Annually recurrent diatom blooms in spring along the New South Wales coast of Australia

Abstract

Blooms of phytoplankton (100-280 mg chlorophyll a m-1) occur on the continental shelf off Sydney in the spring of most years. These sudden chlorophyll increases (more than 10 times the normal algal biomass) are due to short-lived diatom blooms that evolve in a predictable sequence from small chainforming species (Nitzschia, Thalassiosira) to large centric species (Lauderia, Rhizosolenia) and eventually to large dinoflagellates (Protoperidinium). Two research cruises (October 1981, September 1984) were conducted to define the longshore extent of this phenomenon. Diatom blooms were widespread along the whole New South Wales coastline, occurring in the 700-km-long region from Cape Hawke in the north (32°S), where the East Australian Current separates from the coast, to Maria Island off Tasmania in the south (43°S). Hydrological mechanisms of these annually recurrent enrichments are related to the action of the East Australian Current and are unlike those triggering spring blooms in temperate European waters. Implications of these diatom blooms for coastal fisheries along the New South Wales coast are briefly discussed.

Spatial and temporal distribution of tropical phytoplankton species and biomass in the Gulf of Carpentaria, Australia

“…These phytoplankton are generally highly variable in abundance, which may be related to pulses in the biomass of diatoms. In contrast to the distinct succession patterns observed in temperate regions of the world (Guillard & Kilham 1977, Hallegraeff & Jeffrey 1993, the diatoms in Albatross Bay did not show a seasonal pattern of succession. Succession patterns are often determined by the loss of diatoms through diffusion, sinking and grazing, as well as the rate of nutrient regeneration.…”

Long-term changes in temperate Australian coastal waters: implications for phytoplankton

“…Interannual variability in Leeuwin Current flow and sea surface temperature is related to the El Niño-Southern Oscillation (ENSO) phenomenon (Feng et al 2003). In contrast, waters of similar latitude on the Australian east coast are approximately twice as productive (Jitts 1965) and show a spring phytoplankton bloom with a second bloom in late summer to early autumn (Humphrey 1963, Hallegraeff & Jeffrey 1993. Sporadic increases in primary productivity on the southeast coast are the result of EAC activity that uplifts nutrient-rich slope water onto the shelf and close to the surface (Oke & Middleton 2001), sometimes in association with warm-core (Tranter et al 1986) or cold-core (Gibbs et al 1997) eddy formation, often resulting in coastal diatom blooms (Hallegraeff & Reid 1986 (Table 1).…”

Nutrient enrichment off Port Stephens: the role of the East Australian Current

“…In January 1997, a Noctiluca Scintillans bloom occurred off Port Stephens (Ajani et al, 2000). Port Stephens is a site of frequent algal blooms (Hallegraeff and Jeffrey, 1993). The coastal circulation near this location is dominated by the southward flowing EAC that is highly energetic in this region, with currents of up to 2 m s À1 flowing adjacent to the shelf break (Church and Cresswell, 1986).…”