Abstract
Toxic phytoplankton have been detrimental to the fishing and aquaculture industry on the east coast of Tasmania, causing millions of dollars in loss due to contaminated seafood. In 2012–2017, shellfish stocks were poisoned by Alexandrium catenella, a dinoflagellate species that produces paralytic shellfish toxins (PST). Remote sensing data may provide an environmental context for the drivers of PST events in Tasmania. We conducted spatial and temporal trend analyses of the Multi-Scale Ultra-High-Resolution Sea Surface Temperature (MUR SST) and Ocean Color Climate Change Initiative chlorophyll-a (OC-CCI chl-a) to determine if SST and chl-a correlated with the major toxin increases from 2012 to 2017. Along with the trends, we compare the remotely sensed oceanographic parameters of SST and chl-a to toxin events off the east coast of Tasmania to provide environmental context for the high-toxin period. Spatial and temporal changes for chl-a differ based on the north, central, and southeast coast of Tasmania. For sites in the north, chl-a was 5.3% higher from the pre-PST period relative to the PST period, 5.1% along the central part of the coast, and by 6.0% in the south based on deviations from the coastal study area time series. Overall, SST has slightly decreased from 2007 to 2020 (tau = −0.011, p = 0.827) and chl-a has significantly decreased for the east coast (tau = −0.164, p = 1.58 × 10−3). A negative relationship of SST and PST values occurred in the north (r = −0.530, p = 5.32 × 10−5) and central sites (r = −0.225, p = 0.157). The correlation between satellite chl-a (from OC-CCI, Visible Infrared Imaging Radiometer Suite (VIIRS), and Moderate-Resolution Imaging Spectrometer (MODIS) Aqua) and in situ data is weak, which makes it difficult to assess relationships present between chl-a and toxin concentrations. Moving forward, the development of a regional chl-a algorithm and increased in situ chl-a collection and plankton sampling at a species level will help to improve chl-a measurements and toxic phytoplankton production monitoring around Tasmania.
Highlights
From 2012 to 2017, the east coast of Tasmania saw enhanced production of paralytic shellfish toxins (PST) from the dinoflagellate Alexandrium catenella, a common harmful algal bloom (HAB) species, causing over AUD $23 million in losses for the shellfish industry [1,2,3].Aquaculture is a major industry in Tasmania and high toxin production forced most of the marine farms on the east coast to shut down after the poisoning of mussel, oyster, and rock lobster stocks [1]
Xie et al.’s study emphasized low temperatures and high chl-a in relation to PST values for the east coast study area, which matched with our high chl-a in relation to PST values for the east coast study area, which matched with our temperature analysis and the Spring Bay chl-a [4]
Our study sought to establish the environmental context for PST events in eastern coastal Tasmania using remote sensing
Summary
From 2012 to 2017, the east coast of Tasmania saw enhanced production of paralytic shellfish toxins (PST) from the dinoflagellate Alexandrium catenella, a common harmful algal bloom (HAB) species, causing over AUD $23 million in losses for the shellfish industry [1,2,3].Aquaculture is a major industry in Tasmania and high toxin production forced most of the marine farms on the east coast to shut down after the poisoning of mussel, oyster, and rock lobster stocks [1]. From 2012 to 2017, the east coast of Tasmania saw enhanced production of paralytic shellfish toxins (PST) from the dinoflagellate Alexandrium catenella, a common harmful algal bloom (HAB) species, causing over AUD $23 million in losses for the shellfish industry [1,2,3]. The stratification can be caused by an influx of low-nutrient waters from the East Australian Current (EAC), runoff from high rainfall, or low wind conditions during upwelling relaxation [2,4,5]. One hypothesis for these blooms is that low-nutrient conditions afford dinoflagellate species an advantage over diatoms
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