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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Food Webs
Effects of low-level nutrient additions on a littoral zone food web in an oligotrophic perched dune lake, as determined using a 15N tracer
W.L. Hadwen, S.E. Bunn, and A.H. Arthington. Centre for Catchment and In-Stream Research, CRC for Sustainable Tourism, Griffith University, Nathan QLD 4111, Australia
In order to mimic nutrient inputs from tourists, repeated additions of low levels of phosphate and 15N-enriched ammonium were made to the littoral zone of an oligotrophic perched dune lake on Fraser Island, Australia. Additions led to substantial increases in periphyton chlorophyll a concentrations in enriched sites, but had no effect on phytoplankton biomass. Furthermore, periphyton collected just 5 hours after the first nutrient addition had elevated δ15N signatures, suggesting that periphyton communities were rapidly assimilating the added nutrients. These findings indicate that ongoing nutrient additions may lead to increased primary (periphyton) and secondary (grazer) production in this system. However, it is possible that considerable increases in periphyton production may escape grazing by consumers, leading to the accrual of substantial algal biomass in the littoral zone. Algal monitoring results suggests that biomass accumulation has already occurred in heavily visited areas of this lake, where nutrient inputs from tourists are likely to be highest. In the long-term, ongoing nutrient inputs from tourists may have adverse ecological and aesthetic effects.
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