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3 Biology of Fronts
primary biological response is tied to the dynamics of the smaller scale features,
that is the individual fronts, which are characteristic of these frontal zones.
Persistent fronts likely set recruitment patterns of those organisms having a
planktonic larval phase through a variety of biophysical coupling mechanisms.
As pointed out above, fronts can act as accumulators of passive, buoyant particles and weakly swimming organisms, in particular phytoplankton and small zooplankton including larvae. Increased phytoplankton and zooplankton biomass at
frontal regions may also lead to increased development rates and shorter pelagic
larval duration for many species. Because recruitment of larvae to adults’ populations is a key component of resilience in marine ecosystems, regions of high
frontal activity, where recruitment is less variable and generally higher, will be
more resilient and sustainable compared to regions with low front probability
(Woodson et al. 2012).
The distributional problems faced by plankton are an important component of
the ecology of the oceans, not only because the plankton is a diverse and highly
abundant group occupying key links in trophic webs, but also because most of the
benthic or nektonic forms have planktonic larvae. Retention areas may be important for maintaining population persistence, and the retention of eggs and larvae
in favorable areas has been hypothesized as an important determinant of marine
fish year class strength (Bernatchez and Martin 1996; Iles and Sinclair 1982).
Moreover, density relations can be particularly important and concentration of
organisms in frontal areas promotes biological interactions such as predation
(McManus and Woodson 2012); reproduction (Sinclair 1988) or parasites transmissions (Díaz Briz et al. 2012). As was nicely stated by Kiorboe (2008) “Life
is all about encounters… phytoplankton cells need to encounter molecules of
nutrient salts and inorganic carbon; bacteria need to encounter organic molecules;
viruses need to encounter their hosts; predators need to encounter their prey; and
males need to encounter females (or vice versa)”. Concentration and retention
processes (together with nutrients fertilization) are reasons for the key ecological
importance of marine fronts.
3.6 Migrations and Transport
Long-distance migration has evolved in many marine organisms moving through
different habitats and using various modes of locomotion. In most cases migration has evolved basically as a strategy to maximize fitness in a seasonal environment. The basic driving forces for migration are seasonality, spatiotemporal
distributions of resources, habitats, predation and competition. Marine migrants,
moving in an open-ocean environment devoid of visual landmarks, demonstrate
impressive navigational abilities; however the sensory mechanisms used are still
largely unknown. The poor eyesight above water of most of these migrant species
(Ehrenfeld and Koch 1967) probably precludes the use of star patterns and other
celestial cues. Some studies suggest that fronts may act as marks or traces that
3 Biology of Fronts
primary biological response is tied to the dynamics of the smaller scale features,
that is the individual fronts, which are characteristic of these frontal zones.
Persistent fronts likely set recruitment patterns of those organisms having a
planktonic larval phase through a variety of biophysical coupling mechanisms.
As pointed out above, fronts can act as accumulators of passive, buoyant particles and weakly swimming organisms, in particular phytoplankton and small zooplankton including larvae. Increased phytoplankton and zooplankton biomass at
frontal regions may also lead to increased development rates and shorter pelagic
larval duration for many species. Because recruitment of larvae to adults’ populations is a key component of resilience in marine ecosystems, regions of high
frontal activity, where recruitment is less variable and generally higher, will be
more resilient and sustainable compared to regions with low front probability
(Woodson et al. 2012).
The distributional problems faced by plankton are an important component of
the ecology of the oceans, not only because the plankton is a diverse and highly
abundant group occupying key links in trophic webs, but also because most of the
benthic or nektonic forms have planktonic larvae. Retention areas may be important for maintaining population persistence, and the retention of eggs and larvae
in favorable areas has been hypothesized as an important determinant of marine
fish year class strength (Bernatchez and Martin 1996; Iles and Sinclair 1982).
Moreover, density relations can be particularly important and concentration of
organisms in frontal areas promotes biological interactions such as predation
(McManus and Woodson 2012); reproduction (Sinclair 1988) or parasites transmissions (Díaz Briz et al. 2012). As was nicely stated by Kiorboe (2008) “Life
is all about encounters… phytoplankton cells need to encounter molecules of
nutrient salts and inorganic carbon; bacteria need to encounter organic molecules;
viruses need to encounter their hosts; predators need to encounter their prey; and
males need to encounter females (or vice versa)”. Concentration and retention
processes (together with nutrients fertilization) are reasons for the key ecological
importance of marine fronts.
3.6 Migrations and Transport
Long-distance migration has evolved in many marine organisms moving through
different habitats and using various modes of locomotion. In most cases migration has evolved basically as a strategy to maximize fitness in a seasonal environment. The basic driving forces for migration are seasonality, spatiotemporal
distributions of resources, habitats, predation and competition. Marine migrants,
moving in an open-ocean environment devoid of visual landmarks, demonstrate
impressive navigational abilities; however the sensory mechanisms used are still
largely unknown. The poor eyesight above water of most of these migrant species
(Ehrenfeld and Koch 1967) probably precludes the use of star patterns and other
celestial cues. Some studies suggest that fronts may act as marks or traces that