http://reefkeeping.com/issues/2003-12/eb/index.php
Myth #8 in Eric Borneman's article above is especially relevant to this "water change exchange":
Myth 8: The statement, "but my water quality checks out fine."
In his articles here (and elsewhere), as well as in his forum on Reef Central called The Reef Chemistry Forum, Randy Holmes-Farley provides extensive information on the nature of common (and sometimes uncommon) chemicals in reef aquaria. Ron Shimek, and others, have also covered various topics in chemistry and biochemistry over time frames spanning ten years and more. Until relatively recently, only a few chemicals were generally considered in reef aquaria, and the ability to accurately measure those parameters has frequently been called into question.
My point above is that aquarists routinely check a variably complete set of a handful of chemical parameters in variably accurate ways to make the oft-repeated statement, "my water quality checks out fine." As has been discussed elsewhere, there are many difficulties of being assured that such statements are true, and the more recent information concerning more exotic and toxic chemical species including various metals and organometallics virtually ensure that there might be many reasons to suspect that one's water quality might not be "fine," despite routine testing for common parameters.
To take this issue a step further, one must necessarily include the bounty of organic chemicals produced by organisms in aquariums called secondary metabolites. I am both pleased and troubled that the word "allelopathy" has become a regular word in many aquarists' vocabulary. It is almost impossible to describe how varied the products of metabolism can be in the marine environment. In short, virtually every organism in the tank has them, produces them, and releases them. The effects of secondary metabolite chemistry are significant enough to cause real and sometimes dramatic effects in the wild where dilution effects are vast. So common and numerous are these compounds that conferences, books, and journals are devoted entirely to the subject. I would urge readers to look through a copy of the Journal of Natural Products to see the scope of this topic (it is only one of many sources of such information). Each issue consists of several hundred pages (often filled with 1-2 paragraph descriptions) of metabolites derived and isolated from natural sources (organisms) and, sometimes, a brief description of potential effects (usually based on chemical structures similar to those of known function). In any given issue, about 20-50 percent of the chemicals are from marine organisms, and many are from tropical marine organisms. For example, here are the relative feature articles from the past two issues alone:
Novel Oxylipin Metabolites from the Brown Alga Eisenia bicyclis
Isolation and Structure Determination of Lyngbyastatin 3, a Lyngbyastatin 1 Homologue from the Marine Cyanobacterium Lyngbya majuscula. Determination of the Configuration of the 4-Amino-2,2-dimethyl-3-oxopentanoic Acid Unit in Majusculamide C, Dolastatin 12, Lyngbyastatin 1, and Lyngbyastatin 3 from Cyanobacteria
Semiplenamides A-G, Fatty Acid Amides from a Papua New Guinea Collection of the Marine Cyanobacterium Lyngbya semiplena
Komodoquinone A, a Novel Neuritogenic Anthracycline, from Marine Streptomyces sp. KS3
Placidenes C-F, Novel -Pyrone Propionates from the Mediterranean Sacoglossan Placida dendritica
Plakortides M and N, Bioactive Polyketide Endoperoxides from the Caribbean Marine Sponge Plakortis halichondrioides.
New Polyhydroxy Sterols: Proteasome Inhibitors from a Marine Sponge Acanthodendrilla sp.
New Brominated Labdane Diterpenes from the Red Alga Laurencia obtusa
Briaexcavatolides S-V, Four New Briaranes from a Formosan Gorgonian Briareum excavatum
The Synthesis of SO-3, a Conopeptide with High Analgesic Activity Derived from Conus striatus
New Cembrane Diterpenes of the Marine Octocoral Eunicea tourniforti from the Eastern Caribbean
Isolation and Structure Determination of an Antimicrobial Ester from a Marine Sediment-Derived Bacterium
Identification of New Okadaic Acid Derivatives from Laboratory Cultures of Prorocentrum lima
One can imagine what twenty years worth of this type of research has produced. In the feature articles of the past two issues of a single journal, we see novel chemicals derived from sponges, soft corals, dinoflagellates, bacteria, algae, cyanobacteria and mollusks. These are, of course, in addition to those already known from these organisms. Some sponges, algae, and soft corals have been identified that produce in excess of 40 separate chemical compounds.
