EARTH SCIENCE | AGRICULTURE | AGRICULTURAL AQUATIC SCIENCES | AQUACULTURE
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The threatened status of shellfish reefs has been well established globally (e.g Beck et al 2011) however the ecological consequences of these losses is still largely unknown. In Australia, shellfish reefs are one of the most imperilled marine habitat types (Gillies et al 2018), due to historical overharvest and widespread eutrophication of coastal waters through the use of fertilizers, livestock and human waste. Marine bivalves are important ecosystem engineers providing habitat, shelter and a food source for other species in benthic soft-sediment environments. In addition, filter-feeding bivalves link benthic and pelagic components of ecosystems through filtration and excretion. Through their filter feeding, they produce large amounts of faeces (digested seston) and pseudofaeces (rejected particles bound up in mucus) which are deposited on the benthos. This process brings energy and nutrients from the pelagic system to the benthic system (bentho-pelagic coupling). The removal of large quantities of seston can serve an important ecosystem function by improving water quality and clarity. The filtration of water performed by bivalves has been demonstrated to reduce water turbidity, improving light penetration and thereby enhancing growing conditions for seagrasses (Wall et al 2008). In systems where healthy populations of bivalves remain, they can filter a volume equivalent or larger than the entire estuary volume within the residence time of the water (zu Ermgassen et al 2013). While such densities of oysters are rare today, this highlights the critical ecosystem services that are lost when oyster reefs decline. Furthermore, it demonstrates the potential functions that can be regained through oyster reef restoration. Given the increasing awareness of the decline of these ecosystems, interest in restoration efforts to restore critical ecosystem functions has been growing. However, conservation and restoration decision making is underpinned by reliable quantification of relevant ecosystem services (zu Ermgassen et al 2016). For example, there are plans to restore some of the natural oyster reefs of Sydney Rock Oyster (Saccostrea glomerata) in Port Stephens, New South Wales. One of the main drivers motivating this restoration project is restoring lost ecosystem services. The filtration rates of Australian oysters has been demonstrated in aquarium studies using filtered water augmented with algae, yet little is known about filtration and biodeposition rates of oysters using raw seawater. In this study, we provide the first evaluation of the filtration and biodeposition rate of four species of bivalves using raw seawater, providing a proxy for natural biodeposition rates. As such, this study provides a first indication of the filtration/nutrient cycling function that may be restored following oyster restoration efforts.
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This dataset depicts the location of the Broadscale Environmental Monitoring Program (BEMP) sites. It was compiled from data provided by EPA Tasmania, IMAS and published reports. BEMP was initiated in 2009 by the State Government to provide knowledge and information on ecosystem function in the D’Entrecasteaux Channel and Huon Estuary. BEMPs have been developed for all marine farming regions. The objective of each program is to document (on an ongoing basis) broadscale spatial and temporal trends for key environmental parameters, allowing assessment of the environmental effects of finfish aquaculture in Tasmania. Marine farming licence conditions include participation in respective BEMPs. The BEMP program initially covered assessment of water column and sediment health at a broadscale level but has been expanded to include inshore reef, deep-reef and seagrass distribution and health. Seagrass monitoring occurs over transects. In this dataset, only the start location is displayed. Sediment sampling includes benthic infauna, stable isotopes, particle size, visual assessment, redox analysis, and sulphide measurements. Visual assessment, redox and sulphide analysis is carried out each year, while analysis of benthic infauna, stable isotopes and particle size is undertaken every four years. In the intervening years these samples are collected, preserved and retained. Water quality analytes include physico-chemical parameters (temperature, dissolved oxygen and salinity), nutrients (dissolved nutrients: ammonia, nitrate, phosphate, and silicate, nutrients: total nitrogen, total phosphorous), chlorophyll a and phytoplankton species counts. Water quality sampling is undertaken monthly from May to January and fortnightly from February to April.
