<P> The factors limiting primary production in the ocean are also very different from those on land . The availability of water , obviously , is not an issue ( though its salinity can be ) . Similarly , temperature , while affecting metabolic rates ( see Q ) , ranges less widely in the ocean than on land because the heat capacity of seawater buffers temperature changes , and the formation of sea ice insulates it at lower temperatures . However , the availability of light , the source of energy for photosynthesis , and mineral nutrients , the building blocks for new growth , play crucial roles in regulating primary production in the ocean . Available Earth System Models suggest that ongoing ocean bio-geochemical changes could trigger reductions in ocean NPP between 3 % and 10 % of current values depending on the emissions scenario . </P>
which is the major limiting element in marine primary production
the availability of light mineral nutrients