Seasonal shelf-sea front mapping using satellite ocean colour and temperature to support development of a marine protected area network

Front detection and aggregation techniques were applied to 300m resolution MERIS satellite ocean colour data for the first time, to describe frequently occurring shelf-sea fronts near to the Scottish coast. Medium resolution (1km) thermal and colour data have previously been used to analyse the distribution of surface fronts, though these cannot capture smaller frontal zones or those in close proximity to the coast, particularly where the coastline is convoluted. Seasonal frequent front maps, derived from both chlorophyll and SST data, revealed a number of key frontal zones, a subset of which were based on new insights into the sediment and plankton dynamics provided exclusively by the higher-resolution chlorophyll fronts. The methodology is described for applying colour and thermal front data to the task of identifying zones of ecological importance that could assist the process of defining marine protected areas. Each key frontal zone is analysed to describe its spatial and temporal extent and variability, and possible mechanisms. It is hoped that these tools can provide guidance on the dynamic habitats of marine fauna towards aspects of marine spatial planning and conservation.

Shallow water methane-derived authigenic carbonate mounds at the Codling Fault Zone, western Irish Sea

Methane-derived authigenic carbonate (MDAC) mound features at the Codling Fault Zone (CFZ), located in shallow waters (50-120m) of the western Irish Sea were investigated and provide a comparison to deep sea MDAC settings. Carbonates consisted of aragonite as the major mineral phase, with δ¹³C depletion to -50‰ and δ¹⁸O enrichment to~2‰. These isotope signatures, together with the co-precipitation of framboidal pyrite confirm that anaerobic oxidation of methane (AOM) is an important process mediating methane release to the water column and the atmosphere in this region. ¹⁸O-enrichment could be a result of MDAC precipitation with seawater in colder than present day conditions, or precipitation with ¹⁸O-enriched water transported from deep petroleum sources. The ¹³C depletion of bulk carbonate and sampled gas (-70‰) suggests a biogenic source, but significant mixing of thermogenic gas and depletion of the original isotope signature cannot be ruled out. Active seepage was recorded from one mound and together with extensive areas of reduced sediment, confirms that seepage is ongoing. The mounds appear to be composed of stacked pavements that are largely covered by sand and extensively eroded. The CFZ mounds are colonized by abundant Sabellaria polychaetes and possible Nemertesia hydroids, which benefit indirectly from available hard substrate. In contrast to deep sea MDAC settings where seep-related macrofauna are commonly reported, seep-specialist fauna appear to be lacking at the CFZ. In addition, unlike MDAC in deep waters where organic carbon input from photosynthesis is limited, lipid biomarkers and isotope signatures related to marine planktonic production (e.g. sterols, alkanols) were most abundant. Evidence for microbes involved in AOM was limited from samples taken; possibly due to this dilution effect from organic matter derived from the photic zone, and will require further investigation. 

An overview of chemosynthetic symbioses in bivalves from the North Atlantic and Mediterranean Sea

Deep-sea bivalves found at hydrothermal vents, cold seeps and organic falls are sustained by chemosynthetic bacteria that ensure part or all of their carbon nutrition. These symbioses are of prime importance for the functioning of the ecosystems. Similar symbioses occur in other bivalve species living in shallow and coastal reduced habitats worldwide. In recent years, several deep-sea species have been investigated from continental margins around Europe, West Africa, eastern Americas, the Gulf of Mexico, and from hydrothermal vents on the Mid-Atlantic Ridge. In parallel, numerous, more easily accessible shallow marine species have been studied. Herein we provide a summary of the current knowledge available on chemosymbiotic bivalves in the area ranging west-to-east from the Gulf of Mexico to the Sea of Marmara, and north-to-south from the Arctic to the Gulf of Guinea. Characteristics of symbioses in 53 species from the area are summarized for each of the five bivalve families documented to harbor chemosynthetic symbionts (Mytilidae, Vesicomyidae, Solemyidae, Thyasiridae and Lucinidae). Comparisons are made between the families, with special emphasis on ecology, life cycle, and connectivity. Chemosynthetic symbioses are a major adaptation to ecosystems and habitats exposed to reducing conditions. However, relatively little is known regarding their diversity and functioning, apart from a few “model species” on which effort has focused over the last 30 yr. In the context of increasing concern about biodiversity and ecosystems, and increasing anthropogenic pressure on oceans, we advocate a better assessment of the diversity of bivalve symbioses in order to evaluate the capacities of these remarkable ecological and evolutionary units to withstand environmental change.

