Scientific sampling
Until now the soft bottom benthos of te Baltic is sampled by Van Veen style (0.1m2) grab samplers. There are alsocoring gears in use with different sampling volumina. These gears probably provide better sample quality but have other restrictions.
Conventional sampling methods are destructive from the reproductive point of view. It is not possible to sample the exact spot again and again. These methods are expensive and time consuming and may not fulfill the needs of environmental management. The extensive laboratory investigation and species determination and quantitative data does not provide fast data access for decision makers. Quantitative sampling is based on well tested and established methods, which allows the statistical analysis of temporal and spacial variability. Intercalibration and quality assurance between laboratoryie standardised the sampling and increased the liability of data.
The clearly visible disadvantages of convetional methods lead to the development or adaptation of imaging techniques. Additional, the method for analysis of images was developed and influenced by the fields of geology and geography. These imaging techniques spread from echosounder surveillance of the sea floor and nearby sedimentlayers to wide reaching side scan sonar pictures of surface structures to a variety of still photography and video imaging. These last techniques developped for military and civilian purposes can be widely applied by biologists.
A Special application of underwater still photography is the REMOTS sediment profile camera. This technique delivers high resolution pictures for documentation of the first 20cm of the sediments together with the sediment water boundary layer. In 1984, Joseph Germano and Donald Rhoads developed that method together with a new investigation protocol, which logged cornsize, surface roughness, depth of the redoxlayer, sulfidlayers, methan bubbles, thickness of the surface layer digging and drilling sediments. Additionally this provides the ability to see epifauna, tubes and holes, amount of feces and microbiological meadows (Beggiatoea), the dominant fauna and their living depth and tracks, like bioturbation.
The results of imaging techniques start at the general estimation of environmental quality in polluted areas like aquaculture plants and the surveillance of sewage sludge and dump areas up to the evaluation and documentation of fish trawling. Specially in the Baltic Sea imaging techniques are a powerfull tool to distinguish oxygen depleted areas. Prestudies with imaging tools are very valuable addons for indespensible, traditional sampling methods, but they provide a more effective and cheaper realization of the sampling schedule. Combining sampling gears with imaging in one gear initializes high control during the sampling especially in very small structured investigation areas. Additionally a check on undesired disturbance of the sea floor by the gear itself is possible. This can also be used for quality control or evaluation.
The analysis of video profiles and photographs (REMOTS and surface) provides a new view on the conditions of the habitat of soft sediments. This was not possible with other techniques. Some general assumptions can be derived from these pictures. The essential quality measure of the Baltic sea floor seams to be the presence and absence of macrofauna, which can be easily estimated by imaging.
