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Ocean Life
Coral Reefs
Coral reefs are a precious resource in the ocean because of their beauty and biodiversity. Coral reefs provide shelter for a wide variety of marine life, they provide humans with recreation, they are a valuable source of organisms for potential medicines, they create sand for beaches, and serve as a buffer for shorelines. Coral reefs are built by millions of coral polyps, small colonial animals resembling overturned jellyfish that use excess carbon dioxide in the water from the atmosphere and turn it into limestone.
The Variety of Coral Reefs
Coral reefs can be found in both shallow and deep waters and are classified into 3 categories:
Hard corals
Scleractinia, also called Stony corals, are exclusively marine animals; they are very similar to sea anemones but generate a hard skeleton. They first appeared in the Middle Triassic and replaced tabulate and rugose corals that went extinct at the end of the Permian. Much of the framework of coral reefs is formed by scleractinians. There are two groups of Scleractinia: Colonial corals found in clear, shallow tropical waters; they are the world's primary reef-builders (see below for examples), and solitary corals which are found in all regions of the oceans and do not build reefs. Some live in temperate, polar waters, or below the photic zone down to 6,000 m.
Soft corals
The Alcyonacea, or the soft corals are an order of corals which do not produce calcium carbonate skeletons and so are neither reef-building corals nor do they lay new foundations for future corals. Instead they contain minute, spiney skeletal elements called sclerites. Aside from their scientific utility in species identification, sclerites give these corals some degree of support and give their flesh a spiky, grainy texture that deters predators.
Unlike stony corals, most soft corals thrive in nutrient-rich waters with less light intensity. Almost all utilize zooxanthella as a major energy source. However, most will readily eat any free floating food, such as brine shrimp, out of the water column.
Sea fans
A gorgonian, also known as sea whip or sea fan (soft coral), is an order of sessile colonial cnidarian found throughout the oceans of the world, especially in the tropics and subtropics. Gorgonians are similar to the sea pen, another soft coral. Individual tiny polyps form a colonies that are normally erect, flattened, branching, and reminiscent of a fan. Others may be whiplike, bushy, or even encrusting. A colony can be several feet high and across but only a few inches thick. They may be brightly coloured, often purple, red, or yellow.
In 1999, a deep coral reef 60 m below the surface was discovered by the United States Geological Survey (USGS) Center for Coastal and Wetland Studies near Pulley Ridge, an underwater barrier island west of the Dry Tortugas National Park off the southern coast of Florida. The Pulley Ridge reef absorbs more light by increasing surface area and growing flat rather than the usual vertical growth seen in shallower coral reefs. Other deep water reefs include the Darwin Mounds and the Mingulay reef complex. More is known about shallow water coral reefs in tropical zones than deep-water reefs discovered recently, however much research into these unique ecosystems is being conducted.
Tropical Coral Reefs
Tropical coral reefs are biotic reefs formed in tropical waters by live organisms such as calcareous algae (including red algae) and corals. In contrast, abiotic reefs are formed by the deposit of sand and other materials in shallow water. Organisms responsible for building tropical (biotic) coral reefs can only grow at 20-28°C, so although coral reefs live in all oceans, most are found between the Tropic of Capricorn and the Tropic of Cancer. The best growing habitat for coral reefs is a clear-water photic zone less than 50 m deep where light shines down and microscopic algae can best provide photosynthesis for the corals.
The wide array of coral reef forms includes the Apron reef, the Fringing reef, the Barrier reef, the Patch reef, the Ribbon reef, the Table reef and the Atoll reef. The Apron and Fringe reef both reach down and out from the shore point or peninsula although the Apron reef is typically not as steep as the Fringe reef. Barrier reefs, like the Great Barrier Reef, are separated from the shore by lagoons. An Atoll reef surrounds a lagoon in a circular or uninterrupted fashion and is different from the others because there is no island in the middle.
A Critical Situation
Coral reefs are extremely sensitive to changes in light, temperature (bleaching), overfishing, damaging fishing practices, pollution, and excess sediment from development and erosion. Reefs in Southeast Asia are most at risk of damage due to these factors. Human activity is one of the greatest threats to coral reefs, particularly the destruction of mangrove forests that naturally absorb sediment and nutrients that can suffocate coral reefs with silt and algae blooms.
