Recent studies on the ecology of marine larvae suggest that retention near coastal areas and self-recruitment are probably much more common than previously thought. In light of this, the advective potential of pelagic stages can be partially determined by the timing of propagule release. We sampled the upper-shore levels of a subtropical coastline in southeastern Brazil to examine the temporal patterns of propagule release for the common barnacle Chthamalus bisinuatus and the periwinkle Nodilittorina lineolata. The release timing in both species was very consistent between sites a few kilometers apart. Barnacles released nauplii in a rhythmic pattern, mostly coinciding with neap tides, when the speed of tidal currents was lowest. There was no variation in propagule release in relation to diel or flood -ebb tidal cycles. Periwinkles released propagules in a very irregular pattern, which remarkably matched a time series of wave heights. Egg capsules were released during periods of rough seas, when onshore surface currents were expected to prevail. Eggs were released mostly during ebb tides, and there was no diel variation. Propagule release rhythms are usually viewed as a means to ensure fast offshore advection, thus avoiding presumed hazardous conditions for larvae. However, propagule release strategies in these upper-shore species would more likely contribute to the retention of offspring close to parental stocks. KEY WORDS: Reproductive timing · Propagule retention · Rocky shoresResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 414: 155-165, 2010 gan 1995). In the case of intertidal brachyuran crabs, an extensive dataset suggests that hatching is timed with different environmental cycles, so that optimal release is expected to take place during spring tides, at nocturnal ebbing periods, ensuring a fast offshore advection to a habitat patch where predation risk is lower (Forward 1987, Morgan 1995. By this means, larvae may easily be transported off coastal retention zones. However, intertidal crabs are mobile animals which can undertake tidal excursions prior to hatching and larval development is relatively long, usually lasting from 3 to 10 wk (Hines 1986). In rocky shores, the most abundant organisms are sessile or sedentary, and their larvae develop relatively faster. Many of these animals also respond to environmental cues, which are far less predictable. For instance, phytoplankton blooms were shown to trigger spawning and larval release events in different marine invertebrates (Barnes 1962, Starr et al. 1990, and mechanical stimulation, which may simulate wave action, is frequently used to obtain gametes in mussels and polychaetes in the laboratory (e.g. Young 1945, Eckelbarger 1976. In such cases, ripe individuals must be capable of retaining their fully developed eggs until they perceive release-inducing stimuli. Because these environmental cues are highly stochastic, they are also very difficult to anticipate. Endogenous control in such species...
Despite its small area, Araçá Bay (AB) holds cultural, historical, and economic value and displays great benthic biodiversity. Thus, it is crucial to monitor its environmental health, including knowing the main groups of phytoplankton and their temporal variability. The shallow waters of Araçá Bay are continuously modified by the complex hydrography of the adjacent São Sebastião channel (SSC), challenging standard experimental designs for phytoplankton collection. Here we report changes in phytoplankton composition at intervals of five to six weeks from September 2013 to August 2014 in both Araçá Bay and SSC. Samples were collected twice daily for three consecutive days to increase taxonomic resolution. Our goal was to provide an inventory of species occurrences to aid future public policies and environmental management of the area. Analyses revealed high species richness and 166 different phytoplankton taxa. Diatoms and dinoflagellates were always numerically dominant, but taxa occurrence changed markedly. Diatoms of the genera Pseudo-nitzschia were abundant during spring and summer concurrently to signatures of South Atlantic Central Water in the SSC, while Thalassiosira occurred when waters displayed relatively lower salinity. The inventory demonstrated several potentially harmful species of microalgae and cyanobacteria, strongly suggesting investments in monitoring programs in this area that currently experience an increase in population.
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