Effects of temperature increase and nutrient enrichment on phytoplankton functional groups in a Brazilian semi-arid reservoir

Abstract

Aim Our study aimed to evaluate changes in the phytoplankton functional groups brought about by increases in temperature and nutrients predicted by the Intergovernmental Panel on Climate Change (IPCC) scenario for semi-arid regions. Methods Two experiments were performed, one in the rainy season and another in the dry season. The nutrient enrichment was based on the annual mean values (August 2012-August 2013) of soluble reactive phosphorus and nitrate verified in the reservoir. The microcosms were exposed to two different temperatures, the five-year average of air temperature in the reservoir (control) and 4°C above the control temperature (warming). The experiment was conducted over 12 days; every three days water samples of approximately 60 mL in volume were taken from the reservoir for chemical and phytoplankton analysis. All species were classified by Reynolds Functional Groups (RFG). Results The functional groups H1, X1, LO and S1 were the most representative in both seasons (rainy and dry). Our results showed that bloom-forming cyanobacteria, in particular the species of functional groups H1 and M, commonly reported in reservoirs in semi-arid regions of Brazil, were not significantly benefited by the warming and nutrient enrichment. The recruitment of other blue-green species, as well as diatoms and green algae, could be observed. Conclusions The effects of warming and/or nutritional enrichment can change the structure of the phytoplankton community. However, as not expected as the pessimist scenario, in our study the bloom-forming phytoplankton functional groups did not show changes in relative biomass. Instead, the recruitment of diatoms and green algae currently found in enriched environments was verified, specifically in the rainy period, when nutrient dilution typically occurs.

Abiotic factors driving cyanobacterial biomass and composition under perennial bloom conditions in tropical latitudes

“…In a previous microcosm experiment with samples from one of the eutrophic lakes in this study (Boq. Parelhas), bloom-forming cyanobacterial abundance was not favored in the warmer and nutrient-enriched treatment (de Souza et al, 2018). This may indicate that temperature is not a main driver of phytoplankton assemblage in tropical semiarid lakes, likely because temperatures are already optimal and, thus, non-limiting.…”

Analysis of Degradation Processes in Reservoirs Based on Remote Sensing Data

“…Despite numerous studies concerning eutrophication, algae blooms and overgrowing, there is still no knowledge as to which factor determines degradation the most. It may be determined by geographical location (González-Márquez et al, 2018), natural processes , hydro-meteorological conditions (Souza et al 2018), land use and state of wastewater management in the basin (Tang et al, 2019), sediments deposition (Fuska et al, 2017), or water quality in rivers inflowing to the reservoirs (Yu et al, 2019). On the basis of the cluster analysis (CA), it was confirmed that multi-factors affecting the increased concentration of algae blooms or changes of overgrowth areas are different in each water body.…”

Analysis of Degradation Processes in Reservoirs Based on Remote Sensing Data

“…Despite numerous studies concerning eutrophication, algae blooms and overgrowing, there is still no knowledge as to which factor determines degradation the most. It may be determined by geographical location (González-Márquez et al, 2018), natural processes (Liu et al, 2019), hydro-meteorological conditions (Souza et al 2018), land use and state of wastewater management in the basin (Tang et al, 2019), sediments deposition (Fuska et al, 2017), or water quality in rivers inflowing to the reservoirs (Yu et al, 2019). On the basis of the cluster analysis Fig.…”