Chondrilla nucula respiration and clearance rates to changing temperature

As a result of climate change, the Mediterranean Sea has been exposed to an increase in frequency and intensity of marine heat waves in the last decades, some of which caused mass mortality events of benthic invertebrates, including sponges. Sponges are an important component of benthic eco-systems and can be the dominant group in some rocky shallow-water areas in the Mediterranean Sea. In this study, we exposed the common shallow-water Mediterranean sponge Chondrilla nucula (Demospongiae: Chondrillidae) to six different temperatures for 24 h, ranging from temperatures experienced in the field during the year (15, 19, 22, 26, 28 °C) and above normal temperatures (32 °C) and metabolic traits (respiration and rate) and behavioural (clearance rate) were measured. Both respiration and clearance rates were affected by temperature. Respiration rates increased at higher temperatures but were similar between 26 and 32 °C treatments. Clearance rates decreased at temperatures > 26 °C, indicating a drop in food intake that was not reflected by respiration rates. This decline in feeding, while maintaining high respiration rates, may indicate a negative energy balance that could affect this species under chronic or repeated thermal stress exposure. C. nucula will probably be a vulnerable species under climate change conditions, affecting its metabolic per-formance, ecological functioning and the ecosystem services it provides.近数十年来，受气候变化影响，地中海海域海洋热浪的发生频率与强度均呈上升趋势，其中部分热浪已引发包括海绵动物在内的底栖无脊椎动物（benthic invertebrates）大规模死亡事件。海绵动物是底栖生态系统的重要组成类群，在地中海部分岩质浅水区可成为优势类群。本研究以地中海常见浅海海绵假色海绵（Chondrilla nucula，隶属于寻常海绵纲（Demospongiae）：软海绵科（Chondrillidae））为实验对象，设置6个温度梯度（涵盖该海域年度实测水温：15、19、22、26、28 ℃，以及超出正常水温的32 ℃）开展24小时暴露实验，并测定其代谢指标（呼吸速率）与行为指标（滤食率）。温度对该海绵的呼吸速率与滤食率均存在显著影响：呼吸速率随温度升高呈上升趋势，但26 ℃与32 ℃处理组间无显著差异；当水温超过26 ℃时，滤食率显著下降，表明其摄食水平出现降低，而这一变化并未在呼吸速率中体现。在维持较高呼吸速率的同时出现摄食能力下降，可能意味着该物种处于能量负平衡状态，若长期或反复暴露于热胁迫环境下，其生存将受到负面影响。假色海绵（C. nucula）在气候变化背景下或成为易受害物种，其代谢性能、生态功能及所提供的生态系统服务均将受到影响。