BRYOBESIA JOHANNAE,A SMALL TROPICAL REPRESENTATIVE OF THE ORDER CLADOPHORALES (CHLOROPHYCEAE)1

The small and ill-known tropical chlorophyte, Brybesia johannae Weber-van Bosse, is redescribed on the basis of living material from the coral reef of Curacao, Netherlands Antilles. Additional records are given from the Canary Islands. One species, B. johannae, is recognized (including, B. cylindrocarpa Howe 1920), and this probably has a wide Atlantic and Indo-Pacific tropical distribution. Bryobesia is not related to Bryopsis and Derbesia (Caulerpales), but belongs to the Cladophorales. It appears to be a rudimentary Cladophora.     

Effects of substrata, resident conspecifics and damselfish on the settlement and recruitment of the stoplight parrotfish, Sparisoma viride

Recruitment plays an important role in the population dynamics of marine organisms and is often quantified as a surrogate for settlement. When quantified, recruitment includes settlement plus a period of time in the benthic habitat. Therefore, it is essential to determine whether post-settlement processes alter patterns established at settlement. I conducted a series of experiments on 2.0 m² patch reefs to examine the importance of pre- and post-settlement processes to the distribution and abundance of recruits of the stoplight parrotfish, Sparisoma viride, on the Tague Bay reef, St. Croix, USVI. Recruitment was higher to the coral Porites porites than to another common coral Montastrea annularis, but there was no evidence of microhabitat choice at settlement. This result, in conjunction with the examination of the size classes of recruits present on P. porites and M. annularis patch reefs in a separate experiment suggested that differences in recruitment were established after settlement. Stoplights settled in higher numbers to patch reefs that contained conspecific residents, and persistence was higher at higher recruit density. Although resident damselfish directed significant amounts of agonistic behavior towards newly stoplight recruits, damselfish presence had no effect on settlement. However, damselfish presence did reduce stoplight recruitment. These results demonstrate that both pre- and post-settlement processes influence the recruitment of stoplight parrotfish. More importantly, these results indicate that benthic processes can alter recruitment patterns from initial settlement patterns, and indicate that workers should be careful in using recruitment as a proxy for settlement.     

CO2 partial pressure controls the calcification rate of a coral community

Previous studies have demonstrated that coral and algal calcification is tightly regulated by the calcium carbonate saturation state of seawater. This parameter is likely to decrease in response to the increase of dissolved CO₂ resulting from the global increase of the partial pressure of atmospheric CO₂. We have investigated the response of a coral reef community dominated by scleractinian corals, but also including other calcifying organisms such as calcareous algae, crustaceans, gastropods and echinoderms, and kept in an open‐top mesocosm. Seawater pCO₂ was modified by manipulating the pCO₂ of air used to bubble the mesocosm. The aragonite saturation state (Ω_arag) of the seawater in the mesocosm varied between 1.3 and 5.4. Community calcification decreased as a function of increasing pCO₂ and decreasing Ω_arag. This result is in agreement with previous data collected on scleractinian corals, coralline algae and in a reef mesocosm, even though some of these studies did not manipulate CO₂ directly. Our data suggest that the rate of calcification during the last glacial maximum might have been 114% of the preindustrial rate. Moreover, using the average emission scenario (IS92a) of the Intergovernmental Panel on Climate Change, we predict that the calcification rate of scleractinian‐dominated communities may decrease by 21% between the pre‐industrial period (year 1880) and the time at which pCO₂ will double (year 2065).     

Variation in posing behaviour among fish species visiting cleaning stations

The adaptive significance of posing behaviour by fish visiting cleaning stations on a Barbadian fringing reef was investigated. The probability of a visitor being cleaned by cleaning gobies ( Elacatinus spp.) was significantly higher after posing than after failing to pose upon arrival at a cleaning station. Despite this, not all visitors posed, and there was much variation among species in tendency to pose. This interspecific variation was not related to the probability of being cleaned, either after posing or after failing to pose, nor was it related to trophic level or fish total length. The latter was true both for cross-species analyses and phylogenetically independent contrasts. A cost-benefit model is proposed to understand interspecific variation in posing behaviour, which considers both decisions by clients and by cleaners. As well as explaining the results, this may reconcile differences among anecdotal and experimental observations from previous studies.     

