Seamless Maps and Management of the Bothnian Bay SEAmBOTH - Final report Authors Bergdahl Linnea2, Gipson Ashley1, Haapamäki Jaakko1, Heikkinen Mirja5, Holmes Andrew2, Kaskela Anu6, Keskinen Essi1, Kotilainen Aarno6, Koponen Sampsa4, Kovanen Tupuna5, Kågesten Gustav3, Kratzer Susanne7, Nurmi Marco4, Philipson Petra8, Puro-Tahvanainen Annukka5, Saarnio Suvi1,5, Slagbrand Peter3, Virtanen Elina4. Co-authors Alasalmi Hanna4, Alvi Kimmo6*, Antinoja Anna1, Attila Jenni4, Bruun Eeva4, Heijnen Sjef9, Hyttinen Outi6, Hämäläinen Jyrki6, Kallio Kari4, Karén Virpi5, Kervinen Mikko4, Keto Vesa4, Kihlman Susanna6, Kulha Niko4, Laamanen Leena4, Niemelä Waltteri4, Nygård Henrik4, Nyman Alexandra6, Väkevä Sakari4 1Metsähallitus, 2Länsstyrelsen i Norrbottens län, 3Geological Survey of Sweden (SGU), 4Finnish Environment Institute (SYKE), 5Centres for Economic Development, Transport and the Environment (ELY-centres), 6Geological Survey of Finland (GTK), 7Department of Ecology, Environment and Plant Sciences, Stockholm University, 8Brockmann Geomatics Sweden AB (BG), 9Has University of Applied Sciences, *Deceased Title: Seamless Maps and Management of the Bothnian Bay SEAmBOTH - Final report Cover photo: Eveliina Lampinen, Metsähallitus Authors: Bergdahl Linnea, Gipson Ashley, Haapamäki Jaakko, Heikkinen Mirja, Holmes Andrew, Kaskela Anu, Keskinen Essi, Kotilainen Aarno, Koponen Sampsa, Kovanen Tupuna, Kågesten Gustav, Kratzer Susanne, Nurmi Marco, Philipson Petra, Puro-Tahvanainen Annukka, Saarnio Suvi, Slagbrand Peter, Virtanen Elina. Contact details: Essi Keskinen, project coordinator, Metsähallitus Telephone: +358407544525 Email: [email protected] Website: www.seamboth.com ISBN 978-952-295-268-4 (pdf) Metsähallitus, Parks & Wildlife Finland, Vantaa, 2020 2 Summary The SEAmBOTH project (Seamless Maps and Management of the Bothnian Bay) was a collaboration (2017-2020) project between Sweden and Finland and included partners from Parks and Wildlife Finland (Metsähallitus), County Administrative Board of Norrbotten (Länsstyrelsen Norrbotten), Geological Survey of Sweden (SGU), Geological Survey of Finland (GTK), Finnish Environmental Institute (SYKE), Centre for Economic Development, Transport and the Environment in Northern Ostrobothnia and Lapland (ELY centers POP and LAP). The main funders of the project were Interreg Nord, Swedish Agency for Marine and Water Management (SWAM) and Lapin liitto. The project had a focus on sustainable management of the northern Bothnian Bay, as well as increasing the knowledge of the marine environment and promoting collaboration across the border. The main goal of the project was to ensure the conservation of the habitats, ecosystems, and biodiversity of the Bothnian Bay, through efficient planning, sufficient knowledge, and management of the area. The end products of the project (e.g. marine maps, species identification guides and workshop reports) are intended for use by environmental agencies, the general public, and any other organization that may need them. The project area was the northernmost part of the Bothnian Bay (which is itself the northernmost part of the Baltic sea). It reaches from Luleå, Sweden, to the south of Oulu, Finland. Bothnian Bay is a unique marine area characterized by low salinity levels, brackish waters, and a unique mix of freshwater and marine species, with ice cover half year-round. Before the start of the SEAmBOTH project, the amount of available data of the seafloor, species and habitats were low, making assessment of e.g. biodiversity and conservation status difficult. The marine area of the Bothnian Bay is divided by the border between Sweden and Finland and is therefore a shared responsibility of both countries. The northern Bothnian Bay is characterized by freshwater runoff from several large rivers causing low salinity levels (~1–3 PSU). Rivers are also a main source of humus, phosphorus and nitrogen in the area. The humic content of water is quite high, but turbidity and the amount of suspended solids is low outside the river estuaries. Although several large rivers flow into the northern Bothnian Bay, highly influencing the area, the nutrient levels are quite low, reflecting mainly oligotrophic conditions. The SEAmBOTH project used satellite observations (EO, Earth Observation) to detect spatial and temporal changes in the water quality in the area of the Bothnian Bay. It was found that water quality parameters such as turbidity and CDOM could be estimated well in the Bothnian Bay using Sentinel-2 satellite observations. The water quality estimates provided by high resolution instruments are especially valuable in coastal regions, whereas moderate resolution instruments can cover open sea areas with more frequent coverage. With Sentinel-3 satellite OLCI