ALBERT

Description: The southeastern tropical Atlantic hosts a coastal upwelling system characterized by high biological productivity. Three subregions can be distinguished based on differences in the physical climate: the tropical Angolan and the northern and southern Benguela upwelling systems (tAUS, nBUS, sBUS). The tAUS, which is remotely forced via equatorial and coastal trapped waves, can be characterized as a mixing-driven system, where the wind forcing plays only a secondary role. The nBUS and sBUS are both forced by alongshore winds and offshore cyclonic wind stress curl. While the nBUS is a permanent upwelling system, the sBUS is impacted by the seasonal cycle of alongshore winds. Interannual variability in the region is dominated by Benguela Niños and Niñas that are warm and cold events observed every few years in the tAUS and nBUS. Decadal and multidecadal variations are reported for sea surface temperature and salinity, stratification and subsurface oxygen. Future climate warming is likely associated with a southward shift of the South Atlantic wind system. While the mixing-driven tAUS will most likely be affected by warming and increasing stratification, the nBUS and sBUS will be mostly affected by wind changes with increasing winds in the sBUS and weakening winds in the northern nBUS.

Description: This study investigates extreme wet and dry conditions over the humid tropics and their connections to the variability of the tropical ocean basins using observations and a multi-model ensemble of 24 state-of-the-art coupled climate models, for the 1930–2014 period. The extreme wet (dry) conditions are consistently linked to Central Pacific La Niña (Eastern Pacific El Niño), the weakest being the Congo basin, and homogeneous patterns of sea surface temperature (SST) variability in the tropical Indian Ocean. The Atlantic exhibits markedly varying configurations of SST anomalies, including the Atlantic Niño and pan-Atlantic decadal oscillation, with non-symmetrical patterns between the wet and dry conditions. The oceanic influences are associated with anomalous convection and diabatic heating partly related to variations in the strength of the Walker Circulation. The observed connection between the Amazon basin, as well as the Maritime continent, and the Indo-Pacific variability are better simulated than that of the Congo basin. The observed signs of the Pacific and Indian SST anomalies are reversed for the modelled Congo basin extreme conditions which are, instead, tied to the Atlantic Niño/Niña variability. This Atlantic–Congo basin connection is related to a too southerly location of the simulated inter-tropical convergence zone that is associated with warm SST biases over the Atlantic cold tongue. This study highlights important teleconnections and model improvements necessary for the skillful prediction of extreme precipitation over the humid tropics.

Description: Interest in deep-sea mining for polymetallic nodules as an alternative source to onshore mines for various high-technology metals has risen in recent years, as demands and costs have increased. The need for studies to assess its short- and long-term consequences on polymetallic nodule ecosystems is therefore also increasingly prescient. Recent image-based expedition studies have described the temporal impacts on epi-/megafauna seafloor communities across these ecosystems at particular points in time. However, these studies have failed to capture information on large infauna within the sediments or give information on potential transient and temporally limited users of these areas, such as mobile surface deposit feeders or fauna responding to bloom events or food fall depositions. This study uses data from the Peru Basin polymetallic nodule province, where the seafloor was previously disturbed with a plough harrow in 1989 and with an epibenthic sled (EBS) in 2015, to simulate two contrasting possible impact forms of mining disturbance. To try and address the shortfall on information on transient epifauna and infauna use of these various disturbed and undisturbed areas of nodule-rich seafloor, images collected 6 months after the 2015 disturbance event were inspected and all Lebensspuren, 'traces of life', were characterized by type (epi- or infauna tracemakers, as well as forming fauna species where possible), along with whether they occurred on undisturbed seafloor or regions disturbed in 1989 or 2015. The results show that epi- and endobenthic Lebensspuren were at least 50% less abundant across both the ploughed and EBS disturbed seafloors. This indicates that even 26 years after disturbance, sediment use by fauna may remain depressed across these areas.

Description: To advance underwater computer vision and robotics from lab environments and clear water scenarios to the deep dark ocean or murky coastal waters, representative benchmarks and realistic datasets with ground truth information are required. In particular, determining the camera pose is essential for many underwater robotic or photogrammetric applications and known ground truth is mandatory to evaluate the performance of, e.g., simultaneous localization and mapping approaches in such extreme environments. This paper presents the conception, calibration, and implementation of an external reference system for determining the underwater camera pose in real time. The approach, based on an HTC Vive tracking system in air, calculates the underwater camera pose by fusing the poses of two controllers tracked above the water surface of a tank. It is shown that the mean deviation of this approach to an optical marker-based reference in air is less than 3 mm and 0.3. Finally, the usability of the system for underwater applications is demonstrated.

