Local NPR for the Cape, Coast & Islands 90.1 91.1 94.3
Play Live Radio
Next Up:
0:00 0:00
Available On Air Stations

Why Are Potentially Dangerous Algae Blooms Spreading Through Cape Ponds?

Santuit Pond in Mashpee, taken August 21, 2019. The pond is experiencing significant impacts from a blue-green algae bloom that can pose serious public health risks.
Charles Culbertson

Many of us like to swim in any one of the thousand-odd ponds on the Cape. But around the country, blue-green algae blooms have overtaken many of these waterbodies and exposure to the blooms can cause health problems in humans and pets that range from headaches, fevers, organ damage, even death. So how big is this problem on the Cape right now? 


What are cyanobacteria blooms and why are they of concern? 

Cyanobacteria, in normal amounts, are a plant species that live in freshwater ponds around the country. On the surface, they cast an opaque blue-green tint and usually don’t pose any problems.


But when the system gets out of balance in freshwater ponds, cyanobacteria grow in abundance and can produce really dangerous toxins, the most common and concerning of which are called microcystins.


When people or animals ingest--or are exposed to--these toxins in certain high concentrations, they can experience anything from skin irritations or headaches, to blisters around the mouth, even major liver damage.  


This month, three dogs in North Carolina and one dog in Georgia have died after swimming in local ponds. Their deaths have been linked to toxic cyanobacteria blooms.   


How prevalent is this issue on the Cape? And where should we be looking for it? 


There are over 1,000 fresh water ponds on the Cape, and unfortunately, only around 50 ponds are being monitored for toxic blooms, so we don’t know the full scope of the problem. That’s partly why local organizations like the Association to Preserve Cape Cod (APCC) is ringing the alarm on this issue. 


They monitor more than two dozen ponds and have found cyanobacteria blooms all across the Cape. Bryan Horsely, the restoration technician at APCC says there’s really no geographical pattern. These blooms are everywhere. 


Why are these blooms happening to begin with? Is there a climate change connection here? 


A combination of climate change, natural development, and human activity is driving this problem.  


Cyanobacteria blooms prosper when they have access to warm water and nutrients like phosphorous. 


Warming waters are a consequence of climate change, and our ponds are no exception to that. 


Also, septic systems and fertilizer sprays provide a steady stream of phosphorous and other nutrients that seep into the groundwater and find their way into the ponds. 


This is aided by the fact that the Cape is built on such sandy soil that isn’t very good at sequestering groundwater. 


Andrew Gottlieb, the executive director of APCC said unless we act fast, these factors will only get worse. 


“Every pond in the Cape is affected by the impacts of climate change and most ponds to some degree are affected by the nutrient enrichment that's happening in the groundwater,” Gottlieb said. “Those two factors being the two that are driving this phenomenon represent a threat to ponds up and down the Cape. I don't think any particular pond should feel that they are immune from these effects.” 


Are there solutions to this problem?


This can be fixed. This is a human-caused problem, so there’s a human-driven solution.


First, individuals can lay off the fertilizers. That will help reduce the amount of phosphorous that these blooms feed on. 


In the long term, Gottlieb says the Cape needs to reduce its reliance on septic systems and upgrade to something that prevents phosphorous from seeping so easily into the groundwater. 


That project would likely require towns to install sewer systems, which is time consuming and expensive, but, Gottlieb says, goes a long way.  


In the meantime… should people avoid swimming?  


This is a really serious issue with really serious consequences. 


Harold Walker, a professor of environmental engineering at Worcester Polytech Institute, says people don’t need to swear off swimming completely, but they need to be informed.  


He says we’ve reached a point of high enough risk for ponds that the standard shouldn’t be “is this unsafe?” but rather, “is there proof that this IS safe?” 


To learn more about the toxicity status of individual ponds, information can be found at www.apcc.org/cyano.  

Eve Zuckoff covers the environment and human impacts of climate change for CAI.