0000000000824410
AUTHOR
María-josé Villena
Fish communities and food web interactions in some shallow Mediterranean lakes
Fish communities of five shallow Spanish Mediterranean lakes were studied and stomach content analysed to determine the foraging pattern of each species and the influence on the lake food web. Lakes ranged from 0.5 to 2300 ha with less than 3 m mean depth, while the trophic state varied from mesotrophy to hypertrophy. We fished during summer 2000 and 2001, and for one lake also during spring 2002. Almost no piscivores species were recorded and in general omnivorous species dominated independently of lake trophic state. Fish dietary differences were found among lakes and prey availabilities. Maximum fish biomass and diversity were found in the Albufera lake, where mugilids (Mugil cephalus an…
Experimental Study on the Diet of Mosquitofish (Gambusia holbrooki) under Different Ecological Conditions in a Shallow Lake
We studied the diet of the eastern mosquitofish Gambusia holbrooki with in situ experimental mesocosms located in a shallow lake. Different nutrient concentrations (phosphorus and nitrogen) and fish population densities were tested. Our results confirm that it is a planktivorous species, with also a great ingestion of algae and detritus. Nutrient fertilization caused almost no changes in this species feeding behavior, but larger mosquitofish stocks induced a shift to zooplanktivory and a decline in detritivory. When macrophytes were present, the predation effect focused on zooplankton and plant-associated animals, otherwise predation on bottom macroinvertebrates increased. Females preyed up…
Mesocosm experiments on nutrient and fish effects on shallow lake food webs in a Mediterranean climate
Summary 1. Nutrient and fish manipulations in mesocosms were carried out on food-web interactions in a Mediterranean shallow lake in south-east Spain. Nutrients controlled biomass of phytoplankton and periphyton, while zooplankton, regulated by planktivorous fish, influenced the relative percentages of the dominant phytoplankton species. 2. Phytoplankton species diversity decreased with increasing nutrient concentration and planktivorous fish density. Cyanobacteria grew well in both turbid and clear-water states. 3. Planktivorous fish increased concentrations of soluble reactive phosphorus (SRP). Larger zooplankters (mostly Ceriodaphnia and copepods) were significantly reduced when fish wer…
Responses of phytoplankton to fish predation and nutrient loading in shallow lakes: a pan-European mesocosm experiment
1. The impacts of nutrients (phosphorus and nitrogen) and planktivorous fish on phytoplankton composition and biomass were studied in six shallow, macrophyte-dominated lakes across Europe using mesocosm experiments. 2. Phytoplankton biomass was more influenced by nutrients than by densities of planktivorous fish. Nutrient addition resulted in increased algal biomass at all locations. In some experiments, a decrease was noted at the highest nutrient loadings, corresponding to added concentrations of 1 mg L1 P and 10 mg L1 N. 3. Chlorophyll a was a more precise parameter to quantify phytoplankton biomass than algal biovolume, with lower within-treatment variability. 4. Higher densities of pla…
Response of a shallow Mediterranean lake to nutrient diversion: does it follow similar patterns as in northern shallow lakes?
Summary 1. In view of the paucity of data on the response of warm shallow lakes to reductions in nutrient loading, this paper presents a long-term limnological data set to document changes in the food-web of a shallow Mediterranean lake (Lake Albufera, Valencia, Spain) that has experienced reductions in phosphorus (P) (77%) and nitrogen (N) (24%) loading following sewage diversion. 2. Nine years after sewage diversion, P concentration in the lake was reduced by 30% but remained high (TP = 0.34 mg L−1), although the mean water retention time in the lake was only 0.1 years. Nitrate concentrations did not significantly change, probably because the lake continued to receive untreated effluents …