The Science Behind The Bloom

posted Feb 2, 2018, 3:02 PM by Joseph Bickard

“The Science Behind The Bloom”

Lorraine Glowczak and Rosie Hartzler

Published in Windham Eagle, February 2, 2018

The Windham Town Council held a special meeting on Tuesday, focused on the Picocyanobacteria (Pcy ) bloom that has recurred in Highland Lake for the past 4 summers. 

Don Kretchmer, DK Water Resource Consulting (Wolf boro, NH) presented an overview of how lakes work, and then launched into the topic “Why the picocyanobacteria bloom in Highland Lake, and Why now?

Kretchmer explained that there have been no other documented instances of this type of bloom in New England.  Many factors are believed to contribute to the bloom including:  lake chemistry, food chain dynamics, erratic weather , climate change, agriculture, erosion and runoff from properties and roads within the water shed.

The primary driver of the Pcy  bloom is Phosphorus (P).  While P is a naturally occurring element in the soil, when soil is disturbed during development, P is released.  Then when it rains,  P is transported via runoff into Highland Lake.  P has been accumulating in HL for decades.  In the late 90’s P levels in HL were increasing as water clarity was decreasing, causing the DEP to list HL as impaired.  A massive effort and almost a $1 million was invested in a variety of projects around HL to reduce runoff and thereby reduce the P in HL. 

In 2010, the lake showed signs of recovery, yet, P levels were hovering around the 10 Parts per billion mark – a measure by which the DEP determines the level that a lake is able to handle P without turning eutrophic (decreasing water quality often characterized by algae, increased plant growth, and lowered oxygen).  

However, in 2014, the Pcy appeared,  and scientists are still working on figuring out what this new and very troubling phenomenon means.  Some of the questions that are on the front burner:

1.     Does the Pcy take up Phosphorus from the sediments in the lake and then rise to the top creating the cloudy (under 2 meter Secchi disk) conditions?

2.    Are there dynamics in the food chain that accelerate the Pcy  bloom?

3.    Does the increasing numbers of alewives in HL contribute to the bloom?

4.    What is the specific species (genetics) of the Pcy?

It is a very perplexing issue.  But there is a developing concerted effort being organized for the testing protocol that will occur in HL during the 2018 season.  This effort will potentially include scientists from UMO, UNH, USM, Lakes Environmental Association in collaboration with the HLA.

Kretchmer emphasized that everyone in the water shed needs to step up to the plate in the effort to reduce P in HL.  “There are no scenarios  where increased P will make the situation better at HL.” Shoreline property owners obviously need to be very aware of the capacity for their property to buffer potential runoff.  However property owners located a distance from the lake need to also take a look at how their property may contribute to P runoff.

Finally, Kretchmer affirmed the  WTC for engaging with this information – for being proactive in responding to the challenges inherent in the bloom .  Due to all the previous work of the HLA water quality team,  there is a significant bank of data that shows what the lake used to be like, and what folks want to return to. 

Kretchmer was joined by DEP, Jeff Dennis in a lively interactive question and answer period with the council regarding specifics of the situation at HL.  It is clear that there is much more to learn, and much more to digest in the every developing process of discovery at HL.  

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