HR: 1330h
AN: NB33Q-15    [Abstracts]
TI: Baetid mayflies are very messy eaters: evidence from field experiments in a tropical stream, Ilha Grande, RJ, Brazil
AU: * Krsulovic, F
EM: famk@globo.com
AF: Departamento de Ecologia, IBRAG, Universidade do Estado do Rio de Janeiro Rua Sao Francisco Xavier, 524, Rio de Janeiro, RJ 20550-013 Brazil
AU: Moulton, T
EM: bragamoulton@alternex.com.br
AF: Departamento de Ecologia, IBRAG, Universidade do Estado do Rio de Janeiro Rua Sao Francisco Xavier, 524, Rio de Janeiro, RJ 20550-013 Brazil
AB: Mayflies may play an important role in periphyton dynamics. In previous field exclusion experiments, we had found that baetid mayflies (Americabaetis sp. and Cloeodes sp.) had a strong negative impact on periphyton. In this study we quantified the contributions of mayfly consumptive and non-consumptive effects on periphyton in the absence of shrimp. We carried out five field experiments: an egestion rate experiment to quantify periphyton consumed by mayflies and four shrimp exclusion experiments using electricity to exclude shrimps from natural substrate to estimate total removal of periphyton by mayflies. By comparing total removal with estimated ingestion, we estimated non-consumptive loss. We starved mayflies for 0, 3 and 6 h and assumed that periphyton egested would be replaced by ingestion at the same time. We found that, after 3h, 52.8% of the initial amount of periphyton in the mayfly alimentary canal was lost due to egestion, and 77.9% after 6h. During shrimp absence mayflies accumulated over control level and significantly reduced periphyton. Estimated ingestion was 2 to 23% of the periphyton depletion, thus mayfly non-consumptive periphyton removal contributed 98 to 77% of all periphyton lost inside electrified areas. Our results suggest that mayfly have strong negative non-consumptive effects on periphyton.
DE: 4815 Ecosystems, structure and dynamics
DE: 4817 Food chains
DE: 4845 Nutrients and nutrient cycling
DE: 9360 South America
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly