Continental

Reef Zonation: a cross-sectional map of the natural habitats a marine aquarist can choose to mimic in a captive setting.

imens offered for sale were illegally collected. The same holds true for Australia. Given the growing success of stony coral propagation at the hands of a number of pioneering marine aquarists, it is possible that captive-grown specimens of currently banned Caribbean species will be available. The tons of cultured live rock now being readied for harvest off the Florida shoreline will also harbor small corals that have settled out naturally during the rock-farming process. These corals are expected to be exempt from the usual regulations. In my experience, the shallow-water stony corals found in the waters around Pigeon Key and elsewhere in the Florida Keys grow abundantly under rather adverse conditions of high water temperature and heavy nutrient load. Small specimens brought into aquariums at the University of Tennessee fared well. Finger Coral (Pontes pontes), Yellow Mustard Coral (P. astreoides), Starlet Corals (As-trangia sp.) and Rose Coral (Manicina areolata) were the species we worked with. The first three are found on hard-bottom areas, usually along with Halimeda algae and frequently accompanied by the Upside-down Jellyfish

(Cas slope a). Rose Coral is found on silty or sandy substrates, where its pointed base helps to keep it stable. It is the Caribbean analog of Trac hyp hy Ilia geoffroyi, Open Brain Coral, with respect to its mode of life in the lagoon.

The availability of species from some regions can make setting up accurate biotope tanks more of a challenge, but therein lies the great joy of moving beyond the typical marine aquarium that recklessly mixes species that would never, ever be found within the same sea or hemisphere.

Water Depth

Having settled upon a particular ocean and geographic region that you find appealing, next limit the aquarium further, to a more specific microhabitat within that region. We will discuss in more detail later the various life zones associated with coral reefs, but for now let's consider only one aspect of reef ecology: water depth. Water depth greatly affects the distribution of many types of organisms, largely because of its influence on both the intensity and

Part 1 - Introduction 151

spectral quality of the sunlight that reaches them. Light upright in body form. In deeper water, the same species may intensity decreases with depth. Spectral quality changes be broad and flattened, forming plates that scarcely resem-from broad to narrow, with predominantly blue light pene- ble the shallow-water growth pattern. By altering its growth trating most deeply. Clearly, then, lighting system require- form, the coral is able to present more surface area containments will be different for a tank of shallow-water ing photosynthetic zooxanthellae to collect sunlight, light organisms as opposed to deep-water species. Aquarium intensity having been attenuated by the water column, specimens are collected from depths ranging from a few inches to 60 feet or more, so their light requirements vary greatly. Since most aquariums are 24 inches deep or less,

Reef Zonation organisms with widely varying light requirements will be Within any habitat, there are specific zones where difficult to satisfy within the confines of a single tank. Much particular organisms are most abundant. Bearing in mind of the confusion and controversy surrounding the issue of that one can duplicate only a tiny area, one can focus on a aquarium lighting may simply be the result of attempts to particular zone and try to make it as accurate as possible, keep a wide selection of species under one set of light conditions. The best plan is to select species that occupy roughly similar water depths in nature, then provide the tank with appropriate lighting.

Determining the depth from which a particular specimen was collected may be a challenge, since collectors rarely supply such data. At this time, there is no single source of such information in book form for marine hobbyists. However, many field guides provide a depth range for the specimens they describe, and picture books that depict reef communities may note the depth at which the photograph was made. Such books often provide excellent photos of whole communities of organisms and can give you valuable ideas about how natural reefs actually look. This can be a great help, not only in selecting specimens, but also as a guide to arranging your reef tank decor. There are many such references at your bookseller or library, and more appearing each year. (See Selected Sources, pages 307-308, and Bibliography, page 313.)

A good guess about the relative depth from which a specimen may have come can sometimes be deduced from its appearance. For example, in shallow areas with more Aerial view of a typical reef and shoreline, suggesting many water movement, branching corals may be very bushy and distinctive microhabitats appropriate for a biotope aquarium.

Reef Zonation
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