They are termed "secondary metabolites" because in many cases these compounds do not seem to have a function in basic metabolism. However, many are extremely bioactive, and have diverse effects on other organisms, including being lethal. Of course, the effects are largely unknown and many of these chemicals are not produced to have an effect on organisms that would not ordinarily be encountered by the producer of the compound. Other compounds may have an unintentional effect. Furthermore, various compounds may be very specific in the species they affect, and in how they affect those species. In almost all cases, pairwise tests of one species on another have not been done for any effects. There is little to no information as to what the ultimate fate or reactivity of these organics products might be in any environment, much less in aquaria. Finally, these bioactive compounds are highly concentrated in the closed small water volumes of our aquaria. For some examples of the scope of secondary metabolite chemistry from coral reef organisms, see the boxes below which I have derived from various primary and secondary literature over the years. The listings in the boxes are by no means exhaustive.
I hesitate to make such seemingly alarming statements, for I am concerned that such "unknowns" may become the fuel for more myths. It would be comparatively easy for such information to be used as an excuse on which to blame the death or failure to thrive of various tank inhabitants. However, the fact that virtually every inhabitant in our aquaria is producing variable amounts of novel, uncharacterized, and well-known bioactive secondary metabolites of mostly unknown effects, and may be reactive with a host of other largely unknown organic and inorganic compounds present in our tanks, makes our water a complex soup with no two tanks being alike - or predictable.
The take-home message of this myth is that it is practically not possible to say "my water tests fine." All we can do is recognize certain facts, and act accordingly. In my opinion and experience, the most pragmatic solution is dilution and absorption by the use of water changes, protein skimming, and activated carbon. I fully realize the many issues that might stem from this simple advice, especially in light of the materials provided by authors as mentioned above. However, if nothing else, it seems to potentially simplify the many potential chemical interactions that might be occurring.
Potential: Innocuous to lethal. I believe many inexplicable problems in the survival of aquarium species may be due to secondary metabolites. Some are well known to occur, others are purely speculative. However, there remains the incontrovertible fact that there are effects, and that every reef aquarium has organisms producing a pharmacopoeia of bioactive compounds.
Distribution: Ubiquitous. Every day, aquarists around the world use hobby test kits to measure the levels of perhaps 1-6 variables for which tests are available. There are no tests available for the 4-Amino-2,2-dimethyl-3-oxopentanoic acid unit in Majusculamide C, Dolastatin 12, Lyngbyastatin 1, and Lyngbyastatin 3 from Cyanobacteria that were discovered last month. For all we know, this unit causes 100% mortality in Trachyphyllia geoffroyi. Then again, it might not.
Box 1
Some Typical Reactions Of Marine Invertebrates To Bioactive
Compounds
(Compiled from various sources)
- Tissue hypertrophy
- Mucus
- Increased secretion
- Change in mucosal composition
- Change in mucus secreting cells
- Feeding response initiated
- Polyp withdrawal
- Formation of sweeper tentacles (stony/soft corals, gorgonians)
Marginal tentacles (corallimorphs)
- Formation of acrospheres
- Change in growth pattern
- Change in growth form/direction + or -
- Change in nematocyst composition
- Tissue necrosis - local or general
- Initiation of spawning
- Cessation of gonad development
- Change in metabolism
- Change in behavior (non-sessile invertebrates)
- Increased or decreased susceptibility to disease
- Increased or decreased growth rate and survivability
- Increased or decreased settlement of larvae
- Iincreased or decreased fecundity
- Bleaching
- Mortality
Box 2
Potential Roles of Marine Bioactive Compounds for the Producer
(Compiled from various sources)
- Defense against predation
- Ichthyotoxicity
- Other anti-predation (mollusks, echinoderms, etc.)
- Foul odor
- Bad taste
- Antifouling
- Antibiotic
- Antialgal
- Antifungal
- Antiviral
- Inflammatory/Anti-inflammatory
- Antisettlement (larvae, competitors, etc.)
- Mediator of growth form, growth hormones
- Phototaxis, geotaxis?
- Discharge of nematocysts
- Inter- and Intra-specific communication, chemotaxis
- Immunity
- Admittance, specificity and non-digestion of algal symbionts
- Allelochemcials
- Allelopathy against allogeneics and xenogeneics, b/t and w/in taxa
- Stunting, necrosis, avoidance, mortality
- Immunological responses
-Reproduction
- Planulation
- Mass spawning, spawning release factor?
- Polyp contraction/egg release
- Pheromones
- Surface brooding/mucus sheet formation
- Nocturnal spawning
- Egg buoyancy
- Sperm attractants
- Egg and planulae anti-predation
- Species recognition molecules
