Simple harpacticoid composition observed at deep hydrothermal vent sites on sea knoll calderas in the North-west Pacific

Dirivultid copepods (Siphonostomatoida), one of the most successful meiobenthic organisms found at deep-sea hydrothermal vents, have been the focus of most previous ecological studies among meiofauna in these habitats. The ecology of Harpacticoida, a major benthic copepod group in typical deep-sea floor, however, is not well understood in terms of variations in community structure and controlling factors at venting sites. The spatial heterogeneities in benthic harpacticoid composition and their association with environmental parameters were investigated at hydrothermal vent chimney structures in the calderas of three neighbouring sea knolls (Bayonnaise Knoll, Myojin Knoll and Myojin-sho Caldera) in the western North Pacific. While a previous study had reported the distribution of dirivultids was strongly associated with spatial differences in stable carbon isotopic signatures (δ13C) of organic matter in the detritus on active chimneys in the field, multivariate analyses detected no significant corelation between the parameter and harpacticoid composition in this study. Instead, high associations of the harpacticoid composition with differences in water depth and total organic carbon (TOC) concentration were detected. Ectinosomatidae dominated at vent sites with lower TOC values in the shallowest Bayonnaise Knoll, while they were less prevalent at deeper vent fields in the other knolls, where Miraciidae was the most abundant family. This study indicated the availability of vent chemoautotrophic carbon is not a primary factor controlling the composition of harpacticoids even in the habitats on the hydrothermal vents, but instead by the food amount, regardless of its resources (including marine snow from the sea surface), in the study area.

Seasonal Cruise Q3

The Nansen Legacy Q3 cruise, 5-27 August 2019, initiated the seasonal investigations of the Nansen Legacy transect. The transect represent an environmental gradient going through the northern Barents Sea, and included 7 process stations (P1-P7) lasting 6-53 hrs. CTD stations were taken to increase the hydrographic resolution on the transect. The program included measurements and sampling from the atmosphere, sea ice, ocean and sea floor. Data collected ranged from physical observations, chemical, biological and geological data collection, and the aim was to link observations and measurements to improve our understanding of the systems involving both climate, human impacts and the ecosystems. Deployment of moorings and gliders extended the observational capacity in time and space, outside the cruise period.

Reviewing the elements of marine ice cliff instability

Antarctica’s ice sheets are the largest potential sea-level rise contributors, but projections of future sea-level rise yield wide ranges of estimates under different emission scenarios. An important factor in the variability of estimates is marine ice cliff instability (MICI). Inclusion of MICI yields the highest potential sea-level rise cases but also the largest uncertainty due to poor understanding of the factors that control it and the mechanisms of how it happens. Although evidence for MICI has been implied by paleo-ice sheet studies and observations of keel plough mark on sea-floor, recent statistical and modelling studies have suggested a lower magnitude of MICI effect on sea-level rise due to thinning of ice sheets and buttressing forces exerted on potentially failing cliffs. This paper reviews the factors that control MICI with the goal of identifying priorities for modern ice sheet studies to better bound the estimates.

Exploitation of Beach Sand Minerals in the Offshore Areas – Legal perspective in the light of MMDR Act, 1957 and OAMDR Act, 2002

Beach Sand Minerals (BSM) form by weathering and erosion of the rocks in the hinterland which are liberated, disintegrate by various processes and, are transportation by the streams to the sites of deposition (coastal plains). These minerals get concentrated along the coastal areas due to constant winnowing by wave action. It is well documented that sea level changes have occurred along the coastal areas at different points of time whose signatures on land can be seen in the form of palaeo-strandline occurring up to 15-20 km from the present day coast. On a similar analogy and in view of bathymetric profile of the sea floor, BSM deposits are expected in the offshore areas as well, in continuity to onshore deposits, which possibly are the submerged onshore deposits of the past. Mineral Concessions in respect of onshore BSM deposits are governed with the Mines and Minerals Development and Regulation (MMDR) Act, 1957 and those in the offshore are governed as per the Offshore Areas Mineral Development and Regulation (OAMDR) Act, 2002 and the rules thereunder respectively. This paper deals with various provisions of these Acts and recent policies of the Government to harmonize mineral concession in offshore areas in line with the onshore BSM deposits.

