Project 6.4 - Laboratory experiments: Determine relative responses of benthic filter feeders to elevated sediment deposition, TSS and light reduction in controlled laboratory experiments. These laboratory experiments will enable the identification of lethal and sub-lethal thresholds, the potential of filter feeders to recover from dredging pressures, and the key pressures for each organism (sedimentation vs. turbidity vs. light attenuation), and thereby facilitate the development of pressure:response relationships. The threshold data obtained during this study are intended to be compatible with sediment plume modelling, enabling improved spatial risk analyses for tropical nearshore filter feeders, presently only involving sponges. Laboratory experiments will identify both lethal and sub-lethal thresholds of dredging on adult sponges.
Project 6.4 - Laboratory experiments: Controlled laboratory experiments will be performed at SeaSim in Townsville, where filter-feeding organisms will be exposed to different levels of TSS, sedimentation rates and light intensities that occur in dredging plumes. Sediment experiments will range from several days to several weeks, and will measure lethal and sub-lethal changes including alterations in pumping rates, symbiosis, photosynthesis, tissue damage and gene expression. The work will focus on sponges, which often dominate filter-feeding communities in WA. Sponge species and morphologies common to NWA and at the Wheatstone dredging site will be examined. Examples of different sponge morphologies include: massive, encrusting, cup, and erect. Morphologies assessed in experimental aquaria will be represented by different species as far as feasible, with targeted species shared between QLD and WA where possible. Species will include heterotrophic sponges that solely rely on filter feeding, and phototrophic sponges that obtain additional energy from photosynthetic symbionts.