Research press release


Scientific Reports

Environment: Plastic pollution may pose greater risk to younger turtles


今回、Britta Denise Hardestyたちの研究グループは、ウミガメの剖検246例と座礁データベースに登録された剖検記録706件のデータを調べた。その結果、幼若個体は成体よりもプラスチック摂取量が多いこと、そして消化管に残存するプラスチックの量は死因によって異なることが明らかになった。プラスチック摂取量は、死因不明の場合が最も少なく、死因がプラスチック関連でなかった場合(船との衝突、溺死など)がそれに次いで少なかった。一方、プラスチック摂取量が最多だったのは、プラスチック摂取が死因の場合だった。246の剖検例のうち、体内にプラスチックが見つかったのは幼若個体で23%、孵化個体で54%であるのに対し、亜成体では15%、成体では16%だった。また、体内に見つかったプラスチックの数量は1~329個と幅があり、重量は最大10.41グラムだった。以上の知見から、採餌場所と生活史の段階がウミガメの死亡リスクに影響を及ぼす可能性が示唆される。若齢個体は海流に乗って海を漂い、沿岸海域の海面に近い所で餌を得る傾向があり、そうした場所の方が、ウミガメの消化管に蓄積したり消化管穿孔を引き起こしたりする恐れのあるプラスチック製品で汚染されている可能性が高いのだ。


Younger sea turtles (juvenile and post-hatchling) are at a greater risk of dying from plastic ingestion than adult turtles, according to a study in Scientific Reports.

Britta Denise Hardesty and colleagues examined data from 246 sea turtle necropsies and 706 necropsy records from a stranding database. They found that juvenile turtles had ingested larger quantities of plastic than adults and that the amount of plastic in the turtles’ digestive tracts varied depending on their cause of death; turtles that had died from unknown causes had ingested the smallest amounts of plastic, followed by those that died from non-plastic related causes (such as boat strikes and drowning) while those that died from plastic ingestion had ingested the highest amounts. 23% of juvenile and 54% of post-hatchling turtles died of plastic ingestion had ingested plastic, compared to 15% of sub-adult and 16% of adult turtles. The count and mass of plastic ingested ranged from one to 329 pieces and weighed up to 10.41g. The findings suggest that feeding location and life history stage may impact the turtles’ risk of dying; younger turtles tend to feed in coastal waters drift with currents and feed in offshore waters closer to the surface, which are more likely to be contaminated with large plastic items that can accumulate in the animals’ digestive tracts, or cause perforation.

The authors found that the best way of modelling of the relationship between the amounts of plastic a turtle ingested and its risk of death took into account the number of plastic items in relation to the length of the turtle’s shell and its age. Their model represents a first step in quantifying the risk that plastic pollution poses to the world’s declining sea turtle populations, especially in coastal surface waters.

doi: 10.1038/s41598-018-30038-z


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