Last week Friday was our first lab for Marine Biodiversity. At the moment, the lecture topic is centered around primary productivity and plant life. In other words we’re learning about algae. As a result of that, our lab gave us the amazing opportunity to stare at algal features for 3 hours straight! Who’s excited!? In all seriousness though, if plants aren’t your thing, it wasn’t as bad as it sounds.
Our goal of the day was to become familiar with the different taxonomic groups of algae. The word algae itself is an interesting topic. I’ve always pronounced algae with the “g” sound in “germ.” From what I’ve heard in Australia, they pronounce it with a “g” sound in “ghost.” Gotta love accents!
Anyways… my professor actually studies algae, so she had a lot more planned for us than we were able to get though, but nonetheless, we made an attempt! We worked with partners, moving through the lab manual, taking notes, and making scientific drawings when appropriate.
The first division we examined was Rhodophyta, or red algae. Our mission was to identify the species, identify if a holdfast was on our specimen and label the stipe and blade. In layman’s terms, we were looking if there was a root-like structure (or some form of base attachment), trunk-like part, and leaf-like things. Here’s a short video explaining the different parts of algae, using kelp (brown algae) as their focus.
We were also supposed to look at the color of our plants, and based on that make an estimate as to where they might be found vertically in the ocean. Plants reflect different colors based on the pigments they have and what part of the color spectrum they absorb from the sun. Light that isn’t absorbed by the plant is reflected, which makes up the colors that we see. For example, many of our land plants contain chlorophyll, absorbing red and blue lights while reflecting green. Light in the ocean, however, can sometimes prove to be a problem. As you go deeper, light cannot penetrate as well. Red light is not able to reach the same depths as blue and green lights.
For this reason, some plants have alternative methods of absorbing light in order to cope and survive. They might have an extremely high concentration of chlorophyll, resulting in an extremely dark green color, almost to the point of being black. Alternative pigments, other than chlorophyll, are also used, causing the plants to reflect different colors.
One of the Rhodophyta specimens we had was dark maroon, and the other was pinkish with green in certain areas. The darker plant would be assumed to survive at greater depths and to have more pigments, while the second, lighter plant would be expected to be found living closer to the surface.
The next group we examined was the division Chlorophyta, or green algae, specifically of the common genera Ulva.
We used our dissecting kits to cut of a small piece of the thallus, or the plant body of the algae, and examined it more closely under the microscope, mounting it on a slide with water and a coverslip. We drew the arrangement of cells that we saw and were supposed to determine if our plant was reproductive by looking at the cells around the edges. If the cells were different from those in the interior of the specimen, it was probably developing into a reproductive stage. Unfortunately, none of our plants were reproductive, so I still have no idea what it’s supposed to look like! No biflagellated gametes, quadriflagellated spores, gametophyte, or sporophyte identification for us.
We were, however, able to partially identify a nucleus and banana shaped chloroplasts around the edges of the cells.
It started off as my partner an I blankly staring through the telescope, feeling cross-eyed as we tried to focus on one of the plant’s 2 layers of cells. We eventually found a nucleus, and guessed as to the location of chloroplasts. It was a very scientific method (the guessing). Our professor projected some cells on the screen, however, in order to point out the obscure chloroplasts, which made it much easier to identify on our own specimen. Finally, we took a shot at using a dichotomous key to identify which species we had, and our consensus was U. fasciata.
The next task was to mount Chaetomorpha on a slide and draw the uniseriate filaments. In other words, we were supposed to look and see how the pieces of algae were made up of cells stacked together in a single row, sort of like the beads on a necklace.
We identified the nucleus and chloroplasts, which were completely different from the banana shaped ones in the previous specimen. These were more like a chained web of chloroplasts. They sort of reminded me of the net-like Christmas lights you can purchase that you just throw over the bushes.
Finally, we examined a small piece of codium under the microscope. The cells in this plant were completely different! Rather than the round or unisarate filaments we had looked at earlier, this plants cells looked like little torpedos that had been clustered together. It’s amazing how much a microscope can reveal sometimes.
By that time, our 3 hour lab was up and we were instructed to take photos of the other types of algae that we weren’t able to get to that day.
Overall, we were supposed to gain an understanding of the diversity of marine plants, and I think that was accomplished. There are definitely a lot of different types of algae out there. Algae is an intergral part of our ocean and terrestrial exosystems. Two out of every three breaths you take contains oxygen provided by ocianic primary productivity. It’s amazing! Anthropogenic activities, howeve, can have a huge impact on these ecosystems. Fertelizers, pollutants, and other substances wasehed into our oceans can cause algal blooms, resulting in dead zones, completely depleated of oxygen. Introduction of invasive species, such as sea urchins, can descimate a community of kelp, altering the original structure of life that once existed. This video explains a bit about this relationship:
Tasmania is currently facing the issue of invasive sea urchins.
Amazingly, algae is also being investigated for an alternative source of energy.
Though it might night seem as exciting as learning about vertebrates, such as whales, squid, and sharks, algae is really important in order to gain a basic understanding of the ecosystems that exist in our oceans. They are responsible for much of the life that exists and how that life survives. It’s really an amazing organism.