Research press release


Nature Climate Change

Salmon face an acid test



今回、Michelle Ou、Colin Braunerたちは、カラフトマスの胚と稚魚をCO2濃度の現在値と将来予測値において10週間にわたって育ててから海水に移した。高濃度のCO2にさらされた孵化したてのカラフトマスとカラフトマスの稚魚の場合、淡水での成長期と海水への移動後のいずれの段階においても発育障害と代謝の変化が見られた。また、これらのカラフトマスは、警報合図を含む水中と目新しい物体の近くで過ごした時間が有意に多く、このことは、高濃度のCO2がカラフトマスの稚魚の不安を軽減する可能性を示唆している。この点と小さな体が相まって、カラフトマスの稚魚は捕食されやすくなっている可能性がある。


なお、同時に掲載されるNews & Views論文で、Philip Mundayは「[従って]カラフトマスの稚魚の成長と生存がCO2濃度上昇の影響を受けると、生態、経済、社会に影響が広く及ぶ可能性がある」と述べている。

Pink salmon may be at risk in the future from the effects of climate change-related acidification of their freshwater habitats, concludes a paper published online this week in Nature Climate Change. Ocean acidification, caused by rising levels of CO2, negatively affects marine species and is expected to cause widespread changes in saltwater ecosystems over coming decades. However, the potential impacts of acidification on freshwater ecosystems have attracted less attention.

Salmon start life in freshwater, but spend most of their juvenile and adult lives out at sea, before returning to the rivers and streams they were born in to spawn. Pink salmon are the most abundant salmon species in the northern Pacific and contribute to the productivity and function of coastal ecosystems. They are also of considerable cultural significance to the northern Pacific aboriginal communities that are supported by them.

Michelle Ou, Colin Brauner and colleagues reared pink salmon embryos and juveniles, for 10 weeks, at current and projected future CO2 levels and then transferred them to seawater. They found that hatchlings and juvenile pink salmon exposed to elevated CO2 levels exhibited reduced growth and altered metabolism, both during freshwater development and following seawater entry. They also found that these salmon spent significantly more time in water containing alarm cues and near a novel object, suggesting that elevated CO2 may reduce anxiety in pink salmon fry. This, combined with their smaller size, could make them more susceptible to predation.

The findings suggest that, unless populations can adapt, increases in CO2 in fresh water could detrimentally affect the ability of young pink salmon to migrate downstream, as well as their survival in the first part of the marine life stage.

In an accompanying News & Views, Philip Munday writes, “Any effects of elevated CO2 on the growth and survival of juvenile salmon could [therefore] have far-reaching ecological, economic and social consequences.”

doi: 10.1038/nclimate2694

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