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Cold Temperature Effects on Byssal Thread
Production by the Native Mussel Geukensia demissa
versus the Non-Native Mussel Mytella charruana

By: Sasha Brodsky | Mentors: Dr. Linda Walters, Dr. Kimberly Schneider, and Dr. Eric Hoffman

Methods

The following experiments were completed in a laboratory setting. The Mytella charruana trial began on 3 July 2009 and the Geukensia demissa trial began on 11 June 2009. Fifty adult-sized M. charruana (mean length: 23.5 ± 0.6 mm) were collected from the dock at Jacksonville Fire Station 38 Marine Unit (30° 23.232' N, 81° 38.305' W). Fifty adult-sized G. demissa (mean length: 51.4 ± 1.4 mm) were collected from a sea wall in New Smyrna Beach, Florida (28° 59'22.57" N, 80° 52'06.09" W). Following collection, mussels were cleaned and placed in aerated tanks at room temperature (23°C) with a filter and seawater from the collection location. The mussels were kept in the tanks for thirteen days to acclimate to laboratory conditions and were monitored daily to remove any dead individuals. Trials for both species were run with identical methodologies.

Plastic aerated aquarium tanks were placed in a laboratory setting at 23°C at the University of Central Florida. These tanks (29 x 20 x 20 cm) were prepared with 50% collection site water and 50% deionized water mixed with Instant Ocean® salts. Salinity was adjusted to match the conditions of the collection site (Jacksonville–10 ppt, New Smyrna Beach–30 ppt). Three replicate tanks were then prepared for each temperature treatment. Four mussels were placed in each tank on a plastic surface, and then individually labeled with bee tags (The Bee Works, Orillia, Ontario).

There were three temperature treatments: 10°, 13°, and 23° C. Water temperature was manipulated with chillers and water pumps. Experimental temperatures were reached by adjusting temperature 2° C/day for one week following acclimation. After the last temperature adjustment, all byssal threads were cut with a disposable scalpel. The number of new byssal threads was counted and cut each day for seven days, which was the total duration of the experiment. Mussel care included daily monitoring of mortality and 100% water change after three days. An algal paste solution, which contained Phaeodacylum tricornutum, Chaetocerus-B, and Nannochloropsis oculata, was fed to the mussels daily (1mL/mussel).

At the end of the experimental trials, we tested for significant differences in the mean number of byssal threads among treatments and over time using a repeated measures Analysis of Variance (ANOVA) using SPSS (version 17.0.2, 2009). No transformations were used because all data met the assumptions of ANOVA. A Tukey's post-hoc comparison was then used to delineate differences among treatments. A one-way ANOVA using SPSS (version 17.0.2, 2009) was also run at the end of the M. charruana trial to look for significant differences in mean number of byssal threads over time at the 23° C treatment. A Tukey's post-hoc comparison test was then used to determine differences among days.

         

Results >>