First Report on the Diversity of Epizoic Algae in Larval of Shellfish Gastropod Aliger gigas

Epibiosis occur frequently on the shells of some marine crustaceans, which often serve as substrate for various species of algae, there is few information on the associations between these. The objective of this study was to determine if the gastropod mollusk Aliger gigas (formerly Lobatus gigas) in larval had some sort of the association with algal. To the above was carried out collecting egg masses in the environment, the larvae were cultivated in seawater filtered 5 μm. The algal material found was observed in electron microscopy, for its identification and quantification. We analyzed 60 larvae aged 2–44 days for analyzing the structure of the shell and its epibionts. Of the larvae analyzed, 50 larvae presented epizoic. The algae community consisted of 28 taxa, and composed of 25 diatoms (Bacillariophyta) and three cyanophytes (Cyanobacteria). The H´ diversity values fluctuated between 0.2 a 1.2. The dominant and frequent species were formed by diatoms: Nitzschia panduriformis var. minor, Halamphora sp. and Cyclophora sp.

Sea-ice associated carbon flux in Arctic spring

The Svalbard region faces drastic environmental changes, including sea-ice loss and “Atlantification” of Arctic waters, caused primarily by climate warming. These changes result in shifts in the sea-ice-associated (sympagic) community structure, with consequences for the sympagic food web and carbon cycling. To evaluate the role of sympagic biota as a source, sink, and transmitter of carbon, we sampled pack ice and under-ice water (0–2 m) north of Svalbard in spring 2015 by sea-ice coring and under-ice trawling. We estimated biomass and primary production of ice algae and under-ice phytoplankton as well as biomass, carbon demand, and secondary production of sea-ice meiofauna (>10 µm) and under-ice fauna (>300 µm). Sea-ice meiofauna biomass (0.1–2.8 mg C m–2) was dominated by harpacticoid copepods (92%), nauplii (4%), and Ciliophora (3%). Under-ice fauna biomass (3.2–62.7 mg C m–2) was dominated by Calanus copepods (54%). Appendicularia contributed 23% through their high abundance at one station. Herbivorous sympagic fauna dominated the carbon demand across the study area, estimated at 2 mg C m–2 day–1 for ice algae and 4 mg C m–2 day–1 for phytoplankton. This demand was covered by the mean primary production of ice algae (11 mg C m–2 day–1) and phytoplankton (30 mg C m–2 day–1). Hence, potentially 35 mg C m–2 day–1 of algal material could sink from the sympagic realm to deeper layers. The demand of carnivorous under-ice fauna (0.3 mg C m–2 day–1) was barely covered by sympagic secondary production (0.3 mg C m–2 day–1). Our study emphasizes the importance of under-ice fauna for the carbon flux from sea ice to pelagic and benthic habitats and provides a baseline for future comparisons in the context of climate change.

Stress factors resulting from the Arctic vernal sea-ice melt

During sea-ice melt in the Arctic, primary production by sympagic (sea-ice) algae can be exported efficiently to the seabed if sinking rates are rapid and activities of associated heterotrophic bacteria are limited. Salinity stress due to melting ice has been suggested to account for such low bacterial activity. We further tested this hypothesis by analyzing samples of sea ice and sinking particles collected from May 18 to June 29, 2016, in western Baffin Bay as part of the Green Edge project. We applied a method not previously used in polar regions—quantitative PCR coupled to the propidium monoazide DNA-binding method—to evaluate the viability of bacteria associated with sympagic and sinking algae. We also measured cis-trans isomerase activity, known to indicate rapid bacterial response to salinity stress in culture studies, as well as free fatty acids known to be produced by algae as bactericidal compounds. The viability of sympagic-associated bacteria was strong in May (only approximately 10% mortality of total bacteria) and weaker in June (average mortality of 43%; maximum of 75%), with instances of elevated mortality in sinking particle samples across the time series (up to 72%). Short-term stress reflected by cis-trans isomerase activity was observed only in samples of sinking particles collected early in the time series. Following snow melt, however, and saturating levels of photosynthetically active radiation in June, we observed enhanced ice-algal production of bactericidal compounds (free palmitoleic acid; up to 4.8 mg L–1). We thus suggest that protection of sinking sympagic material from bacterial degradation early in a melt season results from low bacterial activity due to salinity stress, while later in the season, algal production of bactericidal compounds induces bacterial mortality. A succession of bacterial stressors during Arctic ice melt helps to explain the efficient export of sea-ice algal material to the seabed.

