The Deep Ocean

Zonation in the Deep Ocean

• Bathypelagic - 1,000-4,000 m
• Abyssopelagic - 4,000-6,000 m
• Hadopelagic - below 6,000 m (to 11,000 m)

General Adaptations of Deep Ocean Organisms

• Countershading completely absent
• Colors generally drab gray or off-white, fish often black, shrimp red
• Bioluminescence widespread, but fewer photophores, mostly on head and sides
• Bioluminescence probably used for attracting prey or mates
• If eyes are present, then generally very small
• Abiotic factors fairly constant: pressure high, temperature just above freezing, chemical properties constant

The Problem of Food

• 5% of food produced in photic zone reaches here
• Deep sea fishes (most common are bristlemouths and anglerfish) are well adapted to low food
• Some are gulpers & swallowers

Sexual Reproduction

• Many of the fishes are hermaphroditic
• Photophores may be used to advertise for a mate
• Pheromones also used in some cases
• Male anglerfish attach to females using their jaws

The Effect of High Pressure

• Can be as high as 1,000 atmospheres in deepest trenches
• Many fish have no swim bladders
• Lower limit for fish is about 8,400 m

Feeding in the Benthos

• Fastest sinking material reaches bottom
• Chitin is broken down by bacteria to usable material for others
• Meiofauna abundant and eat bacteria & DOM
• Suspension feeders essentially absent, most are deposit feeders
• Predators are rare, but include crabs, sea stars, brittle stars, Pycnogonida, etc.
• Some of the invertebrates display deep-sea giantism
• Dead bodies are an important food source too, especially to amphipods, some of whom are specialized as scavengers
• In shallower areas fish may congregate at dead bodies
• See comparison of fish types (Fig. 15.31)

General Life Traits in Deep Sea

• Organisms grow more slowly and live longer
• Produce large eggs with a lot of yolk
• Produce few eggs, often times with feeding

For More on Hydrothermal Vents & Black Smokers

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