Benthic

Problems associated with excessive levels of nutrients and unwanted nuisance species have already been mentioned. There are cases in which intentional fertilization is used by aquaculturists in order to produce desirable types of natural food for the species under culture. Examples of this approach include inorganic fertilizer appHcations in ponds to promote phytoplankton and zooplankton blooms that provide food for young fish such as channel catfish, the development of algal mats through fertilization of milkfish ponds, and the use of organic fertilizers (from Hvestock and human excrement) in Chinese carp ponds to encourage the growth of phytoplankton, macrophytes, and benthic invertebrates. In the latter instance, various species of carp with different food habits are stocked to ensure that all of the types of natural foods produced as a result of fertilization are consumed. 

In several cases, such as shellfish areas and aquatic reserves, the usual water quaUty parameters do not apply because they are nonspecific as to detrimental effects on aquatic life. Eor example, COD is an overall measure of organic content, but it does not differentiate between toxic and nontoxic organics. In these cases, a species diversity index has been employed as related to either free-floating or benthic organisms. The index indicates the overall condition to the aquatic environment. It is related to the number of species in the sample. The higher the species diversity index, the more productive the aquatic system. The species diversity index is computed by the equation K- = (S — 1)/logjg I, where S is the number of species and /the total number of individual organisms counted. 

Another possible example of endocrine disruption in situ relates to the hndings of Moore and Stevenson" of altered sex ratios and intersex harpacticoid copepods in the vicinity of Edinburgh s long sea sewage outfall. Intersexiiality is common in some crustaceans but is extremely rare in harpacticoid copepods. There was no relationship between the frequency of intersex and distance from the most contaminated sites and nor was there evidence that other benthic species had been adversely affected. Additional work is required to prove conclusively that endocrine disruption is involved in this case. 

G. A. Codd, The Toxicity of Benthic Blue-Green Algae in Scottish Freshwaters, Report No. FR/SC... 

Kick net 500 micron white mesh net is designed to meet the requirements of groups performing USEPA Rapid Bioassessment Protocols for Benthic Invertebrates. (Benthic = bottom dwelling). 

Sediment Analysis. Sediment is the most chemically and biologically active component of the aquatic environment. Benthic invertebrate and microbial life concentrate in the sediment, a natural sink for precipitated metal forms, and an excellent sorbent for many metal species. TTie extent to which potentially toxic trace element forms bind to sediment is determined by the sediment s binding intensity and capacity and various solution parameters, as well as the concentration and nature of the metal forms of interest. Under some conditions sediment analyses can readily indicate sources of discharged trace elements. 

Gaillard, J.-F. and Treguer, P. (1997). Antares I France JGOFS in the Indian Sector of the Southern Ocean Benthic and water column processes. Deep-Sea Res. 1144, 951-1176. 

Van Cappellen, P. and Ingall, E. D. (1994). Benthic phosphorus regeneration, net primary production, and ocean anoxia A model of the coupled marine biogeochemical cycles of carbon and phosphoms. Paleoceanography 9,677-692. 

Fig. 18-1 Benthic foraminiferal oxygen isotope record from 3477 m water depth in the eastern tropical Pacific ocean from Ocean Drilling Program site 677 (Shackleton et al, 1990). ratios are expressed in the S...

This high availability of materials can also be related to the high enzymatic activities in the water as well as relevant organic carbon uptake by the benthic microorganisms [40, 41],... 

Artigas J, Romani AM, Gaudes A, et al (2009) Benthic structure and metabolism in a Mediterranean stream from biological communities to the whole stream ecosystem function. Fresh. Biol. 54 DOI 10.1111/j.l365-2427.2008.02140.x... 

Sabater S, Vilalta E, Gaudes A et al (2003) Ecological implications of mass growth of benthic cyanobacteria in rivers. Aquat Microb Ecol 32 175-184... 

Haidekker A, Hering D (2008) Relationship between benthic insects (Ephemeroptera, Plecoptera, Coleoptera, Trichoptera) and temperature in small and medium-sized streams in Germany a multivariate study. Aquat Sci 42 463 81... 

Among the physical factors, current velocity has a special significance for benthic biofilms because it can modulate the diffusion of metals through the biofilm and their effects [18, 40]. pH and organic complexation are particularly significant for metal bioavailability [42]. Therefore, metal toxicity will also depend on the influence that environmental variability has on its bioavailability. 

Inputs of organic matter and nutrients, benthic metabolism, and nutrient retention at each stream section depend on diffuse and point sources. Yet, under low flow conditions, water and matter transport downstream becomes impeded or discontinued due to stream contraction and fragmentation during dry periods. Therefore, nutrient export from rivers in semiarid regions will depend, more so than in more humid regions, on the interplay between the spatial configuration of organic matter... 

Langston, W.J., Bnrt, G.R., and Mingjiang, Z. (1987). Tin and organotin in water, sediments, and benthic organisms of Poole Harbour. Marine Pollution Bulletin 18, 634—639. 

In a similar way, microalgal biomass on the sediment surface can be estimated by measuring the chlorophyll contents in benthic microalgae, which are single-celled microscopic plants that inhabit the top 0 to 3 cm of a sediment surface and are sometimes referred to as microphytobenthos. These organisms are the primary food resources of benthic grazers such as shellfish and numerous finfish species. 

Benthic invertebrates are macroscopic animals that live at or near the sediment/water interface. Some benthic invertebrates, particnlarly mnssels, readily accnmnlate metals, prompting their use as biological indicators of mercnry contamination (Smith... 

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