Seawater carbonate chemistry and herbivory of gastropod Lacuna vincta

While ocean acidification has different effects on herbivores and autotrophs, how acidification may influence herbivory is poorly understood. This study examined how grazing by the gastropod Lacuna vincta (hereafter Lacuna) on the macroalgae Ulva spp. (hereafter Ulva) is influenced by ocean acidification. Herbivory by Lacuna was significantly reduced under elevated partial pressure of carbon dioxide ( pCO2; 1500-2000 µatm) relative to ambient pCO2 (400 µatm). This significant decrease in herbivory was unrelated to the physiological status of Ulva but rather was specifically elicited when Lacuna was exposed to elevated pCO2 in the absence of food for 18 to 24 h prior to grazing Ulva. The negative effects of elevated pCO2 on Lacuna were absent at 400 to 800 µatm pCO2 or when fed but persisted for up to 72 h following a 24 h exposure to elevated pCO2 without food. Depressed respiration rates in Lacuna following exposure to high pCO2 without food indicated these conditions produced metabolic suppression potentially associated with acidosis. Collectively, the lasting (72 h) nature of grazing inhibition of Lacuna following brief exposure (18 h) to moderate pCO2 levels (>1500 µatm) when food was not available suggests this process could have broad effects on the dynamics of macroalgae in estuaries where Lacuna is a dominant grazer; these effects will be amplified as climate change progresses.

尽管海洋酸化对草食动物和自养生物的影响存在差异，但酸化如何作用于植食行为的机制尚不明确。本研究探讨了海洋酸化对腹足类动物Lacuna vincta（以下简称Lacuna）取食大型藻类Ulva spp.（以下简称Ulva）行为的影响。与环境二氧化碳分压（pCO₂；400 µatm）相比，在升高的二氧化碳分压（1500-2000 µatm）条件下，Lacuna的植食行为显著减少。这种植食行为的显著下降与Ulva的生理状态无关，而是在Lacuna于取食Ulva前，在无食物条件下暴露于升高的pCO₂环境18至24小时时被特异性引发。在400至800 µatm pCO₂条件下或Lacuna获得食物时，升高pCO₂的负面影响消失；但在无食物条件下暴露于升高pCO₂环境24小时后，该负面影响可持续长达72小时。综上，当食物缺乏时，Lacuna短暂暴露（18小时）于中等pCO₂水平（>1500 µatm）后，其取食抑制效应可持续72小时；这表明该过程可能对Lacuna作为优势食草动物的河口区域大型藻类动态产生广泛影响，且这些影响将随气候变化加剧而进一步放大。