Communities In Water Column Research Articles

Protistan Diversity in the Arctic: A Case of Paleoclimate Shaping Modern Biodiversity?

BackgroundThe impact of climate on biodiversity is indisputable. Climate changes over geological time must have significantly influenced the evolution of biodiversity, ultimately leading to its present pattern. Here we consider the paleoclimate data record, inferring that present-day hot and cold environments should contain, respectively, the largest and the smallest diversity of ancestral lineages of microbial eukaryotes.Methodology/Principal FindingsWe investigate this hypothesis by analyzing an original dataset of 18S rRNA gene sequences from Western Greenland in the Arctic, and data from the existing literature on 18S rRNA gene diversity in hydrothermal vent, temperate sediments, and anoxic water column communities. Unexpectedly, the community from the cold environment emerged as one of the richest observed to date in protistan species, and most diverse in ancestral lineages.Conclusions/SignificanceThis pattern is consistent with natural selection sweeps on aerobic non-psychrophilic microbial eukaryotes repeatedly caused by low temperatures and global anoxia of snowball Earth conditions. It implies that cold refuges persisted through the periods of greenhouse conditions, which agrees with some, although not all, current views on the extent of the past global cooling and warming events. We therefore identify cold environments as promising targets for microbial discovery.

The hyperbenthic plankton community: composition, distribution, and abundance in a coral reef lagoon

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 336:77-88 (2007) - doi:10.3354/meps336077 The hyperbenthic plankton community: composition, distribution, and abundance in a coral reef lagoon J. H. Carleton1,*, W. M. Hamner2 1Australian Institute of Marine Science, PMB No. 3, Townsville Mail Centre, Queensland 4810, Australia 2Department Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California 90290, USA *Email: j.carleton@aims.gov.au ABSTRACT: Seasonal and diel variations in community structure and abundance of the lagoon hyperbenthic community were examined at Davies Reef, Great Barrier Reef. The lagoon floor community differed from that in the overlying water, it was faunistically more uniform, and it was assembled into statistically distinct seasonal and diel groupings. The lagoon floor community was characterized by reef-associated mysids, gammarids, calanoids, ostracods, harpacticoids, cyclopoids, nematodes, caprellids, and cumaceans. The community was most distinctive in October. The water column community had greater diel than seasonal variability. The nocturnal water column community was characterized by decapod larvae, zoea, larvaceans, fish larvae, gastropod larvae, and nauplii, but was dominated numerically by calanoid copepods (>60%). Catches on the lagoon floor ranged from 750 to 3330 ind. m–3, with peak abundance in October, while water column catches were lower (25 to 2500 ind. m–3), with peak nocturnal abundance in February. Most species in the hyperbenthic community do not migrate into the water column at night, but instead remain concentrated near the lagoon floor. Only the mysid Anisomysis laticauda, the copepod Acartia australis, and the ostracod Cypridina sp. A were consistently captured on the lagoon floor by day and in surface waters at night. The lagoon hyperbenthic community probably contributes to coral reef ecosystems through the remineralization of organic detritus. Given the high abundance of relatively large individuals, the contribution of the resident, lagoon floor community to coral reef ecosystems must be substantial. KEY WORDS: Hyperbenthos · Plankton · Coral reef lagoon · Community structure Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 336. Online publication date: April 27, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Oil well produced water discharges to the North Sea. Part II: Comparison of deployed mussels (Mytilus edulis) and the DREAM model to predict ecological risk

