Introduction: While investigating nongeniculate corallines, I decided to set-up a mini experiment. Melobesia became an instant interest of mine because of its epiphytic lifestyle. I wondered: how fast does it grow, how quickly can it recruit (especially in comparison to Smithora a fleshy red that is also an epiphyte on Phyllospadix), why is it only found on the tips of surf grass, does surf grass send out a chemical cue for Melobesia to follow, and will it grow on another substrate besides surf grass. I set-up a small experiment to answer some of these questions.
Results and Discussion: Because of the storms and large wave activity, I lost all of the real clean-picked surf grass bunches and some of the fake ones. However, there was still enough fake surf grass to make some conclusions. And they were filled with Melobesia colonies!! The garbage bag surf grass (picture) had fewer colonies of Melobesia than the chicken-feed bag surf grass (picture). Due to the dark color of the garbage bag, I felt I was unable to make accurate counts of colonies on these blades. Therefore, I mostly focused on the other fake surf grass.
There were 33 strands of this surf grass left and all were filled with Melobesia colonies. I counted well over 1000 colonies on one blade (picture of colony). For two blades, I measured out 2cm sections and counted the colonies per section to get this graph. Sections start at the tip and work towards the base with section 22 being 3cm instead of the usual.
This graph shows that there is still considerably high numbers of colonies almost right down to the base of each blade. Consistently, the highest densities of colonies do occur at the tips.
The presence of Melobesia also tells us that this species can grow on fake substrates that do have similar morphology and location as the real surf grass. However, this data cannot really say anything conclusive about chemical cues of surf grass if any. Melobesia, during this season, is a faster recruit than Smithora and can quickly colonize new substrata putting on about 1000 colonies of every blade of this material. Melobesia can also grow relatively quickly (picture: in comparison to width of blade). The most important results of this experiment are that Melobesia can land on other substrates than surf grass, it can have a pattern of distribution with high densities of colonies at the tip and close to the base, it can recruit well under a month, and can grow up to 1.5mm in less than a month. (Full grown Melobesia is about 2mm).
Future Research: Much future work could be done with this topic. Research could be done to understand if Melobesia reacts to some chemical cue that Phyllospadix puts out. Also research can more carefully look at Melobesia's relationship with Smithora and their competition. I started examining the biomechanics of Phyllospadix with Melobesia but did not get a chance to compare it to Phyllospadix without epiphytes and if the epiphytes make it stronger or weaker. In addition, future research could investigate on which part of Phyllospadix the Melobesia colonies occur, since they mostly seem to be found at the tips on real surf grass. Other research could include how much wave action does surf grass need to be in for Melobesia to live in because from my observations it preferred areas of high flow.
Many many thanks to Mike Vassar and Judith Connor for their creativity and helping me get the materials for this experiment. Also huge thank you to Caren Braby who helped me set up and follow through this study.
© 2001 Melissa Roth