Faster than those that do not have zooxanthellae

Figure 3.6

Carbon Pathways in Corals

After Barnes 1980

The zooxanthellae of corals are brown in colour, which is the best colour for absorbing blue light (Benson, 1984). If you have ever been SCUBA diving in a tropical ocean, or seen pictures from these areas, you may have noticed that the water is very blue. This is due to the absorption of the longer wavelengths of light (red and yellow) within the first few metres of water. Therefore it is the blue light that extends furthest into the sea. Zooxanthellae have adapted to make the most use of blue light. The accessory pigments isolated from zooxanthellae such as carotenoids and several xanthophylls, all exhibit peak absorptions between 408 and 475 nm; the blue end of the spectrum ( Jeffrey and Haxo, 1968). Furthermore, chlorophyll c isolated from tridacnid clam zooxanthellae, has been shown to consist of one form, chlorophyll c2, which exhibits peak absorption in the blue end of the spectrum


SSÍ&IÍÍSSssm iîîï'iîïï >ï"i5; í: 5 i í Li^r::Üíiií: > :: y

Organism's Internal Inorganic Carbon Pool


Skeletal Carbonate

Respiratory Metabolic C02

Zooplankton Disolved Organic Matter

Excreted Inorganic Carbon

Excreted Organic Carbon (Mucus)

Seawater HCO3

( Jeffrey and Shibata, 1969). Just as in terrestrial plants, marine algae adapt to decreasing levels of light (such as encountered at greater depths or under overhangs) by increasing the amount of chlorophyll and accessory pigments in their chloroplasts, which further enhances their ability to use blue light (Benson, 1984).

Zooxanthellae use light energy to fixate bicarbonate, a form of carbon dioxide, into carbohydrates through the process of photosynthesis. The carbohydrates released by the zooxanthellae are in the form of glycerol and glucose; fatty acids and the amino acids alanine and leucine are produced also. This process requires certain nutrients, mainly nitrogen and phosphorus. As a source of nitrogen, zooxanthellae use the ammonia produced by the coral (Barnes, 1974; Gordon, 1977). It has been suggested that the nitrogen and phosphorus produced by the coral is a result of the metabolism of the tiny amounts of zooplankton on which the coral feeds (Barnes, 1974; Johannes et al., 1970). However, as mentioned in chapter 2, both ammonium, nitrate and phosphorus (as DIP) are readily absorbed by corals, and they are then used by the zooxanthellae (D'Elia, 1977; Muscatine and D'Elia, 1978). Internal cycling of phosphorus and nitrogen in a variety of compounds also occurs between the zooxanthellae and the coral ( Johannes et al., 1970; Muscatine and Porter, 1977). The carbon used by the zooxanthellae comes mostly from carbon dioxide released by the coral, not from any external food source. Finally, the coral also releases acetate to the zooxanthellae, which utilize it to form fatty acids to help stabilize their chloroplasts (Benson, 1984).

Zooxanthellae can transport up to 98% of their photosynthetic products to the coral. This is assisted by digestive enzymes produced by the coral that act on the cell walls of the algae. These enzymes cause the cell walls of the zooxanthellae to become "leaky'11, allowing them to pass tiieir photosynthetic products to the coral. Amino acids produced by the zooxanthellae are used by the coral to make proteins, fatty acids are used to produce waxes and lipids, while the carbohydrates provide energy for work and tissue growth (Benson, 1984). The importance of zooxanthellae in coral nutrition will be discussed later in this chapter.

One recently described phenomenon in coral/zooxanthellae symbiosis occurs in a Red Sea species of deepwater hard coral, Leptoseris fragilis. This coral contains zooxanthellae, but is most common at depths between 110 -120 m (365-400 ft.); unheard of depths for a photosynthetic coral. At this depth the quality and intensity of light is unsuitable for zooxanthellae. According to

Schlichter and Fricke (1986), L. fragilis contains pigments that alter the wavelength of the light, making it useful for the zooxanthellae.

