Guest Posts / How do we science?

Why Water Quality Matters

This guest post was written by Kellen Lauer.  Kellen just completed her Master’s degree in Marine Sciences at UNC-Chapel Hill.  She studies recreational water quality in the Noble lab at UNC’s Institute of Marine Sciences.  Kellen’s research focuses on tracking fecal contamination to its source.

As the weather takes a turn away from frigid winter and into spring, I know what’s on everyone’s mind: it’s soon going to be beach season! I’m sure you are all actively anticipating your beach visit(s) for this summer. Don’t have one planned? You should get on that soon. I’ve heard that Eastern North Carolina has some nice beaches you could go visit. So let’s skip ahead a few months. Now you’ve arrived at the beach, lathered up the SPF (right?) and are ready to take that first refreshing dunk into the ocean. One thing that’s probably not on your mind at this point is the quality of the water that you’re about to swim in. Does it really matter? After all, the ocean is a fish’s bathroom, so should we just accept that it’s full of poop and move on? While fish poop might not be of great concern to our health, there can be fecal contamination from other, more harmful sources that can make its way into the ocean.

Exposure to fecal contamination is a concern because of the pathogens that can be present and spread to a new host through contact. Gastrointestinal pathogens may enter your body through ingestion of water while swimming or playing in the surf. We’ve all been caught up in a crashing wave and ended up swallowing mouthfuls of salt water, right? Not only was the taste really unpleasant, but any bacteria, viruses and/or protozoa present in that water are now entering your digestive system. If any human pathogens are present, they could cause nausea, vomiting and diarrhea. But you don’t only have to swallow water to get sick. Skin irritation or rashes can be a common side effect of exposure and certain types of pathogens can cause ear, eye and respiratory infections. If you have an open wound, it can get infected by exposure to the bacteria present in the water. So think twice before using the mantra ‘salt water heals’ and maybe just use some anti-bacterial cream and a band-aid.

But fear not, things aren’t all that bad. I may have made things seem dire and convinced you never to go swimming again unless it’s in a pool filled with chlorine. However, most of the time water quality is ‘good.’ What constitutes ‘good’ water quality you may ask? The USEPA sets recreational water quality standards for specific types of bacteria which indicate the presence of fecal contamination. These bacteria themselves are not pathogenic, but they are ubiquitously found in all types of fecal material. Therefore, when these bacteria are present in a water sample, you know that there is some form of fecal contamination in the water. When bacteria concentrations are below the EPA thresholds, the level of risk of illness is low enough to not require any avoidance of exposure. Once the indicator bacteria concentrations surpass the thresholds, however, there will be a beach advisory which notifies the public of elevated bacteria levels and discourages people from going swimming that day.

kellen no swimming

No swimming today, based on yesterday’s sampling. Image from

Testing for individual pathogens would be prohibitively expensive and time-consuming. Although these indicator bacteria are in no ways perfect, they are a conservative measure to alert beachgoers to the presence of fecal contamination and protect public health by keeping people out of the water when the contamination is present. Different sources of contamination can pose different levels of threats to public health. Human fecal material obviously carries the highest concentrations of human pathogens, but animals can also be carriers of human pathogens. Seagulls, for instance, can carry Campylobacter and Salmonella species which can be pathogenic to people (and we all know where seagull poop ends up).

One of the biggest hurdles in the field of water quality monitoring these days is the methods used to quantify the bacteria present in a water sample. Current methods typically take 24-96 hours for results to become available. This is because the bacteria are cultured and must be given time to grow and reproduce so that they can be counted. As you may have already guessed, this puts a considerable window of time between when the sample is taken and the time the results can be posted. If bacteria concentrations are too high, no one will know until the next day and everyone who swam on the day the samples were taken would have already been exposed. If contamination is prolonged over multiple days then hopefully there will be no further exposure after that first day, but oftentimes 24 hours is enough time for the contamination to get out of the system (or be diluted enough to return to safe levels). More rapid methods have been developed in recent years that take 3-4 hours to get results, but the start-up costs and specialized training required to switch to the new methods have put them out of reach of many state testing agencies for use in routine monitoring. As with almost all forms of technology these new methods will one day be cheap and easy to use, but then who knows what the next big thing in water quality testing will be by then?

As I mentioned earlier, the general condition of beach waters is usually ‘good,’ meaning bacteria concentrations are at low enough levels that there is little risk of getting sick. The most common ­­­deliverer of fecal contamination is stormwater runoff. When it rains, overland flow scours deposited fecal material and carries it into the storm drains (did you pick up your dog’s poop this morning…?). If the water table rises to a high enough level, it could connect with septic tanks or damaged sewer lines to deliver human contamination downstream. The stormwater runoff then ends up wherever the pipe outfall lies. In coastal communities, this is often along the beaches. Water quality testing is typically done on a regular weekly or biweekly schedule, and is not weather dependent. That means that you won’t know every time the bacteria concentrations are too high.

kellen stormpipe

A Wrightsville Beach, NC, storm drain outfall. Photo by Kellen Lauer.

So here are some things to keep in mind when you take your beach vacation this summer:

  • Don’t swim right in front of a storm drain outfall. Even if it’s not actively discharging, the further you are from the pipe the better.
  • Especially stay out of any pooled waters around storm drain outfalls. You might often see children playing in these shallow, warm waters. This is just asking for trouble!
  • If there happens to be a heavy rain event give it some time before you go swimming again. Especially if there is a passing afternoon thunderstorm. People tend to go right back out to the beach after the storm passes, but all of the fecal contamination that was delivered during the storm is just sitting in the surf zone at that point.
  • Have fun! Even though this might not be the most pleasant thing to think about, there really is a low risk of getting sick from a day at the beach. Healthy adults have the lowest rates of illness, and you shouldn’t be worrying about catching any life-threatening illness out there.


For more information:

EPA Recreational Water Quality Criteria:

North Carolina Division of Marine Fisheries Water Quality Website:

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