Salp grazing: effects on phytoplankton abundance, vertical distribution and taxonomic composition in a coastal habitat
Salp grazing: effects on phytoplankton abundance, vertical distribution and taxonomic composition in a coastal habitat
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樽海鞘放牧：对沿海栖息地浮游植物丰度、垂直分布和分类组成的影响
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
Chang Fh
中科院分区：
文献类型：
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作者：
Zeldis;Davis Cs;J. Mr.;Ballara Sl;Booth We;Chang Fh
本文是在豪拉鲁湾对鲷科鲷Pagrus auratus（Sparidae）春夏季产卵期的卵和幼体死亡率进行的为期3年的环境影响研究的基础上得出的结果。在前2年中，在11月和12月，中间浮游动物的生物量以民主海樽（Thalia democratjca）和梭形海樽（Salpa fuslformls）为主，固定层的叶绿素a平均浓度降低，叶绿素a最大值远低于混合层。第三年，海鞘非常稀少，混合层中chl a较丰富，chl a最大值位于混合层底部。硅藻占主导地位的浮游植物群落在第一个2年，特别是低于混合层，但更均匀的混合硅藻，甲藻和鞭毛虫是在第三年。平均混合层深度和分层强度变化不大，在整个3年，这表明在垂直混合率的变化并没有驱动浮游植物的对比。海鞘人口放牧率高，足以超过浮游植物的人口增长在许多网站。然而，大多数网站有较低的salp生物量比这一点，但叶绿素a浓度的降低和加深的叶绿素a最大值是广泛的，并在时间上持续。chl a的垂直分布在营养盐-浮游植物-浮游动物模型中进行了模拟，该模型将具有高沉积有机废物的以salp为主的群落与废物原位回收的微型浮游动物群落进行了对比。这个模型，并计算放牧，沉积和水柱混合率，表明营养物质纳入到salp质量和沉积的废物材料从salp放牧的速率将远远大于通过密度跃层的混合refereralized营养备份。这会导致形成深层叶绿素a极大值，并在显著的放牧压力消散后持续存在。浮游植物分类组成的变化解释在不同的放牧，营养和光照制度下的类群的增长率。海鞘放牧在沿海环境中的主要影响似乎是加深浮游植物的分布和减少生物量，而不是从真光层完全删除浮游植物生物量，可以发生在斜坡和海洋沃茨。
This paper comes from a 3 yr study of environmental effects on egg and larval mortality of snapper Pagrus auratus (Sparidae), during their spring-summer spawning season in the Hauralu Gulf In the first 2 yr, the salps Thalia democratjca and Salpa fuslformls dominated mesozooplankton biomass in November and December, average chl a concentrations In the rn~xed layer were reduced and chl a maxima were well below the mixed layer. In the third year, salps were very rare, and the mixed layer was richer in chl a and the chl a maxima were at the bottom of the mixed layer. Diatoms dominated the phytoplankton community in the first 2 yr, especially below the mixed layer, but a more even mix of diatoms, dinoflagellates and flagellates was present in the third year. Averaged mixed layer depth and stratification intensity varied little across the 3 yr, suggesting that variation in vertical mixing rates did not drive the phytoplankton contrasts. Salp population grazing rates were high enough to overtake phytoplankton population growth at many sites. However, most sites had lower salp biomass than this, yet the reduction of chl a concentration and deepening of chl a maxima were widespread and temporally persistent. The vertical distributions of chl a were simulated in a nutrient-phytoplankton-zooplankton model which contrasted a salp-dominated community that had high sedimentation of organic wastes with a microzooplankton community within which wastes were recycled in situ. This model, and calculated rates of grazing, sedimentation, and water column mixing, showed that rates of nutrient incorporation into salp mass and sedimentation of waste material from salp grazing would be much greater than mixing of remineralized nutrient back up through the pycnocline. This causes formation of deep chl a maxima which can persist well after significant grazing pressure has dissipated. The variation in phytoplankton taxonomic composition is explained in terms of growth rates of the taxa under different grazing, nutrient and light regimes. The major effects of salp grazing in the coastal environment appear to be to deepen phytoplankton distributions and reduce biomass, rather than to remove phytoplankton biomass from the euphotic zone completely, as can occur in slope and oceanic waters.