Hrycik Allison R, Stockwell Jason D
Rubenstein Ecosystem Science Laboratory University of Vermont Burlington Vermont USA.
Biology Department University of Vermont Burlington Vermont USA.
Limnol Oceanogr. 2021 Feb;66(2):481-495. doi: 10.1002/lno.11618. Epub 2020 Oct 4.
Factors that regulate planktonic communities under lake ice may be vastly different from those during the open-water season. Expected changes in light availability, ice cover, and snowfall associated with climate change have accelerated the need to understand food web processes under ice. We hypothesized that light limitation (bottom-up control) outweighs zooplankton grazing (top-down control) influence on phytoplankton biovolume and community structure under ice in a north temperate lake. Using in situ under-ice mesocosm experiments, we found that light had stronger effects on phytoplankton abundance than zooplankton, as expected. Specifically, low light limited growth of diatoms, cryptophytes, and chrysophytes. Zooplankton, however, also significantly affected some individual phytoplankton groups by decreasing diatoms and cryptophytes, in contrast to the common assumption that zooplankton grazing has negligible effects under ice. Ammonium and soluble reactive phosphorus (SRP) were lowest in high light treatments presumably through uptake by phytoplankton, whereas ammonium and SRP were highest in high zooplankton treatments, likely a result of zooplankton excretion. In situ experimental studies are commonly applied to understand food web dynamics in open-water conditions, but are extremely rare under ice. Our results suggest that changes in the light environment under ice have significant, rapid effects on phytoplankton growth and community structure and that zooplankton may play a more active role in winter food webs than previously thought. Changes in snow and ice dynamics associated with climate change may alter the light environment in ice-covered systems and significantly influence community structure.
调节湖冰下浮游生物群落的因素可能与敞水区季节的因素大不相同。与气候变化相关的光照可用性、冰盖和降雪的预期变化加速了人们对冰下食物网过程的理解需求。我们假设在一个北温带湖泊中，光照限制（自下而上的控制）对冰下浮游植物生物量和群落结构的影响超过浮游动物捕食（自上而下的控制）。通过冰下原位中宇宙实验，我们发现正如预期的那样，光照对浮游植物丰度的影响比浮游动物更强。具体来说，低光照限制了硅藻、隐藻和金藻的生长。然而，与通常认为浮游动物捕食在冰下影响可忽略不计的假设相反，浮游动物也通过减少硅藻和隐藻显著影响了一些单个浮游植物类群。铵和可溶性活性磷（SRP）在高光处理中最低，可能是由于浮游植物的吸收，而在高浮游动物处理中铵和SRP最高，这可能是浮游动物排泄的结果。原位实验研究通常用于理解敞水区条件下的食物网动态，但在冰下极为罕见。我们的结果表明，冰下光照环境的变化对浮游植物生长和群落结构有显著、快速的影响，并且浮游动物在冬季食物网中可能发挥比以前认为的更积极的作用。与气候变化相关的冰雪动态变化可能会改变冰封系统中的光照环境，并显著影响群落结构。
