The Marine Realm

Chapter 4 

Environments 

and Life

What is your current classification? 

A. Freshman 

B. Sophomore 

C. Junior 

D. Senior

Guiding Questions 

• What factors determine the ecological 

niches of species, and by what means do 

species obtain nutrition? 

• What factors govern the geographic 

distribution of species? 

• What factors govern the distribution of 

aquatic life?

Environmental Differences 

• Tropical vs Polar - Terrestrial and Marine 

• Low vs High Elevation 

• Shallow vs Deep 

• Wet vs Dry

Hypsometric Curve 

• Curve showing the proportions of the 

Earth’s surface above and below sea level

Hypsometric Curve

Climate 

• Climate 

– Controls distribution of species globally 

– Has changed through time 

• Plate tectonics and other changes affect 

climate

Ecology 

• Ecology 

– Study of the factors that govern the distribution and 

abundance of organisms in natural environments 

• Habitats 

– Environments on or close to Earth’s surface inhabited 

by life 

• Terrestrial 

• Aquatic 

– Marine 

– Freshwater

Ecology 

• Ecologic niche 

– The way a species relates to its environment, including food, 

nutrients, physical and chemical conditions 

• Life habit 

– The way a species lives within its niche 

• Limiting factors 

– Naturally occurring, restricting condition (physical and chemical) 

– Competition 

• Shared drive for limited resources 

– Predation

Competition 

Arises because organisms share space 

Predation also comes in here by 

possibly limiting or preventing another 

species from inhabiting a particular 

environment.

Ecosystem 

• Ecosystem 

– Organisms of a community and the physical 

environment they occupy 

• Population 

– Group of individuals that belong to a single 

species and live together in a particular area

Ecosystem 

• Ecologic community 

– Populations of several species living in a habitat 

• Producers 

– Photosynthesizing organisms; foundation of community 

• Consumers 

– Herbivores: feed on producers 

– Carnivores: feed on other consumers

• Biota 

Ecosystem 

– Fauna: animals and protozoans of an ecosystem 

– Flora: plants and plantlike protists 

• Food chain 

– Sequence of consumption for producers to consumers

Food Web 

• Food web 

– More complex than simple food chain 

• More common 

– Several species occupy each level

Ecosystem 

• Parasites 

– Feed on living 

organisms 

• Scavengers 

– Feed on organisms 

that are already dead

Ecology 

The movement of materials through an ecosystem. 

Components within ovals are consumers.

Figure 4-35 

(p. 134) 

Interdependence 

of photosynthesis 

and respiration.

Figure 4-38 (p. 136) 

Simple pyramid of ocean life.

Biogeography 

The distribution and abundance of 

organisms on a broad geographic 

scale.

Biogeography 

• Temperature 

• Moisture 

• Nutrients

• Diversity 

Ecosystem 

– The variety of species that live together within a 

community 

• Lower in more difficult habitats 

• Predation influences diversity 

– Heavy can reduce diversity 

– Moderate can increase diversity by reducing competition 

• Opportunistic species 

– Species that specialize in invading newly vacated 

habitats

Biogeography 

• Distribution and 

abundance of 

organisms on a broad 

geographic scale 

• Limiting factors 

– Diversity increases 

toward equator 

– Barriers can affect 

dispersal

Life Habitats 

The mode by which an organism lives, feeds 

in an environment 

1. Tropical vs. Polar 

2. Low vs high altitude 

3. Shallow vs deep 

4. Benthic vs. Planktonic

Atmosphere 

• Regulates Earth’s 

temperature (-18°C w/o 

atmosphere) 

• Composition 

– N 2 , O 2 , CO 2 

• Tilt of the Earth affects 

solar insulation, 

temperature, and climate

In our present atmosphere, 

concentrations of O 2 and CO 2 are: 

A. O 2 > CO 2 

B. O 2 < CO 2 

C. O 2 = CO 2

The Atmosphere 

• Nitrogen -78% 

• Oxygen - 21% 

• Carbon dioxide (CO 2 ) - 0.037% or 370 ppm 

• Methane (CH 4 ) - 0.00018% or 1800 ppb

Solar Radiation 

Daylight 

Which receives more hours of daylight? 

Equator vs Poles 

The amount of daylight (# of hours) averaged 

over a year is the same at the poles as at the 

equator

Solar 

Radiation


• Temperature difference is due to the angle 

of the sunlight and the albedo 

• In the high latitudes, the sun hits at a low 

angle and therefore the unit energy of 

sunlight is spread over a large crosssectional 

area of the earth’s surface. In the 

tropics, the sun hits directly and therefore is 

much more concentrated

Solar Radiation


Albedo refers to the 

reflectivity of the Earth’s 

surface 

1. Snow and ice is very 

reflective - much of the 

solar radiation is reflected 

by to the solar system 

2. Water has a low albedo and 

absorbs a lot of the solar 

radiation

Solar Radiation

Solar Radiation


• When do we have summers? 

