Three replicates of seawater (100 mL) were sampled at each site and depth and filtered through bonnet syringe Minisart filters (0.45 μm pore size, Sartorius Stedim, Dandenong, Australia) to remove large particles. Filtrates were then stored at—20°C
until further analysis. Prior to analysis, the samples were thawed and mixed before injecting approximately 10 mL of each sample into the FIA in duplicate for a total of 6 replicates per sample. The detection limits were 40 nM for dissolved silica species, 70 nM for ammonium, 30 nM selleck compound for orthophosphate and 70 nM for nitrate/nitrite. The method was calibrated using standard solutions prepared in 0.6 M sodium chloride, corresponding to typical seawater salinity values of 35 PSU. The concentration of chlorophyll a (Chl a) was measured every month using methanol extraction and subsequent fluorometric determination ( Welschmeyer 1994). Seawater (600 mL) was filtered in triplicate through 47 mm, glass microfibre filters (1 μm pore size, Filtech, Fairy Meadow, Australia), using a vacuum pump and a filtration ramp. The filters were then wrapped in aluminium foil and stored at—20°C. For analysis, the filters were placed in methanol (5 mL) for 24 h at 4 °C in the dark, and the concentration of the Chl a dissolved in the methanol was determined using a Turner 450 fluorometer, previously
calibrated with Chl a extracted from Anacystis Everolimus nidulans (Sigma Chemicals, St Louis, MO, USA).
At each site and depth, 1 L Protein tyrosine phosphatase samples of seawater were taken and preserved with Lugol’s iodine added to each bottle (0.5%) final concentration, Hajdu et al. 2007) for identification and enumeration of phytoplankton species (>5 μm). Identification and enumeration of phytoplankton was carried out every two weeks by Microalgal Supply Service (Ormond, Victoria, Australia). The cells were identified up to the genus or species level based on their key taxonomic features ( Tomas 1997, Hallegraef et al. 2010) and grouped according to their size and shape. Wind speed [m s−1] and direction data [i.e. northerly/southerly (NS) and easterly/westerly (EW)] were provided by the Australian Bureau of Meteorology and measured by the Adelaide airport weather station. The average wind was entered into a coordinate system where positive NS components indicated upwelling-favourable wind conditions and negative NS components indicated downwelling-favourable wind conditions and corresponded to the dimensionless empirical drag coefficient over 14 days prior to the date of sampling. Upwelling- or downwelling-favourable conditions were determined on basis of the Ekman transport associated with northerly and southerly wind conditions along the coast of the Gulf. All environmental and biological data were tested for normality using the Kolmogorov-Smirnov test (Zar 1999).