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What You Should Know about Recreational Water Quality on Cape Cod this 4th of July Week

Every year, local and national news outlets cover water quality concerns as thousands of people flock to the beaches for what is inevitably one of the busiest weeks of the New England summer. We know some of those news stories can be anxiety inducing, so here’s the information you need to enjoy your July 4th week on Cape Cod knowing you are making healthy choices for yourself and your family.

Water Quality Monitoring Programs on Cape Cod

There are two entities on Cape Cod that consistently monitor beach water to inform the public about potential water quality concerns that could lead to negative health impacts. The Barnstable County Bathing Beach Monitoring Program performs weekly monitoring for fecal bacteria at marine and freshwater beaches, while the Association to Preserve Cape Cod (APCC) monitors freshwater ponds for cyanobacteria.

Sometimes, it can be difficult to understand the difference between these two very different micro-organisms, the factors that contribute to their presence in our water bodies, and the different monitoring techniques and protocols that are used to determine whether it’s safe for humans and animals to swim in the water.

Fecal Bacteria Monitoring

Barnstable County tests the water for two different types of fecal bacteria; Enterococcus in marine water, and E. coli in fresh water. It is important to note that these two bacteria are considered indicator organisms, which, as their name implies, are used to “indicate” the presence of conditions that have the potential to cause illness. Both organisms are found in the intestines of warm-blooded animals, including humans. Their presence in recreational waters suggests that other harmful organisms and viruses (called pathogens) might be present. If these pathogens are inadvertently ingested while swimming, they may cause a variety of diseases, the most common of which is a mild gastroenteritis with flu-like symptoms. This can be inconvenient and even dangerous, especially for those who are immunocompromised.

Stormwater runoff from rain is a dominant cause for elevated indicator bacteria levels. Runoff carries pollutants from roads and other paved surfaces directly to the surface water of beaches and ponds. Other possible causes of fecal contamination of recreation waters are animal wastes from pets and wild animals. Common waste observed on beaches can be from dogs, geese, ducks, seagulls, seals and fox.

Per Massachusetts Bathing Beach Regulations 105 CMR 445.000, towns are required to monitor all public and semi-public bathing beaches for fecal bacteria on a weekly basis during the summer season. Learn more about fecal bacteria monitoring at: Bathing Beach Water Quality – Barnstable County ( (scroll down to “About the Beach Monitoring Program”).

Cyanobacteria Monitoring

Cyanobacteria are a natural phenomenon that can occur in healthy ecosystems. Typically, however, its potential for overgrowth is kept in check by a balance of several different factors, one of which is nutrient availability. All animals and plants require nutrients to grow and thrive, but if an external force makes nutrients either scarce or overabundant–the balance is disrupted, and things can start to go wrong.

Here on Cape Cod, human activities–from fertilization to faulty septic systems–have introduced an overabundance of nutrients into the environment, which leads to an ecologically unhealthy condition called eutrophication (the process by which a water body becomes enriched in dissolved nutrients such as phosphates and nitrogen). The greater the nutrient availability, the more fuel for cyanobacteria (and other undesirable plant life) to grow and thrive. Global warming also plays a key role with warmer pond temperatures favoring cyanobacteria.

When discussing cyanobacteria, we often hear the term used interchangeably with harmful algae blooms (HABs) and toxic algae. There is, however, an important distinction to make: not all cyanobacteria is toxin producing. So while an overgrowth of cyanobacteria may have some aesthetic impact on a particular water body or even environmental implications, it may not be harmful to people and their pets. That said, a visual assessment alone is not enough to make a determination between toxic and non-toxic, so further analysis is required. And if you don’t know either way, it’s always best to conclude the following: WHEN IN DOUBT, STAY OUT.

The Association to Preserve Cape Cod (APCC) is a local non-profit environmental organization that proactively monitors Cape Cod’s ponds for cyanobacteria and, more specifically, the toxins they sometimes produce, using a predictive methodology called CyanoCasting. While this method provides useful information regarding cyanobacteria presence and abundance, it does not provide data regarding the existence or quantity of harmful toxins.

If APCC’s team, through the use of the above-described CyanoCasting method, determines that additional confirmatory toxin testing is warranted, the Barnstable County Water Quality Lab then performs toxin analysis via Environmental Protection Agency (EPA) Approved Method 546 for Surface Water Sampling. If toxins are found to be present in an amount considered to be harmful to humans and pets, an advisory will be issued by the local board of health to make the public aware that swimming could pose a risk of illness. For more specifics regarding the particulars of the monitoring program, please visit APCC’s cyanobacteria monitoring web page.

The Final Determination: Will I Know When it’s Unsafe to Swim at my Favorite Cape Cod Beach?

In most cases, yes! Barnstable County monitors over 350 beaches on Cape Cod WEEKLY, while the Association to Preserve Cape Cod monitors ponds routinely for cyanobacteria. Check out the resources we’ve provided above, look out for signage posted at the beach entrance, and if the water looks murky, green, or just all around unpleasant, remember the slogan “When in Doubt, Stay Out!”.

Happy July 4th Barnstable County!

Additional Resources

Beach Water Quality |

Frequently Asked Questions About Monitoring Water Quality at Beaches |

How to Safely Visit Oceans, Lakes, and Rivers | Healthy Swimming | CDC

Be Prepared for a Day at the Beach | Blogs | CDC

Beaches | US EPA