Micropaleontology Laboratory, Geological Oceanography Division, National Institute of Oceanography, Goa, India.
Micropaleontology Laboratory, Geological Oceanography Division, National Institute of Oceanography, Goa, India.
Sci Total Environ. 2018 Sep 1;634:459-470. doi: 10.1016/j.scitotenv.2018.03.365. Epub 2018 Apr 6.
Calm conditions and extensive fishing, during monsoon season in the mudbank off Alleppey (Kerala), India creates a unique environment, associated with high suspended particulate matter. The effect of processes associated with mudbank formation, on benthic foraminifera, however, has not been documented. We have studied, seasonal foraminiferal distribution, to understand foraminiferal response to physico-chemical changes associated with the mudbank formation. Additionally, seasonal changes in total carbon, calcium carbonate (CaCO), organic carbon (C) and C/nitrogen (C/N) were also measured to understand the effect of mudbank formation on carbon burial. We report a low foraminiferal abundance in the mudbank. Benthic foraminiferal diversity is also low in the mudbank, during both pre-monsoon and monsoon season, clearly suggesting a stressed environment. Agglutinated foraminifera dominate the living benthic foraminiferal population in the mudbank, suggesting that the area is carbonate undersaturated and under fresh-water influence. Ammobaculites dilatatus and Ammobaculites exiguus are the dominant agglutinated species abundant in the mudbank and thus can be used to reconstruct past changes in the mudbank. The CaCO is consistently low during all seasons, at one of the core mudbank stations. The %C is, however, higher in the core mudbank as well as the northern peripheral region. The C/N is consistently uniform at all the stations indicating a similar source of organic matter in all the seasons. The higher %C and constant C/N suggest, that food availability and its source is not a major factor affecting benthic foraminifera in the mudbank. Instead, increased turbidity and low bottom water salinity are the main cause of seasonally stressed environment in the mudbank. Additionally, C degradation coupled with fresh water influx induced drop in bottom water pH is responsible for low foraminiferal population in mudbank region, in all the seasons. The reduced calcareous benthic foraminiferal abundance, however, does not affect the carbon burial in the mudbank, due to higher %C.
在印度喀拉拉邦阿勒皮（Alleppey）的泥滩（mudbank）的季风季节，平静的条件和广泛的捕鱼活动创造了一个独特的环境，与高悬浮物颗粒物有关。然而，与泥滩形成有关的过程对底栖有孔虫的影响尚未记录。我们研究了季节性有孔虫的分布，以了解与泥滩形成有关的理化变化对底栖有孔虫的响应。此外，还测量了总碳、碳酸钙（CaCO）、有机碳（C）和碳/氮（C/N）的季节性变化，以了解泥滩形成对碳埋藏的影响。我们报告说，泥滩中的有孔虫丰度较低。在泥滩中，无论是前季风期还是季风期，底栖有孔虫的多样性也很低，这清楚地表明环境受到了压力。胶结有孔虫在泥滩中的活体底栖有孔虫种群中占主导地位，表明该地区的碳酸盐不饱和，受淡水影响。膨胀胶结有孔虫（Ammobaculites dilatatus）和稀少胶结有孔虫（Ammobaculites exiguus）是泥滩中丰富的优势胶结种，因此可用于重建过去泥滩的变化。在一个核心泥滩站位，所有季节的 CaCO 含量都持续较低。然而，在核心泥滩以及北部周边地区，%C 较高。在所有站位，C/N 始终保持均匀，表明所有季节的有机物质来源相似。较高的%C 和恒定的 C/N 表明，食物的可利用性及其来源并不是影响泥滩底栖有孔虫的主要因素。相反，增加的浊度和底层水盐度降低是泥滩季节性压力环境的主要原因。此外，C 降解以及淡水流入导致的底层水 pH 值下降是所有季节泥滩地区有孔虫数量减少的原因。然而，由于较高的%C，减少的钙质底栖有孔虫丰度并不影响泥滩的碳埋藏。
