By Robert Day, Phd candidate and graduate teaching associate at the Ohio State University, Department of Zoology, Columbus, Ohio. 43210
One of the most important undergraduate classes for fledgling Zoologists at Ohio State is "Introduction to Zoology" or "tip-toeing through the taxa" as it's known to the faculty. It's a tough, boot-camp of a class that really sorts the sheep from the goats (the tangs from the sea cucumbers if you prefer marine metaphors.) In nine frantic weeks we lead (or drag) students through 13 phyla and hundreds of representative species.
In recent years, the teaching staff have tried to incorporate more live specimens into the class because we found that students become excited and enthusiastic about visual aids that slither, creep or wiggle across their desk. In contrast, it seems they quickly loose interest in anything stuffed, pickled or nailed to the base of a sealed glass box . Because of the global environmental situation, we also felt a duty to promote respect for living things and the value of biological diversity, without compromising student contact with real animals or increasing class running costs.
This seems like a formidable list of demands, but many of them have been met using a carefully managed three tank, 220 gallon, marine aquarium system that I thought might interest SeaScope readers, especially those involved in science education.
Our system is unlike most hobbyist tanks because its purpose is quite different. We avoid large expensive specimens and ignore mainstream ideas of what is, or is not "desirable". Instead we use cheap, (better yet, free) hardy species that can stand frequent removal and examination. We favour anything that will breed explosively and colonize rapidly. Tiny species are welcome; they help improve student microscopy skills. Drab, cryptic species are also fine; they teach students to be observant and identify species by looking for key taxonomic features. Bristle and spaghetti worms, Aiptasia , isopods, amphipods and all the other so-called "undesirable" organisms are ideal. They demonstrate the biology of their taxa perfectly well and our system contains nothing expensive for them to exclude anyway. Widespread predation? That's fine too; we use it to show ecological relationships between organisms. Lush algal growth ? Great ! It increases the number of microhabitats and thus contributes to invertebrate and protist diversity, as well as reducing nitrate levels.
The city water in our area seems to be blessed by the angel of death, so we use only distilled. Since supply is limited, even small water changes are a rare luxury. We add generous dosses of commercial and home-made, iodine-rich trace elements and believe it or not, we also add nitrates and phosphates to the system (I can hear you all cringing !) This prevents reproductive disintegration of our macroalgae and maintains modest microalgae growth, although when we test for nitrates we rarely find any. (Now who's crazy ?) The way some aquarists rant and rave about the "evils" of microalgae, an outsider might believe it to be some form of radioactive toxin. In fact, it's a perfectly natural part of any coastal environment. If you peer into the shallow water of the Florida Keys shoreline you'll often see dense stands of it teeming with marine animals. One potential problem with lush algal growth in a closed marine aquaria is the yellowing of water by algal pigments, but we've found that this can be easily prevented using ozone. To prevent algae from over-growing the entire system we occasionally harvest a few handfuls, part of which is used for research elsewhere, the rest we puree into an "algal slurpee" and return to the tank.
In many ways our system resembles the highly diverse ecology of the Keys' shoreline and quiet residential canals. I never describe it as a "reef tank" since it contains no coral and few large cnidarians. The same water circulates around all three tanks, but by varying conditions in each (light levels, turbulence and predator distribution) we've been able to generate ecological partitioning such that each tank holds slightly different species and the total biological diversity is higher than in a single tank of equivalent volume. Of course, this sort of highly productive, high diversity system could also be established in a single tank.
Every one of the 13 main phyla we cover in class is represented in our tanks, which we estimate house a little in excess of 100 animal species, perhaps 3 times that if we include the microscopic algae and protists. Most of these came in as "piggy back" colonists on Floridean algae collected as part of my graduate research ("The Cell Biology of the Caulerpales") and therefore didn't cost us anything. Others were donated by local aquarists or by the Columbus Zoo Aquarium, with whom we enjoy a wonderful symbiosis.
The system is environmentally friendly since it includes only tank-raised fish, and anything we show our students is returned to its home alive so that it can be observed again and again. This approach saves money and shows the students that a responsible scientist can study life without depleting it.
Some of our students have lived in Ohio all their lives and have never seen the ocean, hence the range of different facial expressions on their first encounter with (say) a pencil-urchin has to be seen to be believed:
student: " Does it bite?"
prof : " No, here, hold one"
student: " Aren't they poisonous ?"
prof: " No, it's quite safe, go on"
student: " It's not real, right ? It's just a golf ball that you glued
some sticks onto."
prof: " No, it's real, see? it's moving. Go on, hold it !"
student: " OOOOOOOOH!"
This type of marine aquarium is certainly not for everyone. Some more traditional aquarists may even find our systems ugly (all that algae, swarms of amphipods and isopods and literally thousands of small polychaetes). Beauty however, is in the eye of the beholder. Our system is easy to maintain, extraordinarily cheap to run and spectacularly diverse. If you're a hobbyist fascinated by small animal diversity and have access to an initial source of marine algae this can be a cheap and easy alternative to the "reef" tank. If you are a science educator, I heartily recommend this cost effective tool that gets the students to class early, keeps them late and introduces them to biological principles in a way that text books and preserved specimens alone can't match.
