The Pacific reef tank or Tropical Reef in the Tropics building has similarities to the Atlantic Reef exhibit in Discovery Bay. Both tanks exhibit artificial coral reefs. The difference is in the Oceans they represent. The largest difference is diversity of species. Estimates of 65 to 75 species of coral and 500 to 700 reef associated fish species live in the extended Atlantic/Caribbean coral reef area. This is in contrast to the over 700 coral species and over 3,000 reef associated fish in the Indo-Pacific coral reefs.
The Atlantic Reef or Shark Reef houses predators, large sharks and fish. The Tropical Reef contains sharks and fish also, but these sharks are smaller. The Tropical Reef sharks feed mainly on invertebrates. The Atlantic Reef sharks are suited to eat fish. Both natural reefs, Atlantic and Pacific, have predators to keep populations in balance.
What They Eat
The fish in the Tropical Reef exhibit eat a wide variety of diet items. These fish were chosen because they are omnivores. This means they eat both plants and animals. Algae, shrimp, clams, lobsters, and small fish could all be on their menu if the right size pieces are available. These fish could be called nibblers, small mouths and teeth used to eat small food items. Quickness, stealth, and patience are needed for these feeding habits.
In many ways the sharks in this exhibit are very similar to the fish in feeding habits. As carnivores they will also eat shrimp, crabs, lobsters and fish. They spend a lot of time resting on the bottom, conserving energy. If they smell or see food they “get active” and start searching surfaces for food. Their eyes are on top of their head, mouths on bottom, so they quickly suck up food items when found.
We don’t exhibit fish and shark species in the Pacific Tropical Reef that have large mouths. For example, snappers and groupers would eventually eat anything in this tank that was smaller than them.
Where They Live
Most coral grow in water that is less than 300 ft deep. Roughly 80% of the coral and associated fish and shark species live in water that is less than 150 ft deep. This depth is usually close to land masses. Fish and sharks use a coral reef to escape predators and find food. Pacific coral reefs are found between the Tropic of Cancer and Tropic of Capricorn, roughly 30 deg. North and South of the equator. Going east to west they run from Hawaii to Africa.
What They Do
Corals use light to grow and build the structure that provides habitats for a wide variety of marine creatures. Too much light will cause the symbiotic algae to produce toxic amounts of oxygen. Not enough light starves the symbiotic algae and the corals go hungry.
Water depth, turbidity, and latitude are all factors controlling the range of coral reefs. Low and high water temperatures have different effects on living corals and limit how and where they live.
Rapid environmental changes of any kind are problematic for all coral reefs. Without the support of healthy living coral reefs the associated fish and shark species will not survive.
How They’re Doing
Ocean acidification, ocean warming and associated coral bleaching, increased carbon dioxide in the air, water pollution, sedimentation, destructive fishing practices, coral mining, careless tourism, and ozone depletion are all negative human practices that effect coral reefs.
All of these products of humanity on our planet are making it challenging for coral reefs and the associated aquatic life to survive.
Coral reefs cover less than 1% of the ocean floor but support 25% of all marine life.
They are in trouble around the world. As they decline or are lost so are their many benefits to society. Benefits like animal habitats, millions of jobs for people who depend on healthy reefs, harvested food for humans, protection from storms for the coastlines, and medicines discovered and yet to be discovered.
Scientists’ estimates 11% of the world’s coral reefs have already been lost. 16% were severely damaged by the 1998 El Niño event. Predictions are for another 32% or more may be lost in the next 30 years if human threats are not reduced.
Remoras hitch piggyback rides on sharks and hang on with suctions cup discs on their heads. Remoras keep the shark’s skin free of parasites and in return get to eat bits of leftover food.
A coral colony is like an enormous limestone condominium, getting its bright color from algae tenants. Algae make sugary food for coral from seawater and sun and recycle waste products into oxygen and food.
Coral reefs are like underwater rainforests:
- Both are wondrous, complex ecosystems.
- They shelter the most diverse collection of plants and animals on earth.
- Combined, they house the greatest density of species on the planet.
- Reefs and tropical rain forests both occur in warm climates.
- Creatures that reside in them depend on each other to live.
- People living nearby need them to survive.
- They are being destroyed at phenomenal rates.
- People are their worst enemy.
Corals and sponges are animals. Most earn their names from something they resemble on land.
- Elkhorn coral looks like horns or antlers.
- Brain coral is dome-shaped with irregular surface patterns.
- Table coral looks like you could set it for dinner.
- Tube sponges resemble smoke stacks.
- Chalice sponges are shaped like a short-stemmed wine glass.
Coral reefs are fragile, living ecosystems that are increasingly under pressure due to pollution, disease, and habitat destruction. Not only do they provide habitat for many endangered marine species, but several coral species themselves are now currently listed as threatened or endangered.
Natural threats to coral reefs include hurricanes, typhoons, El Niño, and invasive species. Human threats to corals include destructive fishing practices, coastal development, pollution, and rising global temperatures.
We’ve reached the ocean’s limit. Currently, more than 80% of the world’s fisheries are in danger from overfishing and harmful fishing practices. Since 1950, fisherman have increased their catch by 400% by doubling the number of boats and using more effective fishing gear. Worldwide, fisheries discard 25% of their catch.
Unsustainable fishing practiced like bottom-trawling and some forms of ling-lining deplete targeted species and unintentionally kill sea birds, turtles, and other marine life, while destroying delicate reef ecosystems. About 25 million tons of dead or dying bycatch fish are tossed out each year because they were not the species fishermen wanted. Fish farming methods can sometimes be a more environmentally friendly option. However, some fish farming methods create too much waste and pollute habitats.
To keep the world’s fisheries healthy and viable, global efforts are needed to improve management and decrease political and economic pressures that lead to overfishing. Progress is being made. Several of the world’s largest conservation groups are now focused on addressing the health of marine life and oceans, and managing fisheries sustainably has become a top priority for many government agencies around the world.
Things the Zoo's Done/Doing
Eco-Corps is a grassroots level conservation effort based on the island of Viti Levu in Fiji. The group’s mission is to conserve Fiji’s natural and cultural resources through research, education, and sustainable development programs in local communities. Their four major conservation areas include: marine and terrestrial biodiversity surveys, the development of an underwater park, community education, and wastewater management.
In January 2007, Melanie Sorenson, Education Interpretive Naturalist at the Minnesota Zoo, spent four weeks in Fiji working with Eco-Corps. While there she assisted in the development of a snorkeling trail and a reef walk tour. She also worked with local villagers helping record flora and fauna and developed a training book for local guides and tourists and interpretive graphics, pamphlets, and field sheets for these projects.
The Minnesota Zoo’s Ulysses S. Seal Conservation Grant Program provided Melanie with financial support to cover some of her travel and lodging costs and to purchase supplies for this program.
Minnesota Zoo’s Coral Reef exhibit was designed and constructed with reef conservation in mind. To protect living reef communities, the exhibit was made from artificial corals, either carved or cast from lifelike molds. Reef fishes were collected carefully by hand, and the reef community was not harmed in any way by our methods.