Trends in deep-water shark fisheries in the Azores

Deep-sea resources have been increasingly exploited, and due to that, several ecosystems and species have been considerably affected. Deep-water sharks populations have been of the most disturbed by practices of unselected fisheries, bycatch and discard, mainly due to their low commercial value. Those practices make deep-water sharks very vulnerable to overfishing given their life-history traits, increasing their extinction risk. With the prohibition of the direct fishery, and implementation of quotas and TACs (Total Allowable Catches) regarding the deep-sea shark landings, the official landings have dramatically decreased after the 1990s. However, the IUU (Illegal, unreported and unregulated) catch has exponentially increased. With the analysis of catch per unit effort (CPUE), the depths, and the mean weight of the individuals over the years for each one of the nine most caught species in the Azores, we produced a descriptive analysis of the effect of fisheries in those species. The results show that some of these species have been suffering from a great fishing pressure, and their populations will be greatly affected in the near future if drastic measures are not taken when it comes to managing their long term sustainability.

TURTLE: Systems and technologies for deep ocean long term presence

This paper describes the TURTLE project that aim to develop sub-systems with the capability of deep-sea long-term presence. Our motivation is to produce new robotic ascend and descend energy efficient technologies to be incorporated in robotic vehicles used by civil and military stakeholders for underwater operations. TURTLE contribute to the sustainable presence and operations in the sea bottom. Long term presence on sea bottom, increased awareness and operation capabilities in underwater sea and in particular on benthic deeps can only be achieved through the use of advanced technologies, leading to automation of operation, reducing operational costs and increasing efficiency of human activity.

Studies on the Deep - Water Crab Charybdis (Goniohellenus ) Smithii Macleay From the Seas Around India

The present study deals with a general introduction which outlines the objective of the study providing an exhaustive review of works on crabs with particular reference to deep-sea forms. In the first section, Taxonomy and Geographical disribution of the crab are dealt with. The species is described in detail based on several male and female specimens obtained from the pelagic and bottom collections, and its identity in Indian waters is established. It is also distinguished from a closely allied species so far not reported from Indian waters. The second section comprises the biology of the species and it is dealt with under four subheading, namely Habit and Habitats, Reproduction, Food and feeding and Proximate composition. The different habitats occupied by juveniles, subadults and adults of the species have been described and discussed in the light of available information on differential distribution of other related species. The reproductive biology is described in various details touching on gross anatomy and histology of the reproductive systems, spermatogenesis, oogenesis, size at maturity, ovarian maturation process, fecundity, egg carriage and breeding. The food and feeding habits of the species have been studied with reference to the different life stages such as juveniles, subadults and adults during the different phases of life based on stomach content analysis. The percentage of meat recovery and protein, carbohydrate and lipid content of meat have been described in the section dealing with proximate composition. In section three the distribution and abundance of the crab for the entire Indian EEZ and some contiguous ares have been described and illustrated in detail separately for pelagic and benthic realms. The size frequency disrtibution, sex ratios, length weight relationship and relative abundance of breeding population in the experimental catches have been dealt with in detail and discussed.

Heterotrophic bacteria from the continental slope sediments of arabian sea

The marine environment is indubitably the largest contiguous habitat on Earth. Because of its vast volume and area, the influence of the world ocean on global climate is profound and plays an important role in human welfare and destiny. The marine environment encompasses several habitats, from the sea surface layer down through the bulk water column, which extends >10,000 meters depth, and further down to the habitats on and under the sea floor. Compared to surface habitats, which have relatively high kinetic energy, deep-ocean circulation is very sluggish. By comparison, life in the deep sea is characterized by a relatively constant physical and chemical environment. Deep water occupying the world ocean basin is a potential natural resource based on its properties such as low temperature, high pressure and relatively unexplored properties. So, a judicious assessment of the marine resources and its management are essential to ensure sustainable development of the country’s ocean resources. Marine sediments are complex environments that are affected by both physiological and biological factors, water movements and burrowing animals. They encompass a large extent of aggregates falling from the surface waters. In aquatic ecosystems, the flux of organic matter to the bottom sediments depend on primary productivity at the ocean surface and water depth. Over 50% of the earth’s surface is covered by deep-sea sediments that are primarily formed through the continual deposition of particles from the productive pelagic waters (Vetriani et al., 1999). These aggregates are regarded as ‘hot spots’ of microbial activity in the ocean (Simon et al., 2002). This represents a good nutritional substrate for heterotrophic bacteria and favours bacterial growth

