51
6 Comparisons of Fronts with Terrestrial Boundaries …
fishes and other predators. Many atmospheric fronts are produced at terrestrial
ecotones, such as shorelines of large water bodies or the land/sea boundary (Isard
et al. 2001); however they are hardly seen as a vertical extension of such ecotones.
Moreover, in contrast with marine fronts, the location of few atmospheric fronts
is locked to the topography of land and they therefore displace thousands of kilometers. Although the resemblance of the physical dynamics of atmospheric and
marine fronts is remarkable, the ecological effects of marine fronts are of greater
consequence. This is so because primary producers in the sea are planktonic
(phytoplankton) and their abundances are strongly influenced by flows at fronts:
vertical flows that bring nutrients into the illuminated upper layer and convergent
flows that concentrate and retain phytoplankton at frontal interfaces. Moreover,
primary consumers in the sea (a key element in the energy transference to upper
trophic levels) are mostly planktonic (e.g. copepods) and are also severely influenced by frontal dynamics. Finally, most of the fishes and invertebrates possess
planktonic larval stages. In the atmosphere, there are no species equivalents to
marine phytoplankton; consequently the atmospheric circulation is not relevant for
nutrient distribution and atmospheric fronts cannot promote primary production.
In addition, the flying insects concentrated at atmospheric fronts are adult stages
and play no role in the trophic webs comparable to that of marine zooplankton.
Temporal scales are also different, while atmospheric fronts last for hours or days
(Steele 1991) most marine fronts are permanent or seasonal; as mentioned above,
the ecological impact of ecotones increase with their persistence.
6 Comparisons of Fronts with Terrestrial Boundaries …
fishes and other predators. Many atmospheric fronts are produced at terrestrial
ecotones, such as shorelines of large water bodies or the land/sea boundary (Isard
et al. 2001); however they are hardly seen as a vertical extension of such ecotones.
Moreover, in contrast with marine fronts, the location of few atmospheric fronts
is locked to the topography of land and they therefore displace thousands of kilometers. Although the resemblance of the physical dynamics of atmospheric and
marine fronts is remarkable, the ecological effects of marine fronts are of greater
consequence. This is so because primary producers in the sea are planktonic
(phytoplankton) and their abundances are strongly influenced by flows at fronts:
vertical flows that bring nutrients into the illuminated upper layer and convergent
flows that concentrate and retain phytoplankton at frontal interfaces. Moreover,
primary consumers in the sea (a key element in the energy transference to upper
trophic levels) are mostly planktonic (e.g. copepods) and are also severely influenced by frontal dynamics. Finally, most of the fishes and invertebrates possess
planktonic larval stages. In the atmosphere, there are no species equivalents to
marine phytoplankton; consequently the atmospheric circulation is not relevant for
nutrient distribution and atmospheric fronts cannot promote primary production.
In addition, the flying insects concentrated at atmospheric fronts are adult stages
and play no role in the trophic webs comparable to that of marine zooplankton.
Temporal scales are also different, while atmospheric fronts last for hours or days
(Steele 1991) most marine fronts are permanent or seasonal; as mentioned above,
the ecological impact of ecotones increase with their persistence.