A. Cyanotoxins in Maine Lakes

Morning Session – 8:30AM-10:30AM
Piscataquis/Sagadahoc Room (2nd floor)

Session Co-Chairs:

  • Linda Bacon/Patrick Lind (Maine Dept. of Environmental Protection)
  • Robin Sleith (Bigelow Labs)

Cyanotoxins are on the rise in Maine lakes. Numerous entities have been conducting research ranging from probabilistic-based and targeted surveys of microcystin concentrations in lakes across the state, to eDNA and qPCR studies. Several local lake organizations that heretofore never had to deal with harmful algal blooms, have found themselves dealing with this phenomenon. So, what have we learned over the last decade and, is it time to establish an official advisory process to inform lake users of risk when these toxins are found? This session will feature results from state agencies, universities and research institutions and, could wrap up with a panel discussion regarding how this information is best conveyed to the public, or, a discussion of pros and cons of using various testing methods.

Session Overview

Session Abstracts

Presenters are indicated in bold font.

Using eDNA tools to identify and quantify the phytoplankton taxa of a unique algae bloom

A pdf of this presentation is available. Please contact Sharon Mann with any questions.

Sharon L. Mann1 (student), Karen A. Wilson1, Robin Sleith2, Peter Countway2
1. University of Southern Maine, Department of Environmental Science and Ecology
2. Bigelow Laboratory for Ocean Sciences

In 2014-2017, Highland Lake, Maine, USA, experienced unusual phytoplankton blooms characterized by rapid bloom development and sustained poor water clarity (< 2 m Secchi depth) for 3-4 weeks, followed by sudden improvement in water clarity in mid-August. In 2018, the bloom was not as dense (minimum Secchi = 2.9 m), and only lasted for a few days, but showed the same pattern in water clarity. In 2018 we investigated possible triggers of the bloom, including the suspected presence of picocyanobacteria. Metabarcoding environmental DNA (eDNA) water samples offers a promising opportunity to monitor the relative abundance of nuisance algae blooms that are difficult to manually quantify such as picocyanobacteria (<2 µm). We processed 47 eDNA samples collected bi-weekly from July – October for 16S (cyanobacteria specific) and 18S (eukaryotic) rRNA gene diversity via high-throughput sequencing to investigate the relative dominance of bloom forming taxa. The green algae genera, Rhexinema, dominated the 18S phytoplankton (>50% reads Rhexinema) when the water transparency was lowest and a peak in chlorophyll-α was observed. The week following the lowest water transparency, Cyanobium spp. dominated the 16S bacterial community coincident with a local peak in phycocyanin, a pigment associated with cyanobacteria (>75% reads Cyanobium). Here we show that metabarcoding is a powerful tool to capture elusive species and the relative abundance of bloom forming taxa. One drawback to metabarcoding is that it does not capture absolute abundance and therefore may not correlate strongly to chlorophyll-α and Secchi disk transparency. Targeted qPCR methods offer a promising way to quantify cell density that might better correspond to common measures of water quality.

Collaborative efforts to find answers to Damariscotta Lake’s wicked cyanobacteria problems

A pdf of this presentation is available. Please contact Patricia Nease with any questions.

Patricia Nease1, Robin Sleith2, Peter Countway2
1. Midcoast Conservancy
2. Bigelow Laboratory for Ocean Sciences

Damariscotta Lake in Lincoln County, Maine is a unique environment that has had three consecutive Planktothrix outbreaks in August 2020, 2021 and 2022, and two Dolichospermum outbreaks in June and July of 2022. At roughly 4,700 acres, Damariscotta Lake has three distinct basins. Prior to 2022 only the Southernmost basin, the South Arm, had experienced cyanobacteria outbreaks; but in 2022 one outbreak of Dolichospermum was lake wide. Cyanobacteria problems in the lake are a concern for recreators, lakeshore property owners who utilize lake water for drinking and household water, and because Damariscotta Lake drains into the Great Salt Bay estuary and Damariscotta River estuaries, both of which are important sites for oyster aquaculture. Using a combination of quantitative PCR and toxin analyses, Midcoast Conservancy and partners at Bigelow Laboratory for Ocean Science monitored trends in cyanobacteria levels throughout Damariscotta Lake to better understand the dynamics and severity of the issue. Partnerships have made this work possible and been a benefit to the Damariscotta Lake community and the scientific rigor of this work.

The distribution of toxic Dolichospermum strains across Maine

A pdf of this presentation is available. Please contact Robin Sleith with any questions.

Robin S. Sleith1, Linda C. Bacon2, Peter D. Countway1
1. Bigelow Laboratory for Ocean Sciences,
2. Maine Department of Environmental Protection

Climate change and nutrient pollution in freshwater ecosystems have led to the increase in frequency of harmful cyanobacterial blooms. These blooms can contain toxic and/or non-toxic strains of cyanobacteria. Dolichospermum is one of the most common cyanobacteria causing blooms in Maine. In this study we survey 50 Maine lakes to determine the distribution of toxic and non-toxic strains of Dolichospermum across the state. We find multiple strains occurring in some water bodies, while others contain only a single strain. This information, combined with historical data, will help to determine the factors responsible for toxic strains occurring or dominating in lakes across Maine.

Microcystin concentrations in Maine Lakes

Linda Bacon1, Patrick Lind1, Tristan Taber2, Breana Bennett3
1. Maine Department of Environmental Protection
2. Lake Stewards of Maine
3. Maine Center for Disease Control and Prevention

Maine DEP has conducted both probabilistic and targeted monitoring to determine late summer concentrations of the cyanotoxin microcystin in Maine lakes. Probabilistic monitoring focused on lakes greater than 150 acres in surface area located in populated counties and townships; targeted time series monitoring included visits to known bloomers to gain insight into seasonal patterns and worst-case-scenario conditions. Microcystin production was the greatest in lakes that are known to support algal blooms, especially chronic bloomers. Data indicates that open water concentrations infrequently exceed EPA drinking water standards and do not exceed recreational standards, however shoreline algal scums may exceed both standards by orders of magnitude. In addition to sharing results, progress with respect to CDC’s establishment of a microcystin advisory or alert system based on these data will be presented. Microcystin testing using dipstick tests, ELISA test plates, and EPA’s BloomWatch program will be mentioned. Conditions unrelated to algal toxin exposure that can result in dog illness or death will also be reviewed.