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What is the tidal range of Gulf of Mexico and why?
low tidal range: 2ft due to Wind effect
Between highest tide level and lowest
Distance between highest and lowest tide levels
What have the most extreme tidal range; give example
long, narrow bays have most extreme tidal range ex East Canada- Bay of Fundy-25ft tidal range
list high and low tides etc
what tide is desired for field trips? launching boat/scuba?
- Field trip-low tide
- Boat/scuba-high tide
Tides are measured from the ?
What is the zero mark?
Its set by observation-they keep record of highest and lowest tide for year; avg measurement=> ?
What is the intertidal zone?
Area with tidal effects
What is the subtidal area?
Area below intertidal to deepest wave effects
Why do we have tides?
- earth rotates around sun, moon rotates around earth; Moon pulls at water on earth on same side of it=>high tide
- Opposite side of earth has low tide
What is spring tide? What causes it?
- When tide seems to "spring" up: Higher highs and lower lows
- Occurs was EATH->moon-> sun in that order=>higher tidal range
What is neap tide? Cause?
- Lesser tidal range
- Occurs when sun and mood are perpendicular
Why may tides table be off by couple hours?
Gradually move as earth rotates
Diurnal tides; where do they occur?
- 1 high and 1 low tide per day
- 2 highs and 2 lows per day at 6 hour interval
- Pacific coast of USA
- Higher High(HHT) 6ft
- Lower low (LLT) -2ft
- Lower high(LHT) 4ft
- Higher low(HLT) 2ft
- Waves of tidal flow tends to raise water level on 1 side of basin
- Occurs in semi enclosed areas
- Ex Gulf of Mexico
Physiological challenge on marine life at low tide
- Respiration-low water levels or water retreats
- Desiccation: drying out
- Exposure to wind and rain
- Exposure to land-based predators: birds are major danger, mammals(coyotes/racoons)
- Trampling &crushing and sand compaction
- When little rain=> higher salt=> when dry out -salt formation= BAD
- Especially at extreme high tide
Challenges at high tide: COMPETITION
- Surf-wave banging on tiny organisms can crush or rip away from perch
- Cope by hide, rubbery body, flexible; hang on tight
- Sand abrasion-act like sand paper
- Exposure to Sea water predators-fishes, morays, crabs, octuopus, starfishes
- Ex baracuda into shallow water in search of food
How to cope w/ low life
- Leave-fish will swim offshore or go into deeper pools
- Dig in-burrow into sediment
- Cause problems b/c less oxygen
- Store water
- Stay in a shady place
- Body color: light ,pale or camouflaged
- Helps against predators and heat
- Seasonal cycles
- Some species are strictly intertidal
- Ghost crab: ocypode-only live in intertidal b/c they can't compete
- Can be refuges
- Rock jetties with overhang
- May form microhabitats
- At low tide may go under and will see things only seen when diving normally
- Can also have BAD microhabitats-hypersaline, or dead, rotted seaweed or human caused
Effects of Sea Spray at very highest levels
- Moisture and salt-causes problems with rooted plant
- Salt gets on leaves=>desiccation of leaves
- Some things can handle that
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