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, 10 (2)

Algal Blooms and Cyanotoxins in Jordan Lake, North Carolina

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Algal Blooms and Cyanotoxins in Jordan Lake, North Carolina

Daniel Wiltsie et al. Toxins (Basel).

Abstract

The eutrophication of waterways has led to a rise in cyanobacterial, harmful algal blooms (CyanoHABs) worldwide. The deterioration of water quality due to excess algal biomass in lakes has been well documented (e.g., water clarity, hypoxic conditions), but health risks associated with cyanotoxins remain largely unexplored in the absence of toxin information. This study is the first to document the presence of dissolved microcystin, anatoxin-a, cylindrospermopsin, and β-N-methylamino-l-alanine in Jordan Lake, a major drinking water reservoir in North Carolina. Saxitoxin presence was not confirmed. Multiple toxins were detected at 86% of the tested sites and during 44% of the sampling events between 2014 and 2016. Although concentrations were low, continued exposure of organisms to multiple toxins raises some concerns. A combination of discrete sampling and in-situ tracking (Solid Phase Adsorption Toxin Tracking [SPATT]) revealed that microcystin and anatoxin were the most pervasive year-round. Between 2011 and 2016, summer and fall blooms were dominated by the same cyanobacterial genera, all of which are suggested producers of single or multiple cyanotoxins. The study's findings provide further evidence of the ubiquitous nature of cyanotoxins, and the challenges involved in linking CyanoHAB dynamics to specific environmental forcing factors are discussed.

Keywords: BMAA; North Carolina; SPATT; anatoxin-a; cyanobacteria; cyanotoxins; freshwater blooms; microcystin; water quality.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Map of Jordan Lake sampling sites. Biological, chemical and physical data were analyzed over a 6-year period (2011 to 2016) for sites A, B and C (red circles). Information over approximately 2 years (2014 to 2016) was available for an additional six sites (sites D through I, blue circles). Arrows indicate the three main rivers flowing into the lake. Map from snazzymaps.com.
Figure 2
Figure 2
Average cell densities for cyanobacteria (black circles) and microeukaryote phytoplankton (white triangles) and for Chl a concentration (white squares). Before October 2014, averages were calculated for sites A through C. After October 2014, averages were calculated for all nine sites. Note: all axes are log-transformed.
Figure 3
Figure 3
Cyanobacterial cell densities at each of the sampling locations (sites A through I are shown as panels A through I). Colors depict the six most abundant genera, and less abundant taxa are grouped as “Other”. Long-term sites A through C were sampled from January 2011 to December 2016. D, F, H and I were monitored from October 2014 to June 2016, while monitoring at E and G continued through December 2016. Vertical dashed lines separate years. Note, there are differing scales on the y-axes for A, C and E.
Figure 4
Figure 4
(A) MDS plot based on Bray–Curtis similarities for cyanobacterial communities as a non-metric multi-dimensional scaling (nMDS) plot by season (data from all years and stations combined). (B) Relative changes in cyanobacterial community composition shown along a month-to-month trajectory (site A in 2015). Stress values are reported in the top right corner of each plot.
Figure 5
Figure 5
Changes in (A) temperature, (B) NOx, (C) NH3 concentration and (D) Total Kjeldahl nitrogen (TKN):TP ratio averaged for each sampling event. Standard error bars are included. Vertical dashed lines separate years.
Figure 6
Figure 6
MDS plot showing Euclidian distances for environmental fingerprints by season. Parameters included in these analyses were temperature, NOx, NH3, TKN, TP and DO concentrations, TKN:TP ratios, pH levels and turbidity. The stress value is reported in the top right corner.
Figure 7
Figure 7
Weekly averages of meteorological and hydrological parameters: (A) precipitation; (B) wind speed; (C) PAR; (D) overall river flow. Vertical dashed lines separate years.
Figure 8
Figure 8
SPATT toxin values (columns) and toxin concentrations based on grab sampling (symbols) for (A) MCY, (B) CYN and (C) ANA for site E. SPATT toxin concentrations in ng toxin (g resin−1) d−1 are shown at the half-point of each deployment period. Grab samples are represented as µg toxin L−1 (filled symbols). Empty symbols along the x-axis indicate when toxin values fell below the LDL for each ELISA kit (LDLs shown as horizontal dashed lines originating from the secondary y-axes).
Figure 9
Figure 9
Seasonal averages for dissolved toxin concentrations based on (A) discrete sample analyses for sites A through G and (B) in-situ tracking (SPATTs) of MCY, ANA and CYN for sites E and G. Standard error bars are included whenever multiple samples tested positive. Note there are differing log-scales on the y-axes.

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