On several cold, windy days this past winter, I did something strange. With fingers puckered bright pink from bitter cold saltwater, I maneuvered what looked like a child’s “butterfly net,” called a No. 2 plankton net, dipping it into saltwater off of the pier at the college, and over the sides of rocks at Kettle Cove with one goal: to collect micro-algae.
I’ve been studying marine botany–the first time experiencing SMCC as a student, rather than as a member of the adjunct faculty. I collected phytoplankton (micro-algae) using No. 2 plankton nets (see below), both at Kettle Cove State Park and off the pier and docks at SMCC this past winter (January-March).
In addition, I accompanied Prof. Megan McCuller to learn how to scrape algae off of the side of the dock and floats in order to obtain a sample of benthic diatoms (and dinoflagellates) that were attached to the side of the dock. I learned how to use the dissecting microscope (my favorite part) in the lab, and I transferred a number of samples to a wet-mount slide to examine the tiny organisms that were drifting and even swimming through slimy green algae. When I say “benthic,” I’m referring to the life found at the bottom of the sea, or in this case,
the bottom of the littoral, or shoreline zone, and sublittoral, also known as the “spray zone,” where the waves crash on the rocks between the high and low tide.
The benthic scrape method yielded the most results (mostly pennate diatoms and one dinoflagellate) while my final plankton tow at the floats on March 20th yielded more results (centric, pennate diatoms and two dinoflagellates) than my previous plankton tows at Kettle Cove or off the pier January-March. My observation was that collecting phytoplankton during the weeks of nor’easters yielded fewer diatoms, or I only collected very tiny diatoms (mostly Navicula sp.). My hypothesis was that ephemeral run-off from storms, high winds and choppy conditions had an impact on those plankton tows.
Is your head spinning? Mine did.
First, it’s important to know that phytoplankton are the “plant” variety of plankton, whereas zooplankton are the “animals,” such as copopods. Here’s a copepod (below), swimming through some Phaeocystis pouchetti, which is not a diatom, but in the genus of algae belonging to the division of Haptophyta. It blooms in March and April, so it dominated several of my samples from plankton tows off of the SMCC pier in early to mid-March. A copepod, however, is an example of zooplankton, a microscopic crustacean found in both marine and freshwater habitats. As an aside, COPEPOD is the Coastal and Oceanic Plankton Ecology database with an interactive atlas on plankton. Pretty cool!
For the basics of plankton, see “Plankton 101: the Basics on Gulf of Maine Plankton and Why You Should Thank Them,” by Sally Mack, UNH Sea Grant.
Below are a few images captured using the Leica microscope at 100x and 400x magnification, calibrated to microns for measurements. I identified fifteen diatoms and three dinoflagellates, some of which I’ll show in a series of posts yet to come. (Side note: I got a 100 on the micro-algae project, which made the cold, challenging plankton tows certainly worth the effort, besides the pure joy of learning.) Phytoplankton are microscopic, photosynthetic organisms. There are two main groups of diatoms and these are pennate (Pennales) and centric (Centrales). For identification purposes, I used a number of guides, including this one developed by my professor, Charles Gregory, at SMCC, and University of Maine Sea Grant. Once under the microscope, these diatoms (micro-algae) are quite dynamic, distinctive and fun to examine.
The golden “bracelet” pattern below is a pennate diatom called Licmophora lyngbyei. I collected several Licmophora during the benthic scrape from the side of the SMCC dock/float on March 20, and identified them under the microscope at 40x magnification. Since it is a colonial, epiphytic type, it is often observed attached to other plants/macro-algae such as in the image below. The cells are characteristically wedge-shaped, with fine striations separating parts of each cell. Cells are united in fan-shaped colonies. To me, it looks like a great idea for a charm bracelet for a marine scientist!
One of my favorite of the pennate diatoms that I collected is Gyrosigma, a canoe-shaped pennate diatom, shown below. It’s very common in the Gulf of Maine. But when we look at these microscopic diatoms, it’s important to note the scale; these are measured in microns because they are so small. In the specimen below, the end of the organism had broken off, and it had begun to disintegrate. That’s why it appears to have jewel-like features, when in actuality, these are other things–including bacteria, that have gotten inside its cellular structure. Another pennate diatom I collected at Kettle Cove had a “bracelet” pattern (at least to my untrained eye); in Thalassiosira nordenskioldii have drum-shaped cells connected by barely-visible gelatinous strands to form a chain. According to Dr. Gregory’s Field Guide to Phytoplankton in the Gulf of Maine, some species of Thalassiosira have been known to cause mechanical damage to fish gills, copopods and invertebrates. For example, this study details several examples, including the impacts of toxins found in Thalassiosira rotula on sea urchins. (Many types of diatoms are examined as part of that study by Gary Caldwell, in Marine Drugs, 2009.)
Thalassiosira is also described as a “harmful species” on AlgaeBase, an awesome resource for those studying algae. It’s a global database with the taxonomic, distributional and other information about micro and macro algae, as observed by scientists all over the world. As a student new to the study of algae, I found it an incredibly helpful resource, even if it helped to direct me to other sources on a species that I had collected for my class project in Maine.
Finally, I will end this post with my favorite discovery–a cool pennate diatom called Chaetoceros gracilis, which looks like something between a Star Wars X-wing fighter and one of the Cylon ships from BSG, if only…in a galaxy far, far away. In many ways, this microscopic marine world is another dimension that’s just as deserving of our fascination. I will post a few more diatoms (and dinoflagellates!) in my next post.