HR: 09:15h
AN: NB21B-04    [Abstracts]
TI: What They Work at is not What They eat: Incongruence of Strong Interactions and Assimilation in Shrimps and Baetid Mayflies in a Brazilian Coastal Stream
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
AU: de Souza, M L
EM: ecocelo@yahoo.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
AU: Brito, E F
EM: fuentesbrito@aol.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: Krsulovic, F M
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: Silveira, R M
EM: rmlsilveira@hotmail.com
AF: Instituto de Biociencias, Universidade Federal de Mato Grosso, Avenida Fernando Correia, Cuiab , MT 78060-900 Brazil
AU: Ometto, J B
EM: jpometto@cena.usp.br
AF: Centro de Energia Nuclear na Agricultura (CENA-USP), Av. Centen rio 303, Piracicaba, SP 13416-000 Brazil
AB: Exclusion experiments showed that atyid shrimps (Potimirim glabra) and baetid mayflies (Cloeodes sp., Americabaetis sp.) removed benthic material from hard substrate at different sites in the forested stream Rio Andorinha, Ilha Grande, Rio de Janeiro. Their effects were greater on organic material not associated with algae than on algae. Macrobrachium olfersi shrimp had a negative effect on the mayflies, causing a trophic cascade with the benthic material. Gut analysis of the atyid and baetids showed that they ingested large amounts of detritus, as expected. Macrobrachium contained mainly detritus, some algae and some insect parts. Stable isotope analysis of the gut contents confirmed these compositions, but the tissue of the shrimps and mayflies was of carbon derived from algae (as testified by enriched δ ¹³C corresponding to microalgae from the periphyton). Baetids appeared to be algal herbivores and both Potimirim and Macrobrachium appeared (from their δ ¹⁵N signatures) to be secondary consumers. We note that what the animals remove (both by bioturbation and ingestion) and what they assimilate are very different. We speculate that the baetids and atyid are "gardeners" and remove material to promote the growth of algal turf.
DE: 4815 Ecosystems, structure and dynamics
DE: 4817 Food chains
DE: 4845 Nutrients and nutrient cycling
DE: 4870 Stable isotopes
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly