Abstract. A study of heavy metals in estuarine sediments and foraminiferal tests along with foraminiferal distributions from Southampton Water indicates that:

a) heavy metals have a marked effect upon foraminiferid distribution. Some species are able to tolerate pollution and their relative abundance increases at discharge points, whereas other species develop test deformities. Investigation of cores show that no deformed specimens exist within sediments prior to the introduction of pollution.

b) deformed specimens contain higher levels of elements such as Cu and Zn than non-deformed specimens. This indicates that heavy metals may be responsible for the abnormalities within foraminiferid tests. Culture experiments support this hypothesis. Specimens of Ammonia beccarii (Linné) developed abnormal chambers over a period of 12 weeks within a culture medium containing 10–20ppb of Cu.