We examined the coupling between the release of nauplii in Sanibalaruu balanoides and ... In temperate and high latitudes, the spring phytoplankton bloom is of.
Journal of Plankton Research Vol.13 no.3 pp.561-571, 1991
Coupling of nauplii release in barnacles with phytoplankton blooms: a parallel strategy to that of spawning in urchins and mussels Michel Starr1-2, John H.Himmelman1 and Jean-Claude Therriault2 'GIROQ (Groupe Interuniversitaire de recherche ocianographique du Quibec) and Dipartement de biologie, Universiti Laval, Quibec, P.Q., G1K 7P4 and 2 Institut Maurice-Lamontagne, Ministere des PSches et des Ocians, Division d'octanographie biologique, C.P. 1000, Mont-Joli, P.Q., Canada G5H 3Z4
Introduction Since food availability is likely to influence larval success in marine benthic invertebrates, reproductive cycles should be coordinated so as to ensure that the larvae will encounter an abundant supply of phytoplankton, their primary source of food. In temperate and high latitudes, the spring phytoplankton bloom is of short duration and its timing can vary markedly from year to year. This, combined with a relatively fixed spawning period, could explain interannual variations in recruitment. Fisheries biologists refer to this concept as the matchmismatch theory (Cushing, 1975). Alternatively, to reduce the effect of stochastic variations in the environment, invertebrates may have evolved mechanisms that couple larval production with phytoplankton abundance. An example is the direct coupling of the spawning of green sea urchins (Strongylocentrotus droebachiensis O.F.Muller) and blue mussels (Mytilus edulis L.) with the spring phytoplankton outburst (Starr et al., 1990). These invertebrates spawn when they detect a heat-stable metabolite released by various species of phytoplankton. The occurrence of this mechanism in two widely separated invertebrate phyla indicates that direct coupling of spawning with phytoplankton abundance, through detection of released substances, could be a widespread phenomenon. An analogous situation could be the release of pelagic nauplii larvae by barnacles during phytoplankton blooms. For example, the embryos of Semibalanus balanoides are retained for a considerable time once they have reached © Oxford University Press
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Abstract. We examined the coupling between the release of nauplii in Sanibalaruu balanoides and phytoplankton blooms, and compared it with the mechanism synchronizing spawning with phytoplankton abundance in green sea urchins (Strongylocentrotus droebachiensis) and blue mussels (Mytilus cdulis). Close contact with phytoplankton cells is required to stimulate the release of nauphi in Scmibalanus, whereas spawning in urchins and mussels is triggered by an extracellular metabolite of phytoplankton. The response is concentration dependent and positively correlated with the frequency of moulting The moulting rate in Senubalanus is reported to be directly correlated with food intake and thus larval release should be proportional to feeding activity. The release of Scmibalanus nauplii is more strongly stimulated by the diatom Skeletonema costatum than by Phaeodactylum tncomutum, whereas the highest response is obtained in treatments with nauplii of Artemia salina. We suggest that these differences are related to size of the planktonic particles (Anemia nauplii > Skeletonema > Phaeodactylum). Exposure to air, as occurs in the interbdal zone, does not influence significantly larval release Larval release in other Crustacea may similarly be coupled to phytoplankton abundance.
M.Starr, J.H.HImmdman and J.-C.Tberriault
Method
Adult S.balanoides attached to mussel shells (M.edulis) were collected in Passamaquoddy Bay (St Andrews, New Brunswick) in early spring when nearly all individuals contained fully developed embryos. Prior to the experiments, the barnacles were kept in holding tanks supplied with recirculated sea water without phytoplankton, at a temperature of 5-6°C, a salinity of 21-27%o, and under a 15:9 h light:dark photoperiod (cool white fluorescent lighting). For each experiment, 30 barnacles (each on cleaned portions of mussel shell) were exposed for 7 days to varying conditions in glass bowls containing 250 ml of test medium (see below). Daily, we changed the medium and noted whether nauplii were present. Virtually no mortality ( 0.05) occurred when barnacles were exposed to higher air temperatures (24-27°C; expt 5). Larval release increased with increasing concentration of S.costatum in the experiments in which barnacles were continuously immersed in sea water (Figure 1A). Thus, hatching increased from a =20% response at a concentration of 1 x 107 cells I"1 (equivalent to 5.9 mg Chla m"3, SD = 0.9) to a =80% response at 40 x 107 cells I"1 (equivalent to 238 mg Chla m~3, SD = 36.0). A larval release of
