Chapter 15 Life Near the Surface Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

Life Near the Surface Pelagic realm – water column away from the bottom Pelagic realm – water column away from the bottom Epipelagic – zone that includes the sea surface to a depth of about 200 meters Epipelagic – zone that includes the sea surface to a depth of about 200 meters –divided into: neritic - waters over the continental shelf and neritic - waters over the continental shelf and oceanic - waters beyond the continental shelf oceanic - waters beyond the continental shelf

Life Near the Surface Epipelagic: Epipelagic: –Warmest portion of the water column –Most well lit portion of the water column (photic zone) but light can be limiting in high latitudes and at night –Vast stretches of water that support primary production –This primary production support organisms in the epipelagic as well as organisms in other communities by way of water currents

Life Near the Surface Limitations of the epipelagic: Limitations of the epipelagic: –No substrate for attachment –No bottom for burrowing or deposit feeding –Places to hide from predators are extremely limited –Predators cannot easily catch their prey for the same reason

Life Near the Surface Plankton Plankton –Thrives in the epipelagic –Plankton includes all organisms that cannot swim against the prevailing water currents –Many are microscopic –Plankton is classified by size, by trophic level, or by the length of time spent in the plankton

Plankton Division by Size

Plankton Classification by Time Spent as Plankton Holoplankton – Holoplankton – the entire life of the organism is spent in the plankton Meroplankton – Meroplankton – only a portion of the life of the plankton is spent in the plankton (larvae of fishes, molluscs, crustaceans, etc.)

Plankton Classification by Role in Food Chain Phytoplankton – plankton that performs photosynthesis (primary production: autotrophs) Phytoplankton – plankton that performs photosynthesis (primary production: autotrophs) Zooplankton – plankton consisting of heterotrophs (consumers) Zooplankton – plankton consisting of heterotrophs (consumers)

Phytoplankton Diatoms Diatoms –Extremely important primary producers –Common in all marine waters but tend to be more important in cold water –May be solitary cells or a colony of cells (see “Unicellular Algae,” Ch. 5)

Phytoplankton Dinoflagellates Dinoflagellates –Each of the 1200 species has unique shape that is reinforced by plates of cellulose (see “Unicellular Algae,” Ch. 5) –Two flagella in grooves on body that produce spinning motion –Some are bioluminescent –Some are toxic such as Pfiesteria and the species that cause red tides –particularly prevalent in warm waters and “bloom” readily when nutrients are plentiful

Phytoplankton Cyanobacteria Cyanobacteria –Some able to carry out nitrogen fixation (see “Prokaryotes,” Ch. 5) –Important primary producers –More abundant in the pelagic than originally thought –Many grow in filamentous colonies; others are solitary

Phytoplankton Coccolithophorids Coccolithophorids –Part of nanoplankton (small size) –Occur in neritic and oceanic waters –Plates of calcium carbonate (see Fig. 5.10) Silicoflagellates Silicoflagellates –Star-shaped skeleton of silica (see Fig. 5.9) –Two flagella of varying lengths

Major Groups of Marine Phytoplankton [Insert Box 15.1 in 10 th ed.] [Insert Box 15.1 in 10 th ed.]

Zooplankton: Holoplankton Copepods Copepods –Small crustaceans –Dominant, perhaps making up to 70% of zooplankton –Feed on phytoplankton as well as other zooplankton –Serve, in turn, as a major source of food for other consumers Other crustacean zooplankton: Krill – important food for baleen whales and other consumers

Zooplankton: Holoplankton Salps (top) and larvaceans (below) are pelagic tunicates that use mucous nets to capture food particles Salps (top) and larvaceans (below) are pelagic tunicates that use mucous nets to capture food particles Salps can be solitary or occur as large floating colonies Salps can be solitary or occur as large floating colonies [insert Fig in 10 th ed.]

