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Fall 2017
Environmental Report

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South Carolina Notable State

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Giant salvinia (Salvinia molesta) as seen on Lake Marion.

World’s Worst Aquatic Invasive Plants

For Casey Moorer and Ernie Guerry, what began as another routine boat survey in Lake Marion quickly turned ominous at Elliott’s Landing, where Guerry discovered a different plant lurking between the mix of duck weed and crested floating heart.

Guerry pointed out the plant to Moorer. “My response was, ‘I hope that’s not what I think it is,’” said Moorer.

Both Moorer and Guerry work for Santee Cooper, which is responsible for managing lakes Marion and Moultrie. Upon first glance Moorer, the supervisor of biological services, and Guerry, environmental technician for environmental resources, identified the species as either common salvinia, Salvinia minima, or giant salvinia, Salvinia molesta.

A microscopic view of the leaves of giant salvinia.

“Last year we found common salvinia, or Salvinia minima, which is much less aggressive than giant salvinia, on upper Lake Marion. I was hoping that what we found at Elliott’s Landing was common salvinia,” explained Moorer. 

Guerry and Moorer took some samples to the lab. The microscope confirmed their fears, showing the plant had touching hair-like structures that form a resemblance to egg beaters.

The plant, which is native to Brazil, entered the United States in the 1990s through the horticultural trade. Since its introduction, salvinia has been discovered throughout the Southeast from Texas to North Carolina.

Giant salvinia is a serious threat to freshwater systems and is a significant concern for lakes Marion and Moultrie, and those who enjoy them.

“Salvinia molesta is a very aggressive plant that has been labeled by some in the industry as the ‘World’s Worst Aquatic Invasive Plant,’” said Santee Cooper Environmental Resources Manager Larry McCord.

Santee Cooper employees search Lake Marion in search of Giant Salvinia.

This particular species is infamous for its rapid growth across water surfaces and its formation of dense floating mats up to 3-feet thick. The aggressive growth prevents light from reaching other plants, depleting oxygen levels and degrading water quality for fish and other aquatic organisms. 

Employees with Santee Cooper’s environmental services estimate giant salvinia has spread across 3,900 acres in upper Lake Marion.

“That does not mean that the lake is covered with 3,900 acres of Salvinia molesta. This plant is free-floating, so it moves wherever wind, water, boat traffic or wildlife takes it. Right now, the giant salvinia is scattered and getting caught up in the crested floating heart in the area,” said Moorer.

Unfortunately, there are no known biological control agents available to help control the plant. Grass carp, which are used for controlling hydrilla, another non-native, nuisance aquatic plant, do not eat salvinia. Moreover, an insect that feeds on salvinia in South America, salvinia’s native continent, would not survive South Carolina’s winter temperatures.

Scott Lamprecht, fisheries freshwater coordinator for the South Carolina Department of Natural Resources, said, “From my perspective, Salvinia molesta is capable of taking over huge parts of the lake and preventing recreational use. This species can be eradicated, but it’s going to take a lot of hard work due to its ability to hide in small quantities in different areas.”

The distinctive purple flowers of water hyacinth (Eichhornia crassipes), another common sight on Lake Marion (left). Salvinia molesta can be identified by its light to medium green, nearly round leaves on branched stems (right).

Controlling Invasive Plants

Twelve years ago, employees with Santee Cooper’s analytical and biological services department made an aquatic nuisance species discovery when they found crested floating heart. At the time, crested floating heart was determined to be the most aggressive, floating-leaf plant encountered on the lakes. Originally from Asia, the plant is extremely invasive and can quickly overtake a waterway. The upstream colonization of the crested floating heart is attributed to its tendency to latch on to boat hulls, allowing it to be transported to new areas of the Santee Cooper Lakes. Due to crested floating heart’s ability to withstand treatment with commonly used herbicides, controlling the plant has been very difficult.

However, after over a decade of large-scale treatments, Santee Cooper successfully reduced the crested floating heart population. Nearly continuous treatments are still applied along residential shorelines, near commercial facilities and in important wildlife habitat areas.

In addition, the battle against hydrilla in the lakes continues since its 1982 discovery in Lake Marion. In 1989, Santee Cooper began stocking grass carp in the affected areas of the lake to feed on the hydrilla. After five years, the system-wide reduction of hydrilla was evident. Maintaining control of this aggressive, submersed aquatic plant continues to be a challenge, and grass carp populations are adjusted yearly to keep the plant from rapidly spreading. 

Santee Cooper Environmental Resources Manager Larry McCord examines a patch of Salvinia molesta entwined with crested floating heart during a patrol of Lake Marion.

Water hyacinth, first discovered in Lake Marion in 1994, also continues to be a periodic problem in the lake system. Temperatures below freezing will kill the plant, if freezing occurs at the water surface. South Carolina had a mild 2016 winter, resulting in the treatment of nearly 1,000 acres of water hyacinth to date this year.

Though all invasive aquatic plant species are experts at spreading effectively on their own, boaters can help prevent their spread by being aware of the different species and checking boats and trailers regularly.

While boaters are doing their part, Santee Cooper is committed to doing its part, making sure the Santee Cooper lakes are as healthy as they can be.