Griffith School of Environment and Australian Rivers Institute-Coast & Estuaries, Nathan Campus, Griffith University, Brisbane, Queensland, Australia.
ARC Centre of Excellence for Coral Reef Studies, Townsville, Queensland, Australia.
PLoS One. 2017 Dec 5;12(12):e0189122. doi: 10.1371/journal.pone.0189122. eCollection 2017.
Reduced seawater pH and changes in carbonate chemistry associated with ocean acidification (OA) decrease the recruitment of crustose coralline algae (CCAcf.), an important coral-reef builder. However, it is unclear whether the observed decline in recruitment is driven by impairment of spore germination, or post-settlement processes (e.g. space competition). To address this, we conducted an experiment using a dominant CCA, Porolithon cf. onkodes to test the independent and combined effects of OA, warming, and irradiance on its germination success and early development. Elevated CO2 negatively affected several processes of spore germination, including formation of the germination disc, initial growth, and germling survival. The magnitude of these effects varied depending on the levels of temperature and irradiance. For example, the combination of high CO2 and high temperature reduced formation of the germination disc, but this effect was independent of irradiance levels, while spore abnormalities increased under high CO2 and high temperature particularly in combination with low irradiance intensity. This study demonstrates that spore germination of CCA is impacted by the independent and interactive effects of OA, increasing seawater temperature and irradiance intensity. For the first time, this provides a mechanism for how the sensitivity of critical early life history processes to global change may drive declines of adult populations of key marine calcifiers.
海水 pH 值降低和碳酸盐化学变化与海洋酸化（OA）有关，这会降低结壳珊瑚藻（CCAcf.）的繁殖，而结壳珊瑚藻是珊瑚礁的重要建造者。然而，目前尚不清楚观察到的繁殖减少是由于孢子萌发受损，还是由于定居后过程（例如空间竞争）所致。为了解决这个问题，我们使用一种优势 CCA，Porolithon cf. onkodes 进行了一项实验，以测试 OA、变暖以及光照对其萌发成功率和早期发育的独立和综合影响。高 CO2 对孢子萌发的几个过程产生负面影响，包括萌发盘的形成、初始生长和幼体存活。这些影响的大小取决于温度和光照水平。例如，高 CO2 和高温的组合降低了萌发盘的形成，但这种影响与光照水平无关，而在高 CO2 和高温下，特别是在与低光照强度结合时，孢子异常增加。本研究表明，CCA 的孢子萌发受到 OA、增加海水温度和光照强度的独立和交互影响。这首次为关键早期生活史过程对全球变化的敏感性如何可能导致关键海洋钙化生物成体种群减少提供了一种机制。
