The Structure of Coral Communities at Hurghada in the Northern Red Sea

Abstract. The community structure of hard and soft corals, with an emphasis on hard corals, was determined by means of line-transects on 9 on-and off-shore reefs of different type and different wave exposure in the Northern Red Sea near Hurghada in Egypt. Coral communities were found to differentiate along a horizontal wind- and wave-exposure gradient. Exposed communities were dominated by Acropora species, sheltered communities by Porites species, and semi-exposed communities by Millepora species. Also, vertical within-reef zonations following a depth gradient were observed; these were unique for each exposure-determined community type. Average transect diversity was highest on semi-exposed reefs, lowest on sheltered reefs. Reef slopes were more diverse than other reef zones. The observed community structure was compared with data from the literature, and widely distributed, roughly comparable hard and soft coral communities were identified.     

硇洲岛大型海藻群落的季节演替*

2011年4月至2012年1月对硇洲岛潮间带大型海藻进行了周年的季节调查, 结果表明, 调查海域大型海藻共有64种。其中褐藻门15种, 占总种类数的23.44%; 红藻门28种, 占总种类数的43.75%; 绿藻门20种, 占总种类数的31.25%; 蓝藻门1种, 占总种类数的1.56%。其种类数春季最多, 共43种; 夏季24种; 秋季29种; 冬季31种。有9个物种为4个季节共有种, 有14个物种为3个季节共有种。各季节间共有种类数为12~26种, 季节间种类更替率为0.42~0.78, 春夏季种类更替率最高, 秋冬季种类更替率最低。优势种共有13种, 仅拟鸡毛菜Pterocladiella capillacea为全年优势种, 而半叶马尾藻Sargassum hemiphyllum和小珊瑚藻Corallina pilulifera为3个季节共有优势种。调查海域大型海藻生物量季节变化明显, 平均生物量春季最高, 冬季次之, 夏季最低。不同物种其垂直分带明显, 从高潮区往低潮区种类数不断增多; 生物量也是从高潮区往低潮区逐渐增大。物种多样性指数变化范围为0.03~2.33, 年均值为1.10; 均匀度变化范围为0.01~0.70, 年均值为0.36; 种类丰富度指数变化范围为0.15~1.65, 年均值为0.72; 辛普森优势度指数变化范围为0.01~0.78, 年均值为0.39。各大型海藻含水率变化范围在51.92%~97.52%, 平均值为85.21%; 总有机碳含量变化范围在4.34%~42.06%, 平均为27.99%。相关性分析发现, 调查海域大型海藻生物量与无机氮(DIN)呈显著负相关, 相关系数为0.49(P＜0.05), 与其他环境因子的相关性不明显。在大型海藻生长旺盛的冬春季, 海水中的无机氮(DIN)含量最低, 与其他自然海域冬季营养盐积累规律显著不同。     

Low-Tide Exposure of Sponges in a Caribbean Mangrove Community

Abstract. Sponges on subtidal red-mangrove prop roots may become exposed to air many times per year during very low tides. Full exposure is stressful and potentially fatal, particularly if occurring in full sun. Large root sponges show distinct species zonation between mean low water and -0.5 m. Haliclona implexiformis and Lissodendoryx isodictyalis are near the top while Scopalina ruetzleri are near the lower end of the range. Temporary experimental desiccation resulted in 100% recovery of all three species after they had been exposed to either sun or shade for up to 2 h. Scopalina is the least resistant and lost over 90% tissue within 3 days after the 4-h and 6-h experiments; the remaining cell mass succumbed to infestation by microbes. Haliclona and Lissodendoryx recovered from as much as 6 h in full sun but lost 85% and 80% of the original tissue volume, respectively. In Lissodendoryx , clusters of larvae developed in the regenerating fragments. Water loss tolerated by the three species is estimated as 66% of wet weight in Haliclona , 54% in Lissodendoryx and 38% in Scopalina . Salinity of interstitial seawater (pore water) extracted from exposed sponges rose from ambient 3.5% to 4.348% after 1 h, to 5.1–5.9% after 6 h. Most endobionts died or left their host during this last phase. Natural vertical zonation in these sponges reflects their resistance to tidal exposure.     

Habitat Structure,Disturbance, and Equilibrium in Crustacean Communities*

Abstract. Using data from studies on alga-dwelling harpacticoid copepods from New Zealand and Britain and shallow water decapods from a variety of habitats in the Pacific and Caribbean, an analysis is made of the contribution of physical and biotic habitat structures to the generation and maintenance of crustacean species richness. The relation between the number of species and the complexity of the habitat is, in equilibrium communities, positive and essentially linear. Accordingly, Gray's (1979) and Stenseth's (1979) theoretical predictions are endorsed whereby species-abundance curves are, at equilibrium, expected to follow a log-normal distribution, whereas departures from the log-normal are anticipated in disturbed environments. Such departures reflect either increased dominance or inequalities in the species-abundance hierarchy. Because of their adaptable life-history traits, certain opportunist species are identified as those contributing most to departure points. The impact on community equilibrium of natural disturbance processes such as turbidity, exposure, and substratum transience is assessed.     

Effects of long-term sample preservation on flow cytometric analysis of natural populations of pico-and nanophytoplankton

The effects of long-term preservation on flow cytometric parameters of natural oceanic populations of pico-and nanophytoplankton have been examined. Populations collected at oligotrophic subtropical and subarctic locations in the North Pacific were fixed with glutaraldehyde and frozen in liquid nitrogen, according to Vaulot et al. (1989). During six months’ storage, chlorophyll red fluorescence declined in all the groups examined, while forward light scatter was enhanced in Synechococcus and Prochlorococcus, and weakened in nanoeucaryotes. Cell loss was not significant except for Synechococcus. Caution is required when analyzing flow cytometric data of samples stored for more than a month.     

Mussel Periostracum from Deep-Sea Redox Communities as a Microbial Habitat: The Scalloping Periostracum Borer

Abstract. A complex and highly unusual eukaryotic microorganism was discovered to be penetrating and removing the periostracum of deep-sea mussels from the Florida Escarpment brine seeps at a depth of 3266 m. These brine seeps support a chemolithoautotrophic redox community similar to those known from Pacific hydrotherma! vents. This microorganism of unknown taxonomic affinity is filamentous and coenocytic, with a simple plasma membrane and no cell wall. It forms prostrate, radiating systems of branched tunnels, 8–15 u.m in diameter. The surface of the tunnels is sculptured by helically organized, scale-like depressions, which are left as scars in the process of periostracum removal by the organism. Periostracum is removed in discrete pieces (scallops) at the ends of the tunnels. This organism has been found at three Atlantic deep-sea redox communities, but not in similar communities of the Pacific.     

Ecological characteristics of phytoplankton community from eutrophic waters in the Maluan Bay

I~IOWTheMaluanBayisashallowandmOStlyendedwatertheywhichisisolatedfromwesternXiamenhaforbyaseawall.Thebayhaslongbenboldingagreatdealofagriculturalandindustrialwaterandmunicipalsewage.Moreover,aquacultureindustryhasbeendeveloppedinal~aceinthebayinrecen...