Why timing matters in a coastal sea: Trends, variability and tipping points in the Strait of Georgia, Canada

The timing of geochemical cycles in the Strait of Georgia is delicately poised, with, for example, deep-water oxygen reaching a hypoxic tolerance threshold in the spring, just before deep-water renewal replenishes the oxygen from outside. However, long-term trends in oxygen, temperature and timing of biological activity may lead to the crossing of crucial biological tipping points within this century. Timing is particularly important for monitoring. Relatively long records for basic water properties like temperature and salinity are accompanied by much shorter records for biogeochemical properties like dissolved O2, pH, nutrients and vertical flux, making it difficult to assemble a clear picture of the sorts of changes that may be occurring in the latter. A confident assessment of the ecological resilience of the Strait of Georgia will require longer time series of biological and geochemical properties that are collected with consideration for the strong seasonal variability.