Coral bleaching: the winners and the losers

Sea surface temperatures were warmer throughout 1998 at Sesoko Island, Japan, than in the 10 preceding years. Temperatures peaked at 2.8 °C above average, resulting in extensive coral bleaching and subsequent coral mortality. Using random quadrat surveys, we quantitatively documented the coral community structure one year before and one year after the bleaching event. The 1998 bleaching event reduced coral species richness by 61% and reduced coral cover by 85%. Colony morphology affected bleaching vulnerability and subsequent coral mortality. Finely branched corals were most susceptible, while massive and encrusting colonies survived. Most heavily impacted were the branched Acropora and pocilloporid corals, some of which showed local extinction. We suggest two hypotheses whose synergistic effect may partially explain observed mortality patterns (i.e. preferential survival of thick-tissued species, and shape-dependent differences in colony mass-transfer efficiency). A community-structural shift occurred on Okinawan reefs, resulting in an increase in the relative abundance of massive and encrusting coral species.     

Cannabinoids inhibit zebra mussel (Dreissena polymorpha) byssal attachment: a potentially green antifouling technology

Man-made submerged structures, including shipwrecks, offering substrata for fouling organisms and fish, have been classified secondarily as artificial reefs (ARs). The current approach in AR design is that of low-profile structures placed on the seabed and attempting to mimic natural reef (NR) communities with the aim of mitigating degraded marine ecosystems. To examine the validity of this concept, a long-term comparison of the developing AR fouling communities to those of nearby NRs is required. A survey of the fouling reefal organisms was conducted on seven shipwrecks (Red Sea, Egypt), comprising three young (ca 20 years old) and four old (?>?100 years old) unplanned ARs, in comparison to nearby NR communities. The hypothesis tested was that the age of the ARs shapes the structure of their fouling coral communities. The results demonstrated distinct differences between ARs and NRs and between young and old ARs. While the species composition on ARs may resemble that of NRs after approximately 20 years, obtaining a similar extent of coral cover may require a full century. Moreover, differences in structural features between ARs and NRs may lead to differences in species composition that persist even after 100 years.     

An introduction to the biogeochemical cycling of calcium and substitutive strontium in living coral reef mesocosms

The coral reef mesocosms designed by the Smithsonian Institution's Dr. Walter Adey, his Marine System Laboratory personnel, and staff members of the Pittsburgh Aqua-Zoo simulate most of the physical, chemical, and biological parameters found in natural Caribbean coral reefs. After developing the mesocosm in Pittsburgh, an evaluation and comparison between natural reef seawater sources and closed mesocosm seawater conditions indicated that an additional parameter should be investigated. It was hypothesized that, given time, the aragonite- and calcite (CaCO₃ crystal forms)-producing organisms in the closed mesocosms could deplete the seawater of available Ca²⁺ and substitutive Sr²⁺. Atomic absorption spectrophotometry was utilized to determine concentrations in the seawater over time. Results showed a substantial reduction in dissolved Ca and Sr in the mesocosm after approximately two years. Dissolved aragonitic Halimeda algae parts were put into the system for replacive purposes. In terms of the biogeochemical cycling of Ca²⁺ and Sr²⁺, the coral reef mesocosm organisms behaved similarly to natural reefs, which have a constant supply of dissolved Ca²⁺ and Sr²⁺. Further research utilizing radiolabeled sources of Ca²⁺, Sr²⁺, and Mg²⁺, in conjunction with in vivo scanning electron microscopy (SEM) and growth increment studies, are recommended for determining the exact biogeochemical pathways for these elements in coral reefs, and to quantify growth parameters. © 1993 Wiley-Liss, Inc.