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首页> 外文期刊>Estuarine Coastal and Shelf Science >Benthic response to shellfish farming in Thau lagoon: Pore water signature
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Benthic response to shellfish farming in Thau lagoon: Pore water signature

机译：底特乌对礁湖贝类养殖的反应：孔隙水特征

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摘要

Vertical distributions of dissolved species across the sediment—water interface (SWI), including major cations (sodium, potassium, magnesium, calcium), minor cations (lithium, strontium, barium), redox sensitive species (dissolved manganese, iron, sulfate, sulfide, ammonium) and other chemical parameters (pH, alkalinity, soluble reactive phosphorous, dissolved silica) were studied in a Mediterranean lagoon used for intensive shellfish farming. In order to quantify the impact of this activity on diagenetic processes and the influence of seasonal changes, two stations contrasted with respect to organic carbon fluxes were sampled in Thau lagoon from March 2001 to August 2002 during four field campaigns in winter, spring, summer and fall. Well-defined layers enriched with redox sensitive species were observed following the conventional sequence of early diagenetic reactions. However, differences were observed between both stations in depths and thickness layers. Concentration gradients extended down to more than 92 cm depth at the central position of the lagoon (station C4 — 8 m depth) and down to 40 cm depth inside shellfish farming zones (station C5 — 9 m depth). Station C4 showed an unusual diagenetic signature: sharp dissolved oxygen, iron, nitrate and manganese gradients existed at the SWI but gradients of dissolved sulfide and alkalinity as well as other parameters (dissolved silica, Ba, etc.) were recorded only from 25 to 30 cm depth downward. Seasonal changes were observed in pore water composition as deep as 30—50 cm in station C4 (only 15 cm in station C5). The center of the lagoon is not directly subjected to biodeposits deriving from shellfish activity. Isotopic and bioturbation data allowed to rule out a reworking of the sediment deeper than a few centimeters. In addition to organic content of the sediment, physical parameters were likely to induce the 10—20 cm gap between dissolved iron and sulfide profile as well as the higher vertical extent of diagenetic sequence observed at station C4. Conversely to station C5, station C4 underwent stronger currents and wave effect probably generating advective transport of water through the sediment, but no permeability data were available to confirm this hypothesis. During summer, climatic conditions generated vertical stratification of the water column and transient suboxic conditions at the bottom. Such conditions drove the upward shift of redox fronts, compacting the diagenetic sequence. These effects were reinforced at station C5 by shellfish and its farm structures (mainly attenuation of current and increased heat absorption).
机译：沉积物-水界面（SWI）中溶解物质的垂直分布，包括主要阳离子（钠，钾，镁，钙），次要阳离子（锂，锶，钡），氧化还原敏感物质（溶解的锰，铁，硫酸盐，硫化物） ，铵盐）和其他化学参数（pH，碱度，可溶性反应性磷，溶解二氧化硅）在用于集约化贝类养殖的地中海泻湖中进行了研究。为了量化该活动对成岩过程的影响和季节变化的影响，在2001年3月至2002年8月的冬季，春季，夏季和冬季进行了四次野外活动，在Thau泻湖采样了两个与有机碳通量形成对比的站点。秋季。按照早期成岩反应的常规顺序，观察到了富含氧化还原敏感物质的界限分明的层。但是，在深度和厚度层两个站之间都观察到了差异。在泻湖的中心位置（C4站— 8 m深度），浓度梯度下降到超过92 cm的深度，在贝类养殖区内（C5站— 9 m深度）下降到40 cm深度。 C4站显示出不同寻常的成岩特征：在SWI处存在急剧的溶解氧，铁，硝酸盐和锰梯度，但仅在25至30之间记录了溶解的硫化物和碱度以及其他参数（溶解的二氧化硅，Ba等）的梯度。向下厘米深。在C4站深达30-50 cm的孔隙水成分中观察到季节性变化（在C5站仅15 cm）。泻湖的中心没有直接受到来自贝类活动的生物沉积物的影响。同位素和生物扰动数据可以排除深于几厘米的沉积物再加工。除了沉积物中的有机物外，物理参数还可能导致溶解铁和硫化物剖面之间存在10-20 cm的间隙，以及在C4站观测到的成岩作用序列的垂直范围更高。与C5站相反，C4站经历了更强的水流和波浪作用，可能会产生通过沉积物的平流水，但是没有渗透率数据可用于证实这一假设。在夏季，气候条件使水柱产生垂直分层，并在底部产生短暂的低氧环境。这样的条件驱使氧化还原前沿向上移动，从而压缩了成岩序列。贝类及其养殖场结构在C5站加强了这些影响（主要是电流衰减和热量吸收增加）。

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