1,721,364 research outputs found
The 1991 Dutch Kenya Expedition
No full textIt is proposed to the Dutch Foundation for Marine Research SOZ to organize an expedition to the Kenyan coastal area in 1991. The exact timing of the expedition depends on the availability of the research vessel Tyro. Suitable periods would be December-March (May) and/or September-December. The aim of the expedition in general is to provide basic data on the structure and functioning of marine systems along the East-African coast, and, in particular, to evaluate the ecological effects of the rivers on these marine systems. As a result of human activities, the composition of the riverine water has strongly changed; it is expected that this will have profound effects on the coastal ecosystems. The continental shelf is limited and the ocean becomes very deep close to the Kenyan coast. There is no information on the deeper benthic ecosystems near the coast and also with respect to the pelagic domain only limited information is available: so far it appears that these areas combine a low productivity with a high diversity. In the North, the Somalistream causes strong upwelling during summer. The interactions between the off-shore and coastal areas and the impact of the monsoon on these interactions are unknown. The sedimentology of the East-African coastal zone is unknown as well. The coastal ecosystems in Kenya consist of: (1) coral reefs (fringing reefs) along the entire coastline, with extensive areas of seagrass beds on the more sheltered parts of the backreefs and in lagoonal areas; (2) mangroves on the shores of the brackish parts of rivers and creeks along the coast; also seagrass beds can be found here.Publishe
Verontreiniging van de Noordzee: het ecologisch perspectief
No full textThe author tries to illustrate the complex interaction of physical, chemical, geological and biological processes that are important in determining pathways of pollutants in the environment by using two examples the speciation of mercury in estuarine and marine environments where the chemical and microbiological aspect is important: and eutrophication in the North Sea, with hydrodynamical, geological and biological processes on small to medium scales. It is argued that much fundamental research remains to be done before the impact of pollution on the marine environment will be really understood. Belgium is the only EEG country without an institute devoted to the fundamental study of the seas. If Belgium is to conserve its international role in this domain, it will have to create such an institute soon, since the role of the universities is ever decreasing due to lack of funds and. above all personnel
Stable isotopes as trophic tracers: combining field sampling and manipulative labelling of food resources for macrobenthos
Get PDFWe combined 3 different approaches to determine the relative importance of microphytobenthos production as food for intertidal macrobenthic animals: (1) the natural abundance of stable-isotope ratios of carbon and nitrogen, (2) an in situ deliberate tracer addition of C-13-bicarbonate, which was transferred through the benthic food chain after its incorporation by benthic algae, and (3) a dual labelling experiment in a flume, where pelagic and benthic algae were labelled with N-15 and C-13, respectively. The results of the 3 approaches confirmed the high importance of microphytobenthos as a food source for (surface) deposit feeders. Despite the clearly demonstrated resuspension of benthic algae at high current velocities, suspension feeders appeared to depend almost exclusively on pelagic algae (and possibly detrital carbon) as a food source. Based on the results of the experiments, we determined an approximate degree of dependence on microphytobenthos for different species of intertidal macrobenthos. The macrobenthic biomass at 5 study locations, when weighted by these coefficients, correlated very well with measured productivity of the microphytobenthos. [KEYWORDS: food web; microphytobenthos; deposit feeding; suspension feeding; westerscheldeflume Marennes-oleron bay; westerschelde estuary; benthic invertebrates; arenicola-marina; carbon; nitrogen; gut; microphytobenthos; sediments; matter]
Comparing species diversity and evenness indices.
No full textIn a low diversity brackish water habitat the diversity of the copepod community is best measured with the Shannon-Wiener information function and its evenness by an index proposed by the first author (eH -1)/(S -1). This was shown by comparing the statistical behaviour of the more important diversity and evenness indices currently used
A note on the life-span of r-strategists
No full textThe idea is presented that the short life-span of r-strategists may in some cases be an adaptation to avoid predation. Evidence supporting this hypothesis is presented by examination of predation of the polyp Protohydra leuckarti on harpacticoid copepods
The succession of benthic micrometazoans in a brackish water habitat
No full textDuring the investigation of a shallow brackish water pond in northern Belgium, attention was paid to the quantitative occurrence of several micro-metazoan groups of the benthos: hydrozoa, oligochaeta, nematoda, copepoda and ostracoda. These groups show a succession in time, each group having a different moment of maximum abundance
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