Chapter 15

Chapter 15Chapter 15

Life Near the SurfaceLife Near the Surface


• Pelagic – water column away from Pelagic – water column away from bottom or shorebottom or shore

• Epipelagic – sea surface to depth of Epipelagic – sea surface to depth of about 200 meters about 200 meters – The epipelagic can be divided into (1) The epipelagic can be divided into (1)

neritic waters over the continental shelf neritic waters over the continental shelf and (2) oceanic waters that are not over and (2) oceanic waters that are not over the continental shelfthe continental shelf


• Epipelagic oceanic ecosystems:Epipelagic oceanic ecosystems:– Warmest portion of the water columnWarmest portion of the water column– Most well lit portion of the water column Most well lit portion of the water column

(light can be limiting in high latitudes and (light can be limiting in high latitudes and at night, however)at night, however)

– There are vast stretches of water that There are vast stretches of water that support primary production support primary production

– This primary production support organisms This primary production support organisms in this community as well as organisms in in this community as well as organisms in other communities via water currentsother communities via water currents


• Disadvantages of the Epipelagic Disadvantages of the Epipelagic oceanic ecosystem:oceanic ecosystem:– No substrate for attachmentNo substrate for attachment– No bottom for burrowing or deposit No bottom for burrowing or deposit

feedingfeeding– Places to hide from predators are Places to hide from predators are

extremely limited and prey often can extremely limited and prey often can spot predatorsspot predators


• Plankton:Plankton:– Thrive in the epipelagicThrive in the epipelagic– Plankton are organisms that cannot fight Plankton are organisms that cannot fight

against the prevailing water currentsagainst the prevailing water currents– These organisms may be microscopic or These organisms may be microscopic or

notnot– Plankton are classified in numerous ways Plankton are classified in numerous ways

including by size, by trophic status and by including by size, by trophic status and by the length of time spent in the planktonthe length of time spent in the plankton

Plankton Division by Size Plankton Division by Size (Know (Know Net)Net)

Plankton Division by Time in Plankton Division by Time in the Planktonthe Plankton

• HoloplanktonHoloplankton – – the entire life the entire life of the organism of the organism is spent in the is spent in the planktonplankton

• MeroplanktonMeroplankton – – spend only a spend only a portion of their portion of their life as plankton life as plankton (larvae of (larvae of molluscs (a), molluscs (a), brittlestars (b), brittlestars (b), sea stars (c), sea stars (c), polychaetes (d) polychaetes (d) crustaceans(e) crustaceans(e) and fishand fish

Plankton Classification by Plankton Classification by Trophic StatusTrophic Status

• PhytoplanktonPhytoplankton – plankton that generate – plankton that generate energy by means of primary production energy by means of primary production (autotrophs)=cyanobacteria, diatoms, (autotrophs)=cyanobacteria, diatoms, dinoflagellates, green algae, red algae, dinoflagellates, green algae, red algae, brown algaebrown algae

• ZooplanktonZooplankton – plankton that are – plankton that are heterotrophs=ciliates, radiolarians, heterotrophs=ciliates, radiolarians, foramniferans, copepods, tunicates, foramniferans, copepods, tunicates, pteropods (gastropod) and larvaepteropods (gastropod) and larvae

PhytoplanktonPhytoplankton

• DiatomsDiatoms– Mainly reproduce by Mainly reproduce by

_____ (a form of asexual _____ (a form of asexual reproduction)reproduction)

– Extremely important Extremely important primary producersprimary producers

– Common in all marine Common in all marine waters waters

– May be solitary cells or a May be solitary cells or a colony of cellscolony of cells

– Can be pennate Can be pennate (elongate) or centric (elongate) or centric (circular)(circular)


• DinoflagellatesDinoflagellates– Each of the 1200 species has unique shape Each of the 1200 species has unique shape

reinforced by plates of cellulosereinforced by plates of cellulose– Two _____ in grooves on body that produce spinning Two _____ in grooves on body that produce spinning

motionmotion– Also reproduce by cellular divisionAlso reproduce by cellular division– Some are bioluminescentSome are bioluminescent– Some are toxic such as the species that cause ____ Some are toxic such as the species that cause ____

Tide or Tide or PfiesteriaPfiesteria– they are particularly prevalent in warm waters and they are particularly prevalent in warm waters and

“bloom” readily when nutrients are plentiful“bloom” readily when nutrients are plentiful


• CyanobacteriaCyanobacteria– Some can go through nitrogen fixation which Some can go through nitrogen fixation which

improves growth in low nutrient conditionsimproves growth in low nutrient conditions– Also an extremely important primary producerAlso an extremely important primary producer– Many grow in filamentous colonies with other Many grow in filamentous colonies with other

cyanobacterial cellscyanobacterial cells– Other are solitary cellsOther are solitary cells

