The overarching objective of this project was to verify the methods necessary to isolate and analyze the picocyanobacterial populations within a given waterbody. Picocyanobacteria are found in both marine and freshwater systems (Howard et al. 2017, Smith et al. 2020, Ivey, et al., 2020) and have been shown to produce cyanotoxins (Gin et al., 2021). The “picos” have been the focus of intensive research at the UNH-CFB to verify their toxin production and role in exposure pathways including food webs and aerosols (Murby and Haney, 2015, Langley, 2019, McQuaid, 2019, Carter, 2022), where they have been operationally defined as that portion of the cyanobacterial population which is less than 5µm in size (Langley, 2019). The “picos” as a community have been shown to be a sensitive to perturbances in the environment (Ivey et al., 2020) such as those associated with stochastic events (stormwater inputs), potentially serving as a sensitive ecological indicator.

Specifically, this project collected various particulate size fractions, including whole lake water (WLW), less than 50 microns (<50 µm) and less than 5 microns (<5 µm) as well as additional filtrates including less than 10 microns (<10 µm), less than 5 microns (<5 µm) and less than 0.2 microns (<0.2 µm or dissolved), being shown as Figure 1. For ease of reference, filtrates will be referred to as the “Water Method” and particulates will be referred to as the “Filter Method” throughout the remainder of this document.

The objectives of the project were as follows:

a. Document changes in (pico)cyanobacterial populations and cyanotoxins in response to stormwater discharges,

b. Document any limitations and/or benefits to collecting (pico)cyanobacterial samples as particulates using the “filter method” as compared to the existing “water method”,

c. Recommend metrics that could be used to evaluate exposure potential to (pico)cyanobacterial cyanotoxins across a broad range of habitats, and

d. Evaluate the ease of use of these methods across a broad range of end-users.