1. Chapter 15
Life Near the Surface

2. The Ocean Surface Ocean divided into layers Epipelagic on the top
Also part of the photic zone
Epipelagic divided into 2 parts
1) Neritic – near the coast
2) Oceanic – beyond the continental shelf

3. Living in the Epipelagic
Advantages
Photic zone
Fuels photosynthesis
Massive amount of primary production
Lots of food
Disadvantages
No sediment to latch onto
Prone to predation
No shelter
Staying afloat

4. Plankton Dominant organisms of the epipelagic
Moved by the currents of the ocean
Not strong swimmers
Categorized by
Size
Time spent as part of the plankton
Trophic level

5. R

6. Plankton Life History Holoplankton Meroplankton
Spend entire lives as part of the plankton
Feed, reproduce, and live in the plankton
Meroplankton
Only spend part of their lives as plankton
Larval stage the most common
Larva of
Echinoderms
Molluscs
Crustaceans
Fish

7. Plankton Trophic Levels
Phytoplankton
Primary producers
Photosynthetic
Zooplankton
Consumers
Eat phytoplankton and other zooplankton

8. Phytoplankton Primary producers Include
Photosynthesis produces 50% of Earth’s oxygen
Include
Diatoms
Dinoflagellates
Cyanobacteria
Coccolithophores
Cryptophytes
All protists, except cyanobacteria

9. Diatoms Produce 25-30% of Earth’s oxygen
Highly abundant worldwide in marine and freshwater habitats
Especially in temperate and polar waters

10. Dinoflagellates Prefer warmer waters than diatoms
Can bloom and cause red tides
Better adapted than diatoms to low- nutrient conditions

11. Coccolithophores Prefer oceanic zone Very abundant group
Formed chalk deposits around the world
Important carbon sinks

12. Cryptophytes Commonly known as cryptomonads
Found more in neritic waters
Asymmetrical cell shapes
Some species eat bacteria and photosynthesize

13. Cyanobacteria Bacteria that can photosynthesize
Not protists, unlike other phytoplankton
Produce at least 50% of the ocean’s primary production
Can cause dangerous blooms

14. Zooplankton Consumers Very diverse, includes some
Eat phytoplankton and other zooplankton
Very diverse, includes some
Protozoans
Crustaceans
Invertebrate chordates
Molluscs
Annelids
Cnidarians

15. Protozoans All protists Mostly flagellates Also
Ciliates
Foraminiferans
Radiolarian
Many also phytoplankton

16. Crustaceans Copepods make up 70% of planktonic crustaceans
Very small in size
Food for many organisms
Krill are also common
Consume waste from other zooplankton
Other planktonic crustaceans
Amphipods
Some decapods

17. Invertebrate Chordates
Relatives of tunicates
Salps
Filter water through mucus net for phytoplankton
Larvaceans
Make a “house” of mucus
House pumps in water and filters it for food
Eventually houses become clogged and are discarded
Deposits carbon on the sea floor

18. Molluscs Pteropods Glaucus atlanticus Snails that can swim well
Foot adapted to be like wings
Flaps to stay afloat
Shelled or shelless
Glaucus atlanticus
Common names include blue angel, blue dragon
Sea slug adapted for floating
Consumes Portuguese man-o-war
Absorbs venom and stores it in the skin

19. Annelids Arrow worms (chaetognaths) Abundant in the plankton
Feed on copepods
Important link in the food web

20. Cnidarians Jellies are weak swimmers Often carried by currents
Part of the plankton
Consume zooplankton

21. Nekton Strong swimmers Most are carnivorous Include
Not pulled by current
Most are carnivorous
Include
Fish that feed on plankton
Fish that eat other fish
Whales and dolphins
Marine birds and reptiles

22. Staying in the Epipelagic
The problem of sinking
How to stay in the epipelagic zone?
Epipelagic organisms have adaptations as solutions
Increase water resistance
Drag
Increase buoyancy

23. Water Resistance
Drag
Measure of how much fluid resistance an object has
More drag means harder to move in fluid
Harder to move = harder to sink
Some epipelagic organisms increase body surface area to increase drag
Body shapes flattened
Spines

25. Buoyancy
The measure of how much upward force an object exerts in a fluid
How much an object resists being immersed
Many organisms produce lipids, which increase buoyancy
Diatoms produce oil molecules
Sharks have fat deposits
Bony fish have swim bladders filled with gas

26. Predators and Prey Finding food without being eaten
No place to hide
Predators and prey use
Sense organs
Camouflage
Swimming ability
Vertical migration

27. Sense Organs Lots of light in the photic zone Lateral line system
Highly developed eyes
Lateral line system
Fish
Detects vibrations in water
Echolocation
Dolphins and other cetaceans
Sonar that detects solid objects

28. Camouflage Coloration for protection Transparency is common
Best defense is not to be seen
Transparency is common
Countershading
Top side is darker
Bottom side is lighter
Matches the colors of the ocean
Bodies compressed laterally to decrease silhouette
Thin body is harder to see

29. Swimming Both predators and prey need to move fast
Streamlined bodies to reduce drag
Fish have
Smaller scales, or none
Mucus on skin to lubricate their bodies
Mammals have
Lost their hair

30. Vertical Migration Some epipelagic organisms leave the epipelagic
Mostly zooplankton
Especially dinoflagellates
Migrations to deep (>200m) water
Come back up at night when it is safer

31. Epipelagic Food Webs Important to understand
Sustains fisheries
Allows better managment
Very complicated due to the amount of organisms involved

33. Energy Flow Energy moves from one trophic level to the one above it
Generally 10% on land
But, is closer to 20% in the epipelagic
Feeding higher reduces energy intake efficiency
Why giant whales feed on tiny krill

34. Dissolved Organic Material
Huge amount produced in the oceans
Decaying matter from many organisms
Forms marine snow that drifts down
Energy from DOM is used by bacteria
Reenters the food web

35. Primary Production Limits
Phytoplankton growth is limited by different factors
Light
Nutrients
Season

36. Light Epipelagic is exposed to a lot of light
But light can be blocked
No photosynthesis occurs at night
High concentrations of phytoplankton block light
Self-shading

37. Nutrients Phytoplankton need nutrients to grow
Lowest available nutrient is the limiting nutrient
Most often nitrogen in the ocean
Phosphorus to a lesser degree

38. Season Colder water becomes more dense
Eventually the surface water will sink
Overturn
Water from the deep is mixed with surface water
Brings nutrients from the deep ocean
Changing seasons produce overturns
Spring bloom
Fall bloom

40. Upwelling Water can move up in certain conditions
Carries large amount of nutrients
Winds push water away from the coast
Ekman transport
Deep water moves in to replace the displaced water
Leads to areas of very high productivity