data, examples of Chl-a time series with good correspondence with station sampling were shown at many of the investigated stations. However, the best performing Chl-a algorithm (MPH) was not developed for areas with low Chl-a concentration and extreme aCDOM (brown/humic) waters and over stations with this combination of water type, the performance was not convincing. Dedicated development of an algorithm to estimate Chl-a in high aCDOM waters is a task for future research and development projects. The in-situ dataset collected during SEAmBOTH was a valuable resource for the algorithm testing and development. However, development of water quality algorithms over dark water types requires long time series before a sufficient level of confidence in the results can be reached. It is therefore recommended that water quality sampling is kept at high level in this northern region of the Baltic Sea, and that the sampling follows the optical protocols developed and utilized during the project. In addition to determining the in-situ concentrations of Chl-a, CDOM and turbidity, it is also important in the future to collect more data on the inherent optical properties of the water. Getting improved information about the water depth in coastal areas is also important. During the project, a number of algorithms were analysed, which continuously will be updated. Thus, it would be valuable to repeat the analyses with additional data and new versions at a later date. Usually, at least 25–30 match-ups between satellite and in situ data are required, to derive the uncertainties statistically. Hopefully, this can be accomplished in a follow-up project on the Bothnian Bay. To understand the marine ecosystems, it is key knowledge to understand and map the seafloor abiotic environment which the ecosystems build on. Geological knowledge helps us understand the past and the present environment and is a vital piece of information when attempting to understand how the environment may look in the future. The existing charts and geological maps in the northern Bothnian Bay have generally been old, patchy, and coarse. To improve this knowledge, the focus of the geological mapping activities in the SEAmBOTH project was two-fold: ship-based mapping of selected “pilot” areas in high resolution with state-of-the-art survey techniques, as well as spatial modelling for the larger project area. The pilot areas were selected to provide valuable maps and knowledge of important areas, but they also allowed alignment and comparison of mapping techniques between Finland and Sweden, as well as provided a window of good data to compare with all other maps. 3 The seafloor in the region is relatively shallow with a mean depth of 19 meters, and deepest areas around 125 meters. The geologically young sea area, in large shaped by the last ice age, is full of structurally complex features. Canyons or canyon-like seabed features are the most striking broad scale geomorphological features noted. These canyons are probably ancient river channels, which formed when the water level was significantly lower than today. Examples of fine scale geological/geomorphic features discovered were erosional hard clay structures. These structures consist of a very compact clay, and they can create complex reef like structures. Features related to sediment transport (e.g. ripples), have also been observed in the area. The canyons and deeper parts are mainly filled with soft clay and mud while the shallower and wave exposed areas above 30 meters are often covered with a mix of sand, gravel and rocks. However, modern mud accumulation seems to mainly occur in the water depths shallower than 40 meters. Scattered occurrences of small hard clay features seem fairly common, though challenging to map due to their small area coverage and patchy occurrence. Hardbottom such as rocks and large boulders is estimated to cover about 10 % of the area and is mainly found in the shallow areas where it is the dominating substrate type above 10 meters water depth in wave exposed regions. Elevated concentrations of harmful substances, such as cadmium (Cd), lead (Pb), zinc (Zn) and mercury (Hg) were recorded in the seabed sediments. Regarding the new seabed maps created in this project, where both manual and modelling methods have been tested, it was found that they all provide valuable information and aspects of the seabed environment. Fine scale substrate models and the thematic interpreted substrate maps show similar patterns, however the substrate models capture much variations within the thematic classes as well as soft transitions, indicating that even very detailed thematic maps (1:25000) are still significant simplifications of the true seascape complexity in many areas. Data and information