Ophelia 

About: Ophelia is an academic journal. The journal publishes majorly in the area(s): Population & Bay. It has an ISSN identifier of 0078-5326. Over the lifetime, 868 publications have been published receiving 34458 citations.

Coastal marine eutrophication: A definition, social causes, and future concerns

Abstract: There is a need in the marine research and management communities for a clear operational definition of the term, eutrophication. I propose the following: This definition is consistent with historical usage and emphasizes that eutrophication is a process, not a trophic state. A simple trophic classification for marine systems is also proposed: Various factors may increase the supply of organic matter to coastal systems, but the most common is clearly nutrient enrichment. The major causes of nutrient enrichment in coastal areas are associated directly or indirecdy with meeting the requirements and desires of human nutrition and diet. The deposition of reactive nitrogen emitted to the atmosphere as a consequence of fossil fuel combustion is also an important anthropogenic factor. The intensity of nitrogen emission from fertilizer, livestock waste, and fossil fuel combustion varies widely among the countries of the world. It is strongest in Europe, the northeastern United States, India/Pakistan, Jap...

Submerged aquatic vegetation in relation to different nutrient regimes

Abstract: Submerged vegetation respond to increased nutrient loading through a shift from slow-growing seagrasses and large macroalgae to fast-growing macroalgae, and the ultimate dominance of phytoplankton at high nutrient loadings. This shift reflects a change from nutrient to light limitation along the eutrophication gradient. Slow-growing seagrasses and large macroalgae are good competitors when nutrients are limiting because they have relatively low nutrient requirements, are able of efficient internal nutrient recycling, and can access the elevated nutrient pools in the sediment. Fast-growing macroalgae and phytoplankton are superior competitors when light is limiting because they are positioned closer to the water surface, and capture and use light more efficiently. The important ecosystem consequences of altered nutrient regimes derive from the shift in dominant vegetation types. Slow-growing seagrasses and large macroalgae are longevous, decompose slowly, and experience only moderate grazing losse...

Systematics and ecology of the Isefjord marine fauna (Denmark) with a survey of the eelgrass (Zostera) vegetation and its communities

Abstract: This paper represents the results of more than 30 years field observations and research work carried out from the Isefjord Laboratory, Vellerup Vig (Zealand, Denmark), which is owned and financed by the author. The Isefjord complex, 36 km long, including the main fjord and the Roskilde Fjord, and covering about 400 km2, is a shallow (7–10 m, max. 30 m) area dominated by substrata of fine sand to mud with a high content of organic matter. As a guidebook for future research the first part gives information about distribution, systematics, ecology, and breeding of the majority of the 477 animal species described. Nearly 400 species are invertebrates and of the chordates 68 species are true fishes. 63% of all animal species have not previously been recorded from the area, 27 species are new to Danish seas, and one (Polychaeta, Capitellidae) is new to science. The hydrography is treated mainly on the basis of literature. The fjord system may be classified as mixohaline: the Isefjord proper is polyhali...

The ecology of marine microbenthos IV. Structure and function of the benthic ecosystem, its chemical and physical factors and the microfauna commuities with special reference to the ciliated protozoa

Abstract: The paper describes the ecosystem constituted by marine sediments and their microfiora and fauna but with special emphasis on the ecology of ciliated protozoa. This description is based on quantitative studies of the vertical and horizontal distribution of the fauna, the physicochemical factors (O2, H2, S, Eh, pH, grain size, organic matter, salinity) and the microfiora, and on model experiments with artificial and natural sediments. Factors controlling the oxidation-reduction properties of sediments, the O2-uptake of reduced sediments and the respiration and photosynthesis of undisturbed sediments were studied. Among other things it is demonstrated that the microfaunal communities can be correlated with the oxidation-reduction properties of sediments and with their mechanical composition and that the endproducts of anaerobic decomposition (notably H2S) are of large trophic significance to the sediment ecosystem through the activity of cherno- and photoautotrophic bacteria. The energetic role of ...

Plankton and nutrient dynamics in marine waters

Abstract: Biological oceanographers generally distinguish between two contrasting trophic pathways in the pelagic environment, i.e. the herbivorous and the microbial food webs. The former goes from large phytoplankton and zooplankton to fish, whereas the latter comprises small eukaryotic algae and cyanobacteria as well as heterotrophic bacteria and protozoa. The present paper describes a continuum of trophic pathways, between systems dominated by the herbivorous food web and those dominated by the microbial loop (i.e. almost closed system of heterotrophic bacteria and zooflagel-late grazers, the latter releasing dissolved organic matter used as substrate by the bacteria). It is proposed that the continuum goes from the herbivorous web (or chain) to a “multivorous food web”, to the microbial web, and finally the microbial loop. Characteristics of the various pathways maybe summarized as a series of interconnected ratios. It is hypothesized that systems dominated by the herbivorous food web or the microbial ...