In summary, using light energy7, zooxanthellae convert carbon dioxide (from bicarbonate taken from seawater and the carbon dioxide produced by cellular respiration of the coral tissue) into carbohydrates (glycerol and glucose), lipids and amino acids. These products are then passed on to the host animal tissue, which subsequently provides a source of nitrogen (ammonia primarily) and phosphate to the algae.

Calcification of Corals

As mentioned earlier, zooxanthellae also assist in the production of coral skeletons. Corals that are deprived of their zooxanthellae, or are kept in the dark, deposit calcium at a much slower rate than normal, and hermatypic corals with their symbionts calcify faster than ahermatypic corals. It is this ability to rapidly deposit calcium carbonate w^hich has helped the corals to become the dominant animal constructors of the reef, allowing them to grow at a rate which can exceed the rate of destruction by biological and mechanical erosion and storms.

Some stony corals do not have symbiotic algae (ahermatypic). These corals are either deep water species or found in caves and grottoes. The most commonly encountered ahermatypic hard coral in the aquarium is the Orange Flower Coral ( Tubastrea spp.). Their location on the reef is not an indication of their intolerance of light, rather it is a result of their inability to compete with faster growing hermatypic species and algae. In locations where the water is very rich in the plankton upon which these corals feed, they may compete with hermatypes and grow on upward reef surfaces.

That light enhances calcification in corals has been known or a long time, but it has only recently been demonstrated through scientific analysis. Chalker (1983) gives an overview of the history of scientific investigation into the calcification of corals. Photosynthesis, not any other biological affect of the light, is directly related to this increased calcification rate.

Exactly how photosynthesis enhances calcification is a subject full of controversy, but it seems that the different hypotheses all relate to the benefits that corals derive by having photosynthetic partners. Some hypotheses about symbiont-linked light enhanced calcification are reviewed by Chalker (1983).

Figure 3.7

Calcification Diagram

After Schuhmacher, 1991

It is believed that algal photosynthesis increases the calcium carbonate deposition by removing carbon dioxide and driving the following reaction to the right:

After: Barnes, 1980 Ca(HC03)2 <--» CaC03 4 + H2C03 H20 + C02

Caicium Calcium Carbonic Water Carbon bicarbonate carbonate acid dioxide

Additionally, the zooxanthellae may remove from the site of calcification phosphate produced as a waste product of metabolism by the coral. Phosphate acts as a crystal poison (Simkiss, 1964), and its removal from the site of calcification could enhance the rate of crystal formation while feeding the zooxanthellae and increasing their metabolism.

In aquariums, the calcification process is inhibited when the amount of calcium bicarbonate in the water is low, or when the pH is too high or too low. See the topics calcium additions, alkalinity, and pH in chapter 8 for further information.

Zooxanthellae Chloroplast Picture






Chitinous matrix !>with primary skeleton


Corals do not merely deposit calcium as a solid mass. The intricate design of their skeletons has a framework composed of an organic matrix of filaments. The calcium, magnesium, and strontium carbonate crystals form on this matrix, which is deposited by the coral. The exact composition of the matrix and the mechanisms of its deposition are not completely understood, and they may vary among different species.

Nutrition in Corals

The nutritional requirements of the various organisms that occur in reef systems are extremely varied and/or difficult to ascertain. We are now no longer dealing only with the different feeding habits of the fish that we are keeping but also various orders of invertebrates, each with their own peculiarities. Add to this mass of confusion the fact that very little is known about the nutritional requirements of these organisms, and one can quickly see that the topic of nutrition in reef systems is a most intimidating one.

The general approach taken in feeding organisms in captivity is to closely study the diets of these organisms in the wild and to duplicate this as much as possible. This approach works quite well with most fish and some invertebrates. However, many fishes' natural diets are almost impossible to duplicate (e.g. those that feed on coral polyps and sponges, or bryozoans for certain fish and nudibranchs). Another problem comes with corals. There are few7 studies published on the diets of corals, and much debate about the amount corals feed or whether corals need to be fed in captivity.

There are various feeding mechanisms used by the inhabitants of our reef aquariums. In some instances the same organism may use more than one feeding strategy, which is probably an adaptation to ensure that as much nutrition as possible can be extracted from the nutrient poor environment of the reef. This is the case with many coral species, and for this reason, we cover coral feeding strategies individually.

