21 July, 2003
Every so often there is another kind of "cast" that we make from the Palmer. Whereas our CTD/rosette casts capture data and water, a Bongo cast catches bugs. That's right, creatures from the deep. You never know what might come up with each cast of the Bongo net: Shrimp, jellyfish, gastropods, ostricods, amphipods, worms, fish larvae, and many other kinds of zooplankton.
The bug of greatest interest, however, to researcher Leopoldo Llinas is the copepod. Leopoldo is a graduate student from the University of Miami who is studying these fascinating creatures under the direction of Dr. Sharon Smith. In fact, this is Leo's second cruise to study copepods in the Arctic, and he even plans to go again next year so that he will have 3 years of data to work with for his PhD dissertation. Leopoldo's enthusiasm for these diminutive bugs is highly contagious for it took only a few minutes in listening to him talk about his work for me to be completely swept-up in his project.
The first thing that you'll learn from Leopoldo about the copepods that he is finding on our voyage is that they are BIG! Calanus hyperboreus is, by copepod standards, a whopper- up to five huge millimeters in size. Most copepods are tiny, or even microscopic, but C. hyperboreus is readily visible to the naked eye. A close inspection reveals a crystalline-like creature with two long, red-colored antennae that stand-out from the transparent body with a golden gut down its middle, and a little more red on what must be its tail.
Another thing about copepods: they are not all the same. C. hyperboreus is abundant in the coldest waters, while Pseudocalanus is more common at slightly warmer temperatures. Calanus glacialis is somewhat intermediate between the two. In all, there are at least 20 species of copepods that Leopoldo is studying. Complicating Leo's task even further are the babies, or in scientific terms, the "nauplia." In fact, C. hyperboreus are surprisingly long-lived. From nauplia to adult, this large copepod may live up to two years. To survive the long harsh winter when the sea is frozen-over, these amazing creatures hibernate (called diapause) just like a bear, although they do it at 1000 meters below the surface instead of in a cozy den.
And copepods eat phytoplankton. This is important because these photosynthetic plankton capture the sun's energy which is passed on to the copepods every time they dine on one of these plant-like critters. Put another way, copepods are the cattle of the sea, continuously grazing on the marine "phyto-grass" that we are rounding-up with each cast of the Bongo net. Together, the phytoplankton and the zooplankton - including the copepods - form the base of the food chain that everything from jellyfish and whales to seals and polar bears, depends on to live.
Right now, Leo is focusing on collecting as many samples as he can, but it seems to me that his real work will begin when he returns to his lab at the university. There he'll use molecular techniques that involve extracting DNA from an individual copepod- including those tiny nauplia babies- that will help him identify various species of copepods, and to determine the distributions of different populations.
But there's even more. An interesting aspect of Leopoldo's project involves comparing today's research to data collected in the 1950s in these very same waters. Indeed, since certain species of copepods are distributed in distinct kinds of salinities and temperatures of sea-water, they can be used as a sort of tracer, or bioindicator of the ecosystem. It is yet another type of data that may allow scientist to assess the extent of environmental change as we try to better understand global warming.
I don't know about you, but thanks to Leopoldo, I can't wait to see what he brings up in the next cast of the Bongo net.
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