50
6 Comparisons of Fronts with Terrestrial Boundaries …
trophic levels, one can expect that fronts which persist for longer times will be
characterized by the presence of higher trophic levels. Thus, the presence of large
predators like big fishes are unlikely at fronts with short time scales, more typical
of small estuaries for example (Brandt 1993; Largier 1993). On the other hand,
the phytoplankton landscape may be organized into patches of around 10–100 km,
often dominated by a particular phytoplankton group, separated by physical fronts
induced by horizontal stirring. These physical fronts effectively delimit ephemeral
ecological niches by encircling water masses of similar history and whose lifetimes are comparable to the timescale of the phytoplankton biological response
(a few weeks) (d’Ovidio et al. 2010).
Specific locations in a landscape can serve as a boundary for one research question and as a patch for a different question (Cadenasso et al. 2003a). Marine fronts
share this dual character with terrestrial ecotones; they may also be considered
to function as distinct ecosystems, in so far as the physicochemical environment
and the biological characteristics found in a frontal region may differ markedly
from those of adjacent waters (Sournia 1994; Polovina et al. 2001). Ecotones can
represent unique habitats optimal to some species and inhospitable to others (di
Castri and Hansen 1992); for example, a biome transition zone is hypothesized
to have properties different from adjacent biomes and may amplify or attenuate some system processes such as productivity, resource dynamics and availability (Gosz 1992). Likewise, the physics of fronts provides unique opportunities
for various types of organisms; while at the same time, they can lead to an acute
set of physiological challenges. Some fauna would use fronts as prime foraging
grounds making use of the fact that some prey are at a disadvantage in the front
because of thermal, haline or nutritional stresses (Olson 2002). Human modifications of terrestrial landscapes overlying natural environmental heterogeneity (habitat fragmentation) is resulting in an increase in the number and types of ecological
patterns and their intervening boundaries (Peters et al. 2006), moreover some terrestrial boundaries may be experimentally modified in order to test scientific
hypotheses. This is a substantial difference with marine fronts, which cannot be
created by humans; although fronts’ properties can be altered; for example climate
change may play a role on modifying the location and perhaps the existence of
some fronts.
Much of our current theoretical understanding of marine fronts arises from
meteorological sciences (Olson 2002). Because of their fluid nature, the atmosphere and the oceans are governed by the same fundamental physical laws, and
consequently both systems present similar dynamics and analogous structures.
Flying insects and other components of the “aerial plankton” can be concentrated
by wind convergences (Russell 1999; Chapman et al. 2011). Large-scale atmospheric fronts are responsible for assisting the transport of insects into coastal
regions and landscape-induced sea/lake breeze circulations provide a mechanism
to explain the accumulations of a wide variety of insects on shorelines of large
water bodies (Isard et al. 2001). Flying insects concentrated by atmospheric fronts
and convergence of air masses settle and may attract insectivorous birds (Russell
1999) in analogous way to zooplankton aggregations at marine fronts attract
6 Comparisons of Fronts with Terrestrial Boundaries …
trophic levels, one can expect that fronts which persist for longer times will be
characterized by the presence of higher trophic levels. Thus, the presence of large
predators like big fishes are unlikely at fronts with short time scales, more typical
of small estuaries for example (Brandt 1993; Largier 1993). On the other hand,
the phytoplankton landscape may be organized into patches of around 10–100 km,
often dominated by a particular phytoplankton group, separated by physical fronts
induced by horizontal stirring. These physical fronts effectively delimit ephemeral
ecological niches by encircling water masses of similar history and whose lifetimes are comparable to the timescale of the phytoplankton biological response
(a few weeks) (d’Ovidio et al. 2010).
Specific locations in a landscape can serve as a boundary for one research question and as a patch for a different question (Cadenasso et al. 2003a). Marine fronts
share this dual character with terrestrial ecotones; they may also be considered
to function as distinct ecosystems, in so far as the physicochemical environment
and the biological characteristics found in a frontal region may differ markedly
from those of adjacent waters (Sournia 1994; Polovina et al. 2001). Ecotones can
represent unique habitats optimal to some species and inhospitable to others (di
Castri and Hansen 1992); for example, a biome transition zone is hypothesized
to have properties different from adjacent biomes and may amplify or attenuate some system processes such as productivity, resource dynamics and availability (Gosz 1992). Likewise, the physics of fronts provides unique opportunities
for various types of organisms; while at the same time, they can lead to an acute
set of physiological challenges. Some fauna would use fronts as prime foraging
grounds making use of the fact that some prey are at a disadvantage in the front
because of thermal, haline or nutritional stresses (Olson 2002). Human modifications of terrestrial landscapes overlying natural environmental heterogeneity (habitat fragmentation) is resulting in an increase in the number and types of ecological
patterns and their intervening boundaries (Peters et al. 2006), moreover some terrestrial boundaries may be experimentally modified in order to test scientific
hypotheses. This is a substantial difference with marine fronts, which cannot be
created by humans; although fronts’ properties can be altered; for example climate
change may play a role on modifying the location and perhaps the existence of
some fronts.
Much of our current theoretical understanding of marine fronts arises from
meteorological sciences (Olson 2002). Because of their fluid nature, the atmosphere and the oceans are governed by the same fundamental physical laws, and
consequently both systems present similar dynamics and analogous structures.
Flying insects and other components of the “aerial plankton” can be concentrated
by wind convergences (Russell 1999; Chapman et al. 2011). Large-scale atmospheric fronts are responsible for assisting the transport of insects into coastal
regions and landscape-induced sea/lake breeze circulations provide a mechanism
to explain the accumulations of a wide variety of insects on shorelines of large
water bodies (Isard et al. 2001). Flying insects concentrated by atmospheric fronts
and convergence of air masses settle and may attract insectivorous birds (Russell
1999) in analogous way to zooplankton aggregations at marine fronts attract