Assessing the environmental quality of a historically-polluted fjord: a comparison of benthic foraminiferal eDNA and morphospecies proxy approaches

• Transitional environments present a unique challenge to Ecosystem Quality Status (EcoQS) assessment due to highly heterogenous conditions within the system, resulting in the “estuarine quality paradox”. Benthic foraminiferal assemblages provide high resolution environmental proxy records of the interaction between abiotic and biotic parameters in aqueous ecosystems. Fjords particularly have complex seabed topography which limits bottom water exchange and can result in hypoxia, and Idefjord on the Swedish Norwegian boarder is no exception. Although this oxygen decline is a natural occurrence which impairs fjord’s EcoQS, these ‘naturally stressed conditions’ complicate the definition of in-situ reference conditions if the system becomes subject to anthropogenic impact. At Idefjord the prolonged dumping of waste products from the paper and pulp manufacturing and bleaching industry, situated at the city of Halden, into the river Tista which feeds the fjord system, has led to a build-up of organic matter, sewage effluent and pollutant accumulation in the sediments. This study is the first assessment of foraminiferal diversity using sedimentary eDNA from one of the most polluted and anoxic fjords in Scandinavia, comparing the assemblage response reported by morphology-based and molecular ecosystem assessment techniques. Although index thresholds and genetic data processing decisions influence the EcoQS assessment category determined by each technique, both datasets report congruous responses in the benthic foraminiferal assemblages to pollution and environmental stress factors. Genetic methods tend to overestimate EcoQS at highly anoxic sites probably due to a presence of dormant propagules or extraorganismal DNA and suggesting that morphological methods are more suited to assessment in such conditions.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Multidisciplinär geovetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geosciences, Multidisciplinary (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Annan geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Other Earth and Related Environmental Sciences (hsv//eng)

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