Currently, high-latitude marine ecosystems undergo significant changes as a result of global climate change and anthropogenic pressure. In order to avoid negative effects of these changes, effective ecosystem management decisions, based on comprehensive scientific information on ecosystem functioning, are needed. It is very difficult to get thus information because of necessity to study a lot of species. In the current project proposal, we are going to study the trophic group of key planktivorous fish species of the ecosystem, that allow to study mechanisms of ecosystem changes. Upper and lower trophic levels of marine ecosystems are typically characterized by high species diversity, but intermediate level usually consists of several common and abundant species that control main energy and nutrient flows. This trophic level is usually called by scientists as “wasp waist”. Any changes in the abundance of these species well reflect a change in the whole ecosystem and they can be used as effective indicator species of ecosystem changes. In this project we will focus mostly on the three such species which are the most common in the White Sea and the Gulf of Finland of the Baltic Sea – threespine stickleback Gasterosteus aculeatus and herrings Clupea pallasii and C. harengus. We will undertake the comprehensive ecological and population analysis of these species - their spatial distribution, long-term changes, population structure, trophic relationships, parasite-host relationships, intraspecific phylogeography. We are going to use a wide diversity of methods: study of size-age composition of samples, morphological and molecular genetic methods, population modeling, behavior, analysis of stable isotopes of nitrogen and carbon and lipid composition to estimate trophic condition/status, photo and video registration etc. The results of the research will let us to understand the trends and factors involved in the longterm changes in populations of these species as well as the changes in whole temperate and subarctic marine ecosystems, that could be driven by the climate change and rising anthropogenic impact.

The goal of this project is to study the role of the threespine stickleback Gasterosteus aculeatus in the transport of substances and energy between the offshore and inshore communities of the White Sea. The abundance of threespine stickleback in the White Sea changed greatly over the last century, and in the last 15-20 years it has developed from a rather rare species into the most numerous fish species of the White Sea. In the summer in the 30-meter coastal zone, it comprises 95% of the total number of fish in the White Sea. Stickleback spend most of their life on the high seas, but spawning and development of juveniles occurs in the coastal zone, which is why this species is a powerful factor in the horizontal transport of matter and energy. Sexually mature fish that come from the open offshore, serving as food for predatory coastal fishes and seabirds - as well as eggs and juveniles. Juveniles leave offshore and grow there until the maturation. In the framework of this project we will assess: (1) the number of spawners; (2) spatial and temporal (during spawning season) distribution in the inshore zone; (3) value of sexual products of stickleback entering the inshore community; (4) the number of juveniles in the coastal biotopes and their number going offshore. For the research, in addition to the classical methods of ichthyology, video recording and nature experiments will be used. These data, together with data on mortality of stickleback during the spawning period (including that caused by predators), which will be assessed in other projects, will allow us to estimate the amount of substances and energy flow between the inshore and offshore communities controlled by the stickleback. These results, taking into account the data on the density of distribution of fish in the sea, will be extrapolated to the entire White Sea. The results of the project are directly relevant to understanding the relationship between the species and the community, and will also provide an opportunity to better understand the mechanisms of the functioning of marine high-latitude ecosystems and their long-term changes.

Climate change and other anthropogenic impacts are causing major changes in marine ecosystems, especially rapid in the northern seas. Scientific research is needed to forecast these changes and their consequences. Our project in the White and Baltic Seas focuses on the mass fish species threespine stickleback, its population biology, and related predators, food organisms, and parasites.