九龙江口浮游生物群落呼吸速率及其影响因素

Factors Regulating Pelagic Community Respiration in Jiulong River Estuary

采用甲板培养的方法,于2015年秋季和2016年夏季分别对九龙江口表层水体的浮游生物群落呼吸速率进行了研究,同时测定与浮游生物群落呼吸作用相关的环境参数,分析环境因素对呼吸速率的影响。结果表明,秋季浮游生物群落呼吸速率变化范围为4.3~43.1 μmol·(L·d)^-1 ,沙口上游群落呼吸速率显著高于河口下游,而夏季群落呼吸速率的变化范围为14.5~23.4 μmol·(L·d)^-1 ,最大值却出现在河口下游的藻华区。统计分析表明,在生物量较低的秋季,浮游生物群落呼吸速率与溶解有机碳(dissolved organic carbon,DOC)、叶绿素a(chlorophyll a,Chl-a)均呈显著的正相关,与溶解氧(dissolved oxygen,DO)呈显著负相关;而在生物量较高的夏季群落,呼吸速率与Chl-a、DOC呈弱正相关性,与DO几乎没有相关性。说明,在生产力低的季节,群落呼吸作用不但对DOC的依赖更高,而且自养-异养耦合程度也更大;秋季DO浓度主要受控于浮游生物群落的呼吸作用,夏季则主要受控于浮游植物的光合作用。

The pelagic community respiration rates of surface waters were measured as in vitro changes of dissolved oxygen concentration during deck incubations in November 2015 (autumn) and July 2016 (summer).The environmental parameters related to the community respiration were also determined,and the response of pelagic community respiration rate to environmental factors was analyzed.The results showed that the community respiration rates exhibited significant spatial and seasonal variations in Jiulong River Estuary.In autumn,the respiration rates in the surface water ranged from 4.3 to 43.1 μmol·(L· d)^-1 ,in the upper reaches of the estuary were significantly higher than rates in downstream.On the contrary,in summer,community respiration rates ranged from 14.5 to 23.4 μmol·(L· d)^-1 ,and the maximum respiration rate was observed in the algal bloom area in the lower estuary.Statistical analysis showed that the pelagic community respiration rates were significantly and positively correlated with both DOC and Chl-a concentration in autumn with low phytoplankton biomass,while in summer with high biomass,the community respiration rates were positively but no significantly correlated with Chl-a and weak positively correlated with DOC concentration.These results suggested that the pelagic community respiration was dependent more on allochthonous DOC supplied,and that the autotrophic-heterotrophic coupling degree was greater in low productive season than in high productive season.In autumn,DO concentrations in Jiulong River Estuary were mainly controlled by the pelagic community respiration,while in summer,photosynthetic oxygen production had more influence on DO concentrations than community respiration.