ZooplanktonZooplankton

• CopepodsCopepods– Small Small

crustaceanscrustaceans– Dominate the Dominate the

zooplankton, zooplankton, perhaps making perhaps making up to 70% of up to 70% of zooplanktonzooplankton

– Copepods feed on Copepods feed on phytoplankton as phytoplankton as well as other well as other zooplanktonzooplankton

– They, in turn, They, in turn, serve as a major serve as a major source of food for source of food for other organismsother organisms


• Other zooplankton include a variety of ciliates Other zooplankton include a variety of ciliates and other protists that move by way of and other protists that move by way of pseudopods such as foraminiferans and pseudopods such as foraminiferans and radiolarians. radiolarians.

Foramniferan catching a copepod in its long, thin pseudopods

Zooplankton-TunicatesZooplankton-Tunicates• (Salps (top right) and (Salps (top right) and

larvaceans (bottom larvaceans (bottom right)) are right)) are pelagic pelagic tunicates tunicates that can that can utilize mucous nets to utilize mucous nets to capture food particlescapture food particles


• Pteropods are Pteropods are planktonic molluscs planktonic molluscs (gastropods)(gastropods)

• The foot is modified The foot is modified into two parts that into two parts that serve as “wings” used serve as “wings” used for swimmingfor swimming

• Can be found in Can be found in epipelagic or deeper epipelagic or deeper waterswaters

• Eat phytoplankton and Eat phytoplankton and other zooplanktonother zooplankton


• Jellyfish and comb jellies are not small organismsJellyfish and comb jellies are not small organisms

• However, they are considered by some biologists However, they are considered by some biologists to be plankton because they cannot fight the to be plankton because they cannot fight the prevailing water currents in most casesprevailing water currents in most cases

• Both organisms are carnivorousBoth organisms are carnivorous

Life in the EpipelagicLife in the Epipelagic

• Living in this environment means Living in this environment means finding ways to STAY AFLOATfinding ways to STAY AFLOAT

• This can be accomplished in various This can be accomplished in various ways including air or lipid filled ways including air or lipid filled compartments (increases buoyancy) compartments (increases buoyancy) or by increasing surface area and or by increasing surface area and “drag”“drag”

Increasing Drag and Surface Increasing Drag and Surface AreaArea

• Some organisms Some organisms increase their surface increase their surface area by being flat (as area by being flat (as seen top right)seen top right)

• Others have a variety Others have a variety of spines or of spines or appendages to appendages to increase their surface increase their surface area (bottom right)area (bottom right)

• In both cases, In both cases, increasing the surface increasing the surface area promotes “drag” area promotes “drag” or water resistance or water resistance which helps keep which helps keep these organisms these organisms afloatafloat

Increasing BuoyancyIncreasing Buoyancy

• Some organisms increase buoyancy by Some organisms increase buoyancy by containing droplets or compartments of containing droplets or compartments of lipid which tends to floatlipid which tends to float

• Lipids are used in this way by diatoms, Lipids are used in this way by diatoms, copepods and many larval formscopepods and many larval forms

• Other organisms trap air in various Other organisms trap air in various structures or compartments to increase structures or compartments to increase buoyancy buoyancy

• Such organisms include cyanobacteria, Such organisms include cyanobacteria, cnidarians and even fish (swim bladder)cnidarians and even fish (swim bladder)

NektonNekton

• Nekton are organisms that can fight Nekton are organisms that can fight against the prevailing water current against the prevailing water current and purposefully move in any and purposefully move in any direction they choosedirection they choose

• Examples of nekton found in the Examples of nekton found in the pelagic zone are fish, sea turtles and pelagic zone are fish, sea turtles and sea snakes, marine mammals, sea snakes, marine mammals, cephalopods, and some larger cephalopods, and some larger crustaceans.crustaceans.

Predation and Protection from Predation and Protection from PredationPredation

• Since organisms have virtually no Since organisms have virtually no places to hide, they must have other places to hide, they must have other means for finding prey or avoiding means for finding prey or avoiding being preybeing prey

• Fast swimming, protective coloration, Fast swimming, protective coloration, migrations and a variety of sense migrations and a variety of sense organs are used to accomplish thisorgans are used to accomplish this

Sense OrgansSense Organs

• Eyes – Eyes – – eyes can be used to form images or eyes can be used to form images or

simply to sense light/dark or patternssimply to sense light/dark or patterns– Most organisms is this environment Most organisms is this environment

have well developed eyeshave well developed eyes– Eyesight is used to capture prey, avoid Eyesight is used to capture prey, avoid

being prey, find mates and stay in being prey, find mates and stay in groups (as applicable)groups (as applicable)

