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Maren Moltke Lyngsgaard Stiig Markager Katherine Richardson Eva Friis Møller Hans Henrik Jakobsen 《Estuaries and Coasts》2017,40(5):1263-1275
The seasonal variation in phytoplankton activity is determined by analysing 1385 primary production (PP) profiles, chlorophyll a (Chl) concentration profiles and phytoplankton carbon biomass concentrations (C) from the period 1998–2012. The data was collected at six different stations in the Baltic Sea transition zone (BSTZ) which is a location with strong seasonal production patterns with light as the key parameter controlling this productivity. We show that the use of Chl as a proxy for phytoplankton activity strongly overestimates the contribution from the spring production to annual pelagic carbon flow. Spring (February and March) Chl comprised 16–30% of the total annual Chl produced, whereas spring C was much lower (8–23%) compared to the annual C. Spring PP accounted for 10–18% of the total annual PP, while the July–August production contributed 26–33%, i.e. within the time frame when zooplankton biomass and grazing pressure are highest. That is, Chl failed in this study to reflect the importance of the high summer PP. A better proxy for biomass may be C, which correlated well with the seasonal pattern of PP (Pearson correlation, p < 0.05). Thus, this study suggests to account for the strong seasonal pattern in C/Chl ratios when considering carbon flow in coastal systems. Seasonal data for PP were fitted to a simple sinusoidal wave model describing the seasonal distribution of PP in the BSTZ and were proposed to present a better parameterizaton of PP in shallow stratified temperate regions than more commonly applied proxies. 相似文献
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Dissolved organic matter (DOM) export to a temperate estuary: seasonal variations and implications of land use 总被引：1，自引：0，他引：1
Colin A. Stedmon Stiig Markager Morten Søndergaard Torben Vang Anker Laubel Niels Henrik Borch Anders Windelin 《Estuaries and Coasts》2006,29(3):388-400
Inputs of dissolved carbon, nitrogen, and phosphorus were assessed for an estuary and its catchment (Horsens, Denmark). Seasonal
patterns in the concentrations of DOM in the freshwater supply to the estuary differed depending on the soil and drainage
characteristics of the area. In streams draining more natural areas the, patterns observed were largely driven by seasonal
temperature fluctuations. The material exported from agricultural areas was more variable and largely controlled by precipitation
events. Positive exponential relationships were found between the nitrogen and phosphorus loading, and the percentage of catchment
area used for agriculture. Colored DOM (CDOM) loading measurements were found to be a good predictor of dissolved organic
carbon (DOC) loading across the different subcatchments, offering a rapid and inexpensive alternative of operationally monitoring
DOC export. For all the dissolved nutrient inputs to the estuary, dissolved inorganic nitrogen (DIN) and dissolved organic
phosphorus dominated the loadings. Although 81% of the nitrogen annually supplied to the estuary was DIN, 83% of the nitrogen
exported from the estuary was dissolved organic nitrogen (DON). Results show that increasing the area of the catchment covered
by forest and natural pastures would have a positive effect on the trophic status of the estuary, leading to a considerable
decrease in the phosphorus loading and a shift in the nitrogen loading from DIN to DON. Such a change in land use would also
increase the export of DOC and CDOM to the estuary having the potential to increase oxygen consumption and reduce the photic
depth. 相似文献
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Troels Møller Pedersen Kaj Sand-Jensen Stiig Markager Søren Laurentius Nielsen 《Estuaries and Coasts》2014,37(4):880-892
Loss of water clarity is one of the consequences of coastal eutrophication. Efforts have therefore been made to reduce external nutrient loadings of coastal waters. This paper documents improvements to water clarity between 1985 and 2008–2009 at four stations in the microtidal estuary Roskilde Fjord and find significant relationships to freshwater nutrient loadings. The paper then investigates to which extent changes in phytoplankton biomass (chlorophyll a (Chl a)), non-algal particulate organic matter (POM*), and residual attenuation in the water (K b), respectively, can account for this optical improvement. Vertical light attenuation (K d) declined, on average, by 34 %, accompanying a 71 % reduction of Chl a and an 80 % reduction of POM*. Residual attenuation declined by 26 % over the period in accordance with a measured 34 % decline of dissolved organic nitrogen. Analysis of simultaneous changes in light attenuation and Secchi depth also suggested a reduction of the scatter-to-absorption ratio over time. Considering the stronger reductions of particle concentrations than dissolved organic matter, the contribution of residual attenuation to vertical attenuation increased from 54 to 74 % in 1985 to 78 to 85 % in 2008–2009. Overall, efforts to reduce nutrient loading and improve water clarity appeared to have had a larger impact on POM* than on Chl a and colored dissolved organic matter concentrations in the estuary, which can account for the decrease in the scatter-to-absorption ratio. These optical changes lead to larger improvements of Secchi depth than of vertical light attenuation. The consequence of this is an overestimation (0.45–1.48 m) of the predicted increase of potential seagrass depth limits when based on Secchi depth rather than K d. 相似文献
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Benthic flora can contribute significantly to gross primary production (GPP) of shallow coastal waters where light reaches
the sea bottom. We quantified and compared benthic and pelagic GPP along nutrient gradients in time and space in the shallow
estuary, Limfjorden, Denmark, based on monitoring data combined with historical information. Limfjorden experienced a shift
from a pristine, benthic-dominated clear water regime with high total GPP in the early twentieth century to a eutrophic, plankton-dominated
regime still with high total GPP in the 1980s when nutrient loadings peaked. Recent reductions in nutrient loadings reduced
pelagic GPP, particularly in spring, but water clarity and benthic GPP did not increase correspondingly, so total GPP declined.
