The long-term sustainability of seagrasses, particularly
in the subtropics and tropics, depend on their
ability to adapt to shifts in salinity regimes influenced
by anthropogenic modifications of upstream hydrology,
as well as predicted long-term temperature
increases (Short and Neckles 1999). Tropical species
are living at the edge of their upper physiological
limits of salinity (Walker 1985; Walker et al. 1988)
and temperature (Zieman 1975; Koch et al. 2007), so
further increases in salinity as a result of climate
change and freshwater extraction may have signifi-
cant consequences for tropical seagrasses particularly
in estuaries with restricted circulation and high rates
of evaporation such as Shark Bay, Baffin Bay and
Florida Bay in the USA (Koch et al. 2007).