Sinking Jelly-Carbon Unveils Potential Environmental Variability along a Continental Margin

Particulate matter export fuels benthic ecosystems in continental margins and the deep sea, removing carbon from the upper ocean. Gelatinous zooplankton biomass provides a fast carbon vector that has been poorly studied. Observational data of a large-scale benthic trawling survey from 1994 to 2005 provided a unique opportunity to quantify jelly-carbon along an entire continental margin in the Mediterranean Sea and to assess potential links with biological and physical variables. Biomass depositions were sampled in shelves, slopes and canyons with peaks above 1000 carcasses per trawl, translating to standing stock values between 0.3 and 1.4 mg C m2 after trawling and integrating between 30,000 and 175,000 m2 of seabed. The benthopelagic jelly-carbon spatial distribution from the shelf to the canyons may be explained by atmospheric forcing related with NAO events and dense shelf water cascading, which are both known from the open Mediterranean. Over the decadal scale, we show that the jelly-carbon depositions temporal variability paralleled hydroclimate modifications, and that the enhanced jelly-carbon deposits are connected to a temperature-driven system where chlorophyll plays a minor role. Our results highlight the importance of gelatinous groups as indicators of large-scale ecosystem change, where jelly-carbon depositions play an important role in carbon and energy transport to benthic systems

Deep-Sea Nematodes Actively Colonise Sediments, Irrespective of the Presence of a Pulse of Organic Matter: Results from an In-Situ Experiment

A colonisation experiment was performed in situ at 2500 m water depth at the Arctic deep-sea long-term observatory HAUSGARTEN to determine the response of deep-sea nematodes to disturbed, newly available patches, enriched with organic matter. Cylindrical tubes,laterally covered with a 500 µm mesh, were filled with azoic deep-sea sediment and 13C-labelled food sources (diatoms and bacteria). After 10 days of incubation the tubes were analysed for nematode response in terms of colonisation and uptake. Nematodes actively colonised the tubes,however with densities that only accounted for a maximum of 2.13% (51 ind.10 cm−2) of the ambient nematode assemblages. Densities did not differ according to the presence or absence of organic matter, nor according to the type of organic matter added. The fact that the organic matter did not function as an attractant to nematodes was confirmed by the absence of notable 13C assimilation by the colonising nematodes. Overall, colonisationappears to be a process that yields reproducible abundance and diversity patterns, with certain taxa showing more efficiency. Together with the high variability between the colonising nematode assemblages, this lends experimental support to the existence of a spatio-temporal mosaic that emerges from highly localised, partially stochastic community dynamics

Carbohydrate-active enzymes from the zygomycete fungus Rhizopus oryzae: a highly specialized approach to carbohydrate degradation depicted at genome level

<p>Abstract</p> <p>Background</p> <p><it>Rhizopus oryzae </it>is a zygomycete filamentous fungus, well-known as a saprobe ubiquitous in soil and as a pathogenic/spoilage fungus, causing Rhizopus rot and mucomycoses.</p> <p>Results</p> <p>Carbohydrate Active enzyme (CAZy) annotation of the <it>R. oryzae </it>identified, in contrast to other filamentous fungi, a low number of glycoside hydrolases (GHs) and a high number of glycosyl transferases (GTs) and carbohydrate esterases (CEs). A detailed analysis of CAZy families, supported by growth data, demonstrates highly specialized plant and fungal cell wall degrading abilities distinct from ascomycetes and basidiomycetes. The specific genomic and growth features for degradation of easily digestible plant cell wall mono- and polysaccharides (starch, galactomannan, unbranched pectin, hexose sugars), chitin, chitosan, β-1,3-glucan and fungal cell wall fractions suggest specific adaptations of <it>R. oryzae </it>to its environment.</p> <p>Conclusions</p> <p>CAZy analyses of the genome of the zygomycete fungus <it>R. oryzae </it>and comparison to ascomycetes and basidiomycete species revealed how evolution has shaped its genetic content with respect to carbohydrate degradation, after divergence from the Ascomycota and Basidiomycota.</p

The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

The Mediterranean Sea is a marine biodiversity hot spot. Here we combined an extensive literature analysis with expert opinions to update publicly available estimates of major taxa in this marine ecosystem and to revise and update several species lists. We also assessed overall spatial and temporal patterns of species diversity and identified major changes and threats. Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea. However, our estimates of marine diversity are still incomplete as yet—undescribed species will be added in the future. Diversity for microbes is substantially underestimated, and the deep-sea areas and portions of the southern and eastern region are still poorly known. In addition, the invasion of alien species is a crucial factor that will continue to change the biodiversity of the Mediterranean, mainly in its eastern basin that can spread rapidly northwards and westwards due to the warming of the Mediterranean Sea. Spatial patterns showed a general decrease in biodiversity from northwestern to southeastern regions following a gradient of production, with some exceptions and caution due to gaps in our knowledge of the biota along the southern and eastern rims. Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth. Temporal trends indicated that overexploitation and habitat loss have been the main human drivers of historical changes in biodiversity. At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves (and in particular, the Strait of Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well

