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1. Wochenbericht AL634
No full text1. Wochenbericht FS Alkor Reise 634, Fahrtabschnitt 16.06.-22.06.202
More realistic plankton simulation models will improve projections of ocean ecosystem responses to global change
No full textPlankton models form the core of marine ecosystem simulators, with uses from regional resource and ecosystem management to climate change projections. In this Perspective, we suggest that stronger alignment of models with empirical knowledge about plankton physiology, diversity and trophic roles will improve model utility and the reliability of their outputs regarding biodiversity, ecophysiology, trophic dynamics and biogeochemistry. We recommend key steps to resolve the disconnect between empirical research and simulation models accounting for well-established plankton processes with an aim to increase the utility of such models for applied uses. A central challenge is characterizing the complexity of plankton diversity and activity in ways that are amenable to model incorporation. We argue that experts in empirical science are best placed to advise the development of next-generation models to address these challenges, and we propose a series of actions to achieve that engagement, including involvement of these experts in the design and exploitation of plankton digital twins
Basin-wide and coastal modes of north tropical Atlantic variability have distinct impacts on hurricanes
No full textWarm sea surface temperature anomalies in the north tropical Atlantic are conducive to increased intensity and frequency of Atlantic hurricanes. The period 2023-2024 saw two consecutive warm events but with distinct anomaly patterns. Here we use observations and model outputs over the past several decades to determine whether there exists inherent diversity in north tropical Atlantic surface temperature spatial structures and impacts. We find two distinctive modes of variability: a basin-wide mode and a coastal mode, underpinned by differing relationships between air-sea heat flux and sea surface temperature anomalies. The basin-wide mode has a stronger influence on Atlantic hurricane activity due to its more westward and persistent anomaly pattern. Since the 1990s, the well-known impact from El Niño-Southern Oscillation on the north tropical Atlantic is felt through its influence on the basin-wide mode. Our results highlight the importance of distinguishing the two distinctive modes in assessing and predicting their impacts
Comments on the 2025 ICES assessments of the Baltic Sea, North Sea and Arctic stocks
No full textOf the 67 stocks included in this overview, 13 (19%) are in good status and fished sustainably as required by the Common Fisheries Policy (CFP) of the EU, 18 (27%) are fished sustainably but are too small to produce maximum sustainable yields (MSY) and/or have other problems such as recruitment failures or declining biomass, and 36 (54%) are subject to ongoing overfishing and/or are depleted or collapsed (Fig. 1). Biomass forecasts and catch advice are questionable (?, likely too high) for 21 (31%) stocks based on historical assessment results (Fig. 2 in most assessments). Fifteen stocks (#, 22%) are collapsed and prevented from recovery by ongoing fishing, see also ‘Predator Pit’ box below
Assessing Occurrence Patterns of Shallow Hikurangi Slow Slip Events Using Renewal Processes
No full textWe investigate the occurrence patterns of SSEs along the shallow ((Formula presented.) 15 km) portion of the Hikurangi subduction zone. First, we build a manual catalog constraining timing and length of 92 SSEs between 2006 and 2024. Then, we investigate SSE occurrence patterns by fitting a renewal process, using Bayesian inference to obtain the posterior distribution of model parameters. Our results show that SSE recurrence intervals vary along the Hikurangi margin; less frequent SSEs occur in the southern part of the margin. The periodicity of SSEs also changes along strike. SSEs in the northern part of the margin occur more regularly than those at the central part. Finally, we do not find conclusive evidence that 2016 (Formula presented.) 7.8 Kaikōura earthquake had a lasting effect on SSE occurrence patterns
Arctic Ocean virus communities and their seasonality, bipolarity, and prokaryotic associations
No full textViruses of microbes play important roles in ocean environments as agents of mortality and genetic transfer, influencing ecology, evolution and biogeochemistry. However, we know little about the diversity, seasonality, and host interactions of viruses in polar waters. Here, we study dsDNA viruses in the Arctic Fram Strait across four years via 47 long-read metagenomes of the cellular size-fraction. Among 5662 vOTUs, 98% and 2% are Caudoviricetes and Megaviricetes, respectively. Viral coverage is, on average, 5-fold higher than cellular coverage, and 8-fold higher in summer. Viral community composition shows annual peaks in similarity and strongly correlates with prokaryotic community composition. Using network analysis, we identify putative virus-host interactions and six ecological modules associated with distinct environmental conditions. The network reveals putative novel cyanophages with time-lagged correlations to their hosts (in late summer) as well as diverse viruses correlated with Flavobacteriaceae, Pelagibacteraceae, and Nitrosopumilaceae. Via global metagenomes, we find that 42% of Fram Strait vOTUs peak in abundance in high latitude regions of both hemispheres, and encode proteins with biochemical signatures of cold adaptation. Our study reveals a rich diversity of polar viruses with pronounced seasonality, providing a foundation for understanding viral regulation and ecosystem impacts in changing polar oceans
Vergleich von schiffs- und satellitengestützten AOD-Messungen im tropischen Atlantik während M207 und M208
No full textHydrothermal activity along the young, ultra-slow spreading Red Sea Rift – an update from recent discoveries
No full textHydrothermal activity has been intensively studied at mature mid-ocean ridges and is crucial for
the formation of mineral resources, as habitats for chemosynthetic communities, and for the
cooling of the newly formed oceanic lithosphere1. However, the role of hydrothermal circulation in
the early history of a young emerging ocean basin shortly after continental breakup and the
geological expression of its hydrothermal vents, their geochemical characteristics, and their
associated ecosystems can only be studied at a few locations. The Red Sea Rift is one of Earth’s
youngest ocean basins, but despite ample indications for hydrothermal activity based on rock
chemistry, the presence of extinct chimney fields, metalliferous sediments, and high-temperature
brine poolssee overview in the first direct observation of active hydrothermal vents was only reported
in 2022. These vents at the axial volcano, Hatiba Mons, constitute one of the largest active
hydrothermal areas worldwide, hosting 43 individual fields. In contrast to many mature locations,
no high-temperature vent nor specialized macro-fauna was observed. Instead, the vents were
characterized by low-temperature fluids, numerous Fe-Mn-oxyhydroxide mounds, and thriving
microbial mats. As this was the first active hydrothermal area observed in the Red Sea, the
question remains if this is typical for the Red Sea and potentially for young mid-ocean ridges.
Here we present the outcomes of two expeditions in 2023 with the R/V Aegaeo (KRSE5-1) and R/V
Meteor (M194)4, which resulted in the discovery of five more hydrothermally active areas
distributed along the Red Sea Rift between 17°N and 25°N at water depths between 400-1,800 m.
All hydrothermal areas consist of multiple smaller vent fields with similar low-temperature venting
as reported from Hatiba Mons. The locations of the vents in their geological context and the
expressions of hydrothermal occurrences show some variations ranging from small chimneys
along fault lines to larger mounds covering wider areas. We compare the six hydrothermal fields
in terms of their geology, geomorphological expression, precipitate chemistry, and fluid
characteristics to evaluate their regional differences and similarities to further understand the
nature of hydrothermal venting in a young oceanic basin