Eastern North Carolina has seen a surge in intense tropical storms and researchers say the impacts go beyond flooding and property damage.
Have you ever thought that hurricane season seems to be getting worse each year?
UNC-Chapel Hill Kenan professor of marine and environmental sciences, Dr. Hans Paerl, said not only can decades of data demonstrate the increasing frequency of tropical storms and hurricanes but also years of living in eastern North Carolina can reveal just how severe the impacts have become.
“You know, I’ve lived in coastal North Carolina for over 40-years and the first 25, 30 years or so, things hadn’t really changed all that much, but since the mid-1990s we’ve seen upsurges in more tropical storms, including very extreme events.”
In the wake of 2018’s Hurricane Florence, Paerl and his team of researchers looked at data from the last 100 years and published a paper to show that indeed tropical cyclones have increased in terms of frequency, intensity and the amount of rainfall. Paerl said runoff from these dramatic rain events is where his research comes in.
matter (CDOM) from land into coastal waters.
“You know, they say when it rains, it pours. Well, we're seeing even something beyond that these days when those events occur, they are putting a lot of nutrients and contaminants into our waterways that arrive at our sounds and estuaries and even in the coastal zone. So that's driving an increase in algal production.”
Paerl said this algae is healthy, in stable, natural amounts.
“We like to have nutrients support the algae because the algae support the food chain. But we're into a period now where we're having too much of a good thing, so to speak.”
This influx in algal production initially pools on the surface of water, and Paerl said sometimes it has a pretty punchy odor as well.
“Where the algae growth is so severe at times that the food chain can't really consume all that algae. And so as a result we get blooms. They often look like perceptible changes in color of the water.”
The excessive algae eventually dies. Paerl said this is where another environmental problem begins.
“When they die, they sink to the bottom. And as a result, all that organic matter is trapped in our bottom waters and that leads to oxygen consumption. So, you know, too much algae and that consumes oxygen. And we've seen increases in the low oxygen events that have gotten more severe overall.”
Paerl said these decreased oxygen levels can stress the marine wildlife.
“The shellfish can't move, you know, they're more or less stuck in these places. And if they run out of oxygen in that habitat, they're pretty much done with.”
In Paerl’s research, he said there is a visible 30-year trend showing increases of algal blooms in both freshwater and marine systems. In freshwater, the blooms are composed of cyanobacteria or blue green algae. In the saltwater, the blooms are often dominated by dinoflagellates, including species that are related to the red tides.
“The unfortunate thing about the blooms, besides the fact that they can cause low oxygen conditions, is that the organisms produce toxins that are toxic to fish, shellfish, domestic pests to drink the water and humans. It's not like they intend to kill us, but they do have a detrimental effect when you get buildups of algae as blooms.”
Paerl said whether people are noticing the algal blooms, loss of shoreline, more hurricanes, erosion or just hotter summers, the threat of climate change is becoming more and more visible.
“Residential areas or even businesses that are that close to the shoreline, it's going to be a problem, particularly when you combine sea level rise with the more severe impact of storms eating away at our coastline.”
As our environment continues to change, Paerl said mitigation tactics like creating, restoring and protecting North Carolina’s wetlands can help the state fend against damaging climate events. The wetland systems take many forms, filtering and slowing the flow of water after heavy rainfall events like hurricanes.
“There are going to be some situations where, you know, we have catastrophic events like what we're seeing now in our mountains. But I think there are a lot of events that sort of fall below those catastrophic events that can be mitigated and reduced in terms of how that ultimately impacts our coastal environment and our ecosystems.”