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Sea-dumped munitions in the Baltic Sea support high epifauna abundance and diversity
No full textThe German waters contain 1.6 million tons of munitions, mostly dumped after the World Wars. The structure and composition of epifauna were investigated on the dumped munition in the Lübeck Bay (Baltic Sea) within the area with regular hypoxic conditions using a remotely operated vehicle (ROV). Objects were identified as warheads from the Fieseler flying bomb (Fi103, known as V1). Eight species of epifauna were found, with a mean density of 43,184 ind. m −2 , mostly concentrated on the metal parts. Surrounding sediment had a significantly lower abundance of only 8213 ind. m −2 . Chemical analysis of water sampled directly near several warheads showed high concentrations of explosive compounds, with, e.g., trinitrotoluene (TNT) levels of 2.73 mg/l. These concentrations approach toxicity thresholds for aquatic organisms. However, the epifauna develops on breached munitions in numbers comparable to natural hard substrata. In the future, munitions should be replaced with safe, hard substrates
Synthesis report on public perceptions from WP 3
No full textThis deliverable synthesizes the results from WP 3 on public perceptions of marine Carbon Dioxide Removal (CDR). The main purpose is to inform the overall synthesis report of OceanNets. It also helps inform the other work packages and stakeholders about our results in a timely and brief manner about the ways members of the public view marine CDR specificall
A hydrous mantle source for the Agulhas Plateau in the Southwest Indian Ocean: Insights from IODP Expedition 392
No full textPetrogenesis of mafic lavas and intrusions from the Agulhas Plateau in the SW Indian Ocean: Results from IODP Expedition 392
No full textNitrogen dynamics and nitrate stable isotopes indicate nitrogen loss in the Bay of Bengal
No full textOxygen-minimum zones (OMZs) play an important role in the global oceanic nitrogen cycle because they account for 20 % to 40 % of the global loss of bioavailable nitrogen despite covering only about 1 % of the global ocean volume. The intermediate waters of the Bay of Bengal (BoB) host one of the most pronounced OMZs with near-anoxic conditions. However, it has not yet been recognized as a site with significant nitrate reduction. In this study, we examined the nitrogen-cycling processes in the East Equatorial Indian Ocean (EEIO) and the BoB by measuring water column properties, including temperature, salinity, oxygen, and nutrient concentrations, as well as nitrate isotope signatures, collected during the SO305 BIOCAT-IIOE2 cruise in April and May 2024. Potential temperature and salinity profiles showed distinct water masses and limited mixing between the BoB and the EEIO at 5 degrees N.Nitrate stable isotope depth profiles varied significantly, driven by water mass distribution below 300 m and in situ fractionation above 300 m. Phytoplankton uptake acts as a nitrate sink in the surface waters, showing a significant isotopic enrichment and nitrogen deficit. In subsurface waters, nitrification was observed, primarily through regenerative production using previously assimilated biomass rather than newly fixed nitrogen from N2 fixation. Within the OMZ of the BoB, we identified a persistent nitrogen deficit and slightly enriched nitrate isotopes between 100 and 300 m, indicating nitrogen loss, which we attributed to anammox as the dominant nitrogen loss pathway in the BoB
The chromosomal genome sequence of the sponge, Oscarella lobularis (Schmidt, 1862) (Porifera, Homoscleromorpha) and its associated microbial metagenome sequences
No full textWe present a genome assembly from an individual Oscarella lobularis (Porifera; Homoscleromorpha; Homosclerophorida; Oscarellidae). The genome sequence is 65.2 megabases in span. Most of the assembly is scaffolded into 20 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 20.26 kilobases in length. Gene annotation of the host organism assembly on Ensembl identified 19,260 protein-coding genes. Of twenty-five binned metagenomes, 17 were classified as metagenome-assembled genomes (MAGs). The symbiotic prokaryotic genomes were affiliated with the Alphaproteobacteria (Rhodobacteraceae, Candidatus Rhodobacter lobularis) and Gammaproteobacteria as well as the archaeal Nitrosopumilus sp. clade
The chromosomal genome sequence of the kidney sponge, Chondrosia reniformis Nardo, 1847, and its associated microbial metagenome sequences
No full textWe present a genome assembly from a specimen of Chondrosia reniformis (kidney sponge; Porifera; Demospongiae; Chondrillida; Chondrillidae). The genome sequence has a total length of 117.37 megabases. Most of the assembly (99.98%) is scaffolded into 14 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 17.45 kilobases in length. Several symbiotic bacterial genomes were assembled as MAGs. Gene annotation of the host organism assembly on Ensembl identified 17,340 protein-coding genes. The metagenome of the specimen was also assembled and 53 binned bacterial genomes were identified, including 40 high-quality MAGs that were representative of a typical high microbial abundance sponge and included three candiate phyla (Poribacteria, Latescibacteria, Binatota
Enhancing bycatch escape in trawl fisheries through flow manipulation: a study on Gadoids
No full textFlow manipulation offers a promising yet under-utilized method for enhancing bycatch escape in demersal trawl fisheries by exploiting fish swimming behaviors, such as flow refuging. We investigated how different roundfish species use a low-flow zone to escape from a trawl. A 360° radial escape opportunity was created by placing a gap in the codend within the low-flow zone generated by a tarpaulin funnel. An additional tarpaulin deflector expanded the low-flow zone to prevent fish from holding around the funnel. This approach, designed using flume tank trials and computational fluid dynamics, was tested during sea trials. Substantial escape rates were observed for cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and whiting (Merlangius merlangus). Cod showed an increased escape rate with length, while no such trend was seen in haddock or whiting. We tested two gap sizes and found that a shorter gap size resulted in higher escape rates for undersized haddock and whiting, while cod escape was unaffected by gap size. These findings suggest species-specific interactions between hydrodynamics and behavior for bycatch reduction in trawl fisheries
Quantifying Organic Carbon Remineralization in the Twilight Zone of the Western North Pacific Using Particulate Excess Barium
No full textThe twilight zone plays a pivotal role in the oceanic carbon cycle because large amounts of organic carbon (OC) exported from the euphotic zone are degraded within this layer. However, the magnitude and variability of this remineralization flux remain incompletely understood, particularly across varying regional scales. Using a new particulate excess barium (PBaxs)-oxygen utilization rate transfer function, this study examines spatial patterns of twilight zone OC remineralization fluxes (FOC_remineral) in the western North Pacific (wNP) and the South China Sea (SCS). Results reveal a pronounced latitudinal gradient in wNP open waters, with PBaxs concentrations and FOC_remineral in the upper 150–600 m increasing from the oligotrophic western North Pacific Subtropical Gyre (NPSG) to the nutrient-rich North Pacific Transition Zone (NPTZ). Despite its subtropical location, the SCS basin shows values comparable to those of the NPTZ. Satellite-derived net primary production (NPP) and export production (EP) distributions generally align with FOC_remineral patterns, indicating a strong association between upper and mesopelagic ocean carbon cycling. Using NPP, EP, and FOC_remineral data, we estimated the twilight zone OC remineralization ratio (r-ratio) relative to the euphotic zone biological pump carbon export efficiency (e-ratio). The NPTZ shows enhanced carbon storage potential, with higher e-ratio and lower r-ratio values, while the western NPSG exhibits an opposite trend, indicating reduced carbon sequestration capacity. This spatial variability underscores the need for a comprehensive understanding of twilight zone OC remineralization and its connection to upper-ocean carbon cycling, in order to accurately assess the biological pump's role in the long-term pelagic carbon sink
