Nickum JG, Bart HL Jr, Bowser PR, Greer IE, Jenkins JA, MacMillan JR, Rachlin JW, Rose TD, Sorensen PW, Tomasso JR (2004) Guidelines for the use of fishes in research. American Fisheries Society, BethesdaGoogle Scholar