1. Chapter 15
Life Near the Surface

3. Vast open sea – pelagic realm
Contains almost all of the liquid water on earth

4. How the Open Sea Effects You
Regulates our climate
Conditions our atmosphere
Provides food and many resources

5. Life in the Pelagic
Pelagic organisms live suspended in their liquid medium
Lacks the solid physical structure provided by the bottom
No place for attachment, no bottom for burrowing, nothing to hide behind

6. Epipelagic Upper pelagic
Zone from the surface down to a given depth commonly 200 m (650 ft)
Warmest
Best lit
Similar to the photic zone (area where photosynthesis can occur)

7. Pelagic 1. Epipelagic 2. Mesopelagic 3. Bathypelagic 4. Abyssopelagic
Benthic 5. Littoral, Sub-littoral 6. Bathyal 7. Abyssal 8. Ultra-abyssal

8. Two Main Components
1.Coastal or Nertic – epipelagic waters that lie over the continental shelf
Lies close to shore
Supports most of the world’s marine fisheries production

9. Oceanic part
Waters beyond the continental shelf

10. The Organisms of the Epipelagic

11. The Pelagic Realm Fueled by solar energy captured in photosynthesis
Nearly all primary production takes place within the epiplagic system itself
Gets almost no external input of organic matter
Supplies food to other communities

12. Lacks deposit feeders
Suspension feeders are very common
There are also many large predators like fishes, squids and marine mammals

13. The Plankton: A New Understanding

14. Scientist used to study plankton by catching them in tow nets
This practice limited what organisms were caught

15. Recent developments in collecting plankton have lead to the discovery of many new groups of plankton and have changed how the plankton interactions are currently looked at

16. Plankton can be grouped based on their size
Picoplankton – smallest
Nanoplankton
Microplankton
Mesoplankton
Macroplankton
Megaplankton – largest

17. Phytoplankton – perform photosynthesis
Zooplankton – cannot perform photosynthesis - heterotrophs

20. Phytoplankton – Major Groups

21. Net Plankton (Micro, Meso, Macro)
Diatoms – found everywhere – important primary producers
Dinoflagellates found everywhere, most common in warm waters – common red tide organisms

22. Dinoflagellates
Diatoms

23. Colonial cyanobacteria (Trichodesmium) – mainly tropical – can fix atmospheric nitrogen – causes red tides in the Red Sea

24. Nanoplankton
Coccolithophorids – important primary producers in nutrient poor waters
Cryptophytes – very important primary producers
Silicoflagellates – sometimes form blooms

25. Coccolithophorids

26. Picoplankton
Unicellular cyanobacteria (Prochlorococcus) dominant primary producers, especially in nutrient poor water
Various protists – presence of many groups recently discovered

27. ZooPlankton

28. Phytoplankton form the base of the food web
Solar energy that they capture and store in organic matter is passed on to the other creatures of the epipelagic from minute zooplankton to gigantic whales
Herbivores eat phytoplankton

29. Zooplankton are by far the most important herbivores in the epipelagic
Very few zooplankton are strict herbivores – will eat other zooplankton
Most zooplankton species are primarily carnivorous and hardly eat phytoplankton at all

30. Protozoan Zooplankton
Protozoans can catch tiny picoplankton and nanoplankton
Without protozoans, much of the primary production in the epipelagic would go unutilized
Flagellates, Ciliates, Foraminiferans, Radiolarians

31. Foraminiferans
Radiolarians

32. Copepods Small crustaceans Dominate the net zooplankton
Most abundant members of the net zooplankton practically everywhere in the ocean – 70% or more of the community
Major carnivores

33. Copepods

34. Other Crustaceans – Shrimp-Like Krill
Not as abundant as copepods but often aggregate into huge dense swarms
Dominate the plankton in the polar seas

35. Efficient filter feeders – diatoms are a favorite food, also eat detritus
Relatively big – up to 6 cm
Eaten by fishes, seabirds, great whales

