Dive Dry with Dr. Bill

#382: Spaghetti Alga... But No Sauce?

My doctoral research was in the field of phycology (the study of algae) yet I spend most of my time in these columns talking about fish or invertebrates. People just aren't as interested in algae, or "seaweeds" as most refer to them. They don't "munch" much, and their reproductive patterns are not in the least bit titillating, so many of my readers have less interest in them. I have written about the pernicious Asian exotic kelp that has invaded our waters over the last five years, but mostly I keep my observations about the primary producers to myself. This week I decided it was time to talk about one species in our waters, the spaghetti alga. For those who aren't aware, alga refers to a single species of these photosynthetic "plants" while algae refers to more than one.

Although people often refer to algae as "plants" because they photosynthesize, scientists look at them in much more complex ways. The primary classification of all living things is broken down into Kingdoms, of which there are generally five widely accepted ones. The Monera are single celled or colonial and include the blue-green algae. Kingdom Protista includes one- and many-celled algae that have a flagella or cilia. The Kingdom Plantae includes our land plants, the green algae and a few marine grasses. Fortunately there are no algae in the Kingdoms Fungi or Animalia. Of course there are other classification schemes that create six or as many as eight different Kingdoms. We as humans have what writer John Fowles referred to as the "categorical imperative..." we want to classify everything into groups that are meaningful to us. However, different people (including scientists) use different criteria to classify living things. When scientists first looked at algae, they placed them all in the plant kingdom because of their similarity to land plants. Both produce their own energy by capturing sunlight to power the chemical combination of water and carbon dioxide to produce carbohydrates, such as sugars, which can be stored for later use... or devoured by herbivores who are then consumed by carnivores.

Now to me the only classification we can reasonably bank on is that of the lowest level, the species. Most levels above that reflect human judgment calls. However even that fails us at times when scientists do not recognize the subtle differences between groups of organisms that would make them separate and distinct species. And sometimes scientists separate groups of organisms into separate species when ultimately we discover they are all the same. The first approach is known as the lumpers, while the second is the splitters. Of course splitters sometimes have ulterior motives in separating organisms... such as getting their name placed on the newly described "species." I think of one of my Harvard mentors, Dr. Ernst Mayr, who told the story of when he was studying birds in the jungles of New Guinea years ago. When he compared notes with the aboriginal people who lived there, he discovered they had readily identified all but one based on their knowledge of the birds from hunting. So much for a costly university education!

Back in my first year of graduate school, I was required to collect at least 30 species of algae for my phycology class. I did my collection here on Catalina during one of my school breaks. The professor, Dr. Mike Neushul, was one of the world's leading authorities on kelp and algae. When he evaluated our collections, he called in three other scientists to look at them. They ended up disagreeing on about half of the species I had collected. I quickly learned that even the experts can't always identify a species based on sight alone, unless they use a microscope or look at their DNA. Many of the algae in our waters exhibited different morphological characteristics, that is physical appearance, because the environment on our calm, leeward side was differed from the more exposed coast off Santa Barbara where I was in school.

One algal genus that is difficult to mis-identify is Chaetomorpha, and that is the subject of today's column (finally I'm getting to the point, and I don't mean Casino Point!). The algae in this group, known commonly as spaghetti or green hair algae, grows with new cells extending off the older cells to form linear, unbranched filaments that are often very curly like the hair of a woman who has had a bad perm. To fishermen it may look like a tangled mass of St. Patrick's Day monofilament line (and they don't have to drink green beer to see it). I filmed some good examples of it on last weekend's dive at Casino Point.

Aquarium enthusiasts may recognize Chaetomorpha as a species sold in that trade to remove excess nutrients introduced by the excretions of marine animals... you know, the "fish poopies." The other genus formerly used for this purpose, was Caulerpa, but it has been banned in the US because it can escape from aquariums (with human help) and become an invasive exotic in our waters. Another reason Chaetomorpha is preferred is that Caulerpa "goes sexual" in aquariums, expending most of the nutrients it takes up when it releases its gametes. Chaetomorpha does not "go sexual" (I guess some scientists might classify me with it using that criterion!).

The genus Chaetomorpha is fairly cosmopolitan and species are found in many places around the world. Some will live in brackish or even fresh water. The species pictured here, Chaetomorpha spiralis, is known from throughout the world with the exception of the polar regions. Some species of Chaetomorpha attach to the substrate and create a low growing turf, while others are unattached. The one pictured here begins life by attaching to the substrate, but later breaks free and tangles up with other attached algae to keep it in place. As suggested above, these algae can reproduce asexually by releasing zoospores or through fragments that break off and drift away; or sexually using gametes with whip-like flagella to propel them towards one another. In addition to the flagella, these gametes also have "eyespots" or light sensitive regions which may help them identify the most beautiful or handsome gamete of the opposite gender!

Hmmm... after researching this week's column, I guess there really isn't all that much to write home about with regard to this alga. It really is a bit boring to those of us who spend our hours underwater watching vicious predators pounce on unsuspecting prey, or two to a dozen or more individuals interacting in complex courtship rituals and... um... mating behavior. Algae may be a bit boring compared to those exciting behaviors, but there are two facts we humans need to keep in mind about them. Without algae, including planktonic ones, there would be far less oxygen in our atmosphere to breathe (gasp). And without algae, what would all the marine herbivores and their predators (and eventually us humans) munch on? So this rather unusual looking mass of chlorophyll-tinted spaghetti, and all the other "seaweeds" in the ocean, actually has a pretty vital role in our marine ecosystems... and planet Earth! Maybe now they'll get some respect!

© 2010 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Images of Chaetomorpha spiralis in the Casino Point Dive Park.

This document maintained by Dr. Bill Bushing.
Material and images © 2010 Star Thrower Educational Multimedia