Heterotrophic bacteria in Long Island Sound

Correlated with a study of heterotrophic bacteria from cultures of larval bivalve molluses, bacteria were studied from the water column over an oyster bed in Lont Island Sound, USA. Samples taken biweekly for 1 year showed bacterial densities ranging from 1.2x10³/ml in summer to 3.8x10⁴/ml in winter. Variation in seasonal density mirrored that of phytoplankton. Gram-negativ rods constituted 99% of the isolate. Eight genera were identified, but 92.3% of these were Achromobacter, Flavobacterium, and Pseudomonas. Pseudomonads dominated the summer flora, whereas flavobacteria were most abundant in spring. Types varied seasonally, but proteolytic, lipolytic, and amylolytic activity appeared independent of season.     

Studies on the sublittoral free-living nematodes of Liverpool Bay. I. The structure and distribution of the nematode populations

Data collected from a survey of the benthic fauna of Liverpool Bay (UK) have been used to study the distribution and structure, in terms of percent age dominance and percent age frequency, of the nematode populations. Cluster analysis of the faunistic data from individual stations has shown that the populations are not sharply delimited. The relative proportions of their characteristic genera are extremely variable, and apparently influenced by small differences in sediment composition. It is, thus, considered more logical to think in terms of a number of different habitats, each with certain characteristic genera, rather than in terms of a series of discrete associations. Six types of habitat are distinguished on the basis of sediment granulometry: (1) mud and sandy mud; (2) very muddy sand; (3) muddy sand; (4) muddy sand-gravel mixtures; (5) clean sand-gravel mixtures; (6) clean sand. Habitats 1, 2 and 3 were dominated by Sabatieria spp., the degree of dominance apparently being related to the percentage of silt-clay. Habitat 4 was dominated by Neochromadora sp. and Sabatieria spp. and Habitats 5 and 6 by Desmodora sp. Both generic and dominance diversity were very much lower for Habitats 1 and 2 than elsewhere.     

Genetic structure of asexually reproducing Enteromorpha linza (Ulvales: Chlorophyta) in Long Island Sound

Heterotrophic bacterial uptake and turnover of glycolate were measured in the water column of the New York Bight apex during four seasonal cruises over almost a one-year period between May 1977 and March 1978. Glycolate turnover was most rapid in May and July, when primary productivity and estuarine runoff were high. Extremely rapid glycolate turnover times (<1 h) were detected at some stations during these months. Increased bacterial glycolate tunover did not accompany increased primary productivity in March, when water temperatures were lowest. Glycolate flux calculations indicate that the measured rates of glycolate consumption by bacteria always exceeded estimated glycolate production by phytoplankton, except in March. This excess may reflect an underestimation of phytoplankton production or the input of glycolate from other sources, such as estuarine runoff. Glycolate utilization appears to be seasonally important to bacteria in the New York Bight apex, coinciding with fluctuations in phytoplankton primary productivity.     

Studies on the sublittoral free-living nematodes of Liverpool Bay. II. Influence of sediment composition on the distribution of marine nematodes

Previous work has shown that the composition and diversity of nematode populations in Liverpool Bay (UK) are correlated with sediment granulometry, and possible reasons for this relationship are now discussed. Sediment granulometry and nematode size appear not to be directly related, but the range of nematode lengths is greater in the more heterogeneous sediments. Median particle diameter, sorting efficiency and silt/clay content are all considered to affect sediment uniformity, and an index including all three factors correlated significantly with both size diversity and species diversity. Study of the distribution of the various feeding types revealed that the relative and absolute abundances of epistratum feeders and non-selective deposit feeders correlated significantly with the sediment silt/clay content. It is concluded that sediment granulometry influences nematode distribution both directly in determining the size range of the populations (and hence, to some extent, the species diversity) and indirectly in determining, to a great extent, the type of food available. In addition, it was noted that nematodes with very ornate cuticular ornamentation tended to be associated with coarser, silt-free sediments, and it is suggested that this may be correlated both with their mode of locomotion and with the need for mechanical protection in unstable substrata.     

