台湾海峡上升流区浮游植物对营养盐添加的响应

Response of phytoplankton to nutrients addition in the upwelling regions of the Taiwan Strait

2006年6月在台湾海峡近岸上升流区通过表层水体营养盐添加的现场培养实验,研究该海区营养盐限制情况及其浮游植物水华产生的主要影响因素。对营养盐,叶绿素a浓度和浮游植物细胞丰度进行了测定,结果表明,实验中不存在明显的硅限制;氮磷营养盐均存在明显的限制,且氮限制情况更为严重。营养盐添加后,冰河拟星杆藻(Asterionellopsis glacialis)等硅藻迅速生长成为优势藻种,其对氮磷的利用机制有所不同。对氮营养盐采取吸收后迅速同化利用,相较于硝酸盐的补充,氨氮补充条件下优势硅藻更易迅速生长并迅速死亡;对磷营养盐的利用则由于体内磷库的存在,采用迅速吸收后贮存在体内慢慢消耗的利用机制。氮营养盐的补充是上升流期间浮游植物水华产生的主要因素。

In situ incubation experiments of nutrients addition to surface water from the upwelling region in the Taiwan Strait were conducted to investigate nutrient limitation of this area and the main factors that caused the phytoplankton bloom in June,2006.Variation of nutrients,Chl-a concentration and phytoplankton species density were analyzed.The results showed no clear limitation by silicon,however clear nitrogen and phosphate limitations were found,and nitrogen limitation was more serious than phosphate limitation.Diatoms,such as Asterionellopsis glacialis grew immediately to become the dominant species after nutrients were added.Different mechanisms were used to explain the assimilation of nitrogen and phosphate by these dominant diatoms.Nitrogen was taken up and assimillated immediately after it was added.Ammonium addition resulted in rapid growth and die-out of the dominant diatoms compared with that of nitrate addition.However,because of the phosphate pool inside phytoplankton,the added phosphate was taken up quickly and stored,then assimilated slowly.The results suggest that nitrogen supply was the main factor that caused the phytoplankton bloom in the Taiwan Strait during the upwelling in 2006.