11:00 〜 13:00
[ACG43-P10] 環境DNAメタバーコーディングによる北極圏における魚類群集構造の解析
キーワード：環境DNA、魚類群集、チュクチ海、ベーリング海、メタバーコーディング
Ongoing climate change would induce drastic changes in the Arctic biodiversity and ecosystem. Fish, an essential component of the Arctic ecosystem, can be very susceptible to global warming. Increasing temperature and sea-ice reduction would potentially cause a poleward shift of their distributions and anomalous fluctuations in the abundances. In addition, Arctic fishes contain valuable fishery species like salmons and cods, which are important for the Arctic culture and economy. However, comprehensive research on the Arctic ecosystem has often been difficult by conventional methods (e.g., bottom trawling and statistical analysis of fishery data) because those are labor-intensive and have limitations in operating in a distant area that is difficult to access.
Environmental DNA (eDNA), which is DNA extracted from various environmental samples, is a promising tool to facilitate the study of the Arctic ecosystem. eDNA shed from aquatic organisms in various forms (e.g., cells, feces, gametes) can be retrieved from seawater by filtration and used to detect organisms present in the study site. An increasing number of studies demonstrated that eDNA is a powerful tool for collecting ecological information in diverse aquatic environments, including the Arctic region. Furthermore, eDNA analysis requires a small amount of water so that it is less laborious and can be performed where the conventional method is hardly conducted.
This study aimed to describe fish community structure in the Pacific side of the Arctic region using eDNA analysis. During the Arctic cruise of R/V Mirai (JAMSTEC) held from September to November 2020, eDNA samples were collected from surface seawater in the Chukchi Sea and the Canada Basin (19 sites), and the Bering Sea (nine sites). In addition, seawater was also collected from the bottom or middle of the water column in the Chukchi Sea and off the Barrow Canyon. Collected eDNA was metabarcoded using a high-throughput sequencer to overview the Arctic fish community structure.
Metabarcoding analysis successfully detected fish eDNA from all sites. In the Arctic Ocean, a total of 30 taxa were detected. The number of detected taxa was almost equivalent to that of the Bering Sea (33 taxa), while 12 taxa were exclusively found in the Arctic. The most frequently detected taxon in the Arctic Ocean was Pacific sand lance (Ammodytes hexapterus), followed by pricklebacks (Stichaeidae spp.) and polar cod (Boreogadus saida), which are circumpolar species.
Cluster analysis based on the Jaccard index indicated that the fish community in the northern part of the Chukchi Sea and Canada Basin was discriminated from that in the southern part of the Chukchi Sea and the Bering Sea. It was also found that the fish community in the former region was composed of two distinct clusters. The fish assemblages belonging to these clusters showed sporadic distribution and did not seemingly correspond to geographic location or environmental variables such as water temperature.
Vertical differences in fish assemblages among depths were also suggested in the Chukchi Sea shelf (approx. 50 m deep) and off the Barrow Canyon (approx. 120 m deep). The number of detected taxa was higher in the bottom water than in the surface water. Jaccard index showed that fish assemblages highly varied between depths.
This study demonstrated that eDNA is a promising tool to study the ecological impact of climate change on Arctic fishes. Integrating the results with oceanographic data in the future will provide novel information about the relationship between fish ecology and climate change. However, many technical issues remain to be solved, e.g., completeness of reference database, possible false-negative errors, and optimization of sampling effort. Nevertheless, the use of eDNA will surely prompt future studies to uncover the climate-induced changes in the Arctic ecosystem.
Environmental DNA (eDNA), which is DNA extracted from various environmental samples, is a promising tool to facilitate the study of the Arctic ecosystem. eDNA shed from aquatic organisms in various forms (e.g., cells, feces, gametes) can be retrieved from seawater by filtration and used to detect organisms present in the study site. An increasing number of studies demonstrated that eDNA is a powerful tool for collecting ecological information in diverse aquatic environments, including the Arctic region. Furthermore, eDNA analysis requires a small amount of water so that it is less laborious and can be performed where the conventional method is hardly conducted.
This study aimed to describe fish community structure in the Pacific side of the Arctic region using eDNA analysis. During the Arctic cruise of R/V Mirai (JAMSTEC) held from September to November 2020, eDNA samples were collected from surface seawater in the Chukchi Sea and the Canada Basin (19 sites), and the Bering Sea (nine sites). In addition, seawater was also collected from the bottom or middle of the water column in the Chukchi Sea and off the Barrow Canyon. Collected eDNA was metabarcoded using a high-throughput sequencer to overview the Arctic fish community structure.
Metabarcoding analysis successfully detected fish eDNA from all sites. In the Arctic Ocean, a total of 30 taxa were detected. The number of detected taxa was almost equivalent to that of the Bering Sea (33 taxa), while 12 taxa were exclusively found in the Arctic. The most frequently detected taxon in the Arctic Ocean was Pacific sand lance (Ammodytes hexapterus), followed by pricklebacks (Stichaeidae spp.) and polar cod (Boreogadus saida), which are circumpolar species.
Cluster analysis based on the Jaccard index indicated that the fish community in the northern part of the Chukchi Sea and Canada Basin was discriminated from that in the southern part of the Chukchi Sea and the Bering Sea. It was also found that the fish community in the former region was composed of two distinct clusters. The fish assemblages belonging to these clusters showed sporadic distribution and did not seemingly correspond to geographic location or environmental variables such as water temperature.
Vertical differences in fish assemblages among depths were also suggested in the Chukchi Sea shelf (approx. 50 m deep) and off the Barrow Canyon (approx. 120 m deep). The number of detected taxa was higher in the bottom water than in the surface water. Jaccard index showed that fish assemblages highly varied between depths.
This study demonstrated that eDNA is a promising tool to study the ecological impact of climate change on Arctic fishes. Integrating the results with oceanographic data in the future will provide novel information about the relationship between fish ecology and climate change. However, many technical issues remain to be solved, e.g., completeness of reference database, possible false-negative errors, and optimization of sampling effort. Nevertheless, the use of eDNA will surely prompt future studies to uncover the climate-induced changes in the Arctic ecosystem.