Taking a break from the moon shots, since my computer is in limbo and I don’t have access to Photoshop to make the moon map. (I do have the images from last night’s moon, though, and will post them soon.)
In a recent post I mentioned that I was a bit confused about the taxonomy of seaweeds. You see, the problem is that they are algae, and algae have a very confusing taxonomy: some of them are in the kingdom Plantae, while others are in the kingdom Protista, and still others are placed as far afield as the Prokaryota! That is, if we don’t follow the people who treat algae as a subkingdom, violating all principles of systematics, as Gavin Maneveldt writes on his no-longer-maintained website, “The World of Algae.” The reason for this confusion is that, according to Derek Keats, “Biologically, the name “algae” is given to a group of organisms of mixed affinity. The word itself has no taxonomic significance whatsoever.”
Having finally managed to procure a copy of Dawes and Mathieson’s Seaweeds of Florida from the library, I can at least begin to answer the questions I didn’t even know to ask before. For example, where do seaweeds fit in the tree of life? Well, according to Dawes, who cites someone named Baldauf,
the phyla Chlorophyta (green algae) and Rhodophyta (red algae) are placed in the kingdom Plantae, while the brown seaweeds (class Phaeophyceae) are placed in the phylum Heterokontophyta and kingdom Protista. There are about 900 species of green algae, 997 brown algae, and 2,540 red algae worldwide (Dring, 1982)
By implication, then, seaweeds fall into three phyla across two kingdoms. Algae, as we already know, have been placed in no less than four kingdoms, so it’s nice that there are two fewer to deal with when we’re talking only about seaweeds. Dawes tells us that there are 693 total seaweed taxa in Florida’s waters, although he cautions that additional records of new species “will no doubt occur based upon future studies in the Florida Keys Sanctuary, on both coasts, and from detailed molecular studies.” He distributes Florida’s seaweeds into three algal types as follows: 224 green algae, 102 brown algae, and 367 red algae. By my count, that means that Florida’s seaweeds comprise about 14% of the total taxa of these three phyla. Other sources, though, place the number of seaweed species worldwide closer to 10,000, which means that there’s a large discrepancy between Dring’s numbers that Dawes cites (4439 species of algae, of which seaweeds would comprise only a portion) and the numbers Michael Guiry provides on his website. If we follow Guiry, then Florida has about 7% of the seaweed diversity in the world.
Dawes provides a lovely table that breaks things down even further, but I won’t reproduce that here, because I’m not planning to delve into seaweed taxonomy any more than I planned to tackle the protists. As with that kingdom, seaweeds have too many Hard Words. For example:
The basic morphologies of seaweeds include: (1) uniseriate or multiseriate filaments (with one or more rows of cells) that are either unbranched …or branched…; (2) axes of intertwined filaments that are siphonous…or filamentous/hollow in construction…; (3) axes that are solid…or hollow…; and (4) flattened, foliose, or bladelike plants…. Cylindrical or bladed species may have a dense central filamentous core or medulla…, a pseudoparenchymatous core with spherical or cubelike cells…, or [may] be mostly hollow with a few medullary filaments…. Axes can also be parenchymatous, with closely compacted isodiametric cells that lack filaments (5-6).
I don’t know about you, but I doubt that I will ever be able to tell the difference between parenchymatous axes and pseudoparenchymatous ones, so I’ll leave this type of distinction to the specialists. (Dawes and Mathieson do provide a glossary, but it doesn’t help me much: parenchyma means “a three-dimensional tissue of thin-walled isodiametric cells”; isodiametric means “having equal dimensions or diameters.” Make of that what you will; I still haven’t learned how to use the microscope my parents gave me some time ago.)
It’s not just the Hard Words that make seaweed identification difficult. There’s also the fact that “brown algae can appear green and red algae can look green or brown because the plant’s pigments may be affected by nutrient or light conditions.” So before you can even figure out what phylum (botanists would say division here, but since seaweeds are algae, and not necessarily part of Kingdom Plantae, Dawes & Mathieson use phylum too) the seaweed belongs to, you may have to “first examine a part or section of the plant with a dissecting microscope.
Green algae are typically grass green in color (chlorophylls a and b), brown seaweeds olive green or brown, and reds usually rose red to deep purple red” (23). Then you boil it and see whether it changes color (red algae tend to turn green because their pigment is water soluble, while brown algae won’t change color when boiled). Of course, if you place the seaweed in heated isopropyl alcohol, the brown turns green while the red stays red. These are the hands-on methods of science; they are not the same as the methods of the amateur naturalist (at least this amateur naturalist, trained in identification as I am by visual cues only).
So Dawes and Mathieson’s main usefulness to me will lie in the introduction, which tells me about the various nearshore environments of Florida (salt marsh, mangrove forest, seagrass bed, etc.), and in the line drawings on the plates (there are 51 plates, most of which show 15-20 figures), which I will use to try to match up any seaweeds I run across with their taxonomic identities without bringing them back to my nonexistent lab with its dissecting microscope and various apparatuses for hardcore work.
I want to know more about seaweeds because, as D&M put it in the introduction,
Seaweeds play major roles in primary productivity and food chains of marine and estuarine communities, including salt marshes, mangrove forests, and seagrass beds, hard substrata habitats (for example, “live bottoms”), and coral reefs.
So to a certain extent it’s their ecological role, rather than their specific identity, that interests me. But, inasmuch as species identity can sometimes determine ecological role (imagine how differently an animal responds to, say, a tree with thorns and a tree without thorns), understanding how to identify organisms at least to the genus level can be very helpful.
So at least I’ll be able to tell, as I walk down the beach, that yup, that’s sargassum, and nope, that’s sea lettuce (Ulva spp.). I think a field guide to the beach might have more practical application for a nonspecialist…