In situ grazing on plankton \u3c10 mu m by the boreal sponge Mycale lingua

Ultraplankton, heterotrophic and autotrophic plankton \u3c 5 mu m, are the most abundant food source in the world\u27s oceans, yet their role as a food source for macroinvertebrates is largely unexamined. We quantified in situ feeding on heterotrophic and autotrophic plankton \u3c 10 mu m by the boreal sponge Mycale lingua using measurements that quantified sponge feeding efficiencies, pumping rates, and abundance to determine the contribution of plankton \u3c 10 mu m to sponge carbon intake. Using dual-beam now cytometry we identified 5 populations of plankton \u3c 10 mu m: heterotrophic bacteria, Prochlorococcus, Synechococcus-type cyanobacteria, autotrophic eucaryotes \u3c 3 mu m, and autotrophic eucaryotes 3 to 10 mu m Mycale lingua nonselectively grazed on all types of plankton \u3c 10 mu m. Prochlorococcus was filtered with the highest efficiency (93%), followed by Synechococcus-type cyanobacteria (89%), autotrophic eucaryotes 3 to 10 mu m (86%), heterotrophic bacteria (74%), and autotrophic eucaryotes \u3c 3 mu m (72%). We conservatively estimate that M. lingua al naturally occurring densities can obtain 29 mg C d(-1) m(-2) feeding on plankton \u3c 10 mu m, with 74% resulting from ultraplankton, suggesting that ultraplankton are an important overlooked component of benthic-pelagic coupling

Density-dependent settler-recruit-juvenile relationships in blue crabs

Current theory on the population dynamics of marine species with complex life history patterns posits that a suite of physical and biotic forces (e.g., habitat structure and density-dependent predation or emigration) control survival and abundance in early life history, particularly after settlement. We have conducted a long-term sampling effort accompanied by a series of field and laboratory experiments examining the joint effects of habitat type, body size, and population density upon abundance and survival of early juveniles of the blue crab, Callinectes sapidus. In addition, the chance occurrence of a tropical storm during one set of experiments provided an opportunity to assess the impact of a physical disturbance upon newly settled blue crab survival and abundance. In the 10-yr sampling effort, we quantified relationships between sequential life history stages (juvenile crab instars) in seagrass beds, the initial nursery habitat for blue crabs in the lower Chesapeake Bay. Inter-instar relationships were defined as the densities of larger instars as dependent on the densities of smaller instars. Inter-instar relationships for the youngest instars are described by hyperbolic functions until crabs begin to emigrate to unvegetated habitats at approximately the fifth instar. Inter-instar relationships between crabs larger than the fifth instar and smaller crabs become either parabolic or linear functions and decay as the number of instars between sequential life history stages increases. While both the hyperbolic and parabolic functions are indicative of populations regulated by density-dependent processes, either predation or emigration, the decay in the functions describing the inter-instar relationships for crabs larger than the fifth instar indicates that the suite of processes regulating this segment of the population changes qualitatively. In laboratory and field experiments, the effects of vegetated and unvegetated habitats and size-specific predation on newly settled juveniles were tested. Tethering was used to quantify relative rates of predation, and a laboratory study was conducted to determine if tethering induced treatment-specific bias. We found no statistically significant interactions between the tethering treatment and the factor treatments of crab size and habitat during the laboratory study, indicating that tethering did not produce treatment-specific bias. Thus, tethering provided a relative measure of predation that allowed comparisons between treatments of habitat and crab size on crab survival. In both laboratory and field experiments, survival was significantly higher in vegetated habitats and with increasing size until the ninth instar, when survival did not differ by habitat. This difference explains the dispersal from vegetated to unvegetated habitats that occurred between the fifth and seventh instars. In addition, survival of all crabs was significantly increased both during and after Tropical Storm Danielle compared to pre-storm conditions. A model is developed that describes juvenile survival as a function of crab size and habitat type. Survival curves in both habitats are represented by similar sigmoid functions with survival higher in vegetated habitats. Subsequently, the survival of newly settled blue crabs is likely dependent on the availability of complex habitat. Thus, a suite of biotic and physical processes, both density-dependent and density-independent, control the early life history after settlement for the blue crab

Trophic effects of sponge feeding within Lake Baikal\u27s littoral zone .2. Sponge abundance, diet, feeding efficiency, and carbon flux

Endemic freshwater demosponges in the littoral zone of Lake Baikal, Russia, dominate the benthic biomass, covering 44% of the benthos. We measured in situ sponge abundance and,orating and calculated sponge-mediated Fluxes of picoplankton (plankton \u3c2 mu m) for two common species, Baikalospongia intermedia and Baikalospongia bacillifera. By means of dual-beam how cytometry, we found retention efficiencies ranging from 58 to 99% for four types of picoplankton: heterotrophic bacteria, Synechococcus-type cyanobacteria, autotrophic picoplankton with one chloroplast, and autotrophic picoplankton with two chloroplasts. By using a general model for organism-mediated fluxes, we conservatively estimate that through active suspension feeding, sponges are a sink for 1.97 g C d(-1) m(-1), mostly from procaryotic cell types. Furthermore, grazing by these extensive sponge communities can create a layer of picoplankton-depleted water overlying the benthic community in this unique lake

Estimates of Particulate Organic Carbon Flowing from the Pelagic Environment to the Benthos through Sponge Assemblages

