Hydrothermal Vent

Habitats: Hydrothermal Vent - Characteristics

Hydrothermal Vent

ALVIN, an ONR-research submersible (a small submarine) operated by Woods Hole Oceanographic Institute, made an amazing discover in 1977. While diving nearly 8,000 feet (2,400 meters) on the East Pacific Rise near the Pacific Ocean's Galapagos Islands, the submersible and its three passengers happened upon a hydrothermal vent, the first ever seen by humans! Completely isolated from the world of light, whole communities of organisms (creatures) live in places where warm water flows from chimneys in the ocean floor. These vents are found in some of the deepest places in the ocean, far beyond the reach of normal submarines or divers.

Hydrothermal vents are formed where two oceanic plates pull apart and erupting lava replaces the sea floor.





In these areas, extremely hot, mineral-rich fluid flows out from underneath the ocean floor's surface. The hot fluid flows into very cold water, usually 2 C, and cools down quickly. The cooled minerals in the fluid settle around the vent opening creating chimney-like formations. Some chimneys have been known to grow as tall as 6 kilometers!



Cold seeps are areas similar to hydrothermal vents. Though the cold seep waters are about the same temperature as the surrounding waters, they are called cold seeps in contrast to the extremely hot fluids from hydrothermal vents. The cold seeps support organisms similar to the hydrothermal vents though the exact make-up of the biological community surrounding them depends on the chemicals, such as hydrogen sulfide, methane, iron, manganese and silica, found in the cold-seep fluid.

Habitats: Hydrothermal Vent - Characteristics

Tubeworms in the Pacific Ocean (courtesy of NURP) Although hydrothermal vents are what we would consider a harsh environment, they are teeming (abundant) with life. As long as the vents remain active, which is usually one to two years, animals thrive there. In fact, more than 300 species live around the vents and are unique to this type of environment. These creatures, including tubeworms, fish, crabs, shrimp, clams, anemones and chemosynthetic bacteria, have learned to survive the complete darkness, the extremely hot vent water and the tremendous water pressure. Mussels, worms and spider crabs in a seep community of the Gulf of Mexico. (courtesy of NURP) At such depths, sunlight is unable to penetrate and allow plants to photosynthesize. Thus, they cannot be the basis of the food chain as they are for us and for every other creature with which we normally come in contact. Animals at these depths depend on bacteria that are able to convert sulfur found in the vent's fluids into energy through chemosynthesis. Larger animals then eat the chemosynthetic bacteria or eat the animals that eat the bacteria. In other vent creatures, the chemosynthetic bacteria live inside their bodies. Some organisms, such as the tubeworms, that live around the vents do not have a mouth or even a digestive tract as we do. The bacteria actually live inside their bodies and provide nutrients directly to the organisms' tissues. Habitats: Hydrothermal Vent - Humans & the Environment If hydrothermal vents were closer to the surface, mining copper, manganese, and even gold from them could be quite profitable, but they are far too deep in the ocean for this to be profitable. Even if it were, such activities would destroy this unique habitat. Bacteria discovered around these vents has already begun helping break down dangerous hydrogen sulfide waste from industrial processes, and treatment with sulfer-eating microbes is allowing gold to be extracted from some rocks more easily. Some scientists have suggested that life actually began millions of years ago around hydrothermal vents. These hydrothermal vent fields exist far from the normal activities of humans, in areas so difficult to get to that the vents were completely unknown until 1977. At the present time only a handful of extremely expensive exploration submarines can even reach them. Even with all of the valuable metals that can be found around these vents, it is still too expensive to make mining them worthwhile.

Estuaries - Estuary Life

Habitats: Estuaries - Estuary Life

Estuaries are home to an astonishing variety of plants and animals and important in the lifecycles of many more. Crabs and clams of many species call these fresh and saltwater mixing zones home, each finding the salinity (saltiness) that suits them best.

Horseshoe Crab

Filter feeders are found in all parts of the estuary. They are creatures that pull small bits of organic material, like plankton and larvae, from the water as it moves past them. Horseshoe crabs are one of the older inhabitants of coastal estuaries, living happily and largely unchanged for millions of years.

Boring Sponge

Oysters blanket the estuary floors in areas where they use foot secretions to cement themselves to the substrate. Not only are these oysters a rich food source for us, but they are also important food sources to many estuarine creatures. Predatory snails, including Oyster Drills, whelks, sponges, especially the Boring Sponges, and fish all find oysters a tasty treat.

The Black Drum has jaws powerful enough to crush adult oyster shells.

Leidy's Comb Jelly is a jellyfish that eats oyster larvae.

Estuaries - Characteristics

Habitats: Estuaries - Characteristics

Estuaries are partially enclosed bodies of water where freshwater (water without salt) meets salty ocean water.

Bays, inlets and ocean-flooded river valleys are all examples of estuaries.

Estuaries are divided into four types, depending on how they are formed:

1. Coastal Plain Estuaries are formed by the sea level rising and filling an existing river valley.

Examples of this are the Chesapeake Bay in Maryland and the harbor in Charleston, South Carolina

2. Tectonic Estuaries are caused by the folding or faulting of land surfaces.

These estuaries are found along major fault lines, like the San Francisco Bay area in California.

3. Bar-built Estuaries form when a shallow lagoon or bay is protected from the ocean by a sand bar or barrier island.

 Examples of these are found along the Eastern Seaboard and the Gulf Coast of North America.

4. Fjords are U-shaped valleys formed by glacial action.

 Fjords are found in areas with long histories of glacier activity, like northern Europe, Alaska and Canada.

Most of today's estuaries formed because the sea level has slowly risen during the last 18,000 years, drowning river valleys and filling in glacial troughs.