| title: | The effect of benthic food web and bentic -pelagic coupling on the state of the ecosystem in L. Peipsi |
|---|---|
| reg no: | ETF4986 |
| project type: | Estonian Science Foundation research grant |
| subject: |
1.16. Marine Sciences and Limnology |
| status: | completed |
| institution: | Institute of Zoology and Botany at Estonian University of Life Sciences |
| head of project: | Külli Kangur |
| duration: | 01.01.2002 - 31.12.2005 |
| description: | In the 1990s nutrient content in the surface water of large shallow L. Peipsi decreased. However, phytoplankton biomass (especially that of cyanobacteria) did not follow the dynamics of nutrients but showed an increasing trend. In L. Peipsi, massive long-lasting cyanobacterial blooms were observed in recent years. Hence, one can suppose that internal mechanisms, especially benthic-pelagic interactions can compensate to some extent for decrease in the external load. A key species in the ecosystem of L. Peipsi is probably the filter-feeding bivalve Dreissena polymorpha which serves as a linking organism between the benthic and pelagic systems. The effect and importance of this mussel in the lake ecosystem is yet obscure. Therefore this study focuses on the interactions of Dreissena with the other components of the ecosystem. The aim of the research is: 1) to estimate the grazing rate of Dreissena; 2) to elucidate the effect of Dreissena in the transfer of organic matter from the pelagic to the benthic food web as well as in changing of the composition and abundance of plankton communities; 3) to establish the feeding pressure of fishes on this mussel, 4) to determine what kind of biota populations are the main sources of detritus as well as to establish the share of Dreissena. Hypotheses: 1. Owing to their high filtration capacity of Dreissena, their control over the plankton community in L. Peipsi may be more important than previously assumed. 2. Cyanobacteria, which are more widely distributed in surface water and the colonies of which are large may therefore be less accessible to Dreissena than some other components of phytoplankton. Hence, grazing-resistant cyanobacteria will become more dominating. 3. The resulting siltation deteriorates further the aquatic environment, and hence also the spawning areas of fishes (e.g. vendace). 4. Only a few fishes are able to consume Dreissena and large amounts of this mussel are involved in matter cycling via the detritus food chain, which should reflected in the composition of organic sediments. This project will significantly expand the knowledge of the internal mechanisms of matter circulation in L. Peipsi, also, the results of the project can be used in the prediction of the possible development of this lake, highly important for Estonia. |
| project group | ||||
|---|---|---|---|---|
| no | name | institution | position | |
| 1. | Andu Kangur | EAU IZB | sen. researcher | |
| 2. | Külli Kangur | Institute of Zoology and Botany at the EAU | sen. researcher.. | |
| 3. | Peeter Kangur | EAU IZB | PhD student | |
| 4. | Reet Laugaste | EAU IZB | sen. researcher | |
| 5. | Helle Mäemets | EAU IZB | PhD student | |