Properties of the Ocean Water, Salinity, Light, and Dissolved Oxygen

Water’s Unique Properties

Properties of Water It is the only natural substance that is found in all three states of matter on Earth- solid, liquid, and gas Also called the universal solvent- meaning many things can be dissolved in water Has a high heat capacity, so water can absorb a lot of solar energy without its temperature increasing

Density of Water Unlike any other substance, the density of water is the greatest at 4⁰C (as a liquid) So, ice floats on water!

Composition of Seawater pH 7.5 to 8.4 Salinity of oceans remain constant Contains various salts, such as sodium, magnesium, and potassium chlorides Contains organic carbon compounds Contains dissolved gases- oxygen, carbon dioxide, and nitrogen

Composition of Seawater

Salinity Why is the Sea Salty?

What is Salinity? Total amount of salt dissolved in sea water. Typical salinity of: Freshwater – 0 grams per 1000 mL of water Saltwater – 35 grams per 1000 mL of water Brackish – mixture of both Hypersaline – over 39 ppt Usually referred to as Parts Per Thousand or ppt

Depth vs. Salinity As depth increases salinity increases Colder water pushes particles closer together – increasing the salinity Halocline A distinct depth at which salinity drastically increases. Typically starts at 100 meters and ends at 200 meters

Processes Affecting Sea Water Salinity Precipitation – adds more water, decreases salinity Runoff – adds more water, decreases salinity Coastal waters are less salty Icebergs melting – adds more fresh water, decreases salinity Sea Ice Melting – adds more water and very little salt – decreases salinity Sea ice forming – takes away fresh water – increases salinity Evaporation – takes away fresh water – increases salinity

Salinity and Latitude Highest salinities are recorded at 20 degrees North and 20 degrees South. Highest amount of evaporation and the least amount of precipitation Lower at the equator – more precipitation Higher latitudes have lower salinities – less evaporation and melting of polar ice adds more fresh water to the ocean and decreases the salinity

Salinity and Latitude Salinity and Ocean Currents What Aquarius Found

Water Water everywhere Drinking Sea Water? Drinking sea water causes the water in your cells to diffuse out The salt doesn’t go into your cells because the molecules do not fit through the membrane Water Water everywhere And not a drop to drink!

Osmoregulation Ability of aquatic organisms to maintain proper balance of water and salt. Osmosis – movement of water molecules from area of high concentration to low concentration Both salt and fresh water fish have to deal with maintaining water balance!

Hypotonic Environment When a cell is in a hypotonic environment, there is a higher concentration of salt inside the cell than outside As a result, water moves into the cell, and it swells and bursts When a fish is in freshwater, it continuously gains water by osmosis

Hypertonic Environment When a cell is in a hypertonic environment, there is a higher concentration of salt outside the cell than inside As a result, water diffuses out of the cell, and it shrivels and shrinks When a fish is in salt water, it continuously loses water by osmosis

Osmoregulation Adaptations Freshwater Fish Gains water by osmosis Special kidneys to get rid of excess water Saltwater Fish Loses water by osmosis Must continuously drink to stay hydrated Salt glands to remove excess salt

Light and Dissolved Oxygen

Why is Light Important? Essential for photosynthesis, which produces oxygen Sunlight is the primary source of energy for all living things (beginning of all food chains) Sunlight also warms up the ocean

Relationship between Light and Color Visible light is a form of radiant energy This energy penetrates into the ocean at a maximum depth of 200 meters Different colors are all absorbed and reflected differently

Why Does Water Appear Blue? Blue wavelengths are absorbed the least by the deep ocean water and are scattered and reflected back to the observer’s eye Particles in the water help to reflect blue light Light and Color in the Sea

Relationship Between Wavelength, Frequency, and Energy Shorter wavelengths = Greater Frequency = More Energy! The more energy a wavelength of light has, the farther (and deeper) it can travel in the ocean! Blue light has a very short wavelength, therefore it has a lot of energy, and can travel the deepest

What Reduces the Amount of Light Reaching the Bottom? Suspended sediments within the water Overabundance of zooplankton and phytoplankton Cloudy waters are called turbid

What is Dissolved Oxygen? (DO) Molecular oxygen O2 dissolves in water Measured in parts per million or ppm Ocean water can hold 1-12 ppm of DO. Below 3 is not healthy The oxygen molecule in DO is separate from the oxygen in H2O.

Why is Dissolved Oxygen Important? Oxygen is required for respiration, a life process that all organisms must undergo in order to survive Organisms use oxygen to produce ATP, an energy molecule used by every cell

How Does DO Get into the Water? Most dissolved oxygen enters from the air! Winds blowing over a body of water help DO to diffuse Oxygen is also released by marine plants as a byproduct of photosynthesis Most DO is produced from 0-200 meters. Why?

What Factors Affect DO Levels? Temperature – oxygen is more soluble in cooler temperatures (cold water molecules are close together, trapping in the gas and dissolving it MORE DO in COLD water Respiration – all aquatic plants and animals use up DO Plants photosynthesize in the light but they also do respiration! Overcrowding of organisms decreases DO Decomposition – bacteria that decomposes dead and decaying material use DO to break these things down.

Temperature vs. Dissolved O2

Why is the Water in the Caribbean so clear? The sediments in the Bahamas and Hawaii tend to be composed of heavier particles that are not as easily stirred up or suspended There tends to be far less phytoplankton and zooplankton in the water due to very low nutrients in the Bahamas and Hawaii. There is lower dissolved oxygen because the waters are warmer