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Taxonomic and Microbial Profiling of Diseased and Healthy Marine Sponges from a Commercial Sponge Farm on Zanzibar
No full textAquacultural gateways of antimicrobials in the marine environment: A case study of the cold-water-coral Desmophyllum dianthus in Chilean Comau-fjord
No full textRegional ecosystem-based fisheries management: key concepts and (some) recent developments
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Peak glacial-to-Heinrich-1 changes in Denmark Strait Overflow and seawater stratification in the Nordic Seas, a switchboard of changes in Atlantic Meridional Overturning Circulation and the 'Nordic Heat Pump'
No full textHighlights:
• Interstadial Nordic Sea's overflow waters and AMOC were fed by Arctic deep waters and enhanced, leading to local mud erosion.
• Sediments off N Iceland show a joint onset of deglacial meltwater input and a 3-degree warming of DK Strait Overflow 18.4 ka.
• Change of deglacial overflow was paired with reduced heat advection to N Europe and Greenland 18,4-15 ka, Heinrich Stadial 1.
• After 16.3 ka, a major Barents ice meltwater outbreak caused further changes in flow geometry and a cooling named HS-1a.
• Marine calibrated age values based on atm. 14C-plateau-tuning match incremental ages found in deglacial Greenland ice records.
Abstract
Today, the sub-surface Denmark Strait Overflow (DSO) and the Iceland-Scotland Overflow form the starting points of the Atlantic Meridional Overturning Circulation and compensate for the poleward flowing Norwegian and Irminger branches of the North Atlantic surface current that drive the 'Nordic Heat Pump'. During peak glacial and early deglacial times, ice sheets on Iceland and Greenland, and ice-induced isostatic and eustatic sea-level changes reduced the Denmark Strait aperture and DSO. Yet, extremely high benthic stable carbon and oxygen isotope values together with very high ventilation ages of bottom waters suggest a north-south density gradient of intermediate-waters and persistent flow of partially Arctic-sourced waters through both Denmark Strait and Faeroe Channel, analogous to today. The arrival of deglacial meltwaters off northern Iceland induced the onset of Heinrich-Stadial 1 near 18.400 yr BP, as derived from 14C-plateau tuning. They caused a tipping point in DSO circulation shown by 3 °C warming, reduced ventilation and ventilation ages of bottom water, moreover, by increased radiogenic Nd isotope signatures at luff-side Site PS2644. These records suggest a sudden subsurface incursion of Atlantic intermediate waters across basaltic sediments from S.E. of Iceland. Deep-water convection off Norway then was replaced by weak brine water formation, coeval with a breakdown of the 'Nordic Heat Pump' evidenced by a temperature drop on Greenland. After 16.2 cal ka, a major meltwater outbreak from the Barents ice shelf led to modified Heinrich-1-style circulation until ∼15.1 cal. ka. Conversely, the DSO intensified during interstadial and Holocene times, causing sediment hiatuses at Site PS2644
Artificial light at night can influence the composition, diversity and biomass of early-successional hard-bottom communities
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Observed regimes of submesoscale dynamics in the Southern Ocean seasonal ice zone
No full textSubmesoscale flows, occurring at scales of about 1–10 km, are crucial to the vertical transport of heat and other tracers in the upper ocean. These flows are energized by instabilities that extract potential energy from lateral buoyancy gradients, which are ubiquitous in the seasonal sea ice zone. Process studies have shown that submesoscale flows influence sea ice mechanics and thermodynamics. However, it is necessary to quantify the spatiotemporal distribution of submesoscale fluxes in order to upscale their impact. Here, we utilize hydrographic data from seal-borne sensors to demonstrate that the Southern Ocean seasonal ice zone can be separated into three regimes of submesoscale flux variability, which are associated with distinct dominant drivers. Furthermore, the magnitude and sign of the mean heat fluxes in these regimes differs, which dictates their influence on the upper-ocean heat budget, mixed-layer depth, and sea ice properties
The ~25ka Lajes-Angra ignimbrite-forming eruptions from a scientific and social perspective
No full textArtificial Structures as Shark Egg‐Laying Substrate in a Previously Fished Mediterranean Demersal No‐Take MPA
No full textThe location of shark egg nursery areas in the Mediterranean Sea is not well known. Moreover, decades of trawling have depleted flat muddy bottoms of both organic (sessile colonial organisms) and inorganic (rocks) three-dimensional structures in the western Mediterranean Sea. Here, we present observations of 263 egg cases of small-spotted catshark (Scyliorhinus canicula) that were found attached to artificial mooring structures located within a demersal no-take MPA at 300- to 400-m depth. The area is located within a previously identified suitable habitat for small-spotted catshark egg nurseries, and where conservation measures, such as a no-take MPAs, have been implemented to recover the heavily-impacted ecosystem. However, the slow growth of habitat-forming sessile organisms combined with previous extraction of rocks and other objects from the seabed is hampering the recovery of these areas and the reproduction of oviparous sharks such as the small-spotted catshark. Our findings reveal that three-dimensional artificial structures with ropes and other attachments placed within suitable egg nursery habitat are effectively used by small-spotted catsharks to complete their reproductive cycle. Passive conservation tools such as no-take MPA may be coupled with active restoration activities such as the deployment of artificial structures in order to improve the conservation and recovery of oviparous elasmobranchs and other marine fauna