Inhibition of Larval Survival and Metamorphosis of the Sea Urchin Strongylocentrotus intermedius by 2,4-dibromophenol and 2,4,6-tribromophenol

Abstract

We examined the inhibitory effects of 2,4-dibromophenol (DBP) and 2,4,6-tribromophenol (TBP), which are released by the kelps Eisenia bicyclis and Ecklonia kurome, on survival and metamorphosis of larvae of the sea urchin Strongylocentrotus intermedius. Almost all larvae were fallen in the presence of 5 and 10 ppm, and died in the presence of 20 and 50 ppm DBP and TBP after 24 h, indicating that DBP and TBP have strong toxicity for the larvae of S. intermedius. The percentage of larvae that underwent metamorphosis in filtered seawater after 1 h of exposure to a one-half dilution of saturated dibromomethane solution (~60 ppm) as a chemical inducer reached 43% after 1 h and rose to 75% after 24 h. However, the percentage of metamorphosed larvae in filtered seawater containing 10 ppm DBP was reduced markedly to 25-34% within 24 h, and that in filtered seawater containing 10 ppm and 20 ppm TBP was reduced markedly to 24-34% and 4-10%, respectively, within 24 h. All larvae exposed to 20 ppm and 50 ppm DBP and to 50 ppm TBP died after 1 h. These findings suggest that DBP and TBP have a strong inhibitory effect on larval survival and metamorphosis for S. intermedius. These bromophenols may play a important role in the chemical defense of kelps against sea urchin recruitment in the field.