X. Zooplankton and Bioassay

There are two very different perspectives from which we might judge just what papers are "significant" under the title "zooplankton". To the zooplankters themselves I suspect that the limnological/ecological information (X.) is the "significant" information. To many persons who attend this class, however, the information relating to the use of zooplankters in bioassays of toxic substances is more "significant".  I have tried to give you a sampling of both perspectives.

If you could care less about the autecology of some zooplankter, consider that you must know how they fit into the environment in which they evolved in order to establish cultures of relatively normal animals for toxicity tests. This also holds for fish, rats and bacteria. The lack of reliable, repeatable, aquatic toxicity test systems is the direct result of some really dumb (that's Dumb, as in stupid) choices of procedures. The common sense of a child would have, long since, changed these procedures IF those employing them had information concerning the autecology of target organisms. When you read Banta's paper from 1921, note his comments concerning the uncertainties in his culture system, then note that in STANDARD METHODS items which  produced Banta's discomforts have not been eliminated (50+ years of fumbling). There is a legitimate excuse for the weakness of the first attempt in STANDARD METHODS, the person (C. Tarzwell – a fisheries expert!) who wrote it did not want to do so, he just could not find a volunteer and the protocol was demanded of him by a set of bureaucrats. They would have produced one had he not done so!! His excuse, however, does not hold for the next thirty plus years. Quite a few individuals jumped on what they thought was a bandwagon; declared that it was easy to rear "water fleas", and basically plagiarized Dr. Tarzwell's honest contribution. Then, no one was permitted to change his/her mind. That peculiar characteristic of government work often springs from fears that in a court any  admission of uncertainty concerning a toxicity test might be used to ignore all results. I have never seen such an event (judges are as rational as anyone else). I have seen judges discount information when those who provide it do a very poor job, in scientific terms, of justifying the methods they employed to generate that information. Would it surprise you to learn that even folks who become federal judges take science courses - and some of them do quite well! (Apparently considerably better than some who end up doing toxicity testing.)

If you happen to think that animal-based toxicity systems are nasty bad habits, exercised by cruel and unreasonable persons, and you are hooked on what keeps an ecosystem functioning, try this: We humans have introduced some of the strangest mixtures of unnatural and, or, natural materials ever conceived into most of the waters of the world. The zooplankton-based bioassays which are being actively developed, promoted, and promulgated, will probably provide us with a singular source of information which could help us to salvage some of the ecosystems of which we are so fond, and may, MAY, help us salvage enough of the global ecosystem to keep our particular species around for a few more eons. --- Then again, maybe it won't.

U.S.E.P.A. has required a bioassay addition to new and renewal N.P.D.E.S. permits (renewals are every 5 years). Most state D.E.P.'s are trying to comply. The bioassay must include a fish and an invertebrate. The invertebrate is expected to be a mysid (e.g., Mysidopsis bahia) if effluents enter marine or estuarine waters and a daphnid (e.g.; Ceriodaphnia dubia, Daphnia pulex, D. magna) if effluents enter fresh waters. Once both species have been tested, most future testing can be based on the "most sensitive" of the two. That always turns out to be the invertebrate. It has something to do with those guppies your raised when you were 11. The invertebrates are usually quite unhealthy. Thus, they die when slight changes (not necessarily for the worse) occur in their culture/testing environments.

Hutchinson, G. Evelyn. 1961. The paradox of the plankton. The American Naturalist XCV: 137-145. A very special paper. If you read it twice, you may find it is a different paper the second time. What is the paradox? What is the basis for the paradox? Professor Hutchinson once told me that this was a favorite paper. (The paradox relates to the dimensions of that niche which confers “plankton community dominance” on its “occupant”.)

Luckinbill, L. 1978. r and K selection in experimental populations of Escherichia coli. Science 202:1201-1203. Although it is true that bacteria are not "zoo--anything", it is not true that r and K selection are peculiar to bacteria. This strikes me as a very clear communication of the distinctions between the two types of selection. You should be able to distinguish between the two. The original references are included. Maybe someday you might seek them out. What are the relative distinctions between r and K selection? Could you list a few?

Hardy, A.C. 1936. Plankton ecology and the hypothesis of animal exclusion. Proceedings of the Linnean Society of London - III 148:64-70. Note the two distinct causes for patches of zooplankton which have very  little phytoplankton mixed among them.

Crustacea are not the only significant critters in the zooplankton (remember Asplanchna siebaldi?)