Estuary & Ocean Science Center, Department of Biology, San Francisco State University, San Francisco, California, United States of America.
Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America.
PLoS One. 2020 Aug 31;15(8):e0238361. doi: 10.1371/journal.pone.0238361. eCollection 2020.
The San Francisco Bay outflow creates a tidally influenced low-salinity plume that affects adjacent coastal sites. In the study region, Anthopleura elegantissima (Cnidaria; Anthozoa) hosts a single symbiont, the dinoflagellate Breviolum muscatinei. Salinity, temperature, and aerial stress induce a bleaching response similar to corals where symbionts are expelled, causing further energetic stress. Using field observations of environmental conditions and symbiont abundance at sites on a gradient of exposure to estuarine outflow, along with a fully crossed multifactorial lab experiment, we tested for changes in symbiont abundance in response to various combinations of three stressors. Lab experiments were designed to mimic short term outflow events with low salinity, high temperature, and aerial exposure treatments. The lab aerial exposure treatment was a statistically significant factor in suppressing symbiont repopulation (ANOVA, p = .017). In the field, symbiont density decreased with increasing tidal height at the site closest to freshwater outflow (ANOVA, p = .007), suggesting that aerial exposure may affect symbiont density more than sea surface temperature and salinity. Unanticipated documentation of survival in 9 months of sand burial and subsequent repopulation of symbionts is reported as a six-month extension to past observations, exemplifying strong tolerance to environmental insult in this Cnidarian mutualism. The study of this symbiosis is useful in examining predicted changes in ocean conditions in tidepool communities and considering relative sources of stress.
旧金山湾的流出物形成了一个潮汐影响的低盐度羽流，影响了邻近的沿海地区。在研究区域，Anthopleura elegantissima（刺胞动物；珊瑚虫）宿主一种共生菌，即 Breviolum muscatinei 甲藻。盐度、温度和空气压力会引起类似于珊瑚的白化反应，共生菌被排出，导致进一步的能量压力。我们利用对暴露于河口流出物梯度的不同地点的环境条件和共生体丰度的野外观察，以及完全交叉的多因素实验室实验，测试了共生体丰度对三种胁迫因素的不同组合的变化。实验室实验旨在模拟短期流出事件，采用低盐度、高温和空气暴露处理。实验室空气暴露处理是抑制共生体再殖的一个统计学上显著的因素（方差分析，p =.017）。在野外，最接近淡水流出的地点的共生体密度随潮汐高度的增加而降低（方差分析，p =.007），这表明空气暴露可能比海面温度和盐度更能影响共生体密度。在过去观察的六个月延长时间内，我们意外地记录了共生体在九个月的沙埋中的存活和随后的再殖，这表明这种刺胞动物共生体对环境胁迫具有很强的耐受性。对这种共生关系的研究有助于研究潮汐池群落中海洋条件的预测变化，并考虑相对的胁迫源。
