摘要：Coastal hypoxia is increasing in the global coastal zone, where it is recognized as a major
threat to biota. Managerial efforts to prevent hypoxia and achieve recovery of ecosystems
already affected by hypoxia are largely based on nutrient reduction plans. However, these
managerial efforts need to be informed by predictions on the thresholds of hypoxia (i.e. the
oxygen levels required to conserve biodiversity) as well as the timescales for the recovery of
ecosystems already affected by hypoxia. The thresholds for hypoxia in coastal ecosystems
are higher than previously thought and are not static, but regulated by local and global
processes, being particularly sensitive to warming. The examination of recovery processes
in a number of coastal areas managed for reducing nutrient inputs and, thus, hypoxia
(Northern Adriatic; Black Sea; Baltic Sea; Delaware Bay; and Danish Coastal
Areas) reveals that recovery timescales following the return to normal oxygen
conditions are much longer than those of loss following the onset of hypoxia,
and typically involve decadal timescales. The extended lag time for ecosystem
recovery from hypoxia results in non-linear pathways of recovery due to hysteresis
and the shift in baselines, affecting the oxygen thresholds for hypoxia through
time.
