This week I've been busy collecting many samples of Gracilaria and running feeding assays. When Gracilaria is grazed on by herbivores, it turns on a defense full of chemicals that make the herbivores not want to eat it anymore. I want to find out whether or not all parts of a plant turn on these chemical defenses when it's grazed on by herbivores or if only the nearest part of the plant turns on the chemical defense. I took multiple individuals of Gracilaria and ground the tip of a plant (which is similar to an herbivore eating that tip!). I then put a piece from this ground area of seaweed in a container with a piece of seaweed that wasn't next to the part that was ground. I then put an amphipod called Ampithoe valida (they look like tiny green bugs that live in the ocean) in the containers to see whether the amphipod will eat the ground seaweed or the unground seaweed. I will be checking the results tomorrow! I predict that the amphipods will eat the seaweed that was unground because I think the chemical defenses won't be turned on where I didn't grind the seaweed and that the pieces that were ground won't taste good because the chemical defenses will be turned on! 

I've been playing around with exposing Gracilaria samples from our mudflat to hot and cold temperatures to find out the limits of what they can survive. I'm trying to figure out the best set of methods for doing this. So far, I've done 3 heat assays and 2 cold assays. For the heat assays, I've exposed samples to temperatures between 30-50 degrees Celsius (or 86-122 degrees Fahrenheit) for time periods of either fifteen or thirty minutes. From these experiments, we've found that samples exposed to temperatures of ~44 degrees C and above will die, samples exposed to temperatures of 30-34 degrees C are mostly okay, and samples exposed to temperatures in between these showed some variability. I attached a couple of graphs-the x axis has the temperatures and the y-axis shows the bleach index, which is basically a ranking of how bleached the samples are (5 means they're totally bleached and 0 means no bleaching).
For the cold assays, I've put samples in the freezer at -20 degrees C for varying periods of time, ranging from 5 minutes all the way up to 1 hour. I found during this experiment that the water that the samples were sitting in froze after just 10 minutes. I checked the samples a week after exposing them to the freezer and found that even the samples that had spent an entire hour in the freezer looked perfectly healthy-so this is a pretty tough seaweed! Next week, I'll keep some samples in the freezer for up to four hours to see if I can figure out how long it takes to freeze them to death!