Ocean Water Chapter 21
Ocean Water Properties • Physical properties: temperature, density, color • Chemical properties: determine its composition and allow it to dissolve other substances
Composition of Sea Water • Water (duh): 96.5% pure water in oceans • Dissolved substances: 75 different elements, mostly in ion form • Most common elements: chlorine (Cl), sodium (Na), magnesium (Mg), sulfur (S), calcium (Ca), and potassium (K) • Dissolved gases: Carbon Dioxide (CO2) dissolves easiest, oxygen (O2) only at surface and nitrogen (N2)
Composition of Sea Water • Temperature and dissolved gases: as water temperature increases; the amount of dissolved gases decreases • Salinity: amount of dissolved solids present in ocean water (grams of solids in 1000 grams of ocean water) • Normal salinity is 35 g/1000g or 3.5%
Composition of Sea Water • Temperature and salinity: as temperature increases, evaporation of seawater increases, this makes warm oceans have higher salinity
Temperature of Ocean Water • Infrared: infrared (heat) waves from the sun are absorbed by the ocean; this heats the water, but only the upper layers. • Surface temperature: surface water mixes, so the top 100m to 300m is about the same temperature. • Freezing point of ocean water: -2°C
Temperature of Ocean Water • Tropical waters: can be as warm as 30°C • Temperate waters: can vary 10°C to 20°C between summer and winter. • Arctic waters: can be colder than -2°C during winter, so the water freezes and forms pack ice.
Temperature of Ocean Water • Deep water: usually around 2°C Thermocline • Zone of rapid temperature change between surface water and deep water • Makes a distinct separation between warm surface water and cold deep water • Keeps the layers from mixing
Density • Density: mass/volume (g/cc) • Density of pure water: 1.00g/cc Factors that effect sea water density • Salinity, dissolved solids raise density to 1.026 to 1.028g/cc. • Temperature: as temperature increases, density decreases, why deep water is colder (cold temps make it more dense and it sinks)
Color • Color of something depends on what colors of light it reflects • Light is a mixture of red, orange, yellow, green, blue, indigo and violet light • Ocean color: water absorbs all colors except blue, so clear ocean looks blue • Blue color could be clouded by rock particles or microscopic organisms—green or brown
21.2: Life in the Oceans Requirements for Life • Plants (algae/seaweed) provide food for all other marine life, therefore the requirements of plants are most important requirements. • Plants require CO2, O2, H2O, and S (sulfur)—all abundant in the upper layers of the ocean.
Requirements for Life • Plants need light, also abundant, but only in top 100 meters. • Plants also need nitrogen (N), phosphorus (P) and silicon (Si), these are typically not abundant. Algae often use all of these nutrients that are available.
Requirements for Life • Ocean plants absorb the nutrients they need, grow, die and sink to the bottom. • Bacteria at the bottom decompose the plants and return their nutrients to the water. • Sadly, these nutrients are at the bottom and the living plants are at the surface. • To maximize ocean life, there must be someway to get nutrients back to the surface.
Ways to Return Nutrients to Surface • Upwelling: when winds blow parallel to shore, the moves water away from the shore, nutrient rich deep water moves up to replace the surface water. Occurs on west coasts of Africa and North and South America—makes for fertile fishing grounds.
Ways to Return Nutrients to Surface • In shallow water, wave action can be strong enough to bring nutrients to surface. • Tides can also bring nutrients to surface
Types of Life in Oceans • Plankton: microscopic, free-floating organisms that exist in upper 100 meters. • Phytoplankton: plant-like plankton that do photosynthesis (make food from light), source of almost all food in ocean • Zooplankton: animal-like plankton that eat phytoplankton
Types of Life in Oceans • Nekton: ocean life that can swim, eat plankton or each other (depends on size) • Examples: fish, sharks, dolphins, whales, seals, squid • Benthos: ocean life that lives on the ocean floor • includes seaweed like kelp and animals like coral, sea anemones, starfish, crabs, clams
Marine Food Chains Phytoplankton Zooplankton--Krill Phytoplankton Anchovy Zooplankton--Krill Dolphin Sea Urchin Sea Otter
Ocean Environments • Ocean can be divided into two main environments. • Those environments are sub-divided on the basis of sunlight, temperature, and depth • Benthic environments—bottom • Pelagic environments—open water
Benthic Environments • Intertidal zone: likes between low tide and high tide marks, unstable environment, but plenty of light and nutrients • Sublittoral zone: always underwater, but shallow (continental shelf) • Bathyal zone: from the continental slope to 4,000 meters deep, very limited light
Benthic Environments • Abyssal zone: no light, 4000 to 6000 meters deep • Hadal zone: in trenches, deeper than 6,000 meters, life depends on food from above.
Pelagic Environments • Neritic zone: above the continental shelves, plenty of light, shallow water • Oceanic zone: over the deep waters of the ocean, only upper layer (epipelagic) is very populated with life forms
Ocean Resources—Water • Desalination: separation of fresh water from salt water. • Distillation: one method of desalination, boil water so it evaporates, then condense the water away from the salt. • Other desalination methods include: freezing (ice doesn’t contain salt) and reverse osmosis (passing through a membrane—done in Saudi Arabia and Kuwait)
Ocean Resources—Minerals • Nodules: clumps of minerals such as manganese (used in making steel), iron, copper, nickel, cobalt, and phosphates found in abyssal plains. Difficult to get, but potentially useful • Other minerals such as bromine and magnesium can be extracted from salt in ocean fairly cheaply
Ocean Resources—Minerals • Gold: found dissolved in salt in small quantities, about 6 kg/cubic kilometer. In other words, to get an ounce you would need to go through a million or more gallons of water • Petroleum: most important mineral in the ocean, found in continental margins, ¼ of world’s oil production comes from off-shore wells
Ocean Resources—Food • Ocean is an important source of protein rich food • Aquaculture is farming in the ocean, could produce more than twice the amount of protein as a land farm of the same size
Pollution • Ocean has long been seen as a suitable dumping ground for garbage, sewage, and nuclear wastes. • Runoff from the land can also had pollutants • Many coastal waters are polluted so that organisms from those waters are unsafe to eat