Response of microalgae to elevated CO2 and temperature: impact of climate change on freshwater ecosystems

Abstract

To estimate the combined effects of elevated CO2 and temperature on microalgae, three typical and worldwide freshwater species, the green alga Scenedesmus acuminatus, the diatom Cyclotella meneghiniana, and the cyanobacterium Microcystis aeruginosa, as well as mixes of these three species were continuously cultured in controlled environment chambers with CO2 at 390 and 1000 ppm and temperatures of 20, 25, and 30 °C. CO2 and temperature significantly affected the production of microalgae. The cell productivity increased under elevated CO2 and temperature. Although the green alga dominated in the mixed culture within all CO2 and temperature conditions, rising temperature and CO2 intensified the competition of the cyanobacterium with other microalgae. CO2 affected the extracellular polymeric substances (EPS) characteristics of the green alga and the cyanobacterium. Elevated CO2 induced the generation of humic substances in the EPS fractions of the green alga, the cyanobacterium, and the mixed culture. The extracellular carbohydrates of the diatom and the extracellular proteins of the cyanobacterium increased with elevated CO2 and temperature, while the extracellular carbohydrates and proteins of the green alga and the mixes increased under elevated CO2 and temperature. There were synergistic effects of CO2 and temperature on the productivity and the EPS of microalgae. Climate change related CO2 and temperature increases will promote autochthonous organic carbon production in aquatic ecosystems and facilitate the proliferation of cyanobacteria, which potentially changes the carbon cycling and undermines the functioning of ecosystems.

Influence of parasitic chytrids on the quantity and quality of algal dissolved organic matter (AOM)

“…The LM model showed that the FI of fDOM-2 was significantly positively correlated with diatom abundance (Table 2). It is well known that amino acids can be released by algal activity (Henderson et al 2008;Li et al 2016). The FI of fDOM-2 was also significantly positively correlated with bacterial abundance in the diatom treatment (Fig.…”

“…The fDOM-5 components were considered to be tyrosine-like materials (Cory and McKnight 2005;Yamashita et al 2010). Both could be released during algal activity (Li et al 2016;Yamashita and Tanoue 2003), and were good substrates for bacteria (Wetzel 2001;Pérez and Sommaruga 2006). Moreover, bacteria also release the extracellular polymeric substances (EPS) such as carbohydrates and proteins (Elliott et al 2006;Salama et al 2015).…”

Diatoms for Carbon Sequestration and Bio-Based Manufacturing

“…Both the diatoms, P. triconutum and N. ovalis , have been found to display the same compartmentation for isoprenoid biosynthesis, as previously found in higher plants, the red alga Porphyridium cruentum and the chrysophyte Ochromonas danica [ 160 ]. The extracellular carbohydrates of the diatom Cyclotella meneghiniana have been found to increase with elevated CO 2 and temperature [ 161 ]. Inlet pCO 2 have been found to enhance lipid production along with chitin formation in Cyclotella sp.…”

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

“…Experimental studies are therefore important tools to test the effects of climate change in aquatic ecosystem (see for example Li et al, 2016;Short et al, 2016). In fact, the majority of these experimental studies have been developed in temperate regions, and thus offer little insight about the impact of climate change in tropical aquatic ecosystems (see Roland et al, 2012).…”