Impact of marine aquaculture on the microbiome associated with nearby holobionts: the case of Patella caerulea living in proximity of sea bream aquaculture cages.

Aquaculture plays a major role in the coastal economy of the Mediterranean Sea. This raises the issue of the impact of fish cages on the surrounding environment. Here we explore the impact of aquaculture on the composition of the digestive gland microbiome of a representative locally dwelling wild holobionts, the grazer gastropod Patella caerulea, at an aquaculture facility located in Southern Sicily, Italy. The microbiome was assessed in individuals collected on sea bream aq-uaculture cages and on a rocky coastal tract located far from the cages, as control site. P. caerulea microbiome variations were explained in the broad marine metacommunity context, assessing the water and sediment microbiome composition at both sites, and characterizing the microbi-ome associated with the farmed sea bream. The P. caerulea digestive gland microbiome at the aquaculture site was characterized by a lower diversity, the loss of microorganisms sensitive to heavy metal contamination, and by the acquisition of fish pathogens and parasites. However, we also observed possible adaptive response of the P. caerulea digestive gland microbiome at the aquaculture site, including the acquisition of putative bacteria able to deal with metal and sul-phide accumulation, highlighting the inherent microbiome potential to drive the host acclimata-tion to stressful conditions.

水产养殖业在地中海沿岸经济中占据核心地位，这也引发了鱼类养殖网箱对周边环境影响的相关研究议题。本研究以意大利西西里南部一处水产养殖设施为研究地点，选取当地代表性野生共生体（holobiont）——植食性腹足类青螺（Patella caerulea）为研究对象，探究水产养殖活动对其消化腺微生物组（microbiome）组成的影响。研究分别采集养殖网箱周边及远离网箱的岩质海岸带（对照样地）的青螺个体，对其微生物组进行分析；同时在大尺度海洋元群落（metacommunity）框架下，检测两处样地的水体、沉积物微生物组组成，并对养殖海鲷的附属微生物组进行特征解析，以全面阐释青螺微生物组的变异规律。结果显示，养殖样地中青螺的消化腺微生物组呈现出多样性降低、对重金属污染敏感的微生物类群消失，以及获得鱼类病原体与寄生虫类群的特征。但本研究同时也观测到，养殖样地中青螺消化腺微生物组可能存在适应性响应：例如获得可耐受重金属与硫化物富集的潜在功能细菌类群，这凸显了微生物组的内在潜能可助力宿主应对胁迫环境。