• True or False 

• Summers on Earth occur when it passes 

closest to the Sun


• Obliquity or Tilt (23.5°) of the to Earth’s 

rotational axis 

• This tilt gives us seasons. Summer is when 

the northern or southern hemisphere is 

point towards the Sun

• Regulates Earth’s 

temperature 

• Composition 

– N 2 , O 2 , CO 2 

• Tilt of the Earth 

affects solar 

insulation, 

temperature, and 

climate 

Atmosphere


Heat Capacity

Movement of Air mass 

• Rises at Eq. and sinks near Poles 

• The high solar radiation at the equator heats 

the air masses, causing them to rise 

(buoyant). 

• As the air rises, the temperature of the air 

mass decreases

Atmospheric Circulation 

• Net transport 

– Air sinks at the poles, 

rises at the equator 

– Simplified model 

• No tilt 

• No Coriolis effect

Rising Air 

As the air rises, the temperature of the air mass 

decreases (adiabatic lapse rate 5°C/km) 

Cold air holds less water vapor. Voila, rain and the 

tropical rainforest. Low pressure systems 

usually have rain because the rising air drop 

water as the air ascends and cools

Rising Air


• Coriolis effect 

• Earth’s rotation 

causes air and water 

masses to be defected 

to the right 

(clockwise) in the 

northern hemisphere 

– Counterclockwise for 

southern hemisphere


• If we reverse the direction 

and launch a rocket from 

Panama towards 

Washington DC, which 

way will it curve? 

• A = Right 

• B = Left 

• C = Not at all because 

Panama is close to the Eq.

Coriolis force 

• Deflection of moving objects to the right in 

the No. Hemisphere and left in the So. 

Hemisphere

Coriolis 

Force


• Actual pattern is more 

complex 

– Three circulation cells 

– Trade winds, westerlies, 

easterlies 

• Intertropical convergence 

zone 

– Northern, southern trade 

winds converge near 

equator 

• Changes seasonally

Temperature Variations 

• Atmosphere retains 

heat 

• Solar radiation 

– Absorbed and turned 

into heat energy 

– Reflected 

• 6-10% ocean 

• 5-30% forest 

• 45-95% ice and snow

• As the dry air 

descending 

around 30° 

begins to 

flow back 

towards the 

Eq. it is 

deflected to 

the right. 

Trade winds

Trade winds 

As the dry air descending around 30° begins to flow back 

towards the Eq. it is deflected to the right.

Trade winds 

The NE and SE trades converge on the 

latitude where the maximum in 

convection (rising air) is occurring. 

This is the warmest location. Today, 

this is between 4 and 10°N and is 

termed the Inter-Tropical 

Convergence Zone (ITCZ)

The Terrestrial Realm 

• Latitudinal Zones and Vegetation 

• Rain forests 

• Deserts 

• Savannah Grasslands 

• Temperate Forest 

• Conifer or Evergreen Forest 

• Tundra

Terrestrial Realm 

• Vegetation follows 

climatic zone 

– Tropical rain forest 

– Desert savannahs 

– Temperate forests 

– Polar tundra


• Tropical Climates 

– 18–20° C (64–68° F) 

– 0–30° latitude 

• Tropical Rain Forest 

– Dense vegetation

Rain forests 

• develop under the 

tropical low 

pressure systems. 

Rising air dumps 

lots of rain. Found 

within a few 

degrees near the 

equator


• Deserts 

– Dry trade winds 

remove moisture 

– 20–30° north and 

south of the equator 

– < 25 cm rain/year 

– Little vegetation 

• Savannah, grasslands 

– Too dry to support 

forests

• (

Savannah Grasslands 

• found between Rain forest 

and Desert and receive 

seasonal rain falls. Not 

enough rain throughout the 

year to support woodland

Tundra 

- Arctic ecosystem where 

layer beneath soil remains 

frozen throughout the year.


