Brackish-water benthic fauna under fluctuating environmental conditions : The role of eutrophication, hypoxia, and global change

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 O2 conditions for the benthic habitats

Long term regulative effects of Atlantic climatic factors on Archipelago Sea zooplankton biomass - a comparison with terrestrial arctic butterflies

The study investigates the impacts of climatic control (e. g. Winter NAO index, n:o of Ice days, Baltic Regime shifts) on Archipelago Sea zooplankton biomass time series in 1966-2019. Besides, it try to find out whether the Atlantic climatic factors regulate terrestrial arctic butterfly species in a similar way.</p

Zoobenthos as indicators of marine habitats in the northern Baltic Sea

-Zoobenthos are beneficial indicators of habitat quality and environmental stress and change due to their longevity and how they react species-specifically to abiotic factors. This PhD, consisting of four published papers, investigates the effects of physical and chemical variables on zoobenthic species in space and time, as well as the indicator value of the distinct zoobenthic taxa studied. Furthermore, I investigate the linkages between zoobenthos and their habitats in the northern Baltic Sea. The individual studies of this thesis were conducted at different spatial and/or temporal scales. Specific species were found to be indicative of different habitat types. Sediment type (clay, mud, silt, sandy silt, fine sand, coarse sand, gravel, stones) was found to be an important driving factor for zoobenthic species distribution, especially on medium (between ~100 – 1000 m) spatial scales. On a large landscape scale (several kilometres), seabed topographical factors were more significant drivers. The number of species generally increased with increasing topographical complexity, but the most complex habitats were not the most species rich. Physical and chemical factors (temperature, oxygen, nutrients and salinity) in the water significantly impacted species distribution along the Finnish coastal zone of the Gulf of Finland. On the temporal scale of a few decades, drastic changes have occurred in species assemblage composition. The greatest change occurred in the beginning of the 1990s, as the invasive polychaete Marenzelleria spp. arrived and rapidly exponentially increased in abundance. At the same time the crustaceans Monoporeia affinis and Pontoporeia femorata decreased or nearly vanished from the study sites. These changes have had undeniable consequences for the functioning of the ecosystem, due to the different functional traits of the species. The changes in species composition are simultaneous with long-term temperature increases as well as with decreases in salinity and oxygen concentrations in the area. The results of the studies can be applied as a tool to assess species responses to habitat and water quality changes. In addition, the results provide information on the status of the biological diversity in the sediment water interface in the Gulf of Finland during previous decades. In the future it is critical to assess the impacts of the changes in species composition on the functioning of the ecosystem

Parental care in nesting hawks: breeding experience and food availability influence the outcome

Parental food provisioning and sibling rivalry have inspired abundant investigations of evolutionary conflicts within families. Nevertheless, their joint effects have seldom been assessed in relation to parental and environmental state. We investigated state dependency of feeding behaviors through the complete nesting phase in a species whose young both partly beg for food and partly self-feed, the northern goshawk Accipiter gentilis. After hatching, when young relied on being fed beak-to-beak, siblings achieved equal amounts of food irrespective of hatching rank, body condition, and sex. However, mothers new to a territory fed their offspring less than experienced ones independently of food availability. This pattern persisted also after nestlings grew and initiated to self-feed and aggressively monopolize prey. Mothers never interfered with aggressions but stayed with their even feeding strategy paying little attention to begging activity. Although mothers' even feeding strategy is likely to equalize siblings' survival probabilities when food is abundant, the fact that nestlings in good condition monopolize prey in self-feeding situations will boost brood asymmetries when food decreases. Because new mothers feed their offspring less than experienced ones, aggressive sibling rivalry will be particularly crucial among mothers lacking previous local breeding experience. Albeit hitherto overlooked, feeding behaviors constitute important mechanisms explaining experience-related differences in reproductive performance of wild animals. Copyright 2011, Oxford University Press.