oceanography. one of the most obvious differences between pure water and seawater is the salty taste

Ocean Water and Ocean LifeOceanograp

hy

Composition of SeawaterOne of the most obvious

differences between pure water and seawater is the salty taste.

Composition of SeawaterThe dissolved substances

include sodium chloride, other salts, metals, and dissolved gases.

Composition of SeawaterEvery known naturally

occurring element is found dissolved, at least trace amounts, in seawater.

Composition of SeawaterThe salt content makes it

unsuitable for drinking or irrigation, but many parts of the ocean are full of life adapted to this environment.

SalinityThe total amount of solid

material dissolved in water.The ratio of the mass of

dissolved substances to the mass of the water sample.

SalinityBecause the proportion of

dissolved substances in seawater is such a small number, oceanographers typically express salinity in parts per thousand.

SalinityWhat is the salinity of

seawater?

3.5%35‰

SalinityMost of the salt in seawater

is sodium chloride, common table salt.

Sources of Sea SaltsChemical weathering of

rocks on the continents is one source of elements found in seawater.

Sources of Sea SaltsThese dissolved materials

reach oceans through runoff from rivers and streams at an estimated rate of more than 2.3 billion metric tons per year.

Sources of Sea SaltsThe second major source of

elements found in seawater is from the Earth’s interior.

Sources of Sea SaltsThese dissolved materials

come from volcanic eruptions 4 billion years ago.

Sources of Sea SaltsCertain elements—

particularly chlorine, bromine, sulfur, and boron—exist in much greater quantities than could be explained by weathering of rocks alone.

Processes Affecting SalinityBecause the ocean is well

mixed, the relative concentrations of the major components in seawater are essentially constant.

Processes Affecting SalinitySome of the different

processes that affect the amount of water include precipitation, runoff from land, iceberg melting, and sea ice melting.

Processes Affecting Salinity Other processes, evaporation

and formation of sea ice, remove large amounts of fresh water.

Processes Affecting SalinityVariation in ocean surface

temperature and surface salinity

Ocean Temperature VariationThe ocean’s surface water

temperature varies with the amount of solar radiation received, which is primarily a function of latitude.

Temp Variation with DepthIf you lowered a thermometer

from the surface of the ocean into deeper water, what temperature pattern do you think you would find?

Warmer water on top.

Temp Variation with DepthAt a depth of about 1000

meters, the temperature remains just a few degrees above freezing and is relatively constant below this level.

Temp Variation with DepthThermocline—layer of ocean

water between about 300 and 1000 meters, where there is a rapid change of temperature with depth.

Temp Variations with DepthThe thermocline is a very

important structure in the ocean since it creates a vertical barrier to many types of life.

Temp Variation with DepthLow Latitude vs High

Latitude

Ocean Density VariationDensity is a property of

matter defined as the mass per unit volume.

Ocean Density VariationDensity is an important

property of ocean water because it determines the water’s vertical position in the ocean.

Ocean Density VariationDensity differences cause

large areas of ocean water to sink or float.

Factors Affecting DensitySeawater density is

influenced by two main factors: salinity and temperature.

Factors Affecting DensityAn increase in salinity adds

dissolved substances and results in an increase in seawater density.

Factors Affecting DensityAn increase in temperature

results in a decrease in seawater density.

Factors Affecting DensityTemperature has the greatest

influence on surface seawater density.

Factors Affecting DensityTemperature vs. density

Density Variation with DepthTemperature and salinity—

and the resulting density—vary with depth.

Density Variation with DepthPynocline is the layer of

ocean water between 300 and 1000 meters where there is a rapid change in density with depth.

Ocean LayeringThe ocean like Earth’s

interior is layered according to density.

Ocean LayeringOceanographers generally

recognize a three-layered structure in most parts of the open ocean.

Ocean LayeringThree layers:• A shallow surface mixed

zone.• A transition zone.• A deep zone.

Surface ZoneSolar energy is received

here, and it is here that the water temperatures are the warmest.

Surface ZoneMixed zone is the area of the

surface created by the mixing of water by waves, currents, and tides.

Surface ZoneUsually extends to about 300

meters.