• Poles 

– Defined by ice sheets 

and glaciers today 

– Absent or reduced at 

times in the past


• Glaciers 

– Ice in motion 

– Glide and spread 

– Present at high 

latitudes and high 

elevations near equator


• Tundra 

– Limited water 

– Grasses, sedges, lichens, 

shrubs dominate 

– Cannot support tall trees 

• Evergreen coniferous 

forests 

– South of tundra 

– Spruce, pine, fir


• Temperate forests 

– Longer summers, slightly warmer 

– Deciduous trees 

• Maples, oaks, beeches 

• Mediterranean climate 

– Dry summers, wet winters 

– Common 40° N and S of equator 

• Californian, Mediterranean region

Climate 

• Altitude 

– Similar to latitudinal 

gradient 

– At base 

• Deciduous forest 

– On slopes 

• Evergreen forest 

• Tundra above tree-line 

– At top 

• Glaciers

Climate 

• Mountains 

• Rain shadow 

– Prevailing winds bring 

moisture 

• Precipitation on 

windward side 

• Aridity on leeward side 

– Rain shadows common 

on east side of North 

American mountain 

chains

Climate 

• Seasonal Change 

– High heat capacity of 

water 

• Less change in ocean 

temperatures than on 

land 

• Monsoon Circulation 

– Summer winds flow 

onshore; bring rain 

– Winter winds offshore

Plants as Climate Indicators 

• Sensitive indicators of 

change 

– Cycads 

• Tropics and subtropics 

today 

• Fossil distribution 

allows reconstruction 

of climate patterns

Plants as Climate Indicators 

• Leaf Margins 

– Tropics 

• Smooth, waxy margins 

– Temperate climates 

• Jagged margins

• Ocean currents 

– Wind driven 

– Follow atmospheric patterns 

• Trade winds 

– Push waters west; form 

equatorial currents 

– Equatorial countercurrents 

• Return flow 

• Gyres 

– Clockwise in Northern 

Hemisphere 

– Gulf Stream 

Marine Realm

Marine Realm 

• Circumpolar current 

– Circles Antarctica 

– Very cold


• Polar circulation 

– Sea ice leads to more 

saline water 

– Cold, dense waters 

sink 

– Antarctic waters 

• Flow north at depth 

– Arctic waters 

• Flow south at depth


• Ocean circulation 

– Waves 

• Surface waves 

– Wind driven 

– Break when seafloor interacts at shallow depths 

– Tides 

• Cause major movement of water in oceans 

• Due to rotation of solid Earth beneath bulges of 

water produced by gravitational attraction of the 

moon


• Continental Shelf 

– Submarine extension of 

continental landmass 

• Shelf break 

– Edge of shelf 

• ~200 m w.d. 

• Continental Slope 

• Continental Rise 

• Abyssal Plain

Figure 4-31 (p. 131) 

Classification of marine environments. 

(After Hedgspeth, UJ. W., ed. 1957. Treatise of Marine Ecology and Paleoecology. Geological Society 

of America Memoirs 67(1): 18.)

The Marine Realm 

• The depth of the Sea 

• Moving from the beach seaward, one crosses a 

consistent pattern of water depth changes. The 

continental shelf extends from the shoreline to 

the continental shelf break. Water depths over 

the shelf vary from 0 to ~200 m. This 

environment is very important for benthic 

communities because the photic zone in the 

ocean extends only down to 200m. Consider the 

implications for primary production


• The Shelf break marks the distal edge of 

the shelf where seaward of this point, water 

depths increase at a greater rate (3 to 

5°slope) compared with the shelf (1 to 

2°slope).


• Continental Slope. 

• Typically, the slope extends down to 3000 

to 3500 m. Near the base of the slope is the 

transition from continental to oceanic crust.


• The Slope gives way to the Continental 

Rise. This is a less steep surface that 

segways to the Abyssal Plain (the ocean 

floor). The Rise is created as sediments are 

transported down the slope in turbidity 

currents.


• At the base of the slope and out on the 

abyssal plain, the slope decreases 

significantly and the sediments are 

dropped, forming the Rise

Figure 4-31 (p. 131) 

Classification of marine environments. 

(After Hedgspeth, UJ. W., ed. 1957. Treatise of Marine Ecology and Paleoecology. Geological Society 

of America Memoirs 67(1): 18.)


• Near shore 

– Barrier islands 

– Marshes 

– Epicontinental seas

• Photic Zone 

– Region of ocean where 

enough light penetrates to 

permit photosynthesis 

• Pelagic life 

– Plankton 

• Phytoplankton 

• Zooplankton 

– Nekton 

• Benthic life 

– Suspension feeders 

– Deposit feeders 

Marine Realm


• Marine Biogeography 

– Tropical 

– Subtropical 

– Transitional 

– Subarctic

Figure 4-36 (p. 135) 

Major ocean surface currents.


• Corals 

– Most require warm water 

– Common in tropics 

• Reef builders 

– Coral polyp 

– Builds coral cup 

– Connected to other polyps 

• Symbiotic relationship 

with algae

• Salinity 


– Limiting factor near shore 

– Oceanic 

• 35 ppt 

– Brackish 

• Lower than marine 

• Bays, lagoons 

– Hypersaline 

• Higher than marine 

• Hot arid climates

The portion of the temperature-depth curve in the 

ocean that shows maximum change is the thermocline.

Deep Water Circulation


• If we reverse the direction 

and launch a rocket from 

Panama towards 

Washington DC, which 

way will it curve? 

• A = Right 

• B = Left 

• C = Not at all because 

Panama is close to the Eq.

The Marine Realm

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