Despite the importance of trophic interactions between organisms, and the relationship between primary production and benthic diversity, there have been few studies that have quantified the carbon flow from pelagic to benthic environments as a result of the assemblage level activity of suspension-feeding organisms. In this study, we examine the feeding activity of seven common sponge species from the Taputeranga marine reserve on the south coast of Wellington in New Zealand. We analysed the diet composition, feeding efficiency, pumping rates, and the number of food particles (specifically picoplanktonic prokaryotic cells) retained by sponges. We used this information, combined with abundance estimates of the sponges and estimations of the total amount of food available to sponges in a known volume of water (89,821 m3), to estimate: (1) particulate organic carbon (POC) fluxes through sponges as a result of their suspension-feeding activities on picoplankton; and (2) the proportion of the available POC from picoplankton that sponges consume. The most POC acquired by the sponges was from non-photosynthetic bacterial cells (ranging from 0.09 to 4.69 g C d−1 with varying sponge percentage cover from 0.5 to 5%), followed by Prochlorococcus (0.07 to 3.47 g C d−1) and then Synechococcus (0.05 to 2.34 g C d−1) cells. Depending on sponge abundance, the amount of POC that sponges consumed as a proportion of the total POC available was 0.2–12.1% for Bac, 0.4–21.3% for Prochlo, and 0.3–15.8% for Synecho. The flux of POC for the whole sponge assemblage, based on the consumption of prokaryotic picoplankton, ranged from 0.07–3.50 g C m2 d−1. This study is the first to estimate the contribution of a sponge assemblage (rather than focusing on individual sponge species) to POC flow from three groups of picoplankton in a temperate rocky reef through the feeding activity of sponges and demonstrates the importance of sponges to energy flow in rocky reef environments

Tolerance of sponge assemblages to temperature anomalies: resilience and proliferation of sponges following the 1997-8 El-Niño southern oscillation.

Coral reefs across the world are under threat from a range of stressors, and while there has been considerable focus on the impacts of these stressors on corals, far less is known about their effect on other reef organisms. The 1997-8 El-Niño Southern Oscillation (ENSO) had notable and severe impacts on coral reefs worldwide, but not all reef organisms were negatively impacted by this large-scale event. Here we describe how the sponge fauna at Bahia, Brazil was influenced by the 1997-8 ENSO event. Sponge assemblages from three contrasting reef habitats (reef tops, walls and shallow banks) at four sites were assessed annually from 1995 to 2011. The within-habitat sponge diversity did not vary significantly across the study period; however, there was a significant increase in density in all habitats. Multivariate analyses revealed no significant difference in sponge assemblage composition (ANOSIM) between pre- and post-ENSO years for any of the habitats, suggesting that neither the 1997-8 nor any subsequent smaller ENSO events have had any measurable impact on the reef sponge assemblage. Importantly, this is in marked contrast to the results previously reported for a suite of other taxa (including corals, echinoderms, bryozoans, and ascidians), which all suffered mass mortalities as a result of the ENSO event. Our results suggest that of all reef taxa, sponges have the potential to be resilient to large-scale thermal stress events and we hypothesize that sponges might be less affected by projected increases in sea surface temperature compared to other major groups of reef organisms

Ontogenetic diet shifts in the reef fish Pseudanthias rubrizonatus from isolated populations on the North-West Shelf of Australia

The red-barred anthias Pseudanthias rubrizonatus is a common tropical deep reef fish species found in Australia, but little is known about its dietary preferences and trophic interactions. We examined the gut contents and stable isotope signatures (δ13C and δ15N) of P. rubrizonatus from populations on the North-West Shelf of Australia to determine differences in diet relative to site, depth and fish size. We sampled 5 fish populations from a series of sub-sea structures, from 82 to 152 m depth, which had been submerged for up to 15 yr. Gut content analysis suggested that P. rubrizonatus displays an opportunistic feeding strategy and utilises both pelagic and benthic resources, including larval fishes, heteropods, isopods and mysids. Stable isotope analyses revealed that at all depths P. rubrizonatus underwent an ontogenetic diet shift. Values for δ13C in muscle ranged from -19.7% for small fish to -16.2% for larger individuals, and δ15N ranged from 8.2% for smaller fish to 13.2% for larger fish, indicating that a diet shift occurs at the end of juvenile development between 30 and 50 mm standard length. By simultaneously analysing gut contents and stable isotope signatures of the collected specimens, we have documented opportunistic dietary strategies that may assist P. rubrizonatus to colonise isolated structures. © Inter-Research 2010

Synovectomy of the elbow and radial head excision in rheumatoid arthritis. Predictive factors and long-term outcome.

We carried out a survival analysis of elbow synovectomy (ES) and excision of the radial head (RHE) performed on 171 rheumatoid elbows. The failure criteria were revision surgery (performed or desired) and/or the presence of significant or severe pain. The cumulative survival was 81% at one year which thereafter decreased by an average of 2.6% per year. The strongest predictor for success was a low preoperative range of supination-pronation when corresponding survival curves were compared. A low range of flexion-extension also predicted failure. Combining both factors gave better prediction (failure: 6.3% v 67%), but a long duration of elbow symptoms before surgery predicted failure (72%, p = 0.04). At review, there was a mean gain of 50 degrees in supination-pronation and 11 degrees in flexion-extension; both correlated with success. Failure correlated with recurrence of synovitis, elbow instability, ulnar neuropathy, poor general mobility and poor upper-limb function. The last was independently affected by the severity of RA in the ipsilateral shoulder. Our findings show that although the short-term result of ES and RHE in rheumatoid arthritis is good, the long-term outcome is poor except in a subgroup with more than 50% limitation of forearm rotation