Short-term variability and particle flux
Light in the Strait of Georgia
Fraser River plume
Acidification and Hypoxia
Sewage / wastewater in the Strait of Georgia
Arctic shelf sediments
Arctic change besides sea ice
Polyaromatic hydrocarbons on the BC coast
How to interpret contaminant profiles in sediments
Oxygen in the Strait of Georgia
Johannessen, S. C., Macdonald, R. W., Wright, C. A. and Spear, D. J. 2017. Short-term variability in particle flux: storms, blooms and river discharge in a coastal sea. Continental Shelf Research 143: 29-42.
A rain of sinking particles brings food from the ocean’s surface into the deeper water. The particles also help to bury carbon at the bottom of the ocean. The rain of particles is affected by events, such as storms and blooms. This paper shows the effects of river flow, rainstorms, phytoplankton blooms and jellyfish in the Strait of Georgia, Canada.
Near Vancouver, the rain of particles is heaviest in the summer, when the Fraser River flow is highest. The rain of particles is lower in the northern Strait. In the north, particle flux events occur throughout the year; they are linked to rainstorms and other local events. Short events contribute disproportionately to the annual flux of particles. Short-term variability is increasing with climate change. The importance of these events to the rain of food and to marine carbon sequestration will likely increase in the future.
Loos, E.A., Costa, M., and Johannessen, S. C. 2017. The underwater optical environment of the coastal waters of British Columbia. Accepted by FACETS, August 17, 2017.doi: 10.1139/facets-2017-0074.
The Strait of Georgia is mostly dark. The deepest part of the Strait is about 400 m deep, but beneath the turbid plume of the Fraser River, light only reaches the top 7 m. Farther from the river, green light penetrates as deeply as 20 m. However, the red and blue light mainly used by phytoplankton is gone by 10 m, everywhere in the Strait. The light is attenuated by particles, organic matter and water. The uppermost layer of water (7-20 m) flows out of the Strait, so the energy absorbed from sunlight is largely exported too. The rapid attenuation of light explains why phytoplankton only grow near the surface of the Strait of Georgia.
Pawlowicz, R. Di Costanzo, M. Halverson, E. Devred and S. Johannessen 2017. Advection, surface area, and sediment load of the Fraser River plume under variable wind and river forcing. Accepted by Atmosphere-Ocean August 15, 2017.
Suspended particles are important for a number of reasons. They block light and carry food for zooplankton. They also scavenge contaminants, including oil, out of surface water. The Fraser River is the largest source of particles into the ocean along Canada’s west coast. The particles flow out in a visible plume. This paper maps the plume throughout the year. The plume area and particle concentration increase with river flow. Wind strength and direction affect the location of the plume. Suspended particles remain in the plume for about two days.
Johannessen, S. C. and Macdonald, R. W. 2016. Geoengineering with seagrasses: Is credit due where credit is given? Environmental Research Letters 11: 113001. doi 10.1088/1748-1936/11/11/113001.
Marine plants take up carbon dioxide and make organic carbon. Some of the organic carbon is buried in sediments at the bottom of the ocean, where it can be stored for hundreds or thousands of years. Some scientists have suggested that seagrass meadows might store far more carbon than other types of marine sediments.
International organizations have begun to consider how to award carbon credits for protecting seagrass meadows. This paper shows that the current methods overestimate how much carbon is stored in seagrass meadows. This is important, because if carbon credits are awarded based on overestimates of carbon storage, the overall carbon emissions to the atmosphere might increase – opposite to the intended effect.
Ianson, D., Allen, S. E., Moore-Maley, B.L., Johannessen, S. C. and Macdonald, R. W. 2016. Vulnerability of a semienclosed estuarine sea to ocean acidification in contrast with hypoxia. Geophysical Research Letters doi 10.1002/2016GL068996.
Carbon dioxide is increasing in the atmosphere and causing climate change, including global warming. The ocean absorbs some of the carbon dioxide, which is causing seawater to become more acidic. At the same time, the concentration of oxygen in seawater is decreasing. Marine animals need oxygen to breathe. Usually, acidification and declining oxygen change together. This paper shows that in the Strait of Georgia, off the west coast of Canada, the bottom water is becoming acidic more quickly than the oxygen is decreasing.
This is because of the unusually strong mixing at the entrance to the Strait of Georgia, among the Gulf Islands. Oxygen dissolves quickly into the surface water in this area, and the oxygenated water mixes with the deeper water. When the mixed water flows into the deep Strait of Georgia, it replenishes the oxygen in the deep Strait. Carbon dioxide can’t escape from seawater so quickly, so the mixing does not help to reduce acidification so much.
