Sediment geochemistry and water trace metal concentration in Potter Cove

Recent rapid climate warming at the western Antarctic Peninsula (WAP) results in elevated glacial melting, enhanced sedimentary run-off, increased turbidity and impact of ice-scouring in shallow coastal areas. Discharge of mineral suspension from volcanic bedrock ablation and chronic physical disturbance is expected to influence sessile filter feeders such as the Antarctic soft shell clam Laternula elliptica ( King and Broderip, 1832). We investigated effects of sedimentary run-off on the accumulation of trace metals, and together with physical disturbance, the cumulative effect on oxidative stress parameters in younger and older L. elliptica from two stations in Potter Cove (King George Island, Antarctica) which are distinctly impacted by turbidity and ice-scouring. Fe, Mn, Sr, V and Zn concentrations were slightly higher in sediments of the station receiving more sediment run-off, but not enriched in bivalves of this station. The only element that increased in bivalves experimentally exposed to sediment suspension for 28 days was Mn. Concentration of the waste accumulation biomarker lipofuscin in nervous tissue was higher in L. elliptica from the "exposed" compared to the "less exposed" site, whereas protein carbonyl levels in bivalve mantle tissue were higher at the less sediment impacted site. Tissue metal content and lipofuscin in nervous tissue were generally higher in older compared to younger individuals from both field stations. We conclude that elevated sediment ablation does not per se result in higher metal accumulation in L. elliptica. Instead of direct absorbance from sediment particles, metal accumulation in gills seems to indicate uptake of compounds dissolved in the water column, whereas metals in digestive gland appear to originate from enriched planktonic or detritic food. Accumulation of cellular waste products and potentially reactive metals over lifetime presumably alters L. elliptica physiological performance with age and may contribute to higher stress susceptibility in older animals.南极半岛西部（Western Antarctic Peninsula, WAP）近期的快速气候变暖，导致冰川消融加剧、沉积物径流增强、近岸浅水区浊度升高，同时冰蚀作用的影响范围扩大。火山基岩侵蚀与长期物理扰动所释放的矿物悬浮物，预计会对南极软壳蛤（Laternula elliptica, King & Broderip, 1832）这类固着滤食生物（sessile filter feeders）造成影响。 本研究针对南极乔治王岛波特湾（Potter Cove）的两个采样站位（二者浊度与冰蚀作用受干扰程度差异显著），探究了沉积物径流对痕量金属（trace metals）累积的影响，以及其与物理扰动共同作用下，对不同年龄（幼龄与老龄）南极软壳蛤氧化应激参数的累积效应。 沉积物径流更高的站位，其沉积物中的铁（Fe）、锰（Mn）、锶（Sr）、钒（V）与锌（Zn）浓度略高，但该站位的双壳类体内并未出现这些元素的富集现象。在为期28天的沉积物悬浮液暴露实验中，双壳类体内唯一出现浓度升高的元素为锰（Mn）。 相较于"受干扰较强"站位的个体，"受干扰较轻"站位的南极软壳蛤神经组织中，作为废物累积生物标志物的脂褐素（lipofuscin）浓度更高；而双壳类外套膜组织中的蛋白质羰基（protein carbonyl）水平，则在沉积物干扰较轻的站位更高。 两个野外采样站位的个体均表现出：老龄南极软壳蛤的组织金属含量与神经组织脂褐素水平，普遍高于幼龄个体。 本研究得出结论：沉积物侵蚀加剧本身并不会直接导致南极软壳蛤体内金属累积量升高。鳃组织中的金属累积并非源于对沉积物颗粒的直接吸收，而是指示了对水体中溶解态化合物的摄取；而消化腺中的金属则似乎源自富集了金属的浮游生物或碎屑食物。南极软壳蛤在其生命周期中累积的细胞代谢废物与潜在活性金属，可能会随年龄增长改变其生理机能，并可能加剧老龄个体的应激易感性。