Dr. Christian Heesch Teaches About Zooplankton

During his time is graduate school for marine biology, Dr. Christian Heesch spent many hours studying the intricate world of zooplankton. Now that he has graduated and become a working professional in his field, he uses his vast zooplankton knowledge to study the smallest organisms that inhabit the oceans. Here he offers some of his valuable and hard earned information.

  • The term plankton refers to both the phytoplankton and zooplankton that lives in ocean waterways and seas. While phytoplankton is the incredibly small plant material that creates the basis of many food chains, zooplankton are the microscopic organisms like animals that reside near the surface of the water.
  • Both forms of plankton are important to the oceans, yet offer no form of strength on their own. Plankton, for example, cannot swim on its own merit, but is forced to travel wherever the ocean currents send it.
  • Holoplankton is the name given to the permanent members of the plankton family. Some of the most widely recognized permanent plankton organisms are amphipods, dinoflagellates, krill, and diatoms. Others are radiolarians, foraminifera, salps, and copepods.
  • Meroplankton are the temporary or transient members of the plankton realm. These organisms are only considered to be a member of the plankton family when they are in their earliest or youngest stages, such as larval growth. When these organisms grow to maturity, they are no longer a form of plankton, but a full-fledged species of their own. Common meroplankton include the larval forms of sea urchins, fish, marine worms and snails, crustaceans, and sea stars.
  • For taxonomic purposes, zooplankton is classified by its development stage or size. Sizes of zooplankton are separated into six different measurement categories, with picoplankton being the smallest and megaplankton the largest. However, even megaplankton is small compared to the myriad of other creatures that live in the ocean. The sizes for zooplankton classification are as follows.
  • Picoplankton- less than two micrometers in diameter or length.
  • Nanoplankton- 2 to 20 micrometers in diameter or length.
  • Microplankton- 20 to 200 micrometers in diameter or length.
  • Mesoplankton- 0.2 to 20 millimeters in diameter or length.
  • Macroplankton- 20-200 millimeters in diameter or length.
  • Megaplankton- greater than 200 millimeters in diameter or length.
  • Stage classification of zooplankton is determined by whether the organism is a holoplankton or meroplankton, therefore whether it is destined to always be a form of plankton or still growing into its own species.
  • The world of zooplankton is small in stature but plays a large role in the underwater ecosystem. Dr. Christian Heesch explains that the nanoplanktonic flagellates found in zooplankton are tasked with keeping the bacteria levels in water safe and healthy.
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