Physical properties and processes in the Perth Canyon, Western Australia: Links to water column production and seasonal pygmy blue whale abundance
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The link to the journal’s home page is: http://www.elsevier.com/wps/find/journaldescription.cws_home/503344/description#description. Copyright © 2009 Elsevier B.V. All rights reserved
The oceanography of the Perth Canyon, off southwestern Australia, was examined through two major field excursions in austral spring/summer 2003/2004 combined with previous results from field analysis and numerical simulations. Water properties were used to identify water masses and vertical displacement. The field cruises and numerical simulation indicated unique circulation features of the Leeuwin Current and Undercurrent within the canyon associated with the topographic features. The input of nutrients to the euphotic zone occurred sporadically as the Leeuwin Current generally suppressed upwelling, although the Perth Canyon had increased nutrient concentrations within its rims. The distribution of chlorophyll in the surface layers indicated high spatial variability, with a prevalent deep chlorophyll (and phytoplankton biomass) maximum at ~80 m. Depth-integrated primary production within the study region ranged from 360 to 760 mg C m-2 d-1, which was on average 2.5 times higher than rates measured in continental shelf and off shorewaters north of the canyon.Aggregations of krill and other acoustic backscatter targets were concentrated near the head of the canyon at a range of depths, which may have been promoted by the circulation. The findings here are consistent with seasonal variations in wind and insolation, along with variations in the Leeuwin Current, influencing the seasonal changes and mesoscale features within the region, while the canyon promotes localised upwelling, and enhances both pelagic production and physical aggregation of plankton to attract the whales. Canyon processes must be combined with outside factors to allow upwelled nutrients to reach the photic zone. It is concluded that a combination of factors, rather than one factor alone, contributes favourably tothe appearance of feeding blue whales in the Perth Canyon during the summer.
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Rennie, Susan Jane (2005)Submarine canyons are important to continental shelf ecosystems. They have a strong influence on shelf circulation and the distribution of biota. The Perth Canyon is a long, deep canyon on the Western Australian coastline ...
Rennie, Susan; Pattiaratchi, C.; McCauley, Robert (2009)Surface and sub-surface currents along the ocean boundary of Western Australia were simulated using Regional Ocean Modelling System (ROMS) to examine the circulation within the Perth Canyon. Two major current systems ...
Thermal structure above the Perth Canyon reveals Leeuwin Current, undercurrent and weather influences and the potential for upwelling.Rennie, Susan; McCauley, Robert; Pattiaratchi, C. (2006)The Perth Canyon is a focal feeding area for pygmy blue whales on the Western Australian coast. Studies aimed at elaborating oceanographic mechanisms within the canyon were conducted between 2002 and 2005. Strings of ...