Large volumes of water often are produced with oil and gas from offshore platforms. The produced water is separated from the oil and gas and either reinjected into a deep formation or discharged to the ocean. The Norwegian oil and gas industry advocates ecological risk assessment as the basis for managing produced water discharges to the North Sea. In this paper, we compare estimates of ecological risks to water-column communities based on data on hydrocarbon residues in soft tissues of blue mussels deployed for a month near offshore platforms and based on predictions of the Dose related Risk and Effect Assessment Model (DREAM). The study was performed near produced water discharges to the Tampen and Ekofisk Regions of the Norwegian Sector of the North Sea. Because polycyclic aromatic hydrocarbons (PAH) are considered the most important contributors to the ecological hazard posed by produced water discharges, comparisons made here focus on this group of compounds. The mussel approach is based on predicted environmental concentrations (PECs) of individual PAH, estimated from PAH residues in mussels following deployment for a month near several produced water discharges, and predicted no effects concentrations (PNECs) based on a K(ow) regression model. In the DREAM method, PECs for three PAH fractions are estimated in the three-dimensional area around produced water discharge with the DREAM model. PNECs for each fraction are based on the chronic toxicity of a representative PAH from each fraction divided by an assessment factor to account for uncertainty in the chronic value. The mussel method gives much lower estimates of ecological risk than the DREAM method. The differences are caused by the much lower PNECs used in DREAM than derived from the regression model, and by the lower concentrations of aqueous PAH predicted by DREAM than estimated from PAH residues in mussel tissues. However, the two methods rank stations at different distances from produced water discharges in the same order and both identify 2- and 3-ring PAHs as the main contributors to the ecological risk of produced water discharges. Neither method identifies a significant ecological risk of PAH in the upper water column of the oil fields. The DREAM model may produce an overly conservative estimate of ecological risk of produced water discharges to the North Sea.

Spatial and vertical biogeography of coral reef sediment bacterial and diazotroph communities

Coral reefs are globally important marine ecosystems as sites of high biotic diversity. Reef flat sediments are reasonably homogeneous in composition. This substratum is subject to gradi- ents in water motion, grazing pressure and benthic productivity. This study used DNA fingerprinting techniques, automated rRNA intergenic spacer analysis (ARISA), and terminal restriction fragment length polymorphism (TRFLP) to examine patterns of bacterial assemblage composition within Heron Reef flat sediments, targeting the entire bacterial community (not including Archaea) and nitrogen- fixing bacteria. ARISA fingerprints contained between 51 and 148 operational taxonomic units (OTU) per surface sediment sample. The mean whole-community similarity between adjacent sites along a transect from Heron Island to the reef crest was 0.50 ± 0.03 (mean ± SE) Whittaker Index (comparison of relative abundances) and 0.46 ± 0.03 Jaccard Index (presence/absence only). Comparison of sedi- ment community fingerprints to a water column community fingerprint collected above the reef flat at high tide indicated that sediments contained different assemblages to the water column (mean similarity between sediments and water column assemblage = 0.15 ± 0.01 Jaccard Index); however, assemblage composition did not differ significantly from that expected by random association. Verti- cal sediment cores showed dissimilarity between surface (0 to 3 cm) and deep (3 to 5 cm) community fingerprints, which was probably related to redox state. Comparison of fingerprints of fecally-derived sediments from the sea cucumber Holothuria atra and surrounding sediments indicated that the impact of metazoan grazing could not be distinguished from ambient small spatial scale variability in sediment assemblage composition. The nifH-TRFLP fingerprints of sediment prokaryotic assem- blages (amplified from all samples, but only in sufficient quantities for analysis from 7 locations) indi- cated the presence of ubiquitous, potentially diverse diazotroph communities, with little assemblage similarity between locations. Our results suggested that while bacterial assemblages (including communities of nitrogen-fixing bacteria) in sediments of a coral reef are diverse, their assemblage composition is not related to grazing pressure but may be influenced by other biotic and abiotic environmental conditions such wave energy and sediment depth.

Method for Collecting Air-Water Interface Microbes Suitable for Subsequent Microscopy and Molecular Analysis in both Research and Teaching Laboratories

A method has been developed for collecting air-water interface (AWI) microbes and biofilms that enables analysis of the same sample with various combinations of bright-field and fluorescence light microscopy optics, scanning and transmission electron microscopy (TEM), and atomic force microscopy. The identical sample is then subjected to molecular analysis. The sampling tool consists of a microscope slide supporting appropriate substrates, TEM grids, for example, that are removable for the desired protocols. The slide with its substrates is then coated with a collodion polymer membrane to which in situ AWI organisms adhere upon contact. This sampling device effectively separates the captured AWI bacterial community from the bulk water community immediately subtending. Preliminary data indicate that the AWI community differs significantly from the water column community from the same sample site when both are evaluated with microscopy and with 16S ribosomal DNA sequence-based culture-independent comparisons. This microbe collection method can be used at many levels in research and teaching.

