The previous week was not very productive in salt lake research papers. Just few of them were indexed by the Web of Knowledge. Nevertheless I selected the favorite paper of the week.
This is almost classical aquatic ecology research on the effect of fish on the food web. The effect of fish on pelagic plankton communities in deep water bodies is well studied and the concept of trophic cascade is the basis for not always successful but assumed to be operative biomanipulation.
What is considered to be evident for deep aquatic habitats and pelagic communities may not valid for shallow waters. Macrophytes increase habitat complexity in shallow waters and act as a refuge for zooplankton and benthic invertebrates which mitigates the effect of fish predation.
However such simple logic is not always works. Fish also can be small and use macrophytes as refuge to escape interactions with larger fish. At the same time small fish living within vegetation will be involved in prey–predator encounters with invertebrates.
Spanish scientists decided to test the effects of small fish on aquatic invertebrates in shallow aquatic ecosystem. They performed a field experiment with mesocosms in a Mediterranean salt marsh, using Aphanius iberus as the small fish species and Ruppia cirrhosa as the dominant macrophyte.
The mesocosms is the main reason why this paper was favored. I prefer studies which bring experimental techniques into field ecology. It is more interesting to manipulate with parameters than to observe natural variations. While it also should be mentioned that mesocosm experiments is not always easy to interpret and scale to ecosystem level.
The research demonstrates that indeed small fish suppress size and species diversity of planktonic organisms. At the same time species diversity and richness as well as total biomass of benthic organisms in the mesocosms with fish increased. Authors conclude that “results suggest that aquatic invertebrates of Mediterranean salt marshes may use macrophytes as refuge from small fish species.”I would conclude that small fish suppress and shape plankton community which allows the development of benthic community. Nevertheless results nicely demonstrate that food webs are highly dynamic and flexible. One who plans to predict (or even model) the effect of manipulation on the food web will always face uncertainty.
Upd. The group which published the paper has exelent web page