eCite Digital Repository

Spatial and temporal patterns of factors influencing phytoplankton in a salt wedge estuary, the Swan River, Western Australia


Thompson, PA, Spatial and temporal patterns of factors influencing phytoplankton in a salt wedge estuary, the Swan River, Western Australia, Estuaries, 21, (4B) pp. 801-817. ISSN 0160-8347 (1998) [Refereed Article]

DOI: doi:10.2307/1353282


During 1995 the phytoplankton in the Swan River were intensively sampled to assess biomass and species composition. Continuous measurements of fluorescence, salinity, and temperature were made weekly during 40 km sampling trips along the estuary and used to map the seasonal progression of the algal biomass. Weekly measurements of primary production were made and used to model net primary production from the vertical distribution of biomass, irradiance, and phytoplankton species composition. Potential nutrient limitation was assessed with 'all but one' nutrient bioassays. The results indicate a complex mixture of potentially limiting factors, which vary in time and space. Although the data sequence is short, it suggests a annual succession pattern of diatoms, chlorophytes, diatoms, and finally dinoflagellates and cryptophytes in late summer-autumn. Peak seasonal biomass was observed during January to April. Mean annual chlorophyll a biomass was greatest in upstream stations (5-9), where estimates of net primary production rates averaged 1.55 g C m -2 d -1 and gross primary production was 800-1000 g C m -2 yr -1 . Potential nutrient limitation was most severe from November to May, although not during January 1995. Based on bioassay results, during the period of greatest potential for nutrient limitation, nitrogen was 15 to 30 times more limiting to biomass development than phosphate. Runoff due to consistent rainfall during winter eventually breaks down stratification and flushes the estuary with low-salinity, nutrient-rich water, producing a light-limited, nutrient-rich aquatic ecosystem. Timing and magnitude of physical forcing events, mainly rainfall, appear critical in determining the susceptibility of this ecosystem to summer and autumn algal blooms.

Item Details

Item Type:Refereed Article
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Environmental Management
Objective Group:Coastal and estuarine systems and management
Objective Field:Coastal and estuarine systems and management not elsewhere classified
UTAS Author:Thompson, PA (Dr Peter Thompson)
ID Code:14251
Year Published:1998
Web of Science® Times Cited:41
Deposited By:TAFI - Aquaculture
Deposited On:1998-08-01
Last Modified:2011-08-09

Repository Staff Only: item control page