| 摘要: |
| 本研究向自然海水中接种中肋骨条藻（Skeletonema costatum）、红色哈卡藻（Akashiwo sanguinea）和球形棕囊藻（Phaeocystis globosa）游离单细胞进行培养，比较不同赤潮藻类对海洋浮游微食物网主要类群的影响。结果发现，红色哈卡藻和中肋骨条藻均经历了从增殖到衰亡的过程，中肋骨条藻在磷酸盐耗尽后消亡，磷酸盐随之被重新释放到水体中；而无论增殖还是衰亡，红色哈卡藻添加组磷酸盐含量均持续降低。球形棕囊藻游离单细胞在迅速增殖将磷酸盐耗尽后并未衰亡，其密度维持相对稳定。红色哈卡藻添加组和中肋骨条藻添加组的细菌密度显著低于中肋骨条藻添加组（P<0.05）。三种藻类相比，红色哈卡藻添加组中纤毛虫、异养微型鞭毛虫（heterotrophic nanoflagellate, HNF）和含色素体微型鞭毛虫（pigmented nanoflagellate, PNF）的丰度最高（P<0.05），但该组微型鞭毛虫的营养结构（HNF/PNF）与中肋骨条藻添加组无显著差异（P>0.05）。球形棕囊藻添加组含色素体微型鞭毛虫的丰度显著降低（P<0.05），从而导致该组微型鞭毛虫营养结构显著偏向异养（P<0.05）。实验结束时，球形棕囊藻添加组纤毛虫的丰度显著低于其他两组（P<0.05）。本研究中，球形棕囊藻可通过与含色素体微型鞭毛虫竞争营养盐并抵御异养微型鞭毛虫及纤毛虫捕食的方式对微食物网产生影响。红色哈卡藻对微食物网的影响主要是由于其可被异养微型鞭毛虫摄食。中肋骨条藻对微食物网的影响受营养盐的调节，细菌的分解可能在该藻衰亡后的营养盐再生过程中发挥重要作用 |
| 关键词: 海洋生物学 中肋骨条藻 红色哈卡藻 球形棕囊藻 异养细菌 微型鞭毛虫 纤毛虫 |
| DOI：10.3969/J.ISSN.2095-4972.2022.03.006 |
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| 基金项目:广西自然科学基金资助项目（2018GXNSFAA138194）；广西科技重大专项资助项目(桂科AA17202020 |
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| Effects of three red tide species on the major planktonic groups in microbial food web in the coastal water of Beibu Gulf |
| LU Jiachang,LU Minzhen,LI Jie,LAI Junxiang,ZHUANG Junlian |
| (Guangxi Key Laboratory of Marine Environmental Science, Guangxi Beibu Gulf Marine Research Center, Guangxi Academy of Sciences, Nanning 530007, China) |
| Abstract: |
| To compare the responses of major planktonic groups in microbial food web, the red tide causative species Skeletonema costatum, Akashiwo sanguinea and solitary cells of Phaeocystis globosa, were introduced and incubated in the natural seawater, respectively. The results showed that both S. costatum and A. sanguinea underwent a lysis phase after proliferation during experiments. S. costatum declined after phosphate depletion and the phosphate was released back to water during lysis phase. Unlike S. costatum, phosphate concentration in A. sanguinea group reduced in both proliferation and lysis phase. P. globosa did not decline but sustained in stationary phase after nutrients depleted. The abundance of heterotrophic bacteria was significantly higher in S. costatum group than in other two groups (P<0.05). And compared with other algae, the highest abundance of ciliates, heterotrophic nanoflagellate (HNF) and pigmented nanoflagellate (PNF) appeared in A. sanguinea group (P<0.05). However, no significant differences in trophic structures of nanoflagellate (HNF/PNF) were found between A. sanguinea and S. costatum groups (P>0.05). Comparatively, the trophic structure of nanoflagellates in P. globosa group preferred heterotrophy (P<0.05) as a result of significantly decreased PNF (P<0.05), and the abundance of ciliates was also the lowest at the end of experiments (P<0.05). The results suggest that the effects of P. globosa on microbial food web may compete nutrients with PNF and show chemical defense against predators of HNF and ciliates. And the influence of A. sanguinea on the organisms within microbial food web was mainly due to its edible by HNF. The effects of S. costatum on microbial food web were modulated by nutrients and bacteria may play an important role in nutrient regeneration during lysis phase. |
| Key words: marine biology Skeletonema costatum Akashiwo sanguinea Phaeocystis globosa heterotrophic bacterium nanoflagellate ciliate |
