Effects of global climate change on chlorophyll-a concentrations in a tropical aquatic system during a cyanobacterial bloom: a microcosm study

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 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.Keywords: extreme events, Geitlerinema amphibium, primary productivity, temperature. o monitoramento de ambientes aquáticos. O objetivo do presente estudo foi avaliar o impacto da frequência da precipitação e do aumento da temperature na concentração de Clo-a em um ambiente aquático eutrófico durante um período de floração de cianobactéria. As hipóteses para o presente trabalho: i) A concentração de Clo-a será maior em tratamentos em que a frequencia de precipitação não é homogênea, e ii) Temperaturas mais quentes devem promover aumento na concentração de Clo-a. Foi utilizado um desenho experimental com três fatores: Precipitação, temperature e tempo. A temperature foi avaliada em dois tratamentos (22°C e a temperatura futura de 25°C). A precipitação foi avaliada em quatro tratamentos (ausência de precipitação, precipitação homogênea, e dois tipos precipitação concentrada). O experimento foi desenvolvido por 15 dias e a concentração de Clo-a foi mensurada a cada cinco dias para cada tratamento. Os níveis de Clo-a foram elevados em todos tratamentos, além disso, a concentração de Clo-a foi maior em tratamentos mais aquecidos (simulando cenário futuro) (F=10.343; P=0.002); entretanto, os eventos extremos de precipitação não demonstraram influência na concentração de P=0.326). Portanto, o presente trabalho demonstrou que as c...

The Variability of Surface Chlorophyll-a in Rawa Pening Lake within Five-Month Observations

“…At the same time, the rainfall shows an enhancement during November-December 2020, then followed by a decline in January 2021 (Figure 2). It is likely that the increase of surface chlorophyll-a was due to the elevation of river flow volume and/or surface runoff that carried nutrients to the lake (Moura et al, 2017;Maslukah et al, 2021;2022). There are 16 rivers that empty to Rawa Pening Lake and the dissolved nutrients and organic matter can be factors affecting the concentration of surface chlorophyll-a (Filstrup and Downing, 2017; Zhang et al, 2021).…”

Influence of Riparian Forest and Temperature on Primary Production of Tropical Streams

“…The impact of climate changes on water quality increases from groundwater via head-water streams, rivers, lakes, estuaries, and coastal water (Rozemeijer et al, 2021). A microcosm experiment on eutrophication in tropical aquatic ecosystems also found a positive relationship between temperature and chlorophyll-a concentration (Moura et al, 2017). In rivers, warming of 1.5°C can increase the GPP (Gross Primary Production) from 7% to 9%.…”