Benthic diatom-based indices and isotopic biomonitoring of nitrogen pollution in a warm temperate Austral river system.

Autor: Dalu T; Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou 0950, South Africa; South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa. Electronic address: dalutatenda@yahoo.co.uk., Cuthbert RN; South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, 24105 Kiel, Germany., Taylor JC; South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; Unit for Environmental Science and Management, North-West University, Potchefstroom 2520, South Africa., Magoro ML; South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; DSI/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa., Weyl OLF; DSI/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa., Froneman PW; Department of Zoology and Entomology, Rhodes University, Makhanda 6140, South Africa., Wasserman RJ; South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; Department of Zoology and Entomology, Rhodes University, Makhanda 6140, South Africa.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2020 Dec 15; Vol. 748, pp. 142452. Date of Electronic Publication: 2020 Sep 22.
DOI: 10.1016/j.scitotenv.2020.142452
Abstrakt: Rivers are impacted by pollutants from anthropogenic activities such as urbanisation and agricultural practices. Whilst point source pollution has been widely studied and in some cases remediated, non-point pollutant sources remain pervasive, particularly in developing countries that lack economic and human specialist capacity. Monitoring of pollution levels in many regions is additionally challenged by a lack of robust indicators for nitrogen inputs, however, diatom community indices and analysis of variation in microphytobenthos (MBP) stable isotope analysis variations have potential. The present study investigates variations and utilities in benthic diatom indices and MPB δ 15 N along different river sections (n = 31) of an austral river between two seasons (wet and dry), testing for relationships with key environmental variables (physical, water and sediment), in the context of N monitoring. One hundred and eighteen diatom taxa belonging to 36 genera were identified, with physical (water flow), water (nitrate, P and total dissolved solids) and sediment (B, Ca, Cr, Na, N, P, SOM, Pb and Zn) variables correlating to one or more of the 12 diatom indices presented. In particular, Biological Diatom Index, Biological Index of Water Quality, Central Economic Community, Index of Artois-Picardie Diatom (IDAP) and Sládeček's Index were strongly explained by sediment variables, whilst Descy's Pollution Index and Schiefele and Schreiner's Index were explained by water and physical variables. Whilst MPB δ 15 N were within the "no impact" level in the wet and dry seasons at reference (i.e. unpolluted) sites, all sites located in agricultural or urban areas, and downstream of sewage discharges, had a wider range that encompassed increasing organic impacts ("inorganic impacts" to high "organic impacts"). Temperature and turbidity (negative), as well as dissolved oxygen, waterway width and depth (positive), significantly affected MPB δ 15 N, whilst effects of chemistry variables were less apparent. Overall, we found that MPB δ 15 N signatures were significantly correlated with Trophic Diatom Index, the Specific Pollution Sensitivity Index and the Artois-Picardie Diatom Index, suggesting the utility of diatoms and MPB δ 15 N in assessments of aquatic pollution. In turn, MPB δ 15 N values are strong indicators of N pollution across spatial and seasonal gradients. Thus, the results showed the effects of sediment variables on diatoms to be strong, indicating that sediment rather than water characteristics more strongly structure diatom communities. Thus, sediment variables should be sampled when conducting bioassessment studies.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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