Grazing by 35 to 202 μm micro-zooplankton in Long Island Sound

Micro-zooplankton abundance in Long Island Sound varied from 10³ to 10⁴ animals l^-1 at the station studied and consisted almost entirely of tintinnids. The micro-zooplankton were found to sometimes remove a significant portion of the chlorophyll a standing stock, with an upper limit of 41% of the standing stock being ingested per day. Observed ingestion rates ranged from 0.001 to 0.17 ng chlorophyll a removed animal^-1 h^-1 and from 0.06 to 87 cells removed animal^-1 h^-1, depending on season and type of cell being ingested. Filtering rates varied from 1.03 to 84.7 l animal^-1 h^-1. As a community, the micro-zooplankton exhibited the same order of magnitude ingestion and filtering rates as those noted for copepods.Contribution No. 259 of the Marine Sciences Center     

Metabolic studies on thiobiotic free-living nematodes and their symbiotic microorganisms

The marine, free-living Stilbonematinae (Nematoda: Desmodoridae) are remarkable for the ectosymbiotic, prokaryotic microorganisms that populate their entire body surface. These nematodes occur in sulfidic sediments in the microoxic zone just above the sulfide maximum. Several facts point to a chemolithotrophic, sulfide oxidizing nature of the microorganisms. The oxygen uptake of three species was measured with and without their microbial coat using Cartesian and Gradient Diver microrespirometry in February 1989 at Carrie Bow Cay (Belize Barrier Reef). Symbiont-free stilbonematids exhibited constant and uniform oxygen uptake rates over several hours; rates which are significantly lower than those of oxyphilic nematodes. Freshly extracted stilbonematids, with intact bacterial coats, consumed significantly more oxygen than symbiont-free worms in the first 3 h of measurement. While the rates of aposymbiotic worms were more or less constant over time, the rates of symbiont-carrying worms exhibited a conspicuous drop during prolonged respiration. InStilbonema sp., symbiont carrying individuals kept under oxygenated conditions for more than 12 h had a respiration rate similar to those of aposymbiotic specimens. When such worms were re-incubated in sulfide-enriched seawater the respiration rate was significantly elevated. The possibility of recharging the oxygenated symbiosis system via sulfide-uptake is seen as an indication that storage of reduced sulfur compounds, or reserve substances synthetized in the presence of sulfide, play a decisive role in the metabolisms of the symbiotic bacteria. Migration of nematodes between sulfidic and oxidized sediment-layers are, most likely, the key to understanding the success of this nematode-bacteria symbiosis.Please address all correspondence and requests for reprints to Professor J. Ott     

Chemical Stability of Capped Dredged Material Disposal Mounds in Long Island Sound, Usa

Geochemical analysis and visual inspection of cores collected from capped dredged material mounds revealed that in many cores, cap material was clearly distinguishable, both visually and chemically, from mound material. Contaminated dredged sediments were disposed in Long Island Sound eleven and seven years prior to sampling, and capped with uncontaminated dredged sediments. Core data provided no conclusive evidence of physical disturbance of, or chemical migration from, the contaminated mound sediments. Obvious chemical gradients of contaminant concentrations, which we propose are indicators of chemical migration, were not detected in the cores. Heterogeneity of the cap and mound sediments in some cores made the interface less distinct. We postulate that the preservation of spatial variability of sediment texture and associated contaminants observed within dredged material mounds is a result of the dredging process. Preservation of the textural and contaminant history of dredged sediments within finegrained cohesive cap materials provides evidence of the absence of physical or chemical disturbance.     

Chemical Stability of Capped Dredged Material Disposal Mounds in Long Island Sound,Usa

Geochemical analysis and visual inspection of cores collected from capped dredged material mounds revealed that in many cores, cap material was clearly distinguishable, both visually and chemically, from mound material. Contaminated dredged sediments were disposed in Long Island Sound eleven and seven years prior to sampling, and capped with uncontaminated dredged sediments. Core data provided no conclusive evidence of physical disturbance of, or chemical migration from, the contaminated mound sediments. Obvious chemical gradients of contaminant concentrations, which we propose are indicators of chemical migration, were not detected in the cores. Heterogeneity of the cap and mound sediments in some cores made the interface less distinct. We postulate that the preservation of spatial variability of sediment texture and associated contaminants observed within dredged material mounds is a result of the dredging process. Preservation of the textural and contaminant history of dredged sediments within finegrained cohesive cap materials provides evidence of the absence of physical or chemical disturbance.     

