How Water Physics Affect Marine Life Choose to view chapter section with a click on the section heading. The Physics of Water How Water Physics Affect Marine Life Chapter Topic Menu

The Physics of Water The Physics of Water Chapter 9 Pages 9-3 to 9-15

The Physics of Water Seawater’s chemical properties affect how life functions in the ocean. Water’s physical properties not only affect life processes of marine organisms, but of human beings in the water. The Physics of Water Chapter 9 Page 9-3

Heat and Heat Capacity Temperature is crucial in determining where organisms can live in the ocean. The concept of temperature comes from the need to measure the relative heat of two bodies, or the same body after removing or adding heat. Suppose you’ve filled a bathtub with warm water and scooped out a glassful. If you take the temperatures of the water in the glass and the water in the tub, you’ll find they are the same. But, which has more heat? The Physics of Water Chapter 9 Pages 9-3 to 9-6

Heat and Heat Capacity Heat is the kinetic energy in the random movement, or vibration, of individual atoms and molecules in a substance. The faster molecules move, the more heat there is. Total heat energy is measured based on both the quantity and speed of vibrating molecules. Temperature measures only how fast the molecules vibrate. The two most common temperature systems are Fahrenheit and Celsius. Celsius is most used in science because it is based on water’s physical properties. The Physics of Water Chapter 9 Pages 9-3 to 9-6

Heat and Temperature The Physics of Water Chapter 9 Pages 9-3 to 9-6

Heat and Heat Capacity Heat capacity of a substance is the amount of heat energy required to raise a given amount of a substance by a given temperature. The Physics of Water Chapter 9 Pages 9-3 to 9-6

Heat and Heat Capacity Scientists express heat capacity in terms of the amount of heat energy it takes to change one gram of a substance by 1°C. It’s expressed as the number of calories required. It takes more heat energy to raise water’s temperature than that of most substances. The Physics of Water Chapter 9 Pages 9-3 to 9-6

Heat and Heat Capacity Therefore water can absorb or release a lot of heat with little temperature change. Water’s heat capacity affects the world’s climate and weather. Heat is carried to areas that would otherwise be cooler, and heat is absorbed in areas that would otherwise be hotter. The Physics of Water Chapter 9 Pages 9-3 to 9-6

Heat and Heat Capacity A great example is the island of Bermuda. Bermuda has a moderately tropical climate year round, even though it lies above 30° north latitude. That’s about the same latitude as Birmingham, Alabama, or Fort Worth, Texas, both of which experience some snow and freezing rain in the winter. The difference is that the warm Gulf Stream current flows around Bermuda. By carrying so much heat north, the Gulf Stream gives Bermuda a tropical climate. The Physics of Water Chapter 9 Pages 9-3 to 9-6

Heat and Heat Capacity The Physics of Water Chapter 9 Pages 9-3 to 9-6

Water Temperature and Density As water cools it becomes denser. At 3.98°C (39.16°F) it reaches maximum density. Below this point, it crystallizes into ice. As water moves into a solid state* it becomes less dense. The Physics of Water Chapter 9 Pages 9-7 to 9-8 Ice Liquid Water * State is an expression of a substance’s form as it changes from solid, to liquid, to gas with the addition of heat.

Water Temperature and Density Ice does not form all at once at the freezing point of 0°C (32°F), but crystallizes continuously until all liquid turns solid. Temperature does not drop any further until all the liquid water freezes, even though heat continues to leave. This produces non-sensible heat – a change in heat energy that cannot be sensed with a thermometer. The non-sensible heat lost when water goes from liquid to solid state is called the latent heat of fusion. Sensible heat is that which you can sense with a thermometer. The Physics of Water Chapter 9 Pages 9-7 to 9-8

Water Temperature and Density Relationship of Density to Temperature in Pure Water The Physics of Water Chapter 9 Pages 9-7 to 9-8

Water Temperature and Density Relationship of Density to Temperature in Most Substances The Physics of Water Chapter 9 Pages 9-7 to 9-8

Latent Heat of Vaporization Latent heat of vaporization is the heat required to vaporize a substance. It takes more latent heat to vaporize water than to freeze it because when water freezes only some of the hydrogen bonds break. When it vaporizes, all the hydrogen bonds must break, which requires more energy. The Physics of Water Chapter 9 Pages 9-9 to 9-11

