Peter Sheesley - Week 2, The Rubber Hits the Road

Week two was a full week and several new activities were undertaken. Overall though, it was mostly spent looking at plankton under the microscope. I’m surprised how simply spending more time looking and attempting to classify organisms really does improve my familiarity with them, and my ability to differentiate between them. Now that I know just a little about the various phytoplankton and zooplankton, instead of seeing just a mess of squirming organisms, I instinctively categorize what I know and pay special attention to new or unknown shapes and movements. I suppose this is like the difference between two people watching a football game when one of them knows all the rules and offensive/defensive mechanisms, and the other person sees 22 people sporadically running into each other.

We went to Bastendorff Beach and Arago State Park to collect water samples using our well bailer tool. Bastendorff has an area with a wide surf zone and we took several samples there, on either side of a ridge. There is also a rock outcrop where we took some samples straight down from the rock, into a very narrow surf zone. We then headed south to Arago State Park and climbed down a steep cliff to a rock shelf in the surf zone. This was a bit more dangerous because a sleeper wave could cause one to lose footing and be swept out on the slippery rocks. Using much care, we got as far out as possible and threw the bailer into the surf. We kept samples, but probably didn’t get the sample from far enough out. The water samples were kept in approximately 250 mL plastic containers and preserved with lugols (iodine) drops.

Back at the lab we counted phytoplankton in the collected samples during the rest of the week. We are counting Chaetoceros (abundant diatoms consisting of spiny chains of discs), Pseudonitzschia (diatoms like spikes laid end to end), Dinoflagellates (a variety of shapes, with flagella and usually a reddish center), and Navicula (a unicell, pennate diatom). The Sedgewick-rafter slides hold one mL, so we count how many of each type are in a one mL concentrated sub-sample to get an estimate of how many would be in a one liter sample of the original. We only counted about ten samples, but so far our results seem to support the basic theory that more plankton are present in dissipative surf zones than in reflective surf zones.

We also spent a few mornings during week two tagging limpets for a separate research project of Dr. Shanks’. Specifically, we were tagging the limpet Lottia scabra, on the rocks in the tidal zone below Cape Arago. Tagging them involves sticking a small, lentil-sized piece of epoxy to the shell, and putting a small, numbered plastic tag in the epoxy. At first, the L. scabra limpets were somewhat difficult to find among the many Lottia digitalis limpets present. With a little practice though, finding them became easier. In general they are isolated, have sub-grooves between their main grooves, and have an apex that doesn’t tilt to the side. In addition to being tagged, each limpet is photographed. This will allow for future measurements of growth rate. It was interesting to see the algae-cleared circular area around some of the limpets that makes up their feeding zone. Apparently they move out into the zone to feed and then return to the same spot for years or even decades. This makes the spot they call home sometimes slightly depressed in the rock.

The third project of Dr. Shanks' we are occasionally participating in has to do with keeping a daily running count of crab larva and juveniles collected in a light trap off the nearby docks. For us this only involves retrieving the sample (emptying the trap into a bucket), if we happen to be out at the dock also collecting plankton. The light trap is a converted water bucket with holes in the sides, an extension chord running in to a light inside the bucket, and a filter at the bottom. At night the crab megalopae (second and final larval stage) are attracted to the light and enter the bucket. There are often polychaetes (worm-like creatures) and small fish in with the crabs. The samples are taken to the lab and counted by another student.

Overall, week two was exciting. We got out to the ocean to tag limpets and take water samples. And we started collecting data on our samples. Also, I continued to improve my plankton identification skills.

A clear indication of tilt in the rocks at Cape Arago. This affects the rocky surf zone nearby.

Me; casting the well bailer by hand into a reflective surf zone at Bastendorff Beach.

Some of the crab megalopae from the light trap.

A Lottia scabra limpet with a fresh tag. This one happens to be numbered "007" and named "Bond, Limpet Bond" :)

Me; demonstrating the process of attaching epoxy to a limpet.

Leyia, Dr. Shanks, and Pushkin arriving on the beach at Cape Arago to tag limpets.