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Gulf of Mexico:
exposed sandy beach->barrier island->bay->mudflats, salt marsh->mainland
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Waves
- result of winds blowing across surface of ocean
- Smaller scale than tide
- Size depends on strength of wind
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Fetch
- Distance wind blows
- Longer=higher waves
- Worst winds around Antartica
- Texas doesn't get the high wind or the fetch=> don't get big waves
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Wave can what with each other
Augment or cancel each other
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Swell
- Mostion of waves
- Will move up and down; doesn’t have Break
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Waves break when?
- when wave height /wave length =1/7
- Break at 10000lbs/square inch
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Period
seconds for crest to travel 1 wave length
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HOW TO GUESS WAVE HEIGHT
- Eye level=wave height
- Better think about it
- Look at where wet seaweed is in relation to you
- If high up, then shouldn't enter water
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Shallow water wave:
depth=1/2 wave length
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Surge
Back and forth wave motion in shallow water
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Breakers
Can be spilling or plunging
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Spilling breaker
Wave curls over and doesn’t break immediately, but curves over long line (water tunnel)-surfers use
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Plunging breaker
- comes up on a steep beach
- Just goes splat
- Doesn't feel bottom until already on beach
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Wave breaks
- In TX and most of gulf coast; waves break in series over sandbars
- Some troughs can be 5 ft deep
- So rule of thumb-don't go more than knee deep
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Once Waves finally run up on beach then?
Water can sink into sand and go back to sea Or backwash
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backwash
- water runs back to sea
- 1 inch isn't big deal-strong backwash can knock you off your feet
- Hissing noise indicates strong backwash
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Longshore currents
- Run along beach, carry water to RIP channels-go 900 to beach out to sea
- Usually weak
- Fish sit in rip channel b/c if something gets knocked off beach, it gets into rip channel
- Looks calm-interruption in waves then with foam
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Primary Productivity of sandy beach
- Phytoplankton present
- No attached algae, seagrasses etc
- Animals rely on debris, dead stuff or predation for food
- Lots of dead sargassum
- Affected by surf-scraping, movement
- Sand grain size important what causes sand to be more coarse
- stronger surf=> ?
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Wentworth scale:
- silt (less than 1mm) on upp
- Primarily medium sand in TX
- Most animals prefer medium and thin sand
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Coarse sand doesn't have much fauna b/c ?
they have to deal with wave action
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Coarse sand characteristics
- Wave action LOTS=> lots of O2 and stuff cast ashore,
- BUT sand doesn’t retain water at low tide; much abrasion
- Greater porosity
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FINE SAND characteristics
- Less wave action
- Retains better water at low tide
- Also allows decomposition of particles in it=>can be stagnant
- Allows burrow formation-sticks to itself
- Low porosity b/c sandgrains essentially glued together by silt
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POROSITY-
amount of space between sand grains
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Thixotrophy-
- ability of sand to hold water under certain amount of pressure
- Causes water puddle in footprint
- Makes burrows b/c can put water about themselves
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BEACH (farthest-closest to water) topography
Sand dune; backshore; berm(dry beach); front beach; bars and troughs
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Sand dune characteritics
- Affected by salt spray
- Anything lives there will get salt on it
- Little fresh water, scant soil
- Plants have deep roots or spread out across sand by runners
- Can excrete salt or have hairs, to catch salt
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Sand dune flora
- Sea oats-deep
- Beach morning glory
- Runners
- Beach tea-hairs
- Location varies by season
- Insects, lizards, ground squirrels also live there
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Backshore
Zone of driftwood and storm debris
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Berm(dry beach): ghost crabs and small beetles
- Ghost crabs eat just about anything
- Can even burrow down deep
- Move FAST 6ft/sec.
