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Impaired benthic macrofauna function 4 years after sediment capping with activated carbon in the Grenland fjords, Norway
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.ORCID iD: 0000-0002-8752-1516
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2021 (English)In: Environmental Science and Pollution Research, ISSN 0944-1344, E-ISSN 1614-7499, no 28, p. 16181-16197Article in journal (Refereed) Published
Abstract [en]

The sediments in the Grenland fjords in southern Norway are heavily contaminated by large emissions of dioxins and mercury from historic industrial activities. As a possible in situ remediation option, thin-layer sediment surface capping with powdered activated carbon (AC) mixed with clay was applied at two large test sites (10,000 and 40,000 m(2)) at 30-m and 95-m depths, respectively, in 2009. This paper describes the long-term biological effects of the AC treatment on marine benthic communities up to 4 years after treatment. Our results show that the capping with AC strongly reduced the benthic species diversity, abundance, and biomass by up to 90%. Vital functions in the benthic ecosystem such as particle reworking and bioirrigation of the sediment were also reduced, analyzed by using novel bioturbation and bioirrigation indices (BPc, BIPc, and IPc). Much of the initial effects observed after 1 and 14 months were still present after 49 months, indicating that the effects are long-lasting. These long-lasting negative ecological effects should be carefully considered before decisions are made on sediment remediation with powdered AC, especially in large areas, since important ecosystem functions can be impaired.

Place, publisher, year, edition, pages
2021. no 28, p. 16181-16197
Keywords [en]
Benthic ecology, Macrofauna, Bioturbation, Bioirrigation, Index, Contaminated sediment, Remediation
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-189181DOI: 10.1007/s11356-020-11607-0ISI: 000596042700001PubMedID: 33269443OAI: oai:DiVA.org:su-189181DiVA, id: diva2:1519902
Available from: 2021-01-19 Created: 2021-01-19 Last updated: 2022-02-25Bibliographically approved
In thesis
1. Ecological succession of benthic macrofauna following disturbance: Effects of contaminants and in situ sediment remediation
Open this publication in new window or tab >>Ecological succession of benthic macrofauna following disturbance: Effects of contaminants and in situ sediment remediation
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

More than 70% of the Earth is covered by water, and most of the sea floor consists of soft sediments, such as mud, clay and sand. Thus, soft sediments form one of the most important habitats on Earth, with a high diversity of organisms. However, the sediments in coastal areas are often subject to anthropogenic pollutants, and current remediation methods are often both costly and destructive on the ecosystem. Benthic macrofauna, i.e., sediment-living invertebrates larger than 1 mm, sustain a variety of ecosystem functions in the sediment by their activities; they oxygenate the sediment, redistribute particles and nutrients, and are also important secondary producers. Therefore, it is essential to maintain healthy benthic ecosystems and to study effects of various disturbances on benthic species composition and their recovery trajectory after disturbance, a process called ecological succession.

The aims of this PhD thesis were to investigate: 1) how benthic marine invertebrate communities in a Norwegian fjord respond to thin-layer capping with activated carbon, a recently proposed technique to remediate contaminated sediments in situ in a more cost-efficient and less ecosystem destructive manner, 2) how benthic community composition in sediments from the Baltic Sea is explained by environmental variables and concentrations of polycyclic aromatic hydrocarbons (PAHs) and metals, and 3) how well current benthic quality assessment indices as well as functional indices represent these disturbances.

The remediation method with activated carbon had long-term negative effects on the benthic macrofauna (paper I-III). Up to nine years after the capping, the communities were still severely affected, with lower species diversity, abundance and biomass. Recolonization of key species, such as the brittle star Amphiura filiformis, did not occur in the capped fields. Further, functional indices calculating bioturbation and bioirrigation estimated significantly lower activities in the communities exposed to activated carbon. Other studies have shown promising results in reducing contaminant fluxes and bioaccumulation of dioxins, but the long-term side-effects observed here on the benthic communities after capping show that the remediation method needs to be improved before application on a large scale. 

The benthic community composition was also studied in the Baltic Sea (paper IV). The significant factors to explain the benthic community structure were PAHs, even at medium to low concentrations in the sediment, together with the environmental variables salinity, temperature and depth. These variables also explained the Benthic Quality Index (BQI), used for ecological status assessments in coastal areas of Sweden and in the open Baltic Sea.

 However, several ecological indices commonly used to assess the benthic environmental status were not able to detect the disturbance caused by activated carbon in the Norwegian fjord (paper III), although clear effects on the benthic community in terms of lower species diversity and abundance were evident. Thus, current status assessment indices may need to be revised, or at least used with caution, in management evaluation of the sediments after disturbances other than eutrophication.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2022. p. 59
Keywords
Activated carbon, Benthos, Bioturbation, Contaminants, Environmental indices, Environmental monitoring, Environmental quality, Seafloor integrity, Sediment remediation
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-199659 (URN)978-91-7911-744-3 (ISBN)978-91-7911-745-0 (ISBN)
Public defence
2022-02-10, online via Zoom and in Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20, Stockholm, 13:15 (English)
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Available from: 2022-01-18 Created: 2021-12-14 Last updated: 2022-01-12Bibliographically approved

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Raymond, CarolineGunnarsson, Jonas S.

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