Soft-walled monothalamous and Nodellum-like foraminifera and gromiids (Protista) at the Håkon-Mosby Mud Volcano (Barents Sea slope)

We describe the occurrence of basal (‘primitive’) foraminifera and gromiids (a distinct taxon related to the foraminifera) in different bathyal habitats of the Håkon Mosby Mud Volcano (HMMV, Barents Sea). The foraminifera include two distinct groupings: (1) soft-shelled monothalamous foraminifera (‘allogromiids’, ‘saccamminids’ and ‘psammosphaerids’) and (2) brown organic-walled foraminifera (genera Conicotheca, Nodellum, Placopsilinella and Resigella). Samples were analysed from (1) the ‘hot centre’ of the volcano where fluid upflow was maximal; (2) smooth and structured muds in a ‘warm’ area of the centre where fluid upflow was reduced; (3) areas covered by Beggiatoa mats; (4) an area colonised by siboglinid polychaetes (‘pogonophores’); and (5) areas of ‘normal’ seafloor outside the volcano. Together, the studied organisms represented 57.8 % (‘normal’ seafloor; n?=?418), 28.5 % (‘warm centre’; n?=?122), and 26.4 % (Beggiatoa mats; n?=?5) of all ‘live’ (stained) foraminifera in three samples (0–1 cm layer) that were sorted for all stained foraminifera. In total, the 17 samples examined yielded 21 ‘allogromiid’ (organic-walled), 25 ‘saccamminid’ (agglutinated) and 5 other morphospecies among the monothalamous foraminifera, as well as 5 ‘brown-walled’ and 5 gromiid morphospecies. Four taxa were identified to species (Conicotheca nigrans, Resigella moniliforme, R. polaris, Micrometula hyalinosphaera); another seven were assigned to the genera Bathyallogromia, Conqueria, Nodellum, Placopsilinella, Resigella, Tinogullmia and Vanhoeffenella. All others were undescibed at the genus level. Some species, notably ‘Saccamminid sp. 5’, C. nigrans and Nodellum sp., were distributed in sediment layers down to 5 cm depth, and sausage-shaped gromiids were also present in the deeper layers of some samples. The number of basal foraminiferal and gromiid morphospecies varied considerably from site to site. It was relatively high north of the volcano (42 morphospecies in 4 samples) and in the ‘warm centre’ (28 morphospecies in 2 samples), somewhat lower southwest of the volcano (at least 13 morphospecies in 2 samples) and in the siboglinid field (14 morphospecies in three samples), and substantially reduced in the bacterial mat area (5 morphospecies in 6 samples). The scarcity of these protists at the bacterial mat sites is probably a consequence of high sulfide concentrations. No stained foraminifera or gromiids were observed at the ‘hot centre’ site. In general, assemblages from within and around the HMMV resembled those reported from other bathyal sites, notably in the Porcupine Seabight. Saccamminid sp. 5, by far the most common species in our samples, belongs to a ‘lamp-like’ morphotype that is widely distributed in the oceans. The wall structure, and the presence of what appears to be an internal partition across the base of the neck, is reminiscent of some komokiaceans

Recolonisation of new habitats by meiobenthic organisms in the deep Arctic Ocean: an experimental approach

Commercial exploitation and abrupt changes of the natural conditions may have severe impacts on the Arctic deep-sea ecosystem. The present recolonisation experiment mimicked a situation after a catastrophic disturbance (e.g. by turbidites caused by destabilized continental slopes after methane hydrate decomposition) and investigated if the recolonisation of a deep-sea habitat by meiobenthic organisms is fostered by variations innutrition and/or sediment structure. Two "Sediment Tray Free Vehicles" were deployed for one year in summer 2003 at 2500 m water depth in the Arctic deep-sea in the eastern Fram Strait. The recolonisation trays were filled with different artificial and natural sediment types (glass beads, sand, sediment mixture, pure deep-sea sediment) and were enriched with various types of food (algae, yeast, fish). After one year, meiobenthos abundances and various sediment related environmental parameters were investigated. Foraminifera were generally the most successful group: they dominated all treatments and accounted for about 87% of the total meiobenthos. Colonizing meiobenthos specimens were generally smaller compared to those in the surrounding deep-sea sediment, suggesting an active recolonisation by juveniles. Although experimental treatments with fine-grained, algaeenriched sediment showed abundances closest to natural conditions, the results suggest that food availability was the main determining factor for a successful recolonisation by meiobenthos and the structure of recolonised sediments was shown to have a subordinate influence