Sense Organs – Remote Sense Organs – Remote SensingSensing

• Both Both cartilaginous and cartilaginous and bony fish have a bony fish have a _____ line for _____ line for remote sensing remote sensing of water of water movement that movement that can indicate prey can indicate prey or predators are or predators are nearbynearby

Sense Organs – Remote Sense Organs – Remote SensingSensing

• Dolphins and other cetaceans use their Dolphins and other cetaceans use their _____ for echolocation to navigate pelagic _____ for echolocation to navigate pelagic waterswaters

• They also use the melon to find prey and They also use the melon to find prey and avoid predatorsavoid predators

Protective ColorationProtective Coloration

• To blend in with their environment, To blend in with their environment, organisms can have different types organisms can have different types of protective coloration:of protective coloration:– CountershadingCountershading– CamouflageCamouflage– TransparencyTransparency

CountershadingCountershading

• In _____ organisms, In _____ organisms, the ventral side of the the ventral side of the organism is lighter organism is lighter than the dorsal sidethan the dorsal side

• This aids the organism This aids the organism in “blending in” in “blending in” because if they are because if they are seen from above, seen from above, their darker dorsal their darker dorsal side blends in with the side blends in with the darker water belowdarker water below

• However, if they are However, if they are seen from below, their seen from below, their lighter ventral side lighter ventral side blends in with the blends in with the better lit water abovebetter lit water above

CamouflageCamouflage• As an example, the sargassum fish, As an example, the sargassum fish, Histrio histrioHistrio histrio, ,

is an example of a pelagic organism that uses is an example of a pelagic organism that uses camouflage for protection from predatorscamouflage for protection from predators

• This fish looks very much like the This fish looks very much like the SargassumSargassum macroalgae it calls home macroalgae it calls home

TransparencyTransparency

• Another way to hide is to lack coloration Another way to hide is to lack coloration completelycompletely

• This is the case with most jellyfish, comb This is the case with most jellyfish, comb jellies, and pelagic tunicates, as well as jellies, and pelagic tunicates, as well as many zoo- and phytoplanktonmany zoo- and phytoplankton

SwimmingSwimming

• Epipelagic predators must be able to swim Epipelagic predators must be able to swim quickly to capture preyquickly to capture prey

• This is accomplished by a streamlined body to This is accomplished by a streamlined body to reduce drag and a strongly forked caudal tail to reduce drag and a strongly forked caudal tail to increase thrust.increase thrust.

Pelagic Food WebsPelagic Food Webs• The diagram to The diagram to

the right shows the right shows one example of one example of a food web and a food web and how the web how the web changes over changes over the life cycle of the life cycle of one speciesone species

• This is a This is a common common feature of feature of pelagic food pelagic food webs – an webs – an organism will organism will not feed on the not feed on the same type of same type of organisms organisms throughout their throughout their lifelife

Where do the Food Webs Where do the Food Webs Begin?Begin?

• All pelagic food webs begin with All pelagic food webs begin with either phytoplankton, either directly either phytoplankton, either directly or as dissolved organic matter or as dissolved organic matter (DOM), which comes from viral (DOM), which comes from viral action.action.

Limitations to Primary Limitations to Primary ProductivityProductivity

• Primary production can be limited by Primary production can be limited by light – even though there is normally light – even though there is normally plenty of light in the pelagic plenty of light in the pelagic environment, light is not present at environment, light is not present at night or for long stretches in high night or for long stretches in high latitudes at certain times of the yearlatitudes at certain times of the year

Limitations to Primary Limitations to Primary ProductivityProductivity

• Primary production can also be Primary production can also be limited by essential nutrients such as limited by essential nutrients such as nitrogen (most important) or nitrogen (most important) or phosphatephosphate

• Bacteria are important “recyclers” of Bacteria are important “recyclers” of these nutrients as they break down these nutrients as they break down organic matter and cyanobacteria fix organic matter and cyanobacteria fix nitrogennitrogen

Areas of UpwellingAreas of Upwelling• The heating and The heating and

cooling of surface cooling of surface waters can cause waters can cause deeper water to be deeper water to be brought to the brought to the surface in certain surface in certain areasareas

• The diagram to the The diagram to the right shows this right shows this process, called process, called upwellingupwelling

• Upwelling brings Upwelling brings vital nutrients to vital nutrients to the surface (these the surface (these nutrients were lost nutrients were lost from the pelagic as from the pelagic as DOM, fecal matter, DOM, fecal matter, and mucous)and mucous)

• Primary production Primary production is higher in areas of is higher in areas of upwellingupwelling

Documents

Chapter 15