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Among the Anthozoa collected in recent years from Croatian waters, two species of Actiniaria and eight species of Scleractinia (from 21 stations) deserve special mention. Here we document the first records in the Adriatic Sea of the actiniarians Alicia mirabilis and Halcampoides purpurea and the scleractinians Coenocyathus cylindricus, Spbenotrochus andrewianus and Balanophyllia regia, while the previously uncertain occurrence in this part of the Mediterranean Sea is confirmed for the first time for the scleractinians Caryophyllia cyathus, Coenocyathus anthophyllites, Dendrophyllia ramea and Astroides calycularis. Guynia annulata, previously recorded in the Adriatic only from the southern Italian coast near Bari, has been found on the Croatian coast as far north as Prvic Island.

The diversity and distribution of bryozoans have been surveyed at two localities, Cape Struga on Lastovo Island (South Adriatic) and Cape Š ilo on Prvić Island near Senj (North Adriatic), with similar characteristics of topography and exposure but markedly different sea temperature conditions. Continuous measurements over one year have shown that temperature conditions differ in two aspects. First, the annual range of temperature is much larger in the North. Second, in the South during summer, marine life within the thermocline layer is exposed to large high-frequency temperature oscillations, partly due to an internal diurnal tide, a phenomenon recorded for the first time in the Adriatic. Altogether, 78 species have been recorded, 57 in Lastovo and 50 in Prvić, and 29 in both localities. The comparison of mean zooid lengths of 14 bryozoan species occurring at both localities indicates no consistent difference in zooid size between northern and southern sites. Seventeen bryozoan species have been recorded in the Eastern Adriatic Sea for the first time.

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Abstract. In late summer and early autumn of 1989 benthic mortality in the upper part of Krka estuary extended from the Skradinski buk waterfalls to approximately 5 km downstream. Dead benthic organisms were found on the bottom at depths of up to 4.5 m. During August, a freshwater phytoplankton bloom was recorded in Visovac lake (which supplies the Skradinski buk waterfalls). The green tide in the lake was composed of up to 11.9 million cells. 1‐‐1, predominantly of Synedra acus and Dinobtyon sertularia. At that time the maximal total inflow of phytoplankton cells through the waterfalls was approx. 0.41 S‐I (38000 1. d‐1). Cells of these two species died after reaching the salt wedge and the cummulative effect of their decomposition apparently caused an oxygen demand sufficient enough to trigger the benthic mortality. Due to the water mass dynamics, the spreading of mortality downstream was slow (from August to October, approx. 5 km). Certain benthic fishes (like Gobius sp.) were observed on the bottom of the affected area in mid‐October 1989.