Symbiotic microbes play a variety of fundamental roles in the health and habitat ranges of their hosts. While prokaryotes in marine sponges have been broadly characterized, the diversity of sponge-inhabiting fungi has barely been explored using molecular approaches. Fungi are an important component of many marine and terrestrial ecosystems, and they may be an ecologically significant group in sponge-microbe interactions. This study tested the feasibility of using existing fungal primers for molecular analysis of sponge-associated fungal communities. None of the eight selected primer pairs yielded satisfactory results in fungal rRNA gene or internal transcribed spacer (ITS) clone library constructions. However, 3 of 10 denaturing gradient gel electrophoresis (DGGE) primer sets, which were designed to preferentially amplify fungal rRNA gene or ITS regions from terrestrial environmental samples, were successfully amplified from fungal targets in marine sponges. DGGE analysis indicated that fungal communities differ among different sponge species (Suberites zeteki and Mycale armata) and also vary between sponges and seawater. Sequence analysis of DGGE bands identified 23 and 21 fungal species from each of the two sponge species S. zeteki and M. armata, respectively. These species were representatives of 11 taxonomic orders and belonged to the phyla of Ascomycota (seven orders) and Basidiomycota (four orders). Five of these taxonomic orders (Malasseziales, Corticiales, Polyporales, Agaricales, and Dothideomycetes et Chaetothyriomcetes incertae sedis) have now been identified for the first time in marine sponges. Seven and six fungal species from S. zeteki and M. armata, respectively, are potentially new species because of their low sequence identity (<98%) with their references in GenBank. Phylogenetic analysis indicated sponge-derived sequences were clustered into "marine fungus clades" with those from other marine habitats. This is the first report of molecular analysis of fungal communities in marine sponges, adding depth and dimension to our understanding of sponge-associated microbial communities.

[1] In the North Pacific Subtropical Gyre (NPSG), the regular occurrence of summer phytoplankton blooms contributes to marine ecosystem productivity and the annual carbon export. The mechanisms underlying the formation, maintenance, and decay of these blooms remain largely unknown; nitrogen fixation, episodic vertical mixing of nutrients, and meso-(<100 km) and submesoscale (<10 km) physical processes are all hypothesized to contribute to bloom dynamics. In addition, zones of convergence in the ocean's surface layers are known to generate downwelling and/or converging currents that affect plankton distributions. It has been difficult to quantify the importance of these convergence zones in the export flux of particulate organic carbon (POC) in the open ocean. Here we use two high-resolution ocean transects across a pair of mesoscale eddies in the vicinity of Station ALOHA (22 45′N, 158 00′W) to show that horizontal turbulent stirring may have been a dominant control on the spatial distribution of the nitrogen fixing cyanobacterium Trichodesmium spp. Fast repetition rate fluorometry measurements suggested that this distribution stimulated new primary production; this conclusion was not confirmed by 14 C-based measurements, possibly because of different sampling scales for the two methods. Our observations of particle size distributions along the two transects showed that stretching by the mesoscale eddy field produced submesoscale features that mediated POC export via frontogenetically generated downwelling currents. This study highlights the need to combine high-resolution biogeochemical and physical data sets to understand the links between Trichodesmium spp. surface distribution and POC export in the NPSG at the submesoscale level.

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Photosynthesis-irradiance (P-E) relationships and in situ measurements of primary production for 2 phytoplankton size fractions (> 2 µm and 0.2 to 2 µm) were used to evaluate variability in photophysiology over a 5 yr period (2004 to 2009) in the North Pacific Subtropical Gyre (NPSG). Picophytoplankton (0.2 to 2 µm) were dominant contributors to euphotic zone chlorophyll a (chl a) concentrations (averaging 91 ± 2% [mean ± SD] of the 0 to 125 m depth-integrated inventories) and accounted for a major fraction (averaging 74 ± 7%) of the in situ, depth-integrated, 14 Cbased primary production. Short-term in vitro P-E experiments were conducted to examine the photophysiology of both phytoplankton size classes. Results from these experiments demonstrated that in the well-lit ocean (0 to 45 m) chl a normalized maximum rates of photosynthesis, P chl max , were significantly greater among the larger phytoplankton size class than in the smaller size fraction (1-way ANOVA, p < 0.01), while in the dimly lit region (125 m) there were no significant sizedependent differences in P chl max (1-way ANOVA, p > 0.05). Neither the initial slope of the P-E relationships, α, nor the light intensities required to saturate photosynthesis, E k , varied significantly between the 2 size fractions. Although larger phytoplankton appear to constitute a relatively small fraction of phytoplankton biomass and production in this ecosystem, the photophysiological responses of plankton in this size class demonstrated considerable variability, suggesting these larger size phytoplankton experience time-variable changes in growth despite persistently oligotrophic habitat conditions. KEY WORDS: Photosynthesis · Photophysiology · Phytoplankton · Primary production· North Pacific · Oligotrophic Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 440: 27-40, 2011 28 Photosynthesis-irradiance (P-E) relationships demonstrate several well-defined characteristics, which are typically described by using hyperbolic or negative exponential models (Jassby & Platt 1976. Various photophysiological parameters can be derived from such relationships, including the maximum rate of carbon fixation (termed P max ), the initial slope (termed α) of the P-E response, which provides a measure of light harvesting efficiency by photosynthesis, the susceptibility of photosynthesis to inhibition at elevated light flux (termed β) and the irradiance required to saturate photosynthesis (termed E k ). When used in P-E relationships, rates of photosynthesis are frequently normalized to concentrations of chlorophyll a (chl a), where the resulting normalized maximum photosynthetic rate is termed P chl max . When combined with information on temperaturedependent phytoplankton growth (Eppley 1972), P-E derived parameters can be incorporated into biooptical models and used to estimate areal rates of primary production from remotely sensed determinations of phytoplankton pigments, temperature and light (Bidigare et al. 1992, Pla...

SrHA grown on GO nanosheet-reinforced chitosan scaffolds promoted the bone regeneration as SrHA and GO had good osteoconductivity and high ALP activity while the chitosan matrix played a role in antibacteria.

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