北极楚科奇海北部特征水团对浮游植物空间分布的调控

Regulation of phytoplankton distribution by characteristic water masses in the northern Chukchi Sea,Arctic

通过楚科奇海北部–加拿大海盆西侧交接地带的生态调查,我们发现0~150 m海域水体中以融冰水(MW,0~20 m)、白令海夏季水(sBSW)和阿拉斯加沿岸流(ACW)等水团为主。水温和营养盐变化与水团息息相关,物理–生化的耦合作用进一步影响了浮游植物分布和群落结构。叶绿素a浓度最大值多位于约50 m深、富含营养盐的sBSW和ACW暖水团中。sBSW和ACW中分别以小型(占比约74%)和微微型(占比约65%)浮游植物为主。藻华初期,溶解无机氮(DIN)虽呈相对限制状态,但仍高于浮游植物生长所需阈值。双单元混合模型显示:浮游植物对氮去除明显,氮吸收量与叶绿素a浓度呈正比,且在温度略高的ACW水团中氮吸收量高于sBSW水团。在北极变暖、波弗特流涡增强以及ACW和sBSW营养盐补给下,该区域的浮游植物的叶绿素a浓度(均值:(0.327±0.163)mg/m^(3),范围:0.04~0.69 mg/m^(3))与历史数据相比有所提高。这将增加北极海区的碳吸收通量,有利于其作为碳汇区的发展。

Based on ecological observations of the northern Chukchi Sea and the western Canada Basin junction zore,We found that within the upper 150 m,the phytoplankton distribution was complicated by dominant water masses:the Melting Water(MW),the Alaskan Coastal Water(ACW)transported with the Beaufort Gyre(BG),and summer Bering Sea Water(sBSW).The changes of temperature and nutrients were closely related to water mass,and the physical-biochemical coupling effect further affects the distribution and community structure of phytoplankton.The Chl a maximum concentration layer often existed in the dim water of about 50 m depth.In the nutrient-rich sBSW and ACW dominant water-mass,phytoplankton were dominant by netplankton(74%of the total Chl a concentration)and picoplankton(65%of the total Chl a concentration).In the early stage of bloom,dissolved inorganic nitrogen(DIN)was relative limited to phosphate,while bioavailable nitrogen was still above the absolute limit threshold.The DIN-Salinity conservative mixing model showed that phytoplankton significantly removed nitrogen,and the nitrogen-uptake was positively related to Chl a concentration.The amount of nitrogen uptake in ACW water mass with slightly higher temperature was higher than that in sBSW water mass.In response to Arctic warming,the enhanced Beaufort Gyre,and nutrient supply from ACW and sBSW,Chl a concentration of phytoplankton in this region(ranged from 0.04−0.69 mg/m^(3) with an average of(0.327±0.163)mg/m^(3))were higher than the historical observations.This will increase the carbon absorption flux in the Arctic sea area,which is conducive to its development as a carbon sink area.