Using the optical plankton recorder LOKI (Lightframe On-sight Key species Investigations) to elucidate high-resolution vertical distribution patterns of Arctic zooplankton species in Fram Strait

The plankton recorder LOKI provides high-resolution pictures, continuously taken by a 4 Megapixel camera during vertical hauls from 1000 depth to the surface. Linked to each picture, hydrographical parameters are being recorded, e.g. salinity, temperature, oxygen concentration and fluorescence. This allows to exactly identifying distribution patterns in relation to environmental conditions. In order to analyse the community composition, abundance and depth distribution of the species in the Fram Strait, we have conducted two hauls during a RV Polarstern cruise in July/August 2015 (PS93.2) to the deep-sea observatory “Hausgarten” of the Alfred-Wegener-Institute, Germany. We sampled the most northern (79°56’35” N, 3°11’45” E) and the most southern station (78°35’97” N, 5°4”11” E) of the “Hausgarten” monitoring stations. The two stations were similar with regard to zooplankton community composition. Copepods, among which Calanus, Oncaea and Microcalanus were the most frequent genera, dominated with a contribution of more than 80%. Calanus reached the highest abundances in surface layers ( 300m. Abundances at the northern station were twice as high as at the southern station. Mean weighted depths of the dominant taxa were significantly deeper at the northern than at the southern station, which corresponded to the deeper location of the Return Atlantic Intermediate Water

Comparison on vertical distribution of pelagic copepod abundance, biomass and community structure between Atlantic and Pacific sector of the Arctic Ocean

Recently, a great reduction of sea ice coverage has been reported for the Arctic Ocean during summer. The reduction has been reported to be greater for regions which connect the Arctic with the Atlantic and the Pacific Ocean, respectively. Since the pelagic fauna differs between the Atlantic and the Pacific Ocean, the effects of sea ice loss on the species and, thus, the Arctic ecosystems are expected to be different. However, little information is available on the differences in pelagic community between the Atlantic and Pacific sectors of the Arctic Ocean. In this study, we investigated planktonic copepod abundance, biomass and community structure in the Atlantic and Pacific sectors of the Arctic Ocean, and address their differences

Ocean acidification does not alter grazing in the calanoid copepods Calanus finmarchicus and Calanus glacialis

It is currently under debate whether organisms that regulate their acid–base status under environmental hypercapnia demand additional energy. This could impair animal fitness, but might be compensated for via increased ingestion rates when food is available. No data are yet available for dominant Calanus spp. from boreal and Arctic waters. To fill this gap, we incubated Calanus glacialis at 390, 1120, and 3000 µatm for 16 d with Thalassiosira weissflogii (diatom) as food source on-board RV Polarstern in Fram Strait in 2012. Every 4 d copepods were subsampled from all CO2 treatments and clearance and ingestion rates were determined. During the SOPRAN mesocosm experiment in Bergen, Norway, 2011, we weekly collected Calanus finmarchicus from mesocosms initially adjusted to 390 and 3000 µatm CO2 and measured grazing at low and high pCO2. In addition, copepods were deep frozen for body mass analyses. Elevated pCO2 did not directly affect grazing activities and body mass, suggesting that the copepods did not have additional energy demands for coping with acidification, neither during long-term exposure nor after immediate changes in pCO2. Shifts in seawater pH thus do not seem to challenge these copepod species

Testing the usefulness of optical data for zooplankton long‐term monitoring: Taxonomic composition, abundance, biomass, and size spectra from ZooScan image analysis

