Australian Research Council Centre of Excellence for Coral Reef Studies, School of Biological Sciences, University of Queensland, Brisbane, 4072, Australia.
Glob Chang Biol. 2013 Jan;19(1):291-302. doi: 10.1111/gcb.12035. Epub 2012 Oct 29.
The combination of global and local stressors is leading to a decline in coral reef health globally. In the case of eutrophication, increased concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) are largely attributed to local land use changes. From the global perspective, increased atmospheric CO2 levels are not only contributing to global warming but also ocean acidification (OA). Both eutrophication and OA have serious implications for calcium carbonate production and dissolution among calcifying organisms. In particular, benthic foraminifera precipitate the most soluble form of mineral calcium carbonate (high-Mg calcite), potentially making them more sensitive to dissolution. In this study, a manipulative orthogonal two-factor experiment was conducted to test the effects of dissolved inorganic nutrients and OA on the growth, respiration and photophysiology of the large photosymbiont-bearing benthic foraminifer, Marginopora rossi. This study found the growth rate of M. rossi was inhibited by the interaction of eutrophication and acidification. The relationship between M. rossi and its photosymbionts became destabilized due to the photosymbiont's release from nutrient limitation in the nitrate-enriched treatment, as shown by an increase in zooxanthellae cells per host surface area. Foraminifers from the OA treatments had an increased amount of Chl a per cell, suggesting a greater potential to harvest light energy, however, there was no net benefit to the foraminifer growth. Overall, this study demonstrates that the impacts of OA and eutrophication are dose dependent and interactive. This research indicates an OA threshold at pH 7.6, alone or in combination with eutrophication, will lead to a decline in M. rossi calcification. The decline in foraminifera calcification associated with pollution and OA will have broad ecological implications across their ubiquitous range and suggests that without mitigation it could have serious implications for the future of coral reefs.
全球和地方压力源的结合导致全球范围内珊瑚礁健康状况下降。就富营养化而言，溶解无机氮（DIN）和磷（DIP）浓度的增加主要归因于当地土地利用的变化。从全球角度来看，大气中二氧化碳水平的增加不仅导致全球变暖，还导致海洋酸化（OA）。富营养化和 OA 都对钙化生物的碳酸钙生产和溶解有严重影响。特别是，底栖有孔虫沉淀最易溶解的矿物碳酸钙形式（高镁方解石），这可能使它们对溶解更敏感。在这项研究中，进行了一个可操作的正交两因素实验，以测试溶解无机养分和 OA 对大型光合共生底栖有孔虫 Marginopora rossi 的生长、呼吸和光生理的影响。本研究发现，富营养化和酸化的相互作用抑制了 M. rossi 的生长速度。由于硝酸盐富集处理中营养限制的解除，有孔虫与其共生藻之间的关系变得不稳定，表现为每宿主表面积的共生藻细胞增加。来自 OA 处理的有孔虫每细胞的 Chl a 含量增加，表明其具有更大的获取光能的潜力，但对有孔虫的生长没有净益处。总的来说，这项研究表明，OA 和富营养化的影响是剂量依赖和相互作用的。该研究表明，在 pH7.6 下，OA 单独或与富营养化结合，将导致 M. rossi 钙化减少。与污染和 OA 相关的有孔虫钙化减少将对其广泛分布的生态系统产生广泛影响，并表明如果不加以缓解，这可能对珊瑚礁的未来产生严重影响。
