ALBERT

Description: To investigate scavenging communities associated with carcasses of animals from the water column, we performed experimental food fall studies. We deployed baited camera landers with squid (Loligo vulgaris) and jellyfish (Periphylla periphylla) for 13-35 hours at ~2500 m depth in the Fram Strait at the deep sea Long Term Observatory HAUSGARTEN. The dataset includes all raw count data of scavengers on the food falls sorted by taxon based on image analysis annotation in BIIGLE. Scavengers included Eurythenes gryllus , Scopelocheirus and stegocephalid amphipods, various crustaceans and the gastropod Mohnia.

Description: To investigate scavenging communities associated with carcasses of animals from the water column, we performed experimental food fall studies. We deployed baited camera landers with squid (Illex coindetii), jellyfish (Periphylla periphylla) and fish (Scomber scombrus) for 9-25 hours at 1360-1440 m in the Southern Norwegian Sea. The dataset includes all raw count data of scavengers on the food falls sorted by taxon based on image analysis annoated using ImageJ with the Cell Counter plugin and stored long-term in BIIGLE. Scavengers included lysianassid amphipods (mainly Eurythenes gryllus), ophiuroids, decapod shrimp (Bythocaris spp.) as well as Lycodes frigidus (probably a secondary consumer).

Description: The dataset includes taxon counts of the observed background community at the stations prior to the baited lander deployments as well as area calculations per image. Framegrab images from the OFOS videos were extracted in VLC media player (3.0.11 Vetinari) using the snapshot-tool. Framegrabs were taken every 1.5 minute and additionally as close to the seafloor as possible to have the highest possible resolution. Because of variable image quality, the images were classified into good, medium, and poor quality. In each collected image, organisms were identified to the highest possible taxonomic unit and counted with the Multi-Point tool in ImageJ (ImageJ 1.53g). The annotated area in each image was calculated by setting the scale in ImageJ and then calculating the area with the measure-tool. The total area surveyed was calculated by the sum of the analysed images (total = 8-53 m2 per study region).

Description: Gelatinous zooplankton are increasingly acknowledged to contribute significantly to the carbon cycle worldwide, yet many taxa within this diverse group remain poorly studied. Here, we investigate the pelagic tunicate Pyrosoma atlanticum in the waters surrounding the Cabo Verde Archipelago. By using a combination of pelagic and benthic in situ observations, sampling, and molecular genetic analyses (barcoding, eDNA), we reveal that: P. atlanticum abundance is most likely driven by local island-induced productivity, that it substantially contributes to the organic carbon export flux and is part of a diverse range of biological interactions. Downward migrating pyrosomes actively transported an estimated 13% of their fecal pellets below the mixed layer, equaling a carbon flux of 1.96–64.55 mg C m−2 day−1. We show that analysis of eDNA can detect pyrosome material beyond their migration range, suggesting that pyrosomes have ecological impacts below the upper water column. Moribund P. atlanticum colonies contributed an average of 15.09 ± 17.89 (s.d.) mg C m−2 to the carbon flux reaching the island benthic slopes. Our pelagic in situ observations further show that P. atlanticum formed an abundant substrate in the water column (reaching up to 0.28 m2 substrate area per m2), with animals using pyrosomes for settlement, as a shelter and/or a food source. In total, twelve taxa from four phyla were observed to interact with pyrosomes in the midwater and on the benthos.

Description: 4/2/2019 – 24/2/2019, Mindelo (Republic of Cape Verde) – Mindelo (Republic of Cape Verde) DeepC-Jelly We proposed to test the hypothesis that large gelatinous macrozooplankton (e.g. tunicates, hydrozoans) are a significant carbon storage in midwater, and a vector for carbon from midwater to the ocean floor in Cape Verde. To test this hypothesis, we studied 1) the distribution, diversity and abundance of gelatinous organisms in the epi-, meso-, and bathypelagic zone, 2) their role in transporting carbon through the pelagic foodweb to the seafloor and 3) their behavior and associations. We worked in the coastal deep sea off Santo Antão and Fogo as well as in the open ocean at the time series station CVOO and an eddy. A manned submersible was used for mesopelagic surveys, to document the behaviour and associations of deep-sea organisms and to collect living specimens. We performed pelagic video transects, discrete net sampling, and eDNA sampling down to 3000 m. ADCP and CTD transects allowed a detailed reconstruction of the effect of the islands on currents and productivity. To quantify the carbon flux of pelagic foodfalls, we also surveyed the seafloor. Sample and video analysis is still in progress, but first results indicate the impact of the pelagic tunicate Pyrosoma atlanticum, which is an upwelling-favored species largely absent from the oligotrophic open ocean, in the nearshore regions of Cape Verde as well as in the cyclonic eddy sampled. It was also observed on the seafloor and resembles a food source and a habitat in the water column and in the benthos. Specimens of pelagic fauna were collected that allow new species descriptions. New records and a new species for the region were also observed during benthic surveys. The cruise was documented in various outreach activities including national television in Cabo Verde.

