aphotic ecosystems a world without light. plate tectonics
TRANSCRIPT
Aphotic Ecosystems
A World Without Light
Plate Tectonics
ConvergenceContinental Mountain Ranges
Subduction Zones: TrenchesVolcanic Mountain Ranges or Island Arcs form on the continental plate
Seafloor is made of dense basalt which “dives” under lighter continental granite
Island Arcs - when ocean plate collides with ocean plate
Aleutian Islands
Location of Plates
Hot Spots
Hot spots remain stationary, but above them, the Earth's crustal plates move slowly.
Imagine moving a sheet of paper horizontally a few inches above a burning candle.
Similar to the candle's flame, a hot spot leaves a scorched trail of volcanic islands on its overlying plate.
Zones review What are the open ocean
zones? Epipelagic Mesopelagic Bathypelagic Abyssoplegic Hadalpelagic
Every Mother Buys A Handbag
Which are photic? Only the epipelagic (top 100m) lies
in the photic zone Photosynthesis
Which are aphotic? All the rest No photosynthesis
Oxygen in the Deep Sea Depend on the surface for
Oxygen Oxygen Balance
Added Mixing Photosynthesis
Taken out Respiration
Thermohaline Circulation Ocean Conveyor Belt Brings oxygen to deep sea
The map shows how oxygen is distributed in the global ocean. Regions of near-zero oxygen, are colored purple and are concentrated in the tropics.
Ocean Conveyor Belt provides Oxygen to the Deep Sea as Cold Dense Water Sinks
http://www.divediscover.whoi.edu/circulation/index.html
Epipelagic
Photosynthesis Lots of oxygen & food Fish
Fast swimming Streamlined Strong muscles
Countershading Dark dorsal side Light ventral side Helps organisms hide
Mesopelagic Twilight Zone Some light but not enough
for photosynthesis 200m-1000m Main thermocline occurs
here Rapid temperature change Density layer (invisible
barrier) Organisms that move through
this layer must be adapted to deal with this temperature change
Zooplankton of the Mesopelagic:Midwater Organisms
Krill, shrimp & copepods Ostracods
Carapace that makes them look like clams with legs
Usually 1/8 in long Gigantocypris is ½ in
Amphipods Arrow worms
Worm-like predators Squid Jellies & comb jellies Photophores
Bioluminescent organs
Fish of the Mesopelagic:Midwater Organisms
Most fish are very small
Hatchetfish Viperfish Bristlemouths are
most common Cyclothone
signata is the most abundant fish on earth
Photophores
Adaptations in Mesopelagic:Feeding
Lack of food Small size (growing takes
energy) Live under productive
oceans where there is more detritus
Large mouths to avoid gape limitation
Elastic stomach to eat organisms larger than themselves
Broad diets (eat anything they can find)
Some move to the surface at night to feed
Black swallower - elastic stomach
Gulper Eel - Loosely hinged, huge mouth
Adaptations in Mesopelagic:Vertical Migration
Migratory (up to feed at night & down to hide during day) Layer of vertical migrators is called the Deep
Scattering Layer Tolerate wide range of temperatures as they cross the thermocline Strong muscles & bones Swim bladder (helps keep buoyancy when changing depth)
Can rapidly release gas Many filled with fat instead
Adaptations in Mesopelagic:Vertical Migration
Non-migratory Eat detritus-decaying organic matter from the
epipelagic Flabby muscles/weak bones makes them more
buoyant Don’t swim much so they aren’t very streamlined No swim bladder (saves energy) Eat the vertical migrating fish because they are more
nutritious than non-migrators
Adaptations in Mesopelagic:Sense Organs
Large sensitive eyes Some have tubular eyes
Like having 2 pairs of eyes See well only in the direction
they are aimed (usually upward)
Have a second retina to compensate & aid in lateral vision
Retinas are the light sensitive part of the eye located on the back
Second retina is on the side to aid seeing objects on the side
Adaptations in Mesopelagic:Coloration & Body Shape
Takes too much energy to swim fast or grow spines for predator avoidance Camouflage is main source of protection
Transparency More common in shallower mesopelagic
Silvery Middle of mesopelagic
Red or Black Deeper mesopelagic Red light is the first light filtered out so red appears black in the depths Black is a bit more visible because blue light is reflected
Countershading Black back & silvery sides
Reduction of silhouette long thin bodies that disappear from some angles
Adaptations of Mesoplegaic:Bioluminescence
Attract mates or Communication Confuse Predators
Bioluminescent fluids Squirt these fluids out to distract predators
Counterillumination (like countershading) Photophores on the belly match blue-green sunlight above
Symbiotic bacteria or chemical in tissues Can control intensity (brightness) of their photophores Animals looking up at their prey can’t see the shadow that would be produced Tests on bioluminescent shrimp show that this is controlled by eyesight
Shrimp with blinders produce no light Eyes exposed to more light/ shrimps bodies produced brighter bioluminescence
Attract or see prey Bioluminescent anglerfish lures Or headlights used like flashlights (some are even red lights to see red fish) Some predatory fish have special eyes that can tell the difference between photophores and the sun!
