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SAMS technology aids aggregate extraction impact studies

Many benthic aquatic organisms rely on the suspension of particulate matter for food and / or for building materials, yet the water currents and associated sediment dynamics which provide the ideal environment for these animals can be disrupted by human actions. Aggregate dredging for example, generates significant amounts of suspended sediment which can result in smothering of habitats and / or an alteration of the suspended fraction which supplies those habitats.

How do benthic organisms respond to smothering and altered levels of suspended sediment? To date it has been difficult to replicate sediment loading under controlled laboratory conditions and therefore such investigations have been limited. At SAMS we have recently developed a prototype VOrtex Resuspension Tank (VORT) for the resuspension of food or sediments using an enclosed airlift. This mesocosm has successfully been applied in an investigation of tube growth in the sedentary polychaete worm Sabellaria spinulosa which is highly adapted to living in dynamic sedimentary environments.

Recent funding from the Marine Aggregate Levy Sustainability Fund (MALSF) will allow us to determine the impacts of SPM on organisms commonly found around sites of aggregate extraction. Species to be included in the study are: the Ross worm (Sabellaria spinulosa, illustrated left); mussel (Mytilus edulis); scallop (Pecten maximus); brown crab (Cancer pagurus); edible sea urchin (Echinus esculentus); common brittle star (Ophiothrix fragilis); the sea anemone (Sagartiogeton laceratus) and the sea squirt (Ciona intestinalis). Using a combination of methods including comparative buoyant weights, tube extensions, shell gaping and survival rates we will generate data on species specific smothering / sediment tolerances. These data can then be used to inform mitigation measures for the sustainable extraction of aggregates and may also be fed into environmental impact models that allow predictions of cumulative impact of dredging activities.

Davies AJ, Last KS, Attard K, Hendrick VJ (2009) Maintaining turbidity and current flow in laboratory aquarium studies, a case study using Sabellaria spinulosa. Journal of Experimental Marine Biology and Ecology 370: 35-40.

For more information on the Vort Resuspension Tank or the impact of suspended particulate matter on benthic organisms contact Kim Last or Andy Davies.