Effects of local and global change on an inland sea: the Strait of Georgia, British Columbia, Canada

Abstract

Global changes manifest themselves in coastal waters depending on local oceanography and ecosystems. In this paper, we consider the Strait of Georgia as a case study. After examining physical and chemical processes and trends, we discuss consequences of change on geochemical cycling and biota. Several components of the system are vulnerable. Declines in pH and O 2 of basin waters, partly imported from the shelf and partly supported by carbon cycling within the strait, could reduce benthic and pelagic habitat. Sea level rise and storms will interact with coastal development to place critical habitat, such as low-lying estuaries, intertidal zones and mudflats, at risk. The decrease and earlier peak in zooplankton biomass may lead to changes in the food web that cascade to higher trophic levels such as fish and birds. Anadromous fish, already showing declines, are vulnerable to ocean regime shifts, increasing river temperatures, habitat destruction, harvesting and contaminants. For southern resident killer whales Orcinus orca, a species at risk, decline in Chinook salmon Oncorhynchus tshawytscha together with marine traffic and biomagnifying contaminants will lead to extirpation if no action is taken. Some stressors can be controlled only through international action to mitigate climate change. However, we have local control of fishing, habitat destruction, release of some contaminants and, to some extent, river flow and temperature. Acting to control these stressors will support resilience of biota in the face of inevitable global changes.

Oxygen in the deep Strait of Georgia, 1951–2009: The roles of mixing, deep‐water renewal, and remineralization of organic carbon

“…Even if all the organic carbon from all the wastewater outfalls were discharged directly into the deep basin, however, and if there had been no wastewater discharged before 1971, the organic carbon discharged by municipal outfalls would still be about a factor of 5 smaller than the amount required to have driven the observed decline in oxygen concentration. Pulp mills discharged about 6.7 3 10 9 mol yr 21 of organic carbon in the mid1990s (Johannessen et al 2003), similar to the increase required to have caused the decline in oxygen (if the waste had been discharged at 200 m), but the biochemical oxygen demand of the waste discharged into the Strait of Georgia or Fraser River declined by 88% between 1990(McGreer and Belzer 1999. Consequently, neither municipal wastewater nor pulp mill effluent could have caused the decline in oxygen.…”

“…4) suggest that more oxidation takes place here than at mid-depth in the southern Strait. This could be the result of the high primary productivity (euphotic zone 20-30 m; Masson and Peñ a 2009) and low dilution by inorganic particles from the Fraser River in the northern Strait and of the resulting higher concentration of organic matter in sinking particles in this area (Johannessen et al 2008). Alternatively, lower oxygen residuals in the north could arise from progressive deoxygenation of the mid-depth water as it transits northward from Haro Strait.…”

“…Primary production is a major source of organic carbon in the Strait of Georgia (Johannessen et al 2003). Since the phytoplankton are principally limited by light, a change in stratification due to a change in the timing of the Fraser River discharge (Morrison et al 2002) or in the frequency of summer wind storms could have increased primary production.…”

“…Dissolved organic carbon-The dissolved organic carbon (DOC) data have been published previously (Johannessen et al 2008) and are just presented here to help explain the observed distribution of oxygen in the water column. Briefly, DOC was measured in water samples collected during quarterly cruises in 2003 at the rosette sites marked in Fig.…”

Remote Sensing of Shallow Coastal Benthic Substrates: In situ Spectra and Mapping of Eelgrass (Zostera marina) in the Gulf Islands National Park Reserve of Canada

“…Applying these key wavelengths in the programming of airborne sensors, or the development of coastal based satellite spectral sensors, could yield effective mapping of eelgrass Zostera marina and associated benthic cover in the shallow coastal waters of Sidney Island, B.C., and possibly in other temperate coastal areas. These maps could be used as baseline inventory data and, when merged with other ancillary data layers (e.g., estuarine water flow and sediment loads, salinity, temperature, fish and invertebrate distributions), be used to report on the structure and functioning of coastal ecosystems [94,95]. However, it should be noted that species discrimination in the remote sensing of vegetation is achievable as long as the species and substrates under study are spectrally distinct over space and time [26].…”