Properties of exopolymeric substances (EPSs) produced during cyanobacterial growth: potential role in whiting events
<p>Extracellular polymeric substances (EPSs) are an important organic carbon reservoir in many pelagic and benthic environments. The production of EPS is intimately associated with the growth of phyto- and picoplankton. EPS plays a critical role in carbonate precipitation through the binding o...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-08-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/20/3165/2023/bg-20-3165-2023.pdf |
| Summary: | <p>Extracellular polymeric substances (EPSs) are an important organic carbon reservoir in many pelagic and benthic environments. The production of EPS
is intimately associated with the growth of phyto- and picoplankton. EPS plays a critical role in carbonate precipitation through the binding of
cations and by acting as a nucleation site for minerals. Large-scale episodes of fine-grained calcium carbonate precipitation in the water column
(whiting events) have been linked to cyanobacterial blooms, including of <i>Synechococcus</i> spp. The mechanisms that trigger these precipitation
events are still debated. We pose that the cyanobacterial EPS, produced during exponential and stationary growth phases, plays a critical role in the
formation of whitings. The aim of this study was to investigate the production of EPS during a 2-month cyanobacterial growth, mimicking a
bloom. The production and characteristics of EPS were examined in different growth stages of <i>Synechococcus</i> spp. using various techniques
such as Fourier transform infrared (FT-IR) spectroscopy as well as colorimetric and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) assays. We further evaluated the potential role of EPS in carbonate precipitation through
in vitro-forced precipitation experiments. EPS produced during the early and late stationary
phase contained a larger amount of negatively charged groups than present in EPS produced during the exponential phase. Consequently, a higher
<span class="inline-formula">Ca<sup>2+</sup></span>-binding affinity of the stationary-phase EPS led to the formation of a larger amount of smaller carbonate minerals
(<span class="inline-formula"><</span> 50 <span class="inline-formula">µm</span>) compared to crystals formed in exponential-phase EPS, which were less abundant and larger (<span class="inline-formula">></span> 50 <span class="inline-formula">µm</span>). These
findings were used to establish a conceptual model for picoplankton-bloom-mediated <span class="inline-formula">CaCO<sub>3</sub></span> precipitation that can explain the role of EPS in
whitings.</p> |
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| ISSN: | 1726-4170 1726-4189 |