The most nutrient-rich basins have remained plankton-dominated, with benthic vegetation constrained to shallow waters. The
results support existing evidence that total GPP of shallow coastal areas does not increase systematically with eutrophication.
Furthermore, the results suggest that total GPP may decline temporarily during oligotrophication as pelagic GPP declines,
while feedback mechanisms delay or prevent restoration to a state with benthic dominance of GPP. 相似文献
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Daniel J. Conley Stiig Markager Jesper Andersen Thomas Ellermann Lars M. Svendsen 《Estuaries and Coasts》2002,25(4):848-861
Nutrient over-enrichment and cultural eutrophication are significant problems in the Danish marine environment. Symptoms of eutrophication include periods of hypoxia and anoxia in bottom waters, death of benthic-dwelling organisms during anoxia, long-term reductions in the depth distribution of macrophyte communities, changes in the species composition of macrophyte communities, and increases in reports of harmful algal blooms. In 1987 the Action Plan on the Aquatic Environment was adopted to combat nutrient pollution of the aquatic environment with the overall goal of reducing nitrogen loads by 50% and point source phosphorus loads by 80%. The Danish Aquatic Nation-wide Monitoring Program was begun in 1988 in order to describe the status of point sources (industry, sewage treatment plants, stormwater outfalls, scattered dwellings, and fish farms), ground water, springs, agricultural watersheds, streams, lakes, atmospheric deposition, and the marine environment. Another important aspect of the program was to document the effects on the aquatic environment of the measures and investments taken for nutrient reduction as outlined in the Action Plan. The monitoring program should determine if reductions in nutrients are achieved by the measures taken and should help decision makers choose appropriate additional measures to fulfill the objectives. Coordination with international programs and commissions is an important component of the monitoring program to meet internationally agreed upon reductions in nutrient inputs. The future and direction of the Danish National Aquatic Monitoring and Assessment Program will be to a large extent shaped by both the Water Framework Directive and Habitat Directive adopted by the European Union. 相似文献
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Tracing dissolved organic matter in aquatic environments using a new approach to fluorescence spectroscopy 总被引：34，自引：0，他引：34
Dissolved organic matter (DOM) is a complex and poorly understood mixture of organic polymers that plays an influential role in aquatic ecosystems. In this study we have successfully characterised the fluorescent fraction of DOM in the catchment of a Danish estuary using fluorescence excitation–emission spectroscopy and parallel factor analysis (PARAFAC). PARAFAC aids the characterisation of fluorescent DOM by decomposing the fluorescence matrices into different independent fluorescent components. The results reveal that at least five different fluorescent DOM fractions present (in significant amounts) in the catchment and that the relative composition is dependent on the source (e.g. agricultural runoff, forest soil, aquatic production). Four different allochthonous fluorescent groups and one autochthonous fluorescent group were identified. The ability to trace the different fractions of the DOM pool using this relatively cheap and fast technique represents a significant advance within the fields of aquatic ecology and chemistry, and will prove to be useful for catchment management. 相似文献
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Behaviour of the optical properties of coloured dissolved organic matter under conservative mixing 总被引：3，自引：0，他引：3
The optical properties of coloured dissolved organic matter (CDOM) can be used, in some environments, to trace water masses and provide information about the dynamics of the dissolved organic fraction in natural waters. This work presents the results from a modelling exercise, laboratory experiment and field data, which describe the variations in the optical properties of CDOM during mixing. The exponential slope coefficient (S) is frequently used to characterise different CDOM pools; however, its behaviour during conservative mixing of two different CDOM types is often misunderstood. Identification of a theoretical conservative mixing line allows the rapid identification of non-conservative processes (e.g. in situ production, flocculation and degradation) acting on the pool during mixing. The results suggest that some of the patterns reported in the literature could purely be a result of conservative mixing rather than a product of non-conservative processes. 相似文献
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Photochemical production of ammonium and transformation of dissolved organic matter in the Baltic Sea 总被引：13，自引：1，他引：13
Colin A. Stedmon Stiig Markager Lars Tranvik Leif Kronberg Tove Sltis Winnie Martinsen 《Marine Chemistry》2007,104(3-4):227-240
The release of ammonium from the photochemical degradation of dissolved organic matter (DOM) has been proposed by earlier studies as a potentially important remineralisation pathway for refractory organic nitrogen. In this study the photochemical production of ammonium from Baltic Sea DOM was assessed in the laboratory. Filtered samples from the Bothnian Bay, the Gulf of Finland and the Arkona Sea were exposed to UVA light at environmentally relevant levels, and the developments in ammonium concentrations, light absorption, fluorescence and molecular size distribution were followed. The exposures resulted in a decrease in DOM absorption and loss of the larger sized fraction of DOM. Analysis of the fluorescence properties of DOM using parallel factor analysis (PARAFAC) identified 6 independent components. Five components decreased in intensity as a result of the UVA exposures. One component was produced as a result of the exposures and represents labile photoproducts derived from terrestrial DOM. The characteristics of DOM in samples from the Bothnian Bay and Gulf of Finland were similar and dominated by terrestrially derived material. The DOM from the Arkona Sea was more autochthonous in character. Photoammonification differed depending on the composition of DOM. Calculated photoammonification rates in surface waters varied between 121 and 382 μmol NH4+ L− 1 d− 1. Estimated areal daily production rates ranged between 37 and 237 μmol NH4+ m− 2 d− 1, which are comparable to atmospheric deposition rates and suggest that photochemical remineralisation of organic nitrogen may be a significant source of bioavailable nitrogen to surface waters during summer months with high irradiance and low inorganic nitrogen concentrations. 相似文献
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