16 Remote Sensing of Coral Reefs and Their Environments . . .
329
necessity to couple SST observations with field data on coral communities, especially
where acclimation and reorganization of the coral community have occurred due to
past bleaching events.
To date the only multi-factor analysis of bleaching events for the Indian Ocean,
Maina et al. (2008) combined a variety of remotely sensed data to model the susceptibility of coral reefs to environmental stress. Specifically, they used surface currents,
wind velocity; SST, UV radiation, photosynthetically active radiation (PAR), and
chlorophyll a concentration to develop predictors of thermal stress. In addition, fairly
original (in an oceanography context) soft computing methods, such as fuzzy logic
algorithms, have been used to integrate these environmental variables into the measure of susceptibility. The Maina et al. (2008) approach will certainly pave the way
to more integrated interdisciplinary, multisensory and multiscale study of complex
regional coral reef processes in the Red Sea, the Indian Ocean and elsewhere (Maina
et al. 2011).
Beside coral bleaching, ocean warming can impact coral reef ecosystems through
the widening of the tropical belt. The previous regions of marginal coral growth
and marginal communities should shift southward and northward at the latitudinal
extremes. As pointed out by Lloyd et al. (2012) these consequences are largely unexplored to date. These authors have compared changes in fish community structures
paralleled by a 0.46
◦ C increase of average sea surface temperature between the time
periods 1989–97 and 2002–2007. SST monthly observations came from 4 km resolution AVHRR products. They concluded that the relative abundance of temperate
species as a whole decreased whereas that of tropical species increased, and broadly
distributed species showed little change. These results confirmed the expected poleward shift in species ranges, and the increase in species richness and diversity with
increasing sea temperature along the East Africa coastline.
A number of key processes for coral reef resilience could be studied with indirect
remote sensing data. This includes physical connectivity between reefs through the
modelling of a tracer that simulates larvae dispersal, and ocean color observations.
Conducted elsewhere (Soto et al. 2009), these connectivity applications are yet to be
conducted in the Western Indian Ocean. However, Acker et al. (2008) observed in
the northern Red Sea with Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and
MODIS data the geochemical consequences of water enrichment by the nearby coral
reefs. Their data indicated that large coral reef complexes could export either nutrients
or chlorophyll-rich detritus and sediment, enhancing chlorophyll a concentration in
normally oligotrophic waters adjacent to the reefs.
16.4 Remote Sensing for Management and Coral Reef
Conservation
In principles, a number of the aforementioned direct and indirect applications are
relevant for coral reef management and conservation. Throughout the planet, remote
sensing derived products are increasingly used to map habitats and monitor the
329
necessity to couple SST observations with field data on coral communities, especially
where acclimation and reorganization of the coral community have occurred due to
past bleaching events.
To date the only multi-factor analysis of bleaching events for the Indian Ocean,
Maina et al. (2008) combined a variety of remotely sensed data to model the susceptibility of coral reefs to environmental stress. Specifically, they used surface currents,
wind velocity; SST, UV radiation, photosynthetically active radiation (PAR), and
chlorophyll a concentration to develop predictors of thermal stress. In addition, fairly
original (in an oceanography context) soft computing methods, such as fuzzy logic
algorithms, have been used to integrate these environmental variables into the measure of susceptibility. The Maina et al. (2008) approach will certainly pave the way
to more integrated interdisciplinary, multisensory and multiscale study of complex
regional coral reef processes in the Red Sea, the Indian Ocean and elsewhere (Maina
et al. 2011).
Beside coral bleaching, ocean warming can impact coral reef ecosystems through
the widening of the tropical belt. The previous regions of marginal coral growth
and marginal communities should shift southward and northward at the latitudinal
extremes. As pointed out by Lloyd et al. (2012) these consequences are largely unexplored to date. These authors have compared changes in fish community structures
paralleled by a 0.46
◦ C increase of average sea surface temperature between the time
periods 1989–97 and 2002–2007. SST monthly observations came from 4 km resolution AVHRR products. They concluded that the relative abundance of temperate
species as a whole decreased whereas that of tropical species increased, and broadly
distributed species showed little change. These results confirmed the expected poleward shift in species ranges, and the increase in species richness and diversity with
increasing sea temperature along the East Africa coastline.
A number of key processes for coral reef resilience could be studied with indirect
remote sensing data. This includes physical connectivity between reefs through the
modelling of a tracer that simulates larvae dispersal, and ocean color observations.
Conducted elsewhere (Soto et al. 2009), these connectivity applications are yet to be
conducted in the Western Indian Ocean. However, Acker et al. (2008) observed in
the northern Red Sea with Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and
MODIS data the geochemical consequences of water enrichment by the nearby coral
reefs. Their data indicated that large coral reef complexes could export either nutrients
or chlorophyll-rich detritus and sediment, enhancing chlorophyll a concentration in
normally oligotrophic waters adjacent to the reefs.
16.4 Remote Sensing for Management and Coral Reef
Conservation
In principles, a number of the aforementioned direct and indirect applications are
relevant for coral reef management and conservation. Throughout the planet, remote
sensing derived products are increasingly used to map habitats and monitor the