Survival of copepods passing through a nuclear power station on northeastern Long Island Sound,USA

About 70% of the copepods entering the cooling water system of a nuclear power plant on northeastern Long Island Sound (USA) are not returned to the Sound in the effluent. Copepod mortalities are caused by the mechanical or hydraulic stresses of passage, although our experimental design could not determine whether heat or chlorination could cause mortality in the absence of mortality induced by hydraulic stress. After passing through the power plant, copepods sink rapidly (ca. 2.5 times faster than controls). This leads to an increase in concentrations of copepods suspended in the deep water (25 to 30 m) of the effluent pond. About half of the live copepods collected at the discharge and held in situ died within 3.5 days, and 70% died within 5 days, whereas only 10% of those from the intake died in 5 days. About 60% of the copepods observed suspended in deep water in the pond were dead. The copepod mortality caused by the power plant reflects the loss in secondary production occurring below about 270×10³ m² of sea surface in Long Island Sound annually. This loss represents a reduction of about 0.1% in the annual secondary production over a 333 km² area of Long Island Sound adjacent to the power plant. Highest losses occurred during the spring (April, 1.4×10⁶ g dry weight), the lowest in autumn (November, 45.8×10³ g). If the same copepod loss rate exists for all power plants in Long Island Sound, then secondary production in 1.69×10⁶ m², or 0.05% of the total copepod production may be lost annually. A comparison of the surface outflow from Long Island to Block Island Sound with the water entrained through Millstone Unit One, and the 70% copepod loss rate in the latter area, indicates that Unit One eliminates about 0.1 to 0.3% of the copepod production in eastern Long Island Sound. This calculation compares favorably with losses computed from production data.     

Flax Pond ecosystem study: Exchanges of phosphorus between a salt marsh and the coastal waters of Long Island Sound

The exchanges of phosphorus between the Flax Pond, a tidal Spartina alterniflora marsh on the north shore of Long Island (USA) and Long Island Sound were measured over 18 months. Phosphate was exported from the marsh from May through December and imported during the remainder of the year. Organic phosphorus appears to be accumulated in all seasons, but the yearly phosphorus budget of the marsh is approximately balanced despite the accumulation of about 6 mm of sediment annually.     

The role of habitat heterogeneity in structuring the community of intertidal free-living marine nematodes

The role of habitat complexity has been widely neglected in the study of meiofaunal community patterns. We studied the intertidal nematode community of a structurally complex macrotidal beach exhibiting contrasting microhabitats (sandbars and runnels) to understand the influence of environmental gradients and habitat heterogeneity in the community structure. We tested whether topographical complexity affected (1) the zonation pattern in terms of abundance and diversity, and (2) local diversity by promoting compartmentalization into distinct faunal groups. Our analyses revealed three major faunal assemblages along the exposure gradient associated to differences in mean grain size and chlorophyll a. Diversity patterns involved a mid-intertidal peak, consistent with the intermediate disturbance hypothesis, and another peak at the limit with the subtidal region, consistent with the transition zone. These results highlight the predominance of environmental gradients in establishing intertidal zonation. However, microhabitats differed in environmental conditions and possessed significantly distinct nematofaunal communities. Runnels featured higher levels of taxonomic and functional diversity, many unique genera, and the community differed from the assemblage at the limit to the subtidal, stressing their role as distinct microhabitats. The nematofauna of the structurally complex beach was more diverse than the one from a homogeneous beach nearby, supporting the hypothesis that structural heterogeneity promotes diversity by compartmentalization and highlighting the importance of microhabitats in the assessment of biodiversity. Contrary to previous predictions, our results indicate potentially high regional marine nematode diversity in the Upper Gulf of California.     

Three new species of free-living marine nematodes from sublittoral sediments in Liverpool Bay

Three new species of free-living marine nematodes are described from sublittoral sediments in Liverpool Bay, UK. Pselionema longiseta n.sp. (Ceramonematoidea) is closest to P. longissimum Gerlach, 1952, from which it is distinguished by the longer cephalic setae and the larger amphids; Laimella filicaudata n.sp. (Chromadoroidea) is closest to L. longicauda Cobb, 1920, from which it is mainly distinguished by the much greater curvature of the spicules and the longer caudal apophyses of the gubernaculum; Pseudonchus decempapillatus n.sp. (Choanolaimoidea) is closest to P. deconincki Warwick, 1969 and is distinguished by the presence of 10, rather than 13, pre-anal supplements in the male, by the longer cephalic setae, and by the presence of numerous caudal setae.     

