Acidification and deoxygenation are two consequences of climate change that also co-occur in eutrophied coastal zones and can have deleterious effects on marine life. While the effects of hypoxia on marine herbivores have been well-studied, how ocean acidification combined with hypoxia affects herbivory is poorly understood. This study examined how herbivory and survival by the gastropod Lacuna vincta grazing on the macroalgae Ulva rigida was influenced by hypoxia and ocean acidification, alone and in combination, with and without food limitation. Experiments exposed L. vincta to a range of environmentally realistic dissolved oxygen (0.7 – 8 mg L–1) and pH (7.3 – 8.0 total scale) conditions for 3 – 72 h, with and without a starvation period and quantified herbivory and survival. While acidified conditions (pH < 7.4) reduced herbivory when combined with food limitation, low oxygen conditions (< 4 mg L–1) reduced herbivory and survival regardless of food supply. When L. vincta were starved and grazed in acidified conditions herbivory was additively reduced, whereas starvation and hypoxia synergistically reduced grazing rates. Overall, low oxygen had a more inhibitory effect on herbivory than low pH. Shorter exposure times (9, 6, and 3 h) were required to reduce grazing at lower DO levels (∼2.4, ∼1.6, and ∼0.7 mg L–1, respectively). Herbivory ceased entirely following a three-hour exposure to DO of 0.7 mg L–1 suggesting that episodes of diurnal hypoxia disrupt grazing by these gastropods. The suppression of herbivory in response to acidified and hypoxic conditions could create a positive feedback loop that promotes ‘green tides’ whereby reduced grazing facilitates the overgrowth of macroalgae that cause nocturnal acidification and hypoxia, further disrupting herbivory and promoting the growth of macroalgae. Such feedback loops could have broad implications for estuarine ecosystems where L. vincta is a dominant macroalgal grazer and will intensify as climate change accelerates.

中文翻译：

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缺氧和酸化，单独和组合，破坏草食性并减少腹足类动物的存活率，Lacuna vincta

酸化和脱氧是气候变化的两个后果，它们也同时发生在富营养化的沿海地区，并对海洋生物产生有害影响。虽然缺氧对海洋食草动物的影响已得到充分研究，但人们对海洋酸化与缺氧结合如何影响食草动物知之甚少。这项研究调查了在大型藻类石莼上放牧的腹足动物 Lacuna vincta 的食草性和存活率如何受到缺氧和海洋酸化的影响，无论是单独的还是组合的，有或没有食物限制。实验将 L. vincta 暴露于一系列环境现实的溶解氧（0.7 – 8 mg L–1）和 pH（7.3 – 8.0 总规模）条件下 3 – 72 小时，有或没有饥饿期，并量化食草和存活。在酸化条件下（pH < 7。4）与食物限制相结合时减少食草动物，低氧条件（< 4 mg L-1）无论食物供应如何都会减少食草动物和存活率。当 L. vincta 在酸化条件下挨饿和放牧时，食草性会增加，而饥饿和缺氧会协同降低放牧率。总体而言，与低 pH 值相比，低氧对食草动物的抑制作用更大。需要更短的暴露时间（9、6 和 3 小时）来减少在较低 DO 水平（分别为~2.4、~1.6 和~0.7 mg L-1）下的放牧。在暴露于 0.7 mg L-1 的 DO 3 小时后，食草动物完全停止，这表明昼夜缺氧会破坏这些腹足动物的放牧。在酸化和缺氧条件下抑制食草动物可以产生一个正反馈循环，促进“绿潮”，从而减少放牧促进大型藻类的过度生长，导致夜间酸化和缺氧，进一步破坏食草动物并促进大型藻类的生长。这种反馈回路可能对河口生态系统产生广泛影响，其中 L. vincta 是主要的大型藻类食草动物，并且会随着气候变化的加速而加剧。