Latent Heat of Vaporization Changing from a solid to a liquid. Changing from a liquid to a vapor. The Physics of Water Chapter 9 Pages 9-9 to 911

Latent Heat of Vaporization Latent Heat of Vaporization and Fusion The Physics of Water Chapter 9 Pages 9-9 to 9-11

Latent Heat of Vaporization Hydrological Cycle Shows the Movement of Water Around the Earth The Physics of Water Chapter 9 Pages 9-9 to 9-11

Thermal Inertia The tendency of water to resist temperature change is called thermal inertia. Thermal equilibrium means water cools at about the same rate as it heats. The Physics of Water Chapter 9 Pages 9-11 to 9-12

Thermal Inertia These concepts are important to life and Earth’s climate because: Seawater acts as a global thermostat, preventing broad temperature swings. Temperature changes would be drastic between night and day and between summer and winter. Without the thermal inertia, many – perhaps most – of the organisms on Earth could not survive the drastic temperature changes that would occur each night. The Physics of Water Chapter 9 Pages 9-11 to 9-12

Seawater density varies with salinity and temperature. Ocean Water Density Seawater density varies with salinity and temperature. This causes seawater to stratify, or form layers. The Physics of Water Chapter 9 Pages 9-13 to 9-14 Relationship Between Temperature, Salinity and, Density

Ocean Water Density Dense water is heavy and sinks below less dense layers. The three commonly found density layers are: Surface zone – varies in places from absent to 500 meters (1,640 feet). In general it extends from the top to about 100 meters (328 feet). This zone accounts for about only 2% of the ocean’s volume. Thermocline – separates the surface zone from the deep zone. It only needs a temperature or salinity difference to exist. This zone makes up about 18% of the ocean’s volume. Deep zone – lies below the thermocline. It is a very stable region of cold water beginning deeper than 1,000 meters (3,280 feet) in the middle latitudes, but is shallower in the polar regions. The deep zone makes up about 80% of the ocean’s volume. The Physics of Water Chapter 9 Pages 9-13 to 9-14

Ocean Water Density Density Layers The Physics of Water Chapter 9 Pages 9-13 to 9-14 Density Layers

Ocean Water Density The relatively warm, low-density surface waters are separated from cool, high-density deep waters by the thermocline, the zone in which temperature changes rapidly with depth. The top of the thermocline varies with season, weather, currents, and other conditions. It depends in part on the amount of heat the surface zone receives from the sun and is therefore more pronounced in tropical and temperate waters. Thermoclines are weaker in polar regions because the surface water there is cold. Thermocline zones account for about 18% of ocean water. The Physics of Water Chapter 9 Pages 9-13 to 9-14

Ocean Water Density Below the thermocline is the deep layer. This layer is cold, dense, and fairly uniform because it originates in the polar regions. It begins deeper than about 1,000 meters (3,280 feet) in the middle latitudes but becomes shallower until it reaches the surface in the polar regions. The deep zone makes up about 80% of the ocean’s volume. The Physics of Water Chapter 9 Pages 9-13 to 9-14

How Water Physics Affect Marine Life Chapter 9 Pages 9-16 to 9-33

Light Water scatters and absorbs light. When light reaches the water’s surface, some light penetrates, but, depending on the sun’s angle, much may simply reflect back out of the water. Within the water, light reflects off light-colored suspended particles. Dark colored suspended particles and algae absorb some of the light. Water molecules absorb the energy, converting light into heat. Water absorbs colors at the red end of the spectrum more easily than at the blue end. How Water Physics Affect Marine Life Chapter 9 Pages 9-16 to 9-20

Light Reflection, Scattering, and Absorption How Water Physics Affect Marine Life Chapter 9 Pages 9-16 to 9-20

Light Natural Light Artificial Light How Water Physics Affect Marine Life Chapter 9 Pages 9-16 to 9-20 Artificial Light

Light Two zones exist with respect to light penetration: Photic Zone – where light reaches (can be as deep as 590 meters/1,968 feet). The photic zone has two subzones. Euphotic Zone – the upper shallow portion where most biological production occurs – comprises about 1% of the ocean. Dysphotic Zone – where light reaches, but not enough for photosynthetic life. Aphotic Zone – it makes up the vast majority of the ocean. Where light does not reach and only a fraction of marine organisms live. How Water Physics Affect Marine Life Chapter 9 Pages 9-16 to 9-20