- Even baby sea turtle
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Front beach
- Beach face
- Intertidal
- Palp worms, amphipods, mole crabs(Emerita); clam(Donax)
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Bars and troughs
- Ghost shrimp, small fishes, speckled crab (Arenaeus), sand dollars (Mellita) and sea pansy
- Some starfishes in surf zone
- Eating habits of BEACH BIRDS
- Usually 3rd level consumers
- So common, they are the major 3rd level consumer on beach ecosystem
- Help w/ TX economy-rare bird
- Eating small fish, crabs etc
- At low tide; birds are most likely the predators that need to be considered
- If ignore, you will only have a small picture of what is going on
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GULLS
- Scavengers;Live along just about any big body of water-Move inshore if big storm
- Strong bill
- Eat just about anything-fritos; chips; baby sea turtle; small fish/crabs; anything fisherman catches
- Rounded wings]
- Found on open and closed beaches
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LAUGHING GULL
- Most common in TX
- Characteristic cry
- Black heads in summer And white heads with black dot in winter
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TERNS
- Sharp wings
- Forked tail
- Dive for fish
- Very adroit fliers
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SAND PIPER family
- Shore birds
- Pecking at things in the sand
- Feeding on polyket worms, SMALL clams etc
- Lot of members; extremely difficult to tell apart
- Make peep noise
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SANDERLING-
- Type of sandpiper
- found at low tide level, hunts among the incoming water
- White; Very common-cute
- Found on open beach
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Plover
- Small bill, but Larger than sandpiper
- Short bill
- Feed on small invertebrates
- Very good fliers: Doesn’t glide/hover
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Willet
- Wading bird or on beach, long legs, gray, wings black and white
- Make lot of noiseMake big racket if disturbed
- Eat very small crab
- Have long bill
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SANDY BEACHES
- more surf vs less surf
- more surf less surf
- grain size larger Grain size smaller (more silt)
- Greater porosity Less-more compact sediment
- More O2 in sediment Less except at surface
- More abrasion No abrasion
- Difficult to create burrows Burrowing is easy, burrows last for long time
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Stratification occurs in sediment-describe layers
- MAINLY OCCURS IN LESS surf b/c more surf=> mixing and oxygenization of sand
- Water
- Oxygenated-"GRAY" sand
- No/low free O2-"BLACK" sand
- Full of bacteria-anaerobic
- Decomposition occurs
- H2SO4
- Animals -are low and slow and only if able to survive ACIDIC and anaerobic environment
- REDOX layer: between gray and black layer
- Very distinct; often red
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PROTECTED SANDY BEACHES characteristics
- No surf b/c On bay sides of barrier islands
- Sandy: wind blows sand into bay
- Very flat =>Wide tidal range
- HARSH environment
- Hot and dry @ low tide
- Can be soaked by rain-problems b/c marine orgs. Will have hard time with fresh water
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Fauna of protected sandy beaches
- Animals tend to move up and down; in and out
- Primary production from phytoplankton
- Sometimes also benthic microalgae
- BENTHIC=ON BOTTOM or ON SEA FLOOR
- Many small animals rely on detritus for food
- Detritus= decaying organic matter with a coat of bacteria (protein)
- DETRITAL BASED FOOD CHAIN IS IMPORTANT
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Microtopography of protected sandy beaches
- Small -scale features of sediment
- Burrows, ripple marks, crab tracks etc
- Get many extremely tiny animals-Microfauna; 1mm or less
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Interstitial fauna
- Microfauna that live between and on sand grains
- Small enough to sit on individual sand grain
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Epibenthic animals
- -live on top of surface
- Juvenile blue crab, moon snail, lightning whelk, striped hermit crab
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Juvinile blue crab(allinectes sapidus)
- Good nervous sytem and eye sight
- HATE everyone
- Can dig into sand so that only eyes, respiratory and anntenae
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Moon snail POLINICES
- Eats clams-drills through shell with its mouth then eats it out
- Drills through sand
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Lightning Whelk
- 1 shell gastropod
- Busycotypus
- Scavenger and eats clams
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Striped hermit crab
- As it gets bigger, moves from shell to shell
- Can't live on land
- Stores water in its shell so can survive at low tide for a couple hours
- Not ones in pet store
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Fauna In water near sandy beaches
- Shrimp farfantepenaeus
- Commercial shrimp
- Feed on organisms in sand=>
- Fishes: red fish and croakers
- Mouth on bottom
- Come in at high tide and munch on all the smallers
- Flat fish and stingray-do the shuffle
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Infauna:
- lives buried in sand=> hard to see
- hard clam, small clams, polychaets worms; lug worms
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Hard clam: Mercenaria
- Early naturalists got the shells at the same time enligh were trading with native americans
- Good to eat, but most we see will be from poluted areas=> bad to eat
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Lug worm-polychaete worm(segmented)
- Feeds by swalloing sand/silt/mud
- Digests whats edible(bacteria) then voids the rest
- Direct deposit feeding
- Leaves fecal castings
- What comes out is primarily sand with little fecal mater
- Valuable ecological service
- Oxygenate sediment by moving it around
- Have internal fertilization
- Eggs are left in jelly coat before hatch out as larval stage
- Egg sack Attached to mud by stalk "SNOT BALL"
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Sandy beach DEEP BURROWERS
- Clams-Have neck to reach organism from surface
- Record=5 ft
- Dig in while juvenile, but if pulled back out, can't reburrow
- Below redox level
- GAPER clams: Tresus
- Neck have fused in current and excurrent siphons
- Burrow works as exoskelton
- See whole or something
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