Abstract
SUMMARY: Qualitative and quantitative differences in species composition of meiobenthic communities illustrate the differences among various taxonomic assemblages in the Balearic Islands (Western Mediterranean) analysed by means of multivariate analysis. Average densities ranged between 1000 and 4000 ind·10cm -2 , and are in the same range as previously reported from other shallow Mediterranean areas. The dominant meiofaunal taxa were Nematoda (range 40 to 75%), Turbellaria (5-47%) and Copepoda (2-14%), while other meiofaunal groups (Tardigrada and Rotifera) were only represented by approximately 5% of the total abundance. The dominant nematode families were Desmodoridae, Chromadoridae and Xyalidae. The meiofaunal communities showed little variation among locations. Moreover, small-scale heterogeneity does not seem to affect nematode distribution as shown by the high similarity between replicates in the multivariate analysis.
Highlights
The establishment of the first Spanish MarineNational Park of Cabrera (Balearic Islands) in 1991 provided a good scenario for base-line studies of indicator species, especially regarding benthic organisms
Many natural environmental factors such as water depth and sediment granulometry, oxygenation of the sediment, and biotic interactions modify community structure, it is not easy to separate natural from anthropogenic effects
Sediment parameters, redox-potential discontinuity layer (RPD), depth, temperature of sediment and water were considered as environmental factors
Summary
The establishment of the first Spanish MarineNational Park of Cabrera (Balearic Islands) in 1991 provided a good scenario for base-line studies of indicator species, especially regarding benthic organisms. Nematodes are more tolerant of detrimental conditions than most other groups and have been found to survive as the only group of higher animals in very polluted waters. We selected this taxocene to study the level of anthropogenic influence by comparing stations from a pristine protected area (Cabrera) versus a disturbed location (Mallorca). Many natural environmental factors such as water depth and sediment granulometry, oxygenation of the sediment, and biotic interactions modify community structure, it is not easy to separate natural from anthropogenic effects. Measurement of the community structure usually has limitations in discriminating between the effects of chemical stress, natural physical disturbances, pollution and biological disturbance (Gray, 1971)
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