Variation in sea temperature and the East Australian Current in the Solitary Islands region between 2001-2008 |
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Authors: | Hamish A Malcolm Peter L DaviesAlan Jordan Stephen DA Smith |
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Institution: | 1 Solitary Islands Marine Park, NSW Marine Parks Authority, PO Box 4297 Coffs Harbour Jetty, NSW, Australia 2450 2 NSW Department of Environment, Climate Change and Water, 59-61 Goulburn St, Sydney, NSW, Australia 2000 3 NSW Department of Environment, Climate Change and Water, Locked Bag 800, Nelson Bay, NSW, Australia 2315 4 School of Environmental and Rural Science, University of New England, National Marine Science Centre, PO Box 4321, Coffs Harbour, NSW, Australia 2450 |
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Abstract: | Improved understanding of the East Australian Current (EAC) and sea-temperature patterns within the Solitary Islands region of northern New South Wales, an area where tropical and temperate faunas overlap, is an essential step in explaining cross-shelf gradients in biotic patterns. Sea temperature at ∼10 m was logged using thermistors at seven stations every 30 minutes between January 2001 and December 2008. Stations were replicated in three distance-from-shore categories (<1.5; 1.5 to 6; and >6 km from the coast), corresponding with predominant assemblage patterns of reef fish. Daily, monthly, seasonal and yearly sea-temperature patterns were compared between and within stations and distance-from-shore categories. SST images were examined to determine the role of the EAC in producing short-period (2 to 4 days) temperature anomalies. Sea temperatures ranged between 16.6-27.5 °C and were highest offshore and lowest inshore. Offshore sites experienced average temperatures ∼1 °C higher than nearshore sites over the 8-year study. There was considerable variation in sea temperature between years, with 2002 and 2006 being the warmest and 2007 the coolest. These patterns correspond with strong inter-annual variability of the EAC at the scale of the Solitary Islands region. The EAC influenced shelf waters most strongly during late spring/summer when temperatures were also most variable over the smallest temporal scales (hours, days). Short-period anomalies between and within stations could largely be explained by variable encroachment of the EAC across the shelf and/or colder intrusions of water forming adjacent to the coastline. Previous assumptions that the EAC strongly influences gradients in the distribution of tropical species in this nearshore region are strongly supported. |
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Keywords: | Cross-shelf pattern Sea Surface Temperature Solitary Islands Marine Park Spatial and temporal scale |
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