Learnings from the Texas Nearshore Dispersant Demonstration Project

ABSTRACT This project defines circumstances where a dispersant demonstration might be considered for an estuarine oil spill in Texas. In seeking approval for a spill of opportunity demonstration project, we developed criteria defining a viable dispersant response for consideration by the Region VI Regional Response Team. This paper presents the criteria and their rationale developed for Galveston Bay and Corpus Christi Bay, along with the results of recent training exercises. The criteria define the size and general location of an oil spill that might be considered appropriate for a trial dispersant application, and implementation of response and monitoring within a 2-hour window from notification. They are based on descriptions and characterizations of the habitats and species at risk in coastal areas, concentration and duration of dispersed oil plumes that might be generated in a response, potential impacts of these exposures, and the environmental trade-off between implementing mechanical response and a dispersant response. Because the dilution potential is constrained in shallow water environments, spill size has significant impact on the magnitude and duration of potential exposure regimes for water column organisms. Spills of 250 bbls or less pose minimal concern for water column communities with potential net benefit to other coastal resources. The trade-offs were not so obvious for larger spills. The exposure regimes and potential impacts for water-column organisms that would be maximally exposed during a dispersant operation were compared to the exposures and potential impacts for organisms and habitats exposed to floating oil and oil stranded on shorelines, at levels that could result during a mechanical recovery operation. These potential impacts are compared on a spatial and temporal basis, and with consideration for potential rates of recovery.

Population biology and secondary production of the suspension feeding polychaete Chaetopterus cf. variopedatus: Implications for benthic‐pelagic coupling in lower Chesapeake Bay

Benthic suspension feeders are functionally important components of many shallow estuarine and coastal ecosystems. Their relative importance in material and energy cycling depends on physical and biological factors, of which population dynamics of individual species are a key feature. We studied the demographics and secondary production of a population of the tubicolous, suspension feeding polychaete, Chaetopterus cf. variopedatus, of southern Chesapeake Bay, Virginia, to better understand its functional role in an estuarine ecosystem. Average worm densities in the study region ranged from 30 to >1000 individuals m−2 and were greatest after the summer recruitment period. Recruitment success varied threefold between 1994 and 1995. A two‐cohort model (juveniles and adults) with seasonality best described the data. High secondary production (18 g C m−2 yr−1 in 1994, 34 g C m−2 yr−1 in 1995) was mainly due to rapid growth and maturation of new recruits during summer and tube production. An interannual difference in production was associated with the interannual difference in recruitment success. General temporal trends of primary production and worm production were similar, and the worm population required 35%–100% of the estimated annual net water column community production per m2 for this region of the estuary. Chaetopterus cf. variopedatus is an important component of the lower bay ecosystem and should be considered when modeling carbon, nutrient, and energy flow. Our results further demonstrate that temporal variations in population dynamics lead to significant temporal variability in the relative importance of benthic suspension feeder effects for ecosystem function.

Protozoan Bacterivory in the Ice and the Water Column of a Cold Temperate Lagoon.

> Abstract Bacterial abundance and bacterivorous protist abundance and activity were examined in ice-brine and water column communities of a cold temperate Japanese lagoon (Saroma-Ko Lagoon, Hokkaido, 44 degreesN, 144 degreesE), during the late winter phase of ice community development (February-March 1992). Bacterial abundance averaged 6 and 1 x 10(5) cells ml-1 in the ice-brine and plankton samples, respectively, and generally decreased during the sampling period. Bacterivorous protists, identified based on direct observation of short-term (<1 h) ingested fluorescently labeled bacteria (FLB) in their food vacuoles, were largely dominated by flagellates, mainly cryothecomonad-type and chrysomonad-like cells and small dinoflagellates of the genus Gymnodinium. Bacterivorous ciliates included mainly the prostomatid Urotricha sp., the scuticociliates Uronema and Cyclidium, the choreotrichs Lohmaniella oviformis and Strobilidium, and the hypotrich Euplotes sp. Protist abundance averaged 4 x 10(3) and 8.1 cells ml-1 in the ice-brine and 0.3 x 10(3) and 1.2 cells ml-1 in the plankton, for flagellates and ciliates, respectively. In contrast to bacteria, the abundance of protists generally increased throughout the sampling period, indicating predator-prey interactions. Protistan bacterivory, measured from the rate of FLB disappearance over 24 h, averaged 36% (ice) and 24% (plankton) of bacterial standing stock and exhibited the same seasonal pattern as for protist abundance. The calculated specific clearance (range, 2-67 nl protozoa-1 h-1) and ingestion (<1-26 particles protozoa-1 h-1) rates were likely to be minimal estimates and grazing impact may have been higher on occasion. Indications for the dependence of "bacterivorous protists" on nonbacterial food items were also provided. Although alternative sources of bacterial loss are likely to be of importance, this study provides evidence for the potential of protozoan assemblages as bacterial grazers in both sea ice-brine biota and water column at the southern limit of sea ice in the northern hemisphere.

