Cadmium and phosphorus cycling in the water column of the South China Sea: The roles of biotic and abiotic particles
Cadmium and phosphorus cycling in the water column of the South China Sea: The roles of biotic and abiotic particles
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DOI：
10.1016/j.marchem.2009.07.005
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发表时间：
2009-06-20
期刊：
影响因子：
3
通讯作者：
Sheu, David D.
中科院分区：
文献类型：
--
作者：
Ho, Tung-Yuan;You, Chen-Feng;Sheu, David D.
利用ICPMS测定了大小分异浮游植物、浮游动物和下沉颗粒中镉、磷和铝的浓度，以评估生物和非生物颗粒对水柱中Cd和P的循环和比率的作用。浮游生物分别于2002年和2006年两次使用配备10、60和150 μ m孔径浮游生物网的过滤装置进行采集，并于2004 - 2005年在120、600和3500 m深度使用系泊沉积物捕集器进行下沉颗粒采样。与我们之前的研究结果相反，即浮游生物中大多数其他生物活性微量金属与非生物Al密切相关，并吸附在浮游植物上[Ho，T.Y.]，文，l.s.，你。c.f., Lee, d.c., 2007。南海浮游生物的微量金属组成：生物与非生物来源。海洋学报52,1776- 1788。]， Cd/P比值在0.12 ~ 0.34 mmol/mol R范围内不随Al的变化而变化，在不同大小的浮游生物中表现出相当一致的值，表明Cd主要以细胞内为基础被吸收。在沉降颗粒方面，Cd和P的通量以及Cd/P比值都受到生物和非生物颗粒的强烈影响。总体而言，沉降颗粒的Cd/P比值在0.03 ~ 1.2 mmol/mol之间，在生产季节120 m处捕集器的Cd/P值最高。在深水中，在高通量期观察到最低值。在地表深度，通量和Cd/P比在该区域最多产季节升高。120 m捕集器捕集率的升高很可能与优势种（球石藻）在生育期优先吸收Cd有关。相对而言，Cd/P比值随着深水Al通量的增加而急剧下降，且远低于从产岩颗粒和生物颗粒的相对部分得到的预期Cd/P比值，表明在高产岩颗粒通量时期，深水可溶P在产岩颗粒中有明显的吸附作用。从水体年平均通量和直立存量来看，生物源Cd和P在水体顶部120 m和600 m的停留时间分别为0.10年和0.20年，250年和100年，9100年和5000年，在水体整体上也表现出对Cd的优先去除，而对P的去除在深水区相对较高。我们的研究表明，微藻群落结构的变化以及岩性矿物的输入都是影响地质时间尺度上海水Cd/P比值的潜在重要因素。(C) 2009 Elsevier B.V.版权所有
The concentrations of cadmium, phosphorus, and aluminum in size-fractionated phytoplankton, zooplankton, and sinking particles are determined using ICPMS to evaluate the roles of biotic and abiotic particles on the cycling and ratios of Cd and P in the water column. Plankton were collected with a filtration apparatus equipped with 10, 60, and 150-mu m aperture plankton nets on two occasions (2002 and 2006), and sinking particles were sampled by moored sediment traps deployed at depths of 120, 600, and 3500 m from 2004 to 2005. In contrast to what our previous study revealed, i.e., that most of the other bioactive trace metals in plankton were strongly correlated with abiotic Al and adsorbed on phytoplankton [Ho,T.Y., Wen, L.S., You. C.F., Lee, D.C., 2007. The trace metal composition of size-fractionated plankton in the South China Sea: biotic versus abiotic sources. Limnol Oceanogr 52,1776-88.], Cd/P ratios, ranging from 0.12 to 0.34 mmol/mol R did not vary with Al and exhibited fairly consistent values among different sizes of plankton, showing that Cd was mostly incorporated on an intracellular basis. In terms of the sinking particles, fluxes in Cd and P as well as in Cd/P ratios were strongly influenced by both biotic and abiotic particles. Overall, the Cd/P ratios in the sinking particles ranged from 0.03 to 1.2 mmol/mol, with the highest value observed in traps at 120 m during the productive season. The lowest value was observed in deep water during high flux periods for lithogenic particles. At surface depth, flux and Cd/P ratios were elevated during the most productive season in the region. The elevated ratios in the traps at 120 m were most likely related to preferential uptake of Cd for the dominant species (coccolithophores) during the productive period. Relatively, Cd/P ratios sharply decreased with increasing Al flux in deep water and ratios were much lower than the expected Cd/P ratios obtained from the relative portion of lithogenic and biogenic particles, indicating that the adsorption of soluble P into lithogenic particles was significant in the deep water during high lithogenic particle flux periods. Using averaged annual fluxes and standing stock in the water column, the residence time of biogenic Cd and P are 0.10 and 0.20, 250 and 100, and 9100 and 5000 years respectively in the top 120 m, 600 m, and water column as a whole, also showing preferential removal for Cd in the euphotic zone but relatively higher removal rates for P in the deep water. Our study suggests that the shift in microalgal community structure along with input of lithogenic minerals are both potentially important factors in influencing Cd/P ratios in oceanic water on a geological time scale. (C) 2009 Elsevier B.V. All rights reserved.