Data from: Oyster aquaculture impacts Zostera marina epibiont community composition in Akkeshi-ko estuary, Japan

Coastal fisheries are in decline worldwide, and aquaculture has become an increasingly popular way to meet seafood demand. While finfish aquaculture can have substantial adverse effects on coastal ecosystems due mostly to necessary feed inputs, bivalves graze on natural phytoplankton and are often considered for their positive ecosystem services. We conducted two independent studies to investigate the effects of long-line Crassostrea gigas oyster aquaculture on Zostera marina seagrass beds and associated epibiont communities in Akkeshi-ko estuary, Japan. Results from both studies yielded no evidence of an effect of oyster aquaculture on the morphology, density, or biomass of Z. marina, but significant differences were apparent in the epibiont community. Reference seagrass beds located away from aquaculture had higher seagrass epiphyte loads and higher abundances of amphipods. Conversely, seagrass beds below aquaculture lines had higher sessile polychaete biomass and higher isopod abundances. Our results suggest that the presence of oyster aquaculture may have indirect effects on seagrass by changing epibiont community composition and relative abundances of species. One proposed mechanism is that cultured oysters feed on epiphytic diatoms and epiphyte propagules before they can settle on the seagrass, which reduces epiphyte loads and influences subsequent faunal settlement. If carefully implemented and monitored, long-line oyster aquaculture may be a sustainable option to consider as bivalve aquaculture expands to meet global seafood demand, but further work is needed to fully assess and generalize the community-level effects on seagrass epibionts.

全球近海渔业资源持续衰退，水产养殖（aquaculture）已成为满足全球海产品需求的日益主流的途径。然而，有鳍鱼类水产养殖（finfish aquaculture）常因必需的饲料投入，对近海生态系统造成显著不利影响；而双壳类（bivalves）以天然浮游植物（phytoplankton）为食，常因其提供的正向生态系统服务（ecosystem services）受到广泛关注。本研究开展两项独立实验，以探究日本厚岸河口（Akkeshi-ko estuary）内延绳式（long-line）养殖太平洋牡蛎（Crassostrea gigas）对大叶藻（Zostera marina）海草床及其附生生物群落（epibiont communities）的影响。两项研究结果均未发现牡蛎养殖对大叶藻的形态、密度或生物量产生影响的证据，但附生生物群落却呈现出显著差异。远离养殖区域的对照海草床，其海草附生生物负载量及端足类（amphipods）丰度更高；与之相反，位于养殖延绳下方的海草床，其固着多毛类（sessile polychaete）生物量及等足类（isopods）丰度更高。本研究结果表明，牡蛎养殖的存在可能通过改变附生生物群落组成及物种相对丰度，对海草产生间接影响。其中一种已提出的作用机制为：养殖牡蛎可在附生硅藻（epiphytic diatoms）及附生生物繁殖体（epiphyte propagules）定居海草之前将其取食，从而降低附生生物负载量，并影响后续的动物定居过程。若能谨慎实施并开展有效监测，延绳式牡蛎养殖或可作为一种可持续选项，在双壳类水产养殖扩张以满足全球海产品需求的背景下加以考量，但仍需开展更多研究以全面评估并推广其对海草附生生物的群落级影响。