Assateague Coastal Trust uses Swim Guide, looks for safe levels in ocean, creeks

(Aug. 30, 2019) Assateague Coastal Trust has been keeping an eye on the bacteria levels in the bays and ocean this year, especially after a Vibrio infection scare earlier in June, with the help of Swim Guide, an internationally used website.

Swim Guide delivers free real-time water quality information for over 7,000 beaches, lakes, rivers, and swimming holes in Canada, the U.S., Mexico, the Bahamas, Ireland, France, New Zealand, and Australia. The app was founded by Lake Ontario water staff in Toronto, Canada, over 10 years ago.

“Everywhere you go, you can find out if the water is safe or not, if the state or the county is monitoring water quality on a river or lake,” Coastkeeper Kathy Phillips said. “That information is publicly available. When people start using swim guide, they’re thinking more about what is in the water, asking, ‘Is it safe for my kids to go in swimming?’”


Assateague Coastal Trust’s Communications Manager Billy Weiland collects a water sample.

ACT’s Assateague Coastkeeper currently posts weekly Swim Guide reports for 29 sites along the Maryland and Virginia Eastern Shore ocean beaches and water recreation areas in Ayers Creek, Isle of Wight Bay, Assawoman Bay, St. Martin River, Herring Creek and Turville Creek.

“This data is based on using the IDEXX Quantitray 2000 analysis system for Enterococci,” Phillips said. “We test for Enterococci instead of E.coli because our bay water is brackish, not fresh water. The results are an MPN (Most Probable Number) of enterococci CFUs (colony forming units) in a 100ml sample.  

“Weekly variables include amount of rainfall and how often, tides, water temperature, air temperature, turbidity in the water and what litter or pollutants are being carried by rainwater through stormwater systems in to the Bays and creeks,” she continued.   

The organization has been using Swim Guide for the past eight years. As of earlier this week, 19 of the 29 locations have been determined to be safe for swimming. This year, the program was run by Communications Manager Billy Weiland and intern Casey King, a graduating senior from Salisbury University.

The site has seen a lot more views this year, especially after a young boy was diagnosed with Vibrio, a bacterium found in brackish water, which can cause gastrointestinal issues as well as skin infections.

“I’m pleased with the visitation numbers, the viewing numbers that we have so many more people using the app this summer,” Phillips said. “It’s kind of unfortunate that really what helped promote Swim Guide this summer was the incident of the of the young boy getting Vibrio … [but] that really woke people up on what’s inside the water.”

The numbers of bacteria in the water have been rather high this summer based off of runoff that goes into the bays and ocean when it rains.

The waters must test below the 100-milliliter sample to be considered safe to swim in. For instance, unsafe to swim water has levels above 104 units per milliliter.

The most bacteria dense waters that Assateague Coastal Trust collects from tends to be creeks in Ocean Pines and Berlin.

The number of bacteria has also increased in the past year likely because of runoff, Phillips said.

For example, in 2019, Turville Creek, in Berlin, which tends to have the highest numbers of all the waters tested, saw a level of 736.2 bacteria units per milliliter on Aug. 21. In 2018, that number was 584.8 around the same date.

In waters where people tend to swim, such as the water near the Isle of Wight Nature Park and Horn Island, numbers have been fairly safe this year. This is excluding the beginning of August, when the water near Horn Park saw 500 per milliliter, which is uncommon for that area given how close it is to the ocean, which naturally flushes out bacteria every few hours with the tide.

This should not discourage people from swimming in the bays or ocean, Phillips said, as long as they prepare accordingly.

“Keep a first aid kit available so cuts can be treated immediately with an alcohol wipe or antibacterial ointment,” Phillips said. “Use waterproof bandages and wear water shoes with rubber soles to avoid cutting your feet.”

The process of collecting the samples is time and labor consuming, Phillips said, and is not funded by the county or state. Assateague Coastal Trust receives some donations and support from the local community but also appreciates any donations.

For more information about Assateague Coastal Trust, visit or Assateague Coastal Trust on Facebook. For more information about the Swim Guide, visit

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