Green algal over cyanobacterial dominance promoted with nitrogen and phosphorus additions in a mesocosm study at Lake Taihu, China

Abstract

Enrichment of waterways with nitrogen (N) and phosphorus (P) has accelerated eutrophication and promoted cyanobacterial blooms worldwide. An understanding of whether cyanobacteria maintain their dominance under accelerated eutrophication will help predict trends and provide rational control measures. A mesocosm experiment was conducted under natural light and temperature conditions in Lake Taihu, China. It revealed that only N added to lake water promoted growth of colonial and filamentous cyanobacteria (Microcystis, Pseudoanabaena and Planktothrix) and single-cell green algae (Cosmarium, Chlorella, and Scenedesmus). Adding P alone promoted neither cyanobacteria nor green algae significantly. N plus P additions promoted cyanobacteria and green algae growth greatly. The higher growth rates of green algae vs. cyanobacteria in N plus P additions resulted in the biomass of green algae exceeding that of cyanobacteria. This indicates that further enrichment with N plus P in eutrophic water will enhance green algae over cyanobacterial dominance. However, it does not mean that eutrophication problems will cease. On the contrary, the risk will increase due to increasing total phytoplankton biomass.

Multi-year succession of cyanobacteria blooms in a highland reservoir with changing nutrient status, Guizhou Province, China

“…Inorganic nitrogen was another key factor for phytoplankton development. Previous studies suggest that moderate levels (0.3-0.8 mg L -1 ) of inorganic nitrogen are required for the growth and reproduction of Microcystis spp (Ma et al, 2015). In this study NH 3 -N was positively associated with Microcystis growth throughout the water column.…”

“…In this study water temperatures up to 28°C were important for Microcystis spp growth. Other studies have also shown that water temperature had an impact on cHABs (Ma et al, 2015). Nalewajko and Murphy (2001) noted that harmful cyanobacteria tolerate higher temperatures relative to other algae, while Okino (1973) commented that in several Japanese lakes Microcystis spp did not appear (germinate and develop) until the water temperature was >20°C.…”

“…A previous study has shown that biological and economic losses due to HABs were estimated at US$82 million annually in the United States and nearly US$813 million annually in Europe (Hoagland and Scatasta, 2006). Two contributors to cHABS, Aphanizomenon flosaquae Ralfs ex Bornet & Flahault and Microcystis spp have been correlated to increased nutrient inputs, especially phosphorus and nitrogen (Liqiang et al, 2003;Conley et al, 2009;Ma et al, 2015;O'Neil et al, 2013). Paerl and Huisman (2009) and Pick (2016) also attributed climate change (warmer temperatures) to changes in hydrological cycles and blooms.…”

Response of the photosynthetic activity and biomass of the phytoplankton community to increasing nutrients during cyanobacterial blooms in Meiliang Bay, Lake Taihu

“…Hence, on a short time scale, this method is not appropriate for the control of algal blooms with long durations and large spatial scales in northern bays (Duan et al, ; Qin et al, ). Previous studies have investigated the effects of increasing nutrients (Chen, Fan, Teubner, & Dokulil, ; Ma et al, ; Paerl et al, ; Xu et al, ), physical factors such as water temperature, wind waves, and light (Deng et al, ; Zhou et al, ) and microcystins (Li et al, ) on the growth of phytoplankton in cyanobacterial bloom periods in Lake Taihu through field monitoring and laboratory experiments. However, the differences and dynamics of the physiological photosynthetic activity of the phytoplankton community during cyanobacterial bloom formation have been largely overlooked and still lack adequate research, especially in natural communities.…”

“…Although the response of the total biomass of the phytoplankton community to nutrient additions has been well studied in hypereutrophic areas of Lake Taihu, such as Meiliang Bay, the internal interaction between algal population biomass and photosynthetic performance remains unclear. Moreover, recent studies have demonstrated that extremely high nutrient levels may result in the dominance of green algae over cyanobacteria in Lake Taihu (Ma et al, ). However, little is known about the differences between cyanobacteria and green algae activities during the bloom period.…”