Diversity of free-living marine nematodes (Enoplida) from Baja California assessed by integrative taxonomy

We used morphological and molecular approaches to evaluate the diversity of free-living marine nematodes (order Enoplida) at four coastal sites in the Gulf of California and three on the Pacific coast of Baja California, Mexico. We identified 22 morphological species belonging to six families, of which Thoracostomopsidae and Oncholaimidae were the most diverse. The genus Mesacanthion (Thoracostomopsidae) was the most widespread and diverse. Five allopatric species, genetically and morphologically differentiated, were found in two localities in the Gulf of California (M. sp1 and M. sp2) and three in the Pacific coast (M. sp3, M. sp4 and M. sp5). Overall, we produced 19 and 20 sequences for the 18S and 28S genes, respectively. Neither gene displayed intraspecific polymorphisms, which allowed us to establish that some morphological variation was likely either ontogenetic or due to phenotypic plasticity. Although 18S and 28S phylogenies were topologically congruent (incongruence length difference test, P > 0.05), divergences between species were much higher in the 28S gene. Moreover, this gene possessed a stronger phylogenetic signal to resolve relationships involving Rhabdodemania and Bathylaimus. On the other hand, the close relationship of Pareurystomina (Enchilidiidae) with oncholaimids warrants further study. The 28S sequences (D2D3 domain) may be better suited for DNA barcoding of marine nematodes than those from the 18S rDNA, particularly for differentiating closely related or cryptic species. Finally, our results underline the relevance of adopting an integrative approach encompassing morphological and molecular analyses to improve the assessment of marine nematode diversity and advance their taxonomy.     

Analysis of the small-scale spatial patterns of free-living marine nematodes from tidal flats in the East Frisian Wadden Sea

Serial samples with a multiple corer were taken in order to understand the small-scale aggregation patterns in the nematode community. A total of 77 species was found in the sample. Fifteen dominant nematode species were examined by means of a dispersion analysis. Only one species (Metachromadora scotlandica) may be considered randomly distributed. A variogram analysis gave no proof of aggregation in that species, but all the other (aggregated) species displayed different spatial patterns: (1) a maximum/aggregation at the sample's margin, (2) two maxima/aggregations in the centre of the sample, (3) aggregation of individuals distributed at random over the entire sample (Metalinhomoeus typicus) and (4) aggregation of individuals distributed at random only in the centre of the sample (Paralinhomoeus ilenensis). These results allow the prognosis that distribution patterns are repetitive in five species (Microlaimus conothelis, M. marinus, Odontophora rectangula, Oncholaimellus calvadosicus, Viscosia rustica). Finally, by means of MDS-ordination (based on cosine similarity) two nematode associations were distinguished: one group represented by diatom-feeders (sensu lato), the other one comprised of DOM-users (sensu lato). Received: 13 May 1998 / Accepted: 15 January 1999     

Inducible defenses in the eastern oyster Crassostrea virginica Gmelin in response to the presence of the predatory oyster drill Urosalpinx cinerea Say in Long Island Sound

The response of the eastern oyster C. virginica to the presence of the oyster drill Urosalpinx cinerea was examined from July to September 2011. Several aspects of oyster growth were measured, including wet weight, shell weight, and dorsal shell area for oysters collected near Groton, Connecticut (41.32036 N, −72.06330 W). Wet weight and shell weight growth were significantly higher in the presence of the predator U. cinerea, while tissue weight showed no difference from the control. The control group showed more shell area growth and a much lower ratio of shell weight growth to shell area growth. Differences in shell weight to area ratio indicated that C. virginica dramatically shifted from lateral shell growth to shell thickening in the presence of U. cinerea. This inducible defense has not been previously shown for C. virginica and could play an important role in the predator–prey interaction between these two species.     

Blooms of the dinoflagellate Gyrodinium aureolum in a Long Island estuary:

A dense dinoflagellate bloom of Gyrodinium aureolum Hulburt in a shallow temperate zone estuary was monitored during the summers of 1982 and 1983. The bloom was typically extremely localized, its densest part exceeding 1000g chlorophyll a liter^-1 (2x10⁴ cells ml^-1). The bloom began at temperatures between 24.5° and 27°C, existed at as high as 30°C and terminated when water temperature dropped to between 19° and 22°C. The highest specific growth rate measured was 0.90d^-1 (1.3 divisions d^-1) and near the termination of the bloom decreased to 0.28d^-1 (0.4 divisions d^-1). A diel vertical migration of the bloom was observed. A box model analysis, based on division rates, vertical migration and water circulation patterns, indicated that the bloom must move downward at the estuary mouth to maintain itself in the estuary, either by means of a convergence system or by downward swimming. High growth rate, low grazing pressure, and a stratified water column are proposed to stimulate bloom formation. Decreasing growth rate appeared to reduce the intensity of the bloom and finally allowed its disappearance by estuarine flushing and mixing.Communicated by J. M. Shick, Orono     

