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Die Rolle von Nekton und großem Plankton als Nahrungsquelle für Tiefsee-Lebensgemeinschaften im dynamischen Ozean

Antragsteller Dr. Henk-Jan Hoving
Fachliche Zuordnung Ökologie und Biodiversität der Tiere und Ökosysteme, Organismische Interaktionen
Förderung Förderung von 2017 bis 2022
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 382101453
 
Erstellungsjahr 2023

Zusammenfassung der Projektergebnisse

The Emmy Noether Junior Research Group project "the role of pelagic food falls in subsidizing deep sea benthic communities in a changing ocean” has examined the diversity and distribution of pelagic fauna and their role in the transport of organic matter to the seafloor. Fieldwork and datasets that contributed to project goals consisted of oceanographic campaigns to the Arctic, eastern Atlantic, north Atlantic, Pacific and Antarctica. Extensive examination of seafloor imagery show that observations of food falls are very rare but also diverse. We documented high concentrations of pyrosomes in the eastern Atlantic and Pacific and quantified pyrosome food falls and their scavengers. These studies confirmed our hypothesis that food falls of medium size pelagic fauna may contribute to regional carbon budgets. North of the DISCOL area, a mass deposition of > 200 Argonauta shells was documented on the abyssal plain in the central east Pacific. These observations include the largest deposition of cephalopods remains ever reported in the deep sea, and the first estimate of cephalopod contribution to the inorganic carbon pump. Other food falls documented in this project include crustacean, fish, whale and penguin carcasses. The tracing of cephalopod populations, spent individuals and reviewing literature has provided insight in potential areas of cephalopod carcass deposition with hotspots in the Arctic, Antarctic, Atlantic and Pacific. In the Arctic the squid Gonatus fabricii is a vector of carbon and trace elements. Oceanic islands (Cabo Verde and Azores) also form cephalopod hotspots of diversity. To test the hypotheses that food fall consumption rate, scavenging community and successional stages differ with food fall species and depth we mimicked food falls using free falling landers equipped with time elapse cameras, oceanographic sensors and a bait plate with carcasses (jellyfish, fish or squid). We observed differences in scavenging communities, consumption rate and maximum abundance between food fall species in the same region. A comparison between squid food fall experiments in the Arctic and Norwegian Sea show that increasing depth does not necessarily result in reduced scavenging rates. Scavengers can be used as samplers and via stomach content analysis this approach provided insight in the regional taxonomic diversity of nekton food falls. To test the hypothesis that traces of pelagic species can be detected in sediment via eDNA analysis we analyzed eDNA in sediment from the Arctic and the North Atlantic using a newly developed general 18S primer for Cephalopoda and a primer targeting the 12S gene of fishes. While sedimentary eDNA may not allow quantification of food falls, it provided insights in which species contribute locally to vertical flux of nekton related carbon. More sample analysis and experimental work is needed. eDNA analysis of water column samples from discrete depths from the epi-meso and bathypelagic zone in the Atlantic and Arctic contributed to regional baselines and unique insights in cephalopod diversity and distribution, and the first cephalopod community analysis from eDNA. Pelagic video transects in the deep sea confirmed the project hypothesis that gelatinous fauna are prominent components of Arctic pelagic communities, although the diversity of this community is relatively low compared to tropical and temperate regions. The project benefitted from an elaborate, collaborative institutional, national and international network resulting in unique sampling and research opportunities as well as publications and theses that have impact beyond the project duration. The project has suffered from the Covid-19 pandemic as a result of: canceled fieldwork and lab visits, delayed laboratory work, unavailable external sequencing services and challenges for personnel. The Emmy Noether funding has enabled the establishment of a unique research group in Germany and Europe that combines in oceanographic campaigns, situ observations, experimental work as well molecular genetic techniques, to study the diversity and ecology of elusive pelagic fauna in the deepest regions of our oceans, as well as their role in carbon transport, a major ecosystem service of the deep sea.

Projektbezogene Publikationen (Auswahl)

 
 

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