Isotopic signatures in Mytilus galloprovincialis and Ulva latuca as bioindicators for assessing discharged sewage effluent in coastal waters along Otago Peninsula, New Zealand

Oluwuyi Babaranti,Stephen Horn,Tim Jowett,Russell Frew

doi:10.1080/24749508.2018.1485079

Oluwuyi Babaranti, Stephen Horn + Show 2 more

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https://doi.org/10.1080/24749508.2018.1485079

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Abstract

ABSTRACTSewage, waste organic matter from domestic and municipal wastewater, causes increased secondary productivity, eutrophication and trace metal contamination, reduced oxygen levels, and biodiversity which can lead to ecological disturbances in the natural aquatic ecosystem. The impact of sewage-derived organic matter (SDOM) on the nearshore marine ecosystem of the Otago Coast was assessed before, and 15 years after upgrade of the Dunedin sewage treatment plant. Carbon and nitrogen isotopic ratios in the tissues of sentinel organisms were used as bioindicators to elucidate the primary sources of nutrition the coastal environment. Mytilus galloprovincialis, a marine bivalve, exhibited a strong influence of SDOM from two sites in 2001. In 2015, M. galloprovincialis had a trophic enrichment factor of 3‰ (δ15N) and 1‰ (δ13C) when compared to the marine particulate organic matter (POM), suggestive of a dietary change away from the SDOM. Suspended POM collected from riverine and estuarine sources revealed other possible nitrogen sources from human-driven activities such as pastoral farming, application of organic manure and inorganic fertilisers, nitrification of ammonium from semi-urban septic tanks, and animal organic waste residues.

Highlights

A major organic component of domestic and municipal wastewater, can cause increased secondary productivity (Hillebrand & Sommer, 2000), eutrophication (Jarvie, Neal, & Withers, 2006), heavy metal contamination (Chary, Kamala, & Raj, 2008; Cheevaporn & Menasveta, 2003; Morillo, Usero, & Gracia, 2004), reduced oxygen levels, and biodiversity which can lead to ecological disturbances (Browne et al, 2011; Diaz, Rhoads, Blake, Kropp, & Keay, 2008) in the natural aquatic ecosystems (Deegan & Buchsbaum, 2005; Hargrave, Holmer, & Newcombe, 2008)
In 2001, the carbon and nitrogen isotopic ratios in the tissues of M. galloprovincialis and U. latuca indicated that two sites (i.e., Tomahawk and Smaills) were heavily impacted by the discharged sewage effluent demonstrated in the lower δ13C and δ15N values
M. galloprovincialis and U. lactuca were influenced by sewage at the two previously contaminated beaches in 2001

Summary

Introduction

A major organic component of domestic and municipal wastewater, can cause increased secondary productivity (Hillebrand & Sommer, 2000), eutrophication (Jarvie, Neal, & Withers, 2006), heavy metal contamination (Chary, Kamala, & Raj, 2008; Cheevaporn & Menasveta, 2003; Morillo, Usero, & Gracia, 2004), reduced oxygen levels, and biodiversity which can lead to ecological disturbances (Browne et al, 2011; Diaz, Rhoads, Blake, Kropp, & Keay, 2008) in the natural aquatic ecosystems (Deegan & Buchsbaum, 2005; Hargrave, Holmer, & Newcombe, 2008). Between 1908 and 1950s, raw sewage was discharged directly into the Pacific Ocean at Lawyers Head (Council, 2001) by the Dunedin Water Pollution Control Plant ( called Tahuna Wastewater Treatment Plant). The advancement in the wastewater management involved the construction of a new pump station to the increased flow rate of the wastewater treatment plants. This was done to improve the quality of effluent and shoreline water quality, reduce organic matter content, and ensure public health protection which was a major concern at that time (Bouman & Archer, 2014)

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