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Estimates of the value of habitats can provide an objective basis for the prioritisation of conservation and restoration actions. Bivalve habitats, three-dimensional structures made of high-densities of bivales (most often oysters or mussels), their shells and other organisms, used to be a dominant habitat found in temperate and subtropical coastal waters. These habitats, provide a suite of ecosystem services such as habitat provision and food supply for many species, substrate stabilisation and shoreline protection, and water quaility improvements through their filter feeding. Bivalve habitat restoration is increasingly seen as an opportunity to return lost ecosystem services. In Australia, there is growing interest in bivalve habitat restoration, but there is a knowledge gap in regards to the services they provide. Here, we determined the habitat value of a historically dominant oyster species in Australia, Saccostrea glomerata. At remnant soft-sediment oyster reefs at four locations we estimated density, biomass, productivity and composition of mobile macroinvertebrate communities and compared these with adjacent ‘bare’ soft sediments, which typically replace ecologically extinct oyster reefs. The oyster reefs had a distinct assemblage of macroinvertebrates, with 30% higher densities, 5 times the biomass and almost 5 times the productivity of adjacent bare sediments. Infauna macroinvertebrate productivity was more than twice as high below oyster reefs, suggesting these reefs facilitate infaunal productivity. Crustaceans, an important food source for small fishes, were 13 times more productive on oyster reefs compared to adjacent bare sediments. These results demonstrate that oyster reefs provide an important habitat for macroinvertebrates and that restoration efforts are likely to provide significant returns in enhanced productivity.
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Locations of the Oysters Tasmania's Sensor Network. The sensor network provides real-time data on salinity, water temperature, and depth in shellfish growing areas in Tasmania. Oyster growers can access the sensor data via the ‘ShellPOINT’ portal (https://www.oysterstasmania.org/shellpoint.html).
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Phytoplankton was counted and identified from five sites over the 5-year period. Annual cycles in abundance are available (as cells mL-1), along with detailed species identification. Cell measurements and approximate geometric shape were also recorded for the calculation of biovolume (μL cell-1). Diatoms and dinoflagellates dominated the samples in terms of biomass, however, small cells were also very abundant throughout each year. The data are restricted to an integrated sample from the top 12 m of the water column. Fluorescence profiles elsewhere in this dataset can provide an indication of phytoplankton presence lower in the water column.
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Zooplankton was counted and identified from three sites over the 5-year period. The net used (200 m Bongo net) was designed to catch meso-zooplankton with an integrated vertical tow through the water column. One net from each of the paired Bongo samples was analysed and the data expressed as numbers per m3. Copepods dominated the zooplankton, with other groups such as salps, krill, appendicularians, cladocerans, chaetognaths and meroplanktonic larvae being seasonally dominant.
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Water samples for the analysis of pigments using High Performance Liquid Chromatography (HPLC) were collected only in the first 12 months of the sampling program. Pigment analysis is used to estimate algal community composition and concentration. Pigments which relate specifically to an algal class are termed marker or diagnostic pigments. Some of these diagnostic pigments are found exclusively in one algal class (e.g. prasinoxanthin in prasinophytes), while others are the principal pigments of one class, but are also found in other classes (e.g. fucoxanthin in diatoms and some haptophytes; 19′-butanoyloxyfucoxanthin in chrysophytes and some haptophytes). The presence or absence of these diagnostic pigments can provide a simple guide to the composition of a phytoplankton community, including identifying classes of small flagellates that cannot be determined by light microscopy techniques. There was general similarity in pigment composition between all sites, with a presence of diatoms (as indicated by fucoxanthin), haptophytes (hex-fucoxanthin), prasinophytes (prasinoxanthan), cryptophytes (alloxanthan), cyanophytes (zeaxanthan) and green algae (chl-b) in nearly all monthly samples at all sites. The green algae could be in the form of euglenophytes or prasinophytes; the absence of the pigment lutein in all samples indicates that chlorophytes are not present in Storm Bay, at least at the sites sampled.
