obbyists interested in reef tanks and live rock certainly hear a lot about coralline algae. Most are aware that this is something good to have in a marine aquarium, but not many know what coralline algae are and how to encourage them to grow.
Classification of the marine algae is a subject for experts, although the corallines form a distinct group. They are red algae (Rhodophyta, Order Cryptonemiales) scientifically identified by certain microscopic details of their reproductive structures. The coralline species, which are Strikingly beautiful, coralline algae also prevent the roa, densely bushy Corallina in distinguished from all other growth of undesirable forms of microalgae on live rock. reef flats and tidepools, and red algae by the production of common, shrublike Jania, a calcified skeleton, constitute the Family Corallinaceae. The body, or thallus, of a coralline species may be crustose, covering rocks like a lichen on a stump, or erect and segmented. The reproductive structures are produced in special cups, called conceptacles. These are sometimes evident to the eye or touch and are a useful clue to the identity of some species. The corallines comprise one of the largest and most important families of the red algae and are found in all seas from pole to pole. They tolerate temperature extremes and are found at great depths, owing to the ability of some species to survive on very low light intensities. While coralline algae are impor
tant components of the flora of cold seas, they can be significant in tropical habitats as well. In Hawaii, for example, the living reef crest is often composed of coralline algae, not coral growth. Ecologists designate this portion of a Hawaiian reef the Porolithon Ridge, named for the dominant genus of coralline algae in this zone of turbulent surf. Lithophyllum is another species found in heavy surf.
In shallow-water habitats, articulated coralline algae may be found. These branching, jointed forms include Amphi-
branches that may be flattened, bushy, or even fuzzy, depending upon the species. In open, more wave-swept habitats, unusual Liagora, only partially calcified and therefore more flexible, is found.
Aquarium keepers are more likely to encounter the encrusting coralline algae. Many can be tentatively identified by noting the color and the pattern of growth. Growing on shells and rubble in shallow water and often seen on the
Chapter Three 99
Coralline algae thrive under aquarium conditions that are conducive to good growth in stony corals, i.e., well-oxygenated water, correct pH and alkalinity, ample calcium, strontium, and iodine. Most encrusting corallines grow under moderate light conditions and will not be found in the brighter areas of the aquarium. Mesophyllum is perhaps the most light-loving species. After initially adding all shells of Astraea snails is Titanoderma prototypum. It looks like a patch of mauve paint. Related Titanoderma and species of Fosliella grow only on the surfaces of green macroalgae such as Dictyosphaerium. (These are not the only corallines that live on other organisms. Some are parasites.) Knobby, pale bluish clumps with sharp projections scattered over the surface are colonies of Neogoniolithon spectabile, which might also be confused with the lavender, rough-surfaced Hydrolithon. Smooth, maroon, distinctly botryoidal encrustations are Sporolithon, found in the intertidal zone to 90 feet and common on live rock. Another common genus is Peyssonnelia, looking like a dark reddish or maroon coat Platelike coralline algae: one of many forms and hues that glass about six weeks after of paint on rocks down to can thrive in aquariums receiving calcium supplementation. the initial introduction of live of the live rock to a new aquarium, the system is likely to experience blooms of microalgae for several weeks. If the aquarium is maintained during this time as if stony corals were already present, the corallines will usually begin to appear in small patches on the
600 feet. Uncommon pinkish purple Tenarea has pretty spiral sculpting on its surface, making it easy to identify. It is most often found on rocks taken from about 30 feet, but sometimes occurs in shallower waters. The genus of coralline algae I see most often established in hobbyist aquariums is Mesophyllum. It is a medium purple, forming lovely shelflike plates and crusts on rocks, decorations, equipment, and glass in old, established reef systems. Careful analysis of the coralline algae growth on live rocks could be used to make a good guess about the approximate depth from which the rock was collected, because the algae's habitat preferences may be rather specific.
rock. This may be taken as a good sign that the system is maturing properly and will soon be a suitable environment for stony corals. The presence of coralline algae on a particular site often inhibits the development of other types of algae in the same spot.
Coralline algae are ubiquitous in the marine environment. In the aquarium, their presence is an indicator of good conditions. Their growth discourages competing algae. They are also colorful, attractive, and easy to obtain on live rock. Like many of the less noticeable species that contribute to the aquarium's biodiversity, coralline algae provide important benefits.
100 Natural Reei Aquariums niques and making their own informal observations. Clearly, however, the use of live sand beds both to maintain a better chemical balance and to provide habitat for beneficial organisms offers both environmental and aesthetic improvements over the bare tank bottoms that were widely advocated only a few years ago.
