Behind the Scenes: Oyster Lullaby

Oysters were once a booming fishery in North Carolina with many natural oyster beds around Pamlico Sound. Unfortunately, these natural reefs have been exposed to overfishing, poor water quality, and disease and North Carolina’s oyster populations have declined drastically causing the collapse of the oyster fishery.

oysterA group effort by scientists from multiple universities, government organizations, and local residents has been made to restore North Carolina oyster reefs. I had the opportunity to get a behind the scenes look at some of the oyster research going on at NC State University’s Center for Marine Sciences and Technology (CMAST) in Beaufort, NC.

Ashlee Lillis, a postdoctoral scholar at CMAST, is studying how oyster larvae choose their new homes (i.e. settle). She proposed that these larvae ‘listen’ for certain sounds that existing oyster reefs make. I don’t know how many of you have taken the time to listen underwater, but it’s not as quiet as you might think; in fact, it can be really loud. Waves, currents, and critters make oyster reefs a noisy place, and these sounds are different than other noises around the Sound (see what I did there? :P). Ashlee tested her hypothesis several different ways:

First, Ashlee used hydrophones to record several hours of reef and off-reef underwater noises.

Oyster reef sound profile

Oyster reef sound profile

Off-reef sound profile

Off-reef sound profile

This was a bit of a challenge, and I helped with making and deploying this equipment to the field site. Sometimes a lot of scientific testing equipment requires quite a bit of ‘MacGyver-ing’, and the team rigged up a system of buoys and anchors to keep the hydrophones and speakers where they needed to be.IMGP0115Once we had everything prepped we loaded up the boat and set off for one of several field locations around Pamlico Sound. Ashlee and the guys geared up in scuba equipment and jumped in to get started. I handed equipment over the side as they needed it and took care of the boat (we were required to have one person on the boat at all times just in case; and it’s a good thing we did… but that’s a story for another behind the scenes).

Second, those recordings and settlement were tested in the lab. The oyster reef sound, off-reef sound, and no sound were played to different groups of oyster larvae to see which sounds contributed to higher settlement. Ashlee found that the groups that had constant oyster reef noise did indeed have increased larval settlement.

Figure from Lillis et al. 2013, PLOS ONE

Figure from Lillis et al. 2013, PLOS ONE (link to article below)

Third, Ashlee took it to the field. Larval housings (sealed containers with groups of oyster larvae) were suspended over existing reef or non-reef habitats to determine which would have higher settlement. Again, oyster settlement was much higher over the existing reef environment.

So what does this mean for the oyster fishery? Learning more about how oyster larvae choose where to settle means that we may be able to re-create these conditions to encourage more settlement and enhance oyster populations in Pamlico Sound. Increasing oyster populations and the health of North Carolina’s oysters could revitalize the oyster fishery and, in doing so, boost local economies.

More details about Ashlee’s research can be found here and in the PLOS One publication Oyster Larvae Settle in Response to Habitat-Associated Underwater Sounds.IMGP0112IMGP0116IMGP0117

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