Aquatic organism responses

Responses of Aquatic Organisms. The interactions between aquatic organisms and the chemistry of their water habitats are extremely complex. If a species or a group of species increases or declines in numbers in response to acidification, then the biological structure of the entire water body is likely to be affected. Reactions of organisms to stress such as acidification can be termed a "dose-response" reaction (i.e. a certain dose of acidifying pollutant induces a certain response). 

Besides nitrogen fixation, the only other major source of reduced nitrogen is the decomposition of soil or aquatic organic matter. This process is called ammonification. Heterotrophic bacteria are principally responsible for this. These organisms utilize organic compounds from dead plant or animal matter as a carbon source, and leave behind NH3 and NHJ, which can then be recycled by the biosphere. In some instances heterotrophic bacteria may incorporate a complete organic molecule into their own biomass. The majority of the NH3 produced in this way stays within the biosphere however, a small portion of it will be volatilized. In addition to this source, the breakdown of animal excreta also contributes to atmospheric... 

Important, poorly-constrained variables in this carbon balance include temporal and spatial variations in precipitation and RO DIC, carbonate dust, and pedogenic carbonate and soil C02. In addition, ocean and lake response to river carbon input is not well known. Although marine and freshwater aquatic organisms can be fertilized by increases in N, P, Si, Fe, Zn and C02 (Cassar et al. 2004 Zondervan 2007), it is not clear how much of the... 

The use of clinical diagnostic procedures by which to identify and evaluate specific organ dysfunction is used widely in human and mammalian toxicology. Despite the apparent usefulness of such techniques little has been done to develop similar methods for use in studying toxic responses in aquatic organisms. 

In addition to references on these topics, a separate reference section is devoted to other E P materials. Information related to human health effects is emphasized in this article. Included are the mostly qualitative accounts, by industrial or military physicians, of human intoxication documentation of mammalian toxicity expts and the results of microbial mutagenicity testing, a comparatively recent development. Brief summaries have been presented of the results of tests on aquatic organisms because of their sensitivity to the pollutants that surround them, such organisms provide responses indicative of water quality... 

Shchepkin, V.Ya. and Minyuk, G.S. (1990). The levels of accumulated energy and the response to light in Black Sea sprat (In Russian). In Bioeneigetics of Aquatic Organisms (G.E. Shulman and G.A. Finenko, eds), pp. 207-221, Naukova Dumka, Kiev. 

Study of the role played by living organisms in trace metal control - A considerable number of laboratory-based studies have been done on the response of aquatic organisms to trace element perturbations, mainly in relation to toxicity. However, studies utilising organisms relevant to environmental systems and conducted under realistic environmental conditions are urgently needed. Mechanisms used by organisms to control the external chemical medium are mostly unknown. 

Electrochemical methods have been used for determinations of species of elements in natural waters. Of the many electrochemical techniques, only a few have proved to be useful for studies of speciation in complex samples, and to possess the sensitivity required for environmental applications. The greatest concern is the measurement of the toxic fraction of a metal in an aqueous sample. The definition of a toxic fraction of a metal is that fraction of the total dissolved metal concentration that is recognised as toxic by an aquatic organism. Toxicity is measured by means of bioassays. Elowever, a universally applicable bioassay procedure cannot be adopted because the responses of different aquatic species to metal species vary. Nevertheless, bioassays should be used as means of evaluation and validation of speciation methods. A condition is that the test species (of the bioassay) should be very sensitive to the metals being studied so as to simulate a worst case situation (Florence, 1992). 

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