Zooxanthellae bearing organisms can use a wide variety of feeding techniques. Not only can they utilize the photosynthetic products of their algal symbionts but they can also feed directly on plankton, bacteria, detritus and fish feces (Sorokin, 1973; Schiller and Herndl, 1989). Some corals even have the ability to directly absorb carbohydrates from the water (Stephens, 1962).

As mentioned previously, most corals contain symbiotic algae in their tissues that can supply some of their nutritive needs. We say

some because the degree to which zooxanthellae contribute to a coral's nutrition has been the subject of much research over the past 40 years. It seems that the amount varies between species. In some species of zoanthids over 90% of their nutrition can be met by the zooxanthellae while in others this figure is much lower (60%) (Steen and Muscatine, 1984). However, the general

Large-polyped hermatypic corals

such as this Turbinaria peitata (left)

benefit from the occasional meal of


shrimp or other small solid food.

jT'- My r

The smaller-polyped Pontes on the

J SW #>

right is more dependent on

photosynthesis, though it will also

feed on smaller particles and

. ■ V ■ ■■ t W j. Ty % -c :■!' ■ ... kv

dissolved organic matter.

J.C. Delbeek,

m ^^ ju. " T ' - . ^^

- J W" ^ "k i ■ --' V^ ^ H ' , " *

■ ■


■ - -i- ■ b

## ..

i" _ .■ i . .fcjfe■ T^^fc 'Jrtf*" f . -" - ■ ~m * rM ; "-v ■ ♦ 4

' . . 7" V * V


HVj.^ ■ ^- \ m t: rt ' ' >- ■"

* rVivff

• .v * 4 'j W 4 -i--:-Li-5:-i---h * ---—

--... ——¿i— --------- . —* -S» . ,_ j -

consensus is that zooplankton do not contribute a major portion of the caloric or carbon requirements of hermatypic corals as the amount of zooplankton available on a coral reef is simply too little to satisfy their energy requirements ( Johannes et al., 1970; Muscatine and Porter, 1977). The amount of plankton generated on a coral reef can be significant, while the imports of plankton from the surrounding sea are small.

Corals can feed in a variety of ways. The large r-polyped forms (e.g. Euphyllia) can actually feed on shrimp-sized prey that they capture with their tentacles. Other corals such as Heliofungia may collect the slime that forms on their large polyps and swallow the microorganisms and detritus trapped in it (Kuhlmann, 1985). Those that feed on detritus either digest the bacteria living on them or the particulate organics that coat such particles (Wotton, 1988). It has even been proposed that some species of coral such as Acropora and Psammocora may actually "farm" bacteria growing among their coral branches. The coral's mucus acts as a carbon and nitrogen source for the bacteria. These bacteria are either directly consumed by the coral, or the nanoplankton that feed on the bacteria are eaten by the coral (Schiller and Herndl, 1989). Still other corals can directly absorb nutrients used by the zooxanthellae (ammonium, nitrate and phosphate, as well as various amino acids) from the water (Franzisket, 1974; Muscatine and Porter, 1977; D Elia, 1977;

Muscatine and D'Elia, 1978).

Although one can certainly feed the larger polyped corals, in our opinion many coral species do not need direct feeding. Many get more than enough from natural sources in the tank. The live rock and associated algae and bacteria produce copious amounts of nutrients, vitamins and other products through their metabolic processes. In addition, worms and microcrustaceans in the live rock produce larvae and gametes that are food sources. Every time you feed your fish, particles of food and dissolved nutrients are added to the water. Wilkens (1990) found that even in the presence of an efficient skimmer the levels of amino acids in the aquarium were many times higher than on the reef. It is safe to assume that many other "nutrients" are just as abundant, despite our best efforts.

