Download Subphylum Vertebrata – Early Vertebrates and

Open-sea Ecosystems and Plankton
 Oceanic Zone: ocean beyond continental shelves
 Primary Productivity: limited to phytoplankton (no seaweeds or
detritus); in open sea, most phytoplankton in neuston layer
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Nutrient-poor nature most pronounced in tropics (stable thermocline);
no run-off of nutrients from coasts
Longer food chains than in coastal ecosystems
Low diversity of top predators, but abundance can be high
Many coastal species transit open ocean via major currents
Decomposition of dead organisms as they sink in water column
 Nekton: animals able to swim against ocean currents
 Sharks: silky, dusky, blue, mako, oceanic white-tip, pelagic thresher
sharks
 Bony Fishes: tunas, billfishes, oarfish, mola (most streamlined and
countershaded)
 Others: squids, pelagic red crabs, yellow-bellied sea snake, beaked
whales, common, spotted, and spinner dolphins
 Associations between sea birds, tunas, dolphins: food (baitfish, red
crabs, squid) distributed in patches, difficult to locate
Figure 4-9
Open-sea Ecosystems and Plankton
 Oceanic vs. Coastal Plankton
 Phytoplankton: pico- and nanoplankton dominate (cyanobacteria, coccolithophores) vs. diatoms and dinoflagellates
 Zooplankton: radiolarians, foraminiferans, arrow worms,
and larvaceans dominate vs. copepods and krill
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Holoplankton: plankton for entire life cycle (ex. larvaceans, salps,
pelagic molluscs, radiolarians and forams)
Meroplankton: larval stages in plankton (many inverts and fishes)
 Adaptations: spines, flagella (reduce sinking and
predation), oil droplets and chain formation (reduce
sinking), transparency (anti-predation, from lack of
food?)
Figure 4-12
Figures 4-16 and 5-14
Figure 5-5c
Seafloor Sediments of the Open Sea
 Biogenous Sediments: originate from living organisms
 Siliceous Oozes: from diatoms and radiolarians (with tests
composed of silicon dioxide); dominate in deepest areas
 Calcareous Oozes: from foraminiferans and coccolithophores
(with tests composed of calcium carbonate); dissolution at
carbonate compensation depth (dependent on pressure and
temperature; ~9,000 – 14,000 feet)
 Hydrogenous Sediments: originate from seawater chemistry
(precipitation of solid minerals)
 Ferromanganese Nodules: consist of iron and manganese with
trace amounts of other metals; a potential resource, but
recovery currently too expensive
 Cosmogenous Sediments: originate from outer space; rare,
include cosmic dust; meteor impacts deposit irridium and
lead to formation of microtektites (shocked quartz)
Figures 12-2, 12-3,and 12-4
Figures 12-6 and 12-7
Figures 12-13 and 12-26
Figure 12-25
Figures 12-28 and 12-29
Figure 12-14