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21.
Marieke A. Eleveld Reinold Pasterkamp Hendrik J. van der Woerd Julie D. Pietrzak 《Estuarine, Coastal and Shelf Science》2008
An algorithm is presented for estimating near-surface SPM concentrations in the turbid Case 2 waters of the southern North Sea. The single band algorithm, named POWERS, was derived by parameterising Gordon's approximation of the radiative transfer model with measurements of Belgian and Dutch inherent optical properties. The algorithm was used to calculate near-surface SPM concentration from 491 SeaWiFS datasets for 2001. It was shown to be a robust algorithm for estimating SPM in the southern North Sea. Regression of annual geometric mean SPM concentration derived from remote sensing (SPMrs), against in situ (SPMis) data from 19 Dutch monitoring stations was highly significant with an r2 of 0.87. Further comparison and statistical testing against independent datasets for 2000 confirmed the consistency of this relationship. Moreover, time series of SPMrs concentrations derived from the POWERS algorithm, were shown to follow the same temporal trends as individual SPMis data recorded during 2001. Composites of annual, winter and summer SPMrs for 2001 highlight the three dominant water masses in the southern North Sea, as well as their winter–fall and spring–summer variability. The results indicate that wind induced wave action and mixing cause high surface SPM signals in winter in regions where the water column becomes well mixed, whereas in summer stratification leads to a lower SPM surface signal. The presented algorithm gives accurate near-surface SPM concentrations and could easily be adapted for other water masses and seas. 相似文献
22.
Five stations along a transect from the western shore of Biscayne Bay, Florida to the Florida Current were sampled monthly for one year. The variability and amount of seston particulate organic carbon, adenosine triphosphate, chlorophyll a, primary production and zooplankton decreased along the seaward transect. The greater inshore biomass and variability of seston were the result of the allochthonous input of detritus and inorganic nutrients via terrestrial runoff. Annual primary production in this subtropical coastal lagoon ranged from 13 to 46 g C m?2 yr?1. Chlorophyll a in the bay ranged from 1 to 3 mg chlorophyll a m?2. In contrast, chlorophyll a in the surface centimetre of the sediment ranged from 50 to 300 mg chlorophyll a m?2. In this clear, shallow (2 to 3 m), oligotrophic lagoon, over 90% of total primary production is by submerged macrophytes and benthic algae. The high zooplankton biomass in the bay is most likely sustained by macrophyte detritus and the resuspension of benthic diatoms by the high winds associated with summer squalls and winter cold fronts. 相似文献
23.
TheMicrocystis bloom that once disappeared from Donghu Lake, a shallow, eutrophic Chinese lake, was successfully resumed with the use of
the enclosure method. Seston and dissolved organic carbon (DOC) dynamics during theMicrocystis bloom were investigated with particular emphasis on the effect of three Chinese domestic fishes (silver carp, bighead carp
and grass carp). The results showed that the change of chlorophyll a obviously related to the fish species and its stocking
density. Due to the release of extracellular ogranic carbon and increased bacterial activity, DOC increased apparently after
silver and bighead carps were introduced. POC/DOC dropped considerably in the enclosures containing silver and bighead carps
and in the surrounding lake water, which implied that the bacterial activity was more pronounced in such ecosystems. Statistical
analysis indicated that the linear relationship between POC and chlorophyll a could reflect the state of algal growth and
nutrient metabolism. It was expected that this study would provide some information on biomanipulation in the shallow, eutrophic
lakes.
This work was supported in part by a Grant-In-Aid from the Chinese Academy of Sciences, State Key Laboratory of Freshwater
Ecology and Biotechnology (FEBL) affiliated to the Institute of Hydrobiology for the project “Control Ecosystem: An Approach
to Lake Restoration”. 相似文献
24.
J. D. Green 《新西兰海洋与淡水研究杂志》2013,47(2):199-222
Lake Ototoa is a warm monomictic lake at 36° 31’ S, 174° 14'E. During a year's study (March 1969‐March 1970), the lake became thermally stratified in November, the metalimnion being between depths of 12 m and 16 m. Surface temperatures ranged between 10.2°c (in August) and 25.2°c (in late January), and bottom temperatures between 9.7°c and 17.5°c. The annual heat budget was calculated to be 642 354 KJ.m‐2 (15 500 cal.cm‐2) and the work of the wind in distributing the heat income 1.730 KJ.m‐2 (1766 g.cm.cm‐2). Secchi disc transparencies ranged between 5 m and 9.2 m (mean 7.07 m) and were greatest in the summer. Light transmission per metre was also high, ranging between 61% and 87%. Surface waters were normally supersaturated with oxygen, but during summer stratification oxygen concentrations in the bottom waters dropped to a minimum of 2.3 mg.litre‐2 and a positive heterograde distribution of oxygen with depth was found. The oxygen deficit was 0.015 mg.cm‐2.day‐1 and showed the lake to be oligotrophic. Mean surface pH was 7.82, and the ionic composition of the waters was similar to that of other small New Zealand and Australian lakes located near the sea. Compared with other New Zealand lakes PO4‐P concentrations (range 1.00–10.20 μg.litre‐1) were low and NO3—N concentrations (range 0.12–0.60 mg.litre‐1) high. 相似文献