Aphotic Ecosystems A World Without Light

Plate Tectonics

Convergence Continental Mountain Ranges

Subduction Zones: Trenches Volcanic 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 Island Arcs - when ocean plate collides with ocean plate

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? Which are photic? 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 Gulper Eel - Loosely hinged, huge mouth Black swallower - elastic stomach

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 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