36. Krill

38. Non-Crustacean Zooplantkon
Salps – transparent, planktonic herbivores – filter out plankton by pumping water through a sieve-like sac or a fine mucus net
Larvaceans – float inside a house they make of mucus – beat tail to move water through the house – food particles are caught in a complicated mucus net that is inside the house

39. Pteropods – mollusks – small snails that have a foot that has been modified to form a pair of wings that they flap to stay afloat
Arrow Worms or chaetognaths – extremely important predators in the zooplankton – feed mostly on copepods

41. Jellyfish and siphonophores – large, weak swimmers that drift with the currents – carnivore

42. Holoplankton
Spend their whole lives as plankton

43. Meroplankton Many fish and invertebrates have planktonic larvae
Temporary members of the plankton
Small larvae feed on phytoplankton

44. Larger larvae feed on zooplankton
Larvae can grow while in the plankton and change trophic levels

45. The Nekton

46. Large strong swimmers
Fishes, marine mammals, squids, turtles, sea snakes, penguins
Carnivorous

47. Planktivorous nekton – eat plankton – include herrings, sardines and anchovies, whale shark and the basking shark

48. Herring
Sardines
Anchovies

49. Most species of nekton eat other nekton
Fishes, squids and large crustaceans are the main foods
Epipelagic predators are not fussy, just need to be the right size

51. In general the larger the predator the larger the prey
Herrings (small fish) – zooplankton
Sperm whale largest of nekton – giant squid 10 m (33 ft long)

52. Living in the Epipelagic
Demands of the environment cause organisms to have certain adaptations
Two main problems
Need to stay in the epipelagic zone
Need to eat and avoid being eaten

53. Staying Afloat
Cells and tissues are denser than water – naturally sink
Shells and skeletons are even more dense
Phytoplankton need to stay for sun and the others need to stay so they can get prey

54. How to stay afloat if you can not swim
Increase the water resistance so that you sink slower
Make yourself more buoyant

55. Increased Resistance
Drag – resistance to movement through water or any other medium
Small organisms – drag mostly depends on surface area – higher the surface area the slower the organism sinks – reason plankton are so small

56. Shape influences surface area – parachute shape slows sinking (jellyfish)
Flat shapes slow sinking
Long projections or spines increase surface area and therefore decrease the rate of sinking
Forming chains slows sinking

57. Swimming organisms rarely have spines as this would increase water resistance and make swimming harder
They generally have adaptations that reduce drag

58. Increase Buoyancy Reduces the tendency to sink
Store lipids (Oils or fats)
Lipids are less dense so they tend to float
Diatoms, copepod and fish eggs contain a drop of oil
Many adult fish store lipids – especially sharks and tuna

59. Whales, seals and other marine mammals have a great deal of buoyant fat in a thick layer of blubber under the skin
Pocket of gas is another adaptation

60. Bony fish have swim bladders – disadvantage – gases expand and contract as the fish moves in the water column

61. The Floaters
Neuston – organisms that live right at the sea surface but remain underwater
Pleuston – organisms whose bodies project through the sea surface into the air
Most common method is to have a gas-filled structure

62. By-the-wind-sailor – (Velella) – colonial jellyfish-like cnidarian that is specialized as a float
Portuguese man-of-war (Physalia) – powerful sting – part of the colony acts as a sail
Violet shell (Janthina)- makes a rafts of mucus filled with bubbles from which it hangs upside down

63. Physalia
Velella
Velella

64. Janthina

65. Predators and their Prey
Many of the adaptations of epipelagic animals are related to their need to find food and at the same time avoid being eaten

66. Sense Organs Highly developed
Vision is important – many have good eyesight
Vision is especially important to the nekton because there are no solid structures to avoid concealment

67. Lateral line – remote sensing system that sense vibrations in the water – used to stay with school mates and detect predators

69. Coloring and Camouflage
Protective coloration or camouflage
Nearly universal among epipelagic organisms that are large enough to be seen
One way – transparent – jellyfish, salps, larvaceans, comb jellies

