| 1. |
- Tett, P, et al.
(author)
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Eutrophication and some European waters of restricted exchange
- 2003
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In: Continental Shelf Research. - : Elsevier BV. - 0278-4343. ; 23:17-19, s. 1635-1671
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Journal article (peer-reviewed)abstract
- Regions of Restricted Exchange (RREs) are an important feature of the European coastline. They are historically preferred sites for human settlement and aquaculture and their ecosystems, and consequent human use, may be at risk from eutrophication. The OAERRE project (EVK3-CT1999-0002) concerns ‘Oceanographic Applications to Eutrophication in Regions of Restricted Exchange’. It began in July 2000, and studies six sites. Four of these sites are fjords: Kongsfjorden (west coast of Spitzbergen); Gullmaren (Skagerrak coast of Sweden); Himmerfjärden (Baltic coast of Sweden); and the Firth of Clyde (west coast of Scotland). Two are bays sheltered by sand bars: Golfe de Fos (French Mediterranean); and Ria Formosa (Portuguese Algarve). Together they exemplify a range of hydrographic and enrichment conditions. The project aims to understand the physical, biogeochemical and biological processes, and their interactions, that determine the trophic status of these coastal marine RRE through the development of simple screening models to define, predict and assess eutrophication. This paper introduces the sites and describes the component parts of a basic screening model and its application to each site using historical data. The model forms the starting point for the OAERRE project and views an RRE as a well-mixed box, exchanging with the sea at a daily rate E determined by physical processes, and converting nutrient to phytoplankton chlorophyll at a fixed yield q. It thus uses nutrient levels to estimate maximum biomass; these preliminary results are discussed in relation to objective criteria used to assess trophic status. The influence of factors such as grazing and vertical mixing on key parameters in the screening model are further studied using simulations of a complex ‘research’ model for the Firth of Clyde. The future development of screening models in general and within OAERRE in particular is discussed. In addition, the paper looks ahead with a broad discussion of progress in the scientific understanding of eutrophication and the legal and socio-economic issues that need to be taken into account in managing the trophic status of RREs.
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| 2. |
- Arneborg, Lars, 1969, et al.
(author)
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The rate of inflow and mixing during deep-water renewal in a sill fjord
- 2004
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In: Limnology and Oceanography. - 0024-3590. ; 49:3, s. 768-777
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Journal article (peer-reviewed)abstract
- We obtained high-resolution data on a deep-water renewal in the basin of Gullmar Fjord, Sweden, using an autonomous profiling platform. In the middle of the fjord, where the platform is anchored, renewal starts with the passage of a gravity current front and continues with a steady thickening of the new, oxygen-rich, low-nitrate bottom layer and an associated lifting of the old, oxygen-depleted, high-nitrate bottom water. The basin continuously fills to sill level during a period of 10 d. At the mouth of the fjord, a three-layer structure develops. Renewal is driven by the density difference between the intermediate water inside and the new deep water outside the fjord. The volume flux is well predicted by a hydraulic exchange model in which the upper layer plays a passive role. Local upwelling and downwelling of the upper halocline cause fluctuating baroclinic currents during renewal, but these seem to have little influence on the average volume flux of new deep water. Entrainment rates are small, and the associated volume flux increase seems to be balanced by detrainment.
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| 3. |
- Erlandsson, Carina P., et al.
(author)
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Finn de områden som göder havet mest - och de som är mest känsliga för övergödning
- 2009
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Reports (other academic/artistic)abstract
- Det är viktigt att konstatera att effekterna av övergödning är olika i innerskärgården och i öppna havet och måste också diskuteras utifrån detta faktum. Effekterna av åtgärder mot övergödning på framförallt kustvattenförekomst och vikskala är i högsta grad beroende på vattenomsättningen, d.v.s. systemets förmåga att göra sig av med lokalt tillförd näring (känslighet). Vid åtgärder är det därför viktigt att identifiera om området är känsligt eller okänsligt för övergödning.
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| 4. |
- Erlandsson, Carina P., et al.
(author)
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Increased utility of the Secchi disk to assess eutrophication in coastal waters with freshwater run-off
- 2006
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In: Journal of Marine Systems. - : Elsevier BV. - 0924-7963. ; 60:1-2, s. 19-29
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Journal article (peer-reviewed)abstract
- Changed local Supply of nutrients in coastal waters can lead to changed content of phytoplankton. This influences the visibility, and thereby the water quality in the surface layers, which can be observed by e.g., the Secchi disk. However, the translation of Secchi depth observations to plankton content is complicated by the existence of light attenuating matter entering with run-off from land. To increase the utility of Secchi depth measurements to assess local eutrophication in coastal waters, a formula for calculating the Secchi depth in areas influenced by freshwater was developed. The study includes data analysis of Seechi depth, chlorophyll content, wind speed, and freshwater height estimated from salinity at two stations in the Gullmar Fjord in Sweden. The correlation coefficient between calculated and observed Secchi depths at the inner station close to the freshwater source increased from 0.63 using chlorophyll as the only dependent parameter, to 0.75 (p < 0.001) including the accumulated freshwater in the surface layer from run off, and wind speed. At the outer station close to the mouth of the fjord it increased from 0.68 to 0.70 (p < 0.001) The correlation between observed and calculated Secchi depth decreased considerably, if the restriction to observations made at sun elevations higher than about 30 degrees above the horizon was relaxed. (c) 2005 Elsevier B.V. All rights reserved.
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| 5. |
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| 6. |
- Erlandsson, Carina P., et al.
(author)
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The sensitivity of minimum oxygen concentrations in a fjord to changes in biotic and abiotic external forcing
- 2006
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In: Limnology and Oceanography. - 0024-3590. ; 51:1, part 2, s. 631-638
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Journal article (peer-reviewed)abstract
- We investigated the possible biotic and abiotic causes of the observed long-term decrease of oxygen minimum concentrations in the deep water of Gullmar Fjord. Physical factors explained about 40% of the decreased minimum oxygen concentrations since the 1950s. The North Atlantic Oscillation and more regional climate variations account for an important part of this change. The effect of the climate variations was mainly on the timing of the renewal of the basin water. The consumption rate of oxygen in the basin water has increased by 50% since the 1950s. This biotic effect explained about 60% of the decrease in minimum oxygen concentrations. The likely dominating source of oxygen-consuming matter was (remote) production in the Skagerrak, suggesting that there has been a long-term increase of particulate organic carbon in the Skagerrak water.
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