A study on the relationship between metabolism of Cyanobacteria and chemical oxygen demand in Dianchi Lake, China

Abstract

Recent increases in concentrations of chemical oxygen demand (COD‐Cr) in Dianchi Lake, China, is an important factor affecting its water quality. Large volumes of cyanobacteria algae have also been recorded in this lake; its growth, distribution and metabolism are believed to directly or indirectly affect water quality. The relationship between metabolism of cyanobacteria and COD‐Cr in Dianchi Lake, and the causes of this relationship, are examined in this study. Results show that the increase of COD‐Cr concentration is closely related to the metabolism of algae, and that organic substances containing nitrogen and sugars, produced by metabolism, contribute to an increase of COD‐Cr to a certain extent. The characteristics of fluorescence spectra of dissolved organic matter (DOM) in the Waihai area of Dianchi Lake are similar to those of algae culture water, and their dominant substances are protein‐like substances. Algae release organic substances into water during its growth cycle and extracellular organic substances are mainly released during its normal growth and metabolism stages. Once algae cells enter the decline stage, internal organic matter is released during the dying and decomposition stages, resulting in a distinct increase of COD‐Cr. A high concentration of organic matter is present in Dianchi Lake sediments, dominated by native organic matter predominantly derived from aquatic plants and plankton. This finding indicates a potential long‐term risk of organic pollutants being released from dead algae cells into the lake. Practitioner points There is a distinct positive correlation between COD‐Cr and Chl‐a concentration in Dianchi Lake. Organic substances containing nitrogen and sugars produced by algae metabolism contributed to COD‐Cr. The cells die and decompose organic matter content in the water substantially increases, resulting in a distinct increase of COD‐Cr. Weight >20 kDa are mainly released into the water body during the decomposition of algae cells after mortality. Organic matter content in the water substantially increases, resulting in a distinct increase of COD‐Cr.

Biofilms for Turbidity Mitigation in Oil Sands End Pit Lakes

“…The Biofilm20 jars had 11% lower DO on average than the Biofilm10 jars and had COD and TOC concentrations that were 11% and 12% higher on average, respectively, in comparison to that of the Biofilm10 jars. These results are consistent with the trend noted by He et al [ 44 ], in which COD and TOC concentrations were highest during the stage of algae death and decay, likely due to a rapid release of intracellular organic matter into the surface water. Based on LIVE/DEAD staining of Biofilm10 ( Figure 1 A) and Biofilm20 ( Figure 1 D), it appears that Biofilm20 contained more dead cells than Biofilm10, though the biofilm matrix impacted the quality of these images.…”

“…Measurements of DO and TOC were also higher in the Biofilm10 and Biofilm20 jars, which is expected given the presence of algal communities in the biofilms that generate DO through photosynthesis and TOC through cell metabolism (further details in Section 3.1.2 ) [ 44 , 45 ]. The higher pH in the Biofilm10 and Biofilm20 surface water in comparison to the No Biofilm surface water is consistent with algae in biofilms consuming carbon dioxide (CO 2 ) during photosynthesis.…”

Treatment and Re-Use of Raw Blackwater by Chlorella vulgaris-Based System

“…The initial increase was mostly present in less diluted BW (50% and 30%) with the longest lag phases (Figure 1). The reason can be attributed to the algae cell death as a response to the initial extreme conditions and thus to the release of cellular nutrients into the medium [42]. The initial NH 4 -N and PO 4 -P increase may be explained by the degradation of complex organic compounds in the BW due to bacterial activity naturally present in BW, especially in the tests with high BW dilutions with no or very little starting COD and TN increase.…”

Effects of Malachite Green on the Microbiomes of Milkfish Culture Ponds

“…Killberg-Thoreson et al (2020) demonstrated that the magnitude of uptake rates by bloom of Alexandrium monilatum generally follow the pattern of ammonium (NH 4 + ) > nitrate (NO 3 − ) > urea > amino acids > nitrite (NO 2 − ) [48]. The relationship between the metabolism of cyanobacteria and chemical oxygen demand (COD) in Dianchi Lake and the causes of this relationship were examined in the study by He et al (2019) [49]. Organic substances containing nitrogen and sugars lead to an increase in COD to a certain extent.…”