Description: We proposed to test the hypothesis that large gelatinous macrozooplankton (e.g. tunicates, hydrozoans) are a significant carbon storage in midwater, and a vector for carbon from midwater to the ocean floor in Cape Verde. To test this hypothesis, we studied 1) the distribution, diversity and abundance of gelatinous organisms in the epi-, meso-, and bathypelagic zone, 2) their role in transporting carbon through the pelagic foodweb to the seafloor and 3) their behavior and associations. We worked in the coastal deep sea off Santo Antão and Fogo as well as in the open ocean at the time series station CVOO and an eddy. A manned submersible was used for mesopelagic surveys, to document the behaviour and associations of deep-sea organisms and to collect living specimens. We performed pelagic video transects, discrete net sampling, and eDNA sampling down to 3000 m. ADCP and CTD transects allowed a detailed reconstruction of the effect of the islands on currents and productivity. To quantify the carbon flux of pelagic foodfalls, we also surveyed the seafloor. Sample and video analysis is still in progress, but first results indicate the impact of the pelagic tunicate Pyrosoma atlanticum, which is an upwelling-favored species largely absent from the oligotrophic open ocean, in the nearshore regions of Cape Verde as well as in the cyclonic eddy sampled. It was also observed on the seafloor and resembles a food source and a habitat in the water column and in the benthos. Specimens of pelagic fauna were collected that allow new species descriptions. New records and a new species for the region were also observed during benthic surveys. The cruise was documented in various outreach activities including national television in Cabo Verde.

Description: Gelatinous zooplankton are increasingly acknowledged to contribute significantly to the carbon cycle worldwide, yet many taxa within this diverse group remain poorly studied. Here, we investigate the pelagic tunicate Pyrosoma atlanticum in the waters surrounding the Cabo Verde Archipelago. By using a combination of pelagic and benthic in situ observations, sampling, and molecular genetic analyses (barcoding, eDNA), we reveal that: P. atlanticum abundance is most likely driven by local island-induced productivity, that it substantially contributes to the organic carbon export flux and is part of a diverse range of biological interactions. Downward migrating pyrosomes actively transported an estimated 13% of their fecal pellets below the mixed layer, equaling a carbon flux of 1.96–64.55 mg C m−2 day−1. We show that analysis of eDNA can detect pyrosome material beyond their migration range, suggesting that pyrosomes have ecological impacts below the upper water column. Moribund P. atlanticum colonies contributed an average of 15.09 ± 17.89 (s.d.) mg C m−2 to the carbon flux reaching the island benthic slopes. Our pelagic in situ observations further show that P. atlanticum formed an abundant substrate in the water column (reaching up to 0.28 m2 substrate area per m2), with animals using pyrosomes for settlement, as a shelter and/or a food source. In total, twelve taxa from four phyla were observed to interact with pyrosomes in the midwater and on the benthos.

Description: In the deep sea, benthic communities largely depend on organic material from the overlying water column for food. The remains of organisms on the seafloor (food falls) create areas of organic enrichment that attract scavengers. The scavenging rates and communities of food falls of medium-sized squid, fish and jellyfish (1-100 cm) are poorly known. To test our hypothesis that scavenging responses are specific for different food falls, we deployed camera landers baited with squid, jellyfish and fish for 9 to 25 h at 1360 to 1440 m in the southern Norwegian Sea. Image analysis of 8 deployments showed rapid food fall consumption (20.3 +/- 1.4 [SD] to 31.6 +/- 3.7 g h(-1)) by an amphipod-dominated scavenging community that was significantly different between the food fall types. Fish and squid carcasses were mostly attended by amphipods of the genus Eurythenes. Smaller unidentified amphipods dominated the jellyfish experiments together with brittle stars (cf. Ophiocten gracilis) and decapod shrimps (cf. Bythocaris spp.); the latter only occurred on jellyfish carcasses. The removal time for jellyfish (similar to 17 h) was almost twice as long as that for squid and fish (9-10 h). The maximum scavenger abundance was significantly higher on fish carcasses than on jellyfish and squid. The times at which abundances peaked were similar for jellyfish and fish (after 8-9 h) but significantly sooner for squid (3.00 +/- 0.35 h). Our results, although based on a small number of experiments, demonstrate differences in scavenging responses between food fall species, suggesting tight coupling between the diversity and ecology of benthic scavenging communities in the Norwegian Sea.

