Benthic fauna refers to various organisms found on (epifauna) and in (infauna) the seabed. Sediment-dwelling benthic fauna can be subdivided into the main groups of mussels/snails, crustaceans, bristle worms and echinoderms. A benthic fauna survey is an ecologically relevant parameter which, among other things, can indicate whether an oxygen deficiency has occured or not at a certain place. Different kinds of equipment are used for benthic fauna sampling, depending on the water depth and the sediment type. In shallow-waters the infauna is sampled with a core sampler (i.e. a Haps-corer). This can be done from land, from a boat or by diving, depending on the water depth. In deeper waters the preferred sampler is a ”grabber” (e.g Smith-McIntyre and van Veen). The samples are subsequently sieved and then immediately preserved (in ethanol or formalin). All samplings and species identifications are made by Toxicon’s experienced and skilled staff in accordance with swedish national or regional guidelines.
Epifauna can be subdivided into mobile and stationary organisms. Mobile epifauna consists by definition of larger mobile crustaceans and fish, whereas the stationary epifauna consists of organisms which live on the surface of the sediment and/or in the vegetation. Mobile epifauna is sampled with a drop trap in shallow-waters with a maximum depth of 1 meter. The drop trap is a metal box which is dropped through the water to the bottom after which the epifauna trapped inside the box is caught by netting. Epifauna in the vegetation is sampled with a netted bag that is lowered over a chosen part of the vegetation (e.g. a macroalgae plant or eelgrass), which is then cut off from it’s roots and enclosed in the bag. Epifauna samples are preserved immediately after sampling; species identification takes place later at the laboratory. Samplings and species identifications are carried out by Toxicon’s experienced and skilled staff in accordance with swedish national or regional guidelines.
Fredrik Lundgren is in charge of Toxicon Environment’s benthic fauna unit. He has participated in several EPA (Swedish Environmental Protection Agency) benthic fauna intercalibrations concerning the Baltic Sea as well as the North Sea with excellent results. He also participated in the EPA 2011 benthic fauna workshop.