• Energy Research
• 14. Life underwater close
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AbstractThe Law of the Sea and regional and national laws and agreements require exploited populations or stocks to be managed so that they can produce maximum sustainable yields. However, exploitation level and stock status are unknown for most stocks because the data required for full stock assessments are missing. This study presents a new method [abundance maximum sustainable yields (AMSY)] that estimates relative population size when no catch data are available using time series of catch-per-unit-effort or other relative abundance indices as the main input. AMSY predictions for relative stock size were not significantly different from the “true” values when compared with simulated data. Also, they were not significantly different from relative stock size estimated by data-rich models in 88% of the comparisons within 140 real stocks. Application of AMSY to 38 data-poor stocks showed the suitability of the method and led to the first assessments for 23 species. Given the lack of catch data as input, AMSY estimates of exploitation come with wide margins of uncertainty, which may not be suitable for management. However, AMSY seems to be well suited for estimating productivity as well as relative stock size and may, therefore, aid in the management of data-poor stocks.

Since the 1880s the main preservation method onboard European fishing trawlers was ice manufactured in the fishing ports with mechanized technology based on direct or indirect use of fossil fuels. In 1929 the Norwegian entrepreneur Harald Berg opened a large-scale natural ice factory in northern Norway and challenged the artificial ice producers by providing natural ice to the trawlers, a sustainable and renewable resource. In response, the artificial ice producers tried to discredit natural ice as polluted, unhealthy, and not acceptable for food preservation, with a German district veterinarian at the fishing port of Geestemuende supporting this effort. After several local and Reich authorities became involved, the Reichskuratorium für Technik in der Landwirtschaft conducted an on-site study in Norway in 1936 that stated that there was absolutely no pollution or food safety/health concern and that the ice was safe to be used onboard the trawlers. In the end, the whole campaign by the artificial ice producers in Geestemünde needs to be understood as a campaign of a fossil fuel-based industry to push a competitor out of the market—a competitor who had found a way to manufacture an identical product in a sustainable and renewable way.

LISA cruise has the objective of acquiring new geophysical data in a mostly unexplored region of the SW Iberia Margin, about which many questions exist posing problems to geological interpretation. The LISA cruise acquired geophysical data along a profile (the LISA profile) that cuts across the Ampere seamount, the West Horseshoe Abyssal Palin, the plate boundary region and intersection of the Tore-Madeira Rise with the Gloria fault, and the Atlantic oceanic crust. The cruise consisted on the acquisition of wide angle seismic reflection anf refraction data using 21 OBH from GEOMAR-Kiel and the UTM seismic source. Additional data acquired: magnetic, multibeam bathymetry and backscatter and parasound. Oceanographic data acquired during the LISA Cruise (29SG20220616) on board the Research Vessel Sarmiento de Gamboa in 2022.

AbstractAlthough the role that Pleistocene glacial cycles have played in shaping the present biota of oceanic islands world‐wide has long been recognized, their geographical, biogeographical and ecological implications have not yet been fully incorporated within existing biogeographical models. Here we summarize the different types of impacts that glacial cycles may have had on oceanic islands, including cyclic changes in climate, shifts in marine currents and wind regimes and, especially, cycles of sea level change. The latter have affected geographical parameters such as island area, isolation and elevation. They have also influenced the configurations of archipelagos via island fusion and fission, and cycles of seamount emergence and submergence. We hypothesize that these sea level cycles have had significant impacts on the biogeographical processes shaping oceanic island biotas, influencing the rates and patterns of immigration and extinction and hence species richness. Here we provide a first step toward the development of a glacial‐sensitive model of island biogeography, representing the tentative temporal evolution of those biogeographical parameters during the last glacial cycle. From this reasoning we attempt to derive predictions regarding the imprint of sea level cycles on genetic, demographic or biogeographical patterns within remote island biotas.

