Hi all, this is Dr. Edwards, project PI
Our second cruise to the Aleutian Islands has come to a close. On July 23, we finished our last set of dives at Yunaska. Yesterday’s rocking and rolling swell was non-existent; the winds had died down completely, and the sun had come out. Yes... the sun. It had been almost two weeks since we saw a clear view of that yellow star that warms us. We went in and hauled our chambers and the hundreds of pounds of chain to the boat and picked up the sensors. The water was so calm, you could set things down and they did not move. The thick kelp that only the day before had snagged on every edge of our tanks, BCs and regulators, now cooperated as if we were in harmony. You could move through it with ease, but only if you respected it...danced with it. If you took it for granted, tried to change the dance, it would still snag and pull on you, slowing every movement. But with respect, it was like gliding through a photograph.
The kelp was so thick and full of life. There was an understory of kelp so dense you could not see the bottom. There were sponges that covered square meters of rock bottom. Red, yellow, white. There were large nudibranchs plowing through the sponges and eating their fill. There were snails, and bottom fishes of every color you could imagine. Visibility was so good that the only thing that limited your vision was the scenery in front of you. Though you could if you wanted to, it was hard to pass up an infinite number of scenes in front of you that you almost forgot there was a horizon beyond. It made me completely forget the 41 degree water and the holes in my gloves’ fingertips that appeared after two-weeks of deploying benthic chambers, hauling chain, and collecting urchins.
Afterwards we had a day of cleaning gear, packing research equipment, and preparing to disembark from the Oceanus. This is my last shipboard blog for Brenda's and my NSF 2016 and 2017 cruises. In reflection, I look back at what we accomplished. In the past two years, we dove at 15 of the Aleutian Islands (from west to east: Attu, Nizki, Allaid, Shemya, Kiska, Amchitka, Ogliuga, Tanaga, Adak, Atka, Yunaska, Chuginadak, Umnak, Anangula, and Unalaska). My students (Scotty, Tristin, Pike, Sadie and Genoa) and my collaborator Ju-Hyoung pulled off a Herculean amount of work. We deployed nine benthic respiration chambers at each of 11 of the islands; three each in the kelp beds, urchin barren grounds, and in the transition zones between the two. This equated to 99 chamber deployments in total. Each chamber was held down with about 40 pounds of chain, so you can do the math; we deployed and retrieved about 3960 pounds of chain from small inflatables. This, plus the chambers and the sensors…again…Herculean. Together, we did about 250 dives on each of the cruises (about 500 dives total on the project). Conditions ranged from Atka last year where we endured smashing waves and blowing winds in our sites to the calm clear beauty of Yunaska. Water temperatures ranged from 41 degrees to a balmy 46. My students (the SDSU BEERPIGS) more than conquered these tasks and I am grateful and impressed by their abilities, energy, and attitudes. A job well done.
On the ship, Ju-Hyoung and Sadie conducted controlled measurements of invertebrate respiration and algal photosynthesis. Generating photosynthesis versus irradiance (P vs I) measurements requires careful and methodical work. The instruments we use are sensitive to even a single degree of change in water temperature, and to differences in light intensity so small that the human eye cannot make them out. Each measurement for each species requires up to 90 minutes to fully evaluate the photosynthetic responses of the algae to changes in irradiance. Between the two of them, they conducted a total of 150 P vs I measurements across 26 species. In total, this equates to about 225 hours of measurement time (and that’s in just four weeks of ship time). Further, they conducted respiration measurements on dozens of species of invertebrates, and evaluated the relationship between urchin respiration and urchin size across nearly 20 size classes. They also examined the carbon uptake kinetics of 10 species of algae, and helped parameterize our field irradiance measurements with light casts. Another job well done.
On top of deploying and retrieving chambers, Scotty collected tissue samples from about 400 invertebrates, and 101 water samples that were filtered for phytoplankton. Over the next year, he will analyze these for their isotopic signatures to better understand how food webs and trophic energy flow has changed with the widespread kelp loss.
Together with the benthic respiration chamber data I see my next several months of work analyzing and interpreting the results. And then writing up the papers. Not as fun as being underwater, but just as important and rewarding.
The crew of the Oceanus was amazing. From the captain on down, everyone was friendly and incredibly helpful. Our skiff drivers navigated the dense kelp beds, and helped haul heavy chain and chambers into the boats. They were both our drivers and our surface support. The food was awesome, from fresh-caught baked halibut to hot out-of-the-oven cookies waiting for us when we returned from our dives, worn out and cold. We could not have asked for a better crew or ship. I thank the National Science Foundation for providing both the ship and the funding for this research.
So, as I close this blog, I think about the next time Brenda and I will bring our labs here. It has been almost 25 years since I first came here to live for a few months on Shemya; this place is as beautiful and new as the day I first stepped on that tiny island (though I am a little greyer and maybe a step slower). The ecosystem offers an endless avenue of research questions and our research (as most research does) has resulted in as many new questions as it provided answers. So, I think of the last dive at Yunaska, sitting mid-water and looking at the dense kelp teaming with life. I think of the urchin barrens, which at one time looked to me to be devoid of anything other than urchins, but now have revealed themselves to be diverse and full of their own life. What will happen next? How long will the urchin barrens persist? What might cause them to switch back to kelp beds? New predators? Disease? Some as-of-yet unknown factor? The questions remain. I think about the last dive, and I believe the Aleutians are calling me back.
Dr. Matthew Edwards