Physiologic and metagenomic attributes of the rhodoliths forming the largest CaCO3 bed in the South Atlantic Ocean

Rhodoliths are free-living coralline algae (Rhodophyta, Corallinales) that are ecologically important for the functioning of marine environments. They form extensive beds distributed worldwide, providing a habitat and nursery for benthic organisms and space for fisheries, and are an important source of calcium carbonate. The Abrolhos Bank, off eastern Brazil, harbors the world''s largest continuous rhodolith bed (of ∼21 000 km²) and has one of the largest marine CaCO₃ deposits (producing 25 megatons of CaCO₃ per year). Nevertheless, there is a lack of information about the microbial diversity, photosynthetic potential and ecological interactions within the rhodolith holobiont. Herein, we performed an ecophysiologic and metagenomic analysis of the Abrolhos rhodoliths to understand their microbial composition and functional components. Rhodoliths contained a specific microbiome that displayed a significant enrichment in aerobic ammonia-oxidizing betaproteobacteria and dissimilative sulfate-reducing deltaproteobacteria. We also observed a significant contribution of bacterial guilds (that is, photolithoautotrophs, anaerobic heterotrophs, sulfide oxidizers, anoxygenic phototrophs and methanogens) in the rhodolith metagenome, suggested to have important roles in biomineralization. The increased hits in aromatic compounds, fatty acid and secondary metabolism subsystems hint at an important chemically mediated interaction in which a functional job partition among eukaryal, archaeal and bacterial groups allows the rhodolith holobiont to thrive in the global ocean. High rates of photosynthesis were measured for Abrolhos rhodoliths (52.16 μmol carbon m⁻²s⁻¹), allowing the entire Abrolhos rhodolith bed to produce 5.65 × 10⁵ tons C per day. This estimate illustrates the great importance of the Abrolhos rhodolith beds for dissolved carbon production in the South Atlantic Ocean.     

莱州湾金城海域鱼礁投放后大型底栖动物群落变化

为研究莱州湾金城海域人工鱼礁对大型底栖动物的影响,2009-2012年对鱼礁区与对照区的大型底栖动物进行了9次调查,研究底栖动物种类组成、群落结构、种类相似性、生物量、丰度以及多样性的变化和群落稳定性.结果表明:人工鱼礁区与对照区共采集到大型底栖动物4门30科35种,其中鱼礁区30种,对照区27种.调查海域站点按照鱼礁投放与否可分为两个不同的群落,造成群落分组的首要贡献种为浮游生物食者.鱼礁区与对照区种类相似性由鱼礁投放后第一年的37.5％提高到第二年的58.6％.鱼礁区底栖动物生物量由第一年的1.00 g·m-2增加到第二年的1.55 g·m-2,差异显著;丰度由540 ind·m-2增至622ind·m-2.鱼礁区底栖动物的生物量和丰度均高于对照区.与对照区相比,鱼礁投放后鱼礁区Shannon指数、丰富度指数有所升高,均匀度指数有所降低.丰度/生物量比较(ABC)曲线表明,鱼礁投放后第二年底栖动物群落的扰动较第一年更为明显,说明人工鱼礁投放早期(1～2年)大型底栖动物群落还处于一个被扰动状态.莱州湾金城海域鱼礁投放后大型底栖动物群落变化主要受到物理、化学、生物以及人类活动的影响.     

The Humphead Wrasse,Cheilinus Undulatus: Synopsis of a Threatened and Poorly Known Giant Coral Reef Fish

The humphead wrasse, Cheilinus undulatus, is the largest living member of the family Labridae, with a maximum size exceeding 2 m and 190 kg. Its geographic range covers much of the Indo-Pacific. The species is not common, recorded maximum adult densities rarely exceeding 20 fish/10,000 m². Small individuals are typically associated with high coral cover; larger fish are found mainly on outer or deep reefs, steep slopes and passes, singly or in small groups and seagrasses. However, for reproduction the species forms small spawning aggregations of tens to more than one hundred fish. The diet of the humphead wrasse includes large invertebrates and small fishes. The species attains at least 30 years and reaches sexual maturation at about 35–50 cm total length and <5 years of age. Most small adults are female while mainly males exceed 1 m and there is evidence of female to male sex change. The humphead wrasse is of considerable cultural value in some Pacific countries and is among the most prized in the live reef food fish export trade, for which it is often taken in its juvenile size range, either directly for sale or, increasingly, for grow-out to market size. It is also marketed chilled. The species is particularly sensitive to fishing pressure. In most fished areas, density and body size have dropped substantially. It appears to be particularly heavily targeted and depleted in SE Asia and in some places faces extirpation. The humphead wrasse is often taken by night spearfishing and by cyanide, with protection typically weak or non-existent, despite regulations and by a vulnerable assessment on the 1996 IUCN Red List. The humphead wrasse has not been reared successfully in hatcheries. Other giant reef fish share many similar problems and detailed study of the humphead wrasse contributes to a better understanding and conservation of all such species. This review examines and evaluates published and gray literature, original unpublished research and correspondence with almost 50 knowledgeable workers. It examines the value of such sources for quickly, but adequately, assessing the conservation and management status and key data gaps in species that are little known, vulnerable, difficult and expensive to study and may require urgent management or conservation action.