Soft bottom macrofauna: Collection, treatment, and quality assurance of samples.

Abstract

The aim of these recommendations is to standardize the methods used by different scientists for benthos surveys in order to increase the comparability of results for different areas. The results of ICES/HELCOM Quality Assurance workshops, intercalibrations, and ring tests have been incorporated in this set of recommendations in order to increase the quality, reliability and, thus, comparability of benthos data at a time when an increasing number of researchers and institutions are engaged in sorting and analysing benthos samples before their final evaluation and the storage of information in public data banks. The choice of an appropriate sampler depends on the average living depth of the infauna in question, which can range from the upper millimetre down to almost one metre. Possible discrepancies between the penetration depth of the sampler and the actual living depth must be considered when analysing the results. This set of recommendations covers all steps from the design of the sampling programme to considerations of which gear to use, and all ship-board methods such as sampling with grabs, corers, dredges, and trawls. There is no single standard sampling gear for benthos investigations. The choice of a suitable sampler is a compromise between specific sampling characteristics in different sediment regimes in the area to be sampled, good handling characteristics at sea in bad weather conditions, suitability for various ships, financial limitations, tradition, and scientific questions. Criteria for the rejection of samples are identified. Treatment of samples is described in detail including sieving, transfer of the sample to the sample vessel, fixation, staining, and labelling, followed by a description of laboratory procedures such as sorting, taxonomic identification, and biomass determinations. A list of items for in-house quality assurance is included together with diagrams of suitable sieving devices and details for a warp-rigged Van Veen grab.