Transition ZoneBelow the sun-warmed zone

of mixing, the temperature falls abruptly with depth.

Transition ZoneDistinct layer existing

between the warm surface layer above and deep zone of cold water below.

Transition ZoneThis zone includes the

thermocline and the pycnocline.

Deep ZoneBelow the transition zone.Sunlight never reaches this

zone.

Deep ZoneWater temperatures are just

a few degrees above freezing.

Deep ZoneWater density in this zone

remains constant and high.

Ocean LayeringIn high latitudes, the three-

layered structure doesn’t exist.

Ocean LayeringThe three layers do not exist

because there is no rapid change of temperature or density with depth.

Ocean LayeringGood vertical mixing is able

to happen in the high latitudes.

Ocean LayeringCold high-density water

forms at the surface, sinks, and initiates deep-ocean currents.

The Diversity of Ocean LifeA wide variety of organisms

inhabit the marine environment.

The Diversity of Ocean LifeMarine biologists have

identified over 250,000 marine species, and is constantly increasing as new organisms arediscovered.

The Diversity of Ocean LifeMost marine organisms live

within the sunlit surface waters.

The strong sunlight supports photosynthesis for marine algae.

The Diversity of Ocean LifeAlgae either directly or

indirectly provide food for the majority of organisms.

Classification of Marine OrganismsMarine organisms can be

classified according to where they live and how they move.

Classification of Marine OrganismsMarine organisms can be

classified as either plankton (floaters) or nekton (swimmers), and all others are benthos, bottom dwellers.

PlanktonPlankton include all

organisms—algae, animals, and bacteria—that drift with the ocean currents.

PlanktonJust because plankton drift

does not mean they are unable to swim.

Many plankton can swim but either move very weakly or move only vertically.

PlanktonAmong plankton, the algae

that undergo photosynthesis are called phytoplankton.

Animal plankton are called zooplankton.

PlanktonZooplankton include the

larval stages of many marine organisms such as fish, sea stars, lobsters, and crabs.

NektonNekton include all animals

capable of moving independently of the ocean currents, byswimming or othermeans ofpropulsion.

NektonNekton are able to determine

their location in the ocean and in many cases complete long migrations.

NektonNekton include most adult

fish and squid, marine mammals, and marine reptiles.

NektonFish may appear to

exist everywhere in the oceans, but they are more abundant near continents and in colder waters.

NektonSome fish, salmon, swim

upstream in fresh water rivers to spawn.

Many eels do just the opposite, grow to maturity in fresh water and then swimming to breed in the deep ocean.

BenthosThe term benthos describes

organisms living on or in the ocean bottom.

BenthosThe shallow coastal floor,

where most benthos are found, contains a wide variety of physical conditions and nutrient levels.

BenthosShallow coastal areas are the

only locations where marine algae, seaweeds, are found attached to the bottom.

BenthosThroughout most of the

deeper parts of the seafloor, animals live in perpetual darkness, where photosynthesis cannot occur.

BenthosIn these areas the organisms

must survive on each other or whatever nutrients fall from the productive surface waters.

BenthosThe deep-sea bottom is an

environment of coldness, stillness, and darkness.

Under these conditions, life progresses slowly.

BenthosOrganisms that live in the

deep sea usually are widely distributed because physical conditions vary little on the deep-ocean floor.

Marine Life ZonesThe distribution of marine

organisms is affected by the chemistry, physics, and geology of the oceans.

Marine Life ZonesThree factors are used to

divide the ocean into marine life zones: the availability of sunlight, the distance from shore, and the water depth.

Availability of SunlightThe upper part of the ocean

into which sunlight penetrates is called the photic zone.

Availability of SunlightThe clarity of seawater is

affected by many factors, such as the amount of plankton, suspended sediments, and decaying organic particles in the water.

Availability of SunlightThe euphotic zone is the

portion of the photic zone near the surface where light is strong enough for photosynthesis to occur.

Availability of SunlightIn the euphotic zone,

phytoplankton use sunlight to produce food and become the basis of most oceanic food webs.

Availability of SunlightAlthough photosynthesis

cannot occur much below 100 meters, there is enough light for animals to avoid predators, find, food, recognize their species, and locate mates.

