Quantifying seabed geodiversity of the Archipelago Sea, Baltic Sea, Finland

This study investigated the geodiversity of the Archipelago Sea in the northern Baltic Sea, focusing on geological features and their spatial distribution. By adapting methods used in previous Baltic Sea studies, we conducted spatial analyses of geological data sets including bedrock type, seabed substrates and seabed structures. Bedrock and substrate data were freely available, while seabed structures were modelled from bathymetry data. Geodiversity was quantified using a geodiversity index, which considers the variety of physical elements, roughness and area of the unit. The analyses revealed a diverse seabed environment in the Archipelago Sea with varying geodiversity throughout the study area. Significant features contributing to geodiversity included bedrock fracture and fault zones and large end-moraine formations. Similar patterns have been observed in terrestrial areas of Finland. The analyses also detected relations between archipelago zonation and geodiversity with areas of open sea more homogeneous than the middle and inner archipelago. This study formally recognises the complexity of the seabed in the Archipelago Sea and highlights the importance of understanding the geological processes shaping the region. The results can inform maritime spatial planning and sustainable resource management

A study of the stable carbon and oxygen isotope composition of recent shells of Mytilidae, especially of oxygen values in relation to temperature

Peer reviewe

Sediment Bacterial Communities Reflect the History of a Sea Basin

Peer reviewe

Extensive Coverage of Marine Mineral Concretions Revealed in Shallow Shelf Sea Areas

Ferromanganese (FeMn) concretions are mineral precipitates found on soft sediment seafloors both in the deep sea and coastal sea areas. These mineral deposits potentially form a three-dimensional habitat for marine organisms, and contain minerals targeted by an emerging seabed mining industry. While FeMn concretions are known to occur abundantly in coastal sea areas, specific information on their spatial distribution and significance for marine ecosystems is lacking. Here, we examine the distribution of FeMn concretions in Finnish marine areas. Drawing on an extensive dataset of 140,000 sites visited by the Finnish Inventory Programme for the Underwater Marine Environment (VELMU), we examine the occurrence of FeMn concretions from seabed mapping, and use spatial modeling techniques to estimate the potential coverage of FeMn concretions. Using seafloor characteristics and hydrographical conditions as predictor variables, we demonstrate that the extent of seafloors covered by concretions in the northern Baltic Sea is larger than anticipated, as concretions were found at similar to 7000 sites, and were projected to occur on over 11% of the Finnish sea areas. These results provide new insights into seafloor complexity in coastal sea areas, and further enable examining the ecological role and resource potential of seabed mineral concretions.Peer reviewe

Flocculation of dissolved organic matter controls the distribution of iron in boreal estuarine sediments

Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM). However, the fate of this Fe pool in estuarine sediments has not been extensively studied. Here we show that flocculation of DOM along salinity gradients in an estuary of the northern Baltic Sea efficiently transfers Fe from the dissolved phase into particulate material that accumulates in the sediments. Consequently, we observe a decline with distance offshore in both the Fe content of the sediments and proportion of terrestrial material in the sedimentary organic matter pool. Mössbauer spectroscopy and sequential extractions suggest that large amounts of Fe in sediments of the upper estuarine zone are associated with organic matter as unsulfidized Fe (II) complexes, or present in the form of ferrihydrite, implying a direct transfer of flocculated material to the sediments. Accordingly, the contribution of these components to the total sedimentary Fe declines with distance offshore while other Fe phases become proportionally more important. Sediment core records show that the observed lateral distribution of Fe minerals has remained similar over recent decades, despite variable Fe inputs from anthropogenic sources and eutrophication of the coastal zone. Pore water data suggest that the vertical zonation of diagenetic processes in the sediments is influenced by both the availability of Fe and by bottom water salinity, which controls the availability of sulfate (SO42−).Output Type: Discussion Pape

Impacts of flocculation on the distribution and diagenesis of iron in boreal estuarine sediments

Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM) and as colloidal Fe oxyhydroxides, principally ferrihydrite. However, the fate of this Fe pool in estuarine sediments has not been extensively studied. Here we show that flocculation processes along a salinity gradient in an estuary of the northern Baltic Sea efficiently transfer Fe and OM from the dissolved phase into particulate material that accumulates in the sediments. Flocculation of Fe and OM is partially decoupled. This is likely due to the presence of discrete colloidal ferrihydrite in the freshwater Fe pool, which responds differently from DOM to estuarine mixing. Further decoupling of Fe from OM occurs during sedimentation. While we observe a clear decline with distance offshore in the proportion of terrestrial material in the sedimentary particulate organic matter (POM) pool, the distribution of flocculated Fe in sediments is modulated by focusing effects. Labile Fe phases are most abundant at a deep site in the inner basin of the estuary, consistent with input from flocculation and subsequent focusing. The majority of the labile Fe pool is present as Fe (II), including both acid-volatile sulfur (AVS)-bound Fe and unsulfidized phases. The ubiquitous presence of unsulfidized Fe (II) throughout the sediment column suggests Fe (II)-OM complexes derived from reduction of flocculated Fe (III)-OM, while other Fe (II) phases are likely derived from the reduction of flocculated ferrihydrite. Depth-integrated rates of Fe (II) accumulation (AVS-Fe + unsulfidized Fe (II) + pyrite) for the period 1970-2015 are greater in the inner basin of the estuary with respect to a site further offshore, confirming higher rates of Fe reduction in near-shore areas. Mossbauer Fe-57 spectroscopy shows that refractory Fe is composed largely of superparamagnetic Fe (III), high-spin Fe (II) in silicates, and, at one station, also oxide minerals derived from past industrial activities. Our results highlight that the cycling of Fe in boreal estuarine environments is complex, and that the partial decoupling of Fe from OM during flocculation and sedimentation is key to understanding the role of Fe in sedimentary diagenetic processes in coastal areas.Peer reviewe

Discovering Europe's seabed geology: the EMODnet concept of uniform collection and harmonization of marine data

Maritime spatial planning, management of marine resources, environmental assessments and forecasting all require good seabed maps. Similarly there is a need to support the objectives to achieve Good Environmental Status in Europe's seas by 2020, set up by the European Commission's Marine Strategy Framework Directive. Hence the European Commission established the European Marine Observation and Data Network (EMODnet) programme in 2009, which is now in its fourth phase (2019–21). The programme is designed to assemble existing, but fragmented and partly inaccessible, marine data and to create contiguous and publicly available information layers which are interoperable and free of restrictions on use, and which encompass whole marine basins. The EMODnet Geology project is delivering integrated geological map products that include seabed substrates, sedimentation rates, seafloor geology, Quaternary geology, geomorphology, coastal behaviour, geological events such as submarine landslides and earthquakes, and marine mineral occurrences. Additionally, as a new product during the ongoing and preceding phase of the project, map products on submerged landscapes of the European continental shelf have been compiled at various time frames. All new map products have a resolution of 1:100 000, although finer resolution is presented where the underlying data permit. A multi-scale approach is adopted whenever possible. Numerous national seabed mapping programmes worldwide have demonstrated the necessity for proper knowledge of the seafloor. Acting on this, the European Commission established the European Marine Observation and Data Network (EMODnet) programme in 2009. The national geological survey organizations of Europe have a strong network of marine geological teams through the Marine Geology Expert Group of the association of European geological surveys (Eurogeosurveys). This network was the foundation of the EMODnet Geology consortium which today consists of the national geological surveys of Finland, the UK, Sweden, Norway, Denmark, Estonia, Latvia, Lithuania, Poland, The Netherlands, Belgium, France, Ireland, Spain, Italy, Slovenia, Croatia, Albania, Greece, Cyprus, Malta, Russia, Germany, Montenegro and Iceland, as well as marine teams of research organizations in Portugal (IPMA), Bulgaria (IO-BAS), Romania (GeoEcoMar), the UK (CEFAS), Greece (HCMR) and Ukraine (PSRGE, replaced in the fourth phase by Institute of Geological Sciences, NAS of Ukraine). The consortium is further strengthened with experts from six universities: Edge Hill University (UK), Sapienza University of Rome (Italy), University of Tartu (Estonia), University of Crete through FORTH-ICS, Institute of Marine Science and Technology of Dokuz Eylul University (Turkey), and EMCOL Research Centre of Istanbul Technical University – altogether, 30 partners and nine subcontractors. The EMODnet Geology programme is now in its fourth phase, which started in September 2019. In addition to geological information, the wider EMODnet programme aims to also bring together information from European seas on seabed habitats, physical properties, chemistry, biology, human activities and hydrography. This paper describes the EMODnet Geology project and the different end products which were delivered in the end of the third phase and will be further developed during the recent fourth phase of the project

