Combined effects of hydrologic alteration and cyprinid fish in mediating biogeochemical processes in a Mediterranean stream.
Francesc Rubio-Gracia, David Almeida, Berta Bonet, Frederic Casals, Carmen Espinosa, Alexander S Flecker, Emili García-Berthou, Eugènia Martí, Baigal-Amar Tuulaikhuu, Anna Vila-Gispert, Lluis Zamora, Helena Guasch
Author Information
Francesc Rubio-Gracia: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain. Electronic address: cesc.rubio.gracia@gmail.com.
David Almeida: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain.
Berta Bonet: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain.
Frederic Casals: Department of Animal Science - Wildlife, University of Lleida, 25198 Lleida, Catalonia, Spain; Forest Sciences Centre of Catalonia (CTFC), 25280 Solsona, Catalonia, Spain.
Carmen Espinosa: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain.
Alexander S Flecker: Department of Ecology and Evolutionary Biology, Cornell University, NY 14853, USA.
Emili García-Berthou: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain.
Eugènia Martí: Integrative Freshwater Ecology Group, Centre d'Estudis Avançats de Blanes, CSIC, Accés a la Cala St. Francesc, 17300 Blanes, Catalonia, Spain.
Baigal-Amar Tuulaikhuu: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain.
Anna Vila-Gispert: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain.
Lluis Zamora: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain.
Helena Guasch: GRECO, Institute of Aquatic Ecology, University of Girona, 17003 Girona, Catalonia, Spain.
Flow regimes are important drivers of both stream community and biogeochemical processes. However, the interplay between community and biogeochemical responses under different flow regimes in streams is less understood. In this study, we investigated the structural and functional responses of periphyton and macroinvertebrates to different densities of the Mediterranean barbel (Barbus meridionalis, Cyprinidae) in two stream reaches differing in flow regime. The study was conducted in Llémena Stream, a small calcareous Mediterranean stream with high nutrient levels. We selected a reach with permanent flow (permanent reach) and another subjected to flow regulation (regulated reach) with periods of flow intermittency. At each reach, we used in situ cages to generate 3 levels of fish density. Cages with 10 barbels were used to simulate high fish density (>7indm); cages with open sides were used as controls (i.e. exposed to actual fish densities of each stream reach) thus having low fish density; and those with no fish were used to simulate the disappearance of fish that occurs with stream drying. Differences in fish density did not cause significant changes in periphyton biomass and macroinvertebrate density. However, phosphate uptake by periphyton was enhanced in treatments lacking fish in the regulated reach with intermittent flow but not in the permanent reach, suggesting that hydrologic alteration hampers the ability of biotic communities to compensate for the absence of fish. This study indicates that fish density can mediate the effects of anthropogenic alterations such as flow intermittence derived from hydrologic regulation on stream benthic communities and associated biogeochemical processes, at least in eutrophic streams.