Those polyps that are large enough to be fed small pieces of shrimp can be fed once a week or so by directly placing pieces of food on some of the polyps. Zooxanthellae require phosphate, and although they may be able to absorb this from the water, it is generally felt that the main source is from the tiny amount of prey captured by the polyps (Johannes et al., 1970). However, some large polyped soft corals (e.g. Xenia spp.) have never been observed feeding. Lacking stinging cells in their tentacles, Xenia probably absorb nutrients directly from the water. Judging from the large number of successful aquariums that we have seen in which the corals are never directly fed, most zooxanthellae 1 rearing corals do not require direct feeding to survive, grow and multiply. We will provide more information on feeding individual coral species in Chapter 13.

If you do decide to try and feed your corals be very careful about over-feeding i.e. feed SPARINGLY. An occasional feeding of live baby brine shrimp or liquid foods may be appropriate for some specimens but not others. Pay careful attention when feeding, if it looks like the coral is not ingesting any food then perhaps it does not require additional feeding.

When one is dealing with corals that do not contain zooxanthellae (ahermatypic), feeding takes on extreme importance. Examples of such organisms include certain gorgonian species, Dendronephthya spp. soft corals, and Orange Cup Coral (Tubastrea spp.). For these corals live or prepared foods should be given often. Live foods such as baby brine

Ahermatypic soft corals such as the Scleronepthys sp. shown here, require frequent feeding to survive in the aquarium. A. Storace.

The ahermatypic stony coral Tubastreasp. requires frequent feeding. A. Storace.

Zooxanthellae CoralGorgonian Coral

shrimp, daphnia and rotifers are excellent for most gorgonians and Dendronephthya, whereas Tubastrea should be fed larger items such as live adult brine shrimp, small pieces of shrimp, scallop or fish. Prepared foods can te used as well. Dried or freeze-dried foods can be finely ground and soaked in a vitamin preparation. This sludge is then fed directly to the coral through a pipette or baster. Yon should not feed such food by simply placing it into the water. This only results in added pollution as most of it ends up in the filter, in the gravel or under rocks.

The final method of feeding that might occur in reef tanks is through the direct uptake of organic compounds through the body walls of various sponges, marine worms, ascidians (i.e. tunicates), bryozoans, etc. (Sepers, 1977). The mechanisms, importance and role of such feeding in marine ecosystems and our aquariums is not

well understood and certainly bears more extensive research. In conclusion, ecological, biochemical and physiological data indicate that symbiotic algae are of major importance in the nutrition and growth of coral reefs. They are important not only to the reef building corals, but also to other reef dwelling animals such as sea anemones, giant clams and sponges. Symbiosis between animals and algae appears to be a highly successful adaptation for solving nutritional problems in nutrient-poor areas (Gordon, 1977).

As mentioned at the beginning of this section, the topic of nutrition in aquariums is poorly understood at best. This is an area where the experiences of hobbyists can be of value to scientific researchers. There are more hobbyists out there than there are people actively researching this area. It would be a shame if this tremendous pool of information and experience went unused. Share your information with others, write articles for club or national magazines, keep detailed notes on each of your specimens, spread your knowledge and experience.

Depth Zonation of Corals

The diversity and abundance of corals on a reef, their distribution with depth, and the shapes and colours of coral colonies are affected by numerous environmental factors. We offer here a brief summary of the types of factors that may control coral abundance, distribution, colour and shape.


Light is one of the most important physical parameters that controls the distribution, morphology, and colour of corals. For more detail on the importance of light to the coral reefs and to photosynthetic corals and clams, see chapters 1 and 6.

We know that corals of the same species from different depths or zones can have different growth forms (see Falkowski and Dubinsky, 1981), and that light plays an important role in coral morphology. Light also affects coral pigmentation. Corals from shallow, brightly illuminated water manufacture special pigments to absorb UV light (see next section). Corals in deep water are generally darkly pigmented, to absorb more of the available light, while their counterparts in shallow water tend to be paler. Furthermore, the symbiotic zooxanthellae have photoadaptive states, depending on the location of their host and the species of zooxanthellae. In transplant experiments, zooxanthellae in corals from shallow water that are adapted to high intensity light,

function poorly when their host is moved to a deeper, less illuminated environment. Likewise, zooxanthellae adapted to the deep environment are damaged by high intensity light when moved to shallow water (Dustan, 1982). Therefore, different

- |T a species of zooxanthellae may function best within different ranges of light levels. Adaptation by the coral via bleaching or shedding of excess zooxanthellae, or modifications in pigment density, affords some flexibility for location with respect to light. It has been proposed that changes in the lighting (or other parameters such as temperature) beyond the range of flexibility for a particular species of zooxanthellae necessitates that the coral bleach (shed all of its zooxanthellae) and adapt by re-populating its tissues with a different species of zooxanthellae compatible with the new range of light (Buddemeier and Fautin, 1993)- The growth of corals may also be controlled in part by the species of zooxanthellae, and its ability to function optimally with respect to the light field in the location of its host coral.

