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Benthos

Benthic Macro-invertebrates as Bioindicators
Benthos are often used to indicate ecosystem quality and status in aquatic environments. Stream environments are analyzed based on the presence and abundance of benthic macro-invertebrates. Benthos are prolific in different parts of a stream, making them sufficient study organisms throughout a river ecosystem. Benthos are also prime indicators of stream ecosystem contamination because they reside in the sediment of the stream, which is where the majority of water contaminants will settle. [1] Damásio, Joana; Fernández-Sanjuan, Maria; Sánchez-Avila, Juan; Lacorte, Silvia; Prat, Narcís; Rieradevall, Maria; Soares, Amadeu M. V. M.; Barata, Carlos (2011-06-01). "Multi-biochemical responses of benthic macroinvertebrate species as a complementary tool to diagnose the cause of community impairment in polluted rivers". Water Research. 45 (12): 3599–3613. doi:10.1016/j.watres.2011.04.006. ISSN 0043-1354

[2] Rodrigues, Carolina; Guimarães, Laura; Vieira, Natividade (2019-08-01). "Combining biomarker and community approaches using benthic macroinvertebrates can improve the assessment of the ecological status of rivers". Hydrobiologia. 839 (1): 1–24. doi:10.1007/s10750-019-03991-7. ISSN 1573-5117. Surface Runoff

Agricultural issues[edit]
The other context of agricultural issues involves the transport of agricultural chemicals (nitrates, phosphates, pesticides, herbicides, etc.) via surface runoff. This result occurs when chemical use is excessive or poorly timed with respect to high precipitation. The resulting contaminated runoff represents not only a waste of agricultural chemicals, but also an environmental threat to downstream ecosystems. Pine straws are often used to protect soil from soil erosion and weed growth. However, harvesting these crops may result in the increase of soil erosion. Out of large river systems, some of the highest areas of water contamination occur in regions of agricultural practices. Biomarker

Ecotoxicology[edit]
Main article: Biomarkers of exposure assessment

See also: Bioindicator

Rachel Carson, the author of Silent Spring, raised the issue of using organochlorine pesticides and discussed the possible negative effects that said pesticides have on living organisms. Her book raised ethical issues against chemical corporations that were controlling the general reception of the effect of pesticides on the environment, which pioneered the need for ecotoxicological studies. Ecotoxicologial studies could be considered the precursors to biomarker studies. Biomarkers are used to indicate an exposure to or the effect of xenobiotics which are present in the environment and in organisms. The biomarker may be an external substance itself (e.g. asbestos particles or NNK from tobacco), or a variant of the external substance processed by the body (a metabolite) that usually can be quantified. Bibliography (Benthos)