Evaluating the efficacy of planktonic foraminifer calcite and 18O data for sea surface temperature reconstruction for the Late Miocene

This study examines the efficacy of published δ18O data from the calcite of Late Miocene surface dwelling planktonic foraminifer shells, for sea surface temperature estimates for the pre-Quaternary. The data are from 33 Late Miocene (Messinian) marine sites from a modern latitudinal gradient of 64°N to 48°S. They give estimates of SSTs in the tropics/subtropics (to 30°N and S) that are mostly cooler than present. Possible causes of this temperature discrepancy are ecological factors (e.g. calcification of shells at levels below the ocean mixed layer), taphonomic effects (e.g. diagenesis or dissolution), inaccurate estimation of Late Miocene seawater oxygen isotope composition, or a real Late Miocene cool climate. The scale of apparent cooling in the tropics suggests that the SST signal of the foraminifer calcite has been reset, at least in part, by early diagenetic calcite with higher δ18O, formed in the foraminifer shells in cool sea bottom pore waters, probably coupled with the effects of calcite formed below the mixed layer during the life of the foraminifera. This hypothesis is supported by the markedly cooler SST estimates from low latitudes—in some cases more than 9 °C cooler than present—where the gradients of temperature and the δ18O composition of seawater between sea surface and sea bottom are most marked, and where ocean surface stratification is high. At higher latitudes, particularly N and S of 30°, the temperature signal is still cooler, though maximum temperature estimates overlap with modern SSTs N and S of 40°. Comparison of SST estimates for the Late Miocene from alkenone unsaturation analysis from the eastern tropical Atlantic at Ocean Drilling Program (ODP) Site 958—which suggest a warmer sea surface by 2–4 °C, with estimates from oxygen isotopes at Deep Sea Drilling Project (DSDP) Site 366 and ODP Site 959, indicating cooler than present SSTs, also suggest a significant impact on the δ18O signal. Nevertheless, much of the original SST variation is clearly preserved in the primary calcite formed in the mixed layer, and records secular and temporal oceanographic changes at the sea surface, such as movement of the Antarctic Polar Front in the Southern Ocean. Cooler SSTs in the tropics and sub-tropics are also consistent with the Late Miocene latitude reduction in the coral reef belt and with interrupted reef growth on the Queensland Plateau of eastern Australia, though it is not possible to quantify absolute SSTs with the existing oxygen isotope data. Reconstruction of an accurate global SST dataset for Neogene time-slices from the existing published DSDP/ODP isotope data, for use in general circulation models, may require a detailed re-assessment of taphonomy at many sites.

Evaluating the efficacy of planktonic foraminifer calcite and 18O data for sea surface temperature reconstruction for the Late Miocene

