热带西太平洋Y3和M2海山微食物网主要类群生态分布与比较

COMPARISON IN THE DISTRIBUTION OF MICROBIAL FOOD WEB COMPONENTS IN THE Y3 AND M2 SEAMOUNTS IN THE TROPICAL WESTERN PACIFIC

2014年12月和2016年3月分别对热带西太平洋Y3海山(中层海山)和M2海山(浅海山)微食物网主要类群(包括聚球藻、原绿球藻、微微型真核浮游生物、异养细菌和浮游纤毛虫)丰度和生物量垂直分布进行了研究。结果表明,Y3和M2海山水文环境比较相似但略有区别,叶绿素最大值层(DCM)分别在75—100m和110m水层,微食物网各主要类群在垂直尺度上的分布与叶绿素a浓度紧密相关。其中浮游纤毛虫呈现"双峰型"模式,即丰度高值出现在表层和DCM层;原绿球藻和微微型真核浮游生物呈现"单峰型"模式,丰度高值出现在DCM层;聚球藻和异养细菌峰型相对不显著,DCM层以浅丰度较高,DCM层以深丰度明显降低。分析其原因,可能是受到温度、光照和营养盐的共同影响。Y3和M2海山微食物网结构的垂直变化不完全一致。其中,Y3海山30m以浅和150m以深异养细菌生物量占绝对优势,75—100m水层自养型生物(原绿球藻和微微型真核浮游生物)占绝对优势;M2海山75m以浅和200m以深异养细菌占绝对优势,110—150m自养型生物占绝对优势。M2海山自养型生物占优势的水层要明显深于Y3海山,可能与它们的海山类型和采样季节不同有关。

Abundance and biomass of microbial food web components, including Synechococcus, Prochlorococcus, picoeukaryotes, heterotrophic bacteria, and planktonic ciliate, were investigated in the Y3 and M2 seamounts of the tropical Western Pacific in December 2014 and March 2016, respectively. The vertical distribution of planktonic ciliate showed ＂bimodal＂ pattern, showing high abundance at the surface and the deep chlorophyll maximum（DCM） layer. Prochlorococcus and picoeukaryotes exhibited ＂unimodal＂ pattern with a maximum abundance in the DCM layer. No significant peak was observed in vertical distributions of Synechococcus and heterotrophic bacteria abundance. Temperature, light availability, and nutrient supply were responsible for the distribution patterns of the microbial food web components in the seamounts. In addition, the vertical distribution of microbial food web structure was different between Y3 and M2 seamounts. In the Y3 seamount, heterotrophic bacteria biomass was dominant in the layers above 30 m and below 150 m, whereas Prochlorococcus and picoeukaryotes were dominant between 75 m and 100 m. In the M2 seamount, heterotrophic bacteria were dominant in the upper 75 m layer and below 200 m. Prochlorococcus and picoeukaryotes were dominant in layers between 110 m and 150 m. The differences may be related to the types of the two seamounts and sampling seasons.