Publication Date

12-2000

Series Number

123

Publisher

Fisheries Western Australia

City

Perth

ISBN

0 7309 8439 7

ISSN

1035 - 4549

Abstract

The measurement of chlorophyll-a (a simple estimate of phytoplankton biomass) is often used as an indicator of water quality. Chlorophyll measurements are relatively sparse for most of the Western Australian continental shelf, although there are areas such as the Perth metropolitan coastal zone, Wilson Inlet and the Albany harbours where some intensive studies have been undertaken.

This review of both published and unpublished chlorophyll concentrations in Western Australian waters has shown a high degree of variability in space (both horizontally and vertically) and time, and statistics on the seasonal distribution of chlorophyll have been derived for those regions with sufficient chlorophyll data. Conclusions from these in situ observations have been supported by satellite remote sensing of ocean colour using archived Coastal Zone Colour Scanner (CZCS) satellite imagery.

South-eastern Indian Ocean waters are generally nutrient- and chlorophyll-poor, with chlorophyll concentrations generally well below 1 µg/L and, therefore, probably unsuitable for successful bivalve aquaculture. These concentrations are much lower than in the upwelling regions off the west coasts of southern Africa and South America because of the warm low-nutrient Leeuwin Current. Chlorophyll levels in coastal areas and semi-enclosed water bodies on the Western Australian coast are generally higher than in the open ocean, with seasonal mean chlorophyll concentrations sometimes exceeding 2 µg/L and occasionally reaching 5 µg/L. Such elevated chlorophyll levels are, however, largely due to natural input of nutrients regionally exacerbated by anthropogenic influences like agriculture runoff and sewage. Present chlorophyll levels in these regions should be viewed as transient, being influenced by potentially varying nutrient loadings, as further industrial development occurs and countered by remedial management practices. Peak chlorophyll levels in Western Australia’s coastal waters generally occur in winter with the lowest concentrations in summer and autumn.

An atlas is presented depicting seasonal chlorophyll concentrations for those regions where data coverage is adequate: Perth metropolitan waters, the Peel-Harvey system, Wilson Inlet and the Albany harbours region. Due to the high level of phytoplankton patchiness, more detailed in situ chlorophyll (and other) measurements are recommended in specific areas where future aquaculture ventures are proposed.

Number of Pages

67

Keywords

Mariculture industry, Impact, Environmental management, Western Australia, Productivity, Chlorophyll, Indian Ocean, Coastal, Estuarine

Disciplines

Aquaculture and Fisheries | Environmental Indicators and Impact Assessment | Management Sciences and Quantitative Methods | Marine Biology

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