Scum of the Earth
So at the beginning of May I was checking on things out at Duck Creek and stumbled upon something I hadn’t encountered before. Originally, my attention was attracted to the drops of dew clinging to the spider webs on the surface of a mudflat in Unit A. I took out my camera, switched on the macro function and got down on my belly to take a few photos. From this new point of view I began to notice something else that was intriguing…little green orbs or spheres scattered across the top of the ground. You could almost call them clusters of tiny grapes ranging from 0.5-2 mm in diameter.
I started looking around and saw there were quite a few of these small circular structures clinging to the moist soil surface. I guessed they were some sort of algae, but thought it would be fairly easy to identify once I sent my photos around. Later that day I was out at Dark Cypress, and once again my attention was drawn to the mudflats. This time I was intrigued by a small pink mite. This little bug was racing around too fast for me to get an adequate picture, but the camera did capture more small green spheres. With my bare eyes, I could barely make them out; but other than their small stature, they appeared to be similar to what I had seen in Unit A.
I sent them to our ombudsman, Tim Smith, and got a couple suggestions from folks within the central office, but nothing definitive. I also sent a couple inquiries to several university professors. I was told I needed to take a closer look under the microscope to see the filaments of this species for proper identification.
That next week I went back out to Duck Creek in an effort to grab some samples for the lab. The continued heat and evaporation had caused the distribution of mudflats to shift, but after some searching I was able to find the green spheres of algae. However, you couldn’t just roll them off of the mudflat without popping them. They were like balloons shallowly rooted in the soil. I cut a thin slab of mud that had a good patch of orbs on top and brought them back to the lab.
Under the microscope, I couldn’t find the filaments that I was supposed to find to help in my identification. All I saw was a thin membrane incasing even smaller green spheres. Perhaps it had been too long since my days in microbiology class and I wasn’t using the instrument right. Despite my lack of finding anything significant, I was able to take some photos to pass on as I continued my search.
I followed up with Dr. Bornstein, a botanist at SEMO. He had offered his services earlier on if I couldn’t figure out the identity of my specimen. This included another trip out to Duck Creek and another search for the right mudflat conditions. Back on campus, and under the scope, Dr. Bornstein, like myself, did not find what he was expecting to see. There were no filaments to these algae. He gave me the name of another professor who might be able to help with my quest.
Upon contact, he was interested and I sent him the photos and description of the habitat where I had encountered these small plants. After a week, he replied and reported that he couldn’t put his finger on it, but might be able to identify it by keying out a fresh specimen.
So it was back out to the dried up wetland for another sample of this clearly unpopular, nondescript algae that I was now hell-bent to identify. Since my potential lead had temporarily dried up, I decided to cast another academic net to see if anyone else could identify my photos. Finally, I got a hit. Not a direct one, but definitely in the right direction.
Dr. Nobles is the curator of The Culture Collection of Algae at the University of Texas, Austin. They have approximately 3,000 different strains of living algae, representing most major algal taxa. Cultures in the Collection are used for research, teaching, biotechnology development, and various other projects throughout the world. His response was, “Very interesting stuff! I have not seen anything like this before, but I showed the images to a colleague and I believe he came up with an ID. I think the algae you have is the xanthophyte Botrydium.”
At last, I had a name of a species that matched the characteristics of my mystery plant.
The next step for me was to learn more about this known strain of algae. That shouldn’t be too hard, right? A little digging provided some basic background information. Xanthrophytes are different from the more common and problematic blue-green algae. This group 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.