Evaluation of Size Structure in Freshwater Cyanobacterial Populations: Methods to Quantify Risk Associated with Changes in Biomass and Microcystin Concentrations

Abstract

Cyanobacterial populations in surface waters, including drinking water supplies and recreational waters, represent an ever present challenge for resource managers. As communities continuously respond to external and internal processes, dynamic profiles of composition, dominance, growth and toxigenicity emerge. In this study measures of size structure and biomass, quantified using light microscopy and fluorometry, were used to estimate microcystin concentrations through linear regression analysis. Toxigenic profiles using cyanobacterial biomass were developed for lakes dominated by Microcystis spp. and Dolichospermum spp., influenced by both genus-specific pigment concentrations as well as microcystin concentrations. Community composition (Log %MIC) and biomass were used to describe microcystin concentrations in mixed assemblages, where composition was the first input variable. The accessory photopigment phycocyanin was used to describe the linear relationship between the daily growth and net microcystin production rates in the bloom-forming Microcystis spp. samples, suggesting that this size-fractionated sample may provide indications of potential toxigenicity in the whole lake water sample. Future investigations using fluorometric evaluation of cyanobacterial populations could provide additional applications and metrics for use by resource managers to quantify risk association with elevated cyanotoxin concentrations.

Isolation of Picocyanobacteria (Order <i>Synechococcales</i>) and Occurrence of the Cyanotoxin Anatoxin-A in a Shallow Mesotrophic Pond

“…[(p + 1)/ (n − p − 1)] where n = number of observations, p = number of variables (including the constant) were examined. Cyanobacterial biomass daily net growth rates (µ•d −1 ) were calculated using phycocyanin (PC) concentrations or phycoerythrin (PE) concentrations as previously described [1].…”

“…Cyanobacteria are known to be a diverse and widely distributed group of bacte-ria that occupy a wide range of ecological niches. Their populations can be described using cyanobacterial accessory pigments and size-structure analysis [1] where cell size and organization are important parameters. The cyanobacteria produce secondary metabolites that have been shown to be toxic to various receptors, commonly termed cyanotoxins, making them a threat to human and ecological health.…”

Isolation of Picocyanobacteria (Order <i>Synechococcales</i>) and Occurrence of Cyanotoxins (Anatoxin-a) in Saline Microhabitats at Martha’s Vineyard, MA

“…Analysis of cyanobacterial accessory pigments PC and PE have been used in marine environments to aid in the classification to species level [2] [14]. The range of PC concentrations (Table 1) for our samples was similar to those previously observed for Dolichospermum spp., from freshwater mesotrophic ponds [3] [7] that were confirmed using light microscopy. Dolichospermum sp.…”

“…Picocyanobacteria are known to be a diverse and widely distributed group of cyanobacteria that occupy a wide range of ecological niches including freshwater, brackish and marine microhabitats [1] [2]. In general, cyanobacterial populations can be described using photosynthetic accessory pigments and size-structure analysis [1] [3] to provide detailed descriptions of these populations. The picocyanobacteria can produce secondary metabolites including microcystin (MC) and its variants and B-Methylamino-L-alanine (BMAA) [4] [5].…”

Monitoring indigenous microalgae using derivative spectrophotometry and comparison with M. aeruginosa and C. vulgaris

“…For example, cyanobacteria, commonly called blue-green algae, are prokaryotic organisms that flourish in ponds, lakes, wetlands, and other surface waters. Cyanobacteria algal blooms need to be consistently checked during the summer months as they can pose a serious threat to water quality, ecosystem stability, and public health through toxin production (Leland et al 2019). Due to the rapid increase in cyanobacteria blooms caused by water pollution and climate change, they have become the recent focus of scientific research to develop real-time analytical tools for early detection and monitoring.…”