Structural and trophic alterations in macrobenthic communities downstream from a fish farm outlet
The changes generated by a Spanish trout farm, located in the upper Río Tajuña (Central Spain), on benthic macroinvertebrates were studied by comparing biological characteristics of an upstream station (S-1) with those of three downstream sites placed 0.01 (S-2), 0.15 (S-3) and 1 (S-4) km below the fish farm outlet. In addition, a biological index is presented for estimating relative contributions (informative weights) of major macroinvertebrate groups to the macrobenthic community. Species richness and Shannon diversity were depressed downstream from the trout farm. However, density and biomass values were significantly higher at downstream stations during the summer, presumably due to an increase in water temperature and food supply. Amphipods, plecopterans and planarians were the macroinvertebrates most adversely affected by the fish farm effluent. Coleopterans, ephemeropterans and trichopterans were absent immediately below the outlet (S-2), but exhibited a partial downstream spatial recovery of their informative weights at S-3 and S-4. The abundance of tubificid worms, chironomids, simuliids and leeches increased below the trout farm, with dipterans predominating at all downstream sampling sites. The macrobenthic trophic structure was altered downstream from the trout farm by a significant increase in collectors (gathers and filter feeders) and predators, and a marked decrease in shredders and scrapers. The highest environmental impact was found just below the troutfarm outlet (S-2). It is concluded that the fish farm generates potamological effects on the functional structure of the macrobenthic community. © 1992 Kluwer Academics Publishers.
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| Format: | journal article biblioteca |
| Language: | eng |
| Published: |
1992
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| Online Access: | http://hdl.handle.net/20.500.12792/4938 |
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