Influences of typhoons and extreme rains on plankton through bottom-up effects in Feitsui Reservoir
Date Issued
2015
Date
2015
Author(s)
Huang, Wei-Chung
Abstract
Abstract The frequency of extreme weather events has increased due to climate change, resulting in strong disturbances in ecosystems. Extreme precipitations (EP) in lake systems caused by typhoons and extreme rains (ER) represent a pressing concern. Previous studies indicate that EP can cause disturbances to phytoplankton communities owing to increased turbidity (OBS) and nutrients (PO43-) coming from upper streams. However, whether and how these bottom-up effects can be transferred to zooplankton remains elusive. To tackle this issue, we investigated the zooplankton communities, phytoplankton biomasses, and environmental factors in both the pre-EP and post-EP periods of multiple EP events from 2008 to 2012 in Feitsui Reservoir. We found that, in general, turbidity and PO43- increased after EPs. Meanwhile, chlorophyll a decreased immediately after EPs due to light blocking effects and then gradually recovered to its original level in two weeks. In addition, the depth of chlorophyll a maximum decreased about 6 meter after typhoons. These two responses of chlorophyll a indicated that phytoplankton were mainly affected by turbidity immediately after EPs. More importantly, we found that zooplankton showed differential responses to EP events depending on their body size and feeding habit. More specifically, the species composition of zooplankton shifted to being dominated by smaller species after typhoons and extreme rains. This compositional shift resulted in a decrease in the total biomass, although the total abundance was increased. In addition, species composition of zooplankton changes significantly between the pre-EP, post-EP, and normal periods, as shown by the discriminant analysis. These findings indicated that EP events altered the physical and chemical conditions of lake environment and the disturbance can be transferred to phytoplankton and zooplankton. Both phytoplankton and zooplankton decreased in abundance, and in addition, zooplankton changed their size and species composition.
Subjects
typhoon
extreme precipitation
bottom-up effect
phytoplankton
zooplankton
deep lake
Feitsui reservoir
species composition
SDGs
Type
thesis
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