Description: A new member of the family Flavobacteriaceae (termed Hal144T) was isolated from the marine breadcrumb sponge Halichondria panicea. Sponge material was collected in 2018 at Schilksee which is located in the Kiel Fjord (Baltic Sea, Germany). Phylogenetic analysis of the full-length Hal144T 16S rRNA gene sequence revealed similarities from 94.3 to 96.6% to the nearest type strains of the genus Maribacter. The phylogenetic tree of the 16S rRNA gene sequences depicted a cluster of strain Hal144T with its closest relatives Maribacter aestuarii GY20T (96.6%) and Maribacter thermophilus HT7-2T (96.3%). Genome phylogeny showed that Maribacter halichondriae Hal144T branched from a cluster consisting of Maribacter arenosus, Maribacter luteus, and Maribacter polysiphoniae. Genome comparisons of strain Maribacter halichondriae Hal144T with Maribacter sp. type strains exhibited average nucleotide identities in the range of 75–76% and digital DNA-DNA hybridisation values in the range of 13.1–13.4%. Compared to the next related type strains, strain Hal144T revealed unique genomic features such as phosphoenolpyruvate-dependent phosphotransferase system pathway, serine-glyoxylate cycle, lipid A 3-O-deacylase, 3-hexulose-6-phosphate synthase, enrichment of pseudogenes and of genes involved in cell wall and envelope biogenesis, indicating an adaptation to the host. Strain Hal144T was determined to be Gram-negative, mesophilic, strictly aerobic, flexirubin positive, resistant to aminoglycoside antibiotics, and able to utilize N-acetyl-β-D-glucosamine. Optimal growth occurred at 25–30 °C, within a salinity range of 2–6% sea salt, and a pH range between 5 and 8. The major fatty acids identified were C17:0 3-OH, iso-C15:0, and iso-C15:1 G. The DNA G + C content of strain Hal144T was 41.4 mol%. Based on the polyphasic approach, strain Hal144T represents a novel species of the genus Maribacter, and we propose the name Maribacter halichondriae sp. nov. The type strain is Hal144T (= DSM 114563T = LMG 32744T).

Description: Future changes in the southeastern tropical Atlantic interannual sea surface temperature (SST) variability in response to increasing greenhouse gas concentrations are investigated utilizing the global climate model FOCI. In that model, the Coastal Angola Benguela Area (CABA) is among the regions of the tropical Atlantic that exhibits the largest surface warming. Under the worst-case scenario of the Shared Socioeconomic Pathway 5-8.5 (SSP5-8.5), the SST variability in the CABA decreases by about 19% in 2070–2099 relative to 1981–2010 during the model’s peak interannual variability season May–June–July (MJJ). The weakening of the MJJ interannual temperature variability spans the upper 40 m of the ocean along the Angolan and Namibian coasts. The reduction in variability appears to be related to a diminished surface-layer temperature response to thermocline-depth variations, i.e., a weaker thermocline feedback, which is linked to changes in the mean vertical temperature gradient. Despite improvements made by embedding a high-resolution nest in the ocean a significant SST bias remains, which might have implications for the results.

Description: 3D models, generated from underwater imagery, are a valuable asset for many applications. When acquiring images underwater, light is refracted as it passes the boundary layers between water, housing and the air inside the housing due to the different refractive indices of the materials. Thus the geometry of the light rays changes in this scenario and the standard pinhole camera model is not applicable. As a result, pinhole 3D reconstruction methods can not easily be applied in this environment. For the dense reconstruction of scene surfaces the added complexity is especially challenging, as these types of algorithms have to match vast amounts of image content. This work proposes the refractive adaptation of a PatchMatch Multi-View Stereo algorithm. The refraction encountered at flat port underwater housings is explicitly modeled to avoid systematic errors in the reconstruction. Concepts derived from the axial camera model are employed to handle the high demands of Multi-View Stereo regarding accuracy and computational complexity. Numerical simulations and reconstruction results on synthetically generated but realistic images with ground truth validate the effectiveness of the approach.

Description: Der Biodiversitätsverlust schreitet in bedrohlichem Ausmaß voran. Mit dem Global Biodiversity Framework und voraussichtlich dem Nature Restoration Law bestehen nun auf internationaler und europäischer Ebene vielversprechende Ansätze, ihm Herr zu werden. Jetzt ist der Bundesgesetzgeber – nicht zuletzt aus verfassungsrechtlichen Erwägungen – aufgerufen, daran anzuknüpfen. Dazu bietet sich die Regelungsform eines Rahmen- und Politikplanungsgesetzes an, wie sie schon aus dem Klimaschutzgesetz und dem Klimaanpassungsgesetz bekannt ist. Der Aufsatz beleuchtet den internationalen, europa- und verfassungsrechtlichen Hintergrund eines solchen ‘Biodiversitätsschutzgesetzes’ und diskutiert – unter Zusammenarbeit sowohl rechts- als auch naturwissenschaftlicher Autor:innen – formale und materielle Ausgestaltungsmöglichkeiten.

Description: The deep seafloor of the Northeastern Pacific Ocean between the Clarion and Clipperton Fracture Zones (CCZ) hosts large deposits of polymetallic nodules that are of great commercial interest as they are rich in valuable metals such as manganese, nickel, copper and cobalt. However, mining of these nodules has the potential to severely affect the benthic fauna, whose distribution and diversity are still poorly understood. The CCZ is characterized by strong gradients in sea surface productivity and hence changes in the amount of organic carbon reaching the seafloor, decreasing from mesotrophic conditions in the southeast to oligotrophic conditions in the northwest. Uncovering and understanding changes in community composition and structure along this productivity gradient are challenging but important, especially in the context of future mining impacts. Here, we summarize published data on benthic annelids (polychaetes), a major component of macrobenthic communities in the CCZ. Unlike previous studies, we attempt to explore all available data based on both morphology and genetics collected by box corer and epibenthic sledge. In this regard, we specifically aimed to (a) summarize and compare morphological and molecular data in relation to surface water nutrient conditions and (b) provide recommendations to advance the studies of polychaete biodiversity. Although initial studies on polychaetes in the CCZ were performed as far back as the 1970s, there are still large data gaps further explored in our review. For example, most of the current data are from the eastern CCZ, limiting understanding of species ranges across the region. An association between polychaete communities and the available food supply was generally observed in this study. Indeed, mesotrophic conditions supported higher abundance and species richness in polychaetes as a whole, but for certain groups of species, the patterns appear to be opposite — illustrating that relationships are likely more complex at lower taxonomic levels. A better understanding of biogeographical, ecological and evolutionary processes requires a concerted effort involving increased sampling and sharing of data and material to close existing knowledge gaps.