Sharks, rays and chimaeras of the Seine and Unicorn seamounts (NE Atlantic Ocean)

Background Seamounts are underwater mountains which typically rise rather steeply at least several hundred meters above the deep-sea floor. These geological features interrupt water flow and hence may induce changes in the circulation of different water masses, in turn causing different physical and biological effects. For this reason, seamounts are biodiversity hotspots, housing a wide number of species, as is with the case of the Seine and Unicorn seamounts, which are a part of the Madeira-Tore seamount chain located between Portugal mainland, southwestern Europe and Madeira archipelago (NE Atlantic). Methods Fisheries independent surveys allowed the collection of Chondrichthyes specimens from the Seine and Unicorn seamounts. Individuals were caught over the course of two research cruises, first in 2004 and later in 2017, with species distribution ranging from the summit down to 2500 m of depth. Results Fifteen species belonging to 7 different taxonomical families were collected in the two surveyed areas. Two species were recorded for the first time and added to the checklist of the Seine seamount (Centrophorus granulosus and Somniosus rostratus), and three species for the Unicorn seamount (C. granulosus, Centroscymnus coelolepis and Centroselachus crepidater). Distribution and frequency of occurrence for the collected species were evaluated in relation to depth. Conclusions This work is a valuable contribution to the knowledge of seamount-associated fish fauna. Moreover, the checklist of sharks, rays and chimaeras was updated for the Seine and Unicorn seamounts, summing up 20 species.

Sedimentology of the grounding zone of the Kamb Ice Stream, Siple Coast, West Antarctica

<div>The grounding line of the Siple Coast incorporates six major ice streams, which together drain around a third of the West Antarctic Ice Sheet. Previously, the ~2000 km-long feature had only been sampled and directly observed at Whillans Ice Stream. This thesis examines glaciomarine sediment and processes operating at the presently stagnant Kamb Ice Stream (KIS) grounding zone ~3.3 km seaward of the modern grounding line (Lat. -82.78, Long. -155.16), where the ice is 590 m thick and overlies a 30 m thick water column. KIS-GZ is the planned site for a deep drilling project in 2023. The sea floor was accessed using a hot water drill in the 2019/20 Antarctic field season. A remotely operated submersible (‘Icefin’) was deployed under the ice shelf, which provided 800 m of sea floor video toward the grounding line. A small number of short (~0.6 m) gravity cores were collected from the seafloor, one of which was examined in this study. <br></div><div><br></div><div>The Icefin video imagery was processed using Structure-from-Motion (SfM) software, enabling the identification of two previously unrecognised sea floor sedimentary facies. One is defined by ubiquitous cm-scale ripples in fine-medium sand, where the ripples are aligned with the prevailing tidal currents flowing parallel to the grounding line. Observed current speeds are too low for the ripples to be generated under the modern oceanographic regime. The second facies is defined by abundant dropstones in mediumcoarse sand. A transition zone separates the two facies. Previously unidentified decimetre-scale bedforms are present in the transition zone and near the borehole.</div><div><br></div><div>The lithological, geochemical, and microfossil properties of the gravity core were analysed. The core sediment is sandy diamicton with weak stratification defined by decimetre-scale changes in clast abundance. Mineral counts, zircon ages, Nd/Sr isotopes, and an immature composition indicate this sediment is sourced within the Kamb catchment. The core also contains reworked late Oligocene-late Miocene diatoms. Quaternary diatoms are absent. Ramped pyrolysis radiocarbon dating was attempted on 19 carbon fractions obtained from samples at four depths. Two pyrolysis fractions yielded ages of 31.5-33.2 ka, while the rest did not contain measurable radiocarbon. This likely reflects the reworking of radiocarbon-dead material into the sediment and can only be considered a maximum age for deposition.</div><div><br></div><div>Together, the sediment and video data suggest deposition of the sea floor sediment at the core site occurred subsequent to the stagnation of KIS ~160 years ago. I assume that sediment concentrations are relatively uniform along the length of the ice stream and calculate that up to ~2.7 m of diamicton was rapidly deposited at the core site as the grounding line retreated and englacial sediment melted out and settled through the water column. Accumulation in recent decades has been comparatively low. During the period of reduced sedimentation, the sea floor diamicton has been reworked to varying degrees to form ripples and winnowed lag deposits, resulting in a textural patchwork at km scale.</div>

Sedimentology of the grounding zone of the Kamb Ice Stream, Siple Coast, West Antarctica

