In the tropical and subtropical reservoirs, the control of primary production is generally exerted by bottom-up processes, especially represented by the control by P and N compounds, and by the hydrological dynamics. Moreover, compared with natural lakes in the temperate regions, top-down control of phytoplankton in tropical regions tends to be less important due to a general smaller size of zooplankton and to the high predation exerted by continuously reproducing omnivorous fish. Given these conditions, situations characterized by periods of low water renewal coupled with high availability of nutrients, can represent a serious hazard, favouring the potential development of nuisance species belonging to cyanobacteria, and compromising the exploitation of the reservoirs. In this contribution, we will evaluate the influence of the hydrological regime and nutrient temporal dynamics on the development of phytoplankton and cyanobacteria in the sub-tropical Hongfeng reservoir (Southwestern China, Guizhou Province, 26.5°N). The reservoir has a surface area of 57.2 km2 and a volume of 6.01×108 m3. Since 2000, its major function changed from electricity generation to drinking water supply. From January to May, the water level of the reservoir was stable, oscillating between 1232 and 1234 m a.s.l. (low level). During June, the lake increased its level around 1238-1239 a.s.l. between July and December (high level). The high influx of water, which contributed to prevent the formation of strong temperature gradients, was followed by a decrease in TP concentrations from the low level (ca. 35 μg P/L) to the high level (25 μg P/L) period. At the same time, the phytoplankton community showed a decrease of biovolumes and a shift from cyanobacteria (mostly Oscillatoriales) and large diatoms to specific Morpho-Functional Groups belonging to small chlorophytes (small Naked and Gelatinous chlorophytes) and Small Centric diatoms. Overall, the increasing water influx favoured a decrease of the large species, in favour of smaller species. Changes at the species and at higher taxonomical levels were investigated by applying NMDS ordination techniques coupled with vector fitting. In particular, the phytoplankton sample configurations were significantly linked to the fluctuations of the water level and mean water temperature and, partly, TP. Overall, the results demonstrated a clear negative link between phytoplankton development and increase in the water level. High influx of water and turbulence levels after spring contributed to control, despite medium-high concentrations of TP, the development of high phytoplankton and cyanobacterial biomasses. This works clearly demonstrates the strong implications originating from the adoption of different water discharge management options on the control of phytoplankton dynamics and potential nuisance species.
|Citation:||Li, Q.; Ou, T.; Xiao, J.; Wang, J.; Chen, J.; Salmaso, N. (2016). Hydrological dynamics affect the development of phytoplankton in a large subtropical reservoir (Hongfeng, Southwestern China). In: XXXIII Congress of the International Society of Limnology, Torino, July 31, 2016 – August 5, 2016: 348-349. url: http://www.sil2016.it/files/3214/7272/2565/33rd_SIL_Congress_2016_-_Book_of_Abstracts.pdf handle: http://hdl.handle.net/10449/35849|
|Organization unit:||Department of Sustainable Agro-ecosystems and Bioresources # CRI|
|Authors:||Li, Q.; Ou, T.; Xiao, J.; Wang, J.; Chen, J.; Salmaso, N.|
|Title:||Hydrological dynamics affect the development of phytoplankton in a large subtropical reservoir (Hongfeng, Southwestern China)|
|Scientific Disciplinary Area:||Settore BIO/07 - Ecologia|
|Keywords ENG:||Hongfeng reservoir|
|Appears in Collections:||03 - Conference object|