18
3 Biology of Fronts
thus relationships between organisms’ distributions and fronts may be complex and
nonlinear, especially for more mobile species (Brandt 1993).
Free swimmers like tunas, swordfish or sperm whales, detect fronts by sophisticated sensorial systems (Olson 2002). Strong convergence velocities associated
with fronts are very efficient in accumulating not only plankton but also other
floating materials along the convergence line. Flotsam often includes detritus
such as dust, foam and timber (Bowman 1978). Fish and other marine animals
show widespread attraction to drifting objects (Fig. 3.3), and this could be used
as a front detection mechanism in some cases (Bakun 1996; Castro et al. 2002);
so fish aggregated to drifting objects may obtain food by preying on organisms
aggregated at fronts. Other pelagic species, generally the long range migrants such
as tuna, may use floating objects as a landmarks or “meeting points” to increase
the encounter rate between isolated individuals or small schools and other schools
of con-specifics, thereby forming large schools to continue upon their migration
routes (Castro et al. 2002). However, the roles played by environmental variables
and by behavioral processes (e.g. social behavior) in the formation of these aggregations remain elusive (Robert et al. 2013).
Megaplanktivores such as filter-feeding sharks, Manta rays and baleen whales
are at the apex of a short food chain (phytoplankton–zooplankton–vertebrate) and
are sensitive indicators of sea-surface plankton availability (Fig. 3.4). Finding sufficiently large concentrations of appropriate prey in the open ocean to meet their
high metabolic needs is an impressive skill. It has been demonstrated that predictable oceanic and inner-shelf fronts are principal feeding areas for those megaplanktivorous species (Sims et al. 2005; Bost et al. 2009; Graham et al. 2012). Elephant
seals may use frontal eddies as foraging areas (Campagna et al. 2006; Bost et al.
2009). Marine turtles can exploit fronts as forage habitats (Polovina et al. 2001;
Fig. 3.3 Fishes attracted around old fishing rope (Simon Max Bannister and Sara Close, 5 Gyres
South Atlantic expedition). Strong convergence velocities associated with fronts are very efficient
in accumulating floating materials. Fishes show widespread attraction to drifting objects, and this
could be used as a front detection mechanism in some cases
3 Biology of Fronts
thus relationships between organisms’ distributions and fronts may be complex and
nonlinear, especially for more mobile species (Brandt 1993).
Free swimmers like tunas, swordfish or sperm whales, detect fronts by sophisticated sensorial systems (Olson 2002). Strong convergence velocities associated
with fronts are very efficient in accumulating not only plankton but also other
floating materials along the convergence line. Flotsam often includes detritus
such as dust, foam and timber (Bowman 1978). Fish and other marine animals
show widespread attraction to drifting objects (Fig. 3.3), and this could be used
as a front detection mechanism in some cases (Bakun 1996; Castro et al. 2002);
so fish aggregated to drifting objects may obtain food by preying on organisms
aggregated at fronts. Other pelagic species, generally the long range migrants such
as tuna, may use floating objects as a landmarks or “meeting points” to increase
the encounter rate between isolated individuals or small schools and other schools
of con-specifics, thereby forming large schools to continue upon their migration
routes (Castro et al. 2002). However, the roles played by environmental variables
and by behavioral processes (e.g. social behavior) in the formation of these aggregations remain elusive (Robert et al. 2013).
Megaplanktivores such as filter-feeding sharks, Manta rays and baleen whales
are at the apex of a short food chain (phytoplankton–zooplankton–vertebrate) and
are sensitive indicators of sea-surface plankton availability (Fig. 3.4). Finding sufficiently large concentrations of appropriate prey in the open ocean to meet their
high metabolic needs is an impressive skill. It has been demonstrated that predictable oceanic and inner-shelf fronts are principal feeding areas for those megaplanktivorous species (Sims et al. 2005; Bost et al. 2009; Graham et al. 2012). Elephant
seals may use frontal eddies as foraging areas (Campagna et al. 2006; Bost et al.
2009). Marine turtles can exploit fronts as forage habitats (Polovina et al. 2001;
Fig. 3.3 Fishes attracted around old fishing rope (Simon Max Bannister and Sara Close, 5 Gyres
South Atlantic expedition). Strong convergence velocities associated with fronts are very efficient
in accumulating floating materials. Fishes show widespread attraction to drifting objects, and this
could be used as a front detection mechanism in some cases