Alfred Wegener Institute for Polar and Marine Research
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Blue-Carbon-Potenziale der deutschen Nord- und Ostsee / Blue Carbon potential of the German North and Baltic Seas
No full textBlue Carbon refers to the organic carbon content stored in the sediment of marine and coastal ecosystems. Against the backdrop of the current climate and biodiversity crisis, the Blue Carbon potential of marine ecosystems and habitats is gaining importance and is being intensively researched and discussed. A study by the German Federal Agency for Nature Conservation (BfN) summarises the current state of knowledge on the Blue Carbon potential of the German North and Baltic Seas. Seagrass beds and salt marshes are already defined as Blue Carbon eco- systems and their contribution to mitigating the climate and biodiversity crisis is well recognised. The role of macroalgae, marine sediments and biogenic reefs is not yet clarified. Nationally, there are so far only few published, usable and spatially sufficiently well resolved data defining the Blue Carbon potential. As a part of efforts to combat climate change, there is a need to preserve Blue Carbon comprehensively, but there are still unanswered questions to be addressed. Based on this BfN literature study, strategies are discussed that specifically contribute to the promotion and preservation of Blue Carbon potential
Quantifying permafrost organic carbon remineralization after redeposition on the ocean floor, using δ13C and F14C.
Get PDFArctic permafrost is a critical global tipping element in a warming climate. Annually, the erosion of coastal permafrost discharges an estimated 5 to 14 Tg of organic carbon (OC) into the Arctic Ocean. Although this previously stored OC has the potential to be reintroduced into the atmosphere, thus accelerating human-induced climate change, little is known about the benthic remineralization processes of permafrost OC after erosion and redeposition on the ocean floor. Our research quantified fluxes of dissolved inorganic carbon (DIC) and analyzed its isotopic composition of nearshore sediments in the Canadian Beaufort Sea, specifically off Herschel Island. Our findings showed a DIC release of 0.217 mmo/m&#178;/d, with an average signature of &#948;13C = -22.44 &#177; 72 &#8240; and F14C = 0.548 &#177; 0.007. Utilizing a model that combines two carbon isotopes, we estimate that approximately 38 &#177; 10% of the released DIC is a result of subsurface degradation of redeposited permafrost OC, with an additional 15 &#177; 12% originating from redeposited active layer OC. Additionally, isotopic endmember analysis was utilized on bacterial membrane lipids from live sedimentary bacteria to determine the relative utilization of OC sources in bacterial communities within shallow subsurface sediment (<25 cm). Our results indicate that, on average, these communities obtain 73 &#177; 10% of their OC from recent marine primary production, 11 &#177; 6% from permafrost OC, and 16 &#177; 11% from active layer OC. This study is the first direct quantitative assessment of the release of permafrost OC into the active carbon cycle after it has been redeposited on the ocean floor, as far as we know. The data suggest that the redeposited permafrost OC is easily accessible and utilized by subsurface bacteria. Considering the immense size and vulnerability of the eroding coastal permafrost OC pool, 27 to 53% of it contributing to benthic DIC fluxes could have a prolonged effect on the world's climate, worsening the climate emergency.</jats:p
Non-indigenous species and their realized niche in tidepools along the South-East Pacific coast
No full textNon-indigenous species (NIS) have the potential to colonize and become established in a wide range of coastal
habitats. Species with broad environmental tolerances can quickly adapt to local conditions and expand their
niches along environmental gradients, and even colonize habitats with extreme abiotic conditions. Here we
report and document the distribution of eight marine NIS (four seaweed and four invertebrate species) found in
tidepools along a 3000 km latitudinal gradient along the Pacific coast of Chile (18.4◦S to 41.9◦S). The seaweed
NIS Codium fragile, Capreolia implexa, Schottera nicaeensis and Mastocarpus latissimus were mostly distributed
towards high latitudes (i.e., more southerly locations), where temperatures in tidepools were low. The invertebrate
NIS Anemonia alicemartinae, Ciona robusta, Bugula neritina and Bugulina flabellata were more common
towards low latitudes, where high temperatures were registered in the tidepools. Across the intertidal gradient,
seaweed NIS were mostly found in pools in the mid and low intertidal zone, while invertebrate NIS occurred
mostly in pools from the mid and upper intertidal zones. The realized niche spaces of NIS (based on the Outlying
Mean Index, OMI) in the study area were mainly influenced by environmental conditions of temperature and
salinity (along the latitudinal and intertidal gradients), while other tidepool characteristics (depth, surface area,
exposition, and complexity) only had minor effects. Five of the eight NIS exhibited a realized niche space
coinciding with the average tidepool environmental conditions, while marginal niches were occupied by species
with affinities for specific temperatures and salinities along the latitudinal and intertidal gradients. Our results
indicate that physiological tolerances to environmental factors play a fundamental role in the distribution of
seaweed and invertebrate NIS in tidepools along the Chilean coast. This study confirms that tidepools offer
suitable conditions for some seaweed and invertebrate NIS, potentially facilitating their invasion into new
natural habitats
Perspektiven eines politikplanenden Biodiversitätsschutzgesetzes: Rechtsrahmen, Ausgestaltung und Forschungsbedarf
Get PDFZusammenfassungDer 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.
