Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave., Charlottetown, Prince Edward Island, C1A 4P3, Canada.
Institute of Marine and Environmental Technology, University of Maryland Baltimore County, 701 E Pratt St., Baltimore, Maryland, 21202, USA.
Ecology. 2018 Aug;99(8):1802-1814. doi: 10.1002/ecy.2393. Epub 2018 Jul 2.
Climate change is affecting the health and physiology of marine organisms and altering species interactions. Ocean acidification (OA) threatens calcifying organisms such as the Pacific oyster, Crassostrea gigas. In contrast, seagrasses, such as the eelgrass Zostera marina, can benefit from the increase in available carbon for photosynthesis found at a lower seawater pH. Seagrasses can remove dissolved inorganic carbon from OA environments, creating local daytime pH refugia. Pacific oysters may improve the health of eelgrass by filtering out pathogens such as Labyrinthula zosterae (LZ), which causes eelgrass wasting disease (EWD). We examined how co-culture of eelgrass ramets and juvenile oysters affected the health and growth of eelgrass and the mass of oysters under different pCO exposures. In Phase I, each species was cultured alone or in co-culture at 12°C across ambient, medium, and high pCO conditions, (656, 1,158 and 1,606 μatm pCO , respectively). Under high pCO , eelgrass grew faster and had less severe EWD (contracted in the field prior to the experiment). Co-culture with oysters also reduced the severity of EWD. While the presence of eelgrass decreased daytime pCO , this reduction was not substantial enough to ameliorate the negative impact of high pCO on oyster mass. In Phase II, eelgrass alone or oysters and eelgrass in co-culture were held at 15°C under ambient and high pCO conditions, (488 and 2,013 μatm pCO , respectively). Half of the replicates were challenged with cultured LZ. Concentrations of defensive compounds in eelgrass (total phenolics and tannins), were altered by LZ exposure and pCO treatments. Greater pathogen loads and increased EWD severity were detected in LZ exposed eelgrass ramets; EWD severity was reduced at high relative to low pCO . Oyster presence did not influence pathogen load or EWD severity; high LZ concentrations in experimental treatments may have masked the effect of this treatment. Collectively, these results indicate that, when exposed to natural concentrations of LZ under high pCO conditions, eelgrass can benefit from co-culture with oysters. Further experimentation is necessary to quantify how oysters may benefit from co-culture with eelgrass, examine these interactions in the field and quantify context-dependency.
气候变化正在影响海洋生物的健康和生理机能，并改变物种间的相互作用。海洋酸化（OA）威胁着太平洋牡蛎等钙化生物。相比之下，海草，如鳗草，Zostera marina，可以从较低海水 pH 值下光合作用可用的碳增加中受益。海草可以从 OA 环境中去除溶解的无机碳，形成当地白天的 pH 避难所。太平洋牡蛎可以通过过滤掉病原体 Labyrinthula zosterae（LZ）来改善鳗草的健康，LZ 会导致鳗草浪费病（EWD）。我们研究了鳗草幼体和幼年牡蛎的共培养如何影响鳗草的健康和生长，以及在不同 pCO 暴露下牡蛎的质量。在第一阶段，在 12°C 下，每个物种单独或共培养，分别在环境、中等和高 pCO 条件下（分别为 656、1,158 和 1,606 μatm pCO ）。在高 pCO 下，鳗草生长更快，EWD 更严重（在实验前的野外收缩）。与牡蛎共培养也降低了 EWD 的严重程度。虽然鳗草的存在降低了白天的 pCO，但这种降低不足以缓解高 pCO 对牡蛎质量的负面影响。在第二阶段，在环境和高 pCO 条件下（分别为 488 和 2,013 μatm pCO ），将单独的鳗草或牡蛎和鳗草共培养在 15°C 下。一半的复制品受到培养的 LZ 的挑战。鳗草（总酚和单宁）中的防御化合物浓度受到 LZ 暴露和 pCO 处理的影响。在 LZ 暴露的鳗草枝条中检测到更高的病原体负荷和更严重的 EWD 严重程度；在高 pCO 下，EWD 严重程度降低。牡蛎的存在并不影响病原体负荷或 EWD 严重程度；实验处理中高浓度的 LZ 可能掩盖了这种处理的效果。总的来说，这些结果表明，当鳗草在高 pCO 条件下暴露于自然浓度的 LZ 时，它可以从与牡蛎的共培养中受益。还需要进一步的实验来量化牡蛎如何从与鳗草的共培养中受益，在野外检验这些相互作用，并量化上下文相关性。
