Oyster production in Brazil has been highlighted as an important economic activity and is directly impacted by the quality of the environment, which is largely the result of human interference and climate change. Harmful algal blooms occur in aquatic ecosystems worldwide, including coastal marine environments which have been increasing over the last decades as a result of global change and anthropogenic activities. In this study, the native oysters Crassostrea gasar from Northeast of Brazil were exposed to two toxic benthic dinoflagellate species, Prorocentrum lima and Ostreopsis cf. ovata. Their respective effects on C. gasar physiology and defense mechanisms were investigated. Oyster hemocytes were first exposed in vitro to different concentrations of both dinoflagellate species to assess their effects on hemocyte functions, such as phagocytosis, production of reactive oxygen species, as well as mortality. Results highlighted an alteration of hemocyte phagocytosis and viability in presence of O. cf. ovata, whereas P. lima did not affect the measured hemocyte functions. In a second experiment, oysters were exposed for 4 days in vivo to toxic culture of O. cf. ovata to assess its effects on hemocyte parameters, tissues damages and pathogenic Perkinsus spp. infection. An increase in hemocyte mortality was also observed in vivo, associated with a decrease of ROS production. Histopathological analyses demonstrated a thinning of the epithelium of the digestive tubules of the digestive gland, inflammatory reaction and a significant increase in the level of infection by Perkinsus spp. in oysters exposed to O. cf. ovata. These results indicate that oysters C. gasar seem to be pretty resilient to an exposure to P. lima and may be more susceptible to O. cf. ovata. Furthermore, the latter clearly impaired oyster physiology and defense mechanisms, thus highlighting that harmful algal blooms of O. cf. ovata could potentially lead to increased susceptibility of C. gasar oysters to parasite infections.

巴西的牡蛎生产已被强调为一项重要的经济活动，并直接受到环境质量的影响，这主要是人为干预和气候变化的结果。在全球范围内，包括沿海海洋环境在内的水生生态系统中都会发生有害的藻华，近几十年来，由于全球变化和人为活动，这种环境一直在增加。在这项研究中，原生牡蛎牡蛎GASAR来自巴西东北暴露于两种有毒底栖甲藻种，利马原甲藻和Ostreopsis比照 卵子。它们分别对加索尔梭菌的影响生理和防御机制进行了调查。首先将牡蛎血细胞体外暴露于不同浓度的两种鞭毛藻物种，以评估其对血细胞功能（如吞噬作用，活性氧的产生以及死亡率）的影响。结果强调了在O的存在下血细胞吞噬作用和生存能力的改变。cf. 卵形，而利马体育不影响测得的血细胞功能。在第二个实验，牡蛎暴露4天在体内的有毒培养O.比照 卵形，以评估其对血细胞参数，组织损害和致病效果帕金spp。感染。在体内还观察到血细胞死亡率的增加，这与ROS产生的减少有关。组织病理学分析显示消化腺的消化管上皮变薄，发炎反应以及珀金斯氏菌感染水平显着增加。在暴露于O的牡蛎中。cf. 卵子。这些结果表明，牡蛎C.gasar似乎对暴露于利马毕赤酵母具有相当的抵抗力，并且可能更易受O. cf.的侵害。卵形。此外，后者明显损害了牡蛎的生理和防御机制，从而突显了O. cf.的有害藻华。卵形可能会导致增加易感性C. GASAR牡蛎寄生虫感染。