Effects of biological disturbance by<Emphasis Type="Italic"> Monoporeia affinis</Emphasis> (Amphipoda) on small-scale migration of marine nematodes in low-energy soft sediments

Free-living marine, benthic nematodes quickly colonise sediments where physical forces are strong enough to suspend them into the water column. In the absence of such forces colonisation is much slower and is more likely to be affected by biological factors. The aim of the study was to investigate if nematodes disperse more readily in the presence of biological disturbance where physical disturbance is rare or non-existent. Amphipods are able to greatly rework sediments, and thereby induce disturbance to the infauna. A laboratory experiment with the amphipod Monoporeia affinis and nematodes from a low-energy, 30-m-deep location was conducted in mesocosms where the nematodes were given the choice to colonise azoic sediment at three amphipod densities, zero, low and high. Each area of azoic sediment in the mesocosms was divided into three equilateral sections from the nematode source, i.e. 10, 23 and 36 cm. At termination, after 7 weeks, there were no significant differences in nematode abundance and assemblage structure between treatments despite considerable biological disturbance created by the amphipods. The number of nematodes was 16%, 15% and 11% of the total numbers in the source at the three sections 10, 23 and 36 cm, respectively. There were distinct differences in the nematode community composition between distances, with the small surface-dwelling taxon Leptolaimus spp. being a rapid and the numerically dominant coloniser of the azoic sediments. Migration of nematodes over short distances is likely to be slow in the absence of strong physical forces. To our knowledge, this is the first paper ever that investigates the influence of macrofauna on nematode short-range migration.Communicated by L. Hagerman, Helsingør     

Agriculture in environmentally sensitive areas: implementing the ESA measure in Denmark

Implementation of the environmentally sensitive areas (ESA) measure in Denmark as part of the EC Structures Regulation is described. Immediate effects and the way the agreements are expected to influence landscape development are evaluated. Of the 915 designated ESAs, agreements have only been signed in two‐thirds of the areas. In those areas in which ground water protection is an objective, ‘agreement coverage has been particularly low, whereas relatively more agreements have been signed for coastal areas dominated by salt meadows. More than 3000 agreements have been made, most of them comprising existing grassland such as meadows, salt meadows and dry grasslands. Landscape protection is the most important function of the ESA measure. The effectiveness of the programme towards environmental protection and landscape improvement is evaluated as being limited. Even though a large proportion of the agreement areas, according to the farmers, would be managed in the same way without an agreement, it is not possible to make definite conclusions about the effect on landscape protection before the five‐year agreement period has ended.