ABSTRACT: The utility of analyses of abundance data at taxonomic levels higher than species, in the interpretation of results from marine surveys, is examined using nematode and macrofauna data from a sublittoral dredgings disposal site and from an intertidal site known to be influenced by heavy metal pollution. A more objective approach than has hitherto been the case in comparisons of multivariate patterns from data at different taxonomic levels is taken, and the concept of a 'second-stage' multidimensional scaling (MDS), in which rank correlations between pairs of similarity matrices themselves become the elements of a second similarity matrix, an ordination of which gives a summary of the conclusions, is introduced. It is shown that analyses of both the sublittoral and intertidal estuarine nematode communities are robust to aggregation to the level of genus, but further aggregation alters the perceived pattern of impact. Aggregation of macrofauna abundances to families has only a small effect on analyses of the sublittoral community, and none on analyses of the less diverse intertidal macrofauna. Aggregating macrofauna data to phyla has some effect on consequent analyses in both situations. Whichever component of the benthos is examined, and at whatever taxonomic level the analyses are carried out, interpretable results are possible, especially if the pattern of community change is marked, as in both surveys examined in this study.

KEY WORDS: Nematodes . Macrofauna . Taxonomic levels . Community structure . Rank correlations

Published in MEPS Vol. 127 (1995) on November 2
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1995