Abstract
The various sources of organic compounds in the oceans are shown in Figure 9.1 and tabulated in Table 9.1. As is apparent from Table 9.1, the major source of organic compounds to
the ocean is from the primary production of marine plants (Falkowski, 2012). This primary
production is the result of the growth of these organisms as a result of photosynthetic
processes. It provides the basis of the marine food chain that culminates in fsh and mammals. The plants remove CO2 and micronutrients from the water and, using solar energy,
convert them to complex organic compounds. The simple reaction for the formation of
carbohydrates is
light
CO2 + H2O → CH2O + O2 (9.1)
Phytoplankton are the microorganisms responsible for the greatest primary production
in the sea. Attached algae are important in shallow waters. Phytoplankton are free-Žoating
microscopic plants with only limited mobility and are distributed by ocean currents. They
can be divided by size into
Microplankton: 50 to 500 μm
Nanoplankton: 10 to 50 μm
Ultraplankton: 0.5 to 10 μm
Since they live primarily by photosynthesis, they are phototrophic organisms. Photosynthesis
is a complicated process: Solar energy is absorbed by phytoplankton cells and converted
to biological energy stored in the form of organic compounds. The stages are as follows:
1. Absorption of photons of light by photosynthetic pigments that are contained in
the chromatophores. The principal pigments are chlorophylls. The structure of
chlorophyll-a is shown in Figure 9.2. The resonating system of double bonds stabilizes the molecule and provides electrons that are easily excited to orbitals of
higher energy when light is absorbed.