Availability of SunlightBelow the photic zone is the

aphotic zone where there is no sunlight.

Distance from ShoreThe area where the land and

ocean meet and overlap is called the intertidal zone.

Distance from ShoreThe intertidal zone, where

the land is alternatively covered and uncovered due to the tides, is a harsh place to live.

Distance from ShoreThe intertidal zone has

crashing waves, periodic drying out, and rapid changes in temperature, salinity, and oxygen concentrations.

Distance from ShoreSeaward from the low-tide

line is the neritic zone.Covers the gently continental

shelf.

Distance from ShoreAlthough the neritic zone

covers only about 5% of the world ocean, it is rich in both biomass and number of species.

Distance from ShoreMany organisms find the

neritic zone ideal.Photosynthesis occurs

readily, nutrients wash in from the land, and the bottom provides shelter and habitat.

Distance from ShoreThe neritic zone is so rich

that it supports 90% of the world’s commercial fisheries.

Distance from ShoreBeyond the continental shelf

is the oceanic zone, where the deep ocean is.

Distance from ShoreThe oceanic zone, due to the

great depths, have lower nutrient concentrations, which results in smaller populations.

Water DepthOpen ocean of any depth is

called the pelagic zone, where animals swim or float freely.

Water DepthThe photic part of the pelagic

zone is home to phytoplankton, zooplankton, and nekton, such as tuna, sea turtles, and dolphin.

Water DepthThe aphotic part of the

pelagic zone has giant squid and other species adapted to life in deep water.

Water DepthThe benthic zone is home to

many benthos, giant kelp, sponges, crabs, sea anemones, sea stars, and marine worms.

Water DepthThe benthic zone includes

any sea-bottom surface regardless of its distance from shore.

Water DepthThe abyssal zone is a

subdivision of the benthic zone.

Includes the deep-ocean floor, such as the abyssal plain.

Water DepthThe abyssal zone is

characterized by extremely high water pressure, consistently low temperatures, no sunlight, and sparse food.

Water DepthSome food, tiny decaying

particles, in the abyssal zone constantly “rains” down.

Other food arrives as whole carcasses of organisms that sink from the surface.

Water DepthSome organisms that are in

the abyssal zone include: filter-feeders, brittle stars, burrowing worms, grenadier, tripodfish, and hagfish.

Hydrothermal VentsAmong the most unusual

seafloor discoveries in the past 30 years, have been the hydrothermal vents.

Hydrothermal VentsAt some vents water

temperature of 100 °C or lower support communities of organisms found nowhere else in the world.

Hydrothermal VentsHundreds of new species

have been discovered surrounding these deep-sea habitats.

Hydrothermal VentsChemicals from the vents

become food for bacteria, which produce sugars and other foods that enable many organisms to live in this environment.

Oceanic ProductivityLike other ecosystems on

Earth, organisms in the marine environment are interconnected through the web of food production and consumption.

Oceanic ProductivityWhy are some regions of the

ocean teeming with life, while others seem barren?

Primary ProductivityThe production of organic

compounds through photosynthesis or chemosynthesis.

ChemosynthesisThe process in which certain

microorganisms create organic molecules from inorganic nutrients using chemical energy.

ChemosynthesisBacteria in hydrothermal vents use hydrogen sulfide as an energy source.Acting as producers, these bacteria support these communities.

PhotosynthesisThe use of light energy to

convert water and carbon dioxide into energy-rich glucose molecules.

PhotosynthesisTwo factors influence a

region’s photosynthetic productivity: the availability of nutrients and the amount of solar radiation, or sunlight.

Primary ProducersMarine producers include

phytoplankton, larger algae such as seaweeds, and bacteria.

Primary ProductivityPrimary producers need nutrients such as nitrogen, phosphorus, and iron.

The most abundant marine life exists where there are ample nutrients and good sunlight.

Primary ProducersOceanic productivity, varies

dramatically because of the uneven distribution of nutrients throughout the photosynthetic zone and the availability of solar energy due to seasonal changes.

