Abstract
Many studies have focused on the interactive effects of temperature increases due to global warming and nutrient enrichment on phytoplankton communities. Recently, non-temperature effects of climate change (e.g., decreases in wind speed and increases in solar radiation) on large lakes have received increasing attention. To evaluate the relative contributions of both temperature and non-temperature effects on phytoplankton communities in a large eutrophic subtropical shallow lake, we analyzed long-term monitoring data from Lake Taihu, China from 1997 to 2016. Results showed that Lake Taihu’s spring phytoplankton biovolume and composition changed dramatically over this time frame, with a change in dominant species. Stepwise multiple linear regression models indicated that spring phytoplankton biovolume was strongly influenced by total phosphorus (TP), light condition, wind speed and total nitrogen (TN) (radj2 = 0.8, p < 0.01). Partial redundancy analysis (pRDA) showed that light condition accounted for the greatest variation of phytoplankton community composition, followed by TP and wind speed, as well as the interactions between TP and wind speed. Our study points to the additional importance of non-temperature effects of climate change on phytoplankton community dynamics in Lake Taihu.
Highlights
Phytoplankton play essential roles in aquatic food webs and global biogeochemical cycles [1]
Because the underwater light climate depends on both incident light and the transparency of the water column [38], which was estimated by Secchi depth (SD), the product of these two variables has been used as a simple proxy for the under-water light condition
The results showed that, along with wind speed and light condition, total phosphorus (TP) played an important role on spring phytoplankton community dynamics in Lake Taihu from 1997 to 2016 (Fig 4b), while total nitrogen (TN) did not show significant relationships with phytoplankton biovolume or community variation
Summary
Lake Taihu is a shallow, eutrophic, subtropical lake (30 ̊5504000–31 ̊3205800 N and ̊5203200– ̊3601000 E) located in the Changjiang (Yangtze) Delta, one of the most industrialized and densely populated regions in China. Since the 1980s, rapid economic development in the Lake Taihu basin has resulted in increasing levels of nutrients and other pollutants discharged via tributaries to the lake. Rapid water quality deterioration, accelerating eutrophication, and nuisance algal blooms (Microcystis spp.) have occurred regularly since the early 1990’s [34, 35]. Since prior studies have noted that both nitrogen and phosphorus overenrichment were responsible for blooms in Lake Taihu [35,36,37], total nitrogen (TN) and total phosphorus (TP) were included in our study. Because the underwater light climate depends on both incident light and the transparency of the water column [38], which was estimated by Secchi depth (SD), the product of these two variables has been used as a simple proxy for the under-water light condition
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