1. Pelagic Systems
2. Epipelagic Environment
3. Phytoplankton
4. Planktonic Bacteria and Protozoa
5. Zooplankton
6. Epipelagic Nekton

Pelagic Communities

1. Communities found in the water column
2. Pelagic communities are made up entirely of plankton and nekton
3. Interact with the physical environment of the water column

Epipelagic Zone

1. Surface waters to 200 meters
2. Photic
3. Temperatures near maximum
4. Salinity fluctuates most
5. Dissolved oxygen concentration near maximum
6. Pressure near minimum (less than 20 atm)
7. Nitrogen and phosphorus concentrations near minimum

Neritic Zone

1. Definition: The Neritic Zone is the coastal waters overlying the continental shelf
2. Nutrients from land
3. Very productive
4. Abundant plankton

Oceanic Zone

1. Definition: The Oceanic Zone is the open waters beyond the continental shelf
2. Little nutrients
3. Clear and unproductive
4. Relatively little plankton

Common Characteristics of Phytoplankton

1. Microscopic cells
2. Singular, clusters or chains
3. Contain chloroplasts

Producers of Food

1. Photoautotrophs
2. Base of Pelagic Food Web
3. Growth and reproduction occurs in the surface waters where there is enough light for photosynthesis

Adaptations Retard Sinking

1. Small size
2. Disc shapes
3. Chaining and spiraling
4. Projections
5. Flagella
6. Oil Droplets

Diatom Cell Structure

1. Unicellular; chains or clusters of cells
2. Golden brown color
3. Pillbox shape
4. Siliceous shells (shells collect on sea floor forming oozes)

Diatom Habits

1. Move by gliding
2. Most abundant in cool waters
3. Benthic or planktonic

Dinoflagellate Cell Structure

1. Unicellular
2. Reddish Brown color
3. Cellulose cell wall

Dinoflagellate Habits

1. Move with flagella
2. Planktonic
3. Red Tides are dinoflagellate blooms of tremendous proportions

Dinoflagellate Special Defenses

1. Neurotoxin production
2. Biolumenescence

Neurotoxins

1. Nerve poisons
2. Cause fish kills
3. Paralytic shellfish poisoning
4. Ciguatera poisoning

Biolumenescence

1. Biological production of light
2. Triggered mechanically
3. Startle defense against predators

Common Characteristics of Planktonic Bacteria and Protozoa

1. Microscopic
2. Single cells

Heterotrophs

1. Heterotrophs = consume premade food

A. Decomposers that absorb organic molecules (may be preceded by extacellular digestion)

B. Ingesters that feed on other plankton

Bacterial Plankton

1. Tiny, simple, prokaryotic cells without a membrane bound nucleus or specialized organelles
2. Most are microscopic decomposers

Protozoan Zooplankton

1. Microscopic size
2. Unicellular, eukaryotic heterotrophs that ingest food and digest it in intracellular vacuoles or decomposers that digest food extracellularly
3. Two important groups: Foraminiferans and Radiolaria

Foraminiferans

1. Calcareous shells form oozes
2. Pseudopods for feeding

Radiolarians

1. Siliceous shells form oozes
2. Pseudopods for feeding

Common Characteristics of Zooplankton

1. Vary in size from barely macroscopic to extremely large
2. Complex multicellular invertebrates

Heterotrophs

1. Heterotrophs = consume premade food

A. Ingesters that feed on other plankton and nekton

Animal Plankton (Zooplankton)

1. Multicellular, eukaryotic heterotrophs that ingest food and digest it in cavities or tracts inside their bodies
2. Many animal phyla are represented
3. Individuals vary in size from millimeters to meters in length