Application of molecular biological techniques to a seasonal study of ammonia oxidation in a eutrophic freshwater lake

The autotrophic ammonia-oxidizing bacteria in a eutrophic freshwater lake were studied over a 12-month period. Numbers of ammonia oxidisers in the lakewater were small throughout the year, and tangential-flow concentration was required to obtain meaningful estimates of most probable numbers. Sediments from littoral and profundal sites supported comparatively large populations of these bacteria, and the nitrification potential was high, particularly in summer samples from the littoral sediment surface. In enrichment cultures, lakewater samples nitrified at low (0.67 mM) ammonium concentrations only whereas sediment samples exhibited nitrification at high (12.5 mM) ammonium concentrations also. Enrichments at low ammonium concentration did not nitrify when inoculated into high-ammonium medium, but the converse was not true. This suggests that the water column contains a population of ammonia oxidizers that is sensitive to high ammonium concentrations. The observation of nitrification at high ammonium concentration by isolates from some winter lakewater samples, identified as nitrosospiras by 16S rRNA probing, is consistent with the hypothesis that sediment ammonia oxidizers enter the water column at overturn. With only one exception, nested PCR amplification enabled the detection of Nitrosospira 16S rDNA in all samples, but Nitrosomonas (N. europaea-eutropha lineage) 16S rDNA was never obtained. However, the latter were part of the sediment and water column communities, because their 16S rRNA could be detected by specific oligonucleotide probing of enrichment cultures. Furthermore, a specific PCR amplification regime for the Nitrosomonas europaea ammonia monooxygenase gene (amoA) yielded positive results when applied directly to sediment and lakewater samples. Patterns of Nitrosospira and Nitrosomonas detection by 16S rRNA oligonucleotide probing of sediment enrichment cultures were complex, but lakewater enrichments at low ammonium concentration were positive for nitrosomonads and not nitrosospiras. Analysis of enrichment cultures has therefore provided evidence for the existence of subpopulations within the lake ammonia-oxidizing community distinguishable on the basis of ammonium tolerance and possibly showing a seasonal distribution between the sediment and water column.

Diversity and Geographic Distribution of Free-Living Heterotrophic Flagellates – Analysis by PRIMER

Data on the distribution of approximately 350 species of heterotrophic flagellates (protozoa) in 31 communities from sites around the world - inclusive of marine and freshwater habitats, water column and benthic habitats, and 'extreme' (i.e. anoxic and hypersaline) habitats - are analysed by the Cluster algorithm in the PRIMER package. We have sought to minimise the impact of factors extrinsic to the actual distribution of organisms which may distort our perception of the geographic patchiness of organisms. In our analyses, communities from areas which are geographically close to each other do not cluster together. Communities from similar habitats cluster together (i.e., water column communities group together, as do benthic communities, or freshwater and marine communities), and communities from more unusual habitats segregate from those of less 'extreme' habitats. We argue that our capacity to draw robust conclusions on the distribution of these organisms is hampered by under-reporting. We favour a model in which there are relatively few species of free-living heterotrophic flagellates, and that most of these species have a cosmopolitan distribution.

