Worksheet 12-1: The Plankton – Drifters of the Open Ocean

Reading pages 367-388 in An Introduction to the World’s Oceans

  1. Where does the word “plankton” come from?
  2. The smallest plankton that are less than 0.005 mm in diameter are called ______
  3. Plankton between 0.005 and 0.007 mm in diameter are called ______
  4. Plankton between 0.007 and 1 mm in diameter are called ______
  5. Why are plankton sometimes called “the grasses of the sea?

Phytoplankton

  1. Phytoplankton are mainly single-celled plants known as ______. They are considered plant-like because they gain their energy through the process of ______.
  2. The largest species of phytoplankton is the seaweed called ______that is found floating in the north Atlantic in the area known as the ______(thousands of tons also washes up on Texas beaches which anyone who’s visited Port Aransas has seen first-hand).
  3. How to diatoms stay afloat in the upper photic zone of the ocean? (i.e. where to they get their buoyancy?)
  4. What do fish that feed on diatoms taste like?
  5. Diatoms that die and settle to the sea floor form silica-rich sediments that are often mined as diatomaceous earth. What are two common uses of diatomaceous earth?
  6. What are two ways in which dinoflagellates differ from diatoms?

Zooplankton

  1. What is the main way that zooplankton are different from phytoplankton? (hint—in terms of feeding)
  2. Zooplankton can move vertically in the water column and can often swim and dart short distances in search of prey. Why are they still considered plankton if they can swim?
  3. The primary food of baleen whales is the zooplankton species known as ______.
  4. Study the drawings of radiolarian plankton in figure 15.10. Based on what you learned in the previous unit, why purpose do you think the long spikes might serve that are found on these animals?
  5. Zooplankton that spend their entire lives as plankton are called ______. Zooplankton that spend only a portion of their lives as plankton are called ______.

A Krill-Based Ecosystem

  1. Most species of fish, birds, and mammals living in the Southern Ocean and Antarctica depend on ______as their food source.
  2. How many tons of krill are whales estimated to eat each year? ______

Practical Considerations – Marine Toxins

  1. When the discoloration has left the water after a PSP red tide, the shellfish may not be safe to eat. Explain why
  2. What times of year are red tide most common?
  3. What is one possible reason why scientists believe that red tides are becoming more common?
  4. How many people are affected each year by Ciguatera Poisoning?

General Study Questions

  1. Why are meroplankton produced in such large numbers?
  2. Patches with abundant populations of zooplankton are frequently separated by patches with sparce populations. How does this help assure survival from predators?
  3. If the krill in the Southern Ocean were heavily harvested for human consumption, explain the possible effects on the rest of the organisms in the area.
  4. Why is a planktonic life-stage important to the survival of species that are part of the benthos as adults (i.e. coral, starfish, mussels)?
  5. How do plankton maintain themselves in a given region of the ocean even though there are currents flowing through that region.
  6. Make a simple food web for the Southern Ocean around Antarctica. Include diatoms, krill, fish, whales, seals, squid, penguins, and sea birds.