The effects of treated sewage effluent on three species of marine macroalgae

The early life stages of the macroalgal species Phyllospora comosa, Hormosira banksii and Macrocystis angustifolia were exposed to treatments of sewage effluent, copper, chromium and reduced salinity. Germination and mortality of P. comosa and H. banksii zygotes and embryos, and germination and germination tube growth of M. angustifolia spores were utilised as acute toxicity test endpoints. Germination bioassays were of 48 hours duration whilst mortality bioassays were conducted over 96 hours. Growth of all three species and sporophyte production of M angustifolia were utilised as chronic bioassay endpoints. These tests were conducted over 2-3 weeks. It was found that sensitivity of test end points varied depending on exposure time. Generally longer exposure times resulted in significantly lower threshold concentrations. Growth and sporophyte production or reproduction bioassays showed greater sensitivity in the test species, whilst the shorter tests tended to produce higher threshold concentrations. Primary treated effluent exerted greatest effects on the early life stages of the algae followed by chlorinated secondary and secondary treated effluent