Zooplankton: Holoplankton Pteropods are planktonic molluscs Pteropods are planktonic molluscs The molluscan foot is modified as “wings” The molluscan foot is modified as “wings” Reduced shell Reduced shell Can be found in epipelagic or deeper waters Can be found in epipelagic or deeper waters Feed on phytoplankton and other zooplankton Feed on phytoplankton and other zooplankton

Zooplankton: Holoplankton Arrow worms (chaetognaths) are fish-like predators of smaller zooplankton (see Fig. 7.17) Arrow worms (chaetognaths) are fish-like predators of smaller zooplankton (see Fig. 7.17) Jellyfishes and comb jellies are considered as plankton because they mostly drift in the currents Jellyfishes and comb jellies are considered as plankton because they mostly drift in the currents - Carnivores - Carnivores

Meroplankton The meroplankton only spends a portion of their life as plankton The meroplankton only spends a portion of their life as plankton Include larvae of animals that are part of nekton as adults (fishes), or part of the benthos as adults (molluscs, polychaete worms, crustaceans, echinoderms, and many kinds of invertebrates) Include larvae of animals that are part of nekton as adults (fishes), or part of the benthos as adults (molluscs, polychaete worms, crustaceans, echinoderms, and many kinds of invertebrates)

Nekton Nekton includes organisms that swim against the currents and purposefully move in any direction they choose Nekton includes organisms that swim against the currents and purposefully move in any direction they choose Examples: fishes, penguins, squids, sea turtles, marine mammals Examples: fishes, penguins, squids, sea turtles, marine mammals

Life in the Epipelagic Living in the epipelagic means finding ways to stay afloat Living in the epipelagic means finding ways to stay afloat This can be accomplished by increasing buoyancy by means of accumulating lipids or air or by increasing surface area, or drag This can be accomplished by increasing buoyancy by means of accumulating lipids or air or by increasing surface area, or drag

Increasing Drag and Surface Area Some organisms increase their surface area by being flat Some organisms increase their surface area by being flat Others have a variety of spines or appendages to increase their surface area Others have a variety of spines or appendages to increase their surface area In both cases, increasing the surface area promotes drag or water resistance which helps keep bodies from sinking In both cases, increasing the surface area promotes drag or water resistance which helps keep bodies from sinking

Increasing Buoyancy Some organisms increase buoyancy by storing droplets of lipids, which tend to float because they are less dense than water Some organisms increase buoyancy by storing droplets of lipids, which tend to float because they are less dense than water Such organisms include diatoms, copepods and many planktonic larvae Such organisms include diatoms, copepods and many planktonic larvae Some organisms have pockets of air that increase buoyancy: cyanobacteria, cnidarians, fishes (swim bladders) Some organisms have pockets of air that increase buoyancy: cyanobacteria, cnidarians, fishes (swim bladders)

The Floaters Floating organisms are classified as neuston (float just beneath surface) and pleuston (some parts float above and some below surface) Floating organisms are classified as neuston (float just beneath surface) and pleuston (some parts float above and some below surface) Portuguese man-of-war (Physalia) and the predatory snail Janthina (bottom left of photo) Portuguese man-of-war (Physalia) and the predatory snail Janthina (bottom left of photo) By-the-wind-sailor (Velella) By-the-wind-sailor (Velella)

Predation and Protection from Predation Because pelagic animals have virtually no places to hide, they must have other means for finding prey or avoiding being eaten Because pelagic animals have virtually no places to hide, they must have other means for finding prey or avoiding being eaten Fast swimming, protective coloration, vertical migrations, and a variety of sense organs are adaptations to accomplish this Fast swimming, protective coloration, vertical migrations, and a variety of sense organs are adaptations to accomplish this

Sense Organs Eyes Eyes –Can be used to form images or simply to sense light/dark or patterns –Most pelagic animals have well-developed eyes –Eyesight is used to capture prey, avoid being eaten, find mates, and, in some, to stay in groups

Sense Organs – Remote Sensing Cartilaginous and bony fishes have a lateral line for sensing of prey or predators Cartilaginous and bony fishes have a lateral line for sensing of prey or predators Dolphins and other cetaceans use echolocation Dolphins and other cetaceans use echolocation

Protective Coloration To blend in with their environment, organisms can have different types of protective coloration: To blend in with their environment, organisms can have different types of protective coloration: –Countershading –Camouflage –Transparency

Countershading Countershading - dorsal surface is darker than the ventral surface Countershading - dorsal surface is darker than the ventral surface

