ASPEOTS 0 3 ' STBESS IN THE TROPIUAL MARINE ENVIRONMENT
221
range of salinity than with its mean value. For the American coasts
this range is least in mid-latitudes, much greater in polar waters and
somewhat greater in the tropics (Fig. 2).
C. Radiation
Moore (1958) quotes data showing that the total annual radiation
incident at the sea surface is not widely different in tropical and
temperate latitudes. A number of localities between 10"s and 10"N
average 14.3 x lo4 g.cal/cma per year while localities between 30" and
52" N and S averaged 11.1 x lo4. The main difference is in the greater
seasonality of the temperate radiation. Bakus (1969) has summarized
the differences in primary production in temperate and tropical seas.
Greater illumination in the tropics favors plant production, but vertical
stability of the water column reduces the supply of nutrients to the
surface waters. Differences in primary production are reflected all the
way up the food chain. We are not concerned here with comparing
total productivity, but it may be relevant that food supply will tend
to be more uniform throughout the year in tropical than in temperate
waters.
D. Tides
A large tidal range has certain marked advantages for an organism
living either intertidally or in shallow water. For the former it may allow
a large population and, among other things, a large supply of larvae for
recolonization. For both intertidal and shallow sublittoral zones it
produces stronger tidal currents with resulting improved flushing away
of waste products, better food supply and similar benefits.
It is generally assumed that tidal range is determined by the bottom
conformation in the neighborhood and in the basin through which the
tidal waves pass. To whatever extent this is true, the fact remains that
there is a clear relation of tidal range to latitude which is more or less
closely repeated in all oceans and in both hemispheres. The following
data are taken from the publications of the Coast and Geodetic Survey
(1968) and represent an analysis of about five thousand localities
covering all seas.
Figure 3 shows the relation of tidal range to latitude for all oceans
combined. What little information there is from high latitudes indicates
a small tidal range. Maximum ranges are found at about latitude 50" to
60". There is a marked decrease towards the tropics and apparently a
smaller rise again around the equator.
So far tides have been treated in relation to latitude but in the
following discussions we are generally more concerned with mean
221
range of salinity than with its mean value. For the American coasts
this range is least in mid-latitudes, much greater in polar waters and
somewhat greater in the tropics (Fig. 2).
C. Radiation
Moore (1958) quotes data showing that the total annual radiation
incident at the sea surface is not widely different in tropical and
temperate latitudes. A number of localities between 10"s and 10"N
average 14.3 x lo4 g.cal/cma per year while localities between 30" and
52" N and S averaged 11.1 x lo4. The main difference is in the greater
seasonality of the temperate radiation. Bakus (1969) has summarized
the differences in primary production in temperate and tropical seas.
Greater illumination in the tropics favors plant production, but vertical
stability of the water column reduces the supply of nutrients to the
surface waters. Differences in primary production are reflected all the
way up the food chain. We are not concerned here with comparing
total productivity, but it may be relevant that food supply will tend
to be more uniform throughout the year in tropical than in temperate
waters.
D. Tides
A large tidal range has certain marked advantages for an organism
living either intertidally or in shallow water. For the former it may allow
a large population and, among other things, a large supply of larvae for
recolonization. For both intertidal and shallow sublittoral zones it
produces stronger tidal currents with resulting improved flushing away
of waste products, better food supply and similar benefits.
It is generally assumed that tidal range is determined by the bottom
conformation in the neighborhood and in the basin through which the
tidal waves pass. To whatever extent this is true, the fact remains that
there is a clear relation of tidal range to latitude which is more or less
closely repeated in all oceans and in both hemispheres. The following
data are taken from the publications of the Coast and Geodetic Survey
(1968) and represent an analysis of about five thousand localities
covering all seas.
Figure 3 shows the relation of tidal range to latitude for all oceans
combined. What little information there is from high latitudes indicates
a small tidal range. Maximum ranges are found at about latitude 50" to
60". There is a marked decrease towards the tropics and apparently a
smaller rise again around the equator.
So far tides have been treated in relation to latitude but in the
following discussions we are generally more concerned with mean