<div>The grounding line of the Siple Coast incorporates six major ice streams, which together drain around a third of the West Antarctic Ice Sheet. Previously, the ~2000 km-long feature had only been sampled and directly observed at Whillans Ice Stream. This thesis examines glaciomarine sediment and processes operating at the presently stagnant Kamb Ice Stream (KIS) grounding zone ~3.3 km seaward of the modern grounding line (Lat. -82.78, Long. -155.16), where the ice is 590 m thick and overlies a 30 m thick water column. KIS-GZ is the planned site for a deep drilling project in 2023. The sea floor was accessed using a hot water drill in the 2019/20 Antarctic field season. A remotely operated submersible (‘Icefin’) was deployed under the ice shelf, which provided 800 m of sea floor video toward the grounding line. A small number of short (~0.6 m) gravity cores were collected from the seafloor, one of which was examined in this study. <br></div><div><br></div><div>The Icefin video imagery was processed using Structure-from-Motion (SfM) software, enabling the identification of two previously unrecognised sea floor sedimentary facies. One is defined by ubiquitous cm-scale ripples in fine-medium sand, where the ripples are aligned with the prevailing tidal currents flowing parallel to the grounding line. Observed current speeds are too low for the ripples to be generated under the modern oceanographic regime. The second facies is defined by abundant dropstones in mediumcoarse sand. A transition zone separates the two facies. Previously unidentified decimetre-scale bedforms are present in the transition zone and near the borehole.</div><div><br></div><div>The lithological, geochemical, and microfossil properties of the gravity core were analysed. The core sediment is sandy diamicton with weak stratification defined by decimetre-scale changes in clast abundance. Mineral counts, zircon ages, Nd/Sr isotopes, and an immature composition indicate this sediment is sourced within the Kamb catchment. The core also contains reworked late Oligocene-late Miocene diatoms. Quaternary diatoms are absent. Ramped pyrolysis radiocarbon dating was attempted on 19 carbon fractions obtained from samples at four depths. Two pyrolysis fractions yielded ages of 31.5-33.2 ka, while the rest did not contain measurable radiocarbon. This likely reflects the reworking of radiocarbon-dead material into the sediment and can only be considered a maximum age for deposition.</div><div><br></div><div>Together, the sediment and video data suggest deposition of the sea floor sediment at the core site occurred subsequent to the stagnation of KIS ~160 years ago. I assume that sediment concentrations are relatively uniform along the length of the ice stream and calculate that up to ~2.7 m of diamicton was rapidly deposited at the core site as the grounding line retreated and englacial sediment melted out and settled through the water column. Accumulation in recent decades has been comparatively low. During the period of reduced sedimentation, the sea floor diamicton has been reworked to varying degrees to form ripples and winnowed lag deposits, resulting in a textural patchwork at km scale.</div>

Geology of seas and oceans: Proceedings of XXIV International Conference on Marine Geology. Vol. IV.

The reports of marine geologists, geophysics, geochemists and other specialists of marine science at XXIV International Conference on Marine Geology in Moscow are published in four volumes. Volume IV includes reports devoted to the problems of research of polar regions, and also of sea floor geophysics and geomorphology, lithosphere plate tectonics.

Ocean and Terrestrial Response to a Pleistocene Warm Interglacial (MIS11) as Revealed by Pollen and Dinoflagellates from Marine Sediment Cores, South Island, New Zealand

<p>The response of the surface ocean and terrestrial climate in the New Zealand region to interglacial Marine Isotope Stage (MIS) 11 (423-380ka) is documented, using assemblages of fossilised marine algae (dinoflagellate cysts, or dinocysts) and spores/pollen from terrestrial plants, analysed from marine sediment cores. This work is underpinned by studies on the modern distribution of dinocysts, factors that influence their accumulation in marine sediment, and the use of dinocyst assemblages to quantify past sea surface temperature (SST). In the first of the modern-process studies, a dataset of modern sea-floor dinocyst assemblages from the Southern Hemisphere is collated, including new observations from the SW Pacific. Variations in the assemblages are related to environmental gradients. Cluster analysis reveals distinct biogeographic assemblage zones, individual taxa indicative of specific water masses are identified, while ordination of the databases indicates that the assemblages vary most with changes in SST. A second modern process study reports on the dinocyst assemblages from two time-incremental sediment traps (3 years of data) moored north and south of the Subtropical Front in the ocean east of New Zealand. This study provides observations of seasonal and inter-annual variability of dinocyst flux to the deep sea, which are used to identify possible biases in the sea-floor dinocyst assemblages. Observations from these first two studies are used in a systematic analysis of the strengths and weakness of using dinocyst assemblages to quantify SST in the SW Pacific. The best transfer function performance achieved was a root mean squared error of 1.47˚C, for an artificial neural network model, and the benefits in considering a range of model results are also established. Fossil records that document the oceanographic and terrestrial response to MIS11 are developed from two areas around New Zealand; (i) dinocysts assemblages are collected from the east Tasman Sea, from giant piston cores MD06-2987, -2988, and 2989, and (ii) dinocysts and pollen assemblages are analysed from Deep Sea Drilling Project (DSDP) Site 594, from the east of New Zealand. Dinocyst assemblages confirm that SST in the east Tasman Sea was ~2-3˚C warmer than the present during late MIS11 (415-400ka), while SSTs were slightly below modern levels during an early phase (428-415ka). Two assemblage – based productivity indices suggest that the elevated SSTs during MIS11 were accompanied by lower rates of primary productivity in the east Tasman Sea study area than the present. As in the east Tasman Sea, two distinct phases of MIS11 are recognised in both the dinocyst and pollen assemblages at DSDP 594. The dinocyst assemblages of late MIS11 are similar to, but qualitatively represent warmer waters than the Holocene. The succession of pollen assemblages during MIS12-11 is very similar to that observed during the previous two interglacials at this site (MIS1 and MIS5), with two notable variations: (i) the deglacial vegetation succession during MIS11 was prolonged, and (ii) the pollen assemblage representing the warmest forest type was also present for longer (ca. 15ky) than later interglacials. Changes in the pollen record during MIS11 at DSDP 594 correlate more closely to SST variations in the east Tasman Sea than to ocean variations at DSDP 594, suggesting that the eastern ocean had only limited influence on conditions on the adjacent landmass during MIS11.</p>