This study examines the efficacy of published δ18O data from the calcite of Late Miocene surface dwelling planktonic foraminifer shells, for sea surface temperature estimates for the pre-Quaternary. The data are from 33 Late Miocene (Messinian) marine sites from a modern latitudinal gradient of 64°N to 48°S. They give estimates of SSTs in the tropics/subtropics (to 30°N and S) that are mostly cooler than present. Possible causes of this temperature discrepancy are ecological factors (e.g. calcification of shells at levels below the ocean mixed layer), taphonomic effects (e.g. diagenesis or dissolution), inaccurate estimation of Late Miocene seawater oxygen isotope composition, or a real Late Miocene cool climate. The scale of apparent cooling in the tropics suggests that the SST signal of the foraminifer calcite has been reset, at least in part, by early diagenetic calcite with higher δ18O, formed in the foraminifer shells in cool sea bottom pore waters, probably coupled with the effects of calcite formed below the mixed layer during the life of the foraminifera. This hypothesis is supported by the markedly cooler SST estimates from low latitudes—in some cases more than 9 °C cooler than present—where the gradients of temperature and the δ18O composition of seawater between sea surface and sea bottom are most marked, and where ocean surface stratification is high. At higher latitudes, particularly N and S of 30°, the temperature signal is still cooler, though maximum temperature estimates overlap with modern SSTs N and S of 40°. Comparison of SST estimates for the Late Miocene from alkenone unsaturation analysis from the eastern tropical Atlantic at Ocean Drilling Program (ODP) Site 958—which suggest a warmer sea surface by 2–4 °C, with estimates from oxygen isotopes at Deep Sea Drilling Project (DSDP) Site 366 and ODP Site 959, indicating cooler than present SSTs, also suggest a significant impact on the δ18O signal. Nevertheless, much of the original SST variation is clearly preserved in the primary calcite formed in the mixed layer, and records secular and temporal oceanographic changes at the sea surface, such as movement of the Antarctic Polar Front in the Southern Ocean. Cooler SSTs in the tropics and sub-tropics are also consistent with the Late Miocene latitude reduction in the coral reef belt and with interrupted reef growth on the Queensland Plateau of eastern Australia, though it is not possible to quantify absolute SSTs with the existing oxygen isotope data. Reconstruction of an accurate global SST dataset for Neogene time-slices from the existing published DSDP/ODP isotope data, for use in general circulation models, may require a detailed re-assessment of taphonomy at many sites.

Macrofaunal succession in sediments around kelp and wood falls in the deep NE Pacific and community overlap with other reducing habitats

Sunken parcels of macroalgae and wood provide important oases of organic enrichment at the deep-sea floor, yet sediment community structure and succession around these habitat islands are poorly evaluated. We experimentally implanted 100-kg kelp falls and 200 kg wood falls at 1670 m depth in the Santa Cruz Basin to investigate (1) macrofaunal succession and (2) species overlap with nearby whale-fall and cold-seep communities over time scales of 0.25-5.5 yr. The abundance of infaunal macrobenthos was highly elevated after 0.25 and 0.5 yr near kelp parcels with decreased macrofaunal diversity and evenness within 0.5 m of the falls. Apparently opportunistic species (e.g., two new species of cumaceans) and sulfide tolerant microbial grazers (dorvilleid polychaetes) abounded after 0.25-0.5 yr. At wood falls, opportunistic cumaceans become abundant after 0.5 yr, but sulfide tolerant species only became abundant after 1.8-5.5 yr, in accordance with the much slower buildup of porewater sulfides at wood parcels compared with kelp falls. Species diversity decreased significantly over time in sediments adjacent to the wood parcels, most likely due to stress resulting from intense organic loading of nearby sediments (up to 20-30% organic carbon). Dorvilleid and ampharetid polychaetes were among the top-ranked fauna at wood parcels after 3.0-5.5 yr. Sediments around kelp and wood parcels provided low-intensity reducing conditions that sustain a limited chemoautrotrophically-based fauna. As a result, macrobenthic species overlap among kelp, wood, and other chemosynthetic habitats in the deep NE Pacific are primarily restricted to apparently sulfide tolerant species such as dorvilleid polychaetes, opportunistic cumaceans, and juvenile stages of chemosymbiont containing vesicomyid bivalves. We conclude that organically enriched sediments around wood falls may provide important habitat islands for the persistence and evolution of species dependent on organic- and sulfide-rich conditions at the deep-sea floor and contribute to beta and gamma diversity in deep-sea ecosystems. (C) 2010 Elsevier Ltd. All rights reserved.