Cyanide fishing in the Indonesian and Philippine coral reefs of South Asia stuns and injures valuable fish. Although 85% of the world's aquarium fish are captured with this destructive method, they suffer a 90% mortality rate usually several weeks after they have been poisoned by cyanide. Fishermen in developing countries depend on reef fish for income to provide for their families; however, illegal fishing practices and overfishing is depleting fish stocks in these areas, rapidly threatening the livelihood of these local populations. Fishermen hit the coral reefs with crowbars to shake out stunned fish and they also even fish with dynamite, which often destroys every living thing on the reef. Many reefs once teeming with life are now wastelands that even the most vigorous conservation efforts can't begin to restore.
With approximately 85,470 sq km of tropical coral reefs, Indonesia hosts about 33% of the total coral in the world and 25% of all fish species. However, in 2000 it was reported that over 70% of the coral reefs are in bad to fair condition due to fishing practices, out of control tourism, and long periods of bleaching. Coral reefs in the Philippines were found to be 77% less productive from 1966-1986, while the national population doubled in size. If the destruction continues, we will lose about 70% of the world's reefs within 25-40 years.
The effects of El Niño during 1998 and 2004 are an example of the natural factors that influence the growth of coral reefs. During this El Niño, sea temperatures rose and many coral reefs were bleached or obliterated. Coral bleaching occurs when the single-celled algae vital for coral reef survival and known as symbiotic zooxanthellae are rejected from the coral, soft corals, some sponges and even Tridacna clams. The pigment containing organisms are lost as temperature or stress level due to increased light reaches intolerable levels. As temperatures return to normal, some reefs can recover within several weeks or months. However, equilibrium may not be restored due to global warming and the bleaching effect exposes corals to white and black band diseases. There is some evidence that global warming may actually add to the productivity of an ecosystem through an increase in carbon dioxide and higher temperatures, though the validity of this evidence remains to be seen.
Massive coral bleaching occurred in the Great Barrier Reef of Australia between 1998 and 2002 and in reefs in the Indian Ocean, the Maldives, Sri Lanka, Kenya, Tanzania, and the Seychelles. Most areas in the Great Barrier Reef rebounded with little damage but in some areas approximately 90% of the coral has vanished. The reefs in the Indian Ocean suffered the most damage and 90% of the coral reefs were lost in the remaining five locations. In Indonesia, the damage is less extensive but more diversity is lost in an area significantly more difficult to restore.
Conservation and Restoration
Part of the problem with the coral reefs in Indonesia was the move made in 1991 to delocalize power in the Indonesian and Philippine governments. The result was a lack of funding and national support for protection of the South Asian reefs. More recently, conservation efforts have included roping off Marine Protected Areas (MPAs), research and implementation of electrolysis as stimulant for growth, moving reefs to new places and cutting back on harmful fishing practices—all expensive and time consuming endeavors estimated to cost over $100 million dollars. MPAs have been established in regions like Indonesia so that sustainable fisheries can be managed and ecologically important habitats will be protected with a social and biological objective. Laws similar to those found in national parks have been developed to prohibit illegal harvesting of fishes. The hope is that by designating MPAs, coral reefs will be restored, areas will become more beautiful, diversity of life will not be lost and communities will have a sustainable source of income in fishing and tourism. Work is being done to effectively manage MPAs and scientists have found that co-management, the collaboration of local, provincial and national parties, is an effective management strategy. As with many organizations, MPAs will have to overcome challenges that include finding participants, streamlining viewpoints about how effective certain ideas will be and raising enough money to implement change.
Marine Life
Marine life is the essence of MarineBio, so in this section we explore information on the science, biology, taxonomy, morphology, behavior, and ecological relationships of the fascinating marine life that inhabits the ocean.
Marine biology is the study of life in the oceans and other saltwater environments such as estuaries and wetlands. All plant and animal life forms are included from the microscopic picoplankton all the way to the majestic blue whale, the largest creature in the sea—and for that matter in the world.
Marine Invertebrates
Animals that lack backbones are known as invertebrates. Over 98% of species on Earth are invertebrates that rely on other strategies than a backbone for support such as hydrostatic pressure, exoskeletons, shells, and in some, even glass spicules. Some invertebrate phyla have only one species, while others like Arthropoda include more than 83% of all described animal species with over a million species. The most common marine invertebrates are sponges, cnidarians, marine worms, lophophorates, mollusks, arthropods, echinoderms and the hemichordates
Sponges
The anatomy of a typical sponge is organized so that flagella inside the sponge pull water into small holes (ostia) in the body and expel waste through larger holes (oscula). Sponge species have a variety of body plans that provide structure, including support by organic fibers (Class Demospongiae - 90% of sponge species), calcareous spicules (Class Calcarea ~400 species), and siliceous spicules (Class Hexactinellida) or combinations of these. The body plan of a sponge has adapted to filter small food particles from the passing water allowing them to reside in most habitats, including polar shelves and submarine caverns that often contain very few nutrients.