Figure 3.7

Change in Morphology

In four genera of stony corals from 2 and 20 m.

Growth Forms Corals Female Stony Coral Growth Forms Corals


Growth form in corals is related to calcification rate. In general, the side or portion receiving the most light grows fastest. In shallow-water, the light is not only intense, it comes from many directions because of surface wave refraction and reflection of light off the sandy bottom. Corals in shallow water typically form massive domes or, if they are branched species, they form heads of fingers

or branches. The growth form of these corals shows that they are utilizing light from many directions. In deep water, the light is very directional, mostly from above. When the light is coming uniformly from above, all upward facing surfaces on the coral grow at the same rate. Corals therefore tend to be plate-like in deep water. This phenomenon has also been demonstrated in an experimental aquarium under bright illumination, because of the directional nature of the light ( iaubert and Gattuso, 1989). Corals that normally form thin sheets, crusts, or scrolls (i.e. agariciidae and Turbinaria spp.) only grow rapidly at the outer edge. In deep water they form nearly horizontal, shingle-like plates (an angle off of horizontal may facilitate the removal of settling detritus), while in shallow water they can grow- in vertical plates or scrolls.

Many species show a slight increase in growth rate in a gradient from the surface down to about 5 meters (16 ft.) depth, because of the effects of photo-inhibition by the intense light at the surface (Huston, 1985). In general, however, the coral growth rate within a species decreases with depth (Huston, 1985). Some species do not show this trend, or exhibit just the opposite response.

Factors Other Than Light

Though some corals grow faster in deeper water, other factors may affect their distribution or growth. For example, in transplant experiments, caged colonies of Pocillopora damicornis grew faster at 15 meters (50 ft.) than at 2.4 meters (8 ft.), even though P. damicornis is seldom found at this depth. The cage protected the specimens from coral-eating fish (Huston, 1985).


As we just explained, in deep water, corals may be subject to predation by fishes and invertebrates (i.e. butterflyfish, parrotfish, Crown-of-Thorns starfish, predatory snails, etc.) that may not be able to reach them easily in the most shallow environment because of wave action (Huston, 1985). Therefore certain species that easily fall prey to corallivores may be more abundant in the shallowest water, though they may growr well (or better) under the environmental conditions found in deep water.

Sedimentation and Turbidity

The average turbidity on a given reef as a result of land run-off, tidal currents or wind generated waves affects the distribution of corals and their growth forms. Turbidity blocks the light, and the reduction in intensity affords ideal conditions for growth of both

shallow and deep water species in a mixed zone, in relatively shallow water. Those species that typically occur in the brightest illumination will be restricted to very shallow water in a turbid m environment, whereas they might occur over a broader depth range in clear, sediment free water. Sedimentation can also inhibit the settlement of coral larvae and is a major factor in the prevention of recolonization on disturbed reefs (R. Richmond, pers. comm.).

Growth of Filamentous Algae

Filamentous algae and algal turfs, most abundant in shallow water, can limit the settlement of coral larvae, and thus affect the zonation of species. Herbivores that clear the algae away allow some settlement and counter the effect of rapid algae growth in shallow water, but the reduced growth of algae in deep water makes for better coral larvae survival there. Therefore the rapid growth of algae in shallow water is a factor that tends to increase coral abundance in water deeper than a few meters (Huston, 1985). In areas where the loss of herbivores lias resulted in uncontrolled growth of algae, resident corals may be smothered, and there is a lack of recruitment of new stony corals. This has become a problem in some localities in the Caribbean (e.g. Jamaica) due to the harvest of parrotfish via fish traps, and the sudden loss of most Diadema antillarum sea urchins in the early 1980's, as a result of a mysterious illness. Where this has happened, subsequent damage from hurricanes can eliminate the remaining live corals, and the algae prevent the reef from recovering.

