Because autotrophic organisms form the base of the food web, all of the energy available to the ocean ecosystem is derived from phytoplankton, algae, and bacteria. So it is important not to disturb the productivity of the autotrophs. In oceanic food chain, seasonal factors cause fluctuations in the growth rate and size of the phytoplankton crop. Consequently, these factors cause seasonal fluctuations in the growth rates and size of all of the other consumer in the food chain.
Ecology
Ecosystems function to
convert energy from one form to another, such as
converting the radiant energy of sunlight to the chemical energy of sugars
and other compounds in phytoplankton or algae. In turn, this chemical
energy is consumed by other organisms who themselves are consumed.
Ecosystems also function as storage places for various chemical elements.
Since all organisms are composed of carbon,
nitrogen,
oxygen, sulfur, phosphorous
and
other elements. These chemicals are moved from seawater to an organism,
such as phytoplankton, algae, or bacteria, and then from one organism to
another as each is consumed in succession. At each step, some compounds
are lost through respiration, excretion, feces, or death of the organism. In this
form, many elements are returned to their nonliving inorganic form as
bacteria decompose the compounds in which they were constituted. Once
returned to seawater or sediments, these elements become available to
organisms, thus starting the cycle of elements all over again. As a
result, elements cycle through ecosystems and continue to cycle through
until lost permanently, either by conversion to a permanent form, such as
petrified wood or limestone.
The amount of living material produced by net and gross primary
production
can be expressed as the number of organisms produced, their weight, or
grams of carbon; this is known as biomass. Biomass is usually reported as
the dry weight of organic carbon in grams present under a square meter of
sea surface or gC/m2. The rate at which biomass changes, also known as
primary productivity, is reported as gC/m2/time.
