Biodiversity in aquatic ecosystems (1 Topic)

1. Analysis of the biodiversity and functioning of the macrofauna community in the different treatment in the experimental ponds at Loenderveen (in cooperation with the university of Amsterdam)

Background
Our starting point was a paper by Loreau et al. (2001) in Science 294: 804-808. According to that paper there was a need to extend our current knowledge on the meaning of diversity for ecosystem functioning to ecosystems other than temperate grasslands. Because top-down control is generally thought to be more common in freshwater than in terrestrial ecosystems significant differences might be expected among ecosystems. With respect to this, the recent paper “Biodiversity and the functioning of aquatic systems” (Giller et al. 2004 Oikos 104: 423-436) should be noted.
On the basis of the paper of Loreau et al. three main questions were originally formulated by us:
(1) Does biodiversity generate biodiversity?
With biodiversity the number of ecological niches may increase. In this way, diversity at one trophic level may lead to an increase in diversity at other trophic levels.
(2) Does loss of biodiversity affect the functioning of ecosystems?
With our present knowledge, we cannot reject the hypothesis that a few dominant species suffice to explain ecosystem properties (e.g. the level of primary production).
(3) Does biodiversity provide an "insurance" against environmental fluctuations?
Biodiversity may be particularly important for maintaining ecosystem functioning under changing environmental conditions. Different species may respond differently, leading to more predictable ecosystem properties.
All in all, the answer to question (2) seems to be yes, and there is to our mind no need to add much there. Much remains to be done in the field of questions (1) impact on associated taxa and (3) in terms of stability and resilience.

Design
Because we want to mimic shallow lakes we constructed large mesocosms (app. 3 x 3 m). The aim is to investigate the effect of submerged macrophyte diversity on the resistance of transparent shallow lakes to increased environmental stresses and on the biodiversity at non-manipulated trophic levels (e.g. macrofauna, plankton, bacteria)
As stressors it was proposed to use (1) nutrient loading and (2) grazing.
We would have two monocultures of resistant species (i.e., resistant to eutrophication and/or grazing), and one diverse community of submerged macrophytes (including these resistant species). With the four treatments in triplicate, we would therefore need 36 ponds (see table below).

Duration 
From March 2009.

Information
Marcel Klaassen, e-mail: m.klaassen@nioo.knaw.nl

The departments of Aquatic Food Webs and Microbial Wetland Ecology also have student projects on this subject.