Fast Growing, Over Shading Species

Rapid growing species such as table acroporids create large shade areas below their branches. This shading affords them a competitive advantage in the fight for space and use of light. Therefore they can easily dominate the tops of reefs. Shade-loving species may settle below their "umbrellas" (see coral aggression at the end of this chapter).

Water Motion

The motion of water has a strong influence on both the zonation and shape of corals. The design of coral skeletons makes them either suited or unsuited to the harsh surge and currents found in shallow water fore-reef zones. Some corals adapt to different water flow by altering their shape, but some corals cannot adapt to certain flow regimes (see chapter 1).

Although, it may seem a paradox, one often finds the more delicate, branched forms in the shallows where water motion can be most severe, while in deep, calmer water the more massive and robust forms are common (Vine, 1986). In areas of high water motion, the current can be so great that polyp extension would be inhibited. Therefore, a hydronamic shape that offers high resistance to the water flow7 (i.e. ramose), is an asset, as it dampens the flow enough to allow the polyps to open (Vine 1986). Likewise, less resistive hemispherical shapes are favoured in low-flow environments, since the shape allows better gas exchange across the coral surface (Vine, 1986).


High water temperatures that occur in calm, shallow water near shore, prevent most species of coral from growing there. Cold temperatures in the same environment likewise limit coral growth (see chapters 1 and 8).


Natural disturbances such as hurricanes, if they are frequent and not too severe, tend to increase the diversity of coral species in shallow water because they prevent dominant species from achieving stable growth for too long. Unnatural disturbances, such as oil spills or ship groundings, and severe disturbances, such as powerful hurricanes, can impact coral diversity and abundance on a reef for many years. Chronic disturbance, such as pollution and constant damage from daily visitation by careless divers can also impact coral abundance.

Interactive Competition Between Coral Species

Because of competitive interaction between corals, the presence of a particular species can affect the presence of other, less competitive species in localized zones. Soft corals are especially capable of dominating areas of reef (see coral aggression at the end of this chapter).

Ultraviolet Light and Corals

One of the common misconceptions in the marine reef hobby has been that ultraviolet (UV) light does not significantly penetrate through seawater. In fact, as long ago as 1950 it has been known that UV can penetrate as far as 20 m (66 ft.) in clear seawater ( Jerlov, 1950). Yet, it has only recently been appreciated that UV light can be a significant factor in shaping shallow water coral communities (Chalker et al., 1986).

Ultraviolet light extends below the range of visible light (400-700 nm) and can be divided into three classifications: UV-A, UV-B and UV- C. The wavelength of UV-C extends from 200-280 nanometres and is not considered a factor in marine aquariums since only germicidal lamps produce UV-C (Mohan, 1990). UV-C is also not a factor in nature since light below 286 nm does not penetrate the Earth's atmosphere. In contrast to UV-C, both UV-A (320-400 nm) and UV-B (280-320 nm) penetrate the atmosphere and can be physiologically and photosynthetically damaging to many forms of reef life (Chalker et al., 1986). UV-B has been shown to cause photo-oxidation in corals, to destroy DNA and RNA, and to inhibit the formation of chloroplasts (Halldal, 1968; Mohan, 1990). Under

Acropora sp. from shallow water exhibit UV protection pigments. S.W. Michael.

Stoney Coral

artificial sources of UV-B, corals have shown withdrawal of polyps, discharge of mucus, swelling of tissue, ejection of mesenterial filaments and eventually death (Mohan, 1990). UV-A is somewhat less damaging then UV-B but excessive levels can inhibit calcification in corals and can cause damage to DNA and RNA at shorter (320-350 nm) wavelengths (Mohan, 1990).

