Coccolithophores on the north-west European shelf: calcification rates and environmental controls
Coccolithophores on the north-west European shelf: calcification rates and environmental controls
复制标题
DOI：
10.5194/bg-11-3919-2014
复制
发表时间：
2014-07
期刊：
影响因子：
4.9
通讯作者：
A. Poulton;M. Stinchcombe;E. Achterberg;D. Bakker;C. Dumousseaud;H. Lawson;Gareth A. Lee;S. Richier;D. Suggett;J. Young
中科院分区：
文献类型：
--
作者：
A. Poulton;M. Stinchcombe;E. Achterberg;D. Bakker;C. Dumousseaud;H. Lawson;Gareth A. Lee;S. Richier;D. Suggett;J. Young
在远洋生产碳酸钙(方解石)方面，球石生物体是一个关键的功能群，尽管它们对陆架海生物地球化学的贡献以及这种贡献与环境条件的关系很少受到限制。在西北欧大陆架上进行了方解石产量(CP)和球石生物体丰度的测量，以检查球石生物体钙化沿碳酸盐化学、常量营养素有效性和浮游生物组成的自然梯度的趋势。在三个控制营养物质(硝酸盐、磷酸盐)和二氧化碳水平的生物测定实验中，也进行了类似的测量。除一个采样点外，所有采样点的叶绿素生物量和初级生产量(PP)均以纳米鞭毛虫(<；10μm)为主，CP在0.6~9.6mmolCm−2 d−1之间。在Heligoland附近完全混合的水域中，硅藻水华的CP和鞭毛虫丰度较高，而在北海中部和英吉利海峡西部的两个不同的球藻水华中则没有。球藻生物体丰度和CP与营养物质浓度或比例没有相关性，而CP、细胞特异性钙化(CELL-CF)和水柱中的光照之间的显著(p<；0.01)相关性突出了光照对中上层CP的强大控制作用。在实验生物测定中，大陆架水域(北海北部，挪威海沟)中以艾米利亚尼亚-赫克斯莱伊为主的球石群落对硝酸盐和磷酸盐的组合添加表现出强烈的CP响应，这是通过细胞-CF和生长速度的变化来调节的。相比之下，近海一个多样化的球虫群落(比斯开湾)对营养添加没有反应，而光可获得性或死亡率可能在控制这个群落方面起到了更重要的作用。在生物测定实验中，pH的急剧下降和方解石饱和状态的大致减半导致比斯开湾和北海北部的CP下降，但挪威海沟没有。CP的这些降低与二氧化碳浓度升高(750atm)时生物测定中的增长速度相对于环境处理中的增长速度减慢有关。我们研究的综合结果突出了西北欧大陆架水域中球藻对光照、营养物质和碳酸盐化学的不同反应，这是由生长速度、细胞-CF和物种组成的变化所调节的。
Coccolithophores are a key functional group in terms of the pelagic production of calcium carbonate (calcite), although their contribution to shelf sea biogeochemistry, and how this relates to environmental conditions, is poorly constrained. Measurements of calcite production (CP) and coccolithophore abundance were made on the north-west European shelf to examine trends in coccolithophore calcification along natural gradients of carbonate chemistry, macronutrient availability and plankton composition. Similar measurements were also made in three bioassay experiments where nutrient (nitrate, phosphate) and pCO2 levels were manipulated. Nanoflagellates (< 10 μm) dominated chlorophyll biomass and primary production (PP) at all but one sampling site, with CP ranging from 0.6 to 9.6 mmol C m−2 d−1. High CP and coccolithophore abundance occurred in a diatom bloom in fully mixed waters off Heligoland, but not in two distinct coccolithophore blooms in the central North Sea and Western English Channel. Coccolithophore abundance and CP showed no correlation with nutrient concentrations or ratios, while significant (p < 0.01) correlations between CP, cell-specific calcification (cell-CF) and irradiance in the water column highlighted how light availability exerts a strong control on pelagic CP. In the experimental bioassays, Emiliania-huxleyi-dominated coccolithophore communities in shelf waters (northern North Sea, Norwegian Trench) showed a strong response in terms of CP to combined nitrate and phosphate addition, mediated by changes in cell-CF and growth rates. In contrast, an offshore diverse coccolithophore community (Bay of Biscay) showed no response to nutrient addition, while light availability or mortality may have been more important in controlling this community. Sharp decreases in pH and a rough halving of calcite saturation states in the bioassay experiments led to decreased CP in the Bay of Biscay and northern North Sea, but not the Norwegian Trench. These decreases in CP were related to slowed growth rates in the bioassays at elevated pCO2 (750 μatm) relative to those in the ambient treatments. The combined results from our study highlight the variable coccolithophore responses to irradiance, nutrients and carbonate chemistry in north-west European shelf waters, which are mediated by changes in growth rates, cell-CF and species composition.