Adaptations of Mesopelagic:Oxygen Minimum Layer
500m Oxygen Minimum Not in contact with atmosphere Little or no photosynthesis Lots of respiration
more detritus than deeper zones
Large gills Inactive so they use less oxygen Hemoglobin
Protein in blood Transports oxygen to body tissues Functions well in low oxygen
environments
Deep Sea Pelagic
Largest environment on earth
75% of the ocean Area of the ocean that
receives no light No seafloor bottom Relatively constant physical
environment Little change in temp (2C),
light (none), salinity etc. Includes:
Bathypelagic Abyssopelagic Hadopelagic (trenches)
Deep Sea Pelagic:Bioluminescence, camouflage & vision
Bioluminescence Courtship,
communication, attracting prey, confusing predators
Not for counter illumination
Less common than in mesopelagic
Most organisms are black or red
Small eyes or blindness
Deep Sea Pelagic:Lack of food
Only 5% of photic production makes it as detritus 20% in mesopelagic
Large mouths & stomachs No vertical migration Hardly move / wait for prey
Lure prey Small, but larger than
mesopelagic Grow slowly but live longer than
in mesopelagic Reproduce later in life Flabby muscles & weak bones Poorly developed circulatory &
nervous systems No scales No swim bladders Can use energy that isn’t used
in migration & reproduction
Deep Sea Pelagic:Reproduction Mates are hide to find
Right species Right gender Low abundance High diversity
Hermaphrodites Can mate with anyone in the species Both are fertilized 2 for the price of one
Attract mates Pheromones-chemicals in the water bioluminescence
Male parasitism Males permanently attach to females
Deep Sea Pelagic:Extreme Pressure
Makes it hard to study the deep
Pressure resistant enzymes
Lack swim bladders Too much energy to fill in
the deep Deepest fish
8,370 m Invertebrates
Found in Mariana Trench 11,022m
Deep Sea Pelagic Fish
Small, but larger than mesopelagic
No streamlining Weak flabby muscles Small eyes / no eyes Black, red, or no color Bioluminescence
Attract mates & prey
Benthic Deep Sea:Food
Deep seafloor & detritus Detritus from above sinks to the bottom
Marine snow Most is eaten before it reaches the bottom
Food that is missed doesn't keep sinking Food particles accumulate on benthos Bacteria
Decompose detritus Bacteria are eaten
Deposit feeders Eat food that has settled on the bottom Infauna-live in sediment Epifauna-live on sediment
(all pictured)
Benthic Deep Sea Fish
Large Elongated bodies Strong muscles Small eyes Dark brown, white or
black Only some
bioluminescense
Location of Seeps & Vents
Bacteria & Bologna
Alvin sank with lunches on board sub was recovered after ten months on the bottom the seawater soaked lunches were in a remarkable
state of preservation. Bologna sandwiches were not spoiled and the meat was
still pink. The apples tasted salty, but were still quite fresh. The lunches had just been sitting in an open leather
satchel inside the sub, protected from all the little scavenging animals, but free for microbes to act.
Decomposition is slow & so is metabolism
Oasis: Cold Seeps Discovered 1984 in Gulf of Mexico
Methane & sulfur seep out of the ground Methane hydrate is frozen, but not
cold to the touch and will light on fire if you put a match to it “fire ice”
Slow & steady emisson Chemosynthesizing bacteria
Slow growth rates World oldest invertebrate
Lamellibrachia luymesi Live 250 years
Oasis: Brine Pool extreme concentration of salinity
5x the salinity of the ocean Kills organisms accidentally
swimming into them So salty that the submersibles (like
Alvin) can hardly penetrate into them
just sit there, on top of the salt-"inversion" boundary.
rich sources of methane Chemosynthesis
dense colonies of mussels form on the halocline symbiotic relationship with
methanogenic (methane-metabolizing) bacteria
Bacteria live in the gills
Oasis: Whale falls
Discovered in 1987 Whale or other animal
carcass that has fallen to the seafloor
Feeds scavengers for decades
Oasis:Hydrothermal Vents
Water seeps into seafloor fissures heats up, reemerges loaded with
minerals Water jets out of vents in the
seafloor hits cold water, minerals precipitate out & leave mineral deposits that build
up into chimneys or smokers (white or black)
H2S (hydrogen sulfide) is also released, used by chemosynthetic bacteria
Biology: High abundance Low diversity Tubeworms
Riftia - 6 - 10 feet long, Alvinella, Tevnia, Pompeii worm
Discovery of Vents
Found in 1977 in the Galapagos Rift valley
Marine Geologists
Scientists thought that there was no life in the depths (no life without light)
Alvin submersible
Location of vents
Vents are found on Ridges
Phylum: Annelida