Soft bottom macrofauna (benthos) in the deep-sea is influenced by a wide variety of environmental factors. In this review I will shortly evaluate the importance of some factors on different parameters of the benthos. Studies on macrobenthic communities from the Skagerrak in the north to the Iberian continental margin in the south are compared. Not one factor can be indicated as the factor controlling the benthic fauna at the European continental margin. Nearly all factors are coupled and directly or indirectly influencing the benthic community, indicating the complexity of this ecosystem. The overall pattern in decrease in total density and biomass with increasing water depth is mainly determined by the food input, but special topographic structures can highly influence this pattern. In canyons very high densities were found, whereas on very steep slopes and on sea mounts densities were very low. Not only quantity, but also quality, reliability and source of the food are important for the benthos. High flow velocities can resuspend the organic matter again and make it more available for suspension-feeders, whereas the fauna can change the flow and actively capture food that otherwise would pass. Extreme flow conditions can periodically disturb the fauna, allowing only deep living fauna to maintain and favor rapid colonizers, whereas a stable environment allows the development of a ’climax’ community in which biotic interactions become very important. As we still know only very little about the biology of the deep-sea fauna, we also can say very little about the elasticity and carrying capacity of this remote, but probably very important ecosystem. The highly complex nature of the continental margins, with strong difference in appearance, steep slopes with rocky outcrops, smooth sedimental plateaus, bights, troughs, seamounts and canyons, results in high local variability. We need to know more about the actual life-history strategies, feeding-types and mobility of the deep-sea fauna. Long-term observations and experiments would give an idea about the reactions of the benthos on different environmental events, as changes in flow velocities, food falls, sedimentation, even pollution and disturbances, but also reactions on biological events, as predators, competitors, etc. DNA- analyses can give information about evolution and distribution of the fauna and probably allow us a better understanding of biodiversity.
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- Factors Controlling Soft Bottom Macrofauna Along and Across European Continental Margins
E. C. Flach
- Springer Berlin Heidelberg