Plankton – The Basis of the Ocean Food Web
Today we celebrate the little critters of the ocean, the ones you never notice or see highlighted on discovery channel, Blue Planet, or NatGeo. I’m talking, of course, about plankton. These tiny marine organisms are responsible for creating and maintaining practically every ocean ecosystem, and yet most people know so little about them that a recent article in the Epoch Times referred to them as “the tiniest animal in the ocean.” So before I get too much into why we’re talking about plankton, let’s all get to know them a little better.
“Plankton” does not refer to a single animal. The word plankton comes from the Greek word planktos, which roughly translates to “drifter” (technically it’s translated as the adjective “errant,” but the closest noun translation would be “drifter”). The uniting characteristic of all plankton, therefore, is that they are drifters. These organisms are too small to move actively against ocean currents, so they simply drift with them. Therefore, rather than being a taxonomic term like “fish”, “whales”, or even “invertebrates,” “plankton” is simply a term given to those organisms which cannot move against currents.
As you might have guessed, with such a broad definition of plankton we have many different types. Phytoplankton are photosynthetic plankton which form the base of practically every marine ecosystem. Zooplankton are heterotrophic, meaning they must consume other organisms for energy. Within zooplankton you have holoplankton and meroplankton. Holoplankton are organisms that remain planktonic for their entire life cycle, while meroplankton ultimately grow large enough to move against ocean currents. Plankton can also be grouped according to size. Going from largest to smallest, we have Megaplankton, macroplankton, mesoplankton, microplankton, nanoplankton, picoplankton, and femtoplankton.
You may be asking yourself why any of this matters. Well, in addition to definitely being great first date topics no matter how many exes might say otherwise, plankton are incredibly important to the health of our oceans. They undergo what some call the largest migration in the world, when each night they migrate to surface waters to feed. Plankton are also the largest source of food for many secondary consumers such as fish, shrimp, and even whales. Many economically important species of fish, crab, and shrimp go through planktonic larval stages before they become adults. Through photosynthesis, phytoplankton are responsible for creating the majority of earth’s oxygen. Many species of plankton have skeletons or shells made of calcium carbonate. As they die and sink to the ocean floor, some of this calcium carbonate is sequestered in the ocean floor. This sequestered material ultimately helps to reduce atmospheric carbon dioxide, thereby mitigating potential harmful impacts of climate change. Finally, because plankton are smaller and have shorter life cycles than many fish, they are great indicators of ecosystem shifts or climate change that may ultimately prove detrimental to species higher up the food chain.
Sylvia Earle recently said that “life as we know it depends on plankton … not just for the ocean, but for the planet.” She was narrating a new documentary released in July by Jean-Michel Cousteau, son of Jacques Cousteau, titled “The Secret Ocean.” Through this documentary, Earle and Cousteau attempt to bring awareness to these little but vital components of marine ecosystems. And it couldn’t have come at a better time. While many funding agencies are willing to put money towards research studying the effects of climate change and marine pollution on fish, whales, and sea turtles, very few seem to be interested in the changes happening to plankton communities. However, any alteration to the abundance, distribution, or composition of phytokplankton and zooplankton could very well translate into declines in productivity for fisheries, changes in feeding behaviors of marine mammals, and greater sea surface temperatures. Therefore, it’s important that we monitor the health of marine planktonic communities. It may not be sexy research, but it is vital research.
Enjoy the Podcast!