长棘海星暴发对珊瑚礁区沉积物营养盐动力学的影响研究

Study on the impacts of crown-of-thorns starfish on nutrient dynamics in the coral reef sediments

长棘海星暴发对珊瑚礁生态系统产生了严重危害,而水体营养盐的补充可能是导致长棘海星暴发的一个关键因素。砂质沉积物对调控珊瑚礁区的营养盐浓度和结构起着关键作用,因此本研究通过流动式反应器对长棘海星和砂质沉积物进行模拟实验,分析长棘海星排泄活动及其死亡后有机体降解对水体营养盐的影响,并探究砂质沉积物的响应。实验结果表明:(1)长棘海星排泄的溶解无机氮(DIN)和溶解无机磷(DIP)通量分别为(83.55±4.74)μmol/(ind.·h)和(2.53±0.03)μmol/(ind.·h),这些营养盐可能给长棘海星的持续暴发提供营养条件;(2)砂质沉积物对长棘海星排泄导致的营养盐浓度升高具有缓冲作用,约70.7%的DIN和91.4%的DIP被截留在沉积物中,但沉积物界面营养盐交换导致的氮磷比升高可能不利于珊瑚生长;(3)长棘海星死后的有机体降解可促使沉积物–水界面释放营养盐,结合海星暴发密度估算,其释放的营养盐可导致上覆水中DIN和DIP浓度分别升高0.32μmol/L和0.01μmol/L,这可能会促使大型藻的快速生长而妨碍珊瑚的自我修复。

The outbreak of crown-of-thorns starfish has seriously threatened the ecological health of coral reefs,and the supplement of nutrients in seawater may be a key factor leading to the outbreak of starfish.Sandy sediments play a key role in regulating the nutrient concentration and structure in coral reefs.Therefore,crown-ofthorns starfish and sandy sediments were incubated using flow-through reactor,to analyze the effects of crown-ofthorns starfish excretion and dead body degradation on nutrient concentration and structure,and to explore the role of sandy sediments under activities of crown-of-thorns starfish.The results were as followed:(1)crown-of-thorns starfish excreted dissolved inorganic nitrogen(DIN)and dissolved inorganic phosphorus(DIP)at rates of(83.55±4.74)μmol/(ind.·h)and(2.53±0.03)μmol/(ind.·h),respectively,which maight provide nutritional conditions for the continuous outbreak of starfish;(2)sandy sediments could regulate the nutrient concentration changed by the excretion of starfish,about 70.7%of DIN and 91.4%of DIP were trapped in the sediments,but the increase of DIN/DIP caused by nutrient exchange at the sediment-seawater interface may be detrimental to coral growth;(3)the degradation of starfish organisms could promote the release of nutrients at the sediment-seawater interface.Based on the density of starfish,the released nutrients could cause the concentrations of DIN and DIP in the overlying water to increase by 0.32μmol/L and 0.01μmol/L,respectively,which maight promote the rapid growth of macroalgae and hinder the self-restoration of corals.