Threatened habitat types in Finland 2018: the Baltic Sea. Red List of habitats. Part 2: Descriptions of habitat types

This report is a partial translation of the final report in Finnish on threatened habitat types (Threatened habitat types in Finland 2018, Part II: Descriptions of habitat types, The Finnish Environment 5/2018) that presents a total of 420 habitat types. This report includes all the evaluated habitat types of the Baltic Sea, as well as six new marine habitat types, which were described but not yet evaluated (NE). Also included are habitat types regarded as of least concern (LC) and those with deficient data (DD). For each habitat type a description, distribution map, photo, and the reasoning behind the assessment result are presented. The descriptions of the habitat types include their characteristics, geographical variation, connectivity to other habitat types, occurrence in Finland, reasons for being threatened and future threats, trend in the state of the habitat type, correspondence of the habitats type with habitat types covered by statutory protection, and whether the habitat type is one for which Finland has an international responsibility. Part I of the final report (in Finnish Suomen luontotyyppien uhanalaisuus 2018, SY 5/2018 and in English Threatened Habitat Types in Finland 2018, FE 2/2019) presents the assessment method for threatened habitat types, results and reasoning of the assessment, and proposals for measures prepared by the experts groups. In the whole country 186 habitats types were assessed as threatened (48% of the number of habitats types). The share of threatened habitat types is much larger in southern Finland (59%) than in northern Finland (32%). The assessment was conducted by broadly-based expert groups in 2016–2018. This was the second assessment of threatened habitat types in Finland. This assessment was conducted using the international IUCN Red List of Ecosystems method. Because of the new assessment method, the results of the first and second assessment of threatened habitat types are not directly comparable with each other. The conclusion that can be made, however, is that the decline and degradation of habitats has not diminished

Giant saltwater inflow in AD 1951 triggered Baltic Sea hypoxia

A marked sedimentological change in subsurface sediments from the entire Baltic Proper, the Baltic Sea, has been previously noted. Our detailed work on a variety of multi-cores from basin-wide transects indicates that this sedimentological change was caused by a large shift in environmental conditions during the 1950s. Until the 1950s, the water column was rather weakly stratified and winter-time convection – although weakened during the post Little Ice Age warming – was still able to ventilate the bottom waters of the Baltic Proper. Therefore, complete sediment sequences only accumulated in calm waters deeper than 150–160 m. High-resolution benthic foraminiferal records of subsurface sediments obtained along the saline water inflow pathway in combination with historical data indicate that the depositional environment changed drastically owing to the giant saline water inflow in AD 1951. The accompanied sharpening of the halo(pycno)cline triggered a collapse in the ventilation of the basin, resulting in oxygen-deficient bottom waters. This deficiency, in turn, caused the onset of phosphate release from the sediments, which accelerated primary production. The ventilation collapse also enabled the onset of deposition of organic carbon-rich sediments also in shallower water areas as calm conditions prevailed up to the modern winter mixing depth (60–70 m). A slight return to Little Ice Age-type conditions was observed during the late 1980s when temperatures decreased and stratification weakened. These conditions gave rise to a reduction in hypoxic areas and to a bottom-water ventilation, most pronounced in the north of the so-called Baltic Sea Klint, a hydrographic and topographic barrier. However, the general environmental conditions essentially have not changed since the 1950s. Remarkably, external (temperature and stratification) in combination with internal factors (e.g. ventilation collapse and phosphate release) were able to change the redox conditions of the Baltic Proper from oxic to hypoxic within less than 10 years