Meet Dr. Sophie George, corresponding author of The Physiological and Biochemical Response of Ribbed Mussels to Rising Temperatures: Benefits of Salt Marsh Cordgrass

A Smith, J Erber, A Watson, C Johnson, W E Gato, S B George

Dr. George recently answered a few follow up questions about this study she co authored that centered on salt marsh ecosystems that are heavily reliant on ribbed mussel (Geukensia demissa) populations to aid in rapid recovery from droughts. 

The focus of this study was thus to document the effects of rising temperatures on ribbed mussel populations in a Georgia salt marsh. Seven lab and eight field experiments were used to assess the effects of current air temperatures on mussels at two high marsh (HM) sites with short and sparse cordgrass and one mid marsh (MM) site with tall and dense cordgrass. 

Can you share with us a bit about your background, and what led you to this research project? 

My first exposure to marine invertebrates was during graduate work at the University of Paris, Pierre et Marie Curie now Sorbonne University.  I studied the effect of nutrition on the reproductive strategies of echinoderms and the consequences on larval development at one of the university’s marine stations, at Villefranche Sur Mer in the south of France.  In recent years, my interests shifted to investigating how environmental change is affecting both adults and larvae of a variety of species.  In the Pacific Northwest, sea stars and sand dollars, and in the Southeast US, sand dollars, fiddler crabs, and mussels. A third of the salt marshes (~ 400,000 acres) found along the Southeast coast are along the coast of Georgia about an hour away from Georgia Southern university where the study on the mussel Geukensia demissa was done. The salt marsh ecosystem is heavily reliant on this species for survival. For example, models indicate that salt marsh recovery after droughts is accelerated in the presence of these mussels from over 100 years to as little as 10 years. In addition, as water rushes into the salt marsh, mussels reduce pollution by filtering tons of suspended matter/per hectare/year.  However, heat waves are increasing in frequency and causing the deaths of millions of mussels worldwide. I began to wonder whether G. demissa was next. I thus started a project to document the temperatures at several salt marsh sites at Tybee Island, GA and assess how this mussel was responding to current environmental conditions.  The salt marsh is a perfect environment to introduce undergraduate and graduate students to research as there are so many questions and species to work on and it’s not too far from the main campus. I love including students in all my research projects and have mentored over 90, at least a third worked on salt marsh projects.  

In what way do you feel these findings on the physiological and biochemical response of Ribbed mussels to rising temperatures  demonstrate urgency for those who care about the conservation/ preservation of the Georgia salt marshes?

This study shows that temperatures are already very high in the summer in some of Georgia’s salt marshes, (> 40°C to > 50°C in some instances). This study also shows that mussel heart rates increased dramatically (>20 bpm higher) for those subjected to much lower temperatures in the laboratory (36°C) than the maximum temperatures we recorded in the field.  Currently, mussels at two sites in the mid and high marsh do not experience temperatures above 32°C for much of the year.  In agreement with past studies, the presence of tall and dense cordgrass at these sites may be providing enough shade to sustain large mussel aggregates.  However, recent satellite data indicates that cordgrass biomass in Southeastern salt marshes is decreasing (O’Donnell and Schalles). A decrease in cordgrass at any of our sites could have detrimental effects on mussel populations. At sites with very little cordgrass, mussel densities and heart rates were very low. Personally, I could not believe how hot it got.  I remember my students and I drinking tons of ice-cold water just to stay hydrated while working.  Unfortunately, it did not always help and over the years several of us had to stop all work just to recover from the tremendous heat. Something mussels cannot do!

Given these results, there is an urgent need to conserve all of Georgia’s salt marshes from further coastal development.

Based on your findings, what do you feel are some steps that those who live in and around the Georgia salt marsh can take to better the situation? 

Cut back on developing areas around all of Georgia’s salt marshes

What is your next project? 

 Our current project is on the effect of the duration of marine heat waves on larval growth and development of sea star larvae in the Pacific Northwest.