Life in the Ocean’s Depths

Survival in the Deep Sea• Sunlight fades with increased depth• Tremendous pressure of ocean depths–1 atm at sea level–Increase by 1 atm every 10 m

Adaptations to Pressure• Fluid pressure in animal

tissue matches the pressure of the surrounding water

• Tissue fluid pressure pushes against the surrounding pressure with an equal but opposite force– Prevents them from being

crushed

Adaptations to Cold• Body temperatures close to temperature of the

surrounding water– Slow metabolism• Move more slowly• Grow more slowly• Reproduce less frequently and later in life• Live longer than similar species in surface water• Require less food

• Body densities close to density of their environment– Do not have to expend energy to keep from sinking

Life in the Dark• Color in organisms:– Disphotic or twilight zone:• 150-450m below surface• Enough light to make countershading a means of camouflage• Ex: hatchet fish– Possess rows of photophores along bodies (light-

producing organs)» Aid in species recognition» Camouflage

Role of Bioluminescence• Common in animals found between 300-2400m– Some have bioluminescent organs (ex: squid, crustaceans, fish)– Some have bioluminescent bacteria in species-specific locations

(mutualism)• Occurs when a protein (luciferin) is combined with oxygen in the

presence of an enzyme (luciferase) and ATP– Chemical energy of ATP is converted into light energy

• Camouflage:–Will not appear as a shadow or silhouette

when seen from below

• Mating and species recognition:–Pattern of lights identifies species or individuals

as male or female – Signal readiness to mate by series of light flashes

• Attracting prey:–Bioluminescent lures and eyes

• Defense:–Bioluminescent fluid that clouds the water

with light•Confuses predators

Seeing in the Dark• Eyes of many deep-sea fishes are tubular and have 2

retinas versus 1– One retina views distant objects– Other sees closer things

• Better depth perception• Some have tiny eyes (slightly functional) or are blind and

must rely on tactile or chemical stimuli

Finding Mates in the Dark• Male bites female and remains attached,

sometimes for life (ex: anglerfish)–Lifelong parasite (fuses to female)

Finding Food in the Dark• Scarce in the deep sea– No photosynthetic organisms– Detritus from above

• Barbel– Fleshy projection that dangles below chin or throat– Lures to probe the bottom ooze for food– Can serve in species recognition during mating

Giants of the Deep• Live longer than shallow water relatives• Giant squid (Architeuthis)– Largest of all invertebrates (9-16m long)• Arms thick as human thigh and covered with

thousands of suckers– Capture prey and carry it to animal’s beak

where it is shredded to pieces– Found in all oceans 600 ft. or more– Anatomy indicates weak swimmers– Unknown diet– Hunted and eaten by sperm whales

Relicts From the DeepMany species have undergone little evolutionary change

• Spirula– Mollusk with spiral

internal shell of gas-filled chambers

– Resemble squids and octopuses

• Vampire squid– Webbing between the arms– Dark color– Muscles are soft and poorly

developed– Spend entire lives in deep

water– Good eyesight– Bioluminescent organs

• Coelocanth–1.8 m (6 ft.) long– Large, thick scales and

fleshy bundles between its body and fins

• Neopilina–Limpet-like mollusk–Lightweight conical shell–Large pink and blue foot

Life on the Sea Bottom• Benthic communities:– Must deal with extreme pressures, low

temperatures, and darkness– Impacted greatest by food availability– Sources of food:• Feces• Decaying tissue• Organic matter

– Food chains• Bacteria meiofauna (ex:

foraminiferans, nematodes) large worms and bivalves

• Vent communities:– Can be very productive– Can exist without solar energy– Not all surround hydrothermal vents

• Vent formation:– Form at spreading centers– Cold seawater seeps down near centers through cracks

and fissures in ocean floor• Comes into contact with hot basaltic magma

– Superheated water returns to the sea through chimney-like structures formed by minerals that have precipitated out of hot water

2 Types of Chimneys• White smokers–Produce stream of milky fluid rich in zinc sulfide–Temperature less than 300°C

• Black smokers– Narrow chimneys– Emit clear water with temperatures between 300-450°C rich in

copper sulfides• Encounters cold ocean water and sulfides precipitate,

producing black color

• Organisms:– Large clams, mussels, anemones, barnacles, limpets, crabs,

worms, and fishes– Large worms (10 feet long)– Primary producers are chemosynthetic bacteria

• Oxidize compounds such as hydrogen sulfide– Small animals feed directly on bacteria or can absorb

organic molecules released by bacteria when they die• Rise and fall or vent communities– Last about 20 years until vents become inactive