Faunal responses to turbidity in a man-modified bay (Bilbao, Spain)

摘要

The relationship between rocky shore faunal assemblages and measured environmental variables in a small bay (Bilbao, Spain) affected by large anthropogenic interferences were examined using multivariate statistical techniques (CANOCO, PRIMER). Redundancy ana- lysis (RDA), with forward selection of environmental variables and associated Monte Carlo permutation tests, suggested that total suspension solids (TSSs) and salinity (Sals) at the water surface made significant ( < 0.05) contributions to explaining the variation in the investigated faunal assemblages. Alternatively, the BIO-ENV analysis selected a subset of three environ- mental variables, related to turbidity, as the best explanatory variables. A constrained RDA with TSSs as the only explanatory variable revealed that turbidity was a strong variable, and accounted for a statistically significant proportion of the variance in the faunal data set. Further analyses of faunal data using a smaller subset of 14 top dominant taxa produced spatial patterns as clearly as the analysis with the full species data set (63 species). This indi- cated that nearly 75/100 of the taxonomic information could be deemed redundant for the purposes of this study. In conclusion, the weight of evidence suggests that turbidity, mainly from estuarine runoff, is causing a severe stress to the hard-bottom faunal assemblages.