Author Interview: Feeding preferences and the effect of temperature on feeding rates of the graceful kelp crab, Pugettia gracilis

by Communities @ PeerJ | Apr 24, 2023 | Article Spotlight, Author Interview, Hubs, Hubs News

PeerJ talks to Katrina H Johnson from The University of California San Diego about “Feeding preferences and the effect of temperature on feeding rates of the graceful kelp crab, Pugettia gracilis“ published in PeerJ Life & Environment as part of the IABO Hub. The IABO Hub is the publishing home of the International Association for Biological Oceanography, and features the latest biological oceanography research published by the members of IABO.

Katrina Johnson

Can you tell us a bit about yourself?
I am a PhD Candidate at Scripps Institution of Oceanography at the University of California San Diego in La Jolla, California. I have conducted research in many sectors of the marine science world, from carbon sequestration in eelgrass beds to feeding preferences of kelp crabs to physiological trends in leopard seal populations. Most recently, my research has focused on anthropogenic impacts on cetaceans. For my PhD, I am quantifying anthropogenic noise, particularly from commercial shipping, in underwater soundscapes and investigating its impacts on marine mammals as they rely on sound for communication, navigation, foraging, among other behaviors. I hope to have this research inform management strategies and conservation of marine mammals in the future.

Can you briefly explain the research you published in PeerJ?
Our paper arose from my undergraduate research at Bates College in Lewiston, Maine. I received a fellowship that funded summer research at Friday Harbor Laboratories on San Juan Island, Washington with Dr. Katie Dobkowski where I researched the feeding preferences and rates of the graceful kelp crab (Pugettia gracilis). As shallow subtidal and intertidal ecosystems are of particular interest with changing ocean conditions, graceful kelp crabs were an interesting organism, being a relatively understudied, abundant consumer in the shallow subtidal ecosystems of the Salish Sea. We first examined the feeding preferences between native kelp (Nereocystis luetkeana) and invasive seaweed (Sargassum muticum). We then expanded upon this by studying feeding rates of their preferred seaweed at elevated temperatures in an attempt to understand their role in changing coastal food webs.

We showed that graceful kelp crabs preferred the native kelp over the invasive seaweed if given a choice, but ate equal amounts of native vs. invasive if not given a choice. We also documented that crabs exposed to elevated temperatures ate more than those in ambient temperatures. These results demonstrate the diet flexibility of the graceful kelp crab and suggest that warming ocean temperatures may prompt an increase in their feeding rates.

What was significant about your findings?

Coastal food webs are experiencing short and long-term ocean warming. Atmospheric heatwaves have had large impacts on nearshore ecosystems and have created large-scale shifts in the structure of kelp forests. As key kelp consumers, kelp crabs are of particular interest in understanding the pressures placed on kelp forests. We showed that graceful kelp crabs prefer the native kelp over invasive seaweed. Further, we showed that increased temperatures lead to increased feeding rates. The combined results may exacerbate harmful impacts on native kelp, which is already vulnerable to warming and invasive competitors. If graceful kelp crabs consume more native kelp at higher temperatures, and invasive seaweed populations proliferate in warmer waters (as shown in other studies), future native kelp survival may be threatened. Our study is a step towards understanding the widespread threats to native kelp populations.

How did you first hear about PeerJ, and what persuaded you to submit to us?

One of my co-authors, Katie Dobkowski, has published with PeerJ before with a positive experience. My co-authors and I wanted to share our findings in an open-access journal of this caliber. The review process was helpful and fair and we appreciated the expertise of the editor and reviewers we worked with.

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