Author: Laura Oleniacz
While wading in about a foot of water in the Dan River, Victor Holland saw an insect he didn’t recognize. He was searching for aquatic life under boulders in the river when he saw the larval insect clinging to some riverweed.
It was 2014, and as a benthic biologist with the Biological Assessment Branch in DEQ’s Division of Water Resources, Holland’s mission was to classify the insects and other aquatic life in the Dan River. But even under a magnifying glass, he still didn’t recognize this mayfly, which was about a half-inch in size.
“I was standing in the river, and I had it on my hand,” Holland said. “Even under a lens, I didn’t know what it was.”
Holland brought samples of the mayfly, as well as its nymphs, back to the branch’s laboratory in Raleigh. He and the other benthic biologists on his team looked at it under the microscope, and compared the insect to samples of other critters in the laboratory, as well as to records kept by a museum in Colorado. They also began studying the characteristics of the mayflies over time in different life stages in the lab.
After all that, the conclusion was made. Holland, and the other benthic biologists in the DWR Biological Assessment Branch, had discovered a new species of mayfly.
Their findings were published in the scientific journal Zootaxa in 2016. Since then, the team has discovered other new species. In total, they’ve published four, including one this year, with more on the way.
“Finding a new species is a great joy in this type of work,” said Chris Verdone, a benthic biologist for DWR. “They tend to be very rare, and they’re not easy to find.”
Where Water Flows, the N.C. Benthic Team Goes
As part of an effort to classify the water quality of flowing water across North Carolina, Holland and the other DWR Biological Assessment Branch benthic biologists travel across the state to collect samples of small aquatic animals that live on the bottom of streams, rivers and swamps.
They look for dragonflies, stoneflies, snails and even worms – creatures known in the scientific world as “benthic macroinvertebrates” since the term “benthic” means “bottom-dwelling.”
On a five-year basis, the benthic team samples a subset of streams in every basin across North Carolina. There are 17 river basins in the state.
“If it’s flowing, we’re there,” said DWR benthic biologist Steven Beaty.
The team uses a net to capture invertebrates, places them in jars for transport back to Raleigh and looks at them under the microscope. In 2010, they started a project to raise insects in the laboratory so they could be sure they were classifying insects and other critters across different life stages with precision.
Many of the aquatic insects live in the water as nymphs or larvae. Identifying these animals can be difficult, since their physical characteristics, or morphology, can be very different depending on their life stage.
What the Presence (or Lack) of Bottom Dwellers says About Pollution
The biologists sample for these critters because their presence – or lack of it – is an indicator of the health and cleanliness of the water they live in.
“If you think about water quality, you might think about emerging chemicals or sewage,” Beaty said. “These bugs live in the water, and they are subjected to these pollutants. If they wipe out the life in the water, that ain’t good.”
So, classifying the specific type of species in a particular water body is important.
“These organisms have different susceptibility to pollution,” Beaty said. “Stoneflies and mayflies and caddisflies are pretty sensitive to pollution, meaning it will kill them off. Midge larvae, or dragonfly larvae, can withstand a little bit more.”
Depending on the community of organisms they find, they assign the water body a classification of “poor,” “fair,” “good-fair,” “good” or “excellent.”
“Each individual taxon has a tolerance value calculated for it,” Holland said. “If the tolerance value is high, it can indicate that a species is fairly tolerant of pollutants. If it’s really low, it’s intolerant. That score is fed into a computer algorithm to create an index that’s used to assign classifications for streams.”
Since tolerance values can vary depending on the species, that means that identifying the species is of particular importance. Researchers look at the body color, presence or absence of certain structures, as well as tiny hairs, to compare species.
For the publication this year of a new species of stonefly called Isoperla riverae, Verdone looked at more than a thousand specimens. When stoneflies, mayflies and caddisflies mature, they emerge from the water and look for a mate. The female will lay eggs in the water. The eggs have specialized structures that allow them to sink and adhere to surfaces under the water.
“There appear to be a lot of undescribed species of stoneflies,” Verdone said. “Of the aquatic insects we study, they tend to be some of the most sensitive to pollution.”
Accuracy in identification ensures higher quality, and more rigorous water quality assessments.
The team also hopes that publishing these new species could also help to protect biodiversity in North Carolina’s waterways.
To find the team’s classifications for streams across the state, click here.