As our trip nears its end (we only have 3 more work days left in Mo’orea!) we are using our last few days on the island to collect the final pieces of data for all of the projects that we have spent the last month working on. Yesterday, my algae group (nick-named 3D since we are the only 3-person group in the class that is made up completely of SCUBA Divers) finished the last of our nutrient limitation experiments using the algae Padina. Four days previously, we put pieces of Padina in small mesh bags made our of window screen, and then put those bags in plots of Turbinaria (the larger, spikier algae that is all over our study site) to see the effects of Turbinaria density on nutrient cycling. In some of the plots, we placed bags of slow-release fertilizer next to the bags of Padina, and in others we left the algae to just absorb whatever nutrients are naturally in the water. We manipulated a few things about the plots (the density of the Turbinaria, the presence or absence of nutrients, and the presence or absence of other kinds of algae that grows around the base of the Turbinaria) to see how the density of Turbinaria affects the availability of nutrients for other algae to use.
After letting the Padina sit out there photosynthesizing away for 4 days, we pulled it out of the ocean and weighed it to see how much each piece of algae had grown under each of the different circumstances. But between pulling out algae and heading back to the lab, 3D took advantage of the left over air in our tanks and dropped down the edge of the reef to check out the cool fish and coral down there. Our algae experiments have all been at depths of 3-6 feet, so we were excited to dive down 30 feet below the surface and play with the fish and sea anemones down there.