Chapter 15Chapter 15Life Near the

SurfaceLife Near the

Surface

Vast open sea – pelagic realmContains almost all of the

liquid water on earth

Vast open sea – pelagic realmContains almost all of the

liquid water on earth

How the Open Sea Effects You

How the Open Sea Effects You

Regulates our climateConditions our atmosphereProvides food and many

resources

Regulates our climateConditions our atmosphereProvides food and many

resources

Life in the PelagicLife 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

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

EpipelagicEpipelagic

Upper pelagicZone from the surface down to a

given depth commonly 200 m (650 ft)

Warmest Best litSimilar to the photic zone (area

where photosynthesis can occur)

Upper pelagicZone from the surface down to a

given depth commonly 200 m (650 ft)

Warmest Best litSimilar to the photic zone (area

where photosynthesis can occur)

I. Pelagic 1. Epipelagic 2. Mesopelagic 3. Bathypelagic 4. Abyssopelagic

II. Benthic 5. Littoral, Sub-littoral 6. Bathyal 7. Abyssal 8. Ultra-abyssal

Two Main ComponentsTwo Main Components

1.Coastal or Nertic – epipelagic waters that lie over the continental shelf

Lies close to shoreSupports most of the world’s

marine fisheries production

1.Coastal or Nertic – epipelagic waters that lie over the continental shelf

Lies close to shoreSupports most of the world’s

marine fisheries production

2.Oceanic partWaters beyond the continental shelf

2.Oceanic partWaters beyond the continental shelf

The Organisms of the Epipelagic

The Organisms of the Epipelagic

The Pelagic RealmThe 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

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

Lacks deposit feedersSuspension feeders are very

commonThere are also many large

predators like fishes, squids and marine mammals

Lacks deposit feedersSuspension feeders are very

commonThere are also many large

predators like fishes, squids and marine mammals

The Plankton: A New

Understanding

The Plankton: A New

Understanding

Scientist used to study plankton by catching them in tow nets

This practice limited what organisms were caught

Scientist used to study plankton by catching them in tow nets

This practice limited what organisms were caught

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

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

Plankton can be grouped based on their size

Plankton can be grouped based on their size

Picoplankton – smallestNanoplanktonMicroplanktonMesoplanktonMacroplanktonMegaplankton – largest

Picoplankton – smallestNanoplanktonMicroplanktonMesoplanktonMacroplanktonMegaplankton – largest

Phytoplankton – perform photosynthesis

Zooplankton – cannot perform photosynthesis - heterotrophs

Phytoplankton – perform photosynthesis

Zooplankton – cannot perform photosynthesis - heterotrophs

Phytoplankton – Major Groups

Phytoplankton – Major Groups

Net Plankton (Micro, Meso, Macro)

Net Plankton (Micro, Meso, Macro)

Diatoms – found everywhere – important primary producers

Dinoflagellates found everywhere, most common in warm waters – common red tide organisms

Diatoms – found everywhere – important primary producers

Dinoflagellates found everywhere, most common in warm waters – common red tide organisms

Diatoms

Dinoflagellates

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

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

NanoplanktonNanoplankton

Coccolithophorids – important primary producers in nutrient poor waters

Cryptophytes – very important primary producers

Silicoflagellates – sometimes form blooms

Coccolithophorids – important primary producers in nutrient poor waters

Cryptophytes – very important primary producers

Silicoflagellates – sometimes form blooms

CoccolithophoridsCoccolithophorids

PicoplanktonPicoplankton

Unicellular cyanobacteria (Prochlorococcus) dominant primary producers, especially in nutrient poor water

Various protists – presence of many groups recently discovered

Unicellular cyanobacteria (Prochlorococcus) dominant primary producers, especially in nutrient poor water

Various protists – presence of many groups recently discovered

ZooPlanktonZooPlankton

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

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

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

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

Protozoan ZooplanktonProtozoan 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

Protozoans can catch tiny picoplankton and nanoplankton

Without protozoans, much of the primary production in the epipelagic would go unutilized

Flagellates, Ciliates, Foraminiferans, Radiolarians

Foraminiferans

Radiolarians

CopepodsCopepods

Small crustaceansDominate the net zooplanktonMost abundant members of

the net zooplankton practically everywhere in the ocean – 70% or more of the community

Major carnivores

Small crustaceansDominate the net zooplanktonMost abundant members of

the net zooplankton practically everywhere in the ocean – 70% or more of the community

Major carnivores

Copepods

Other Crustaceans – Shrimp-Like Krill

Other Crustaceans – Shrimp-Like Krill

Not as abundant as copepods but often aggregate into huge dense swarms

Dominate the plankton in the polar seas

Not as abundant as copepods but often aggregate into huge dense swarms

Dominate the plankton in the polar seas

Efficient filter feeders – diatoms are a favorite food, also eat detritus

Relatively big – up to 6 cmEaten by fishes, seabirds,

great whales

Efficient filter feeders – diatoms are a favorite food, also eat detritus

Relatively big – up to 6 cmEaten by fishes, seabirds,

great whales

Krill

Non-Crustacean Zooplantkon

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

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

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

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

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

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

HoloplanktonHoloplankton

Spend their whole lives as plankton

Spend their whole lives as plankton

MeroplanktonMeroplankton

Many fish and invertebrates have planktonic larvae

Temporary members of the plankton

Small larvae feed on phytoplankton

Many fish and invertebrates have planktonic larvae

Temporary members of the plankton

Small larvae feed on phytoplankton

Larger larvae feed on zooplankton

Larvae can grow while in the plankton and change trophic levels

Larger larvae feed on zooplankton

Larvae can grow while in the plankton and change trophic levels

The NektonThe Nekton

Large strong swimmersFishes, marine mammals,

squids, turtles, sea snakes, penguins

Carnivorous

Large strong swimmersFishes, marine mammals,

squids, turtles, sea snakes, penguins

Carnivorous

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

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

Herring

AnchoviesSardines

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

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

In general the larger the predator the larger the

prey

In general the larger the predator the larger the

preyHerrings (small fish) –

zooplanktonSperm whale largest of

nekton – giant squid 10 m (33 ft long)

