Comparative jet wake structure and swimming performance of salps

Salps are barrel-shaped marine invertebrates that swim by jet propulsion. Morphological variations among species and life-cycle stages are accompanied by differences in swimming mode. The goal of this investigation was to compare propulsive jet wakes and swimming performance variables among morphologically distinct salp species (Pegea confoederata, Weelia (Salpa) cylindrica, Cyclosalpa sp.) and relate swimming patterns to ecological function. Using a combination of in situ dye visualization and particle image velocimetry (PIV) measurements, we describe properties of the jet wake and swimming performance variables including thrust, drag and propulsive efficiency. Locomotion by all species investigated was achieved via vortex ring propulsion. The slow-swimming P. confoederata produced the highest weight-specific thrust (T =53 N kg^(–1)) and swam with the highest wholecycle propulsive efficiency (η_wc= 55%). The fast-swimming W. cylindrica had the most streamlined body shape but produced an intermediate weight-specific thrust (T=30 N kg^(–1)) and swam with an intermediate whole-cycle propulsive efficiency (η_wc =52%). Weak swimming performance variables in the slow-swimming C. affinis, including the lowest weight-specific thrust (T=25 N kg^(–1)) and lowest whole-cycle propulsive efficiency (η_wc=47%), may be compensated by low energetic requirements. Swimming performance variables are considered in the context of ecological roles and evolutionary relationships

Distribution and taxonomy of zooplankton in the Alboran Sea and adjacent western Mediterranean : a literature survey and field guide

This a survey of literature records for occurrence and taxonomy of zooplankton in the Western Mediterranean, with particular emphasis on the Alboran Sea. It is intended to give a general background on the fauna, and facilitate identification of specimens collected or observed. A description of the hydrography of the Alboran Sea is followed by a general account of zooplankton biomass distribution, and more detailed lists of the occurrence of 361 species of medusae, siphonophores, ctenophores, worms, tunicates and crustaceans in 7 regions of the Western Mediterranean. Bioluminescent properties of the organisms are indicated where known. An illustrated taxonomic guide provides capsule descriptions and illustrations of 254 of the listed species.Funding was provided by Grant No. N00014-91-C6007 from the Naval Oceanographic and Atmospheric Research Laboratory to the Harbor Branch Oceanographic Institution

Diversity and Community Structure of Pelagic Fishes to 5000m Depth in the Sargasso Sea

The diversity, abundance and distribution of pelagic fishes from 0-5000 m in the Sargasso Sea, northwestern Atlantic Ocean, were investigated, with primary focus on fishes between 1000-5000 m. A large-volume, fine-mesh (335-μm), discrete-depth sampling system was used to sample the latter strata in 1000-m intervals. Species composition and total biomass of fishes collected in these strata were compared with samples taken 0-1000 m using a smaller midwater trawl. Samples were collected in association with the Census of Marine Zooplankton at-sea DNA-sequencing effort, allowing the determination of genetic barcodes of taxa for which species descriptions do not currently exist (e.g., many male ceratioid anglerfishes). A total of 3965 fish specimens were collected, representing minimally 127 species (84 genera), from 42 families. The bristlemouth, Cyclothone braueri, dominated the catches both above (47%) and below (41%) 1000 m. The Myctophidae and Stomiidae were the most species-rich taxa, while the deep-sea anglerfish suborder Ceratioidei was the most diverse bathypelagic taxon. Thirty species of fish were sequenced and data submitted to GenBank. New Ocean Biogeographic Information System location records for the Saragasso Sea were logged for 84 fish species. Hydrographic data revealed separation of the region into three physical regimes within the top 1000 m (northern, transition, and southern), while the sub-1000 m stratum was fairly homogeneous. Though species richness, abundance, and diversity were highest in the southern Sargasso, diversity indices of whole water column (0-5000 m) samples were not significantly different between regions. Below 1000 m, the 1000-2000 m stratum held the most diverse assemblage across the entire transect, but high diversity was exhibited below 3000 m at two of four stations. Ordination discriminated 13 pelagic fish assemblages, with these related to depth far more than region. Geometric abundance class analysis revealed profound differences in relative species abundances between the meso- and bathypelagic zones with the former demonstrating a much higher percentage of common species. This finding tracks the hydrographic patterns observed: increased stability in the bathypelagic zone favors increased numbers of rare species relative to the mesopelagic zone, where hydrographic complexity favors higher numbers of common species

