Ocean Properties

Ocean Concepts Buoyancy Temperature Light Density Pressure Depth Sound

Buoyancy

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Archimedes Principle of Buoyancy A floating object displaces a volume of fluid equal in mass to the floating object empty loaded with fish Displaced water

Objects that are more dense than water will sink. Objects that are less dense than water will float. Objects that are the same density as water will neither sink nor float. float Neutrally buoyant sink

Blubber Swim bladder Pneumatophore Organisms adaptation to buoyancy in water

Air chambers Large liver & heterocercal tail Buoyancy Compensator Device (BCD) Organisms adaptation to buoyancy in water

Temperature

Isotherms Lines of equal temperature 60 o 30 o 0o0o 60 o polar temperate tropic temperate

Sea Surface Temperature Oct. 2010

Sea Surface Temperature

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Properties of Light in the Ocean

The Electromagnetic Radiation Spectrum Only green and blue wavelengths pass through water a great distance.

Light Absorption in the Ocean Light Intensity –decreases with depth –0-100 m (photic zone) – m (dysphotic zone) –>1000 (aphotic zone)

Coral Reef Communities

Hermatypic corals: possess zooxanthellae are reef builders Light: Clear water Warm temperature: o C Low nutrients Low productivity in water Ahermatypic corals: no zooxanthellae rely on tentacular feeding can live in aphotic zone

Cauliflower coral (Pocillopora meandrina) 6 m 0 m 25 m 13 m Lobe coral (Porites lobata) Finger coral (Porites compressa) Plate coral (Porites rus) High light levels Moderate wave energy Moderate light levels Occasional storm wave energy Low light levels Low wave energy Very low light, Primarily downwelling No wave energy

Water color and life in the ocean Ocean color is influenced by: –The amount of turbidity from runoff –The amount of photosynthetic pigment, which corresponds to the amount of productivity Yellow-green = highly productive water –Found in coastal and upwelling areas (eutrophic) Clear indigo blue = low productivity water –Found in the tropics and open ocean (oligotrophic)

Light Penetration in the Ocean ~65% of visible light is absorbed in the 1 st m Photic Zone Aphotic Zone No Photosynthesis 100m 0 m Wavelength (nm) Photosynthesis Dysphotic Zone 1000m

Light Absorption in the Ocean Spectral Characteristics –red wavelengths absorbed more readily by water than blue wavelengths –blue light penetrates deepest in the oceans

Light effects organisms residing in the photic and aphotic zone. Phytoplankton productivity Algae- green, brown, red Predator/Prey relationships Diurnal vertical migration Bioluminescence- luminescent organs on underside mimic downwelling light

Refraction- as light enters the water, it bends; this is due to light traveling through different densities Light entering the ocean is weakened by scattering and absorption.

Density

Density Air 0.08 lbs 1 ft fw 62.4 lbs 1 ft sw 64 lbs 1 ft Piston example: Air is compressibleWater is incompressible

64 lbs Water doesn’t change density under pressure

Ocean Layers Photic zone: 0-100m - neustonic layer: 0-1m Mesopelagic (dysphotic or twilight) zone: m Aphotic zone: bathypelagic zone m Abyssal and Hadal (trench) zones: 6000m Describe biological and physical characteristics of each depth

TemperatureSalinityDensity Low High Low High LowHigh surface 0 m 100 m 1000 m Thermocline + Halocline = Pycnocline thermoclinepycnoclinehalocline

Thermocline El Nino –Disruption of thermocline Upwelling areas –Cool, nutrient-rich deep water is brought to the sunlit surface –Peru fisheries

Thermocline Temperature profile depth

Peru Anchovy Fishery

Upwelling zone off Peru Fishery began 1950 Greatest fish catches for any single species Fish exported for domestic animal feed Fishery collapsed due to El Niño and overfishing

= El Niño Peru Anchovy Fishery

Normal Year El Niño Year

Sound in Water

Speed of sound- faster in ocean (higher density) 1500 m/sec, which is 4x faster than in air Difficult to determine direction of sound Can hear many things such as ships miles away, shrimp eating, helicopters overhead, and whales communicating. Sound in Water source of noise

Depth (m) Speed of Sound (m/sec) 1,475 1,500 sofar layer min speed high speed

Depth (m) SOFAR Channel Distance SOFAR channel sound rays

The depth at which the speed of sound is minimum; Thus, loud noises can be heard for thousands of km Sound generated by Navy test in Indian Ocean at sofar layer was heard as far away as the Oregon coast. May affect behavior and anatomy of marine organisms Sofar Layer

Diurnal vertical migration Organisms within the deep scattering layer undertake a daily migration to hide in deep, darker waters during daytime

Deep sea scattering layer: Composite echogram of hydroacoustic data showing a distinct krill scattering layer. Black line represents surface tracking of a blue whale feeding patchiness

Ocean Productivity

Regional productivity Photosynthetic productivity varies due to: –Amount of sunlight –Availability of nutrients Thermocline (a layer of rapidly changing temperature) limits nutrient supply Examine three open ocean regions: 1.Polar oceans (>60° latitude) 2.Tropical oceans (<30° latitude) 3.Temperate oceans (30-60° latitude)

Productivity in tropical, temperate, and polar oceans Zooplankton

Productivity polar oceans

Productivity in tropical oceans

Productivity in temperate oceans

O 2 Minimum Zone (OMZ)

O 2 Content (ml/L) Water depth (m)

What causes the O 2 minimum layer? Marine snow

Why are there high levels of O 2 at depth?

O 2 Dead Zones

Inquiry 1.What zone does photosynthesis occur? 2.Why does light appear to bend when it enters water? 3.Which wavelength of light penetrates the ocean the deepest? 4.What is SOFAR? 5.Describe the relationship between El Nino and Peru Upwelling. 6.What causes the OMZ? 7.How do sharks maintain buoyancy? 8.What areas in the ocean are the most productive? 9.Why is the open ocean considered a biological desert?