Env. Science: Aquatic Ecosystems
75% of Earth’s surface is covered by water.
Salinity: the amount of dissolved salt present in water.
Ecosystems are classified as salt water, fresh water, or brackish depending on salinity.
Keeps a lot of the currents going.
Water with salinity between 0.5 and 30 ppt is considered brackish, above 30 ppt is salt water, and water with less than 0.5 ppt is fresh.
Photosynthesis tends to be limited by light availability, which is a function of depth and water clarity.
Aquatic ecosystems are either flowing or standing.
Aquatic ecosystem zones: photic, aphotic, benthic.
Photic: the uppermost layer of the aquatic ecosystem where there is enough light for photosynthesis.
Aphotic: the layer just below the photic layer where there is no sunlight and photosynthesis cannot occur.
Benthic: the very bottom of a body of water that can be sunlit or pitch black depending on the depth and clarity of the water.
Consumers on the land require oxygen to breathe and some aquatic consumers, such as sea turtles and whales, breathe in air by periodically rising to the top of the water.
Most aquatic consumers do not breathe air. Instead, they obtain the oxygen they need to carry out cellular respiration from water taken in through the gills.
Most of the dissolved oxygen is in the photic layer.
The presence of sunlight not only causes photosynthesis but also causes warmer water temperatures.
The upper layers of the aquatic ecosystems tend to be warmer than the deeper layers because of sunlight.
Temperature shifts can happen due to seasonal temperature changes of shifting currents.
Ponds and lakes are similar, except in size, but inland seas contain organisms adapted for open water.
Ponds and lakes are divided horizontally into the littoral and limnetic zones.
Littoral zone: the shore area
Limnetic zone: the end of the littoral zone until the other end of the pond/lake.
Areas of land flooded with water for at least part of the year are known as wetlands, which are freshwater ecosystems.
Include freshwater marshes, swamps, bogs, and fens.
Wetlands prevent flooding, recharge aquifers, filter pollutants, and provide habitats to other organisms.
Bodies of surface water that flow downhill, eventually reaching an ocean or inland sea, are known as rivers and streams, which are freshwater ecosystems.
Watershed: the area of land drained by a river and its tributaries.
Characteristics, such as dissolved oxygen, temperature, water speed, organisms, and others, change from source to mouth.
Estuaries occur where a river flows into the ocean or an inland sea.
Coastal estuaries are brackish ecosystems; organisms must tolerate wide salinity and temperature changes.
Coastal estuaries are home to salt marshes and mangrove forests.
Like wetlands, estuaries help prevent flooding and soil erosion as well as provide habitats.
Ocean currents are driven by water temperature and density differences, wind, and gravity.
Surface winds and heating generate vertical currents that transport nutrients and oxygen.
Horizontal ocean zones: intertidal, neritic, open ocean.
Intertidal: spread between the uppermost reach of the high tide and the lowest limit of the low tide.
Highly diverse; extreme range of temperature, moisture, and salinity.
Intertidal organisms spend part of the day submerged in water, part of the day exposed to the air and sun, and part of the day being lashed by waves.
Neritic: extends from the low tide tine to the edge of the continental shelf.
Productive kelp forests and coral reefs provide habitats and help protect shorelines from erosion.
Open ocean: low productivity due to low light penetration; phytoplankton base of the food chain; deep-sea organisms and hydrothermal vent communities.
Vertical ocean zones: photic, aphotic, benthic.