Sami Jokinen

Geological Survey of Finland | GTK · Marine Geology

Sedimentary molybdenum (Mo) and uranium (U) enrichments are often used as redox proxies to reconstruct bottom water redox changes. However, these redox proxies may not be equally reliable across a range of coastal settings due to varying depositional environments. Fjords vary greatly in their depositional conditions, due to their unique bathymetry...

Sedimentary molybdenum (Mo) and uranium (U) enrichments are widely used to reconstruct changes in bottom water oxygen conditions in aquatic environments. Until now, most studies using Mo and U have focused on restricted suboxic-euxinic basins and continental margin oxygen minimum zones (OMZs), leaving mildly reducing and oxic (but eutrophic) coasta...

We report observations of vateritic crystallization in the sagittal otoliths of the Baltic herring Clupea harengus membras in the northern Baltic Sea. While the existence of vaterite in the calcium carbonate matrix of sagittal otoliths has been observed in various species globally, reports from the brackish Baltic Sea are few in number. Large varia...

Coastal regions globally have experienced widespread anthropogenic eutrophication in recent decades. Loading of autochthonous carbon to coastal sediments enhances the demand for electron acceptors for microbial remineralization, often leading to rearrangement of the sediment diagenetic zonation and potentially enhancing fluxes of methane and hydrog...

Using biogeochemical analyses of sediments and porewaters, we investigate the legacy of a brief, intense period of eutrophication on sedimentary phosphorus (P) cycling in a boreal lake (Enonselkä basin, Lake Vesijärvi, Finland). Point-source sewage inputs in the 20th century caused deoxygenation of the lake and accelerated the focusing of iron (Fe)...

Molybdenum (Mo) and uranium (U) contents in sedimentary archives are often used to reconstruct past changes in seafloor oxygenation. However, their sequestration processes are as yet poorly constrained in low-salinity coastal waters, which often suffer from anthropogenic eutrophication but only mild oxygen depletion. Due to the consequent lack of r...

Coastal sediments play a fundamental role in processing anthropogenic trace metal inputs. Previous studies have shown that terrestrialorganic matter (OM) is a significant vector for trace metal transport across the land-to-sea continuum, but little is known about the fate of land-derived metal-OM complexes in coastal sediments. Here, we use a compr...

The Iisalmi Route watercourse in central-eastern Finland contains a number of highly eutrophic lakes. Despite substantial impacts from anthropogenic activity, the region appears to be naturally eutrophic because of its geological setting. A passive continental ice sheet deposited fine-grained basal till that contributes to the naturally eutrophic s...

The anthropogenically forced expansion of coastal hypoxia is a major environmental problem affecting coastal ecosystems and biogeochemical cycles throughout the world. The Baltic Sea is a semi-enclosed shelf sea whose central deep basins have been highly prone to deoxygenation during its Holocene history, as shown previously by numerous paleoenviro...

The anthropogenically forced expansion of coastal hypoxia is a major environmental problem affecting coastal ecosystems and biogeochemical cycles throughout the world. The Baltic Sea is a semi-enclosed shelf sea whose central deep basins have been highly prone to deoxygenation during its Holocene history, as shown previously by numerous paleoenviro...

Many modern epicontinental seas were dry land before their marine flooding by the mid-Holocene glacioeustatic sea-level rise, whereas the Baltic Sea Basin was covered by a huge postglacial lake. This change from a postglacial lake to the present-day semi-enclosed brackish-water sea is studied here in sediment cores and acoustic profiles from the Ba...

Human-induced spreading of coastal hypoxia is currently a growing global problem that has deleterious effects on marine ecosystems. Although long-term spatio-temporal trends in hypoxia in the offshore areas of the Baltic Sea have been widely studied, coastal areas have received less research interest so far. In addition, the conventional environmen...

Eutrophication-induced hypoxia has resulted in preservation of laminated sedimentary fabric in coastal areas of the northern Baltic Sea. These laminites offer a potential technique for dating recently deposited organic-rich muds, but their formation mechanisms have been inadequately understood. In this study, microfabric of the modern laminated sed...

Puolustusvoimat vetäytyy Örön linnakesaarelta vuoden 2014 lopulla, jonka jälkeen saaren hallinnointi on siirtymässä Metsähallitukselle. Metsähallitus suunnittelee saaresta merkittävää virkistyskäyttökohdetta osana Saaristomeren kansallispuiston palveluita. Virkistyskäyttö edellyttää Örön satama-alueella ruoppaustoimia, joiden mahdollisia ympäristöv...

Puolustusvoimat vetäytyy Örön linnakesaarelta vuoden 2014 lopulla, jonka jälkeen saaren hallinnointi on siirtymässä Metsähallitukselle. Metsähallitus suunnittelee saaresta merkittävää virkistyskäyttökohdetta osana Saaristomeren kansallispuiston palveluita. Oletettavasti lisääntyvä matkailijavirta edellyttää toimia Örön sataman nykyiseen infrastruk...