Fish and nutrient enrichment effects on rotifers in a Mediterranean shallow lake: a mesocosm experiment |
| |
Authors: | M R Miracle M T Alfonso E Vicente |
| |
Institution: | (1) Departament de Ecologia i Microbiologia, Universitat de València, Burjassot, Valencia, 46100, Spain |
| |
Abstract: | A mesocosm experiment was conducted “in situ” in a Chara dominated shallow lake near Valencia (Spain) to study top–down and bottom–up effects on rotifers by means of nutrient and
fish additions. Both processes were important in determining rotifer abundance, biomass and diversity. A total of 36 mesocoms
were established with triplicate treatment combinations of three fish levels (from no fish to 45 individuals of Gambusia holbrooki males) and four nutrient enrichment levels (from no additions to 10 mg l−1 nitrate-N and 1 mg l−1 phosphate-P). The main effect was a notable increase of planktonic and plant associated rotifers densities with fish. Rotifers
benefited from mosquitofish predation on microcrustaceans and chironomids. The results showed a marked negative relationship
between rotifer and cyclopoid abundances, indicating the importance of the predatory pressure of cyclopoids on rotifers. Effects
on rotifer diversity were also evident, in general rotifer diversity decreased with nutrients and increased with fish. The
effects of nutrients analysed at species level showed two contrasting density responses: an increase or a decrease with nutrients,
which levelled off at high nutrient concentrations. High-level nutrient additions (from 5 mg l−1 nitrate-N and 0.5 mg l−1 phosphate-P) induced a switch to a turbid state with macrophyte disappearance. Most planktonic rotifer species, as well as
plant associated ones, diminished when the turbid state was well established, especially in the mesocosms without fish. In
the turbid mesocosms, relative abundance of plant-associated rotifers (as a whole) was higher than that of planktonic rotifers.
The changes in rotifer species composition after the switch from a clear to a turbid water state are also described. Species
of the genus Anuraeopsis, Trichocerca and Hexarthra, dominant in the clear water state, practically disappeared in the turbid water state, in which Proalides tentaculatus and Lecane nana were the main species.
Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez
Advances in Rotifer Research |
| |
Keywords: | Planktonic rotifers Plant-associated rotifers Eutrophication Fish predation Macrophytes Community structure Food webs Shallow lakes |
本文献已被 SpringerLink 等数据库收录! |
|