Negligible isotopic fractionation of nitrogen within temperate <i>Zostera</i> spp. meadows

Seagrass meadows form an ecologically important ecosystem in the coastal zone. The 15N∕14N ratio of seagrass is commonly used to assess the extent to which sewage-derived nitrogen may be influencing seagrass beds. There have, however, been few studies comparing the 15N∕14N ratios of seagrass beds, their associated sediments and, of critical importance, the porewater NH4+ pool, which is most bioavailable. Here, we undertook a study of the 15N∕14N ratios of seagrass tissue, sediment porewater NH4+ pool and the bulk sediment to elucidate the extent of any fractionating processes taking place during organic matter mineralisation and nitrogen assimilation. The study was undertaken within two coastal embayments known to receive nitrogen from a range of sources including marine, urban and sewage sources. There was close agreement between the bulk sediment δ15N and seagrass δ15N (r2 of 0.92 and mean offset of 0.9 ‰), illustrating a close coupling between the plant and sediment pools. The δ15N of porewater NH4+ was strongly correlated with the δ15N of both the sediment and the seagrass tissue. For both of these relationships, however, the intercept of the line was not significantly different from 0 and the slopes were not 1:1, reflecting an enrichment of the porewater NH4+ δ15N pool relative to seagrass tissue and bulk sediment δ15N at high δ15N values. We suggest that nitrogen fixation is the most likely explanation for the observation that the δ15N of seagrass tissue is lower than porewater NH4+. Conversely, we suggest that the most likely explanation for the enrichment of porewater NH4+ above bulk sediment was through the preferential mineralisation of isotopically enriched algal material (nitrogen derived from sewage sources) within the sediment as δ15N increased in the vicinity of a sewage treatment plant.

Evolution of a Vegetarian Vibrio: Metabolic Specialization of Vibrio breoganii to Macroalgal Substrates

ABSTRACT While most Vibrionaceae are considered generalists that thrive on diverse substrates, including animal-derived material, we show that Vibrio breoganii has specialized for the consumption of marine macroalga-derived substrates. Genomic and physiological comparisons of V. breoganii with other Vibrionaceae isolates revealed the ability to degrade alginate, laminarin, and additional glycans present in algal cell walls. Moreover, the widely conserved ability to hydrolyze animal-derived polymers, including chitin and glycogen, was lost, along with the ability to efficiently grow on a variety of amino acids. Ecological data showing associations with particulate algal material but not zooplankton further support this shift in niche preference, and the loss of motility appears to reflect a sessile macroalga-associated lifestyle. Together, these findings indicate that algal polysaccharides have become a major source of carbon and energy in V. breoganii, and these ecophysiological adaptations may facilitate transient commensal associations with marine invertebrates that feed on algae. IMPORTANCE Vibrios are often considered animal specialists or generalists. Here, we show that Vibrio breoganii has undergone massive genomic changes to become specialized on algal carbohydrates. Accompanying genomic changes include massive gene import and loss. These vibrios may help us better understand how algal biomass is degraded in the environment and may serve as a blueprint on how to optimize the conversion of algae to biofuels.

Plastic microbeads from cosmetic products: an experimental study of their hydrodynamic behaviour, vertical transport and resuspension in phytoplankton and sediment aggregates

Hydrodynamic behaviour and the transport pathways of microplastics within the ocean environment are not well known, rendering accurate predictive models for dispersal management of such pollutants difficult to establish. In the natural environment, aggregation between plastic microbeads and phytodetritus or suspended sediments in rivers and oceans further complicate the patterns of dispersal. In this laboratory study, the physical characteristics and hydrodynamic behaviour of a selection of common plastic microbeads, as used in exfoliation skincare cosmetic products, were investigated. Additionally, the potential for aggregation of these microbeads with phytodetritus and suspended sediments, as well as the subsequent sinking and resuspension behaviour of produced aggregates, were investigated with roller tanks, settling columns and erosion chamber. Physical characteristics of the plastic microbeads showed great heterogeneity, with various densities, sizes and shapes of plastic material being utilised in products designed for the same purpose. The majority of the plastics investigated were positively buoyant in both freshwater and seawater. Aggregation between plastic microbeads and phytoplankton was observed to be swift, with even extremely high concentrations of plastics being rapidly scavenged by suspended algal material. Following aggregation to sizes of 300 to 4400 μm diameter, some formerly buoyant plastics were observed to settle through the water column and enter the benthic boundary layer with settling velocities ranging between 32 and 831 m day–1. These aggregates could be resuspended in the laboratory under critical shear velocities of 0.67–1.33 cm s–1 (free stream velocities of &gt; 10 cm s–1). This rapid aggregation and subsequent settling indicates a potentially important transport pathway for these waste products, a pathway that should be considered when modelling discharge and transport of plastic microbeads and determining the ecosystems that may be at risk from exposure.

