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Response of marine benthic fauna to thin-layer capping with activated carbon in a large-scale field experiment in the Grenland fjords, Norway
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Svensk Ekologikonsult, Sweden.
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.ORCID iD: 0000-0002-8752-1516
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Number of Authors: 62017 (English)In: Environmental Science and Pollution Research, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 24, no 16, p. 14218-14233Article in journal (Refereed) Published
Abstract [en]

A field experiment with thin-layer capping was conducted in the Grenland fjords, Norway, for remediation in situ of mercury and dioxin-contaminated sediments. Experimental fields at 30 and 95 m depth were capped with (i) powdered activated carbon (AC) mixed with clay (AC+clay), (ii) clay, and (iii) crushed limestone. Ecological effects on the benthic community and species-feeding guilds were studied 1 and 14 months after capping, and a total of 158 species were included in the analyses. The results show that clay and limestone had only minor effects on the benthic community, while AC+clay caused severe perturbations. AC+clay reduced the abundance, biomass, and number of species by up to 90% at both 30 and 95 m depth, and few indications of recovery were found during the period of this investigation. The negative effects of AC+clay were observed on a wide range of species with different feeding strategies, although the suspension feeding brittle star Amphiura filiformis was particularly affected. Even though activated carbon is effective in reducing sediment-to-water fluxes of dioxins and other organic pollutants, this study shows that capping with powdered AC can lead to substantial disturbances to the benthic community.

Place, publisher, year, edition, pages
2017. Vol. 24, no 16, p. 14218-14233
Keywords [en]
Benthic ecology, Macrofauna, Benthic community, Feeding guilds, Contaminated sediment, Remediation
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-144679DOI: 10.1007/s11356-017-8851-6ISI: 000402748300029PubMedID: 28421523OAI: oai:DiVA.org:su-144679DiVA, id: diva2:1128117
Available from: 2017-07-21 Created: 2017-07-21 Last updated: 2022-03-23Bibliographically 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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