Inhibitory effect of phenolic compounds and marine bacteria on larval settlement of the barnacle Balanus amphitrite amphitrite darwin
Titel:
Inhibitory effect of phenolic compounds and marine bacteria on larval settlement of the barnacle Balanus amphitrite amphitrite darwin
Auteur:
Lau, Stanley C. K. Qian, Pei-Yuan
Verschenen in:
Biofouling
Paginering:
Jaargang 16 (2000) nr. 1 pagina's 47-58
Jaar:
2000-10
Inhoud:
This study examined the inhibitory effect of 3 phenolic compounds and 12 strains of marine bacteria on the larval settlement of Balanus amphitrite amphitrite. The phenolic compounds used were phlorotannins, phloroglucinol and tannic acid. Phlorotannins are polymers of phloroglucinol (1,3,5-trihydroxybenzene) known only from brown algae. Tannic acid, which exists in terrestrial plants, is composed of oligomers of phloroglucinol attached to a sugar molecule. The bacterial strains used were isolated from a natural biofilm. The following were investigated: 1) the toxicity of the phenolic compounds to B. a. amphirite in three different larval stages, viz. nauplius II, nauplius V and cyprid; 2) the potency of the compounds as inhibitors of larval settlement and the possible mechanism involved in settlement inhibition; and 3) the effects of the bacteria on larval settlement. The level of toxicity of the phenolic compounds varied widely for the larvae. Phlorotannins were most toxic, having LC50 values ranging from 9.47 to 40.35 μg ml-1; phloroglucinol was least toxic, having LC50 values of 235.12 to 368.28 μg ml-1. In general, nauplii were more sensitive to the toxicity of the phenolic compounds than cyprids. The greater sensitivity of nauplii may be due to their active feeding behavior, which exposes the interior of their bodies to the compounds by active intake. Phloroglucinol was the most potent settlement inhibitor, having an EC50 value of 0.02 μg ml-1. Phlorotannins and tannic acid had EC50 values of 1.90 μg ml-1 and 14.05 μg ml-1, respectively. Phloroglucinol appeared to inhibit larval settlement through a relatively non-toxic mechanism as its LC50 value was four orders of magnitude higher than its EC50 value. The high potency of phloroglucinol indicates that a simple constituent of a complex natural compound can be more effective than the natural compound itself. Larval settlement bioassays with monospecies bacterial films indicated that some of the bacterial species were inhibitory to larval settlement while the others showed no effect. None of the bacterial strains in this study induced larval settlement.
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