Huon Aquaculture Company Trumpeter EIS Storm Bay MFDP Comparison to historical data - CSIRO studies 1985-89 Harris et al., (1991) undertook weekly observations at a sampling station in Storm Bay (43°10'S, 147°32'E) over a period of 4 years from March 1985 to March 1989. They provided strong evidence for the very dynamic nature and variability of the waters in Storm Bay and the strong influence of wind events in the productivity of the system: Sea surface temperature (SST) could warm by 2.5°C from the cool, windy summer of 1986-87 to 1989. Warm years were characterized by an increased north-easterly, subtropical influence and cool years by an increased south-westerly, subantarctic influence. Intrusions of subtropical water could be detected by increased salinities and very low dissolved inorganic phosphorus Phosphate concentrations in Storm Bay in the summer of 1988-89 were one-half of the concentrations measured in 1985. Winter nitrate concentrations in 1988 were also one-half of average. Total nitrogen (range 2-20uM), phosphorus and dissolved organic carbon (range 60- 200uM) concentrations in surface waters (10m depth) fell steadily throughout the sampling period. Pulses of algal growth (measured as Chlorophyll) followed peaks in the 40-day wind oscillation and resulted from the re-suspension of nutrients regenerated by decomposition in bottom waters. Surface nitrate concentration ranged from 0-4.5uM and bottom nitrate was always higher with a maximum of 8uM, surface phosphate ranged from 0-0.8uM, and Chlorophyll ranged from 0.5-8ug/l. Windy periods (such as the summer of 1986-87) were marked by high nitrate and dissolved organic nitrogen concentrations in surface waters. Episodes of 'new' production therefore followed periods of increased westerly wind stress. There was thus a strong interaction between the time scales of wind events, nutrient uptake, phytoplankton growth, grazing, sedimentation, decomposition and re-suspension. Particle size data and data on the size fractionation of the zooplankton biomass indicated a strong trend towards more oligotrophic conditions in surface waters during the warm, calm period after 1987 The phytoplankton community was dominated by small flagellates, indicative of regenerated production rather than the large diatoms characteristic of new production in the cool, windy years. The very oligotrophic conditions of the summer of 1988-89 led to small copepods dominating, and the elimination of all large zooplankters 110 Huon Aquaculture Company Trumpeter EIS Storm Bay MFDP The entire chain of events appears to have been associated with the major La Nina 'Cold Event' of 1988. Crawford et al., (2011): ‘A comparison of the preliminary environmental data collected in 2010 with data collected by CSIRO at the same site in Storm Bay in 1985-89 indicates that salinities tended to be higher in 2010 in autumn and early winter compared with over two decades ago and temperatures are now tending towards the higher values of 1985-89. Phosphate are clearly lower for most of the year in 2010, whereas nitrates are generally similar although indicate a pattern of higher winter values over an extended winter period. Chlorophyll a values in 2010 were mostly lower than in the 1980’s, implying lower productivity. These preliminary data indicate changes are occurring and if the indications of lower productivity are correct then a reduction in fishery output can be expected. However additional monthly data are required to determine whether change is long term or merely interannual variability, and to provide the replication necessary for statistical analysis. When comparing results over time there is a concern that the techniques and analytical equipment used will have changed so the results may not be directly comparable. However, one of the co-investigators in the current project, Lesley Clementson, conducted the nutrient analyses of the data from 1985-89. The flow injection technique she used was relatively new at the time and is still used today. The auto analyser type system that was used for the analyses in 2009-10 is probably capable of lower detection limits compared to those of the 1980's, but the levels recorded in Storm Bay are unlikely to show any difference. Chlorophyll a results, however, should be viewed with caution because both the extraction and analytical techniques differed between the two sampling periods.’ 