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How to Trace the Energy Flow Through an Aquatic Habitat

Energy in an aquatic ecosystem cycles through a process that begins with the absorption of heat in the form of radiation from the sun by aquatic plants, proceeds through aquatic animals by way of the food chain and continues through decomposition. The process of primary production, wherein organic matter is produced directly from the absorption of radiation, gives way to the addition of new plant biomass to the aquatic habitat. Then, the energy can be traced from smaller to larger aquatic species. Energy works its way through these species and eventually the matter decomposes and the energy recycles back into the environment.

Things You'll Need

Diagram of aquatic ecosystem food chain (optional)

Instructions

- 1
  Record your observations of the process of primary production through photosynthetic plant species in an aquatic environment. Photosynthesis is most active during the afternoon when the strongest levels of sunlight are present. Record the amount of a specific water surface-bound aquatic population, such algae, at a determined time in the afternoon. Compare the population to the size of an everyday object, such as an orange or a shoebox. Return at the same time the next day and observe the general size of the population again. Fast-growing species, such as algae, clearly illustrate primary production as the biomass of the population grows day by day. However, these observations are only a estimate and can be skewed by environmental factors, such when animals eat the plant matter or storms disturb it.
- 2
  Observe the transfer of energy by way of the food chain in the aquatic environment. Mark the the transfer of energy from one organism to another on your diagram of an aquatic ecosystem food chain or draw your own simple diagram using words or pictures to sequentially illustrate each organism and its position in the process. The energy transfer is demonstrated as a small insect eats algae that grows on the water's surface, for example. It is again transferred as a fish eats the insect for nourishment. Large mammals, such as bears, are considered part of an aquatic habitat as well, because they eat fish and other aquatic species such as frogs and reptiles.
- 3
  Record your observations of decomposition in the aquatic habitat on your diagram to trace the completion of the energy cycle. Take note of the biomass situated underneath plants that grow on the water's edge. This biomass is usually recognizable as debris from the same plant species that, after death, continues the energy cycle and, in turn, nourishes living, growing plants. Notice and document how large areas of decomposing biomass on the water's surface provide shelter from the direct sunlight for some aquatic animal species to lay eggs and nurture young. Search for and report underwater, terrestrial species, such as aquatic worms, that thrive in decomposing plant matter that forms the soil and silt underneath the water.

Animals & Science