Abstract Pteropods (pelagic snails) are abundant zooplankton in the Southern Ocean where they are important grazers of phytoplankton, prey for higher trophic levels, and sensitive to environmental change. The Western Antarctic Peninsula (WAP) is a highly dynamic and productive region that has undergone rapid warming, but little is known about how environmental changes there will affect pteropod physiology. In this study, the effects of warming seawater temperatures and shifting food availability on Limacina helicina antarctica metabolism (respiration and excretion) were determined by conducting shipboard experiments that exposed pteropods to a range of temperatures and phytoplankton (food) concentrations. Highest respiration (up to 69 μmol O2 gDW−1 h−1) and usually highest excretion rates occurred under higher temperature with more limited metabolic response to food concentration, indicating these factors do not always have an additive effect on pteropod metabolism. The proportion of dissolved organic matter (DOM) to total organic and inorganic dissolved constituents was high and was also significantly affected by shifts in temperature and food. Dissolved organic carbon, nitrogen, and phosphorus (DOC, DON, and DOP) were on average 27, 51, and 11.5% of the total C, N, and P metabolized, respectively. The proportion of total N excreted as DON and the proportion of total P excreted as DOP were significantly affected by a combination of shifting temperature and food concentrations. There were no effects of temperature or food on DOC excretion (mean 8.79 μmol C gDW−1 h−1; range 0.44 to 44) as a proportion of total C metabolized. Metabolic O2:N ratio ranged from 2 to 9 and decreased significantly with increasing temperature and food, indicating a shift toward increased protein catabolism. Metabolic ratios of C, N, and P were all below the canonical Redfield ratio, which has implications for phytoplankton nutrient uptake and bacterial production. Respiration rates at ambient conditions of other WAP pteropods, and excretion rates for Clio pyramidata, were also measured, with respiration rates ranging from 24.39 (Spongiobranchaea australis) to 28.86 (L. h. antarctica) μmol O2 gDW−1 h−1. Finally, a CO2 perturbation experiment measuring L. h. antarctica metabolism under pre-industrial and elevated dissolved pCO2 conditions showed no significant change in mean L. h. antarctica respiration or excretion rates with higher pCO2. These insights into the metabolic response of pteropods to ocean variability increase our understanding of the role of zooplankton in biogeochemical cycles and help predict future responses to climate change.

中文翻译：

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温度和食物浓度对南极半岛西部翼足类代谢的影响

摘要 翼足类（远洋蜗牛）是南大洋丰富的浮游动物，它们是浮游植物的重要食草动物，捕食较高营养级，对环境变化敏感。南极半岛西部 (WAP) 是一个充满活力和生产力的地区，经历了快速变暖，但人们对那里的环境变化将如何影响翼足类生理学知之甚少。在这项研究中，海水温度升高和食物供应变化对 Limacina helicina antarctica 代谢（呼吸和排泄）的影​​响是通过将翼足类动物暴露于一系列温度和浮游植物（食物）浓度的船上实验来确定的。最高呼吸（高达 69 μmol O2 gDW-1 h-1）和通常最高排泄率发生在较高温度下，对食物浓度的代谢反应更有限，表明这些因素并不总是对翼足类代谢产生累加效应。溶解有机物 (DOM) 占总有机和无机溶解成分的比例很高，并且还受到温度和食物变化的显着影响。溶解的有机碳、氮和磷（DOC、DON 和 DOP）分别平均占总 C、N 和 P 代谢的 27%、51% 和 11.5%。以 DON 形式排出的总 N 的比例和以 DOP 形式排出的总 P 的比例受温度变化和食物浓度组合的显着影响。温度或食物对 DOC 排泄没有影响（平均 8. 79 μmol C gDW-1 h-1；范围 0.44 到 44) 作为总 C 代谢的比例。代谢 O2:N 比率范围为 2 到 9，并且随着温度和食物的增加而显着降低，表明蛋白质分解代谢增加。C、N 和 P 的代谢比率都低于规范的 Redfield 比率，这对浮游植物营养吸收和细菌产生有影响。还测量了其他 WAP 翼足类动物在环境条件下的呼吸速率和锥体 Clio 的排泄速率，呼吸速率范围从 24.39（Spongiobranchaea australis）到 28.86（L. h. antarctica）μmol O2 gDW−1 h−1。最后，测量 L. h. 的 CO2 扰动实验。工业化前和溶解 pCO2 升高条件下的南极代谢显示平均 L. h. 没有显着变化。南极洲呼吸或排泄率较高，pCO2 较高。这些关于翼足类动物对海洋变化的代谢反应的见解增加了我们对浮游动物在生物地球化学循环中的作用的理解，并有助于预测未来对气候变化的反应。