The other vital biochemical process that occurs in all ecosystems — assimilation — is carried out by pho-tosynthetic organisms. Photosynthesis is essential to many of the species that will be exhibited in a reef aquarium. Some photosynthetic organisms, however, can be a major problem for the aquarist. Photosynthetic organisms utilize light energy to power the reverse of the oxidation process: reduction. During photosynthesis, carbon dioxide (one of the end products of mineralization or decomposition) is "reduced" to carbohydrate molecules in the presence of light. After nightfall, the energy stored in the carbohydrate molecules is liberated once again, using oxygen, in the same metabolic process used by nonphotosynthetic organisms to carry out decomposition. The energy liberated from the carbohydrates is ultimately used by the photosynthesizer to create complex molecules for growth, development, reproduction, and other important biological tasks. When photosynthe-sizers are in turn eaten by animals, or decomposed by bacteria or fungi, the energy stored in their carbohydrates is liberated for the benefit of the consumers. Photosynthesis thus channels the sun's energy into the ecosystem.
The role of bacteria in nitrate utilization is important to the stability of the aquarium ecosystem, but is likely to be quickly overshadowed by photosynthesis when nutrients required for photosynthesis are abundant. Many corals and their relatives, although technically nonphotosynthetic animals, depend upon photosynthesis because they contain symbiotic algae, called zooxanthellae. These have important functions in the life of the coral, one of which is the assimilation of waste products of the coral's metabolism. Much nutrient recycling thus occurs in reef organisms such as these. Probably very little ammonia is actually excreted into the water column by organisms harboring photosynthetic symbionts.Tridacnid clams, for example, are known to extract ammonia and nitrate from aquarium water (Hes-
The bulk of the living material (biomass) of the natural reef aquarium will consist of species that are photosynthetic or that have photosynthetic symbionts. Nonphotosynthetic invertebrates will also be present in significant numbers, as will heterotrophic bacteria. All will release ammonia and other compounds into the water. Owing, however, to their comparatively minuscule food requirements, these organisms will not contribute much to the pollution load in the aquarium. It will most likely be fishes, with their greedy appetites and high levels of activity, that provide most of the waste products for processing by the system. This is one reason why the fish population of the natural reef aquarium should be kept low, although such systems are able to support a population density of fishes per gallon of water that is much higher than the density that occurs in the ocean.
Interest in maintaining large numbers of fishes no doubt led early marine aquarists to focus on the oxidation of ammonia to nitrate as the most important detoxification process that should take place in the aquarium system. To the modern aquarist seeking to maintain a natural reef aquarium, biological filtration (mineralization) must be balanced with its counterparts — assimilation and denitrification. Artificial methods for achieving such a balance in the aquarium usually look good on paper but are impractical because they must necessarily focus on limited aspects of the total ecosystem. Hence, wet/dry filters, for example, are wonderful at achieving mineralization, but a tank so
equipped may experience excessive algae growth if additional effort is not expended to reduce the accumulation of algae nutrients in the water.
In the natural reef aquarium, artificial methods are employed largely to remove organic compounds before they are mineralized. The technique that accomplishes this is foam fractionation, also known as protein skimming. In addition, husbandry practices in the natural reef aquarium are directed toward limiting the input of nutrients from outside the system. Bacteria present in live rock carry out both mineralization (nitrification) and denitrification, thus taking care of any excess material that escapes the protein skimmer. Finally, growth of cer- Colorful but secretive, sometimes troublesome, and covered with stiffened, stinging tain types of algae (usually coralline hairs, bristleworms routinely appear in reef aquariums, imported unseen in live rock, algae species) is allowed to develop naturally, permitting assimilation to occur. In this manner, the natural reef system develops its own balance.
Interactions & Eouilibriums
In any aquarium, however, regardless of the techniques employed to create it, a complex collection of interrelated organisms will develop over time. The biological processes mediated by each of them will affect all of the others. Consider the equilibrium that is achieved in a system that has To select an appropriate suite of techniques for a been running for a year or more with no additions of new particular installation, the marine hobbyist must consider the animals. Apart from the growth of the original specimens, reason for the aquarium's existence. To readers of this book, there may be little change in the biomass. A stable popula-that reason may be the enjoyment of a relaxing hobby, the tion of nitrifying bacteria will convert to nitrate any am-challenge of learning about coral reefs and their inhabitants, monia not collected by photosynthetic organisms. As soon or the pleasure derived from having a special kind of deco- as it is produced, the nitrate is converted to nitrogen by the ration in the living room. Other good reasons for aquari- denitrifying bacteria. When such an equilibrium exists, the ums include creating an artificial ecosystem to study the net amount of nitrogen measurable in the water, whether effects of change on natural ecosystems or the production as ammonia, nitrite, or nitrate, will therefore be zero. This of marine organisms for sale or for restocking the ocean. is a fundamental observation that has been overlooked in
Was this article helpful?
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.