Coelho J P, Pereira M E, Duarte A C, Pardal M A
CESAM & Chemistry Department, Campus de Santiago, University of Aveiro, 3810-193 Aveiro, Portugal.
Mar Pollut Bull. 2009 Aug;58(3):358-65. doi: 10.1016/j.marpolbul.2008.10.014. Epub 2008 Dec 5.
There is an ongoing eutrophication process in the Ria de Aveiro coastal lagoon (Portugal), with progressive replacement of rooted primary producers for macroalgae. Taking advantage of a well-defined environmental contamination gradient, we studied mercury accumulation and distribution in the aboveground and the belowground biomass of several salt marsh plants, including the seagrass species Zostera noltii and the dominant green macroalgal species Enteromorpha sp. The results of these experiments were then placed into the context of the estuarine mercury cycle and transport from the contaminated area. All salt marsh plants accumulated mercury in the root system, with Halimione portulacoides showing the highest levels, with up to 1.3 mg kg(-1) observed in the most contaminated area. Belowground/aboveground ratios were generally below 0.4, suggesting that salt marsh plants are efficient immobilizers and retainers of mercury agents. Moreover, due to their sediment accretion capacities, salt marsh plants seem to play an important role in the sequestration of mercury in estuarine sediments. Seagrasses, on the other hand, accumulated considerable amounts of mercury in the aboveground biomass with belowground/aboveground ratios reaching as high as 1.4. These results may be due to their different routes of uptake (roots and foliar uptake) which suggests that seagrass meadows can be an important agent in the export of mercury from contaminated areas, considering the high aboveground biomass replacement rates. Rooted macrophytes accumulate less mercury in their aboveground biomass than macroalgae. The change of primary producer dominance due to eutrophication can originate a 4- to 5-fold increase in primary producer associated mercury. This mercury would be available for export, making it bioavailable to estuarine food webs, which stresses the need to reverse the current eutrophic status of estuarine systems.
葡萄牙阿威罗里亚海岸泻湖正在经历富营养化过程，有根的初级生产者正逐渐被大型藻类取代。利用明确的环境污染梯度，我们研究了几种盐沼植物地上和地下生物量中汞的积累和分布情况，其中包括海草物种波叶海泽藻和优势绿藻物种浒苔。然后将这些实验结果置于河口汞循环以及从污染区域的汞传输背景下进行分析。所有盐沼植物的根系都积累了汞，盐角草的汞含量最高，在污染最严重的区域观测到高达1.3毫克/千克。地下/地上比通常低于0.4，这表明盐沼植物是汞的有效固定者和保留者。此外，由于其沉积物堆积能力，盐沼植物似乎在河口沉积物汞的固存中发挥着重要作用。另一方面，海草地上生物量积累了大量汞，地下/地上比高达1.4。这些结果可能归因于它们不同的吸收途径（根系吸收和叶面吸收），这表明考虑到地上生物量的高替换率，海草草甸可能是污染区域汞输出的重要媒介。有根大型植物地上生物量积累的汞比大型藻类少。富营养化导致的初级生产者优势变化可能使与初级生产者相关的汞增加4至5倍。这种汞可供输出，使其在河口食物网中具有生物可利用性，这凸显了扭转河口系统当前富营养化状态的必要性。
