Using Developing Embryos of Hormosira banskii (Phaeophyta) as a Marine Bioassay System

Toxicity tests using developmental stages of Hormosira banksii (Phaeophyta) identify ammonium as a damaging component of secondary treated sewage effluent discharged into Bass Strait, Victoria, Australia

“…Artificial seawater (ASW, modified from Maier & Calenberg 1994) was used for all experiments to avoid bacterial contamination, variability in seawater constituents, and the occurrence of endochites (Kevekordes & Clayton 1996). ASW was made from analytical reagent (AR) grade chemicals dissolved in Milli-Q filtered water, adjusted to 34 parts per thousand salinity (‰ S) and a pH of 7.8 to allow comparisons with other related toxicity studies (Stauber et al 1998).…”

“…Eggs were released from 6 female plants into 1 container of ASW to ensure a common gene pool for all treatments in the experiment. The suspension of eggs was filtered through a nylon mesh (0.2 mm) to remove debris and small animals (Kevekordes & Clayton 1996). Sperm were released from 5 plants into 1 container of ASW, again to ensure a common gene pool for all treatments in the experiment.…”

“…Treatments were gently swirled 6 to 7 min after gamete mixing, to ensure even mixing of newly fertilized/unfertilized eggs before 10 ml aliquots were decanted into petri dishes each containing a coverslip (used for microscope observations). Embryos were grown under Sylvania Gro-lux wide spectrum fluorescent tubes (40 W) with a photon irradiance of 25 µmol m -2 s -1 on a 12:12 h light:dark cycle at 15°C (Kevekordes & Clayton 1996).…”

“…Once observations were made, the coverslip was discarded and a new petri dish used to assess the next developmental feature (Kevekordes & Clayton 1996). The presence of a cell wall was detected with the fluorochrome, calcofluor white (Hughes & McCully 1975).…”

“…Recent studies (Doblin & Clayton 1995, Kevekordes 2000 have shown that developing H. banksii embryos are also susceptible to sewage effluent at the median concentration occurring at Boags Rocks (40%) and that damage is evident in zygotes 24 h or older (Kevekordes 2000). These studies have also identified an ecologically relevant bioassay system where development occurs as a series of welldefined events that are easily quantified (Kevekordes & Clayton 1996) and therefore able to be used as endpoints in toxicity studies.…”