Improved water clarity and lower cyanobacteria levels after alum treatment
October 2026: Lake Massapoag water continues to be clearer, and have lower levels of cyanobacteria one year after the June 2025 alum (aluminum sulfate) treatment. Water clarity, measured by Secchi disk readings, and background levels of cyanobacteria (based on the levels of phycocyanin, a protein only found in cyanobacteria) were lower than in previous years (see below). This year did bring some transient, localized blooms, at Camp Everwood in July, and at several shoreline locations after the nor'easter storm at the end of September. These transient and localized blooms are likely due to external phosphorus loading.
The latest results are also posted on LMAC’s webpages for Cyanobacteria and Algae and Water Quality.
The latest results are also posted on LMAC’s webpages for Cyanobacteria and Algae and Water Quality.
| cyanobacteria_and_secchi_23-26.pdf |
LMAC tested dissolved aluminum levels; July levels were detectable but not a concern for swimming, as expected, and August levels were nondetectable (<0.01 mg/L). The table attached below shows the aluminum levels in the lake are much lower than drinking water standards for aluminum.
| total_aluminum_levels.pdf |
Explanation of LMAC's rationale for addressing internal phosphorus loading
LMAC documented key conditions in Lake Massapoag that support the need for inactivation of internal phosphorus loading in order to improve water quality and reduce cyanobacteria blooms:
1) Very low oxygen levels in the deep hole during the summer months
2) Blooms consist of Microcystis and Dolichospermum cyanobacteria
3) The sediment in the deep hole of Lake Massapoag contains a large amount of iron-bound phosphorus
1) Very low oxygen levels in the deep hole during the summer months
2) Blooms consist of Microcystis and Dolichospermum cyanobacteria
3) The sediment in the deep hole of Lake Massapoag contains a large amount of iron-bound phosphorus
| stm_alum_2025.pdf |
Detailed Explanation of Internal phosphorus loading from the sediment as a key driver in cyanobacteria blooms
Presentation by Ken Wagner*, PhD 2022 North American Lake Management Conference
* author of The Massachusetts Guide to Algae and Aquatic Plant Management
Presentation by Ken Wagner*, PhD 2022 North American Lake Management Conference
* author of The Massachusetts Guide to Algae and Aquatic Plant Management
Brief Explanations of Alum Treatment
| alum_fact_sheet.pdf |
| lake_massapoag_is_facing_a_critical_challenge.pdf |