Biogenic opal, carbonate fluxes, time series

Analyses of samples from a 14-year series of sediment-trap deployments in the deep Sargasso Sea reveal a significant trend in the ratio of the sinking fluxes of biogenic calcium carbonate and silica. Although there are pronounced seasonal cycles for both flux components, the overall opal/CaCO3 ratio changed by 50% from 1978 to 1991 (largely due to a decrease of opal flux), while total flux had no significant trend. These results suggest that plankton communities respond rapidly to subtle climate change, such as is evident in regional variations of wind speed, precipitation, wintertime ventilation and midwater temperatures. If the trends we observe in the makeup of sinking particulate matter occur on a large scale, they may in turn modify climate by modulating ocean-atmosphere CO2 exchange and albedo over the ocean.

对马尾藻海深海开展的为期14年的系列沉积物捕获器（sediment-trap）布放所获样品的分析，揭示了生源碳酸钙（biogenic calcium carbonate）与硅质（silica）沉降通量（sinking flux）比值的显著变化趋势。尽管两类通量组分均存在显著的季节循环，但1978年至1991年间，整体蛋白石（opal）/碳酸钙比值的变化幅度达50%，这一变化主要源于蛋白石通量的下降；而总沉降通量则无显著变化趋势。上述结果表明，浮游生物群落能够对细微气候变化做出快速响应——诸如风速、降水、冬季水体通风以及中层水温的区域差异所体现的气候变化，便是此类细微变化的典型例证。倘若我们在沉降颗粒物组成中观测到的变化趋势能够在大尺度范围内发生，那么这些趋势将通过调节海-气二氧化碳交换与海洋反照率（albedo），进而对气候产生调控作用。