The pelagic ecosystem of the Arctic Ocean is threatened by severe changes such as the reduction in sea-ice coverage and increased inflow of warmer Atlantic water. The latter is already altering the zooplankton community, highlighting the need for monitoring studies. It is therefore essential to accelerate the taxonomic identification to speed up sample analysis, and to expand the analysis to biomass and size assessments, providing data for modeling efforts. Our case study in Fram Strait illustrates that image-based analyses with the ZooScan provide abundance data and taxonomic resolutions that are comparable to microscopic analyses and are suitable for zooplankton monitoring purposes in the Arctic. We also show that image analysis allows to differentiate developmental stages of the key species Calanus spp. and Metridia longa and, thus, to study their population dynamics. Our results emphasize that older preserved samples can be successfully reanalyzed with ZooScan. To explore the applicability of image parameters for calculating total mesozooplankton and Calanus spp. biomasses, we used (1) conversion factors (CFs) translating wet mass to dry mass (DM), and (2) length–mass (LM) relationships. For Calanus spp., the calculated biomass values yielded similar results as direct DM measurements. Total mesozooplankton biomass ranged between 1.6 and 15 (LM) or 2.4 and 21 (CF) g DM m−2, respectively, which corresponds to previous studies in Fram Strait. Ultimately, a normalized biomass size spectra analysis provides 1st insights into the mesozooplankton size structure at different depths, revealing steep slopes in the linear fit in communities influenced by Atlantic water inflow

Ecosystem mapping in the Central Arctic Ocean (CAO) during the MOSAiC Expedition

As a result of global warming, the marine ecosystem around the North Pole, the Central Arctic Ocean (CAO), is in fast transition from a permanently to a seasonally ice-covered ocean. The sea-ice loss will enable summer access to the CAO for non-icebreaking ships, including fishery vessels, in the near future. However, the lack of knowledge on the CAO ecosystem impedes any assessment of the sustainability of potential future fisheries in the CAO. Taking a precautionary approach, nine countries and the EU established in 2021 the Agreement to Prevent Unregulated High Seas Fisheries in the Central Arctic Ocean, which a.o. includes mapping and monitoring of the CAO ecosystem before any commercial fishery is initiated. To reduce the existing lack of knowledge, the EFICA Consortium participated, together with ca. 250 on-board scientists, in sampling and data collection of ecosystem data during four legs of the international MOSAiC expedition in 2019-2020. This report describes the field work performed by the EFICA scientists using water-column acoustics, deep-sea video recording, and fish and eDNA sampling for targeting zooplankton and fish. Further ecosystem data (physical, chemical and biological) were collected by the EFICA scientists in collaboration with other scientists on-board. Together with this report, a metadata database containing lists of all collected samples and data that are relevant for future fishery assessment studies was delivered to the European Commission

Year-round under-ice research on MOSAiC using a remotely operated vehicle

To provide easy and reliable access to the underside of the sea-ice during the MOSAiC expedition, the Alfred-Wegener-Institute will operate its new remotely operated vehicle during the full duration of the drift directly from an access hole on the ice. The vehicle has proven its capabilities during several Arctic field campaigns and provides a stable sensor platform, as well as inspection and intervention capabilities. It has a maximum range of 300m from the designated access hole(s) and a depth rating of 100m. The ROV operations under sea ice will allow repeat measurements during the entire drift with little impact to the sea ice, the upper ocean, the ecosystem and other objects of interest. In the current setup, the vehicle comprises various video cameras, a still camera, single and multibeam bathymetric sonar, scanning sonar, a CTD, triplet fluorometer as well as sensors for hyperspectral irradiance, radiance, extinction, dissolved oxygen, pH and nitrate. The vehicle position is recorded by acoustic positioning tied into the floe fixed reference frame of all observations on the central observatory floe. Beyond this, the vehicle also provides several additional power outlets and data ports that allow connecting additional systems to the vehicle. Currently, the integration of a current profiler (ADCP), a zooplankton camera, different nets for zooplankton sampling, as well as a water sampling system are under development. All data are recorded, timestamped on site, and will be uploaded to an open data portal, which will be easily accessible for the scientific community. The main task of the vehicle will be repeated mapping of the spatial variability of the various parameters on a weekly basis. In addition, we plan to use it for deployment and retrieval of under-ice sensor packages and perform inspection and manipulation tasks. The ROV operations can easily be conducted by a small on-board sea-ice team due to the reliable and redundant system architecture. Altogether, measurements give a comprehensive picture of the spatio-temporal evolution of the sea-ice and its associated ecosystem. They link upper ocean dynamics with the thermodynamic and dynamic development of the ice cover. In combination with surface measurements, like aerial photography and terrestrial laser scanning, a full 3D characterization of the local ice cover will enable areal upscaling of the obtained results also using remote sensing data. Ideally these high resolution measurements at the MOSAiC central observatory will be extended with regular missions of an autonomous underwater vehicle (AUV), which can travel longer distances in spite of a small logistical footprint, to tie the local observations into the context of the larger spatial scale of the MOSAiC distributed measurement network

