Aquatic Macroinvertebrates on Bald Head Island

By Riley Westman, Fall Intern 2024

A giant water bug, one of many macroinvertebrates found in freshwater ponds around Bald Head Island.

Sideswimmer amphipod

Aquatic macroinvertebrates are organisms that can be seen with the naked eye (“macro”), don’t have a backbone (“invertebrate”), and live in water for all or part of their life cycle. Despite being ubiquitous in freshwater ecosystems, they rarely get the love they deserve. Macroinvertebrates provide a number of ecosystem services, including aiding in nutrient cycling and serving as a food source for more well-known organisms like amphibians and fish. They are also great indicators of water quality conditions, as certain species are less abundant in heavily-impacted bodies of water. As long-term (> 1 year) residents of aquatic systems, their communities also reflect long-term environmental conditions, so monitoring these communities annually can substitute for higher-frequency (and more expensive) water quality monitoring.

Fall interns Riley and Natalie pick through a macroinvertebrate sample collected from the pond beside Hole 14 of the island’s golf course.

At the Bald Head Island Conservancy, we are interested in establishing baseline conditions for the ecological health of the island’s ponds, as well as determining how environmental conditions influence which species thrive. Prior to this fall, the Conservancy had never surveyed macroinvertebrates in any of Bald Head Island’s freshwater ponds. This October, fall interns Riley Westman and Natalie Novak, with the mentorship of Coastal Scientist Allison Polinski, decided to address this need for their intern projects. They collected macroinvertebrates, soil samples, and water quality data from six ponds on the island. The ponds surveyed include popular wildlife-viewing destinations (Wildlife Overlook and Ibis Pond) and several ponds on the Bald Head Island Club’s golf course (where we pulled up several stray golf balls in our samples!). 

Forktail damselfly

There are a number of interesting organisms that call Bald Head Island’s ponds home. For example, you have certainly seen dragonflies frequenting the island, but did you know that their larvae actually live in water for months to years before growing wings and flying away? Dragonfly larvae (along with their close relatives damselflies – pictured here) are predators that eat smaller macroinvertebrates, as are giant water bugs (also pictured here). Other organisms you are likely familiar with seeing on land are snails and caterpillars, but both of these also have aquatic counterparts. The snails and caterpillars in our ponds live on underwater plants, but while snails scrape algae off the plant surfaces, aquatic caterpillars chew through the plants themselves. Other organisms, like amphipods, shred and eat dead leaves and other organic matter. That is just a snapshot of the organisms we collected; in total, we identified 21 unique species across just these six ponds. Next time you check out one of the island’s ponds, remember to show some appreciation for our aquatic macroinvertebrates!