Alga - grazer interactions in marine littoral environment

​Regulation of littoral biodiversity by foundation species and trophic cascades

The most fundamental roles in communities are played by foundation species that impose disproportionate influences on community structure and function. In addition, higher trophic levels may generate influences that cascade to lower trophic levels. We focus on littoral communities of the Baltic Sea associated with the foundation species, the rockweed Fucus vesiculosus. We apply recent developments in community genetics and ask how genetic characteristics of a foundation species may extend to community assembly, biotic interactions and to ecosystem function. We then explore top-down regulation by quantifying the roles of herbivores, their fish predators and cormorants, predatory sea birds feeding on fish, in regulating macroalgal communities including the foundation species itself. Loss of foundation species and changes in high-trophic-level species are increasing concerns in all major ecosystems. Our study will contribute to understanding the consequences of these ongoing changes.
Ecological role of herbivory in determining macroalgal species composition
Ecophysiological capabilities of macroalgal species determine their ability to utilize nutrients for growth. However, biological interactions such as competition and herbivory largely determine ecological success of each species. In this part of the project we evaluate the roles of top-down and bottom-up regulation on macroalgal community structure. The aim is to determine species specific responses of the most common algae to herbivory as well as the ecological roles of different grazer groups in affecting algal species composition.

Effects of eutrophication on alga-grazer interaction

Environmental changes associated to eutrophication, increased nutrient availability and turbidity, modify resource availability for algae as well as change the macroalgal species composition. We have shown that such changes reflect to performance of herbivores via food quality and diet composition by increasing growth rate and reproductive output. Therefore, eutrophication increases grazing pressure, which is likely to be harmful especially for the perennial species. In our area, bladder wrack Fucus vesiculosus is the only perennial species that forms a strongly structured habitat harbouring most of the littoral species diversity. Our study focuses on changes in the quality of bladder wrack and other algae as food for herbivores along a natural gradient of ambient nutrient availability.

Evolutionary ecology of algal antiherbivore strategies

A plant defence trait must provide resistance to herbivory by deterring or otherwise harming herbivores. In order to have evolved as a defence, the trait must be costly to produce. The evolutionary potential of such a trait depends on the amount of genetic variation and the patterns of selection for the trait. We are studying the antiherbivory strategies of the bladder wrack focusing on the above questions. Our emphasis is especially in the role of secondary metabolites, phlorotannins, in providing resistance to herbivory.

Geographic mosaic of plant-herbivore interactions

Our study area, the Archipelago Sea, consists of thousands of islands separated by pelagic areas thereby forming a naturally fragmented mosaic environment for littoral species. When dispersal is restricted, such a geographic mosaic creates possibilities for local adaptions. We are studying local adaptations in food plant utilization efficiency of the isopod Idotea baltica, both among populations originating from separate bladder wrack populations and among populations originating from different  host plant assemblages. Our preliminary results suggest that Idotea - Fucus interaction may represent a case of a georapically mosaic interaction.

Digging into chemistry and ecological role of phlorotannins

Brown algae allocate large amount of photosynthetized carbon, up to one fifth in the bladder wrack, into production secondary phenolic metabolites, phlorotannins. Phlorotannins are a group of  compounds that form by polymerization of the basic structural unit. The ecological role of these compounds is controversial, but they probably function as anti-herbivory or anti-fouling compounds. We are developing methods to separate, characterize and quantify different phlorotannin compounds in order to clarify the possible