We’re in full swing now. The divers are jumping in and out of holes in the sea ice of McMurdo Sound, taking pictures, videos, and cores of Stacy’s 14 long-term monitoring sites. Stacy has been checking these sites since 1988 and is looking at the changes in these soft-bottom (mud) communities. They’re also taking pictures of a place called “Dayton’s Wall” which Paul first took pictures of in 1967. There are about 30 places on this underwater wall that Paul tagged, which the divers are returning to this year to photograph so Paul can see what has grown and changed in these hard-bottom (rock) communities.
SCINI is also diving in and out of holes as the engineers refine tracking and vehicle control while looking for Paul’s old experiments. Paul has cages, plates, and floaters in various parts of the ocean down here at McMurdo. Yesterday we successfully pulled out the first of these experiments at Dayton's Wall! It was a big moment.
After 36 years of being in the ocean, what will we find?
These first two experiments were floater; they had buoys on top, a rope going down, 10 on each settling plates in the middle, and an anchor on the bottom to keep the whole contraption down on the seafloor. These floaters were originally put down in the water by Paul in 1974 – 36 years ago!
Paul gets his first glimpse
We had two of McMurdo’s best divers, Rob Robbins and Steve go out to the site and attach float bags to the site so they could swim the floaters from their designated spot to the dive hole. They then used rope to attach the floaters to the top of our dive hole. DJ, David, and Bob then created a pulley system to help them pull the floaters out of the water.
What did this seal think of us removing this old experiment?
DJ, Bob, and Paul pull all the rope and settling plates out
They pulled and pulled and out came about 30 feet of rope, plates, and creatures galore.
The complete anchor, line, and settling plate experiment is out of the water! What will we find?
Paul found sponges and lots of other interesting animals!
A worm, soft coral (red) and sponges (yellow)
An arthropod - can you see his eyes?
We’ve now carried everything back to the Crary lab where Paul is analyzing the organisms carefully. Paul is looking at three different things concerning these bottom-dwelling animals. First is the question of what baby animals, known as larvae, can swim. Animals that live on the seafloor reproduce in three main ways. Some animals, like many kinds of sponges, reproduce by budding. A tiny piece of sponge breaks off from the mature sponge, settles on the seafloor, and grows to create a new sponge. These sponges usually crawl to their new spot. A second type of reproduction involves eggs being fertilized. Sea stars reproduce in this way. The female sea star has eggs which are fertilized by the male sea star. The female then broods her eggs for up to three years before tiny sea stars are released. These baby sea stars also crawl to their new location. The third type of reproduction, used by other sponges, tunicates, and hydroids, is more complicated and involves crawling or swimming larvae.
Hydroids (the pink ones) and sponges (the tan ones) - How did they get on a plate 15 feet above the seafloor?
Paul’s settling plates, which are about 5 and 10 and 15 feet or more above the seafloor, shows us which of these larvae can swim. We know mature animals such as sponges and tunicates cannot swim. Thus, if we see an animal on the settling plate, we know its larvae had to and, more importantly, it can swim to get to a new location. This has never been shown before as the life cycle of these animals is very long and changes cannot be seen in one season. With a span of 36 years and a huge collection of creatures, these plates will document what bottom-dwelling animals have swimming larvae. Paul’s experiment also shows what happens when the major predator on the seafloor, the sea star, is not around. Since sea stars cannot swim or climb a rope, the animals on the settling plates are safe from them and we’ll be able to observe what happens in such an environment.
hydroids and sponges - how old are these?
Lastly, Paul’s experiment will give us a long-term perspective. We can see what has happened over a 36 year time period. Paul observed the sites in the 1970’s but did not see much change. He then saw them in the 1980’s when something happened as they suddenly became heavily encrusted with organisms. He does not know exactly what happened. Why did all the animals settle during that time? What could have caused that? I don’t know if we’ll find an answer to that but we will see what has happened since then. What do you think we’ll find and why?
a smiling Paul with his first experiment to analyze