The Aquatic Environment
Part I
By Jason Kim
Jason is the founder of AquaC. Inc.
From his web site www.proteinskimmer.com
Aquarticles
A lot of people who become interested in reef keeping have little or no background
knowledge about the marine environment. Often times, beginning hobbyists are those
individuals who feel ready to make the transition from freshwater to saltwater aquariums.
Although some of the basic principles which apply to a freshwater system remain, reef
microcosms are often more complex due to the fact that they are really miniature replicas
of the actual ocean environment.
So what is a reef, anyway??
Biologists define a traditional coral reef as a large, stable framework which is biogenic
in origin, limited to the photic zone, and resistant to wave and storm action. Did you
know that the Great Barrier Reef in Australia is the single largest organic construction
on the planet? These tiny animals are really quite amazing. Because coral polyps are so
small and slow-growing, it takes thousands, if not millions of years to build a large
reef. Over time, the calcareous remains of coral skeletons, molluscs, bryazoans, and other
marine critters are slowly cemented together by coralline algae and geological processes.
Coral reefs are limited to the photic zone (the warm, sunlit bathed belt around the
Earth's equator) since hermatypic invertebrates rely on U.V. light to synthesize food. One
of the hallmarks of a pristine reef is the crystal-clear, nutrient-poor water which
surrounds it. Just like the expensive condominiums in Hawaii, real estate in tropical
oceans is hard to come by and extremely valuable. The only way slow growing corals can
compete with the faster colonizing species of algae and sponge is by living in an
environment which is inhospitable to nutrient-loving organisms. Most algae require lots of
nutrients like nitrates and phosphates in order to thrive, and these delicacies are often
in short supply off the shores of a tropical island. Corals, on the other hand, subsist
quite well on the simple sugars their symbiotic zooxanthellae provide via photosynthesis.
Not only are tropical waters nutrient-poor, but they also tend to be clear of sediment,
terrestrial run-off, and phytoplankton blooms. Sunlight already has a tough enough time
penetrating water - in fact as much as 75% of useful U.V. light is absorbed in the first
few feet of the ocean's surface. Unclear water only makes it harder for corals to harness
the sunlight they so desperately need.
The take-home message here is really quite simple. A successful reef
aquarium absolutely requires clear, clean, nutrient-poor water in order to thrive. The
principles which apply in the ocean are just as applicable to the tank in your living
room. If your aquarium's water is laden with excess nutrients, unwanted algae may begin to
take over your tank and eventually crowd out your expensive coral specimens. Of course,
there are some species of algae which are slow growing and actually very attractive, and
thus suitable for the home aquarium. Most of these species belong to a group of marine
plants called coralline algae. Coralline algae incorporate calcium in their tissue layers
as a means of defense against herbivorous fish. Since they rely so heavily on calcium,
these types of algae are often slow growing and do not pose a significant threat to
captive coral specimens. Other types of algae, however, like the dreaded "hair
algae" or "bubble algae" can become the bane of even the most experienced
aquarist. Nutrient-rich water not only affects algae growth, but there is quite a bit of
evidence that suggests it also inhibits coral health and can even lead to premature death.
Small polyped stony corals such as members of the large Acropora genus are
notoriously delicate and require near-perfect water conditions in order to thrive. Through
proper techniques and husbandry, an oligotrophic (nutrient-poor) environment can be
maintained.
Those are topics for future articles, however... Look forward to next week's issue,
which will be part two of this three part series on the aquatic environment.
The Aquatic Environment
Part II
In last week's article, I stressed the need for superb water quality. Some of you may
have wondered why many tropical areas are oligotrophic (nutrient-poor) by nature, since
temperate parts of the world seem to be heavily inundated with an abundance of nutrients.
One of the main reasons is due to the fact that nutrient-rich water, after a long journey
through the deep sea, is constantly imported by offshore currents along the coasts of many
temperate areas. Most of the world's temperate coastlines are directly affected by
upwelling currents, and this is one of the reasons that kelp/macroalgae habitats are
common in these areas. Tropical coral reefs export rather than import nutrients through
strong wave action and currents. Furthermore, the biological interactions which exist on
coral reefs are so tightly interwoven that most nutrients freed through biological
processes are simply sucked right back up into the system and recycled. Just like the real
estate on a calcareous reef, nutrients are hard to come by and are plucked up as if they
were hotcakes. Besides having crystal-clear water, tropical reefs are also remarkably
"sunny" places. Unlike Northern England or Seattle, Washington, the tropics
receive near constant bombardment by the sun's intense U.V. rays. The tropics experience
fewer cloudy or overcast days per year than do other latitudes, and they also receive a
greater amount of sunlight. The angle of incidence effects light's ability to penetrate
the atmosphere and ocean surface. If you hold a flashlight at an angle and stare into the
bulb, your eyes would probably be just fine. But if you look straight into a flashlight
head on, you might be temporarily blinded. This is a good example of light's angle of
incidence and how it affects intensity.