Childhood and Adolescent Pesticide Exposure and Breast Cancer Risk

To date, epidemiological studies have not strongly supported an association between pesticide exposure and breast cancer. However, few previous studies had the ability to assess specific time periods of exposure. Studies that relied on adult serum levels of metabolites of organochlorine pesticides may not accurately reflect exposure during developmental periods. Further, exposure assessment often occurred after diagnosis and key tumor characteristics, such as hormone receptor status, have rarely been available to evaluate tumor-subtype specific associations. We examine the association between pesticide exposure during childhood and adolescence and breast cancer risk in the prospective Sister Study cohort (N=50,844 women) to assess this relation by tumor subtype

Sea ice decline drives biogeographical shifts of key Calanus species in the central Arctic Ocean

In recent decades, the central Arctic Ocean has been experiencing dramatic decline in sea ice coverage, thickness and extent, which is expected to have a tremendous impact on all levels of Arctic marine life. Here, we analyze the regional and temporal changes in pan-Arctic distribution and population structure of the key zooplankton species Calanus glacialis and C. hyperboreus in relation to recent changes in ice conditions, based on historical (1993–1998) and recent (2007–2016) zooplankton collections and satellite-based sea ice observations. We found strong correlations between Calanus abundance/population structure and a number of sea ice parameters. These relationships were particularly strong for C. glacialis, with higher numbers being observed at locations with a lower ice concentration, a shorter distance to the ice edge, and more days of open water. Interestingly, early stages of C. hyperboreus followed the same trends, suggesting that these two species substantially overlap in their core distribution area in the Arctic Ocean. Calanus glacialis and C. hyperboreus have been historically classified as shelf versus basin species, yet we conclude that both species can inhabit a wide range of bottom depths and their distribution in the Arctic Ocean is largely shaped by sea ice dynamics. Our data suggest that the core distribution patterns of these key zooplankton are shifting northwards with retreating sea ice and changing climate conditions.publishedVersio

Sea ice decline drives biogeographical shifts of key Calanus species in the central Arctic Ocean

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Unprecedented insights into extents of biological responses to physical forcing in an Arctic sub-mesoscale filament by combining high-resolution measurement approaches

In Fram Strait, we combined underway-sampling using the remote-controlled Automated Filtration System for Marine Microbes (AUTOFIM) with CTD-sampling for eDNA analyses, and with high-resolution optical measurements in an unprecedented approach to determine variability in plankton composition in response to physical forcing in a sub-mesoscale filament. We determined plankton composition and biomass near the surface with a horizontal resolution of ~ 2 km, and addressed vertical variability at five selected sites. Inside and near the filament, plankton composition was tightly linked to the hydrological dynamics related to the presence of sea ice. The comprehensive data set indicates that sea-ice melt related stratification near the surface inside the sub-mesoscale filament resulted in increased sequence abundances of sea ice-associated diatoms and zooplankton near the surface. In analogy to the physical data set, the underway eDNA data, complemented with highly sampled phytoplankton pigment data suggest a corridor of 7 km along the filament with enhanced photosynthetic biomass and sequence abundances of sea-ice associated plankton. Thus, based on our data we extrapolated an area of 350 km2 in Fram Strait with enhanced plankton abundances, possibly leading to enhanced POC export in an area that is around a magnitude larger than the visible streak of sea-ice