15 Vertical Structure of Ocean Waters and
Biological Productivity
15.1 Introduction
It is a widely accepted opinion that phytoplankton need light and nutrients
for growth and reproduction. The source of light comes from above, while the
source of nutrients is at depth. Therefore, to bring the nutrients to the surface,
vertical water fluxes are needed. As we showed in the previous chapters, there
is a variety of hydrodynamic processes, such as upwelling, turbulent and tidal
mixing, and internal waves, all resulting in a vertical transport of water mass.
A complete description of the link between vertical structure of ocean water
and biological ocean productivity is out of the scope of this book. Rather,
this broad subject deserves its own separate book. In this chapter we will only
provide some examples of the influence of vertical ocean structure on primary
production.
The obvious physical mechanism which provides vertical transport of water
mass is upwelling. The upwelling results in the replacement of warm surface
water with colder nutrient-rich water. There are three primary types of upwelling: coastal, polar and equatorial. The best known upwelling is coastal.
The relationship between water movement and primary production associated
with coastal upwelling is discussed in Sect. 15.2.
The distribution of ocean water temperature, salinity, density and other water
properties is not uniform throughout the water column or in the horizontal
plane. Instead, there are many regions where horizontal gradients are very
large. They are known as fronts, which appear in many sizes, from large oceanic
fronts down to small scale fronts within island wakes. As the larger fronts are
relatively well known, in Sect. 15.3 the emphasis is on small-scale, less known
fronts in shallow waters.
Finally, in Sect. 15.4, the problem of a lack of stratification due to tidal
mixing and biological production is described. The lack of stratification would
be expected to decrease phytoplankton productivity. However, vigorous mixing
by tides in shallow and shelf waters brings the nutrients back into the water
column and stimulates phytoplankton production (Sects. 15.5 and 15.6).
S. R. Massel, Fluid Mechanics for Marine Ecologists
© Springer-Verlag Berlin Heidelberg 1999
Biological Productivity
15.1 Introduction
It is a widely accepted opinion that phytoplankton need light and nutrients
for growth and reproduction. The source of light comes from above, while the
source of nutrients is at depth. Therefore, to bring the nutrients to the surface,
vertical water fluxes are needed. As we showed in the previous chapters, there
is a variety of hydrodynamic processes, such as upwelling, turbulent and tidal
mixing, and internal waves, all resulting in a vertical transport of water mass.
A complete description of the link between vertical structure of ocean water
and biological ocean productivity is out of the scope of this book. Rather,
this broad subject deserves its own separate book. In this chapter we will only
provide some examples of the influence of vertical ocean structure on primary
production.
The obvious physical mechanism which provides vertical transport of water
mass is upwelling. The upwelling results in the replacement of warm surface
water with colder nutrient-rich water. There are three primary types of upwelling: coastal, polar and equatorial. The best known upwelling is coastal.
The relationship between water movement and primary production associated
with coastal upwelling is discussed in Sect. 15.2.
The distribution of ocean water temperature, salinity, density and other water
properties is not uniform throughout the water column or in the horizontal
plane. Instead, there are many regions where horizontal gradients are very
large. They are known as fronts, which appear in many sizes, from large oceanic
fronts down to small scale fronts within island wakes. As the larger fronts are
relatively well known, in Sect. 15.3 the emphasis is on small-scale, less known
fronts in shallow waters.
Finally, in Sect. 15.4, the problem of a lack of stratification due to tidal
mixing and biological production is described. The lack of stratification would
be expected to decrease phytoplankton productivity. However, vigorous mixing
by tides in shallow and shelf waters brings the nutrients back into the water
column and stimulates phytoplankton production (Sects. 15.5 and 15.6).
S. R. Massel, Fluid Mechanics for Marine Ecologists
© Springer-Verlag Berlin Heidelberg 1999