The Ocean Food Chain

Ocean ecosystems - wave crashing
        An ecosystem is the grouping of plants and animals and the location that they live in. All the oceans make up the largest ecosystem. Smaller ecosystems exist as well. Examples of smaller ecosystems include a stretch of shore, a tidepool, or a gulf. (Day 119) Organisms are grouped into either benthic or pelagic catagories. Benthic organisms are those found on the sea floor or in the sediment. Pelagic organisms are those found in the open sea. (Day 119) There are three main types of organisms in the ocean ecosystem: producers, consumers and decomposers. Producers are seaweed and other plants which serve as food for consumers. The animals are termed consumers; they consume plants and animals to survive. Examples of decomposers are bacteria and fungi; they break down substances. (Day 119)
        First we will talk about the producers, or the plants. There are two kinds of plants found in the ocean: microscopic plants that float around and bigger plants such as seaweed that grow up from the ground. These bigger plants provide a habitat for other organisms. (Kraynak 83)
        Producers normally form the base of a food pyramid, which will be discussed later. In the ocean, there are three primary producers: photosynthetic plants, chemosynthetic bacteria, and detritus. Photosynthetic plants soak up energy from the sun and use it to form sugar. Animals then eat these plants for energy. Cyanobacteria are photosynthetic, though they aren't plants. They make up 80% of the production of phytoplankton. Chemosynthetic bacteria hang around hydrothermal vents and use the chemicals they find there to produce sugars. Clams and mussells feed off of these bacteria. Larger animals in turn feed off of them. Organic wastes are converted by fungi and bacteria into something called detritus. Certain creatures feed off of detritus, which usually settles to the bottom of the ocean. Some detritus, however, can be carried by water currents to other areas. Sometimes it is carried to where it helps plankton to bloom. Whales in turn can feed off of the plankton. (Kraynak 86-87)
        Algae is a type of photosynthetic plant. Macroalgae are large algae that consist of a holdfast, a stipe, and blades. Macroalgae commonly are either brown, green, or red. They are very different from microalgae, the green specks that will grow in water if left by a window. Seaweed is commonly found in ocean waters and is a type of macroalgae. Seaweed stays anchored by use of its holdfast; they can stay in place for years. Some seaweed is intertidal and receives a beating from the constant waves. At low tide, 90% of their moisture is baked out by the sun before they rehydrate at high tide. (Kraynak 98-99)
        Consumers are the next type of organism we will discuss. When we talk about consumers, we naturally may ask what they are consuming. Well, Scientists often study what eats what. In doing so, they compose a food chain, a chart with arrows indicating an order of consumption. Generally the lowest level on the food chain is phytoplankton. Primary consumers are the second level in the food chain, feeding off of producers like phytoplankton. Secondary consumers are the third level, and they eat primary consumers. Tertiary consumers are the fourth level, eating secondary consumers. Dolphins are an example of tertiary consumers. Sometimes organisms will eat from more than one level in a food chain. This can make the organism more resiliant because if one food source dies off they will have other options. But, food chains are interconnected and variations in food supply can have their effect on other organisms. (Day 119-120)
        An ecological niche is where an organisms exists and includes the organism's diet, how it lives, and how it reproduces. Usually a single species occupies an ecological niche. However, sometimes there is competition within the niche for similar resources. Often, one organism will beat the other organism within it's niche. This is termed the competition-exclusion principle. (Day 119)
        Sometimes organisms will share resources by specialization. This is called resource partitioning. An example of this is shorebirds which exploit different levels in the mud on their search for food. (Day 119)
        Decomposers are the final type of organism that will be mentioned. Decomposers are: animal-like protists, bacteria and fungi. Decomposers ingest various animal, plant and microbial wastes and convert them into simple inorganic compounds. This conversion process recycles essential nutrients back into the ocean ecosystem. Decomposers and the dead, organic matter that they feed on are sometimes called detritus. Detrivores feed on detritus, bringing those elements back into the food chain. This is called the microbial loop. (Day 119)
        In conclusion, the ocean ecosystem operates smoothly because of the interaction of all of it's organisms. This interaction plays out along shorelines, in gulfs and throughout the depths found in the middle of oceans. The organisms can be seen as composing a food chain; the three types of organisms: producers, consumers, and decomposers, exist together and feed off each other according to a certain order. This order keeps the ocean teeming with life.


Day, Trevor. Oceans, Revised Edition. New York: Facts On File, Inc., 2008. Print.

Kraynak, Joe, and Kim W. Tetrault. The Complete Idiot's Guide to The Oceans. New York: Alpha Books, 2003. Print.

Site Design: Ardriondree Software, custserv@ardriondree.com