Chapter 12 The Marine HabitatEssentials of Oceanography 7th Edition

The diversity of marine lifeThe ocean is home to a wide variety of organismsMarine organisms range from microscopic bacteria and algae to the largest animal in the world (blue whale)Number of known marine species: 250,000

Classification of living thingsOrganisms can be classified into one of three domains of life:ArchaeaBacteriaEukaryaFigure 12-1

Classification of living thingsOrganisms can also be classified into one of five kingdoms:MoneraProtoctistaFungiPlantaeAnimaliaFigure 12-1

Classification of living thingsTaxonomic classification includes the following increasingly specific groupings:KingdomPhylum (Division for plants)ClassOrderFamilyGenusSpecies

Taxonomic classification of selected organisms

CategoryHumanKiller whaleGiant kelpKingdomAnimaliaAnimaliaProtoctistaPhylumChordataChordataPhaeophyta Subphylum Vertebrata VertebrataClassMammaliaMammaliaPhaeophycaeOrderPrimatesCetaceaLaminarialesFamilyHominidaeDelphinidaeLessoniaceaeGenusHomoOrcinusMacrocystisSpeciessapiensorca pyrifera

Classification of marine organismsMarine organisms can be classified into one of three groups based on habitat and mobility:Plankton (floaters)Phytoplankton (drifting plants and algae)Zooplankton (drifting animals)Nekton (swimmers)Benthos (bottom dwellers)

Plankton: ExamplesFigure 12-2PhytoplanktonZooplankton

Nekton: ExamplesFigure 12-4

Benthos: ExamplesFigure 12-5

Life cycle of a squidSquid experience benthic, planktonic, and nektonic stagesSquid are considered meroplankton (opposite = holoplankton) Figure 12-3

Distribution of species on EarthThe land has more species because it has greater environmental variability than the oceanMost ocean species are benthic because of greater environmental variability compared to pelagic environmentsFigure 12-6

Adaptations of organisms to the marine environmentThe marine environment presents many challenges to organisms because seawater:Is dense enough to support organismsHas high viscosityExperiences variations in temperature and salinityContains variable amounts of dissolved gasesHas high transparencyHas a dramatic change of pressure with depthMarine organisms have various adaptations for the conditions of the marine environment

Need for physical supportCondition:Seawater is dense enough to support marine organismsAdaptations:Many marine organisms lack rigid skeletons, appendages, or vast root systemsInstead, they rely on buoyancy and friction to maintain their position within the water column

Seawaters viscosity controlled by temperatureCondition:Seawaters viscosity (resistance to flow) is strongly affected by temperatureCold water has higher viscosity than warm water, so is more difficult to swim throughWarm water has lower viscosity, so organisms tend to sink within the water column

Seawaters viscosity controlled by temperatureAdaptations:Many warm-water organisms have ornate appendages to say afloatMany cold-water organisms are streamlined to swim more easilyFigure 12-7Warm-water copepodCold-water copepod

Seawaters viscosity and adaptations of phytoplanktonCondition:Phytoplankton must remain in sunlit surface watersAdaptations:Small size increases surface area to volume ratioAppendages increase frictional resistanceTiny droplet of low density oil increases buoyancyFigure 12-8

Variations in temperatureCondition:Coastal water temperatures vary more than the open ocean or at depthAdaptations:Many coastal organisms can withstand a wide temperature range (are eurythermal)Most open ocean and deep-water organisms can withstand only a small temperature range (are stenothermal)

Variations in salinityCondition:Coastal environments experience greater salinity variation than the open ocean or at depthAdaptations:Many shallow-water coastal organisms can withstand a wide salinity range (are euryhaline)Most open ocean and deep-water organisms can withstand only a small change in salinity (are stenohaline)

OsmosisCondition:Osmosis is the movement of water molecules through a semipermeable membrane from higher to lower concentrationsOsmosis removes water from hypotonic organismsOsmosis adds water to hypertonic organismsFigure 12-13

OsmosisAdaptations:Figure 12-14

Dissolved gases: OxygenCondition:Marine animals need oxygen to surviveAdaptations:Many marine animals use gills to extract dissolved oxygen from seawaterMarine mammals must breathe air Figure 12-15

Abundance of dissolved oxygen and nutrients with depthFigure 12-20

Seawaters high transparencyCondition:Seawater has high transparencyAdaptations:TransparencyCamouflageCountershadingMigration (DSL)Figure 12-17CamouflageCountershading

The deep scattering layer (DSL)Organisms within the deep scattering layer undertake a daily migration to hide in deep, darker waters during daytimeFigure 12B

Increase of pressure with depthCondition:Pressure increases rapidly with depthAdaptations:Most marine organisms lack large compressible air pockets inside their bodiesWater-filled bodies exert the same amount of pressure as is pushing inward, so marine organisms do not feel the high pressure at depth

Divisions of the marine environmentMain divisions:Pelagic (open sea)Benthic (sea bottom)Figure 12-19

End of Chapter 12Essentials of Oceanography 7th Edition