BIOL 111 Chapter Notes - Chapter 7: Hadal Zone, Littoral Zone, Benthic Zone
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AQUATIC LIFE ZONES
1. Most aquatic life zones can be divided into three layers: surface, middle, and bottom.
2. Levels of dissolved O2 are highest near the surface. Levels of CO2 are lowest near the surface.
3. Photosynthesis is confined to the surface, or the euphotic zone, where sunlight can penetrate.
4. Saltwater and freshwater life zones contain four major types of organisms:
Decomposers (mostly bacteria).
Benthos (eg, barnacles, oysters, lobsters, crabs), which dwell on the ocean floors.
Strongly swimming nekton (consumers), such as fish, turtles, and whales.
Weakly swimming, free-floating plankton, carried by currents.
Phytoplankton (producers), such as many types of algae.
Ultra-plankton, photosynthetic bacteria responsible for 70% of aquatic photosynthesis.
5. Saltwater life zones contain about 250,000 known species.
The coastal zone is the warm, nutrient-rich, shallow water.
Although it makes up 10% of the oceans, it contains 90% of all marine species.
Estuaries are partially enclosed areas where seawater mixes with freshwater.
Coral reefs form in clear, warm, coastal waters of the tropics and subtropics.
The sharp increase in water depth with a vast volume of ocean is the open sea.
The euphotic zone is the lighted, upper zone where photosynthesis occurs.
The bathyal zone is the dimly lit, middle zone that sunlight cannot penetrate.
The lowest zones, called the abyssal and hadal zones, are dark, cold, and under pressure.
6. Freshwater life zones cover 1% of Earth, and have salt concentrations which are less than 1%.
Lakes are bodies of standing water, formed by glaciation and/or crustal displacement.
The littoral zone is the shallow, sunlit water near the shore.
The limnetic zone is the open, sunlit water away from the shore.
The profundal zone is the deep, open water where it is too dark for photosynthesis.
The benthic zone is at the bottom of the lake, mainly consisting of decomposers.
Epilimnion is warm & oxygenated water. Hypolimnion is cold, less oxygenated water.
A turnover is when convection mixes nutrients at the bottom with O2 at the top.
An oligotrophic lake is a newly formed lake has small supply of nutrients.
A eutrophic lake is a lake with a large supply of nutrients.
A mesotrophic lake is a lake that falls somewhere between these two extremes.
The downward flow of water from mountains to the sea takes place in three zones:
The narrow, source zone, which includes cold, clear water & waterfalls (steep slopes).
The middle, transition zone, where water streams merge to form wider streams.
The floodplain zone, where streams join into wider & deeper rivers across flat valleys.