Propagule release and recruitment in Porphyra perforata (Rhodophyta) from Baja California, Mexico

Abstract

This study determined the effect of irradiance, temperature and photoperiod on the release of zygotospores and spermatia in Porphyra perforata from the Pacific coast of Baja California, Mexico. Reproductive blades were placed under controlled conditions of irradiance (5, 75, 150 and 300 μmol photons m−2 s−1), photoperiod [8:16; 12:12 and 16:8 light:dark (L:D)] and temperature (15, 18, 21 and 25°C). Peak zygotospore release occurred at 15–18°C and photoperiod of 16:8 L:D. Reproductive tissue released between 60% and 90% of zygotospores and spermatia during the first 10 days of incubation at 50 μmol photons m−2 s−1, 18°C and photoperiod of 16:8 L:D. Maximum zygotospore and spermatium release occurred in tissue collected between June and November. The number of zygotospores released was approximately 40% greater than that of spermatia (2.7×106 vs. 1.6×106 g FW−1 d−1). The reproductive foliar phase was observed throughout the year, but only thalli collected from April to January released zygotospores and spermatia. Collectively, the results suggest that low temperature, as observed in upwelling events, may induce high zygotospore and spermatium release during summer months.