Light How Water Physics Affect Marine Life Chapter 9 Pages 9-16 to 9-20

Temperature Seawater doesn’t fluctuate in temperature nearly as much as air does. Marine organisms rarely encounter temperatures below 1.9°C or above 30°C. Compared to land-based climates, this narrow range provides an advantage. Compared to land-based climates, marine organisms live in a much less challenging environment with respect to temperature range. Generally, temperature dictates the rate of chemical reaction. How Water Physics Affect Marine Life Chapter 9 Pages 9-21 to 9-22

Temperature Most marine organisms have an internal temperature close to that of surrounding seawater. Their internal temperature changes with seawater temperature. An organism with this characteristic is called an ectotherm. Ectotherms are commonly called cold-blooded organisms, and include terrestrial as well as marine organisms. How Water Physics Affect Marine Life Chapter 9 Pages 9-21 to 9-22

Temperature Other marine organisms, such as certain tuna and sharks, have an internal temperature that varies, but remains 9˚ to 16˚C warmer than the surrounding water. Organisms with this characteristic are called endotherms. Marine mammals and birds have an internal temperature that is relatively stable. Organisms with this characteristic are called homeotherms. Some endotherms have a body temperature above their surroundings, but it is not constant and varies with the surrounding temperature. Organisms with this characteristic are called poikilotherms. Endotherms are commonly called warm-blooded organisms. How Water Physics Affect Marine Life Chapter 9 Pages 9-21 to 9-22

Temperature Temperature affects metabolism – the higher the temperature within an organism the more energy-releasing chemical processes (metabolism) happen. Endotherms and homeotherms can tolerate a wide range of external temperatures. Internal heat regulation allows endotherms an advantage. Their metabolic rate remains the same regardless of external temperature allowing them to live in a variety of habitats. How Water Physics Affect Marine Life Chapter 9 Pages 9-21 to 9-22

Sound Sound is energy that travels in pressure waves. It can only travel through matter, which is why there’s no sound in outer space. Sound travels well in air, but even better in water. In distilled water at 20˚C/68˚F, sound travels 1,482.4 meters (4,863.4 feet) per second, which is about five times faster than in air. How Water Physics Affect Marine Life Chapter 9 Pages 9-22 to 9-24

Sound Travels through warm water faster than cool… but it travels faster in deep water due to pressure. Bounces off suspended particles, water layers, the bottom and other obstacles. Travels much farther through water than light does. Is eventually absorbed by water as heat. How Water Physics Affect Marine Life Chapter 9 Pages 9-22 to 9-24

Sound Because sound travels so well in water, marine mammals use echolocation to sense an object’s size, distance, density, and position underwater. How Water Physics Affect Marine Life Chapter 9 Pages 9-22 to 9-24

Pressure Right now, you’re under pressure. If you’re at sea level, you’re under the pressure of the atmosphere, which is literally the weight of the air. Water weighs far more than air, so marine organisms exist in an environment with greater surrounding pressure than land-based organisms do. How Water Physics Affect Marine Life Chapter 9 Pages 9-25 to 9-28

Pressure How Water Physics Affect Marine Life Chapter 9 Pages 9-25 to 9-28

Pressure Pressure exerted by water is called hydrostatic pressure. It’s simply the weight of the water. At 10 meters (33 feet) hydrostatic pressure is equal to atmospheric pressure – 1 bar/ata. At 10 meters (33 feet) the total pressure is 2 bar – 1 bar from atmospheric pressure plus 1 bar from hydrostatic pressure. A marine organism living at 10 meters (33 feet) experiences twice the pressure present at sea level. Pressure increases 1 bar for each additional 10 meters (33 feet). How Water Physics Affect Marine Life Chapter 9 Pages 9-25 to 9-28

Pressure How Water Physics Affect Marine Life Chapter 9 Pages 9-25 to 9-28

Pressure Hydrostatic pressure doesn’t affect marine organisms because it is the same inside the organism as outside. Living tissue is made primarily of water, which (within limits) transmits pressure evenly. Since it’s in balance, pressure doesn’t crush or harm marine organisms. Hydrostatic pressure is primarily an issue only for organisms that have gas spaces in their bodies. How Water Physics Affect Marine Life Chapter 9 Pages 9-25 to 9-28