It would therefore appear that many shallow water organisms are at risk from exposure to UV light. In most cases, UV sensitive organisms such as algae, sponges and bryozoans exist in shallow areas by growing between coral crevices or underneath overhangs, thereby avoiding direct UV exposure. When such organisms are placed in full sunlight they quickly succumb to UV light but if these same organisms are placed under a UV absorbing shield, they do just fine (Jokiel, 1980). Therefore UV light can be shown to be a major factor in organism distribution on a coral reef. Howrever, there are still many organisms that exist quite well in shallow waters, exposed to large amounts of UV light. These include, stony and soft corals, anemones, giant clams, zoanthids, some sponges and algae (Chalker et al., 1986). Many of these invertebrates contain zooxanthellae, which require light for photosynthesis. Therefore the tissues of these organisms must be transparent to allow for the transmission of light. Jokiel and York (1984) showed that isolated zooxanthellae quickly die when exposed to UV-A and B at levels above 20% of incident surface radiation. It has been shown, however, that oxygen production does occur when zooxanthellae are exposed to UV-A, indicating that it can be used for photosynthesis (Halldal, 1968). Still, corals and clams are quite common in shallow waters, suggesting that they must have some mechanism for protection from UV light. In most cases these organisms have developed UV absorbing compounds in the zooxanthellae and tissue cells. One class of compounds is called S-320, named after its absorption spectrum, which peaks at 320 nm. Currently S-320 is known to consist of three separate mycosporine-like amino acids; mycosporine-Gly, palythine and palythinol (Dunlap and Chalker, 1986). These compounds were originally isolated from the colonial anemone Palythoa tuberculosa and have since been found in sponges, algae, molluscs, echinoderms and tunicates (Dunlap and Chalker, 1986). Other pigments act by absorbing UV light and re-emitting the energy as fluorescence. These pigments are responsible for the bright greens often seen in corals, anemones and clams (Mohan, 1990). Other pigments that result in violet and bright whites, block UV by being good reflectors of UV light (Mohan, 1990)

Jokiel and York (1982) demonstrated that when placed under near-UV absorbing material, the hard coral Pocillopora damicornis grew faster and had lower S-320 levels. This suggests that S-320 concentrations are directly related to UV intensity and that near UV light is an important factor in the growth and physiology of corals. It has also been shown that the concentrations of UV absorbing compounds are lower in organisms found deeper on the reef. Therefore, such organisms are more sensitive to UV light and caution should be exercised when dealing with them in the aquarium. We will go into more detail on UV light and its role in the aquarium in chapters 6 and 10.

Waikiki Aquarium

Release of eggs by a female colony of Sandalolitha robusta in May, 1992, at the Waikiki Aquarium; a nearby male colony released sperm shortly thereafter. The female specimen has been in captivity since 1983. T. Kelly.

Aquarium and Fish Care Tactics

Aquarium and Fish Care Tactics

Who Else Wants To Learn The Secret Tactics For Setting Up And Maintaining A Solid Aquarium Set At Home And Get The Most Exciting Information About Aquarium Fish Care In A Decade. You're about to discover the most comprehensive report on aquarium and fish care you will ever read on the internet in the next five minutes.

Get My Free Ebook


  • lorena
    Where do zooxanthellae reside in coral?
    7 years ago
  • adam wood
    Do deep sea coral and zooxanthellae?
    7 years ago
  • Kade
    Do zooxanthellae use phosphate?
    7 years ago
  • florian
    Do deep water corals grow upward or across?
    6 years ago
  • autumn morrison
    Do zooxanthallae make amino acids?
    6 years ago
  • Peony
    How to make Zooxanthellae?
    6 years ago
  • claire
    Does zooxanthallae need phosphates?
    6 years ago
  • belinda clayhanger
    How to increase zooxanthellae?
    6 years ago
  • Pauli
    Can coral control zooxanthellae?
    6 years ago
  • rudigar
    Which of these organisms would have zooxanthalle growing in its tissues?
    6 years ago
  • semhar
    Do stony coral use zooxanthellae tp get their nutrition?
    5 years ago
  • lucia
    Does any oxygen gas produced by zooxanthellae escape coral tissue?
    5 years ago
  • Jessika
    Which of these organisms would have zooxanthellae growing in its tissues coursehero?
    5 years ago

Post a comment