How would you describe your project in a few sentences?
Blooms of nitrogen-fixing toxic cyanobacteria are of concern in ecosystem management worldwide. The aim of our project is to understand the role of bloom-forming cyanobacteria in the productivity of the Baltic Sea. To do that, we are developing a new approach combining molecular and isotopic analyses and use it to quantify grazing on bloom-forming cyanobacteria in the pelagic food webs.
What are your most important results, and for whom are they particularly useful?
Currently, management decisions are based on the assumption that cyanobacterial production is of no positive value, because it cannot be efficiently utilized by grazers and, hence, does not propagate into food webs. We show that cyanobacteria are an important food source for zooplankton grazers during summer, which means that they should be accounted for when analyzing energy flows, fish nutrition, and productivity mechanisms in this system. We also found that some zooplankton species have a greater capacity than others to utilize cyanobacteria, with beneficial effects on growth and reproduction. Thus, changes in the bloom intensity and frequency may lead to evolutionary change in the Baltic zooplankton communities.
How can it assist an ecosystem-based management of the marine environment?
The main challenge for management of cyanobacteria blooms in the Baltic Sea is to establish ecological threshold levels for these blooms, where the beneficial effects on productivity override detrimental effects on growth and reproduction of pelagic and benthic animals as well as negative effects on tourism and recreation. Our results quantifying the contribution of cyanobacterial blooms to zooplankton feeding are critical for determining these thresholds as well as for various food web and nutrient cycling models that current management decisions are based on, including models assessing fish production and nutrient reductions in the Baltic Sea.
