Animal-Sediment Relations in Shallow Water Benthic Communities

Johnson, R

Ninety benthic samples were used to study animal-sediment relations in Tomales Bay, California. While most of the benthic species studied were found more often in a particular type of substrate, individuals of such species were occasionally found in other substrates. There is a striking tendency for species occurring outside of their characteristic environment to be associated with the most diverse assemblages of the foreign substrate. Species low in the order of succession are those species that are found more frequently on other substrates. These phenomena are explained in terms of environmental stability. The concepts involved suggest a means of predicting the sequence of faunal changes following the alteration of the substrate. A commonly used index of diversity (Brillouin's equation) was found to be very sensitive to the occurrence of two ubiquitous species. A high correlation was obtained between the number of species and the index of diversity when the two ubiquitous species were not considered. The benthic environment of Tomales Bay is gradational and faunal variation is correspondingly continuous. Under such circumstances, the animal-sediment and diversity relations described are probably more apparent than in areas where the slope of the environmental gradient is greater. Similar relations would be expected, however, in the deep sea and in continuous stratigraphic sequences in the geologic record.

Animal-Sediment Relations in Shallow Water Benthic Communities

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