Old Bacteria Create New Beach Problems

"We have experienced some high counts of certain types of bacteria and the counts weren't going down .... we had to investigate what could possible be causing it and eliminate all the normal things and none of those things were occurring ...  and so we had to do a deep dive "

— Jacqui BeeBe 

Town Administrator, Eastham, MA

What happened at Cooks Brook and South Sunken Meadow Beaches in Eastham?

On Eastham's bay side beaches, routine beach monitoring identified high counts of enterococcus bacteria - but none of the usual suspect such as animal waste, septic, or runoff accounted for it. The counts remained high, the beaches remained closed, and the mystery grew. Eventually the town's research found the source: ancient cedar trees and ancient peat exposed by erosion. As the beach elevation dropped, a darker denser material appeared ... a layer of ancient peat. Once exposed, the centuries-old layer released centuries-old bacteria into the water.

Has this happened before?

While contamination from ancient bacteria is not common, in certain coastal configurations it can happen. It turns out these Cape Cod bay beaches have the right attributes and as the coast rises and lowers with the seasons and the weather at some times the old layer emerge. Town health agent Hillary Greenberg-Lemos says Eastham also saw this happen in the 1980s and 1990s.

Should we worry about ancient bacteria?

This exposure to ancient peat and it embedded bacteria is a natural phenomenon. The health risk takes the form of gastrointestinal illness and comes from ingesting the water, ie, if you don't drink it you are probably OK. Health agent Greenberg-Lemos also cautions aainst exposing open cuts or wounds to the contaminated water.

Is the beach safe now?

Eastham's bay beaches re-opened in August after six days of safe testing, showing they were no longer contaminated by ancient bacteria.

In general, how do I know any Cape Cod beach is safe from bacteria?

• The Commonwealth of Massachusetts keeps a current list on its website, identifying the most recent beach closings by town.
• Barnstable County also posts notices and offers a searchable Cape and Islands test list.
• The Association to Preserve Cape Cod monitors freshwater cyanobacteria outbreaks with a graphical map and an alert email list.

• Learn more about the 2023 Cape Cod beach closure in this Lower Cape News report.
• Learn more about cyanobacteria pond closures in this 2022 Lower Cape News video.