Cnidarians
The Phylum Cnidaria ( (“Ny-DARE-eeya”) consists of about 10,000 species of "simple" animals found only in marine habitats and includes Class Anthozoa ( corals and sea anemones), Class Hydrozoa ( hydrozoans), Subphylum Medusozoa: Class Cubozoa ( box jellyfish), Class Scyphozoa ( jellyfish), and Class Staurozoa which contains Order Stauromedusae ( stalked jellyfish). Phylum Cnidaria may also contain Family Polypodiidae and Family Tetraplatidae. Species in cnidaria have special stinging cells called cnidocytes (see figure). Cnidarians evolved during the Precambrian era and are some of the earliest multicellualr life forms known. Most cnidarians have a very basic body plan which includes a digestive cavity with one opening. This opening functions as both the mouth and anus for the organism. The only true organs in cnidarians are the gonads. Most cnidarians are symmetrical, an observation referred to as “ radial symmetry.” Cnidarians also have an ectoderm (tissue that covers the outer body surfaces) and an endoderm (inner layer of cells forming the gastrointestinal and respiratory tracts, and inner organs). The ectoderm is connected to the endoderm by a gel-like substance known as the mesoglea. Cnidarians use a nerve net and very basic receptors for impulses to move. Oxygen is taken in directly from the water through the tissues.
Marine Worms
Marine worms can be placed into more than ten different phyla and come in a variety of colors, shapes, and sizes. Marine worms are often confused with other animals with thin and long bodies. Most marine worms are grouped into the Annelids, a group that includes the Polychaetes (bristle worms), Oligochaetes, Hirudinae, and the Eunice aphroditois. Polychaetes are most often found near the shoreline and swim or crawl using a pair of legs found on each segment of their body. The Oligochaetes, which include earthworms, are mainly found on land and the subclass Hirudinae include leeches that usually live in freshwater environments. Some marine worm species, such as the bearded fire worm, can deliver a nasty burning sting to humans when handled.
Lophophorates
Lophophorates are characterized by a special feeding organ called a lophophore which is an extension of the body wall into a tentacled structure that surrounds the mouth and is either U-shaped or circular. The lophophore is used to trap floating food particles in passing currents (called suspension feeding). Tentacles surrounding the mouth are usually hollow and the mouth is usually located inside the lophophore. The anus is on the same side of the body but on the outside of the lophophore. Lophophorates include the phyla Phoronida, Bryozoa (Ectoprocta), and Brachiopoda and are related to the Mollusca and Annelida phyla. Many lophophorates have tubes, shells, or exoskeletons for protection. They are usually sessile (non-moving), benthic (sea floor dwellers), and live in salt water, although there are a few freshwater lophophorates in the Phylum Bryozoa.
Mollusks
Animals classified under the phylum Mollusca are extremely diverse in form, but all have a fairly simple body plan. Familiar mollusks include oysters, chitons, clams, snails, slugs, octopus, and squid. Most mollusks have a soft body and a hard or “calcareous” shell. Many mollusca use mucous and cilia to eat, move, and reproduce. There are more than 110,000 species in phylum Mollusca, more than every other phylum except Arthropoda. With a few exceptions, all living species of mollusks are categorized underGastropoda or Bivalvia. Another important class is Cephalopoda. Some scientists have determined that there is more biomass from marine mollusks than any other animal on earth.
Arthropods
Crab from teh Bunaken Marine Park, Suluwesi, Indonesia 2006Krill, Euphausia superbaArthropoda is the largest phylum in the taxonomic system and is composed of insects, crustaceans, and arachnids. Nearly 4/5 of all living animals are arthropods.This ancient phylum dates back to the earliest days of the Cambrian period. Arthropods are characterized by a segmented body plan with a head, abdomen, and thorax and legs or appendages on every segment with a rigid exoskeleton made out of chitin. Arthropods use their appendages to feed, as sensory mechanisms, and for locomotion. Aquatic arthropods use gills for respiration. Although spiders are possibly the most familiar arthropod, lobsters, crabs, barnacles, and shrimp in the class Crustacea are also in this phylum. Arthropods are most closely related to the Annelida, or segmented worms. The five main subgroups of the phylum are the Trilobita, Myriapoda, Chelicerata, Crustacea, and the Hexapoda.
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