Habitat characteristics and energy budget of the ocean quahog (Arctica islandica)@en

We compared lifetime and population energy budgets of the extraordinary long-lived ocean quahog Arctica islandica from 6 different sites - the Norwegian coast, Kattegat, Kiel Bay, White Sea, German Bight, and off northeast Iceland - covering a temperature and salinity gradient of 4-10°C (annual mean) and 25-34, respectively. Based on von Bertalanffy growth models and size-mass relationships, we computed organic matter production of body (PSB) and of shell (PSS), whereas gonad production (PG) was estimated from the seasonal cycle in mass. Respiration (R) was computed by a model driven by body mass, temperature, and site. A. islandica populations differed distinctly in maximum life span (40 y in Kiel Bay to 197 y in Iceland), but less in growth performance (phi' ranged from 2.41 in the White Sea to 2.65 in Kattegat). Individual lifetime energy throughput, as approximated by assimilation, was highest in Iceland (43,730 kJ) and lowest in the White Sea (313 kJ). Net growth efficiency ranged between 0.251 and 0.348, whereas lifetime energy investment distinctly shifted from somatic to gonad production with increasing life span; PS/PG decreased from 0.362 (Kiel Bay, 40 y) to 0.031 (Iceland, 197 y). Population annual energy budgets were derived from individual budgets and estimates of population mortality rate (0.035/y in Iceland to 0.173/y in Kiel Bay). Relationships between budget ratios were similar on the population level, albeit with more emphasis on somatic production; PS/ PG ranged from 0.196 (Iceland) to 2.728 (White Sea), and P/B ranged from 0.203-0.285/y. Life span is the principal determinant of the relationship between budget parameters, whereas temperature affects net growth efficiency only. In the White Sea population, both growth performance and net growth efficiency of A. islandica were lowest. We presume that low temperature combined with low salinity represent a particularly stressful environment for this species.本研究对比了来自6个不同采样位点的超长寿命海洋圆蛤（Arctica islandica）的个体终生能量预算与种群能量预算，6个采样位点分别为挪威海岸、卡特加特海峡、基尔湾、白海、德国湾以及冰岛东北外海，涵盖的年平均温度梯度为4~10℃，盐度梯度为25~34。基于冯·贝塔朗菲生长模型（von Bertalanffy growth models）与体型-体重关系，本研究计算了个体体组织有机质生产（PSB）与壳体有机质生产（PSS），而性腺生产（PG）则通过体重的季节周期进行估算。呼吸代谢（R）通过由体重、温度及采样位点驱动的模型计算得到。该蛤类种群的最大寿命差异显著（基尔湾种群为40年，冰岛种群可达197年），但生长表现（phi'，取值范围为白海种群的2.41至卡特加特海峡种群的2.65）的差异相对较小。以同化量估算的个体终生能量通量，冰岛种群最高（43730千焦），白海种群最低（313千焦）。净生长效率介于0.251至0.348之间；随着寿命延长，终生能量投资从躯体生产显著转向性腺生产，PS/PG比值从基尔湾种群（40年寿命）的0.362降至冰岛种群（197年寿命）的0.031。种群年度能量预算由个体能量预算与种群死亡率估算值推导得到（冰岛种群死亡率为0.035/年，基尔湾种群为0.173/年）。种群水平上的能量预算比值关系与个体水平相似，但更侧重躯体生产；PS/PG比值范围为冰岛种群的0.196至白海种群的2.728，生产/生物量比值（P/B）范围为0.203~0.285/年。寿命是预算参数间关系的主要决定因素，而温度仅对净生长效率存在影响。白海种群的该蛤类生长性能与净生长效率均为最低。本研究推测，低温与低盐度的联合作用对该物种而言构成了极具胁迫性的生存环境。