The IASC Marine Working Group (MWG) provided funding to facilitate and support the participation of an early career scientist on a research cruise operated by an international partner in 2022, and again in 2023. The project´s primary goal is to increase the participation of early career scientists and/or Indigenous knowledge holders on ships conducting oceanographic research in the Arctic on a cross-platform, international basis (platforms that would allow the participation of one country's scientist(s) on another's country's vessel). The object of this program in general is to improve international cooperation and coordination, data sharing, complement observations, and collaboration across international boundaries. This project supported travel to join the ship; shipboard costs are expected to be borne by the host country.

EvaLopesWith funding received by the IASC Marine Working Group and the support of the Japan Agency for Marine Science and Technology (JAMSTEC), and especially Dr. Takashi Kikuchi of JAMSTEC, Eva Silva Lopes of the Universidade do Porto (Portugal) was selected to join the expedition. Lopes was previously accepted by JAMSTEC as part of a team of international early-career scientists who had applied to participate on the 2023 RV Mirai research cruise to the Arctic. During her time onboard of Mirai, Ms. Lopes undertook studies on microbial biogeochemistry and the microbial biome. She has presented a poster at the XV Portuguese Conference of Polar Sciences describing her experience and more formal scientific results will be forthcoming. Ms. Lopes provided a description of her work aboard the ship, which follows.

With the temperature increase of the Pacific and Atlantic Oceans, nutrient redistribution will be affected. This will also include distributional shifts in several Arctic and sub-Arctic species, including the microbiome. Microbes play pivotal roles within the marine food web, contributing significantly to key biogeochemical cycles that sustain water column primary productivity. Understanding climate change's impact on prokaryotic (bacteria and archaea) and protist members of microbial communities is crucial. This understanding should include their diversity, spatial distribution, and interactions. Analysing the change in the redistribution of plankton microbial communities and their functions within the changing Arctic Ocean is crucial since they form a web of highly diverse species and functions that quickly react to change, dictating shifts on ocean primary production and consequently on ecosystem sustainability. In my PhD project, I aim to investigate the Arctic Ocean prokaryotic and unicellular eukaryotic communities from a community dynamics and ecological perspective by understanding how planktonic prokaryotic and unicellular eukaryotic communities interact with each other.

Throughout the campaign, the Arctic Ocean prokaryotic and unicellular eukaryotic communities will be analysed from an ecological standpoint. Firstly, we'll uncover the crucial links (taxonomic and functional) between these communities. Secondly, we will study how environmental variations in Pacific and Arctic water masses impact the interaction dynamics among planktonic prokaryotes and unicellular eukaryotes. During the Mirai expedition, I collected seawater samples in multiple stations at different depths for microplankton analysis. The chosen area of this campaign was the Pacific Arctic Region, starting in Dutch Harbor (Alaska, USA), crossing areas such as the Bering Strait, Chukchi Shelf, Canada Basin, Barrow Canyon, and the East Siberian Sea. The samples were collected using 12 L Niskin bottles on a CTD/Rosette multi-sampler, between the 7th and 30th of September 2023. CTD and routine samples, at several depths, were taken of the following parameters: 18O isotopes, pH, dissolved inorganic carbon, salinity, nutrients, and chlorophyll-a. For my DNA samples, the chosen depths were the deep chlorophyll maximum and the bottom depth sampled at each station. After the seawater samples collection, samples were filtered through a Sterivex® filter with a 0.22 μM pore size and stored at −80°C until further genomic and metagenomic analysis. These samples were collected to observe the dynamics of the microbial communities across the water column in the Arctic Ocean. Additionally, across the Chukchi Sea, opportunistic sampling occurred. Sediment samples were collected from a multiple core sampler, Ashura, and interstitial water was filtered through a Sterivex® filter with a 0.22 μM pore size and stored at −80°C, until further analysis. These samples were collected to compare the microbial community differences between the sediments and water, with a special focus on diatoms. A total of 144 seawater samples were collected during this campaign. Due to the progressive intensification of the Pacific and Arctic water connectivity, and considering heat transport, it is predicted that community functions will change. With this in mind, onboard the R/V Mirai, a microcosm experience was performed, where the Pacification phenomenon was reproduced. The aim was to mix surface waters, collected at 100m, with bottom waters, collected at 300m, and analyse which interactions between the communities change during 48 hours of incubation (Figure 2). The dynamic Barrow Canyon area was selected for this study. Water collected at 100m was classified as “Remnant Winter Water” and water collected at 300m was classified as “Atlantic Water”. The output of these microcosm experiments will allow us to observe how these communities change their interactions in these changing environments and especially will allow us to see if the communities on the different sides of the Arctic Ocean have or do not have the same behaviour.

saewatersamplesPrevious studies have not gathered enough spatial and temporal information about the movement and change over time of tiny life in the North Pacific and Arctic areas because there is not much biological data from these remote regions. Indeed, long-term data sets from these regions are available for physical variables like temperature and salinity, which limits modeling approaches to predict the response of biological communities to climate change. Opportunities like the Mirai campaign help to bridge this knowledge gap in the Arctic Ocean by promoting study and understanding of prokaryotic and unicellular eukaryotic planktonic communities. A fundamental question is which community functions will change due to the progressive intensification of the Pacific and Arctic water connectivity, as heat transport accelerates. It is essential to fill this knowledge gap by undertaking observations to understand how the increase of the Pacific heat inflow to the Arctic will promote shifts in Arctic plankton microbiome diversity and functions. This is crucial because there are some dramatic changes, in particular the retreating ice edge and increased heat influx of North Pacific water, happening in this crucial transition area but the impact of these changing trends on microplankton is poorly studied.

3 (scientific) highlights:

  • Project successfully increased international participation in US-led (2022) and Japanese-led research cruises (2023) by German (2022) and Portuguese graduate students (2023).
  • Focus of the scientific effort supported in both years has been on microbial biogeochemistry and genomics
  • The impacts of climate warming in the Arctic are key motivating factors.

Figure 1 (top): Eva Lopes, Early Career Scientist funded by IASC to participate on the campaign on board of the R/V Mirai.
Figure 2: Seawater sampling material used for the microcosms.

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