Scum of the Earth
is often called yellow-green algae because they lack the brown or golden pigment (fucoxanthin) that is indicative of green algae, another family group. A different type of cholorphyll, chlorophyll c, is responsible for this slightly different coloring. Within Xanthrophacae family, all but three species are rare, Botrydium, being one of the more common species. Overall, xanthrophytes are generally found in freshwater, wet soil and tree trunks and do well in low pH habitats that are rich in iron.
Another interesting tidbit of information that I found was that many xanthophytes produce a cell wall, but no one has tried to figure out what it is made of other than perhaps some bits of silica. What we do know is that it isn’t cellulose, like plants, or chitin, which would be similar to fungus. For those that get into the evolution of rudimentary plants, there is a theory that these algae evolved from unicellular organisms that engulfed algae and assimilated their chloroplasts. While these bits of trivia were great for useless knowledge, they really didn’t tell me why they were at Duck Creek.
I dug a little deeper and had trouble finding anything recent that had a good general description of this species. I attribute this to the location (transition between wet and dry habitats) and non-confrontational nature of this algae. Blue-green algae gets a lot of press these days because of its destructive nature and seasonal explosions due to excessive nutrients from run-off in our altered watersheds. Not much money is funneled towards an inconspicuous, round plant that occurs on mudflats every now and then.
However, I did find multiple descriptions from biologists documenting the plant a hundred years ago, when natural history and the general description of species of the world was still in vogue. The Algae Britannicae, descriptions of the marine and other inarticulated plants of the British Islands belonging to the order of Algae, by Robert Kaye Greville, 1830, gave a good description of the plant, although he himself couldn’t procure a fresh sample of the species to aid in his narrative. Other sources that I found were dated between 1890 to 1944.
Cluster of Grapes
In Greek, Botrydium means a small cluster of grapes, which is appropriate enough. It is an ephemeral algae that can occur in the spring and fall. This partially explains why I was able to find it more readily available during cooler weeks than during one of our hot spells. When present this species can be found on the banks of freshwater lakes, ponds, rivers, streams, ditches and apparently wetlands as well. It was noted that it can occur in shady locations within these habitats, so perhaps this is another indication of a cooler temperature regime. Or this just could be an indication of where the mud stays saturated at the right condition longer.
An article from the Botanical Gazette in 1943 noted that at a site in India “it covered a large area, particularly on patches manured by the droppings of wild ducks and geese.” This is interesting to me because the locations in Unit A and at Dark Cypress also had been heavily utilized by waterfowl this past fall and spring. Although, this algae may not cause pandemic blooms and fish kills, perhaps in their own way they do respond positively to a little extra nutrient loading.
On another little sidenote on how this species may fit into the grand scheme of things, one of the times I was scraping a thin sample of mud to take back to the lab, I couldn’t help but notice that there was a trail crossing one of the clusters of yellow-green algae. Perhaps a snail was hovering along and sucked up the algae, thereby converted the nutrients into metabolizable energy and taking these calories into the next trophic level. Now I’m just speculating, but this snail could then be devoured by a freshly hatched wood duck who would be trying to grow big enough to start his big annual journey this fall, thereby illustrating the connection of food webs and importance of a lowly, forgotten species of a group often referred to as scum.
Although it did take some effort, I have to admit I enjoyed the chase and learning about something new. No doubt, this fall and coming spring, I might be found with my nose close to the damp ground. It might be silly. It might be just algae. But for me, this species represents the need for a wider awareness of our surroundings and understanding of what is going on in our own back yard. To some it may be scum of the earth, but I see them as part of the sweet fruits, grapes more precisely, of our wetland ecosystems.