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C. Hily and M. Bernard
also factors which can modify the intertidal seascape more frequently and more
deeply than modifications of the terrestrial landscapes under storms. In addition, oil
spills are known to deeply modify seascapes and the ecosystem functioning. The
ecological successions initiated after cleaning operations have also been described
and the processes studied, but recovery of intertidal ecosystems have not been studied
in terms of patch dynamics restoration at the landscape scale.
Thus, the different potentialities of an intertidal seascape approach can be
summarized as follow:
An intertidalscape approach can:
• Facilitate the identification of habitats: a new hierarchical classification of
intertidal habitat has been recently proposed. It uses some visual features of
patches to differentiate rocky habitats (the REBENT typology, Guillaumont et al.
2010). It is a classification adapted from the Eunis classification to facilitate the
habitat mapping. As an example, the mediolittoral habitat type “Rock and boulders
dominated by macroalgae” is differentiated from the habitat “Rock and boulders
dominated by macrofauna”. The edges and the fragmentation of such patches can
be easily identified and mapped by GPS.
• Detect changes: periodical intertidalscape reading help the detection of temporal
changes both at short-term by identifying the spatial amplitude of the dynamic
stability (ex: mussel beds), and at long-term by identifying persistent modifications of the mosaic due to a component fragmentation. Short term changes: as
underlined by Ellis and Schneider (1997) “more than any other factor, our inability
to explain natural variability places a limit on our ability to detect anthropogenic
change”. This variability is not only effective at the spatial scale but also at the
temporal scale. Changes observed in an intertidalscape can be the result of a
punctual natural event, visible for a few days or weeks, but with no consequences
at a pluri-annual scale. As an example, beaching of drifting kelp uprooted by a
winter storm is an event which can totally change the intertidalscape for days and
weeks. Easily visible by an observer, the phenomenon induces drastic changes in
the ecosystem functioning of the shore. We studied the ecological consequences
of the beaching of abundant laminariales (which can reach more than one meter in thickness) on a shore of the Molene archipelago in the West Brittanny
(Le Hir 2002). We showed that the structure and functioning of the ecosystem
was modified by cascading effects in a bottom up stimulation of the trophic network. The detritus of macroalgal were exploited by detritivorous amphipods and
isopods which increased drastically their populations and were further eaten by a
diverse fauna of secondary consumers. Such events are a part of the natural annual
variability of the intertidalscape and functioning of the intertidal ecosystems.
• Describe evolution, banalization and homogeneization of the intertidalscape
Kelp beaching events may also be induced by anthropogenic activities resulting
from waste of the mechanical harvesting of laminariales during spring and summer. In this case, algae remain accumulated on the substratum for months and
the ecosystem cannot assimilate these amounts of organic matter as described
previously. As a consequence, anaerobic decomposition induces high mortalities on fauna and flora, associated with strong visual, olfactory and functioning
consequences at the scale of the beach site.
C. Hily and M. Bernard
also factors which can modify the intertidal seascape more frequently and more
deeply than modifications of the terrestrial landscapes under storms. In addition, oil
spills are known to deeply modify seascapes and the ecosystem functioning. The
ecological successions initiated after cleaning operations have also been described
and the processes studied, but recovery of intertidal ecosystems have not been studied
in terms of patch dynamics restoration at the landscape scale.
Thus, the different potentialities of an intertidal seascape approach can be
summarized as follow:
An intertidalscape approach can:
• Facilitate the identification of habitats: a new hierarchical classification of
intertidal habitat has been recently proposed. It uses some visual features of
patches to differentiate rocky habitats (the REBENT typology, Guillaumont et al.
2010). It is a classification adapted from the Eunis classification to facilitate the
habitat mapping. As an example, the mediolittoral habitat type “Rock and boulders
dominated by macroalgae” is differentiated from the habitat “Rock and boulders
dominated by macrofauna”. The edges and the fragmentation of such patches can
be easily identified and mapped by GPS.
• Detect changes: periodical intertidalscape reading help the detection of temporal
changes both at short-term by identifying the spatial amplitude of the dynamic
stability (ex: mussel beds), and at long-term by identifying persistent modifications of the mosaic due to a component fragmentation. Short term changes: as
underlined by Ellis and Schneider (1997) “more than any other factor, our inability
to explain natural variability places a limit on our ability to detect anthropogenic
change”. This variability is not only effective at the spatial scale but also at the
temporal scale. Changes observed in an intertidalscape can be the result of a
punctual natural event, visible for a few days or weeks, but with no consequences
at a pluri-annual scale. As an example, beaching of drifting kelp uprooted by a
winter storm is an event which can totally change the intertidalscape for days and
weeks. Easily visible by an observer, the phenomenon induces drastic changes in
the ecosystem functioning of the shore. We studied the ecological consequences
of the beaching of abundant laminariales (which can reach more than one meter in thickness) on a shore of the Molene archipelago in the West Brittanny
(Le Hir 2002). We showed that the structure and functioning of the ecosystem
was modified by cascading effects in a bottom up stimulation of the trophic network. The detritus of macroalgal were exploited by detritivorous amphipods and
isopods which increased drastically their populations and were further eaten by a
diverse fauna of secondary consumers. Such events are a part of the natural annual
variability of the intertidalscape and functioning of the intertidal ecosystems.
• Describe evolution, banalization and homogeneization of the intertidalscape
Kelp beaching events may also be induced by anthropogenic activities resulting
from waste of the mechanical harvesting of laminariales during spring and summer. In this case, algae remain accumulated on the substratum for months and
the ecosystem cannot assimilate these amounts of organic matter as described
previously. As a consequence, anaerobic decomposition induces high mortalities on fauna and flora, associated with strong visual, olfactory and functioning
consequences at the scale of the beach site.