Abstract The surface of the ocean has absorbed one-third of the CO2gas that has been released by anthropogenic activities, which has resulted in a reduction in pH and the aragonite saturation state (Ωara) with potential negative impacts in calcifying organisms, such as corals. To evaluate these effects, the natural variability present must first be understood, including that of processes that operate at diurnal, seasonal, and interannual frequencies. The objective of this study was to determine the influence of physical and biogeochemical processes on the seasonal variability of the CO2-system in a fringe coral reef of the Eastern Tropical Pacific (ETP). To achieve this, a SeapHOx sensor was installed to measure temperature, salinity, dissolved oxygen, and pHTot at 30-min intervals from November 2013 (early winter) to July 2014 (early summer). The recorded temperature and salinity data fed a mixing model to identify the water masses present in the reef. We show how physical and biogeochemical oceanic processes influence and control the variability of the carbonate system. The presence of water masses with different carbon chemistries responded to two scenarios: (1) seasonal circulation on the order of months and (2) an intermittence between water masses related to mesoscale structures (eddies) on the order of weeks. A low-pH and Ωara condition was detected during summer, which was related to the presence of warm and respired Tropical Surface Water. The broadest changes in Ωara were the result of physical processes (winter ΔΩara = 0.14 and summer ΔΩara = 0.34 units) and corresponded to the transition between water masses with different carbon-biogeochemistry signals. Our results suggest that the Cabo Pulmo coral community develops in an environment with a wide range of pH and Ωara conditions and that seasonal changes are controlled by open ocean carbon biogeochemistry.

中文翻译：

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墨西哥加利福尼亚湾边缘珊瑚礁碳生物地球化学的季节性控制

摘要 海洋表面吸收了人类活动释放的二氧化碳气体的三分之一，这导致 pH 值和文石饱和状态 (Ωara) 降低，对珊瑚等钙化生物产生潜在的负面影响。要评估这些影响，必须首先了解存在的自然变率，包括以昼夜、季节性和年际频率运行的过程的变率。本研究的目的是确定物理和生物地球化学过程对东热带太平洋 (ETP) 边缘珊瑚礁 CO2 系统季节性变化的影响。为了实现这一目标，安装了一个 SeapHOx 传感器，以从 2013 年 11 月（初冬）到 2014 年 7 月（初夏）以 30 分钟的间隔测量温度、盐度、溶解氧和 pHTot。记录的温度和盐度数据提供了一个混合模型，以识别珊瑚礁中存在的水团。我们展示了物理和生物地球化学海洋过程如何影响和控制碳酸盐系统的可变性。具有不同碳化学成分的水团的存在对两种情况作出反应：（1）以月为单位的季节性循环；（2）与中尺度结构（涡流）相关的水团之间的间歇期为数周。在夏季检测到低 pH 值和 Ωara 条件，这与温暖和呼吸的热带地表水的存在有关。Ωara 的最广泛变化是物理过程的结果（冬季 ΔΩara = 0.14 和夏季 ΔΩara = 0.34 个单位），对应于具有不同碳-生物地球化学信号的水团之间的转变。