water quality blog

What's in the Water: A Breakdown of How We Sample

Miami Waterkeeper takes weekly water quality samples from several sites around Miami-Dade County. Read more HERE on why we sample. There are many steps to ensure samples are taken, processed, and reported efficiently. To elaborate on this process further, we have compiled a list of questions and detailed answers.


How do we sample our waterways?

Miami Waterkeeper samples key recreational areas in Miami Dade County once a week. Water samples are collected at these sites and are measured for the presence of Fecal Indicator Bacteria (FIB). FIBs are used to indicate whether bacteria that cause human illness are likely to be present in the water. The EPA sets a standard for the safe level of FIBs in recreational waters. High concentrations of FIBs can indicate poor water quality and risk to human health.


When is a swim advisory issued?

EPA standards tell us when the water quality is considered “poor.” Thatis, the water quality could cause people recreating to experience skin itching, ear or eye irritation, gastrointestinal distress, or other illnesses. The Florida Department of Health (DOH) is the agency that oversees swim advisories. The DOH issues an advisory when two consecutive water samples exceed EPA standards for water quality. 

Remember: the FIB, enterococci, is an indicator. It just tells us that there may be harmful viruses or bacteria present in the water that can make people sick. We aren’t able to determine the source of these harmful viruses or bacteria from our testing - only genetic analysis can do that. Also, Miami Waterkeeper shares water quality data, but we cannot issue formal “swim advisories.”

Be sure to check Swim Guide, our website, our social media, the Florida DOH Healthy Beaches program website, or your local news outlet to determine if an advisory is in place.


How are the samples analyzed?

Through generous grant funding and sponsorship, Miami Waterkeeper monitors recreational sites weekly for enterococci -- the FIB measured in saltwater. By following EPA protocols, Miami Waterkeeper evaluates FIB levels in water samples using the IDEXX system.

Our sampling is made possible by sponsorship from Zoo Miami, Paul and Maxine Frohring Family Foundation, and the City of Miami. 

Here are the steps:

  1. Collect - Samples are collected from the shoreline using a sterile bottle or bag at a depth of 6-12 inches below the surface.
  2. Store - Samples are stored in a darkened container on ice and are taken to our lab for analysis.
  3. Mix - In the lab, the sample is mixed with IDEXX Enteroalert - a nutrient indicator that actually lights up when consumed by the FIB.
  4. Incubate - The sample and indicator are incubated, or warmed, in a special tray for 24 hours.
  5. View - Then, our scientists use a black light to view the tray. The more the tray fluoresces, or lights up, the more enterococci are in the water sample!
  6. Calculate - We then calculate the exact amount of enterococci in the water using a special formula.
  7. Resample - If a sample is greater than the EPA standard, we head back out to the field to resample everyday until the water quality improves at that site.

Interested in having all the info in a printable fact-sheet? Click HERE to download and use for your reference.

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