Bathypelagic Fish Diversity in the Sargasso Sea, Northwestern Atlantic Ocean

Of the various marine habitats, one of the (if not the) most daunting to quantify is the under-sampled bathypelagic zone (\u3e 1000 m depth), which at 60% of the ocean’s volume is the largest habitat on Earth. One project addressing this challenge is the Census of Marine Zooplankton (CMarZ), whose goal is the assessment of biodiversity of animal plankton throughout the world’s oceans. The 2006 CMarZ cruise in the Western North Atlantic provided an unprecedented opportunity to sample bathypelagic micronekton using a large midwater trawl (10-m2 MOCNESS) outfitted with fine (0.335-mm) mesh netting. This netting allowed non-destructive sampling of the fragile fish fauna to 5000 m depth, thus facilitating accurate identification and at-sea DNA extraction and sequencing. A total of 3,965 fish specimens were collected from at least 127 species (84 genera, 42 families), many rarely caught, and four of which may be undescribed. Of note were male anglerfishes from five families, which are poorly known. Tissue was taken from all males to match with females, thus enabling the construction of a key for the most diverse bathypelagic fish group

Composition and degradation of salp fecal pellets: Implications for vertical flux in oceanic environments

Changes in the sinking rates, ash-free dry weights, particulate carbon and nitrogen content, and carbon:nitrogen ratios from the fecal pellets of several species of oceanic salps were examined in ten-day decomposition studies. Although bacteria and protozoa became abundant in the incubation vessels, most of the fecal pellets remained physically intact throughout the study. Bacterial activity in the pellets (measured by the rate of uptake of 3H-thymidine) increased, but microbial degradation had little effect on the sinking speeds of most of the fecal pellets. The average losses of ash-free dry weight and carbon and nitrogen content, along with changes in carbon:nitrogen ratio, were small compared to their initial values. We conclude that microbial degradation of large salp fecal pellets would not prevent the vertical flux to the deep ocean of a significant fraction of the particulate organic material contained in the pellets. The fecal pellets of oceanic salps provide a rapid, and potentially important, mechanism for the consolidation and vertical transport of organic and lithogenic material associated with minute particles in the open ocean

Enrichment of microbial populations in macroaggregates (marine snow) from surface waters of the North Atlantic

Marine snow particles (macroscopic detrital aggregates) were collected from surface waters throughout the western North Atlantic. Counts of phototrophic and heterotrophic picoplankton, phototrophic and heterotrophic nanoplankton, and phototrophic microplankton were made by epifluorescence microscopy. A Most Probable Number culture technique also was used to estimate the density of bacterivorous protozoa. All microbial populations enumerated were highly enriched on macroaggregates relative to their densities in the surrounding water. The degree of enrichment was greater in open ocean environments because microorganisms in the surrounding water were less abundant in the open ocean than in nearshore waters, and also because microbial density on marine snow was greater in the open ocean than in nearshore environments. Material released by ctenophores and appendicularia is a likely source of marine snow since it supported microbial populations of the same order of magnitude as were observed on SCUBA-collected particles. Heterotrophic nanoflagellates dominated the bacterivorous protozoa cultured from macroaggregates and the surrounding water, but dense populations of ciliates and amoebae also were present on particles. Protozoan populations on marine snow were so dense relative to the surrounding water as to suggest that detrital aggregates are responsible for the planktonic existence of some bacterivorous species

The remarkable squidworm is an example of discoveries that await in deep-pelagic habitats

Author Posting. © The Authors, 2010. This is the author's version of the work. It is posted here by permission of Royal Society for personal use, not for redistribution. The definitive version was published in Biology Letters 7 (2011): 449-453, doi:10.1098/rsbl.2010.0923.An intriguing new annelid, Teuthidodrilus samae (Annelida, Cirratuliformia) gen. and sp. nov., was observed and collected during deep water column exploration of the western Celebes Sea. The Celebes Sea is a deep pocket basin, effectively isolated from surrounding deep water, and is part of the Coral Triangle, a focal area for conservation because of its high diversity and unique geological history. Collected specimens reached 94 mm in length and possessed 10 anterior appendages that were as long or longer than the body. Two characters distinguish T. samae from other polychaetes: notochaetae forming broad, concavo-convex paddles, and six pairs of free-standing, oppositely branched nuchal organs. Phylogenetic analysis of five genes and a 29 character morphological matrix showed that T. samae is an acrocirrid (primarily benthic polychaetes) belonging to the morphologically diverse swimming clade. Pelagic animals within primarily benthic clades are of particular interest in evolutionary biology, because their adaptations to life in the water column inform us of the evolutionary possibilities and constraints within the clade and indirectly of the selective pressures at work in this unfamiliar habitat. This new genus illustrates how much we have to learn about even the large, abundant inhabitants of deep-pelagic communities.Funding was provided to LPM by grants from NOAA’s Office of Ocean Exploration and WHOI Ocean Life Institute, with additional support from the National Geographic Society. The University of California President’s Postdoctoral Fellowship provided funding to KJO

