Browsing by Subject "δ15N"

The present retreat of the Greenland Ice Sheet will increase the amount of fjords surrounded only by land-terminating glaciers in the future. As in the Arctic, productivity is generally lower at these kinds of fjord systems than in the ones surrounded by marine-terminating glaciers, this will most likely affect the productivity and ecosystem structure of coastal marine areas. Paleorecords of past coastal ecosystems can improve our understanding of the drivers of Arctic coastal ecosystem change and provide possible future scenarios. At present, there are not many high-resolution marine ecosystem reconstructions from the Arctic near-shore areas, and in particular those, which take into account land-derived inputs are lacking. To provide a detailed reconstruction of coastal marine ecosystem change over the Holocene and study its linkages to climate and terrestrial freshwater inputs, organic-walled palynomorphs (including e.g. dinoflagellate cysts and pollen) and some basic geochemistry (including e.g. total organic carbon, C:N ratio, biogenic silica and stable isotopes of carbon and nitrogen) were examined from two radiometrically dated sediment cores from Young Sound fjord, Northeast Greenland. The results indicate that the near-shore marine ecosystem in Young Sound is clearly influenced by local forcings, such as terrestrial freshwater and organic matter inputs, during the Holocene. The results also illustrate that these terrestrial inputs affect the ecosystem structure and at least some dimension of ecosystem productivity. This study demonstrates that increasing number of fjords with only land-terminating glaciers in the future will affect marine productivity and ecosystem structure in Greenland’s fjord systems, with potential impacts on biodiversity and important fisheries. Studying past ecosystem changes in different fjord systems, and complementing marine records with proxies for terrestrial inputs, would further help constrain the future scenarios along the Greenland shore.

Global warming and anthropogenic activity will change the environmental conditions in the northern regions. For example, precipitation and river flow are expected to increase, the amount of organic matter ending up in the sea from land will increase, and its quality will change. The impact of changes in organic matter on northern coastal ecosystems and the carbon cycle is poorly known and these impacts need to be studied. In this study, the amount, quality and variations of organic matter accumulated in the surface sediments of the Bothnian Bay coastal areas in the northern part of the Baltic Sea and in the Liminka Bay over the past 100 years are studied by analyzing the concentrations of organic carbon and nitrogen (TOC and TN), C/N ratio, and the stable isotope ratios δ13C and δ15N, thus assessing environmental change in the coastal area of the Bothnian Sea. The accumulation of organic matter along the coast of Bothnian Bay is affected by both the proximity of the rivers and the land cover and land use of the river basin. More organic matter accumulates on the coasts (average 3.5 wt%) than further into the open sea (average 1.9 wt%). Contrary to presuppositions, there is no clear variation in the quality of organic matter between the coast and the open sea, but the observed change is north-south: in the northern areas, organic matter is more terrestrial and autochthonous, and in the southern areas it is more aquatic and allochthonous. The northern regions are characterized by large rivers with large amounts of forests and peatlands in the catchment areas. Further south, the rivers are smaller and carry less organic matter in quantity. Further north in the coastal ecosystem, the amount of primary production is lower and nitrogen does not limit primary production, as opposed to more southern areas. Primary production of ice may also have affected the organic matter deposited in the Bothnian Sea sediments. The amount of organic matter deposited in Liminka Bay has been on the rise over the past century, probably due to global warming, increased river flow and the impact of human activity. Based on the C/N ratio, the material has been more terrestrial in the 1930s to 1970s, after which the material has become more aquatic. In addition, aquatic primary production has increased in the Liminka Bay and nitrogen has begun to restrict primary production more. The study shows that climate and environmental change and human activities affect the amount and quality of organic matter in northern coastal areas, but further research is needed to determine more accurate ecosystem impacts.