EARTH SCIENCE | OCEANS | OCEAN CHEMISTRY | PIGMENTS | CHLOROPHYLL
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These data were collected on Southern Surveyor transit voyage SS2013_T01 from Sydney to Hobart in February 2013. The voyage was a teaching voyage as part of KSA724. Masters students participated in the collection of standard oceanographic data, focusing on eddies of the East Australian Current. This dataset includes for reference the nutrient and hydrography bottle data as produced by the Marine National Facility, as well as the fluorometrically determined extracted chlorophyll concentration
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.
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).
Chlorophyll a concentration is widely used as a proxy to describe trends in phytoplankton biomass over spatial and temporal scales. The concentration of chlorophyll a in Storm Bay showed surprisingly little variation across the seasons. There was a gradient in concentration from site 1 to site 3, where chlorophyll a decreased slightly. It was highest and most variable at the inshore sites 1 and 9, and lowest at site 3, furthest out in the bay. There was no clear annually recurrent seasonal bloom, although data suggests higher values in spring and autumn (see later time series).