70. Countershading – dorsal surface (back) is dark usually green, blue or black and the belly (ventral surface) is white or silver
Looking down – ocean depths are dark blue and it is hard to see the prey
Looking up – bright light is filtered down and it is hard to see the prey

72. Laterally compressed bodies are also common – reduce the size of the silhouette

73. Silvery sides – reflect light – help to blend in
Vertical bars or irregular patterns – help to break up their outline in the dappled under water light

75. Swimming: The Need for Speed
Whether the prey gets away or the predator gets a meal depends on which swims faster
Emphasis is on sheer speed
Epipelagic contains the worlds most powerful swimmers

76. Practically all epipelagic nekton have streamlined bodies that make swimming easier & more efficient
Do not have features that increase resistance (like spines, bulging eyes)

77. Laterally compressed bodies are also common – reduce the size of the silhouette
Firm and Muscular

78. Force is delivered mainly by the tail
The tail is high and narrow
Fins tend to be stiff – provides maneuverability and lift

79. Fishes have two types of muscle – red and white – red muscle gets its color from the high concentration of myoglobin (stores oxygen)
Red muscle – best suited for long sustained effort – for sustained cruising

80. White muscle – provides short burst of power
Epipelagic sharks, tuna and billfishes have evolved a system to conserve the heat generated by their muscles and keep their internal temperatures above that of the surrounding water

81. Vertical Migration
Pelagic waters are dangerous but they also contain the most food
Some zooplankton spend only part of their time near the surface and then retreat to safer, deeper water
Usually live at least 200m or 650 ft down

82. Epipelagic Food Webs

83. Of great interest, especially because epipelagic fishes provide food and employment to millions

86. Trophic Levels and Energy Flow
Very complex
Epipelagic contains vast numbers of different species
Feeding habits of most of them are poorly known
Most of the animals eat a variety of prey often from different trophic levels

87. Most epipelagic animals consume different prey at different times in their lives
The basic flow of energy in the epipelagic can be depicted as phytoplankton  zooplankton  Small nekton  Large nekton top predators

89. Epipelagic food chains usually have many steps and are generally longer than in other ecosystems
Tropical usually have more levels than colder waters

90. Epipelagic is an exception to the 10% rule
Herbivores pass on 20% and the carnivores pass on more than 10% also

91. Patterns of Production

92. Epipelagic food webs are complex but they all share one simple feature: primary production by phytoplankton is the base

94. Some areas of the epipelagic are among the most productive on earth and some are “deserts”

95. Phytoplankton need 2 main things to perform photosynthesis:
Sunlight
Supply of essential nutrients

96. Ocean Productivity
       
Red areas contain the most life, while the purple areas are nearly empty of life. Ocean areas of high productivity support more life than less productive areas. It is as simple as more food = more fish. More oxygen is produced and carbon dioxide consumed in these highly productive areas of the ocean.

97. Light Limitation Must get all their light during the day
May be light-limited during the winter
Total primary production also depends on how far down light penetrates into the water column

98. Nutrients
Nitrogen, iron and phosphorus play a major part in controlling primary production
Nitrogen is most often the limiting nutrient
Most nutrients come from recycling

99. Much of the organic matter ends up as detritus (fecal pellets, dead bodies)
Often the detritus sinks past the epipelagic zone before it releases its nutrients
Deep water is usually nutrient rich

100. Seasonal Patterns
Can cause nutrient laden cold water to come to the surface
As the water cools it sinks, breaks up the thermocline and allows surface waters to mix with deep nutrient rich water

102. Upwelling Caused by Ekman Transport
Occur mainly along the eastern sides of ocean basins where the prevailing winds blow parallel to the coast
Ekman transport carries the warm surface water offshore

105. This allows the deeper nutrient rich water to move to the surface
Major coastal upwelling areas are among the most productive waters of the epipelagic
In the pacific there can be equatorial upwelling