Analysis of the Spatial Variability in Abundance and Age Structure of 2 Infaunal Bivalves, Cerastoderma-Edule and C-Lamarcki, Using Hierarchical Sampling Programs

• Spatial variability in abundance and age distribution of 2 infaunal bivalves, Cerastoderma edule (Linnaeus, 1785) and C. lamarcki (Reeve, 1845), were quantified using hierarchical sampling programs. The scales investigated ranged between 100 and 10(5) m. Analyses of variance revealed significant variability in abundance among sites within bays (similar to 100 m apart) for both species and also among bays (similar to 1 km apart) for C. lamarcki. Mean age varied at several spatial scales. For both species, however, the scale contributing most to the variation was bays, which provided about 40 % of the total variation for each species. Randomization procedures were used to test the generality of previous observations of non-random distributions of year classes (namely number of year classes and dominance by single year classes). These analyses showed that for both species a spatial unit contained significantly fewer year classes and the most abundant year class was significantly more abundant than expected by chance. These results were consistent for all spatial scales except among plots (similar to 10(1) m apart) in C. lamarcki. The necessity to assess spatial patterns at a wide range of spatial scales is emphasized. Potentially important processes (focusing on larval supply and recruitment) which generate the observed patterns and general implications of spatial variability are discussed.

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NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

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