Choanoflagellates (acanthoecidae, choanoflagellida) from the Weddell Sea, Antarctica, Taxonomy and community structure with particular emphasis on the ice biota; with preliminary remarks on choanoflagellates from Arctic sea ice (Northeast Water Polynya, Greenland)

Summary Ice biota studies in the Antarctic region, Weddell Sea, have focused on an examination of single cells and an analysis of community structure of the flagellate assemblage from sea ice and comparisons with planktonic assemblages. Based on extensive light microscopical analysis of 40 samples ranging from open water to “brown-ice” habitats, it became evident through clustering of the data, that the mature choanoflagellate community from ice is significantly different from both the water column community and those encountered in samples derived from newly formed ice (i.e. grease ice, platelet ice, nilas and thin pancakes). The choanoflagellates from sea ice encompasses a range of previously undescribed loricate taxa ( Acanthocorbis nana sp. nov., A. weddellensis sp. nov., A. prolongata sp. nov., Apheloecion antarctica sp. nov., A. glacialis sp. nov., A. conicoides sp. nov., Calliacantha frigida sp. nov., C. ankyra sp. nov., Diaphanoeca multiannulata subsp. nov. glacialis, Parvicorbicula corynocostata sp. nov., P. pachycostata sp. nov.). These taxa have been investigated using a combination of light, and electron microscopy. A preliminary investigation of samples from the Arctic (NE Greenland) indicates that the loricate choanoflagellate diversity is significantly lower in Arctic sea ice.

Springtime coupling between ice algal and phytoplankton assemblages in southeastern Hudson Bay, Canadian Arctic

Microalgal assemblages from the bottom ice, the ice-water interface and the water column were systematically sampled from April to June 1986, in southeastern Hudson Bay (Canadian Arctic). The taxonomic similarity between samples from the three environments was assessed using a clustering procedure. There were two groups that comprised samples from both the ice-water interface and the water column, while five other groups were made of samples originating from a single environment. Taxonomic compositions of the two mixed groups suggest two types of connexion between the ice-water interface and the water column, i.e. before the phytoplankton bloom, there was seeding of the water column by ice algae and, during ice melt, interfacial algae contributed to the water column communities that were otherwise typically phytoplankton. Overall, the phytoplankton community underwent a succession from pennate to centric diatoms. Sinking rates of algae from the ice-water interface were estimated using settling columns (SETCOL). The sinking rates increased seasonally (0.4–2.7 m d−1), which enhanced accessibility of ice-algal cells to the pelagic grazers. Ice algae contributed to water column production as they became accessible to the pelagic grazers, and also by seeding the water column before the phytoplankton bloom.

Sources and relative reactivities of amino acids, neutral sugars, and lignin in an intermittently anoxic marine environment

A sediment-trap sample, representing an annual average particle flux at 50 m in Saanich Inlet, British Columbia, was analyzed for its elemental, amino acid, neutral sugar, and lignin composition. Amino acid analyses also were performed on underlying sediments which were analyzed previously for organic carbon, nitrogen, neutral sugars, and lignin. The results uniformly indicate primarily marine organic matter sources for all samples, although relatively higher terrigenous contributions are evident in the sediments. The δ 13 C values of trap materials also point to primarily autochthonous particle fluxes. Comparison of annual average water-column fluxes to sediment accumulation rates indicates under-sampling of sinking particles due to lateral sediment inputs at depth. The anoxic benthic interface appears to be an important site of diagenesis, and selective removal is observed both at compound-class and molecular levels. Cinnamyl and syringyl phenols are selectively removed relative to vanillyl phenols and loss patterns of the monosaccharides, and to a lesser degree the amino acids, strongly indicate preferential preservation of diatom cell-wall materials. Low flux ratios displayed by the nonprotein amino acids are consistent with their diagenetic origin. Preferential loss of marine organic material is indicated by the calculated δ 13 C value and biochemical composition of the substrate. Concentrations of all measured organic constituents decreased with depth in the uniformly varved 0–14 cm sediment interval, and suggest in situ degradation. Relative reactivities of the biochemical classes indicate a change in diagenetic substrate from that utilized above and at the benthic interface. With the exception of the amino acids, however, diagenesis is generally less selective in the sediments. The amino acid utilization pattern differs from that observed across the benthic interface, and down-core changes in protein and nonprotein amino acid compositions clearly indicate in situ degradation. The sedimentary degraded fraction also appears to be predominantly marine, but lignin yields and sugar compositions suggest a relative increase in the utilization of vascular plant remains. Protein, polysaccharide, and lignin contributions to total organic carbon decrease from 37% in the sediment-trap sample to 22% at the bottom of the 0–14 cm sediment interval. These biochemicals represent over 40 and 50–60% of the degraded carbon and nitrogen, respectively, and thus are important nutrients for the benthic and water-column communities.

