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The extent of sediment resuspension caused by bottom trawling, storms, and dredging in the Baltic Proper
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
Swedish University of Agricultural Sciences (SLU), Department of Aquatic Resources, Institute of Marine Research.
(Swedish Meteorological and Hydrological Institute)
Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Abstract [en]

This study compares the extent and frequency of seafloor disturbances due to anthropogenic processes (bottom trawling and dredging) with those due to wind-driven waves in the Baltic Proper. There is little overlap between areas affected by bottom trawlers and naturally from waves, and bottom trawling is the main cause of sediment resuspension at greater (>73m) depths. Swedish bottom trawlers annually suspend between 3.8 and 13.6 M tonnes in this area, while from the reported dredging projects (reported between 2007 and 2009) the estimated maximum annual spillage was 0.14 M tonnes. The dominance of bottom trawling as a factor suspending sediment is clear, but management approaches for bottom trawling and dredging are different, despite similar expected effects on organisms and the environment. 

Keyword [en]
Baltic Sea, sediment resuspension, natural disturbance, anthropogenic disturbance, fisheries management, seafloor integrity
National Category
Ecology
Research subject
Marine Ecology
Identifiers
URN: urn:nbn:se:su:diva-98408OAI: oai:DiVA.org:su-98408DiVA: diva2:684726
Projects
Baltic Ecosystem Adaptive Management, BEAM
Funder
Formas, 2006-1018
Available from: 2014-01-08 Created: 2014-01-06 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
Ecology
Research subject
Marine Ecotoxicology
Identifiers
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)
Opponent
Supervisors
Projects
Baltic Ecosystem Adaptive Management (BEAM)
Funder
Formas, 2006-1018
Note

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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