Usually when people say “Enter the water, enter the food chain” they are talking about big aquatic predators like sharks. But I think it applies equally to itty bitty teeny tiny things. After we pick all the big things out of our sample, we sieve the water. This concentrates all the tiny animals. We then use a microscope to count all the little critters. Every year it amazes me how many super tiny animals live in the sea water. It also makes me wonder what things swim inside my ear every time I go swimming in the ocean. If they are swimming in my ear, are they also taking little nibbles in there?
The most abundant little critters in the water are copepods. Copepods have a huge range in size. Some we can’t see at all without a microscope, others we can see as little flecks of color with the naked eye.
In the picture above you can see Paraeuchaeta, the biggest critter in the photo. Paraeuchaeta is a rather large copepod that we can often see as a orange dot flitting around the large sample. Under the microscope we can see that it has two huge arms that it keeps curled up under its mouth. Next to Paraeuchaeta you can see a bunch of smaller clear copepods. These are Metridia and they are the most common, and abundant copepod we get in our nets. Also in the pic above is a chaetagnath (it looks a bit like a weird arrow coming in from the right side of the photo). You might remember me holding a huge one at the end of my last post. This small size is much more typical for chaetagnaths in the world oceans.
Copepods have a fun diversity of shapes. Two fun ones that are easy to recognize are “orange brushy feet” and Heterohabdus sp. Oddly enough we don’t know what species orange brushy feet is, but the orange brushy feet are unmistakably adorable. The Southern ocean copepod keys are also unmistakably difficult to work through, so the exact nature of good old orange brushy feet remains a mystery.
Heterohabdus sp is a nice big copepod. It usually has beautiful orange oil droplets inside of it. It also has tremendously long antennae and a long cetae (hair) coming off its tail. Female Heterohabdus have “lady lumps”, or a bulge on either side at the base of the tail. You can see one of the lady lumps on the copepod pictured above.
In earlier blogs I have shown you what grown-up krill, T. mac, Frigida, and Triancantha look like. Well, we also get very small early larval stages of these guys. These early larval stages look nothing like the shrimp like creatures they will grow up to be, but we can still tell them apart. The most common larvae we get this time of year is the C1 stage of Euphausia frigida. We also get the C1 stage of E. triacantha. As is true for the adults, the triacantha larvae are bigger and more colorful than the frigida larvae. The triacantha larvae also have a rather conspicuous spine protecting their tails.
Another cool thing we get in our samples are radiolarians. These are crazy looking spikey balls. If these things were larger they would be terrifying weapons. But since they are small they are beautiful and really fun to find in the sample.
Another class of animals that we find using the microscope are polychaete worms. We can identify about 5 species of polychaetes, but there are so many more species here.
I really do love looking at all these little critters under the microscope. We all do. You can frequently hear us greeting the animals, telling them they are gorgeous, and calling other team members over to look at particularly cool critters as we do our microscopic counts. Zooplankton are just amazing… but I still don’t want them in my ears.