Amazon Estuary #2: General Info, Vertebrates, and Aquatic Plants

The Amazon Estuary has by far the largest water output of any estuary in the world, discharging an average of 46 million gallons (175 million liters) per second into the Atlantic. The sheer magnitude of this discharge means that, almost uniquely among estuaries, there is very little saltwater intrusion into it. Instead, nearly all of the mixing between the river’s discharge and seawater occurs outside the estuary, on an area of continental shelf. Despite the relative lack of seawater intrusion, the whole estuary is significantly affected by twice-daily tides, which cause inundation (by river water) of most of the islands in the estuary.

 Water plants play a key role in Amazon ecology. Many animals, such as the manatee, feed upon the plants. Their underwater roots are used for shelter and spawning by small fish, amphibians and crustaceans. The vegetation above water is home to a host of insect and spider species. Mats of water plants provide nesting sites for water birds such as the Jacana. The habitat also supports large water dwelling reptiles, such as caiman, monitor lizards and snakes, especially constrictors: the boas and the Anaconda.

There are many distinctive water plants but only a few are especially abundant and common. These play and especially important part in the dynamics of the forest and river. The water hyacinth and water lettuce are the two most common fully aquatic species. These can quickly block water ways, especially if their main consumer, the manatee, is absent, as it is in many places. Cane species then take over. If floods are insufficient to dislodge the mass of vegetation, it will remain and eventually undergo the succession process. During heavy floods, plant mats are broken up and passively float around the ecosystem, moved by river currents. This is undoubtedly important in distributing animals to places they may not otherwise reach (commensalism).

Of the water plants, the Giant Water Lily is the most famous for being by far the world's largest water lily. The pads measure up to six feet across, compared with most other species that reach at most one or two feet across.  Other important species are water hyacinth, water lettuce, water fern and various aquatic grasses.


  0°55'38.21"S
 48°27'46.58"W

Amazon River #1: Introduction and the Amazon Rainforest

The Amazon River and tropical rainforest has one of the highest levels of biodiversity on the planet. It produces almost 20% of the world's oxygen. Almost 16% of the world's river water flows through the Amazon delta. The Amazon Rainforest, though not an estuary, is extremely relevant to the Amazon River biome and therefore we will go into the rainforest in detail here.

The Amazon rainforest consists of four community layers. The emergent layer is the tallest layer, where trees can be as tall as 200 feet, and rise well above the canopy. Here they are exposed. They take advantage of the wind by developing winged seeds that are blown to other parts of the forest. Trunks can be up to 16 feet around and braced by massive buttress roots.

The main layer of the rainforest is the canopy. Most canopy trees have smooth, oval leaves that come to a point, known as a "drip tip". This allows water to flow off the leaf quickly and prevents the growth of fungi, mosses, and lichens. The canopy's leaves are very dense and filter out about 80% of the sunlight. Many flowers and fruits grow in this layer.

The understory only gets about two to five percent of the available sunlight. The plants find unique ways to adapt to this lack of light.. Their solar-collecting leaves grow large, and are dark green in color. They don't often grow more than 12 feet in height. Because there is very little air movement, they rely on insects and animals to pollinate their flowers. Some grow large flowers and fruits low on their trunks to allow larger, non-climbing animals to eat and disperse their fruit. The largest concentrations of insects inhabit this layer.

The forest floor is the lowest layer and almost no plants grow here. Only about 2% of the sunlight filters through. The floor is littered with decomposing vegetation and organisms that are broken down into usable nutrients. Many nutrients are locked into this biomass. Tree roots stay close to the surface to access these nutrients. Large animals forage for roots and tubers, while insects like millipedes, scorpions, and earthworms use the litter as a source of food.

Today, almost 20% of the Amazon rainforest has been destroyed by deforestation. Quite surprising, considering almost 40% of all medicines used today in the United States came at one time from a rainforest. The Amazon rainforest alone has provided over 230 medicines, natural cures, and remedies.

The destruction of the Amazon rainforest is a particularly serious issue when you consider the damage to the surrounding biomes, particularly the Amazon river biome. The two biomes are inexorably linked.

  1° 1'12.52"S
 48°28'9.96"W

Chesapeake Bay #6: Bay vegetation



Phyllospadix scouleri (surf grass)



Bay underwater grasses provide food and habitat for many species of fish, shellfish, and waterbirds. Many shellfish species use the grasses as nurseries for their young, including the blue crab. Grasses are often used to hide from predators, particularly by mollusks and small fish. Female blue crabs hide in the grasses after molting, when they are particularly soft and vulnerable.

Tiny crustaceons such as barnacles, sponges, and sea squirts all dine on underwater grass, as do zooplankton. Waterfowl also occasionally feed on the grasses.

Underwater grasses also keep the bay itself clean and healthy. They add oxygen to the water and trap sediments that would otherwise pollute the water and harm the organisms in it. The grasses also help to anchor soil that might be eroded.

Grasses themselves are fed by the excess of nutrients that come into estuaries.

 38°39'49.45"N
76°26'23.91"W

Chesapeake Bay #5: Birds

There are many birds that reside in the Chesapeake Bay estuary. The Great Blue Heron, considered a wading bird, a consumer of blue crabs and is ecologically significant. It is not commercially exploited. The American Osprey and the Bald Eagle are predatory raptors who are predators on the top of bay food chains.

38°30'50.72"N
76°28'31.05"W

Chesapeake Bay #4: Rockfish

Rockfish, also known as striped bass, stripers, or pimpfish, are one of the most commercially exploited fish in the bay. Rockfish is so delicious that it was designated the Maryland state fish in 1965.

Rockfish also play a valuable ecological role in the Chesapeake Bay. As one of the bay's top predators, they prey on menhaden and anchovies. Large population increases or declines (like the famous decline in the 1980s) often result in ecological chaos.

38°36'36.14"N
76°26'18.71"W

Chesapeake Bay #3 Crabs

Blue Crabs

Blue Crabs in the Chesapeake Bay

Blue crabs are a staple of Chesapeake Bay's aquaculture and fishing industries. Blue crabs are one of the most popular bay organisms to fish for. The commercial blue crab harvest in 2000 was approximately $55 million in value and about 1/3 of the United States' crabs come from Chesapeake Bay.

Blue crabs also have a lot of ecological value to the bay. They are, both as predator and prey, a keystone species in the Chesapeake Bay ecosystem. Birds, striped bass, drums, eels, catfish, cownose rays and some sharks all rely on the blue crab for their primary food source. Blue crab larvae are preyed upon by the planktonic community, including oysters, menhaden, bay anchovies and juveniles of other fish species. Blue crabs are also the primary consumer of the bay's benthos.

38°30'37.76"N
76°23'32.10"W