Combined effects of temperature and salinity on larval development and attachment of the subtidal barnacle Balanus trigonus Darwin

The combined effects of temperature and salinity on larval development and attachment of Balanus trigonus Darwin (Cirripedia, Balanidae) was examined under controlled laboratory conditions. Whilst larval survivorship was not affected (> 70%), the duration of larval development was significantly affected by temperature and salinity. The effect of temperature was comparatively stronger than that of salinity. The majority of nauplius 11 larvae metamorphosed into cypris stage after 4-5 and 10-11 days at 28degreesC (22-34parts per thousand) and 18degreesC (22-34parts per thousand), respectively. Temperature, salinity and the duration of assay had a significant effect on cypris attachment with significant interaction among these main effects. Maximum (> 80% in 6 days) and minimum percent attachment (0% in 6 days) on polystyrene surfaces were observed at 24degreesC (34parts per thousand) and 18degreesC (22parts per thousand), respectively. At high temperature (28 degreesC) and low salinity (22-26parts per thousand), larvae rapidly (4 days) developed into cyprids, but less than 33% attached. These results suggest that low larval attachment rates may lead to the low recruitment of B. trigonus in Hong Kong waters during summer when the water temperature is high (about 28 degreesC) and salinity is low ( < 26parts per thousand). (C) 2002 Elsevier Science B.V. All fights reserved.