Johannessen, S.C., Macdonald, R.W., Burd, B., van Roodselaar, A. and Bertold, S. 2015. Local environmental conditions determine the footprint of municipal effluent in coastal waters: A case study in the Strait of Georgia, British Columbia. Science of the Total Environment 508: 228-239.
Sewage discharge into the Strait of Georgia has been controversial, partly because of a lack of information about its effects.
There are biological effects near the Vancouver and Victoria outfalls. The effects are mainly due to low oxygen. Wastewater is negligible in the regional budgets of substances that have natural cycles. These include organic carbon, nitrogen, oxygen demand and metals. However, it is a major route of entry for flame retardants (PBDEs). PBDEs are found in computers, furniture and other household items.
Secondary treatment breaks down organic matter. It does not break down metals or persistent chemicals. Those are moved into the sludge. If the sludge is deposited on land, chemicals could leach into groundwater and streams.
Macdonald, R.W., Kuzyk, Z.Z.A. and Johannessen, S.C. 2015. The vulnerability of Arctic shelf sediments to climate change. Environmental Reviews 23: 461-479.
Continental shelves surround the Arctic Ocean. Sediment on the shelves provides habitat for bottom-dwelling animals. Organic matter and contaminants are transformed or buried in the sediment. The sediment is affected by ice, ocean and land. Arctic shelves react to climate change in the Pacific Ocean. They are also sensitive to changes on land, such as melting permafrost.
Macdonald, R.W., Kuzyk, Z.Z.A. and Johannessen, S.C. 2015. It is not just about the ice: A geochemical perspective on the changing Arctic Ocean. Environmental Studies and Sciences 5(3): 288-301.
Shrinking sea ice is the most visible sign of change in the Arctic Ocean. However, changes in freshwater inflow and the carbon cycle are also important. The Arctic is a small ocean surrounded by land and continental shelves. Land affects the Arctic Ocean more than other oceans. We need to increase our understanding of the changes in the land surrounding the ocean in order to understand fully the changes that are taking place within the ocean itself.
Yunker, M.B., Macdonald, R.W., Ross, P.S., Johannessen, S.C. and Dangerfield, N. 2015. Assessment of alkane and PAH provenance and potential bioavailability in coastal marine sediments subject to a north to south gradient of increasing anthropogenic sources in British Columbia, Canada. Organic Geochemistry 89-90: 80-116.
Polyaromatic hydrocarbons (PAHs) are organic compounds found in coal, gasoline and other fossil fuels. They are also produced when plants or fossil fuels are burned. In sediments near the large urban area around Vancouver, British Columbia, the PAHs are mainly from burning liquid fuel, like gasoline. In the more remote central and north coast, the main sources of PAHs are burning plants (like forest fires) and seepage from coal deposits.
The types of PAHs found near the city are more easily taken up by marine animals than are those found in the remote areas. Consequently, the marine animals that live in remote areas are likely less adapted to these compounds. They could be more vulnerable to the effects of spilled oil.
Kuzyk, Z.Z.A., Macdonald, R.W. and Johannessen, S.C. 2015. Calculating rates and dates and interpreting contaminant profiles in biomixed sediment cores. In J. M. Blais et al. (eds.) Environmental Contaminants, Developments in Paleoenvironmental Research 18, DOI: 10.1007/978-94-017-9541-8_4, p. 61-87.
Many contaminants stick to particles. The particles settle to the bottom of the ocean and build up, year after year. They preserve a record of the contaminants. However, bottom-dwelling animals mix the sediment. It is not simple to interpret a contaminant profile. This paper explains how to interpret contaminant profiles in marine sediment cores.
Johannessen, S.C., Masson, D. and Macdonald, R.W. 2014. Oxygen in the deep Strait of Georgia, 1951-2009: The roles of mixing, deep-water renewal, and remineralization of organic carbon. Limnology and Oceanography 59(1): 211-222.
Marine animals need oxygen to live. Oxygen in the deep Strait of Georgia has declined since the 1970s. The decline was caused by declining oxygen in the water that flows in from the Pacific Ocean. Local discharges, such as wastewater and pulp mill effluent, could not have caused the decline. Oxygen is low enough in the deep Strait of Georgia at some times of year to stress the animals that live there.
Hypoxic water (water with very little oxygen) flows in through Juan de Fuca Strait. When it reaches Haro Strait (among the Gulf Islands), the strong tidal currents mix the hypoxic water with oxygen-rich surface water. The mixed water flows into the deep Strait of Georgia in late spring. It replenishes the oxygen in the deep basin. Even if the water coming in from the Pacific becomes completely anoxic (containing no oxygen at all), the deep Strait of Georgia will not, because of the mixing in Haro Strait.