Population structure, growth and recruitment of the euryalinid brittle-star Astrobrachion constrictum (Echinodermata: Ophiuroidea) in Doubtful Sound, Fiordland, New Zealand

The euryalinid brittle-star (snake star) Astrobrachion constrictum (Farquhar) lives coiled around the branches of black coral (Antipathes fiordensis) colonies. Twenty-two vertical transects, 10 m wide by 30 m deep, were swum in Doubtful Sound over a 2.5 yr period from 1993 to 1995. Numbers, disc diameters and colour morphotypes of brittle-stars inhabiting coral colonies were recorded. 36.3% of the coral colonies >200 mm tall (n = 292) hosted ≥1 Astrobrachion constrictum (range 0 to 12). Overall, the population was patchily distributed on the available coral habitat. The dark red colour morphotype of A. constrictum was most common (87%, n = 279) followed by the yellow, striped, and then spotted varieties. The population was comprised mainly of large (≥10 mm disc diam) individuals, and juveniles were rarely encountered, indicating low rates of recruitment or a high mortality of recruits. Disc-diameter data gathered from this and previous studies indicated that growth in A. constrictum is initially rapid, with individuals reaching a disc diameter of 15 mm in ≃2.5 yr; growth decreases with age, as in other deep-sea ophiuroids. Growth rate within years, however, was not constant, with faster growth in the spring/summer. Maximum size for A. constrictum is reached in ≃8 yr at ˜23 mm disc diam. Anecdotal evidence indicates that A. constrictum may not be confined solely to black coral colonies. Received: 25 September 1996 / Accepted: 16 October 1996     

Adaptive Units for Conservation: Population Distinction and Historic Extinctions in the Island Scrub-Jay

Abstract:  The Island Scrub-Jay ( Aphelocoma insularis ) is found on Santa Cruz Island, California, and is the only insular bird species in the continental United States. We typed seven microsatellite loci and sequenced a portion of the mitochondrial DNA control region of Island Scrub-Jays and their closest mainland relative, the Western Scrub-Jay ( Aphelocoma californica ), to assess levels of variability and effective population size and to examine the evolutionary relationship between the two species. The estimated female effective population size, N _ef, of the Island Scrub-Jay was 1603 (90% confidence interval: 1481–1738) and was about 7.5% of the size of the mainland species. Island and Western Scrub-Jays have highly divergent control-region sequences, and the value of 3.14 ± 0.09% sequence divergence between the two species suggests a divergence time of approximately 151,000 years ago. Because the four northern Channel Islands were joined as one large island as recently as 11,000 years ago, extinctions must have occurred on the three other northern Channel islands, Santa Rosa, San Miguel, and Anacapa, highlighting the vulnerability of the remaining population. We assessed the evolutionary significance of four island endemics, including the Island Scrub-Jay, based on both genetic and adaptive divergence. Our results show that the Island Scrub-Jay is a distinct species of high conservation value whose history and adaptive potential is not well predicted by study of other island vertebrates.     

Population structure and accumulation of lipids in the ctenophore Mertensia ovum

We studied the abundance, length-frequency distribution and body composition (lipid accumulation) of the ctenophore Mertensia ovum in Kongsfjorden, Svalbard (79°N) between May 2001 and April 2002. The highest abundances were found during summer in the outer and middle areas of the fjord, possibly caused by the concentration of advected zooplankton. Polymodal length-frequencies indicated a life span of 2 years, with 0, 1 and 2-groups being present in summer. Total lipid for a standardized animal decreased from May to August, and increased to the highest level in September. Relative lipid content was always highest in the 0-group, probably reflecting reduction of lipid levels due to increased energy costs during reproduction for the older age groups. Lipids probably are used to fuel prolonged reproduction from May to August until spawning ends by September. The overwintering age groups (0 and 1) subsequently build up lipid reserves for the next years’ spawning.