The effects of human impacts on Antarctic sponge species in the Ross Sea

The effects of human impacts on the microbial and chemical ecology of Antarctic sponge species was investigated. Sponges dominate many of the shallow marine Antarctic habitats and due to the large volumes of seawater that they filter are ideal indicator organisms for assessing benthic conditions. The microbial flora and the symbiotic relationship associated with several Antarctic sponge species (Homaxinella balfourensis, Kirckpatricia variolosa, Latrunculia apicalis, Mycale ascerata and Sphaerotylus antarcticus) was examined by collecting samples of each sponge species at sites of high impact (Winterquarters Bay, McMurdo sewage outfall, Scott Base RO Intake), low impact (Cape Armitage) and pristine conditions (Pram Point, Turtle Rock and Cape Evans). Tissue samples were taken for microbial cultivation on a minimum of 6 media, electron microscopy, 16S rRNA sequencing, DNA fingerprinting and DNA probing where the DNA was frozen for DNA and chemical analysis. These techniques were used to monitor changes in microbial diversity with increasing levels of pollution stress. The level of contamination at each site is being defined by heavy metal, hydrocarbon and nutrient analysis of sediments and bivalves and fecal coliform counts from seawater and sediment. Samples were analysed for heavy metals, total nitrogen and phosphorous, hydrocarbons, persistant organic pollutants and tributyltin (TBT). Microbial symbionts are increasingly being identified as the source of many compounds isolated from sponges. The chemical ecology of Antarctic sponges was examined and the within and between site biochemical variation, and the influences of pollution on secondary metabolite production both as an indicator of stress and as a source of novel and potentially valuable chemistry was investigated from these samples. Glass slides were deployed to examine the relative development of biofilms and recruitment at each site after one year. The total microbial communities were described using cultivation and molecular techniques to analyse population changes with respect to increasing levels of pollution as microbial biofilms can also have a strong influence on the settlement of many reef invertebrates. The key outputs of this research include a series of diagnostic test for measuring sub-lethal stress responses that can provide environmental managers with valuable predictive information, and a library of novel Antarctic microbial symbionts as well as invertebrate extracts for natural product screening programs.