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Decline of locally available fish populations and eventual local extinction is
likely. One consequence of elevated temperature is sea-level rise. For moderate
rates of sea level rise enhanced vegetation growth is likely as the ecosystem strives
to adapt. At faster rates of SLR vegetation however, mortality ensues as the
substrate deepens beyond depths capable of supporting vegetation (Kirwan et al.,
2010). Also, adults that are only salinity tolerant for short periods of time (typically
located more shoreward) will suffer from prolonged exposure to seawater. Over
the longer term, the impacts of sea-level rise on mangroves and mangrove
associates need not necessarily be negative, provided shoreward migration is
possible (Waycott et al, 2011). More intense sea level rise is likely to impact
seagrass meadows. Higher sea-level expose more of the coast to erosion bring
about increased nutrient and sedimentation. High nutrient input can be good for the
seagrass as these meadows are known to be nutrient poor. However, the increased
sedimentation can bury seagrass meadows or at the very least leave the water
murky for extended periods of time. These will compromise seagrass productivity
(Gacia, et al., 2005; Orth et al., 2006). In terms of fisheries this specifically
impacts on seagrass related fisheries such as that of rabbit fish and prawns. It will
also have a cascade effect on larger target fish since seagrass meadows provide
food for these higher trophic levels.
Ocean acidification have also been observed to negatively affect the
recruitment success of temperate species (Simpson et al., 2011; Munday et al.,
2009) but may not necessarily be disadvantageous for tropical benthic-spawning
marine fishes (Munday et al., 2009b). Coral reefs however,are highly susceptible to
degradation from increases in ocean temperature (coral bleaching) and reduced
calcification due to ocean acidification (Munday et al. 2008, Pratchett et al. 2011,
Hughes et al. 2003, Hoegh-Guldberg et al., 2011). Loss of coral cover, typically
result in the decline of smaller-bodied coral-associated fishes that are dependent on
the structure of reef habitat for shelter (Graham et al. 2008). Only the small
generalist species and rubbledwellers are expected to increase in abundance on
degraded coral reefs (Bellwood et al. 2006; Ticzon et al., 2012). These species are
generally not utilized as food fish.
There are also particular economically important species that require the
presence of all three coastal habitats to be sustainable such as groupers. As habitat
health is degraded due to climate change larger predators will also be affected
(Sundblad, 2014). This can happen in two ways. Both pelagic and demersal
predators also use the mangroves, seagrass, and corals as nursery ground. Hence,
their population will also be compromised as the habitats get degraded. In addition,
as the smaller habitat-affiliated fishes are compromised the predators may end up
migrating to more bountiful cooler and deeper areas. This will tax small-scale
fishers who have limited mobility.
An alternative food resource is mariculture which is a more controlled
environment. But experience has shown that this is not climate-proof either.
Anomalous warming of ocean water affects the oxygen content of the water and
has historically resulted to massive fish kills within mariculture sites (David, et
al., 2014). Increase in surface ocean temperature might also abet the formation of