Since corals depend so heavily on light in order to survive, and we know that light
rays are amazingly strong at the equator, it makes sense that we must strive to create a
very bright environment in the aquarium. The term brightness, however, means very little
to the experienced reef aquarist. Light, just like sound, varies in wavelength, as well as
intensity. Certainly, there is a huge difference between one of Beethoven's symphonies and
the sharp sting of an air horn. Imagine that corals, in the same way that people can
tolerate certain frequencies of sound, enjoy certain wavelengths of light and dislike
others. Since water serves as a very good filter for most of the visible light in the
spectrum, corals have, over time, evolved and adapted to specific "colors" of
light. These wavelengths happen to be those which penetrate water the most effectively.
When you are underwater, everything seems to look blue, green and grey. Notice how reds
and yellows become drab the deeper you go. Since blues and greens, or wavelengths near
400-450 nanometers penetrate the ocean so well, corals absolutely depend on this band of
energy to survive. This is of great importance to the reef aquarist, since many of the
bulbs offered for sale at pet stores produce high intensity red and yellow light, and
little blue light. The reason manufacturers produce these bulbs is simple. Corals, fish,
and decorations look their best under red/yellow light since this wavelength seems to
bring out their vibrant colors best. When purchasing lights for a reef tank, however, it
is wise to pick bulbs which most closely match the wavelengths which are found in the
natural environment. Do not buy bulbs which only make your critters look vibrant. Sure,
you may get a few oohs and ahhs, but they will be temporary gasps of amazement since your
tank's inhabitants will soon be dead. Luckily, the recent boom in the reef keeping hobby
has brought about an awareness of this issue, and it's quite easy to find the perfect
lighting system.
I would like to mention one other matter before I end this article. Now that we have
covered the basics of light and water quality, some people might wonder what other aspects
of the aquatic environment remain to be discussed. One issue that frequently gets left out
of many popular texts is the bioload factor. For those familiar with fish-only aquariums,
there is an old rule of thumb which states "one inch of fish per gallon of
water". How does this rule apply to reef tanks?
First of all, there are very, very few "rules" in the reef keeping hobby at
all, and anyone who tells you otherwise should be looked at with great skepticism.
Even in regards to fish-only tanks, this rule of thumb is silly. Why? Different species
of fish produce varying amounts of biological waste. For example, a six inch triggerfish
which feeds on raw meat and goldfish will certainly present a greater stress on a
filtration system than would a six-inch pipefish. Some people recommend calculating actual
body mass as a way to decide how many fish an aquarium can handle. This, in my opinion, is
just as silly. A large angel fish with the same body mass as a triggerfish just doesn't
produce the same amount of waste. Triggers are messy fish, whereas angels tend to be
delicate, nit-picky eaters. Furthermore, a tank with a wet/dry filter, protein skimmer,
mechanical canister filter, U.V. sterilizer, and ozonizer will certainly be able to
process a heavier bioload that one which only benefits from a single wet/dry filter. Once
again, the old trustee "rule of thumb" falls apart.
Corals, like fish, come in all sorts of shapes and sizes, and also vary in their
capacity to produce waste. If you've ever seen a picture of a coral reef, or had the
privilege of diving one, you undoubtedly noticed that most sections of living reefs do not
look like the pictures of beautiful aquariums you see in magazines and books. For the most
part, corals simply cannot coexist in such tight orderly fashion with one another.
Remember, it's a dog eat dog competition for space and resources out there. This is not to
say that a tank jam-packed with corals is an unhealthy tank...it is merely a word of
caution. I once read an article which stated that the average two-inch damsel fish, in
nature, has the equivalent of 2,000 gallons of water in which to live. It would be mighty
depressing if we were forced to purchase huge, ten foot long tanks in order to keep a lone
damsel. The point is that many ocean creatures are accustomed to a large amount of space
to move about in and live. Corals, though sedentary, need space too. Many species of
corals have evolved specialized defense mechanisms to ward off would-be intruders. These
include stinging, nematocyst-lined sweeper tentacles and various methods of chemical
warfare. Since we should attempt to duplicate nature in the home aquarium, it is
appropriate to keep these factors in mind. Beware of placing corals too close together.