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Observations and modeling of areal surface albedo and surface types in the Arctic
Get PDFAn accurate representation of the annual evolution of surface albedo of the Arctic Ocean, especially during the melting period, is crucial to obtain reliable climate model predictions in the Arctic. Therefore, the output of the surface albedo scheme of a coupled regional climate model (HIRHAM-NAOSIM) was evaluated against airborne and ground-based measurements. The observations were conducted during five aircraft campaigns in the European Arctic at different times of the year between 2017 and 2022; one of them was part of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2020. We applied two approaches for the evaluation: (a) relying on measured input parameters of surface type fraction and surface skin temperature (offline) and (b) using HIRHAM-NAOSIM simulations independently of observational data (online). From the offline method we found a seasonally dependent bias between measured and modeled surface albedo. In spring, the cloud effect on surface broadband albedo was overestimated by the surface albedo parametrization (mean albedo bias of 0.06), while the surface albedo scheme for cloudless cases reproduced the measured surface albedo distributions for all seasons. The online evaluation revealed an overestimation of the modeled surface albedo resulting from an overestimation of the modeled cloud cover. Furthermore, it was shown that the surface type parametrization contributes significantly to the bias in albedo, especially in summer (after the drainage of melt ponds) and autumn (onset of refreezing). The lack of an adequate model representation of the surface scattering layer, which usually forms on bare ice in summer, contributed to the underestimation of surface albedo during that period. The difference between modeled and measured net irradiances for selected flights during the five airborne campaigns was derived to estimate the impact of the model bias for the solar radiative energy budget at the surface. We revealed a negative bias between modeled and measured net irradiances (median: -6.4ĝ€¯Wĝ€¯m-2) for optically thin clouds, while the median value of only 0.1ĝ€¯Wĝ€¯m-2 was determined for optically thicker clouds
Seasonality influences the effect of warming on kelp photosynthesis
No full textThe consequences of a year-round warming scenario on the photosynthetic performance
of kelp species are unknown. In times of global warming, fundamental photosynthesis data
are important due to the high temperature dependence. Seasonal photosynthetic performance was
quantified in the kelp Laminaria hyperborea sampled along a depth gradient (2, 4 and 6 m below
mean low water spring tide) at the island of Helgoland (North Sea, Germany). Blade discs were cultivated
at in situ irradiances and temperatures (spring: 7°C; summer: 16°C; autumn: 14°C; winter:
6°C) and in parallel under warming scenarios (+4°C) for 3 d. The results highlighted that seasonality
and collection depth had a stronger effect on oxygen formation (photosynthesis versus irradiance
curve) and pigmentation than short-term warming, as there is a stronger correlation with
changing irradiance levels than with temperature. Photosynthesis was highest in spring and
summer, with small impacts of warming, indicating a high resilience to short-term temperature
increases. In summer, algae exhibited reduced maximum quantum yields (Fv/Fm) at sub-lethal temperatures
(20°C), pointing to a moderate stress response. Photosynthetic acclimation along the
depth gradient was intensified by short-term warming, reflected in a stronger decrease in Pmax and
chlorophyll content. Overall, the influence of short-term warming on the depth acclimation varied
seasonally, underlining the importance of considering the season. In conclusion, L. hyperborea
revealed distinct seasonal photosynthetic response patterns and a high photoacclimation potential
at different depths. Therefore, seasonal and depth effects need to be considered when predicting
the effects of warming on kelp primary production
A belly full of jelly? DNA metabarcoding shows evidence for gelatinous zooplankton predation by several fish species in Greenland waters
Get PDFThe waters of Greenland harbour a high species richness and biomass of gelatinous zooplankton (GZP); however, their role in the diet of the many fish species, including commercially exploited species, has not yet been verified. Traditionally, GZP was considered to be a trophic dead end, i.e. with a limited contribution as prey for higher trophic levels. We applied DNA metabarcoding of two gene fragments (COI, 18S V1–V2) to the stomach contents of seven pelagic and demersal fish species in Greenland waters, to identify their prey composition as well as the occurrence of GZP predation. We detected GZP DNA reads in the stomachs of all investigated fish species, with frequency of occurrences ranging from 12.5% (for Melanogrammus aeglefinus) to 50% (for Argentina silus). GZP predation had not yet been reported for several of these species. GZP were found to majorly contribute to the diet of A. silus and Anarhichas denticulatus, particularly, the siphonophore Nanomia cara and the scyphozoan Atolla were of a high importance as prey, respectively. The use of multiple genetic markers enabled us to detect a total of 59 GZP taxa in the fish stomachs with several GZP species being detected only by one of the markers