Transparency One way to hide is to lack coloration and become transparent (see Fig ) One way to hide is to lack coloration and become transparent (see Fig ) This is the case with many jellyfishes, comb jellies, salps, larvaceans, and in some zooplankton This is the case with many jellyfishes, comb jellies, salps, larvaceans, and in some zooplankton

Swimming Epipelagic predators must be able to swim quickly and fast to capture prey Epipelagic predators must be able to swim quickly and fast to capture prey This is accomplished by several adaptations in pelagic fishes such as tunas: a streamlined body to reduce drag, a strongly forked caudal tail to increase thrust, and a narrow caudal peduncle to concentrate energy on the caudal fin (see Box 15.2, “Swimming Machines”) This is accomplished by several adaptations in pelagic fishes such as tunas: a streamlined body to reduce drag, a strongly forked caudal tail to increase thrust, and a narrow caudal peduncle to concentrate energy on the caudal fin (see Box 15.2, “Swimming Machines”)

Muscles of Pelagic Fishes “Warm blooded” – heat energy generated by muscle activity is carried back in returning blood (rete mirabile) “Warm blooded” – heat energy generated by muscle activity is carried back in returning blood (rete mirabile) Red muscles: high concentration of myoglobin, which stores extra oxygen Red muscles: high concentration of myoglobin, which stores extra oxygen

[insert Fig in 10 th ed.]

Vertical Migrations Some pelagic animals move into deeper waters during the day to avoid predators Some pelagic animals move into deeper waters during the day to avoid predators At night, they move back into shallower waters to feed on phytoplankton At night, they move back into shallower waters to feed on phytoplankton This predator avoidance comes with a cost: it takes more energy to migrate than to stay in one place This predator avoidance comes with a cost: it takes more energy to migrate than to stay in one place

Epipelagic Food Webs Typical epipelagic food web: an animal will not feed on the same type of organisms throughout its life Typical epipelagic food web: an animal will not feed on the same type of organisms throughout its life

Limitations to Primary Production Nutrients, particularly nitrate (most important) and phosphate Nutrients, particularly nitrate (most important) and phosphate Light, even when there is normally plenty of light in the pelagic environment, but absent at night or for long stretches in high latitudes in winter (seasonal patterns) Light, even when there is normally plenty of light in the pelagic environment, but absent at night or for long stretches in high latitudes in winter (seasonal patterns)

Limitations to Primary Production Bacteria, viruses, and other microorganisms are important recyclers of nutrients in the epipelagic (microbial loop) Bacteria, viruses, and other microorganisms are important recyclers of nutrients in the epipelagic (microbial loop)

Areas of Upwelling The heating and cooling of surface waters can cause deeper water to be brought to the surface in certain areas (upwelling) The heating and cooling of surface waters can cause deeper water to be brought to the surface in certain areas (upwelling) Upwelling brings vital nutrients to the surface, nutrients that were lost from the pelagic as DOM, fecal material, mucous, etc. Upwelling brings vital nutrients to the surface, nutrients that were lost from the pelagic as DOM, fecal material, mucous, etc. Primary production is higher in areas of upwelling Primary production is higher in areas of upwelling

Types of Upwelling Coastal upwelling Coastal upwelling Equatorial upwelling – surface water moves away on opposite sides of the Equator as a result of the Coreolis effect (see Fig ) Equatorial upwelling – surface water moves away on opposite sides of the Equator as a result of the Coreolis effect (see Fig )

El Nio-Southern Oscillation (ENSO) El Niño-Southern Oscillation (ENSO) El Niño occurs as upwelling along the Pacific coast of South America decreases, causing a warming of the ocean surface El Niño occurs as upwelling along the Pacific coast of South America decreases, causing a warming of the ocean surface This decrease in the coastal upwelling characteristic of this region results in a sharp decrease in primary production This decrease in the coastal upwelling characteristic of this region results in a sharp decrease in primary production This drop in primary production causes effects through the food chain in an otherwise highly productive region: drop in plankton populations, fish catches, seabird populations This drop in primary production causes effects through the food chain in an otherwise highly productive region: drop in plankton populations, fish catches, seabird populations ENSO – global effects that go beyond El Niño (see Fig ) ENSO – global effects that go beyond El Niño (see Fig )