Background of the cruise

Background and purpose of the cruise

Arctic sea ice has declined significantly over the past several decades and is expected to decline further in the future. In addition, the Arctic region has warmed more markedly than the global average and is expected to continue to warm more significantly than the global average, which is known as Arctic Amplification. Sea ice reduction and rising sea surface temperatures are changing lower-trophic ecosystems such as phytoplankton to higher-trophic ecosystems such as marine mammals, affecting biodiversity. The Joint Statement of the 3rd Arctic Science Ministerial in Tokyo in 2021 noted that "The effect of the loss of sea ice is speeding up coastal erosion and marine ecosystem change, which can have broader socio-economic impacts in the Arctic." In order to conserve Arctic ecosystems and biodiversity, it is important to collect scientific information through surveys and monitoring, and to take measures based on a better understanding of this information.

The Oshoro-Maru has made many contributions to our understanding of environmental changes in the Arctic and their impact on ecosystems. For example, data analysis of fish sampled by the Oshoro-Maru between 1990 and 2013 showed that the community structure of benthic fishes such as walleye pollock is strongly influenced by the timing of sea ice retreat (Nishio et al., 2020). Recently, we conducted observations in the northern Bering Sea to southern Chukchi Sea in 2017, when sea ice melt in the northern Bering Sea was as usual, and in 2018, when sea ice melt was earlier than recorded (Ueno et al., 2020). The results revealed that early sea ice melt reduces large zooplankton that are useful as food for fish, resulting in a degraded feeding environment for fish (Kimura et al., 2022). In addition, visual inspection of seabirds indicated that seabirds had difficulty finding food organisms in 2018, when sea ice melt was faster than recorded (Nishizawa et al., 2020).

Supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Arctic Challenge for Sustainability (ArCS II), this cruise will cover the area from the northern Bering Sea to the Chukchi Sea, the marginal sea of the Arctic Ocean, to clarify changes in ocean thermal and material circulation and the marine ecosystem from primary production (phytoplankton) to higher organisms (marine mammals, etc.) by collecting samples for oceanographic observations and breeding experiments, visual inspections, and other methods. Through these observations, we aim to gain a comprehensive understanding of the impact of changes in the marine environment on marine ecosystems. In addition to fish sampling by net trawling, environmental DNA (DNA derived from organisms present in the environment) will be observed in this observation to capture changes in fish community structure from multiple perspectives.

The training ship Oshoro-Maru is a "campus at sea," and the various oceanographic observations conducted on this cruise are conducted as practical training for undergraduate and graduate students. Most of the undergraduate and graduate students who were on board the Oshoro-Maru mainly for research are graduate/undergraduate students of School of Fisheries Sciences, Hokkaido University, but graduate students from other universities, including those from the University of Alaska Fairbanks, with which we have an inter-university exchange agreement, will also be on board the ship to conduct observations and collect data related to their master's and doctoral dissertations. In addition, during the second half of the cruise (Leg 3: Nome, Alaska, U.S.A. to Hakodate, Japan), an open course for undergraduate students from all over Japan will be held for the first time, based on ArCS II Priority Subject 1: Capacity Building and Research Promotion. Ten students from national and private universities, including those from humanities/social-science departments, are scheduled to get board the ship not only for conducting natural science oceanographic observations but also learning the history and culture of the Arctic region. We hope that the students will not only become Arctic researchers, but also be involved directly or indirectly in solving various problems in the Arctic region and spreading knowledge about the region through various social activities such as business, government, education, and non-profit organizations. (https://www.nipr.ac.jp/arcs2/info/oshoro-2023/)