5.1.5 Sediments Sediment chemistry Refer to the Initial Environmental Assessment (Appendix H). The Geophysical survey and mapping report provided by CSIRO showed the sediments to be highly uniform across the whole survey area and similar to the sediments found at the south of Trumpeter Bay (SB)1-4 sites in the previous 2014 survey for Amendment 1. The sediments were described as fine to medium sands with some silt in places. From the ROV survey the majority of sites shared the common features of fine to medium-grained rippled sands, with varying amounts of shells and shell grit or gravel. Shells and shell grit appeared more prevalent towards the northern and more shallow end of the survey area and were especially prevalent at sites R1 and R8. The results for the sediment grab samples mirror the film footage in that all sites were composed of fine to medium rippled sands, yellow-brown in colour. Again, the two 111 Huon Aquaculture Company Trumpeter EIS Storm Bay MFDP exceptions were sites 1 and 8 where larger shell debris dominated the samples. Dark grey/black silt was also present beneath the surface at several sites across the survey area. The fine to medium grained sands dominating the whole survey area are broadly indicative of a sedimentary environment with moderate agitation of seabed sediments. These patterns are considered typical of sediments in exposed locations. The overall similarity in particle size distribution between sites implies similar depositional environments. Extract from the Marine Farming Development Plan for Storm Bay off Trumpeter Bay North Bruny Island (1998): ‘Aquahealth et al (1996) assessed sediment and biological quality at two sites within the exploratory lease (100m apart) and two control sites off the lease site (1.4km apart), prior to placement of the exploratory fish cage. The bottom was found to be typically sand with minor corrugations. Across all four sites the sediment profile was typically yellow sand to a depth of 3-4 cm, and then becoming a yellow- brown sand at further depths. The sediments had a clayey nature and gritty content (mainly due to fine shell fragments). Rocks and boulders were not observed. The pH values of sediments ranged between 7.79 and 8.18, reflecting the marine conditions. Temperature values ranged between 9.8oC and 12.5 oC, reflecting the winter sampling period. The Eh values ranged between 303 and 310 mV and this indicated that the water column was well oxygenated at the surface, with the Eh value decreasing with increasing sediment depth. The % Loss-On-Ignition values ranged between 2.6% and 3.7%, indicating a low to moderate level of organic enrichment.’ Benthic infauna The Benthic Infauna observed in the latest survey work is broadly consistent with all previous survey work in the Storm Bay off Trumpeter Bay North Bruny Island, MFDP. The Initial Environmental Assessment for this proposed zone is included in Appendix H. It notes that larger infauna found in multiple grab samples across the survey area included heart urchins, Screw shells, bivalves and gastropods, with the occasional hermit crab.’ In addition, ‘There appeared to be numerous Anthozoa (suspected Edwardsiidae) at most sites.’ Extracts from the original Trumpeter Bay lease (approximately 3.5-4kms to the south of the proposed Yellow Bluff zone) Environmental Baseline surveys can be found at Appendix A: In the original Trumpeter Bay 30ha lease survey (Dec 2014), it was noted that ‘Benthic infaunal analysis revealed high faunal diversity, with a total of 543 individuals from 68 species identified across the 12 samples. Faunal communities were dominated by crustaceans, accounting for 48.8% of individuals and 41.2 % of species identified. The 112 Huon Aquaculture Company Trumpeter EIS Storm Bay MFDP remaining fauna was mainly comprised of bivalves and polychaetes, which were comparable in terms of abundance and diversity. Other fauna, including echinoderms, nemerteans, nematodes and ascidians, were recorded in low numbers. The most common families recorded included Euphilomedidae (ostracod), Veneridae (bivalve mollusc), Phoxocephalidae (amphipod) and Spionidae (polychaete). Observed faunal patterns were within the range expected for an unimpacted ecosystem, with relatively diverse communities and low levels of single species dominance. Based on the benthic faunal patterns present, any future benthic impacts should be readily observable.’ During the subsequent Trumpeter Bay lease 70ha baseline survey (Sept 2016) Benthic infaunal analysis revealed high faunal diversity, with a total of 2390 individuals from 109 taxa identified across the 12 samples. Faunal communities were dominated by crustaceans, accounting for 36.5% of individuals and 41.3 % of species identified. The remaining fauna was mainly comprised of polychaetes, anthozoans and molluscs. Other fauna (including ascidians, echinoderms, nemerteans, nematodes, phoronids, platyhelminths and sipunculids) were recorded in low numbers. The most common family recorded during the survey was the anthozoan family Edwardsiidae. Overall, this taxa accounted for 22.5% of all animals counted. While this group is occasionally recorded from benthic samples in Tasmanian coastal; waters, the densities recorded during the current survey were unusually high. In past surveys of the Trumpeter Bay area, anthozoans were either absent or present in low densities. It appears that a significant recruitment event has occurred for this particular taxa.’ An extract from the Marine Farming Development Plan for Storm Bay off Trumpeter Bay North Bruny Island (1998): stated that ‘The density of invertebrates (average density of 1340 individuals per m2) was within the range for those found in other South East Tasmanian sites (eg.