Marine Shores:Life Between the Tides

Toni Christopher

Overview

• Geography• Structure• Physical Conditions• Chemical Conditions• Biology• Human Influences

Geography

• Intertidal Zones– Area covered and uncovered by the

tides– Tide pools, salt spray, and sweet

smelling kelp• Thousands of kilometers(.6

miles/km) worth worldwide• Can be either exposed(rocky) or

sheltered(sandy/muddy) shores

Structure

Physical Conditions:Light and Temperature

• Light– Varies with the tide

• High tide, water turbulence = less light• Low tide = full sun

• Temperature– Every changing; varies with tide and location

• Low tide= below freezing at high latitudes when exposed to air; above 40C(104F) in tropics and subtropics

• High tide = temperature is that of water, 17C(62.6F)

Physical Conditions: Water Movement: Tides and Waves

• Tides– Vary in strength and frequency

• Semidiurnal or diurnal• Can vary from few cm to 15m in Canada’s Bay of

Fundy– Affected by alignment of both sun and moon

• At full and new moons, sun, moon, and Earth align; stronger tides; called Spring

• At ¼ and ¾ moons, sun and moon at right angle, opposing one another; weakest tides; called Neap

• Size and location of bay, sea, coastline, etc determine if sun and moon effect amplified or dampened

• Waves– Vary greatly from area to area; affect

distribution of life• Headlands vs. Coves and Bays

Chemical Conditions:Salinity and Oxygen

• Salinity– Varies more on the shores than in the

oceans• Desert shores: higher from evaporation• Rainy shores and tropics in wet season: much

lower

• Oxygen– Amount typically not a limitation factor

• Species exposed to air at low tides• Water is mixed and well oxygenated

– Exceptions are sandy/muddy shores of sheltered bays, etc that don’t have good water circulation

Biology

• Life adapted to a marine/terrestrial existence– Covered and uncovered by tides

periodically

• Zonation of species– Species live where best adapted

• Habitats include tide pools, the different zones, salty streams, sandy/muddy shores, and rocky shores

Human Influence

• Some species devastated by humans–Mussels, oysters, clams, etc

• Exploitation for food, education, and research

• Oil spills pollute and ruin habitats• Introduction of non-native species on

bottoms of ship hulls

Resources

• Molles, Manuel C Jr. Ecology, Concepts and Applications. Fifth Ed., 2010.

• http://studentweb.cortland.edu/knowles86/Intertidalzone.gif

• http://www.clarku.edu/departments/biology/biol201/2002/JLagliva/Organisms.html

• Google Images