Some specimens, such as certain species of soft corals that produce harmful biotoxins,
should also be watched closely. As long are your aquarium's inhabitants live peacefully
and appear healthy, then there really is no limit to the number of animals you may stock
your tank with. Do not, however, purchase a thoughtless assortment of animals, place them
in your tank haphazardly, and hope for the best. This would be cruel and pointless, since
your animals would undoubtedly harm themselves, and might even die.
Next week will be part three of this series on the aquatic environment.
The Aquatic Environment Part III
Ahh...we have finally reached the last article of this series. Hopefully, those
of you who are taking the time to read these articles are actually learning new
information and gaining new insight into the biological processes which help make coral
reefs some of the most fascinating places on Earth. So far, I've talked about water
quality, the importance of light, and factors concerning bioload. The last topic I want to
discuss is the state of the world's reefs. While this topic does not directly deal with
aquarium techniques, I think it is important for all prospective reefkeepers to have an
idea of what's going on below the ocean's surface.
There are hundreds of different types of habitats here on Earth. People tend to be most
familiar with terrestrial ecosystems, since these areas often benefit from the most
popular spokesmen. I am not talking about Jack Hannah or some environmentalist from
Greenpeace... I am referring to those cute, furry animals that inspire compassion for
nature. Tigers, koala bears, and their assorted cuddly friends contribute a great service
to ecologists who fight to save their habitats. Unfortunately, ecosystems like salt
marshes, deserts, and the open ocean do not have many spokesmen to speak of (no pun
intended). Everyone knows that the world's rainforests are being slashed and burned at a
mind-boggling rate, but did you know that coral reefs are taking just as bad a beating?
Agricultural runoff, blasting, cyanide use, and over-fishing are just a few of the
problems which threaten reefs today.
I doubt that the International Coral Reef Conservation Association would attract much
public support by putting a longhorn cowfish on its brochure. What a shame! Corals (or
their close relatives) have, for the most part, inhabited the earth's tropical ocean's for
over a billion years. That is a very long time, even geologically speaking. Coral reefs
have witnesses the birth and extinction of dinosaurs, and will likely persist to witness
the last days of Homo sapiens. One of the reasons they have been so successful is the fact
that reefs, as an ecosystem, are remarkably adaptable. Unfortunately, human beings have
used this fact as a way to justify their grossly exploitative actions. The progressive,
blitzkrieg-style impact on reefs due to anthropogenic influences, combined with natural
phenomena like storms, temperature variations, and disease are really taking their toll
throughout the world's tropical oceans.
Quite a few experts in the field agree that the pristine reef environment is a thing of
the past. A habitat gone extinct.
What can we do to help save the world's reefs? Unfortunately, not a whole lot. Even
with increased legislation and awareness of key environmental issues, the state of the
oceans hangs perilously from the sloped shoulders of mankind. As the world's population
continues to explode, the oceans will be forced to accept greater and greater stresses.
There are many ill-informed conservationists who would have the public believe that the
aquarium industry is one of the greatest threats to coral reefs. This saddens me,
since I feel that their energy could be better spent trying to tackle more serious issues
at hand. Until recently, caring for live tropical invertebrates was something straight out
of a science fiction novel. We simply did not understand the biology or possess the
technology to keep such delicate creatures alive in the home. As a result, corals have the
reputation as a wasted resource in the aquarium. Conservationists can easily target
aquarists since they are not backed by the enormous funds which oil companies, foreign
fishing conglomerates, or organizations representing farmer's agricultural rights use to
fight their economic and political battles.
The fact is, the harmful effects of harvesting for the aquarium trade is low on the
list of environmental threats.
Unlike other pressures, the industry does increase awareness and promote education
which might ultimately lead to increased conservation efforts. I believe that one of the
most promising ways to preserve natural coral reefs is through education. As the
reefkeeping hobby continues to gain popularity the general public will learn what amazing
creatures these are and hopefully want to help save them. The manatees in Florida or the
California condor would have gone extinct long ago had their plights not been made so
visual to the entire world. Large public aquariums are sprouting up like weeds in many
parts of the country, which goes to show that increased awareness and education is now
within our reach. As responsible reefkeepers, and in order to help fight to save the
world's reefs, we should avoid purchasing specimens which are obviously unfit for life in
an aquarium. There are plenty of species of coral, fish and invertebrate which can live
comfortably in a captive tank.
Let's not add fuel to the fire by attempting to maintain those certain
"delicate" species which have little chance to survive.
If we act responsibly, there just might be the slightest glimmer of hope for the future
of our Earth's most prestigious aquatic environment. Take pride in the fact that, as you
acquire knowledge and gain the experience necessary to become a successful reefkeeper, you
are also a full-fledged conservationist, playing an ethical role in the grand scheme of
things.
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