Pressure Many fish have a gas bladder that they use to control their buoyancy. They must add or release gas from the bladders when they change depth to keep the pressure in balance. Similarly, scuba divers learn to add air to the space in their ears (a technique called equalizing because it equalizes the pressure inside the air space with the pressure outside), which allows them to dive without discomfort. Failure to equalize can cause the pressure to rupture the diver’s ear drums. How Water Physics Affect Marine Life Chapter 9 Pages 9-25 to 9-28

Pressure and Gas Volume Relationships How Water Physics Affect Marine Life Chapter 9 Page 9-27

Size and Volume Marine organisms thrive by getting all the resources they need from the water around them. Each cell gets the nutrients and gas it needs from the surrounding environment and excretes waste products into that environment. Single-cell organisms, such as protozoa or bacteria, make these exchanges directly to and from seawater. A multicellular organism, such as a sea cucumber or a fish, uses systems to gather nutrients and gas from the environment and excrete waste. The cells within a multicellular organism make the exchanges via the organism’s systems rather than directly with the surrounding water. How Water Physics Affect Marine Life Chapter 9 Page 9-28

Size and Volume High surface-to-volume ratio is important for cell function. The bigger the cell, the lower the surface-to-volume ratio, which means that there’s less relative area through which to exchange gases, nutrients, and waste. This is why large organisms are multicellular rather than a giant single cell. How Water Physics Affect Marine Life Chapter 9 Page 9-28

Size and Volume Using a sphere to substitute for a cell: The volume of a sphere increases with the cube of its radius and the surface area increases with the square of its radius. If a cell were to increase diameter 24 times original size, the volume would increase 64 times, but the surface area would increase only 16 times. How Water Physics Affect Marine Life Chapter 9 Page 9-28

Buoyancy Archimedes’ Principle states that an object immersed in a gas or liquid is buoyed up by a force equal to the weight of the gas or liquid displaced. How Water Physics Affect Marine Life Chapter 9 Pages 9-29 to 9-31

Buoyancy Floats Sinks Floats How Water Physics Affect Marine Life Chapter 9 Pages 9-29 to 9-31 Floats

Buoyancy Means marine organisms don’t have to expend much energy to offset their own weight compared to a land-based existence. It allows entire communities to exist simply by drifting. It allows organisms to grow larger than those on land. It allows many swimming creatures to live without ever actually coming into contact with the bottom. How Water Physics Affect Marine Life Chapter 9 Pages 9-29 to 9-31

Buoyancy Buoyancy Makes Size Possible How Water Physics Affect Marine Life Chapter 9 Pages 9-29 to 9-31 Buoyancy Makes Size Possible

Movement and Drag While marine organisms have an advantage over land-based organisms with respect to buoyancy, the situation is reversed when it comes to drag. Because water has a far higher viscosity than air, it resists movement through it far more than air does. Consider what happens when you’re in a swimming pool; it takes very little effort to push yourself off the bottom thanks to buoyancy. However, it takes far more effort to swim a long distance than to run the same distance. This is due to drag. How Water Physics Affect Marine Life Chapter 9 Pages 9-31 to 9-32

Movement and Drag Viscosity affects small organisms, plankton in particular. Their small size gives them little strength to swim through water. Small marine organisms avoid sinking by: Plumes, hairs, ribbons, spines, and other protrusions that increase their drag and help them resist sinking. Others have buoyancy adaptations that help them remain suspended in the water column (oil in tissues). How Water Physics Affect Marine Life Chapter 9 Pages 9-31 to 9-32

Movement and Drag Some marine organisms need to overcome drag as they swim. Adaptations that help them overcome drag: Moving or swimming very slowly. Excreting mucus or oil that actually lubricates them to “slip” through the water. The most common is to have a shape that reduces drag – streamlining. How Water Physics Affect Marine Life Chapter 9 Pages 9-31 to 9-32

Movement and Drag Drag, Streamlining, and Turbulence How Water Physics Affect Marine Life Chapter 9 Pages 9-31 to 9-32 Drag, Streamlining, and Turbulence

Currents It is speculated that drifting provides several advantages. Drifting disperses organisms into new habitats, ensuring survival should something happen to the original community. May take organisms into nutrient-rich areas, preventing too many offspring from competing for the same resources in the original community. How Water Physics Affect Marine Life Chapter 9 Pages 9-32 to 9-33