The search for sea slugs
Linking non-divers to the excitement of ocean discovery
by Elise Pletcher
Citizen Science and Volunteer Coordinator
The Marine Science and Technology Center
Highline College
The Dendronotus iris, a species of nudibranch recently found in one of the MaST Aquarium tanks.
he Nudibranch Team is a citizen science volunteer program at the Marine Science and Technology Center of Highline College. Volunteers work with Aquarium Staff to record populations of nudibranchs (colorful sea slugs). The MaST Center’s 3,000-gallon aquarium is operated on a “flow-through” model where 250 gallons of unfiltered Puget Sound water is pumped every minute through the tanks. This water brings with it several kinds of plankton, which are hard to identify and collect in the open waters of the Puget Sound, but within our tanks can be identified at the species level. Even once they are past their planktonic larval stage, many of the nudibranchs found in our aquarium are less than 1 cm in length!
This system offers the unique opportunity to record abundance of several nudibranch species throughout the year. Citizen scientists on our nudibranch team are trained to identify upwards of twenty nudibranch species, and use flashlights to track them down in our tanks. Why nudibranchs you may ask? They make an excellent species to study because each species is very distinct morphologically. Nudibranchs are the subject of a lot of macrophotography here in the Puget Sound; their bright colors and patterns make them a photogenic group of animals. Many of the animals in our aquarium are collected, but the nudibranchs come in naturally. When we see a nudibranch, it is exciting, because we get to discover them in the tanks! The thrill of not knowing what you are going to see is also a key part of what makes diving so exciting. The Nudibranch Team provides this thrill to non-divers.
The MaST’s Nudibranch Team hosts a diverse crowd with a wide range of abilities. Some are divers who already have a passion for filming nudibranchs, while others are just learning about these sea slugs for the first time. Our team is made up of mother-child duos, music teachers, retirees, and recent college graduates, all with one thing in common: their obsession with these peculiar sea slugs. You don’t need a SCUBA certification to get involved, just an interest in peering into a tank with a flashlight for an hour or two a week. Volunteers start with a 1.5 hour training in which they learn all about nudibranchs and how to identify them, including morphological traits. After the training, they’re given an identification guide, a data collection sheet, and set loose. Of all the MaST’s volunteer programs the Nudibranch Team demands the least amount of training time, it’s what helps make it so efficient.
The program originally started in 2013 when former Education Coordinator Eugene Disney and Manager Rus Higley started noticing certain nudibranchs were in the tanks in greater numbers depending on the time of year. They decided to round up a couple of volunteers to help count nudibranchs. Fast forward five years, and we are starting to see some interesting trends in nudibranch abundance emerge. Certain species are peaking in abundance at certain times of the year.
Of our most common species, each has a distinguished peak in annual abundance. Some tend to have high abundance throughout the year, but dip in the summer. While others peak in the summer months. This is interesting because nudibranchs are indicators of ocean health. If we see a huge spike in populations, something in ecosystem is likely influencing this spike. Since they occur naturally in our aquarium, we can use their abundance as a proxy for nudibranch abundance in the water at Redondo Beach. With the MaST’s four complete years’ of nudibranch population data, we have a strong baseline for tracking population changes. Nudibranch population changes can provide insight into the population health of their food sources: hydroids, sponges, and bryozoans.
We have shared this unique citizen science program at the Western Society of Naturalists Conference in 2017, Salish Sea Ecosystem Conference 2018, and the Northwest Aquatic and Marine Educators Conference this summer! Are you attending the Northwest Aquatic and Marine Educators Conference this summer? Check out our poster Tracking Temporal and Seasonal Changes in Nudibranch Populations from a Small Aquarium presented by the wonderful Vanessa Hunt, an Associate Professor at Central Washington University.
In the next few months, we hope to design a better classification system based on volunteer experience and expertise. This includes updating our identification keys to address species color variation. The ultimate goal for this program is to publish the data, and make it available for public use by others who wish to study invertebrate population trends in the South Puget Sound.
While the MaST is excited to have some quantitative data behind our sea slug populations, the best part of the team is still sharing in the excitement of discovering a new nudibranch –just recently, we found a Dendronotus iris, a beautifully branched nudibranch, mostly white and flecked with orange and purplish-brown. Staff and volunteers flocked to the aquarium to get a closer look at this nudibranch. It has been over a year and a half since the last time this species was spotted in one of our tanks!
The Marine Science and Technology Center is the marine laboratory of Highline College. Committed to increasing ocean literacy through community interaction, personal relations and exploration; the MaST strives to accomplish this through volunteer programs, formal college classes, and k-12 school programs.
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Author: Elise Pletcher is the Citizen Science and Volunteer Coordinator at the MaST Center in Des Moines WA, where she works alongside volunteers on the Jelly, Nudibranch, Marine Mammal, and Discovery Day volunteer teams.