Effects of warm water intrusions on populations of macrozooplankton on Georges Bank, Northwest Atlantic

Author Posting. © The Authors, 2004. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Continental Shelf Research 25 (2005): 143-156, doi:10.1016/j.csr.2004.07.028.As part of the Georges Bank/North West Atlantic GLOBEC (Global Ocean Ecosystems Dynamics) Program, macrozooplankton and micronekton were collected on 30 Broad Scale Survey Cruises between January – June, 1995 –1999, using a 10 m2 MOCNESS (3mm mesh). The objective of this study is to examine the effects of warm water intrusions on populations of macrozooplankton, namely Salpa spp., Phronima spp., Neomysis americana, and Crangon septemspinosa, on Georges Bank. Salpa spp. and Phronima spp. showed a large degree of horizontal co-occurrence, being found predominantly in Upper Slope/Gulf Stream Water and Georges Bank/Gulf of Maine Water. Abundances of these taxa showed striking interannual variability, and were only abundant on the southern flank and in the Northeast Channel in late spring/early summer of 1995 and 1999, periods during which AVHRR imagery and hydrographic data showed the presence of warm water intrusions. These intrusions seemed to have little effect on the distribution of other macrozooplankton (e.g., Neomysis americana and Crangon septemspinosa). Warm water intrusions can directly affect Salpa spp. and Phronima spp. populations by advecting them onto Georges Bank, although other, more resident populations, especially those inside the 100m isobath, seem to be little affected by such intrusions.Additional thanks goes to Tom Niesen and Stan Williams for their advice on data analysis and interpretation. This work was supported by NSF award No. OCE96-17209 and NOAA award No. NA66GP0356 to S. M. Bollens provided from the US GLOBEC Northwest Atlantic/Georges Bank Program, a joint program of the National Science Foundation and the National Oceanic and Atmospheric Administration

Effects of turbulence on the feeding rate of a pelagic predator : the planktonic hydroid Clytia gracilis

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Experimental Marine Biology and Ecology 333 (2006): 159-165, doi:10.1016/j.jembe.2005.12.006.Relatively little is known about the role of turbulence in a predator - prey system where the predator is a passive, pelagic forager. The Campanulariid hydroid Clytia gracilis (Cnidaria, Hydrozoa) is unusual because it occurs as planktonic colonies and is reported to forage passively in the water column on Georges Bank, Massachusetts, USA. In this study we investigated the role of various turbulence conditions on the feeding rate of C. gracilis colonies in laboratory experiments. We found a positive relationship between turbulence velocities and feeding rates up to a turbulent energy dissipation rate of ca 1 cm2 s-3. Beyond this threshold feeding rate decreased slightly, indicating a dome-shaped relationship. Additionally, a negative relationship was found between feeding efficiency and hydroid colony size under lower turbulent velocities, but this trend was not significant under higher turbulence regimes.P. Adamík received support from the WHOI Academic Programs Office via the 2002 Summer Student Fellowship and while writing this paper from the Ministry of Education of the Czech Republic (MSM 6198959212 and MSM 153100012)

Voracious planktonic hydroids: unexpected predatory impact on a coastal marine ecosystem

Hydroids are typically attached, benthic cnidarians that feed on a variety of small prey. During sampling on Georges Bank in spring 1994, we found huge numbers of hydroids suspended in the plankton. They fed on young stages of copepods that are an important prey for fish, as well as on young fish themselves. Two independent methods were used to estimate feeding rates of the hydroids; both indicate that the hydroids are capable of consuming from 50% to over 100% of the daily production of young copepods. These results suggest that hydroids can have a profound effect on the population dynamics of zooplankton and young fish on Georges Bank