The fractionation of nitrogen and oxygen isotopes in macroalgae during the assimilation of nitrate

In order to determine and understand the stable isotope fractionation of 18O and 15N manifested during assimilation of NO3− in marine macro-benthic algae, two species (Ulva sp. and Agardhiella sp.) have been grown in a wide range of NO3- concentrations (2–500 μM). Two types of experiments were performed. The first was one in which the concentration of the NO3− was allowed to drift downward as it was assimilated by the algae, between 24 h replacements of media. These experiments proceeded for periods of between seven and ten days. A second set of experiments maintained the NO3− concentration at a low steady state value by means of a syringe pump. The effective fractionation during the assimilation of the NO3− was determined by measuring the δ15N of both the (i) new algal growth, and (ii) residual NO3− in the free drift experiments after 0, 12, 24, and 48 h. Fitting models to these data show that the fractionation during assimilation is dependent upon the concentration of NO3− and is effectively zero at concentrations of less than 1 μM. The change in the fractionation with respect to concentration is the greatest at lower concentrations (1–10 μM). The fractionation determined using the δ15N of the NO3− or the solid algal material provided statistically the same result. Therefore, at typical marine concentrations of NO3−, fractionation during assimilation can probably be considered to be negligible. Although the δ18O and δ15N of NO3− in the residual solution were correlated, the slope of the relationship varied with NO3− concentration, with slopes of greater than unity at low concentration. These results suggest shifts in the dominant fractionation mechanism between 1 and 10 μM NO3−. At typical marine concentrations of NO3−, fractionation during assimilation can be considered to be negligible. However, at higher concentrations, fractionation during assimilation will lead to both δ15N values for algal biomass lower than the NO3− source, but also 15N enrichments in the residual NO3−.

Carbon sources in suspended particles and surface sediments from the Beaufort Sea revealed by molecular lipid biomarkers and compound-specific isotope analysis

Molecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids) and compound-specific isotope analysis of suspended particulate organic matter (SPM) and surface sediments of the Mackenzie Shelf and slope (southeast Beaufort Sea, Arctic Ocean) were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the organic matter (OM) of this area. Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and <1%, respectively. In marine SPM from the Mackenzie slope, the major contributions were fresh and detrital algal components (>80%), with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75%), whereas those from the slope contained the highest proportion of fossil (40%) and C3 terrestrial plant material (10%). Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC) found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the sediments accounted for 30–40% of the total carbon in the inner shelf sediments, 17% in the outer shelf and Amundsen Gulf and up to 25% in the slope sediments. These estimates are low compared to other studies conducted 5–20 yr earlier, and they support the increase in primary production during the last decade mainly because of the increase in the number of ice-free days and due to the strength and persistence of winds favouring upwelling.

Carbon sources in the Beaufort Sea revealed by molecular lipid biomarkers and compound specific isotope analysis

Molecular lipid biomarkers (hydrocarbons, alcohols, sterols and fatty acids) and compound specific isotope analysis of suspended particulate organic matter (SPM) and surface sediments of the Mackenzie Shelf and slope (Southeast Beaufort Sea, Arctic Ocean), were studied in summer 2009. The concentrations of the molecular lipid markers, characteristic of known organic matter sources, were grouped and used as proxies to evaluate the relative importance of fresh algal, detrital algal, fossil, C3 terrestrial plants, bacterial and zooplankton material in the sedimentary organic matter (OM). Fossil and detrital algal contributions were the major fractions of the freshwater SPM from the Mackenzie River with ~34% each of the total molecular biomarkers. Fresh algal, C3 terrestrial, bacterial and zooplanktonic components represented much lower percentages, 17, 10, 4 and < 1%, respectively. In marine SPM from the Mackenzie slope, the major contributions were fresh and detrital algal components (> 80%) with a minor contribution of fossil and C3 terrestrial biomarkers. Characterization of the sediments revealed a major sink of refractory algal material mixed with some fresh algal material, fossil hydrocarbons and a small input of C3 terrestrial sources. In particular, the sediments from the shelf and at the mouth of the Amundsen Gulf presented the highest contribution of detrital algal material (60–75%) whereas those from the slope contained the highest proportion of fossil (40%) and C3 terrestrial plant material (10%). Overall, considering that the detrital algal material is marine derived, autochthonous sources contributed more than allochthonous sources to the OM lipid pool. Using the ratio of an allochthonous biomarker (normalized to total organic carbon, TOC) found in the sediments to those measured at the river mouth water, we estimated that the fraction of terrestrial material preserved in the sediments accounted for 30–40% of the total carbon in the inner shelf sediments, 17% in the outer shelf and Amundsen Gulf and up to 25% in the slope sediments.

Complex noncalcified macroalgae from the Silurian of Cornwallis Island, Arctic Canada

Thin beds of silty limestone within a Ludlovian (Ludfordian) section of the Cape Phillips Formation on Cornwallis Island, Arctic Canada, contain numerous specimens of noncalcified macroalgae in association with dendroid and graptoloid graptolites, brachiopods, and trilobites. The algal material, preserved as carbonaceous compressions, represents three new taxa, each characterized by a central axis surrounded by laterals. Laterals ofEocladus xiaoin. gen. n. sp. are thin and branch to the fifth order whereas those ofChaetocladus captitatusn. sp. are undivided and form a distinctive capitulum. Thalli ofPalaeocymopolia nunavutensisn. gen. n. sp. have a branched, serial-segmented form and a corticated structure. On the basis of thallus architecture, all three taxa are assigned to the extant green algal order Dasycladales. Parallels exist between this macroalgal assemblage and a modern macroalgal association in Florida Bay.