Productivity in Polar OceansPolar regions experience

continuous darkness for about three months of winter and continuous illumination for about three months of summer

Productivity in Polar OceansProductivity of phytoplankton peaks during May.During May the sun rises high enough to penetrate deep into the water.

Productivity in Polar OceansAs soon as the phytoplankton develop zooplankton begin feeding on them.The zooplankton biomass peaks in June and continues at a relatively high level until October darkness.

Productivity in Polar OceansDensity and temperature

vary little with depth in the polar regions and mixing occurs between surface and nutrient rich deeper waters.

Productivity in Polar OceansIn the summer, melting ice creates a thin, low salinity layer that does not readily mix with the deeper waters.This lack of mixing helps prevent phytoplankton being carried into the deeper darker waters.

Productivity in Polar OceansBecause of the constant

supply of nutrients rising from deeper waters below, high-latitude surface waters typically have high nutrient concentrations.

Productivity in Polar OceansThe availability of solar

energy is what limits photosynthetic productivity in polar areas.

Productivity in Polar Oceans

Productivity in Tropical OceansProductivity is low in tropical regions of the open ocean.The sun is more directly overhead, so light penetrates deeper, and solar energy is available year-round.

Productivity in Tropical OceansProductivity is low because a

permanent thermocline prevents mixing between surface waters and the nutrient-rich deeper waters.

Productivity in Tropical OceansProductivity in tropical regions is limited by the lack of nutrients.

These areas have so few organisms that they are considered biological deserts.

Temperate OceansProductivity is limited by

available sunlight in polar regions and by nutrient supply in the tropics.

Temperate OceansIn temperate regions, which

are found at mid-latitudes, a combination of these two limiting factors, sunlight and nutrient supply, controls productivity.

Temperate OceansWinter—

productivity very lownutrient concentration

highestsolar energy limiteddepth which photosynthesis can occur is shallow and

phytoplankton do not grow much.

Temperate OceansSpring—

Sun rises higher-greater depth for photosynthesis

Spring bloom of phytoplankton occurs with solar energy and nutrients.

Temperate OceansSpring—

seasonal thermocline develops

traps algae in euphotic zone.

productivity decreases sharply, due to depletion of nutrient source.

Temperate OceansSummer—

Sun rises higher-surface waters continue to warm.

strong seasonal thermocline remains and phytoplankton population remains low.

Temperate OceansFall—

solar radiation decreasesthermocline breaks downnutrients return to the

surfacerise in phytoplankton, but

less dramatic than the spring.

Temperate OceansFall—

rise in phytoplankton is short lived

sunlight becomes the limiting factor as winter approaches

Biomass Productivity

Oceanic Feeding RelationshipsMarine algae, plants, and bacteria-like organisms are the main oceanic producers.As producers make food available to the consumers, energy is passed from one population to the next.

Oceanic Feeding RelationshipsEnergy is “consumed” or

“lost” at each level, so only a small percentage of the energy taken in at any level is passed on to the next level.

Oceanic Feeding RelationshipsThe producer’s biomass in

the ocean is many times greater than the mass of the top consumers, such as sharks and whales.

Trophic LevelsChemical energy stored in

the mass of the ocean’s algae is transferred through feeding.

Trophic LevelsZooplankton are herbivores, so they eat algae.The herbivores are then eaten by carnivores.Smaller carnivores are eaten by another population of larger carnivores.

Trophic LevelsEach of the feeding stages is

called a trophic level.

Transfer EfficiencyThe transfer of energy between trophic levels is very inefficient.

The efficiencies of different algal species vary, but the average is only 2%.

Transfer EfficiencyOnly 2 percent of the light

energy absorbed by algae is ultimately changed into food and made available to herbivores.

Transfer Efficiency

Food Chains and Food WebsA food chain is a sequence of

organisms through which energy is transferred.

Food Chains and Food WebsFood webs are all the feeding

relationships between producers and the top consumers.

Food Chains and Food WebsA herbivore eats the

producer, then one or more carnivore eats the herbivore. And finally the top carnivore eats the carnivore below it.

Food Chains and Food WebsAnimals that feed through a

food web rather than a food chain are more likely to survive because they have alternative foods to eat should one of their food sources diminish or disappear.

Food Chains and Food Webs