Description: Highlights: • Food fall scavenger experiments were conducted in the Fram Strait. • At 2500 m depth, carcasses of squid were consumed 7.6 times faster than those of jellyfish. • Amphipods dominated squid food falls but were virtually absent on jellyfish foodfalls • Invertebrate food falls in the Arctic attracted a total of 15 taxa. • Food fall scavenger community composition and consumption rates are depth-dependent. Abstract: Deep-sea benthic communities depend on food that reaches the seafloor from the overlying water column as well as from in-situ autotrophic production. Sinking carcasses (food falls) from jellyfish and squid contribute to this nutrient flux, but natural medium-sized food falls are rarely observed. Consequently, little is known about scavenging communities associated with invertebrate food falls. The Arctic Ocean is known for rapid environmental change and strong benthic-pelagic coupling. To investigate if scavenging responses in the Arctic deep sea differ between medium-sized food fall species we performed experiments in the Fram Strait at ∼2500 m depth. Baited free fall landers were equipped with a time-lapse camera (n = 5) and traps (n = 4) to document and capture scavengers. Squid (Loligo vulgaris) and jellyfish (Periphylla periphylla) were used as bait. Image analysis showed that the amphipod Eurythenes gryllus arrived within minutes and was the main scavenger on squid (MaxN = 166 individuals) while it was almost absent (MaxN = 3 individuals) on jellyfish. Nine additional scavenger taxa were identified in total, including Scopelocheirus and stegocephalid amphipods, various crustaceans and the gastropod Mohnia. The jellyfish bait was consumed 7.6 times slower than squid (jellyfish: 171 g d−1, squid: 1,294 g d−1), and almost three times slower than during similar experiments in the North Atlantic. Squid experiments incited higher consumption rates and scavenger diversity, but lower maximum abundances than similar experiments in the North Atlantic. Despite a small sample size of our experiments, differences in consumption rates, scavenger diversity and successional stages between food falls were apparent supporting that scavenging response depends on carcass species.

Description: Seamount systems offer a diverse range of habitats which support the local communities influenced by the hydrographic specifics of the mount area. Efforts to investigate the benthic communities of the Arctic as well as seamounts have risen in the last years, yet the knowledge in these areas remains scarce. For this study the macrofaunal distribution, biodiversity and abundance was studied along a depth gradient based on material collected along the Langseth Ridge for the first time (Gakkel Ridge, Central Arctic Ocean) and in the surrounding area during the R.V. Polarstern expedition PS101. The macrofaunal samples were obtained with a giant box corer (0.25 m²) at seven stations (three replicates each), ranging from a mean depth of 645 m to 3873 m. Common paradigms were tested with additional data from the adjacent basins. The community was strongly structured by depth and featured three distinctive faunal assemblages, the mount, transition and deep assemblage. These varied in species composition, diversity and densities. While biodiversity was found to be highest at intermediate depth levels, i.e. the transition assemblage (~1000-1800m), average species numbers and densities decreased and species evenness increased with increasing depth. A total of 65 putative species, belonging to 14 major taxa, were identified with at least four of these species potentially being new and endemic. Polychaetes contributed the most towards species diversity, while the poriferan Geodia parva exhibited highest overall densities and thus dominated the mount assemblage. The faunal patterns of this study reflect those observed at various other seamounts. While the hypothesis of seamounts as biological hotspots was confirmed for this high Arctic environment, this doesn’t necessarily imply true geographic boundaries. The overall results, with the mount assemblage being very similar on all three mounts, agree with the idea of seamounts serving as stepping stones, enhancing population connectivity. Whether the mounts of the Langseth Ridge can be regarded as island according to the island theory for seamounts will have to be investigated in future studies on larger spatial scales, including genetic analyses on species, in order to gain scientific evidence. However, seamounts, particularly in such extreme environments, are highly vulnerable and valuable marine ecosystems due to their high potential for population connectivity, as well as their potential as a source to maintain populations in surrounding sink habitats.