Week 4 was another busy week! Here are some delightful highlights!
Monday 11/5
Upon arriving to lab in the morning, we were excited to see that our preliminary agar tests had gone well! About 5 snails were gathered around the agar plate containing crushed algae. It had many chunks missing; it was evident that a lot of grazing had taken place. The plate with just agar and no algae had also been grazed a fair amount, but no snails were on it at the time of our observations. Since the preliminary tests were successful, we got working on making agar squares (bladed, spiky, and an algae-less control). The agar is surprisingly fun to make and cut into squares. Valerie and Kaylee were definitely tempted to take a bite of the gelatinous cubes on several occasions...
In the afternoon, we did another set of fish surveys at Lion's Head and Big Fisherman's Cove. It was a hot day and there was some wind, and the visibility was bad compared to previous days.At a plot in Lion's Head, we observed a cormorant down at 20 feet chasing a school of mackerel. It was really surprising to see the bird, and it seemed surprised to see us as well!
It is increasingly apparent that our plots serve as refuge for juvenile fishes. Juvenile kelp bass rock wrasses arevery common at both sites. This is something we should discuss in our paper and find references to support our observations.
Tuesday 11/6
After setting up our snail trials, we went to the computer lab to analyze some of our statistics in JMP (a useful analytic statistics program) for the ecological project. Since we had about 8 days left to do experiments, we wanted to make sure that the fish survey data we were collecting and putting so much time and effort to was generating significant results. We took the average number of fish over all three observers for each plot, imported that table into JMP, and computed a two-way ANOVA on our data. ANOVA, or Analysis of Variance, is a good statistical tool to make clearer comparisons between means.
To perform a two-way ANOVA on our data, we have to make sure our data follows several assumptions: the data must be normally distributed, observations between groups and within groups must be independent, and the variances among the populations must be equal.
First, we took the average numbers of fish for each treatment (BFC kelp, BFC sand, LH kelp, LH sand), fit a normal curve to the data, and used the Goodness of Fit function in JMP to see if they followed a normal distribution. We also learned a little about data transformation to make our data appear to be normal so we can run the ANOVA tests. Its not the most interesting of processes (a lot of trial and error and playing around in JMP), so I'll spare you the details!
After "testing the assumptions", we tested how equal the variances were through JMP. Our variances turned out to be sufficiently equal! We also ran some other tests to examine significance and interactions. All in all, our results are significant enough to consider more fish surveys both relevant and useful!This afternoon we went to Isthmus Reef to collect Dictyota for practicing our invertebrate counting methods, as the deadline for plot collection is swiftly approaching and we have yet to completely standardize our methods. After spending some time around 50-60 feet for sightseeing purposes, we carefully collected 14 Dictyota plants. Back at the lab, we utilized window-screen mesh, freshwater rinses, and forceps (tweezers) and got to work! We found hundreds of invertebrates on each plant, including juvenile snails, amphipods, shrimp, caprellids, eggs, small decorator crabs, brittle stars, and isopods. In addition to getting a baseline of critters on each plant, we also tested the efficacy of freshwater rinses by treating some plants just as we had prior to putting them back into the field on our plots. We found the 30 second rinse to be very effective, which was great news.
We also discussed possibilities for quantifying the animals small enough to pass through the window screen, and decided that using a plankton wheel was probably the best method to subsample the tiniest of critters.
Wednesday and Thursday continued the pattern of morning Lithopoma agar trials and afternoon fish surveys. As the days went on and a pretty intense wind began to set in, the visibility definitely decreased due to the turbulent conditions. One such afternoon when fish surveys would not have been useful, Kaylee and Valerie helped out fellow team ShredEx by going on SCUBA and collecting Pisaster giganteus, the giant sea star, and later collecting small Tegula snails in the intertidal. Despite it raining, we all had a good time. Having the afternoon "off" was a great relief since tomorrow (Friday, 11/9), is our first collection day at Big Fisherman's Cove, and the wind is sure to be very strong and a Small Craft Advisory is to be implemented, which will prove to be troublesome.
The last photo is credited to Sam of ShredEx. You should check out their blog at:
http://shredexmbq.blogspot.com/
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