The amphipod crustacean Talitrus saltator is an established, easily accessible, biomonitor of trace metal bioavailabilities in coastal waters. We have carried out a geographically widespread collection of T. saltator from European shores, stretching from the north-west Atlantic through the Baltic to the Mediterranean. A primary aim of the work was to establish a database of accumulated trace metal concentrations (Cd, Cr, Cu, Fe, Mn and Zn) in this biomonitor. Statistical analysis has shown significant geographical differences in the bioavailabilities of all the metals, the most distinct being copper, iron and manganese. It has proved possible to identify unusually high accumulated concentrations of Cd, Cr, Cu, Fe, Mn and Zn in this biomonitor, indicative of high metal bioavailability at a particular site. These may serve as reference points for future biomonitoring programmes seeking to identify metal contamination in coastal waters.

The distribution of Orchestia gammarellus (Pallas) and Platorchestia platensis (Kröyer) (Amphipoda: Talitridae) along the Swedish coast was studied in 1995–96. The latter species had expanded its distribution since the 1960s both on the Swedish west coast and in the Baltic Sea. The survival of the two species in salinities between 0·5 and 51 was investigated at 12°C. Platorchestia platensis was found to endure lower salinities better than Orchestia gammarellus with reversed conditions in higher salinities. This would imply that the inner distributional limit for Platorchestia platensis in the Baltic has not yet been reached, or that other environmental factors are operating. Southerly currents which dominate for most of the year also hamper dispersal northward along the Swedish Baltic coast. The life-cycle of the two species was studied for 2 years both in allopatric and sympatric populations in the Baltic Sea. In the locality with sympatric populations the dominance of Platorchestia platensis had increased from tenths of a percent in an earlier study (1991) to 90–95% in 1997. The dominance in 1997 was significantly higher than in 1996. The breeding cycle of both species began simultaneously in late May but ended in August/September in Orchestia gammarellus, whereas gravid female Platorchestia platensis were found as late as November/December. In the latter species the generation that hatched in early summer became mature and reproduced the same autumn. Fecundity values were positively correlated with female body size and the maximum egg numbers were among the highest recorded for both species. Thus salinity does not affect brood size.

The responses to a white directional light and a black stripe covering 60° of the horizon were studied in two Swedish populations of the amphipod species Talitrus saltator (Montagu, 1808) and Talorchesia deshayesii (Audoin, 1826) from two beaches on the southern Baltic Sea. Adult individuals were caught in the field and tested in constant laboratory conditions in order to investigate the possible variation of the responses during the 24h cycle, and then to compare their behaviour with that of the Atlantic and Mediterranean populations, already known in literature. Previous studies explained the observed differences between Atlantic and Mediterranean populations with the differences in tidal excursions and did not take into account the different climatic conditions. The Baltic coasts, like those of the Italian Mediterranean, are not tidal and present prevalent low mean temperatures and high humidity throughout the year like those of Britain. The response to the artificial white light remained photopositive throughout the 24h cycle in both the species sampled, although its intensity was lower during the day than at night in Talitrus saltator. The response to the black stripe showed an inversion from positive to negative during the 24h cycle, the animals being directed towards the black stripe during the day and away from it at night; this response was more intense and clear cut in Talorchestia deshayesii than inTalitrus saltator . The pattern of response to the black stripe shown by the Swedish talitrids, differed from both that of the British and Italian populations, and was interpreted as a basic response related to the diel rhythm of emergence and burrowing.