Clavelina oblonga, a marine foul invasive species, not only reduces the diversity of the communities it invades, but also interferes in their recovery from natural disasters – a process known as ‘succession’.
Succession refers to how an ecosystem recovers after a disturbance or natural disaster – does the system come back more or less the same as it was in terms of species composition, or is it different?
“The classic example of succession is a forest undergoing a wildfire,” says Kayla Christianson, a former North Carolina state graduate student and first author of a paper describing the research. “As the community recovers from the fire, it proceeds with a predictable pattern of community development – starting with grasses and ending with trees and mature forest. This predictable order of succession is mainly due to the seed bank below the ground, which allows the community to recover regardless of when the disturbance occurs. “
However, marine fouling communities do not follow the same pattern as terrestrial ecosystems. Polluting marine species are invertebrate filter-feeding organisms – such as barnacles or mussels – that settle on hard substrates, such as docks, pilings or ship hulls. Soft-bodied tunicates such as the invasive C. oblonga are also fouled species.
“Marine fouling environments are different because different species of larvae are present at different times of the year. Carolina State University and corresponding research author. “For marine species, disturbance enhances the diversity of the community.”
Given the recent introduction and proliferation of C. oblonga along the coast of North Carolina, Eggleston and Christianson wanted to see how this invasive species would affect succession in a fouled environment.
Christianson and Eggleston duplicated succession experiments performed 50 years ago in Beaufort, North Carolina. They submerged terracotta settlements every four weeks from May 2017 to September 2018 along the docks and observed the communities that settled there.
During the study, 22 different fouling species settled on the plates. But in each case, when C. oblonga took hold, they quickly crowded out the other species. The study period also included an unusually cold winter, as well as the arrival ashore of Hurricane Florence in September 2018, allowing researchers to examine the succession after natural disturbance. While the cold and hurricane succeeded in eliminating C. oblonga, it quickly grew back and crowded out other species, eliminating species diversity.
“By testing the theory of succession again, we found that it holds in the absence of invasive species but not in their presence,” Eggleston said. “For these foul species, no matter when a disturbance occurs, the community always reverts to the invasive species.
“C. oblonga has only been here since 2015, but it doesn’t seem to have any real natural predators, it crowds out native species and it has a foot. We will need to watch this species and make sure it doesn’t affect our local shellfish industry. “
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Material provided by North Carolina State University. Original written by Tracey Peake. Note: Content can be changed for style and length.