Abstract
Recent studies have investigated the impact of climate change on aquatic environments, and Chlorophyll-a (Chl-a) concentration is a quick and reliable variable for monitoring such changes. This study evaluated the impact of rainfall frequency as a diluting agent and the effect of increased temperature on Chl-a concentrations in eutrophic environments during a bloom of cyanobacteria. This was based on the hypothesis that the concentration of Chl-a will be higher in treatments in which the rainfall frequency is not homogeneous and that warmer temperatures predicted due to climate change should favor higher concentrations of Chl-a. The experiment was designed to investigate three factors: temperature, precipitation and time. Temperature was tested with two treatment levels (22°C and the future temperature of 25°C). Precipitation was tested with four treatments (no precipitation, a homogeneous precipitation pattern, and two types of concentrated precipitation patterns). Experiments were run for 15 days, and Chl-a concentration was measured every five days in each of the temperature and precipitation treatments. The water used in the microcosms was collected from a eutrophic lake located in Central Brazil during a bloom of filamentous cyanobacteria (Geilterinema amphibium). Chl-a levels were high in all treatments. The higher temperature treatment showed increased Chl-a concentration (F=10.343; P=0.002); however, the extreme precipitation events did not significantly influence Chl-a concentrations (F=1.198; P=0.326). Therefore, the study demonstrates that future climatic conditions (projected to 2100), such as elevated temperatures, may affect the primary productivity of aquatic environments in tropical aquatic systems.
Highlights
The study of global climate change has attracted interest from the scientific community since the 1970s (e.g., Kopec, 1971)
This study evaluated the impact of rainfall frequency and increased temperature on chlorophyll-a concentrations in eutrophic environments during a bloom of cyanobacteria
Increased temperature caused a significant increase in Chl-a concentrations, but precipitation did not cause any significant difference in Chl-a concentrations (Figure 3)
Summary
The study of global climate change has attracted interest from the scientific community since the 1970s (e.g., Kopec, 1971). Experimental and whole lakes studies have shown that climate change (e.g. extreme events and warming) can affect aquatic tropical environments by modifying their geochemistry (Roland et al, 2012), altering species composition and functional groups (e.g. Costa et al, 2015), or increasing cyanobacterial dominance (Kosten et al, 2012). This study evaluated the impact of rainfall frequency and increased temperature on chlorophyll-a concentrations in eutrophic environments during a bloom of cyanobacteria This was based on the expectations that: i) the intensity of rainfall in a short period of time would increase chlorophyll-a concentrations in the treatments with the most homogeneous precipitation conditions, and ii) the warmer temperatures predicted due to climate change should favor higher concentrations of chlorophyll-a
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