Life in the Open Sea

(terms to know)

• Pelagic: in the Water Column
• Neritic: over the continental shelf
• Oceanic: beyond the continental shelf
• Epipelagic: upper 200m (warmest most light)
• Euphotic Zone: range of depth with enough light for photosynthesis not epipelagic
• Plankton: organisms that drift with currents (animals& micro algae, weak swimmers at best.

phytoplankton 

zooplankton

• phytoplankton: photosynthetic plankters
• zooplankton: animal plankters
• also a habitat "the plankton"

Nekton

Primary Production in Open Ocean

• CO2 Turns into organic molecules (aka photosynthesis or chemosynthesis
• performed by plankton 
• only in euphotic zone
• all food originates in the top layer
• more primary production by plankton than all terrestrial plants!!!

Requirements for Primary Production

• light, nutrients (nitrate, phosphate)
• sites of high primary production: 
• neritic: coastal upwelling
• oceanic: equatorial upwelling

What limits Primary Production?

• Light: daily and seasonal variation
• latitudinal variation affects depth of euphotic zone
• nutrient availability
• limiting nutrient: in shortest supply, often nitrate or iron

Phytoplankton 

• 95% of primary production in open ocean done by plankton
• they are mostly unicellular and small but found in HUGE numbers
• Other major players: diatoms, dinoflagellates cyanobacteria (some fix nitrogen)

Phytoplankton Blooms

• aka "Red Tide"
• most reproduce asexually= rapid population growth
• population explosion of a single species (usually diatom, dinoflagellate)
• cell division is greater than grazing by herbivores
• most blooms aren't toxic 

Harmful Algal Blooms

(HAB's)

• phytoplankters produce toxins
• Toxins ingested by filter feeders (mussels etc.)
• Passed to higher trophic levels (fishes, birds, mammals)
• Amnesia shellfish poisoning (ASP)
• produced by a diatom
• Paralytic Shelfish Poisoning (PSP)
• produced by a dinoflagellate
• Diarrhetic SHellfish Poisoning (DSP)
• produced by a dinoflagellate (problem with fisheries.
• Pfisteria 
• dinoflagellate that kills fish, attacks skin
• the toxin can also be inhaled which causes delusion, hallucinations. 

Zooplanton

• Represent every animal Phylum (extremely diverse)
• Includes heterotrophic protozoans
• Holoplankton:entire life in plankton
• Meroplankton: part of life in plankton (Crustacean holoplankton)
• Crustacean: "insects" of the sea
• the most numerous animals, feed on phytoplankton. eaten by everyone (important in pelagic food webs) 
• Transfer Energy from primary production to higher trophic levels.  

Krill

• feed on phytoplankton, small zooplankton 
• eaten by fish, squid, seabirds, mysticetes.

Nekton 

• Nekton: swim against currents
• fishes, squid, vertebrates 
• many have planktonic larvae
• planktioveres feed on plankton

Neuston and Pleuston

• Neuston: animals that live at surface
• all of body in the water (ex: nudibranchs)
• Pleuston: subset of neuston
• body in air and water
• specialized habitat- aerial and marine stresses
• No protection from UV
• blue pigments used as sunscreen