Thursday, April 8, 2010

Jenna and Mandy on a Boat (Part 2 of 2): Science at Sea

Now let's do some science! As I mentioned in the previous post. Jenna and I were on the trawl shift from 8-noon and 8-midnight. During each 4 hour shift there were between 3 and 5 trawls. Each trawl had 10 minutes of bottom time and several minutes going down and coming up. A trawl is basically a giant funnel shaped net with wooden doors at the front that keep the net open as it is being pulled through the water along the ocean (or whatever body of water) floor. I can't tell you too much about the physics of it, but when you pull the net up, you untie the narrow end of the funnel and dump out the critters. This is when the biology part begins. As we sorted through the critters on deck the fish could go together in one or more giant fish bucket(s), but the invertebrates were sorted by level of aggressiveness with swimming crabs and stomatopods (mantis shrimp) being separated from more delicate animals like squid.

If you're studying fish, most of your animals ended up nicely grouped at the end of the net near the closure; if you're studying invertebrates then many of your animals have limbs for grabbing, and are probably scattered throughout the net. In the picture below Jenna and are are going through the net to remove animals that didn't make it through to the tied off end, usually starfish and crabs.

Anamar needed specific information for each trawl including total wet weight, number of species, number of individuals of each species, and measurements of some molluscs and arthropods. Starfish were a common theme in every trawl, as were juvenile Penaeid shrimp (also known as eatin' shrimp). In one trawl Jenna had the privilege of counting 453 Penaeids! Animals that we were keeping for the museum went into relaxants, which were different depending on the critter in question.

Most of those animals were photographed and had a tissue subsample taken. Below are some of the lab photos we took of an anemone and a worm with a portion of the shell-covered tube he constructed.

We kept a running illustration of the "Catch of the Day," one for invertebrates and one for fish. Jenna had the invertebrate illustration well in hand, but Jason (the fish expert on board) wasn't confident in his artistic abilities so Jenna volunteered to give the fish illustration a go. It looks accurate, based on the ID, but we're not fish taxonomists so there may be a few errors.

One of our Catches of the Day was this huge Pleuroploca gigantea. It is the largest species of marine snail in this hemisphere. The ruler in the picture with him is one foot long.

Not to be outdone, during the last trawl of the trip the fish team pulled up this giant stingray, which is also the record-holding species for the Atlantic.

He was so big that they couldn't weigh him using the winch and the largest scale available on the boat. All we know for sure is that he weighs more than 100 lbs. He was so big that the crew all gathered at the back deck to get a glimpse of him, although since it was April Fool's Day some people didn't believe the report when they heard it. In contrast to my usual liberal application of random gender assignments to the animals we caught, we actually know that this guy was a male due to his claspers. The females get even larger!

So after our evening shift we usually stuck around the lab and fished up the processing of the specimens for the museum: relaxing, photographing, subsampling, fixing. After our morning shift we pitched in with some of the other activities. During the 12-8pm shift there were several different sampling methods being employed. One of these was a bottom grab which got two different treatments. One sample was homogenized for chemical analysis, and one was sieved and bagged to be sent to another institution. Jenna and I did some sieving to give the usual sievers a dinner break.

We would also take turns catching up on sleep and manning the radio so we could root through the leftovers from the chemistry sample. We found some cool stuff in there including lots of worms and a cool sea biscuit.

Also during this time they would deploy the CTD. I'm sure its full name is very descriptive of its function, and might be useful for me to know now. In any case it took water measurements such as salinity, temperature, depth, current. It can also take water samples, but we didn't take any on this trip.

A few people also did some diving to get a direct observation of the bottom conditions in certain areas. Here they are waiting for the smaller boat to be set in the water to take them to the dive site.

They also had a cool camera thing that they could send down to the bottom that would take video footage of animals within the sediment using refraction, but it's a sensitive piece of equipment and opted not to work this time, although much of the last day was spent staring at it in an attempt to bend its functionality to our will. This picture was taken when we had nearly accepted defeat.

So we had a great time and saw a lot of really interesting stuff! We also found some animals that are new to the collection. Thanks to Anamar and the EPA for including us (hat tip to Jason). Hopefully we can get in on another trip in the future. In the group shot below that's not the OSV Bold in the background; it's just a boat that happened to be at the same dock.

:) Mandy

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