THE ESTUARY
Yes, we could end up like the dinosaurs. Estuaries are areas where freshwater meets saltwater referred to as brackish water. The estuary includes the arm of the sea such as a sound or bay that extends inshore to merge with the river mouth. The St. Simons and Jekyll Island Sounds receive water from several rivers and creeks. Habitats that are part of the estuary may include the salt marsh, mud or tidal flats, sounds, and tidal creeks. These environments include the most biologically productive ecosystems in nature.
Estuaries are rich because they are great absorbers and trap nutrients that flow into them. Rainwater picks up dissolved minerals, chemicals and materials from the land and this material eventually enters the estua ry. Once in the estuary, it is mixed with salt water, carbon dioxide, marsh grasses, algae, phytoplankton and dead and decaying plant and animal matter (detritus) and trapped in the estuary by the ebbing and flooding tides. This constant mixing of nutrients from both the land and the ocean, creates a murky brown mixture of fresh and salt water along with nutrients that makes the estuarine waters so productive.
Plants and animals flourish in the blend of brackish water. But they must adapt to erratic conditions: the effects of tidal currents, changing salinity and the rapid wide ranging change in temperature. Water temperature determines the amount of dissolved oxygen; with warmer water holding less than cold water.
Estuaries are important as the nursery of the sea. Seventy to ninety percent of recreational and commercially valuable fish, shrimp, crabs, and shellfish depend on and live in estuaries for at least part of their life cycle. Estuaries have important commercial and recreational value. They also provide breeding and nesting grounds for coastal birds, reptiles and mammals. Acting like a big sponge, the estuarine salt marsh controls flooding naturally and somewhat filters out pollutants.
The estuarine ecosystems are very susceptible to the impact of human population. Damage to estuaries includes: habitat loss, runoff (from pesticides, oils fertilizers and even paints), and siltation. All of these situations can have a profound impact on the variety of food chains and the web of life. Sadly, many of our world's estuaries are being destroyed. The more we learn and understand the less likely we are to continue destroying the very environment that we are an integral part of. Sustainable development needs to be practiced, especially in this very delicate barrier island ecosytem.
Learn more and be proactive at the grassroots level. Use, reuse and recycle. Use native plants in your landscaping, There are beautiful ways to plant that will attract a wide variety of wildlife.
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Holiday & Everyday Field Studies
Teachers, it's time to register for winter and spring field trips to the Nature Center. Field trips are offered with basic marsh, beach, invertebrate lab and nature art workshops. Special curriculum is designed to enhance core curriculum studies through grades 12.
Church groups, scouts, young adult and elderhostel groups welcome! Overnight groups are welcome too with most staying at Epworth by the Sea where large and small groups can be accommodated including all meals. We also offer special programs for the holidays and spring break.
Call (912)638-0221 or e-mail: coastalkids@www.technonet.com
Visitors are welcome to tour the Center Monday-Saturday 9-5.
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CRITTER CORNER
THE SEA ANEMONE
Is it a plant? Is it an animal? This ocean dweller was a source of confusion for beachcombers as well as scientists up through the last century. They are found in the tropics and at the poles, in water as shallow as tide pools and as deep as seven miles.
It looks like a flower (the word "anemone" comes from the Greek meaning wind-flower). But it is carnivorous and can move about, although at a snails pace. Aristotle concluded that the anemone was a combination of both plant and animal and categorized it as zoophyta, Greek for animal-plant. It was however, finally proven in the eighteenth century that the anemone was in fact an animal, and an invertebrate at that! So why does it have "petals" like a flower? These petals are actually tentacles that surround a large slit like mouth and are equipped with stinging capsules at the tips. Once stung, the anemone's prey, which includes fish, crabs, snails, shrimp, and zooplankton, are paralyzed and then pulled into the mouth and ingested.
These stinging capsules are called nematocysts, and each encases a coiled tube with a toxin-filled barb at the tip. Contact with the tentacle triggers the nematocyst to explode and turn inside out. The coiled tube shoots out and hits the prey, rendering it immobile.
Being equipped with stinging cells places the anemone in the Phylum Cnidaria (the C is silent) along with jellyfish and corals. In addition to feeding, these nematocysts are used for protection as well, with a few species of anemones causing a severe reaction in humans when stung. Most, however, produce a reaction less irritating than a jellyfish.
The tentacles of this invertebrate are attached to a soft tubular-shaped body called a polyp or column. It has no head or appendages and is 99% water. The end opposite the mouth is a closed, flattened foot called a pedal disc. It is used for attachment to rocks or shells, to burrow, and for mobility. The two common anemones one may encounter on our beach are the Hermit Crab Anemone (Calliactis tricolor) and the Sea Onion Anemone (Paranthus rapiformis).
As its name implies, the Hermit Crab Anemone is typically found attached to the shell of a hermit crab, especially the flat-clawed hermit crab who prefers not to venture any further up the beach that the low tide line. The polyp is typically a dull brown color with cream streaks. The tentacles should be retracted if the anemone is out of the water, giving it the appearance of a small striped dome.
The Sea Onion, Onion anemone, or Burrowing Anemone is (you guessed it!) a burrower and is seen quite often in large numbers strewn about the beach after a strong storm. The best way to describe this critter is to think of a freshly peeled, ovoid shaped ( right again!) onion lying on the beach! When it burrows, its polyp can extend into the soft sediments to upwards of 14 inches, taking on a wormlike shape with its tentacles exposed above the sand.
Although the anemone possesses a toxin, our local anemones pose no threat to humans. So the next time you find one of these odd creatures at the water's edge, place it gently into the water and watch for those beautiful tentacles to emerge and wave back and forth. Or, stop by the Nature Center. Our anemones are quite friendly, and if you wave at them, chances are they'll wave right back!
Coastal Encounters is sponsoring another trip to Costa Rica from June 8-June 18 1998. Costa Rica is a small country about the size of West Virginia located at the narrowest point of Central America. It is a quiet country with a surprising number of different environments ranging from lowland tropical rainforests to mountainous cloud forests.
This ten day trip will leave from the Jacksonville airport and arrive in San Jose, the capital of Costa Rica. We will travel by bus to wondrous hiking into the Monteverde Cloud Forest Reserve. We will also be visiting the Butterfly Garden, Serpentarium, Hummingbird Gallery and Orchid Garden over the next few days. On this part of the journey evening programs are offered covering the history of Monteverde, local researchers and bats! For the more adventurous of the group there will be a forest canopy tour, and then on to the lowlands.
The last days of the trip will be spent relaxing on some of the most beautiful beaches in the world. Birding trips, tide pooling, and natural history walks will be offered. Or you can just enjoy the beaches! On the final day at Manuel Antonio we will head back to San Jose for some afternoon shopping.
This trip is being led by Tim Decker, a naturalist. Tim taught biology for seven years before moving to Costa Rica for two years. He worked as a biologist for the Butterfly Garden and as a naturalist and guide for the Monteverde Institute. Georgia Graves, a marine educator will be a guide as well. She was an instructor for two summers as a marine science teacher workshop in the Caribbean, and recently won the Georgia Marine Educator of the Year Award. Georgia now teaches at the Nature Center full-time.
The price for this incredible trip will be around $2000 and will cover airfare from Jacksonville, FL, all lodging, transportation, tours, fees, and most meals. Flights can also be scheduled from the airport in Atlanta. Please call Tim Decker for more information and reservations at (704) 667-0857 or e-mail him at tory@ioa.com
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