Transcript Coastal Seas

Coastal Seas
 A Coastal Sea is the part of the world ocean that
covers the continental shelf.
 Continental shelves extend variable distances
from continents and typically gradually descend to
140 m (460ft) before dropping off as the
continental slope.
Continental Shelves
Coastal Sea
Light Penetration
 Epipelagic / Euphotic Zone = The zone of
the oceans to 200 m with enough light to
sustain photosynthesis.
 Almost all of all continental shelves is within
the euphotic zone.
 However, almost all photosynthesis occurs in
the top 30 m and turbidity can reduce that.
 The benthic zone of continental shelves away
from shore is still pretty dark and rarely
supports any but the most minimal
photosynthesis.
Tides
 Tides = Periodic movement of the sea due to the
gravitational effects of the sun and the moon on the
world ocean (High and low tides ~ twice a day.)
 Spring Tides – are tides with the largest tidal
range (greatest range of tides = every 14 days)
 Neap Tides – are tides with the lowest tidal range
(least range of tides = every 14 days)
Tides
Tidal Range
Coastal Sea: “The Littoral”
 Littoral zone = ?
(Different for lakes.)
-area affected by the ocean to ~ 60 m deep
-splash zone to deepest area affected by wave energy
-covered and uncovered by tides (Eulittoral)
 Surf zone = area above where wave energy
affects the bottom and waves begin to break.
The “Littoral” Substrate
 Hard substate = rock outcrops, large
boulders, and/or rocks not moved by
wave or tidal action. = VERY small part
of littoral
 “Soft” substate = particles (from
microscopic silt to rocks) moved by wave
or tidal action. = most of the littoral
-mud, sand, gravel (beaches & mud flats)
-well sorted = particles mostly same size
(particles move easily)
-poorly sorted = particles vary in size
(particles move less easily)
Coastal Sea: Neritic Zone
 Neritic zone = from the lowest level NOT
uncovered by the tides to the edge of the
continental shelf
-Neritic pelagic
-Neritic benthic – continental shelf sea floor
The Neritic Substrate
 Almost all of the substrate of the neritic zone
is soft due to sediment from the water column
and little or no wave action effects.
Stream/Runoff Contributions
Coastal Upwelling
Oceanic Primary Production
Coastal Primary Production
 Macrophytes = near shore; green, brown,
and red algae
In general, surface to deeper
brown-to-green-to-red
(This is very rough and all are found shallowly
and deeply.)
 Periphyton = near shore; mostly green algae,
diatoms, and cyanobacteria
 Phytoplankton = euphotic zone; mostly
green algae, diatoms, dinoflagellates,
cocclithophores, and cyanobacteria
“Littoral” Zone Food Web
periphyton &
macrophytes
phytoplankton
& zooplankton
(mostly “washed in”)
grazers
planktivores
fishes, mollusks,
crustaceans
fishes, mollusks,
crustaceans, echinoderms,
cnidarians
particulate organic
matter (POM)
(from a range of sources)
bacteria
deposit feeders
(soft substrates)
“predatory”
fishes, mollusks,
crustaceans, echinoderms
fishes, mollusks,
crustaceans, echinoderms
Euphotic Neritic Food Web
phytoplankton
dissolved organic
compounds (DOC)
phytobacteria
microzooplankton
phytoplanktivorous grazing zooplankton
fishes
predatory zooplankton
“predatory” fishes, mollusks, etc.
bacteria
larger
“predatory”
fishes, mammals, etc.
Neritic Benthic Food Web
particulate organic
matter (POM)
dissolved organic
compounds (DOC)
bacteria
collecting/scavenging animals
(annelid worms, echinoderms, mollusks
crustaceans, fishes, etc.)
predatory animals
(echinoderms, mollusks, crustaceans, fishes, etc.)
larger predatory animals
(mollusks, crustaceans, fishes, etc.)
Soft Substrate Communities
 Affected by constant change in substrate due
to wave action or sedimentation.
 Species composition usually more
structured by disturbance and predation (less
affected by competition)
Reefs & Banks
 Reef = a solid (hard) outcrop in shallow
water reached by sunlight.
(Not all are coral reefs. e.g., oyster reefs)
 Bank = shallower regions of the
offshore continental shelf.
Sea Grass Communities
 Fully aquatic submerged plants (true grasses).
 Require soft substrates. When present they
stabilize the substrates. Primary production
and species richness higeher.
Sea Grass Communities
Pipefish
Sharptail Eel
Lizard Fishes
Seahorses
Hard Substrate Communities
 Less change in substrate and substrate
provides fixed anchoring point.
 Species composition usually structured by
competition and predation (usually a little
less affected by disturbance)
Hard Substrate Limitation
 The predominance of soft bottoms means
that hard substrates are limited.
 Artificial reefs are rapidly colonized. Both
biomass and species richness are greater
around such reefs.
Rocky Intertidal Zonation
 Provides a gradient of physical conditions.
Tropical Coral Reefs
 Coral reefs found only
between 30º N and S
latitude & require shallow,
warm, clear water.
 Built by coral animals with
mutualistic algae – CaCO3
skeletons.
 The need for “shallow”
waters means that most
are around land.
Coral Polyps
Coral Polyps
Reef Types
Fringing Reef
flat
back reef
reef
face
Australia Great Barrier Reef
Tropical Coral Reef Communities
 Primary production from microphytic
algae in corals and macrophytic algae.
 Plankton from open water important.
 Very diverse communities.
 Structured by competition, predation, &
disturbance.
 Competition (especially for space) is
usually very intense. Many territorial
animals.
Butterfly Fishes
Bluehead Wrasse
Parrot Fishes
Cleaner Gobies
Human Impacts: General
 Pollutants from stream & direct runoff.
-additional sediment
-heavy metals & industrial pollutants
-phosphate (P) [and nitrate (N)]
 Over fishing/over harvest – removing
part of the community.
 Red Tides – blooms of certain species
of dinoflagellate (phytoplankon) that can
result in low oxygen and/or neurotoxin
release.
Human Impacts: Sea Grasses
 Pollutants from stream & direct runoff.
-additional sediment – can cover or
increase turbidity
-heavy metals & industrial pollutants
-phosphate (P) [and nitrate (N)] – overgrown
by periphyton and smothered
 Dredging (& dragging of boat anchors)
– root damage takes a long time for
recovery.
Human Impacts: Coral Reefs
 Pollutants from stream & direct runoff.
-additional sediment – can cover or
increase turbidity and smother
-heavy metals & industrial pollutants
-phosphate (P) [and nitrate (N)] – overgrown
by periphyton/macrophytes and smothered
 Physical Damage to the Reef –takes a
long time for recovery.
 Increase or decrease in temperature.
 Coral stress causes bleaching.
Human Impacts: Coral Reefs
Coral Bleaching
Coral Bleaching
Human Impacts: Fishing
 Reefs
-dynamite fishing
-poisoning
 Seagrass Beds
-dynamite fishing
-trawling – net drags
 Soft bottom
-trawling – net drags
-bycatch dumping