In this data package you can learn about hypoxia in Saanich Inlet using graphs, images, video and data interpretation questions. Some background information on hypoxia can be found below and in the data package itself.
Low oxygen environments (hypoxic zones) are increasing throughout marine coastal ecosystems on a global scale (Diaz and Rosenberg, 2008). Hypoxic zones occur when oxygen levels fall under 1.5 ml/l, resulting in an environment where only a limited number of adapted species can thrive (Ocean Properties, 2013). Marine hypoxia can occur either naturally in deep basins, fjords and upwelling regions, or through anthropogenic disturbances. The main factors responsible for increasing hypoxic environments are eutrophication and climate change.
Eutrophication occurs when an excess of nutrients enters into the ocean either by natural or anthropogenic processes (i.e. industrial activities or mining practices) (Diaz and Rosenberg, 2008). The nutrient excess triggers massive phytoplankton blooms. When phytoplankton cells die, the high level of organic matter is decomposed by bacteria – a process which exhausts the oxygen supply (Ocean Properties, 2013).
Climate change increases sea surface temperatures, leading to reduced oxygen solubility and increased water stratification. When the water column is stratified, oxygen saturated surface waters no longer recharge bottom waters at a sufficient rate, leading to hypoxic conditions.
Ocean hypoxia can pose harmful effects on the growth, survival, reproduction and behavior of many marine species. Compared to other coastal and deep-sea environments, biodiversity is lower in hypoxic regions (e.g. Matabos et al., 2012).
Diaz R., and Rosenberg R. (2008). Spreading dead zones and consequences for ecosystems. Science. 321(5891). Pages: 926-929.
Ocean Properties (2013). Retrieved March 24. 2013, from http://venus.uvic.ca/research/ocean-properties/.
Matabos M., Tunnicliffe V., Juniper S.K., and Dean C. (2012). A year in hypoxia: epibenthic community responses to severe oxygen deficit at a subsea observatory in a coastal inlet. PLoS ONE. 7(9):e45626, DOI:10.1371/journal.pone.0045626.