Spatio-temporal variation of macrofaunal assemblages in the deep Blanes submarine canyon

The spatio-temporal variations in diversity and abundance of deep-sea macrofaunal assemblages (excluding meiofaunal taxa, as Nematoda, Copepoda and Ostracoda) from the Blanes Canyon (BC) and adjacent open slope are described. The Catalan Sea basin is characterized by the presence of numerous submarine canyons, which are globally acknowledged as biodiversity hot-spots, due to their disturbance regime and incremented conveying of organic matter. This area is subjected to local deep-sea fisheries activities, and to recurrent cold water cascading events from the shelf. The upper canyon (~900 m), middle slope (~1200 m) and lower slope (~1500 m) habitats were investigated during three different months (October 2008, May 2009 and September 2009). A total of 624 specimens belonging to 16 different taxa were found into 67 analyzed samples, which had been collected from the two study areas. Of these, Polychaeta, Mollusca and Crustacea were always the most abundant groups. As expected, the patterns of species diversity and evenness were different in time and space. Both in BC and open slope, taxa diversity and abundance are higher in the shallowest depth and lowest at -1500 m depth. This is probably due to different trophic regimes at these depths. The abundance of filter-feeders is higher inside BC than in the adjacent open slope, which is also related with an increment of predator polychaetes. Surface deposit-feeders are more abundant in the open slope than in BC, along with a decrement of filter-feeders and their predators. Probably these differences are due to higher quantities of suspended organic matter reaching the canyon. The multivariate analyses conducted on major taxa point out major differences effective taxa richness between depths and stations. In September 2009 the analyzed communities double their abundances, with a corresponding increase in richness of taxa. This could be related to a mobilizing event, like the release of accumulated food-supply in a nepheloid layer associated to the arrival of autumn. The highest abundance in BC is detected in the shallowest depth and in late summer (September), probably due to higher food availability caused by stronger flood events coming from Tordera River. The effects of such events seemed to involve adjacent open slope too. The nMDS conducted on major taxa abundance shows a slight temporal difference between the three campaigns samples, with a clear clustering between samples of Sept 09. All depth and all months were dominated by Polychaeta, which have been identified to family level and submitted to further analysis. Family richness have clearly minimum at the -1200 m depth of BC, highlighting the presence of a general impact affecting the populations in the middle slope. Three different matrices have been created, each with a different taxonomic level (All Taxa “AT”, Phylum Level “PL” and Polychaeta Families “PF”). Multivariate analysis (MDS, SIMPER) conducted on PL matrix showed a clear spatial differences between stations (BC and open slope) and depths. MDSs conducted on other two matrices (AT and PF) showed similar patterns, but different from PL analysis. A 2 nd stage analysis have been conducted to understand differences between different taxonomic levels, and PL level has been chosen as the most representative of variation. The faunal differences observed were explained by depth, station and season. All work has been accomplished in the Centre d’estudis avançats de Blanes (CEAB-CSIC), within the framework of Spanish PROMETEO project "Estudio Integrado de Cañones y Taludes PROfundos del MEdiTErráneo Occidental: un hábitat esencial", Ref. CTM2007-66316-C02- 01/MAR.

Projected pH reductions by 2100 might put deep North Atlantic biodiversity at risk

This study aims to evaluate the potential for impacts of ocean acidification on North Atlantic deep-sea ecosystems in response to IPCC AR5 Representative Concentration Pathways (RCPs). Deep-sea biota is likely highly vulnerable to changes in seawater chemistry and sensitive to moderate excursions in pH. Here we show, from seven fully coupled Earth system models, that for three out of four RCPs over 17% of the seafloor area below 500 m depth in the North Atlantic sector will experience pH reductions exceeding −0.2 units by 2100. Increased stratification in response to climate change partially alleviates the impact of ocean acidification on deep benthic environments. We report on major pH reductions over the deep North Atlantic seafloor (depth >500 m) and at important deep-sea features, such as seamounts and canyons. By 2100, and under the high CO2 scenario RCP8.5, pH reductions exceeding −0.2 (−0.3) units are projected in close to 23% (~15%) of North Atlantic deep-sea canyons and ~8% (3%) of seamounts – including seamounts proposed as sites of marine protected areas. The spatial pattern of impacts reflects the depth of the pH perturbation and does not scale linearly with atmospheric CO2 concentration. Impacts may cause negative changes of the same magnitude or exceeding the current target of 10% of preservation of marine biomes set by the convention on biological diversity, implying that ocean acidification may offset benefits from conservation/management strategies relying on the regulation of resource exploitation.