Types of Zooplankton

1. Holoplankton
2. Meroplankton
3. Demersal zooplankton
4. Gelatinous zooplankton

Holoplankton

1. Holoplankton=organisms whose entire life-cycle is planktonic
2. Make up the majority of the zooplankton in numbers and species
3. 95 percent of zooplankton are holoplanktonic copepods
4. Copepods outnumber all other marine animals combined
5. Krill a type of shrimp-like crustacean is a regionally abundant holoplankter
6. Arrow worms are important predators copepod predators

Gelatinous Holoplankton

1. Holoplankton with gelatinous translucent tissues
2. Tissue densities approximately equal to that of seawater
3. Include medusae, siphonophores, pteropods, larvaceans, salps

Meroplankton

1. Meroplankton are the planktonic larvae of benthic or nektonic adults
2. Most abundant in shallow waters near shore
3. Developing embryos of benthic invertebrates
4. Fish eggs and larvae

Demersal Zooplankton

1. Spend part of their time in the water and part in or on the bottom
2. Often swim up from the bottom at night

Adaptations to Retard Sinking

1. Long appendages
2. Gelatinous tissues
3. Oils and waxes
4. Gas-filled floats
5. Swimming

Diurnal Vertical Migrations

1. Movements upward and downward on a daily basis
2. Rise at night and sink by day

Value of Migrations

1. Zooplankton move downward by day to avoid visual predators such as fish and squid
2. Herbivorous zooplankton swim upward at night to feed on phytoplankton and carnivorous zooplankton follow their prey upward

Cost of Migrations

1. Migrating zooplankton expend a great deal of energy when swimming upward
2. Energy expended by swimming is replaced when feeding on rich food resources near the surface
3. The cost of swimming up every night is exceeded only by the risk of being preyed upon if the zooplankton were to remain at the surface permanently

Non-Migraters

1. Some zooplankton do not migrate
2. Some remain at the surface
3. Some remain at depth

Types of Epipelagic Nekton

1. Cephalopods: squids
2. Fishes: Clupieds, Engradulids & Scrombroids

Adaptations of Epipelagic Nekton

1. Adapted for living in a relm of blue water
2. There is enough light for visual predators to see prey
3. There are no solid structures to hide in or near

Protection

1. Transparency in squids
2. Vertical migrations
3. Schooling is common
4. Countershading
5. Speed

Speed Swimming

1. Streamlined bodies often fusiform or laterally compressed
2. Small scales or scaleless
3. Lunate tails, narrow caudal peduncles and finlets
4. Strong swimming muscles

Swimming Musculature

1. Higher proportion of red muscle
2. Red muscle rich in myoglobin can store oxygen for long sustained effort
3. White muscle with less myoglobin for short bursts

Sensory adaptations

1. Must have good senses to detect predators
2. Squids, Fishes and Marine Mammals have good eyesight to find prey and watch for predators
3. Whales have ecolocation
4. Fishes have lateral lines for vibration detection

Clupeid Fishes

1. Important in temperate epipelagic food webs
2. Herring, Menhaden, Shad and Sardines
3. Silvery with dark blue or green backs
4. Laterally compressed, deep body with forked tail
5. Dorsal fatty ridge and ventral scutes (saw belly)
6. Terminal, upturned mouth
7. Planktivorous: filter feeding with long gill rakers
8. Schooling

Engraulid Fishes

1. Important in tropical epipelagic food webs
2. Anchovies
3. Silvery with lateral stripe
4. Long, narrow body with forked tail
5. No fatty ridge or scutes
6. Bulbous snout and inferior mouth
7. Planktivorous: filter feeding gill rakers
8. Schooling

Scrombroid Fishes

1. Tunas, mackerels and billfishes
2. Swim continuously
3. May travel thousands of miles during a lifetime
4. Tunas and billfishes are adapted for endurance swimming and many have migration patterns of oceanic proportions

Adaptations in Scromboids

1. Bill helps in slipping through water
2. Grooves for retracting fins
3. Finlets, keel and lunate tail
4. Reduced swim bladder
5. Reduced gill ventilating musculature & grooved tongue
6. Counter current heat exchange