Herrings (small fish) – zooplankton

Sperm whale largest of nekton – giant squid 10 m (33 ft long)

Living in the EpipelagicLiving in the Epipelagic

Demands of the environment cause organisms to have certain adaptations

Two main problemsNeed to stay in the epipelagic

zoneNeed to eat and avoid being

eaten

Demands of the environment cause organisms to have certain adaptations

Two main problemsNeed to stay in the epipelagic

zoneNeed to eat and avoid being

eaten

Staying AfloatStaying 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

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

How to stay afloat if you can not swim

How to stay afloat if you can not swim

Increase the water resistance so that you sink slower

Make yourself more buoyant

Increase the water resistance so that you sink slower

Make yourself more buoyant

Increased ResistanceIncreased 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

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

Shape influences surface area – parachute shape slows sinking (jellyfish)

Flat shapes slow sinkingLong projections or spines

increase surface area and therefore decrease the rate of sinking

Forming chains slows sinking

Shape influences surface area – parachute shape slows sinking (jellyfish)

Flat shapes slow sinkingLong projections or spines

increase surface area and therefore decrease the rate of sinking

Forming chains slows sinking

Swimming organisms rarely have spines as this would increase water resistance and make swimming harder

They generally have adaptations that reduce drag

Swimming organisms rarely have spines as this would increase water resistance and make swimming harder

They generally have adaptations that reduce drag

Increase BuoyancyIncrease Buoyancy

Reduces the tendency to sinkStore lipids (Oils or fats)Lipids are less dense so they

tend to floatDiatoms, copepod and fish

eggs contain a drop of oilMany adult fish store lipids –

especially sharks and tuna

Reduces the tendency to sinkStore lipids (Oils or fats)Lipids are less dense so they

tend to floatDiatoms, copepod and fish

eggs contain a drop of oilMany adult fish store lipids –

especially sharks and tuna

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

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

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

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

The FloatersThe 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

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

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

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

VelellaVelella

Physalia

Janthina

Predators and their Prey

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

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

Sense OrgansSense Organs

Highly developedVision is important – many have

good eyesightVision is especially important to

the nekton because there are no solid structures to avoid concealment

Highly developedVision is important – many have

good eyesightVision is especially important to

the nekton because there are no solid structures to avoid concealment

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

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

Coloring and Camouflage

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

Protective coloration or camouflage

Nearly universal among epipelagic organisms that are large enough to be seen

One way – transparent – jellyfish, salps, larvaceans, comb jellies

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

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

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

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

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

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

Swimming: The Need for Speed

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 speedEpipelagic contains the

worlds most powerful swimmers

Whether the prey gets away or the predator gets a meal depends on which swims faster

Emphasis is on sheer speedEpipelagic contains the

worlds most powerful swimmers

Practically all epipelagic nekton have streamlined bodies that make swimming easier & more efficient

Do not have features that increase resistance (like spines, bulging eyes)

Practically all epipelagic nekton have streamlined bodies that make swimming easier & more efficient

Do not have features that increase resistance (like spines, bulging eyes)

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

Firm and Muscular

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

Firm and Muscular

Force is delivered mainly by the tail

The tail is high and narrowFins tend to be stiff – provides

maneuverability and lift

Force is delivered mainly by the tail

The tail is high and narrowFins tend to be stiff – provides

maneuverability and lift

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

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

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

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

Vertical MigrationVertical 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

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

Epipelagic Food Webs

Epipelagic Food Webs

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

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

Trophic Levels and Energy Flow

Trophic Levels and Energy Flow

Very complexEpipelagic contains vast

numbers of different speciesFeeding habits of most of

them are poorly knownMost of the animals eat a

variety of prey often from different trophic levels

Very complexEpipelagic contains vast

numbers of different speciesFeeding habits of most of

them are poorly knownMost of the animals eat a

variety of prey often from different trophic levels

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

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

Epipelagic food chains usually have many steps and are generally longer than in other ecosystems

Tropical usually have more levels than colder waters

Epipelagic food chains usually have many steps and are generally longer than in other ecosystems

Tropical usually have more levels than colder waters

Epipelagic is an exception to the 10% rule

Herbivores pass on 20% and the carnivores pass on more than 10% also

Epipelagic is an exception to the 10% rule

Herbivores pass on 20% and the carnivores pass on more than 10% also

Patterns of ProductionPatterns of Production

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

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

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

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

Phytoplankton need 2 main things to perform

photosynthesis:

Phytoplankton need 2 main things to perform

photosynthesis:

SunlightSupply of essential nutrients

SunlightSupply of essential nutrients

       

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.

Ocean ProductivityOcean Productivity

Light LimitationLight 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

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

NutrientsNutrients

Nitrogen, iron and phosphorus play a major part in controlling primary production

Nitrogen is most often the limiting nutrient

Most nutrients come from recycling

Nitrogen, iron and phosphorus play a major part in controlling primary production

Nitrogen is most often the limiting nutrient

Most nutrients come from recycling

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

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

Seasonal PatternsSeasonal 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

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

UpwellingUpwelling

Caused by Ekman TransportOccur 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

Caused by Ekman TransportOccur 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

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

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