The Phytoplankton Ecology of Wilson Inlet, Western Australia - Nutrient Limitation of Phytoplankton Biomass

Full description

Nutrient deletion bioassays were applied over a one-year period to the phytoplankton community of Wilson Inlet. The bioassay data was supplemented with in situ measurements of physical and chemical variables to provide an indication of the nutrient status of the estuary and of the potential for the phytoplankton to become nutrient limited.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Three study sites were chosen for bioassay experiments; site 1 located in the western basin nearest the ocean, site 2 in the mid-estuary and site 3 in the eastern basin proximal to teh Hay and Sleeman Rivers (see Fig. 3.1 in thesis). Methods for the collection of physical, chemical and biological data at teh three bioassay sites are given in section 2.3.2 and 2.3.3 of the thesis. The physical, chemical and biological water quality data presented in this chapter were collected from January 1997 to November 1998.

Statement: - Bioassays - Between October 1997 and December 1998, 20 bioassays were conducted on the resident phytoplankton community in Wilson Inlet. An integrated water column sample was collected at each site by mixing 1-L of water from 0.5 m intervals from surface to the bottom. Within 24 h of colelction, 40 mL of integrated sample was incubated, in triplicate, within 50 mL borosilicate treatment tubes with Teflon lined caps. Treatments were incubated at an irradiance of 200 umol photons m-2 s-1 ('cool white' fluorescent bulbs) with a light:dark ratio adjusted to track the ambient photoperiod (between 14:10 summer and 12:12 winter, L:D). Temperature was adjusted to teh mean temperatureof the three sampling sites measured at the time of sample collection. Treatments were prepared by the addition of nutrients based on the recipe of (Harrison et al., 1980) at a concentration considered high enough to saturate the intial growth rates (see Table 3.1). Each treatment was prepared by omitting one of the nutrients from the full compliment. A control with no added nutrients and a treatment with all added nutrients were prepared to enable a comparison of each treatment biomass at the end of incubation. At intervals of 24 h the in vivo fluorescence of each treatment was measured by inserting the whole treatment tube into a Turner Designs model 10 fluorometer. At the end of exponential growth a 30 mL sub-sample was filtered through a GF/C filter and the chlorophyll a concentration of each treatment was estimated by the the in vitro fluorometric method (Parsons et al., 1984). All bioassay treatments and controls were grown in triplicate. Where necessary data were transformed to achieve normality and homoscedasticity prior to statistical analysis.

Notes

Credit
National Eutrophication Management Program and Water and Rivers Commission of WA (now Department of Water)