In Eastern Boundary Upwelling Systems nutrient-rich waters are transported to the ocean surface, fuelling high photoautotrophic primary production. Subsequent heterotrophic decomposition of the produced biomass increases the oxygen-depletion at intermediate water depths, which can result in the formation of oxygen minimum zones (OMZ). OMZs can sporadically accumulate hydrogen sulfide (H2S), which is toxic to most multicellular organisms and has been implicated in massive fish kills. During a cruise to the OMZ off Peru in January 2009 we found a sulfidic plume in continental shelf waters, covering an area >5500 km(2), which contained ∼2.2×10(4) tons of H2S. This was the first time that H2S was measured in the Peruvian OMZ and with ∼440 km(3) the largest plume ever reported for oceanic waters. We assessed the phylogenetic and functional diversity of the inhabiting microbial community by high-throughput sequencing of DNA and RNA, while its metabolic activity was determined with rate measurements of carbon fixation and nitrogen transformation processes. The waters were dominated by several distinct γ-, δ- and ε-proteobacterial taxa associated with either sulfur oxidation or sulfate reduction. Our results suggest that these chemolithoautotrophic bacteria utilized several oxidants (oxygen, nitrate, nitrite, nitric oxide and nitrous oxide) to detoxify the sulfidic waters well below the oxic surface. The chemolithoautotrophic activity at our sampling site led to high rates of dark carbon fixation. Assuming that these chemolithoautotrophic rates were maintained throughout the sulfidic waters, they could be representing as much as ∼30% of the photoautotrophic carbon fixation. Postulated changes such as eutrophication and global warming, which lead to an expansion and intensification of OMZs, might also increase the frequency of sulfidic waters. We suggest that the chemolithoautotrophically fixed carbon may be involved in a negative feedback loop that could fuel further sulfate reduction and potentially stabilize the sulfidic OMZ waters.

Abstract North Pacific ocean desert (NPOD) refers to the subtropical North Pacific Ocean of low chlorophyll-a (Chl-a) concentrations, as the largest ocean desert globally. Studies have suggested a development of NPOD over recent decades based on limited evidences from in-field measurements and yet elusive mechanism. In this study, we characterize intensity, area and position of the NPOD from year 1998 to 2018, and investigate its control by the coherent climate processes, based on an available, longest satellite observations of Chl-a concentration. Our results suggested that NPOD oligotrophication and expansion processes were correlated with warming upper oceans in most part of the NPOD, except for the SW NPOD area where the Chl-a variations were linked with regional change in sea surface heights. Moreover, based on our analysis, insignificant shift but only NW-SE variability of the NPOD mean position was likely controlled by the Pacific decadal oscillation processes.

The fluvial and aquatic ecosystem of the Tagus River and Entrepeñas reservoir located in the surrounding of the Trillo nuclear power plant (NPP) was evaluated from 1992 to 2008, considering the physical-chemical characteristics, metal content and radiological activity of the water, sediments, algae and fish. The water of both basins demonstrated pH, conductivity, COD, NO3- and DO values within a range considered as good quality and the water quality index (WQI) was found to be within a range of 71-90. Chemometric analysis revealed a shift in the river water (from upstream to downstream) affected by the concentration of salts and metals of natural origin, such as Fe and Al, and slight variations in temperature and radiological activity were detected due to the discharges from the NPP. The hydric conditions contributed to increase or decrease the metal concentration of the river water, the reservoir sediments, algae and fish. Fe and Al were found in higher concentration during drought periods and accumulated in sediments, algae and fish along the river course (from SP1 to SP3). Natural and artificial radionuclides found were 40K with an average of 245 Bq/kg in river sediments, 499 Bq/kg in reservoir sediments and 121 Bq/kg in fish, and 90Sr with a concentration between 0.40 and 1.30 Bq/kg in sediments. Contamination of the aquatic ecosystem with metals and radionuclides was low according to European legislation. In conclusion, this study provides additional elements aimed at understanding the dynamics of fluvial and lentic ecosystems under the influence of different disturbances.