Ocean and Terrestrial Response to a Pleistocene Warm Interglacial (MIS11) as Revealed by Pollen and Dinoflagellates from Marine Sediment Cores, South Island, New Zealand

<p>The response of the surface ocean and terrestrial climate in the New Zealand region to interglacial Marine Isotope Stage (MIS) 11 (423-380ka) is documented, using assemblages of fossilised marine algae (dinoflagellate cysts, or dinocysts) and spores/pollen from terrestrial plants, analysed from marine sediment cores. This work is underpinned by studies on the modern distribution of dinocysts, factors that influence their accumulation in marine sediment, and the use of dinocyst assemblages to quantify past sea surface temperature (SST). In the first of the modern-process studies, a dataset of modern sea-floor dinocyst assemblages from the Southern Hemisphere is collated, including new observations from the SW Pacific. Variations in the assemblages are related to environmental gradients. Cluster analysis reveals distinct biogeographic assemblage zones, individual taxa indicative of specific water masses are identified, while ordination of the databases indicates that the assemblages vary most with changes in SST. A second modern process study reports on the dinocyst assemblages from two time-incremental sediment traps (3 years of data) moored north and south of the Subtropical Front in the ocean east of New Zealand. This study provides observations of seasonal and inter-annual variability of dinocyst flux to the deep sea, which are used to identify possible biases in the sea-floor dinocyst assemblages. Observations from these first two studies are used in a systematic analysis of the strengths and weakness of using dinocyst assemblages to quantify SST in the SW Pacific. The best transfer function performance achieved was a root mean squared error of 1.47˚C, for an artificial neural network model, and the benefits in considering a range of model results are also established. Fossil records that document the oceanographic and terrestrial response to MIS11 are developed from two areas around New Zealand; (i) dinocysts assemblages are collected from the east Tasman Sea, from giant piston cores MD06-2987, -2988, and 2989, and (ii) dinocysts and pollen assemblages are analysed from Deep Sea Drilling Project (DSDP) Site 594, from the east of New Zealand. Dinocyst assemblages confirm that SST in the east Tasman Sea was ~2-3˚C warmer than the present during late MIS11 (415-400ka), while SSTs were slightly below modern levels during an early phase (428-415ka). Two assemblage – based productivity indices suggest that the elevated SSTs during MIS11 were accompanied by lower rates of primary productivity in the east Tasman Sea study area than the present. As in the east Tasman Sea, two distinct phases of MIS11 are recognised in both the dinocyst and pollen assemblages at DSDP 594. The dinocyst assemblages of late MIS11 are similar to, but qualitatively represent warmer waters than the Holocene. The succession of pollen assemblages during MIS12-11 is very similar to that observed during the previous two interglacials at this site (MIS1 and MIS5), with two notable variations: (i) the deglacial vegetation succession during MIS11 was prolonged, and (ii) the pollen assemblage representing the warmest forest type was also present for longer (ca. 15ky) than later interglacials. Changes in the pollen record during MIS11 at DSDP 594 correlate more closely to SST variations in the east Tasman Sea than to ocean variations at DSDP 594, suggesting that the eastern ocean had only limited influence on conditions on the adjacent landmass during MIS11.</p>