Rousi, H., Laine, A. O., Peltonen, H., Kangas, P., Andersin, A-B., Rissanen, J., Sandberg-Kilpi, E., and Bonsdorff, E. 2013. Long-term changes in coastal zoobenthos in the northern Baltic Sea: the role of abiotic environmental factors – ICES Journal of Marine Science, 70: 440–451. We investigated site-specific changes in a coastal zoobenthic community during 1964–2007 in the northern Baltic Sea. Multivariate analysis indicated that the community structure had changed. The amphipods Monoporeia affinis and Pontoporeia femorata decreased drastically in the late 1970s–early 1980s, and by the early 1990s P. femorata vanished and M. affinis abundance was low. The decline of M. affinis and P. femorata was followed by an increase of the bivalve Macoma balthica and the arrival of the polychaete genus Marenzelleria in the 1990s. Trend analyses showed a rising trend for near-bottom temperature from the late 1960s. There was a significant decline in salinity during the early 1980s, which stabilized during the early 1990s. A negative trend was observed for oxygen concentration during the entire study period. There were interannual variations in the phosphorus and nitrogen concentrations, and a step-like increase in phosphorus concentration at the beginning of the 21st century. The correlations of temperature, salinity, oxygen, total phosphorus and nitrogen with zoobenthic communities were examined using Constrained Correspondence Analysis. Temperature was the most highly correlated explanatory variable for the benthic species. The study highlights the importance of long-term data sets in assessing the state and ecological processes of zoobenthic systems.

No abstract

No abstract

We studied the spatio-temporal impacts of physical and chemical environmental variables (depth, sediment type, salinity, temperature, oxygen, total phosphorus, and total nitrogen) on soft-sediment zoobenthos in the open coastal Gulf of Finland during 2001-2015. The study included 55 sampling-stations covering the east-west gradient of the Finnish coastal zone. The chosen environmental variables significantly influenced the distribution of the species in space and over time. Some zoobenthic taxa formed assemblages with each other, occurring in similar environmental conditions, while Gammarus spp. and Chironomidae clearly differed from other taxa in regards to ecological requirements. We showed the critical influence of oxygen (normoxia, hypoxia, anoxia) on individual species, some better adapted to low oxygen conditions (e.g., Chironomidae) than others (e.g., Monoporeia affinis). The nutrient concentrations in the surface sediment also significantly affected the benthic assemblage patterns. The number of species in space and time increased with increasing oxygen concentrations. This study clearly shows that in order to maintain healthy marine communities, it is essential to counteract excess nutrient inputs and their indirect effects on sufficient O 2 conditions for the benthic habitats.