2026-10-28 ワシントン大学（UW）
米国ワシントン大学の研究チームは、干潟に生息する巣穴掘りエビの生息域が、年間最大約30メートル移動することを明らかにした。調査は米国ワシントン州ウィラパ湾で3年間実施され、生息域の境界が時間とともにどの程度変化するかを定量的に示した初めての研究である。巣穴掘りエビは泥中の有機物を摂取し、細かな堆積物を排出するため、生息域の底質を変化させる。エビが移動した後の場所では、泥質化と底質の緻密化が進み、数年後には生態系の健全性を示すアマモが定着することが観察された。一方、水流によって泥が堆積しにくい場所では、このような環境改変作用は明瞭ではなかった。エビが移動する原因はまだ解明されていないが、生息域の変化と底質の特徴を把握することで、カキやハマグリの養殖被害を軽減する管理手法の開発につながると期待される。
The study’s lead author, Wesley Hull, who completed this research as a UW graduate student in biology, digs for oysters that were buried a foot down after a summer on a dense burrowing shrimp bed. Photo: Jennifer Ruesink
＜関連情報＞
- https://www.washington.edu/news/2026/10/28/october-research-highlights-cellular-organization-downsized-llms-migrant-fishers-and-burrowing-shrimp/
- https://www.sciencedirect.com/science/article/abs/pii/S0272771426005822
物理的条件は、河口域の生物攪拌生物によって形成される動的なパッチ境界の生態系への影響を媒介する Physical conditions mediate ecosystem effects of dynamic patch boundaries formed by an estuarine bioturbator
Wesley W. Hull,Brooke A. McIntyre,Nathaniel S. Lewis,C. Haleh Mawson,Kendall Valentine,Joseph N. Brockman,James Fitzpatrick,Jennifer L. Ruesink,Brett R. Dumbauld,Andrea S. Ogston
Estuarine, Coastal and Shelf Science Available online 25 September 2026
DOI:https://doi.org/10.1016/j.ecss.2026.110282
Highlights
- Without burrowing shrimp, sediment increased in organic and mud content.
- Physical gradients influenced sediment contrasts and the rate of boundary recession.
- Boundary shifts arose from shrimp movement and density dynamics, not mortality.
- Eelgrass rapidly colonized areas after shrimp retreated.
- Shrimp – environment interactions shape sediment and habitat transitions.
Abstract
Burrowing shrimp (Neotrypaea californiensis) are a dominant bioturbating species on tidal flats of eastern Pacific estuaries, where their local densities can exceed hundreds of individuals m−2. This study reports on rapid changes in the position of shrimp bed boundaries and the consequent change in ecosystem engineering. Six shrimp bed boundaries in Willapa Bay (Washington, USA) were selected for their easy delineation due to an abrupt shift from dense to nearly absent shrimp populations. During the three-year study, these boundaries shifted 9-34 m ᐧ yr−1, providing an opportunity to compare areas where shrimp were still present at high density with nearby areas with few remaining shrimp. As shrimp densities shifted from high to low due to this boundary retreat, sediment penetrability declined, and mud and organic content increased. Eelgrass (Zostera marina) appeared as seedlings within one year of shrimp retreat and began flowering after two years. Shrimp recruits occurred at equal density on both sides of shrimp bed boundaries, and adult shrimp transplanted outside of shrimp beds had equal persistence to inside, which suggests that boundaries shifted due to individual movement more than differential recruitment or mortality across boundaries. The engineering effects of shrimp depended on overlying physical conditions. Specifically, sediment differed more across the boundary at lower-elevation, turbid sites, consistent with shrimp activity mattering most where sediments would otherwise accumulate fines, while these muddier sediments were altered less by shrimp in terms of penetrability. This same environmental axis was related to the rate of boundary shift, with faster retreat at lower-elevation, turbid sites. Boundary shifts were mostly independent of season, except faster in summer at one site. Overall, the consequences of dynamic patch boundaries surrounding this major ecosystem engineer spanned sediment and species interactions, which were contingent on the physical context of estuarine tidal flats.
