Aquatic Ecosystems

Nearly 75 % of the planet is covered with water. It only makes sense that most life may be found in water. Aquatic ecosystems are determined primarily by the depth, flow, temperature, and chemistry of the overlying water. The depth of the water determines the amount of light that the area receives.

The chemistry refers primarily to the amount of dissolved chemicals --- salts, nutrients, and oxygen -- on which life depends. Only 3% of the water on earth is fresh water. Freshwater systems are divided into two main types: flowing and standing ecosystems.

Flowing ecosystems Rivers, streams, creeks, and brooks. insect larvae, catfish, trout origin in mountains or hills plants usually establish further downstream where the flow is slower. turtles, beavers, otters downstream creatures

Standing Water Lakes and ponds Water usually circulates heat, oxygen, and nutrients Plankton are usually found in lakes and ponds Plankton is a general term for the tiny, free floating organisms that live in both freshwater and saltwater environments.

Freshwater Wetlands An ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year. Water may be flowing or standing, fresh, salty, or brackish. Brackish is a mixture of fresh and salt water. Wetlands serve as breeding grounds for insects, birds, fish, and amphibians.

Wetlands The three main types of freshwater wetlands are bogs, marshes, and swamps. Bogs form in depressions called kettle holes left by ice sheets that melted thousands of years ago. Sphagnum moss may be found here. Marshes are shallow wetlands along rivers. Cattails, rushes, tall grasslike plants Swamps – slow flowing water, trees, shrubs

Estuaries Wetlands that form where rivers meet the sea. Contain fresh and saltwater….affected by the rise and fall of ocean tides. Shallow, so light hits bottom for photosynthesis to occur. plantlife, algae, photosynthetic and chemosynthetic bacteria Most production is not consumed by herbivores……clams, worms, sponges, shrimp, crab, birds.

Estuaries continued Much organic material enters as detritus Detritus is made up of tiny pieces of organic material. Salt Marshes – temperate zone estuaries dominated by salt tolerant grasses above the low tide line, and by seagrasses under water. Mangrove swamps – coastal wetlands that are widespread across tropical regions (southern florida) salt tolerant trees (mangroves) seagrasses, nurseries for fish and shellfish. Largest mangrove area is in Florida’s Everglades

Marine Ecosystems Sunlight only penetrates a short distance. Photosynthesis is limited to the photic zone….depth of 200 meters. Below the photic zone is the aphotic zone ….it is permanently dark. Chemosynthetic autotrophs are the only producers that can survive in the aphotic zone.

Classification Systems for Marine Ecosystems Intertidal zone, coastal ocean, open ocean, benthic zone.

Intertidal Zone Organisms exposed to extreme changes. Submerged in sea water, exposed to air, temperature changes, and sunlight. Battered by strong currents. barnacles, seaweed, snails, sea urchins, sea stars Competition results in zonation. Zonation - the prominent horizontal banding of organisms that live in a particular habitat.

Coastal Ocean Extends from the low tide mark to the outer edge of the continental shelf. Mostly photic rich in plankton and other organisms kelp forests snails, sea urchins, sea otters, fishes, seals, and whales.

Coral Reefs Warm shallow water of coastal, tropical oceans. Named for the coral animals whose hard, calcium carbonate skeletons make up their structure. jellyfish, fish, microscopic animals.

Open Ocean The largest marine zone. 500 meters to 11,000 meters High pressure, frigid temperatures, total darkness. Very low levels of nutrients. Swordfish, octopus, dolphins, whales

Benthic Zone The ocean floor contains organisms that live attached to or near the bottom. sea stars, anemones, marine worms Depend on food from organisms that grow in the photic zone. mostly attached to the bottom and do not move around much. clams, sea cucumbers

Populations Three important characteristics of a population are its geographic distribution, density, and growth rate. Geographic distribution - range Population density – the number of individuals per unit area.

Population Growth Three factors can affect population size: the number of births, the number of deaths, and the number of individuals tht enter or leave the population. Immigration – the movement of individuals into an area Emigration – the movement of individuals out of a population Food shortages may result in emigration.

Exponential Growth Occurs when the individuals in a population reproduce at a constant rate. Under ideal conditions with unlimited resources, a population will grow exponentially.

Logistic Growth As resources become less available, the growth of a population slows or stops. Logistic growth occurs when a population’s growth slows or stops following a period of exponential growth.

Carrying capacity the largest number of individuals that an environment can support. Limiting Factors – competition, predation, parasitism, disease, drought, human disturbances, limited nutrients.

Density Dependent Factors A limiting factor that depends on population size is called a density dependent limiting factor. Include competition, predation, parasitism, and disease. The best method of population control is the predator-prey relationship. The predator-prey relationship follows a cycle of increasing and decreasing numbers.

Density Independent Factors Unusual weather, natural disasters, seasonal cycles, human activities. Extreme cold can wipe out many plant and insect species.

Human Activities Hunting, gathering, agriculture, industry, and urban development have transformed the biosphere. 1950’s -- fast growing global human population forced agriculture to increase production…this era is now known as the green revolution. monoculture – the planting of large crops year after year….the advantage….lots of the same food….the disadvantage…increased use of water, increase in certain insect populations….heavy use of pesticides…chemicals can be harmful to environment, other species, and humans.

The tragedy of the Commons When a resource is open to everyone, no one is responsible for preserving it, so we eventually destroy it. Environmental Resources can be classified into two types: renewable and nonrenewable. Renewable resources can be replenished but they are now LIMITED due to our population. Nonrenewable resources cannot be replenished naturally but may be replenished in the lab. Synthetic oil

Sustainable Use A way of using natural resources at a rate that does not deplete them. Soil is renewable but can be damaged beyond use. Problems with overfishing -- no one country can control fishing in open ocean waters. Aquaculture -- farming of aquatic organisms is part of the solution.

Air resources Smog, acid rain WATER RESOURCES wastes, sewage, chemicals, oil spills

Biodiversity The sum total of the genetically based variety of all organisms in the environment. Extinction occurs when a species disappears from all or part of its range. Endangered species…..a species whose population size decreases in such a way to place it in danger of extinction.

Habitat Fragmentation The dividing of a habitat by human activity. The smaller the area, the fewer species that may be maintained there.

Invasive Species Apparently harmless plants and animals that we transport from one place to another. The new area lacks the parasites and predators that control the population and their numbers increase beyond control. Native species may be brought to extinction or endangered.