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Bottom trawling resuspends sediment and releases bioavailable contaminants in a polluted fjord
Stockholm University, Faculty of Science, Department of Systems Ecology.
Stockholm University, Faculty of Science, Department of Systems Ecology.
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2012 (English)In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 170, 232-241 p.Article in journal (Refereed) Published
Abstract [en]

Sediments are sinks for contaminants in the world's oceans. At the same time, commercial bottom trawling is estimated to affect around 15 million km(2) of the world's seafloor every year. However, few studies have investigated whether this disturbance remobilises sediment-associated contaminants and, if so, whether these are bioavailable to aquatic organisms. This field study in a trawled contaminated Norwegian fjord showed that a single 1.8 km long trawl pass created a 3-5 million m(3) sediment plume containing around 9 t contaminated sediment; ie. 200 g dw m(-2) trawled, equivalent to c. 10% of the annual gross sedimentation rate. Substantial amounts of PCDD/Fs and non-ortho PCBs were released from the sediments, likely causing a semi-permanent contaminated sediment suspension in the bottom waters. PCDD/Fs from the sediments were also taken up by mussels which, during one month, accumulated them to levels above the EU maximum advised concentration for human consumption.

Place, publisher, year, edition, pages
2012. Vol. 170, 232-241 p.
Keyword [en]
Sediment resuspension, Bottom trawling, Contaminant, Bioavailability, Blue mussel, SPMD
National Category
Environmental Sciences
URN: urn:nbn:se:su:diva-82144DOI: 10.1016/j.envpol.2012.06.019ISI: 000308450100029OAI: diva2:566627


Available from: 2012-11-09 Created: 2012-11-08 Last updated: 2014-01-14Bibliographically approved
In thesis
1. Sediment resuspension: Impacts and extent of human disturbances
Open this publication in new window or tab >>Sediment resuspension: Impacts and extent of human disturbances
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Resuspension of sediment by anthropogenic disturbances is a concern due to the impacts it has on organisms and ecosystems. Bottom trawling is one major cause of sediment resuspension. A field study showed that a small trawl created a sediment plume 120 - 150 m wide and 15-18 m high (Paper 1). The sediment in the same study was highly contaminated. Blue mussels exposed to the sediment plume showed an increased uptake of contaminants and after 1 month reached levels toxic for human health (Paper 1). In the Baltic Proper, bottom trawling is the main cause of sediment suspension in waters >73 m, where resuspension by wind induced waves is minimal. Compared with dredging, bottom trawling annually resuspends 23-88 times more sediment in this area (Paper 4).

Bottom trawling is expanding to deeper waters where sediment resuspension is expected to have larger impacts on organisms compared with shallow water. Deep water sponges create important habitats that are attractive fishing grounds. A laboratory experiment (Paper 3) showed that deep water sponges had a rapid respiratory response to short exposure of elevated turbidity.

Boat activities in harbours are another major cause of sediment and contaminant remobilisation to the water column. A laboratory experiment showed that suspension of sediment with high TBT concentrations induced higher mortality in blue mussels, Mytilus edulis, and faster growth inhibition of the alga Ceramium tenuicorne than unsuspended sediment (Paper 2).

This thesis clearly shows that resuspension due to human activities, in particular bottom trawling, is widespread and can have impacts on a range of organisms. However, there are large differences in management of these activities as they are covered by different legislative frameworks. When managing dredging, it is the most cited concern, whereas it is not considered in the management of bottom trawling.

Place, publisher, year, edition, pages
Stockholm: Department of Ecology, Environment and Plant Sciences, Stockholm University, 2014. 42 p.
National Category
Research subject
Marine Ecotoxicology
urn:nbn:se:su:diva-98640 (URN)978-91-7447-842-6 (ISBN)
Public defence
2014-02-14, föreläsningssalen, Institutionen för ekologi, miljö och botanik, Lilla Frescativägen 5, Stockholm, 14:00 (English)
Baltic Ecosystem Adaptive Management (BEAM)
Formas, 2006-1018

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript.

Available from: 2014-01-23 Created: 2014-01-08 Last updated: 2014-01-24Bibliographically approved

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