Primary productivity and particulate organic matter flow in an estuarine mangrove-wetland in Hong Kong

Net primary productivity and organic matter flow of a mangrove-dominated wetland was estimated by following production and detritus dynamics in a tidal pond in north west Hong Kong in 1986–1988 (9.1 ha). Total productivity was 12.47 t dry wt ha−1 yr−1, of which >90% was from emergent macrophytes (the mangroveKandelia candel and the reedPhragmites communis). High turbidity and high summer temperatures probably limited respective production by phytoplankton and benthic macroalgae (dominated byEnteromorpha crinata). Despite the high total productivity, little detritus was exported from the emergent macrophyte stands, due to the low inundation frequency. This created a net water column carbon deficit which was provided for by the high organic matter import (mean = 4.42 g ash free dry wt m−2 d−1) from the incoming water. This same sediment and particulate organic carbon input giving a high accretion rate of 1.7 cm yr−1 was probably also the force behind progressive dis-coupling of emergent macrophyte production from water column consumers. This resulted in a tendency to retain production in the emergent macrophyte stands while the water column community increasingly relied on allochthonous carbon. This shift from a net exporter to a net importer of carbon in landward wetlands is probably characteristic of the transition into nutrient-conservative terrestrial systems.

The macrozooplankton community of Kosterfjorden, western Sweden. Abundance, biomass, and preliminary data on the life cycles of dominant species

Abstract The macrozooplankton abundance and biomass in Kosterfjorden (58°52' N, 11°06' E) were heavily dominated by the copepod Calanus finmarchicus/helgolandicus, euphausiid species being only temporarily important during summer. Carnivorous species contributed significantly, mainly in winter and spring. A comparison of zooplankton biomasses from coastal areas in Sweden and Norway indicates a direct relationship between water-column depth and community biomass. The macrozooplankton fauna in Kosterfjorden resembles that of Korsfjorden, western Norway by a similarity in the ranking of the quantitatively most important species. The siphonophore Dimophyes arctica, the polychaete Tomopteris helgolandica, and the crustaceans Chiridius armatus, Thysanoessa raschii, and {iParathemisto abyssorum} are more important in the former area, the crustaceans Calanus hyperboreus and Boreomysis arctica, and the chaetognath Eukrohnia hamata in the latter area. Analyses of the seasonal succession in the size structure and st...

Response of the microflora in outdoor experimental streams to pentachlorophenol: compartmental contributions.

Outdoor artificial streams were treated continuously with pentachlorophenol (PCP) for 88 days during the summer of 1983. The contributions of different stream compartments (microbial habitats) to microbial degradation of PCP were determined in a stream treated with 144 micrograms of PCP per liter. The 488-m long stream was composed of mud-bottomed pools alternating with gravel riffles. PCP loss in the stream attributable to microbial degradation after an adaptation period was in the range of 55 to 74%. Contributions to PCP loss were determined for rock surface (epilithic), macrophyte surface (epiphytic), sedimentary, and water column communities by measuring rates of PCP disappearance in stream water, containing ambient concentrations of PCP, in contact with representative compartmental samples. The specific capability, in units of micrograms of PCP per hour per square meter of stream cross-sectional area (macrophytes at maximum plant density, water column at mean depth, upper 10-cm layer of gravel), followed the order rock surface much greater than macrophytes greater than sediment approximately equal to water column. The compartmental contribution to total stream losses in units of grams per hour followed the same order, although the differences were smaller. The rate of PCP disappearance in the water column above sediment cores followed the order oxygen-rich greater than oxygen-poor approximately equal to anaerobic greater than sorption-only conditions. The large difference in specific capability between the rock surface and sediment compartments could be attributed to oxygen deficiency (because of chemical and biological oxygen demand) in the sediments. Free-floating and particle-attached organisms in the water column were important to PCP biodegradation.