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Here’s why dark water is flowing and dead fish are being left behind in neighborhoods

As waters recede in the Longs area, fish begin to die off. The waters of the Waccamaw are becoming unsafe for them.
As waters recede in the Longs area, fish begin to die off. The waters of the Waccamaw are becoming unsafe for them. jlee@thesunnews.com

The vast amount of flooding as a result of Hurricane Florence isn’t only ruining homes and properties. Changes in water quality are creating an unhealthy environment for local aquatic critters.

As a result, water from the Waccamaw River has gotten darker and dead fish are being left behind.

Currently, dissolved oxygen and pH levels in the Waccamaw River are dropping below state water quality standards as a result of the vast flood area. These two factors are leading to the darker-than-normal waters and signs of a potential “fish kill.”

The depletion of oxygen to unhealthy levels leads to a fish kill, in which large amounts of fish die as a result of the poor environment. In some previously flooded neighborhoods, dead fish litter the roads, like in Longs on Monday.

While some plants have adapted to survive with little oxygen, many other river plants have not and may also suffer from the low levels of dissolved oxygen.

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As is being seen in the Waccamaw, organic debris, like twigs and plants, wash into the river and act like tea leaves, releasing particles that change the color of the water.

While these changes are harmful to fish life, this isn’t the first time the Waccamaw has experienced threatening drops in pH levels and dissolved oxygen.

“What I am observing is what I typically see after an intense flood event,” Coastal Carolina professor Susan Libes said.

Libes, who also is the director of the Waccamaw Watershed Academy, spent Tuesday morning testing the water quality of the Waccamaw River close to Murrells Landing, which is near Conway, for the first time since the flooding hit its catastrophic levels.

The flooding has made collecting data harder over the past week as many tools from the United States Geological Service were moved for protection.

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Typically a crew of volunteers, funded by local governments, regularly monitor water quality and upload it online. Using this data, people can begin to compare water quality from before and after the storm, as well as contrast it to that of previous disasters.

For now, Libes is collecting the data from one point along the river, which she said is not indicative of the quality of the whole river or other rivers. Still, it shows an isolated sample of what is in the water.

More data will be needed to comprehensively determine the impact on the entire Waccamaw River, but what Libes observed is what she would expect given what is occurring in Horry County.

In past floods, one of the biggest effects has been on dissolved oxygen, a good indicator of water quality. When organic matter, like leaves or tree limbs, gets into the water, microorganisms begin to decompose it, deleting oxygen levels in the water as they work.

While fecal matter can be detected in the water and could drop oxygen levels there, Libes said the vast quantity of water greatly dilutes its impact on the river’s health.

Even in past storms, when large amounts of fecal matter got out through septic systems, it was not enough to have a significant impact on fish life.

“I think it’s because there is so much water in the river,” Libes said.

That doesn’t mean fecal matter has lacked impact. It is just not comparable to the impact leaves and twigs have.

In addition to dissolved oxygen levels, low pH levels are contributing to unhealthy environments. The lower the pH levels, the higher the acidity of the water.

“The acidity level is very high,” Libes said. “That presents a problem.”

Even though the current water quality is unhealthy for aquatic life, it is not necessarily the worst Libes has seen. Nor does it mean that life will cease to exist in the river.

Fish may find ways to adapt to the temporary environment by mouth breathing at the surface or swimming farther downstream.

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