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Comprehensive baseline environmental data for Storm Bay in south eastern Tasmania were required to inform the salmonid industry regarding site selection, to provide background environmental data before large-scale farming commences, and to support the development of a scientifically relevant and cost-effective environmental monitoring program. Storm Bay is a large deep bay that receives freshwater inflow from the River Derwent on its north-western boundary and exchanges water with Frederick Henry Bay on its north-eastern boundary. The eastern and western boundaries are defined by the Tasman Peninsula and Bruny Island, respectively, and the southern boundary connects with the Tasman Sea. This area is a mixing zone between the River Derwent outflow and oceanic waters. The oceanography in Storm Bay is complex and is characterized by considerable fluctuations in temperature, salinity and nutrients on variable temporal and spatial scales. This is due to the southerly extension of warm nutrient-depleted sub-tropical waters transported via the East Australian Current (EAC) down the east coast of Tasmania over summer, whilst the south and south-west coasts are influenced by cooler, nutrient-rich sub-Antarctic waters from the south and the Leeuwin Current from the north-west (Buchanan et al. 2014). The current project arose in response to the salmon aquaculture industry recognising the need for increased scientific knowledge to support ecologically sustainable development of Atlantic salmon (Salmo salar) farming operations in south-eastern Tasmania, particularly expansion into Storm Bay. The information provided will assist salmon companies to manage their operations in Storm Bay under varying environmental conditions. Our research has also provided the opportunity to investigate changes in water quality over a quarter of a century, as CSIRO investigated seasonal and inter-annual variability in chemical and biological parameters in Storm Bay during 1985-89. We sampled at the same “master station” in Storm Bay as CSIRO and used similar procedures where possible. Five sites were sampled monthly in Storm Bay for over five years from November 2009 to April 2015, except on rare occasions when weather conditions were unsuitable, and bimonthly at times in 2013 when external funding was not available. Site 1 was located at the mouth of the Derwent estuary and the entrance to Storm Bay, site 2 was in the same location as the ‘master site’ of a CSIRO study in 1985-88, site 3 was furthest offshore and provided the most information on oceanic currents influencing the bay, while sites 5 and 6 were requested by the salmon aquaculture industry as potential sites for expansion of salmon farming. Site 4 was further offshore and monitoring at this site was discontinued after three months because of insufficient time to collect samples from all sites in one day. An additional site, 9, at the entrance to Frederick Henry Bay was included from 18 July 2011 at the request of the Marine Farming Branch, Department of Primary Industries, Parks, Water and Environment (DPIPWE), to provide information on water quality coming from Frederick Henry Bay. Adjacent to, and largely unaffected by the River Derwent, Frederick Henry Bay is a large marine embayment with limited freshwater input from the Coal River at its northern boundary. ---------------------------------------------- See child records linked to this parent record for specific context and methodologies for each of the monitoring variables (phytoplankton, zooplankton, chlorophyll, pigment, nutrients, oceanography).
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Data was collected and processed for the project: "Assessment and communication of risks to Tasmanian aquaculture and fisheries from marine heatwaves". Observational data is from NOAA OISST v2.1 (1982-2020), and model data is from 25 CMIP6 models over the historical period (from 1982-2014), with SSP1-2.6 and SSP5-8.5 extensions (out to 2100). Raw sea surface temperature data truncated to the Tasmanian region: 138-155E, 49-35S. Time-series of subdomain area averages are also provided, along with calendar corrections, mean-bias corrections, and seasonal bias corrections for the model data. Further details are provided in Kajtar, J.B. and Holbrook, N.J. (2021): "Future projections of marine heatwave hazards to aquaculture and fisheries in Tasmania", Institute for Marine and Antarctic Studies, University of Tasmania, Australia. 36pp. ISBN: 978-1-922708-06-9. http://ecite.utas.edu.au/147866.
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Biologically relevant macronutrients, nitrate + nitrite, silicate, phosphate and ammonia, were measured at all sites throughout the study. Nitrate + nitrite values (NOx) at the surface showed clear seasonal trends, peaking over winter and drawing down to near zero in summer and autumn. Phosphate concentrations also reached a peak in winter, which was associated with Southern Ocean influence. Median ammonium concentrations at all sites were generally <0.5 μM, with no clear peaks in any season or month. Overall, the lowest values were measured in August and other months showed reasonable spread around the median. Median silicate concentrations were consistently highest at sites 1 and 9, followed by site 5. Water from the River Derwent flows through site 1, then tracks east towards site 9 then site 5. Seasonally, silicate was generally highest in winter when the River Derwent outflow is also greatest.