Nekton community composition and habitat use of an invasive seagrass and its native congener in Pacific Northwest USA estuaries

Authors: SUND, DANIEL - Oregon State University; Dumbauld, Brett; HEIDMANN, SARAH - University Of Virgin Islands, St Croix

Submitted to: Estuaries and Coasts - Journal of the Estuarine Research Federation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Introduction of non-native species that become invasive often results in fundamental changes to the structure and function of the invaded environment. On the US west coast, the introduced seagrass Zostera japonica is rapidly expanding. Studies have shown that benthic infaunal and epifaunal communities in Z. japonica are very different than those found in what was a typically open mudflat before it invaded. This new community is more similar to that found in areas where the native seagrass, Zostera marina is present. Seagrasses are viewed as valuable components of these estuarine systems because they serve as nursery areas for fish and crab, but the community of these larger animals that utilize the invaded area that Zostera japonica has invaded has been little investigated. The goal of this study was to inform Z japonica management including that for shellfish aquaculture by comparing the nekton community in Z. japonica to that in the native seagrass Z. marina via deployment of underwater action cameras. Thirteen species were observed in video footage of seagrass beds in both estuaries with transiting and foraging behaviors most common. Dungeness crab wwere more frequently observed in native seagrass in both estuaries while staghorn sculpin were more abundant in native seagrass in Yaquina Bay and no difference was observed in Willapa Bay. Shiner perch (Cymatogaster aggregata) were more frequently observed in seagrass than open mudflat where Z. japonica had been removed in Willapa Bay, but observed equally in both seagrasses in both estuaries, while juvenile starry flounder (Platicthys stellatus) were more abundant in treated open habitat. Overall community composition differed moderately between the two seagrasses in Yaquina Bay, but not in Willapa Bay, suggesting that both seagrasses provide structure and that the distribution and proximity of Z. japonica to Z. marina may drive these differences in community composition between estuaries.

Technical Abstract: Introduction of non-native species often results in fundamental changes in the structure and function of invaded environments. On the US west coast, the introduced seagrass Zostera japonica is rapidly expanding. Seagrasses are viewed as valuable components of these estuarine systems at least in part because they serve as nursery areas for fish and crab, but the nekton community utilizing Z. japonica has been little investigated. The goal of this study was to inform Z japonica management including that for shellfish aquaculture by comparing the nekton community in Z. japonica to that in the native seagrass Z. marina via deployment of underwater action cameras. Thirteen species were observed in video footage of seagrass beds in both estuaries with transiting and foraging behaviors most common. Adjusted catch per unit effort (CPUE) for one of the most abundant species Metacarcinus magister (Dungeness crab) was higher in native Z. marina in both estuaries while staghorn sculpins (Leptocottus armatus) were only more abundant in Z. marina in Yaquina Bay. Shiner perch (Cymatogaster aggregata) were more frequently observed in seagrass than open mudflat where Z. japonica had been removed in Willapa Bay, but observed equally in both seagrasses in both estuaries while juvenile starry flounder (Platicthys stellatus) were more abundant in treated open habitat. Overall community composition differed moderately between the two seagrasses in Yaquina Bay, but not in Willapa Bay, suggesting that both seagrasses provide structure but the distribution of Z. japonica and its proximity to Z. marina may drive differences in community composition between estuaries.