Lithogenic and biogenic particle deposition in an Antarctic coastal environment (Marian Cove, King George Island): Seasonal patterns from a sediment trap study

摘要

Particulate suspended material was recovered over a 23-month period using two sediment traps deployed in shallow water (～30 m deep) off the King Sejong Station located in Marian Cove of King George Island, West Antarctica. Variability in seasonal flux and geochemical characteristics of the sediment particles highlights seasonal patterns of sedimentation of both lithogenic (terrigenous) and biogenic particles in the coastal glaciomarine environment. All components including total mass flux, lithogenic particle flux and biogenic particle flux show distinct seasonal variation, with high recovery rates during the summer and low rates under winter fast ice. The major contributor to total mass flux is the lithogenic component, comprising from 88% during the summer months (about 21 g m~(-2) d~(-1)) up to 97% during the winter season (about 2 g m~(-2) d~(-1)). The lithogenic particle flux depends mainly on the amount of snow-melt (snow accumulation) delivered into the coastal region as well as on the resuspension of sedimentary materials. These fine-grained lithogenic particles are silt-to-clay sized, composed mostly of clay minerals weathered on King George Island. Biogenic particle flux is also seasonal. Winter flux is ～0.2 g m~(-2)d~(-1), whereas the summer contribution increases more than tenfold, up to 2.6 g m~(-2) d~(-1). Different biogenic flux between the two summers indicates inter-annual variability to the spring—summer phytoplankton bloom. The maximum of lithogenic particle flux occurs over a short period of time, and follows the peak of biogenic particle flux, which lasts longer. The seasonal warming and sea-ice retreat result in change in seawater nutrient status and subsequent ice-edge phytoplankton production. Meanwhile, the meltwater input to Marian Cove from the coastal drainage in January to February plays a major role in transporting lithogenic particles into the shallow water environment, although the tidal currents may be the main agents of resuspension in this kind of sheltered bay.