Responses of a hydroid to surface water samples from the River Tamar and Plymouth Sound in relation to metal concentrations

Abstract

The River Tamar and its tributaries drain a highly metalliferous area; and increased metal levels in river water might be expected to affect biological water quality in the estuary. In order to detect possible effects we have used sensitive responses to stress of the hydroid Campanularia flexuosa as an index of quality of water samples from the River Tamar, Plymouth Sound and Cattewater. No water samples caused inhibition of colonial growth rate, but in each experiment there were significant variations in other more sensitive responses. It is these variations that we have related to metal distributions, although of the metals measured, only copper and cadmium occasionally occur in concentrations that could be biologically significant, and at the same time show any correlation with the hydroid responses. The limitation of the survey to water of relatively high salinity does not permit a firm conclusion about the origin of these metals, but there are some indications that local inputs may be important.