Disturbances of nematodes

Nematode disturbances

Sediment movement, erosion and deposition are natural processes, and benthic organisms have adapted to such disturbances. Man-made physical disturbances (e.g., beam trawling, dredged material disposal, coastal development) occur at a much larger scale, rate and magnitude and may exceed the adaptive capacity of sediment-inhabiting organisms.

Different disturbances in the same region

MarBEF researchers on the MANUELA project compiled and analysed an extensive database of experimental and observational studies to investigate the effects of physical disturbances in sediments on nematodes. Some measures of diversity decreased with increasing level of disturbance regardless of the disturbance type. Others, however, were more variable and depended on the nature and origin of the disturbance. Hence, there is no consistent effect of physical disturbances on nematode assemblages.

In addition, it was shown that man-induced changes are intrinsically different from those of natural origin. Nematode assemblages were more similar after being subjected to high-intensity disturbances, even if they originated from geographically distinct areas.

Similar disturbances in different regions

However, it is largely unknown whether nematodes respond in a similar way to the same disturbance, independently from the geographical location. In this experiment, MANUELA researchers mimicked the effect of an increased amount and frequency of rainfall on sandy beaches from four different locations in Europe. Experimental beaches were located in Poland (Baltic Sea), Belgium (North Sea), Portugal (NE Atlantic Ocean) and Crete (Mediterranean Sea). Beaches covered a range of tidal regimes (microtidal to macrotidal), salinity brackish to marine) and temperature (northsouth gradient) environments. The frequent addition of freshwater to the Baltic beach did not affect salinity in the sand, due to the low natural salinity. All other beaches showed modified salinity profiles. All nematode assemblages changed significantly as a consequence of the experimental treatment but the underlying mechanisms were different. Nematodes do not show a universal response to disturbances associated with climate change. This shows that there is no universal response of nematode assemblages to disturbances and that changes occurring at a global scale will have different impacts in different localities. The adaptation of the receiving community to the frequently-changing environment largely determines the effect of the increase in rainfall.

MARBEF has examined impacts of disturbance at a truly European scale - collating, generating and comparing evidence from a wide range of disturbance types, habitats, taxa, places and times. Its researchers have worked to improve methodologies for data collection, archiving and analysis and have completed a substantial body of original research. New evidence has shown that the impacts of key disturbances can vary substantially depending on the environmental context in which they act and are not necessarily predictable based on existing knowledge. The specific and general findings of the work can be applied directly to the implementation of the existing Water Framework Directive and the new Marine Strategy Framework Directive. Effective decision-support tools must incorporate empirically derived insight into the impacts of key disturbances in specific regions and localities. The databases generated during MARBEF will provide a lasting legacy and can be built upon and interrogated repeatedly in future with great potential to improve our understanding of variation in impacts of disturbance on marine ecosystems and our approaches to managing marine environments.