In this study, we optimized procedures to enumerate viruses from marine sediments by epifluorescence microscopy using SYBR Green I as a stain. The highest virus yields from the bulk of the sediments were obtained by utilizing pyrophosphate and 3 min of sonication. The efficiency of extraction benthic viruses by pyrophosphate-ultrasound treatment was about 60% of the extractable virus particles. Samples treated with nucleases had increased virus counts, suggesting a masking effect of extracellular DNA. No significant differences were observed between virus counts obtained by epifluorescence microscopy and transmission electron microscopy. Both formaldehyde and glutaraldehyde gave significant reductions of virus counts after only 24 h of sediment storage, but no further loss occurred after 7 days.

Stable isotope ratios (typically of carbon and nitrogen) provide one representation of an organism's trophic niche and are widely used to examine aspects of food web structure. Yet stable isotopes have not been applied to quantitatively characterize community-wide aspects of trophic structure (i.e., at the level of an entire food web). We propose quantitative metrics that can be used to this end, drawing on similar approaches from ecomorphology research. For example, the convex hull area occupied by species in delta13C-delta15N niche space is a representation of the total extent of trophic diversity within a food web, whereas mean nearest neighbor distance among all species pairs is a measure of species packing within trophic niche space. To facilitate discussion of opportunities and limitations of the metrics, we provide empirical and conceptual examples drawn from Bahamian tidal creek food webs. These examples illustrate how this methodology can be used to quantify trophic diversity and trophic redundancy in food webs, as well as to link individual species to characteristics of the food web in which they are embedded. Building from extensive applications of stable isotope ratios by ecologists, the community-wide metrics may provide a new perspective on food web structure, function, and dynamics.

深海的海山生态系统支持着独特的生物群落,是海洋生态系统中物种扩散和进化的重要节点。由于研究的欠缺和认识的不足,国际间对于海山的区系和生物多样性认知存在较大分歧。存在海山特有种假说、物种源汇假说、孤岛假说、绿洲假说等各种假说,且均有争议。综述了海山生物区系和多样性研究的最新进展,指出了目前研究存在的缺陷和不足,并就我国未来有关海山生物区系和多样性研究提出了建议。

Seamounts support unique biological communities and might act as important nodes of species dispersal and evolution in deep ocean ecosystems. Seamounts have been one of the few characteristic ecosystems that remain underexplored in the abyssal world. However, our knowledge of seamount animals remains very limited due to the difficulty in access to technology, resulting in controversial explanation on their fauna, biodiversity, and biogeography. There have been several hypotheses on seamount biota, including the Endemicity Hypothesis, the SourceSink Hypothesis, the Insular Isolation Hypothesis, and the Oasis Hypothesis. We summarize the pros and cons of seamount fauna and biodiversity, and put forward proposals for future investigation on seamount ecosystem.

Suspended particulate matter (SPM) strongly alters the trophic environment of photosymbiotic aquatic organisms. At high particles loads, phototrophic energy gains can be diminished due to light absorption by suspended particles, and stress from particle abrasion or deposition on tissues. However, energy gains are enhanced if organisms are able to use SPM as a food source. For photosymbiotic benthic suspension feeders, increases in SPM concentrations may require both phototrophic and heterotrophic acclimation to sustain a positive energy balance. This study provides an experimental analysis of the effects of contrasting light and SPM regimes on the energy budget (scope for growth) of two zooxanthellate corals (Goniastrea retiformis and Porites cylindrica). Using a factorial design in a flow-through tank system, corals were exposed for 2 months to shaded and unshaded conditions (equivalent to 3-4 m depth at 4 and 16 mg dry weight SPM l(-1), respectively) and a range of controlled SPM loads with a natural organic content ( approximately 3% w/w). In G. retiformis, rates of particle ingestion were a linear function of SPM concentration within a broad range (1-30 mg dry weight l(-1)). After 2 months of shading, photosynthetic acclimation was significant in G. retiformis, but did not compensate for the reduced light level, as daily respiration exceeded daily photosynthesis. However, in response to the prolonged shading, G. retiformis more than doubled its rate of particle feeding. At high SPM treatments (16 mg dw l(-1)), sediment feeding by this species compensated fully for the 35-47% lower phototrophy in the shaded treatment. Due to both photo- and heterotrophic plasticity, G. retiformis gained tissue and skeletal mass at all experimental levels of light and SPM. In contrast, rates of particle intake by P. cylindrica contributed <10% to the energy budget in shaded and <3% in unshaded conditions. Feeding rates of P. cylindrica were half-saturated at approximately 3 mg dry weight l(-1), and four- to eight-fold lower than those of G. retiformis. Skeletal growth was sustained, but tissue mass and lipid contents declined in shaded and high-SPM treatments, and carbon loss due to shading by SPM was not compensated for by particle feeding. Thus, due to a lack of photo- and heterotrophic plasticity, periods of high turbidity resulted in energy deficiency in P. cylindrica, and high turbidity conditions appeared physiologically unsustainable for this species. This study is the first to show heterotrophic plasticity in a symbiotic coral, and to show that such plasticity can offset stress from high particle loads. It demonstrates that changes in the trophic mode of some coral species are a mechanism for sustaining a positive energy balance in turbid environments, thereby broadening their physiological niche.

Sponges link the microbial loop with benthic communities by feeding on bacteria. Glass sponge reefs on the continental shelf of western Canada have extremely high grazing rates, consuming seven times more particulate carbon than can be supplied by vertical flux alone. Unlike many sponges, the reef building species Aphrocallistes vastus has no microbial symbionts and removes little dissolved organic carbon. To determine how reef sponges therefore get enough food to sustain such substantial grazing we measured stable carbon and nitrogen isotope signatures of water, sediment and sponge tissues. To ensure samples were temporally associated, we also studied the duration particles were retained in tissues in controlled feeding studies using microscopic beads and C-13-labeled bacteria. Although fecal pellets were expelled from sponges within 24 hours of feeding, intact bacteria were still found in tissues and sponge tissues retained elevated C-13 levels for at least 14 days. These independent lines of evidence suggest that carbon in reef sponge tissues may reflect food consumed from days to weeks earlier. Stable isotope analysis suggests that heterotrophic bacteria ingested by the sponges comes from a confluence of trophic subsidies: from terrestrial and oceanic sources, and also potentially on sediment-borne bacteria resuspended by tidal currents.