title: Development of a Method for Trace Analysis of Dioctyl Sodium Sulfosuccinate by Liquid Chromatography Mass Spectrometry and its Application to Samples from the MV Rena Incident

authors: Bernstein, Daniel Richard

subjects: Liquid chromatography

abstract: The grounding of the MV Rena off the coast of Tauranga, New Zealand in 2011 prompted the application of Corexit® oil spill dispersants in an attempt to mitigate the impact of the spilled oil to coastal ecosystems. A quantitative method was developed employing sonication assisted extraction from beach sand followed by sample clean up by solid phase extraction and analysis by liquid chromatography tandem mass spectrometry for the analysis of Corexit® component dioctyl sodium sulfosuccinate (DOSS) at trace levels. The chromatographic method included the use of a C8 stationary phase with a gradient elution and quantitation by an internal standard approach based on mass spectrometer instrument response. Validation studies gave recoveries of 72 ± 1.7% with an accuracy of 94%. Calibration curves were shown to have a linear range of 0 – 200 μg.L⁻¹. Application of the method to the available environmental samples showed no presence of DOSS.
An attempt was made to apply the instrumental method to heavy fuel oil (HFO) tar-balls and oiled sand samples. Multiple extraction techniques were trialled including liquid-liquid extraction, sonication assisted extraction and anion exchange chromatography with recovery experiments for each method being carried out. Analysis of the extracts showed that quantitative recovery of DOSS had not been achieved for any of the methods investigated.
The difficulties associated with extracting DOSS from HFO tar-balls and oil sands suggest that the application of DOSS to surface oil slicks results in the preferential partitioning of DOSS into HFO. This has implications with respect to the distribution of DOSS in the environment following application, subsequent environmental monitoring and the degradation of HFO components by microbial communities.

text: Development of a Method for Trace Analysis of Dioctyl Sodium Sulfosuccinate by Liquid Chromatography Mass Spectrometry and its Application to Samples from the MV Rena Incident The grounding of the MV Rena off the coast of Tauranga, New Zealand in 2011 prompted the application of Corexit® oil spill dispersants in an attempt to mitigate the impact of the spilled oil to coastal ecosystems. A quantitative method was developed employing sonication assisted extraction from beach sand followed by sample clean up by solid phase extraction and analysis by liquid chromatography tandem mass spectrometry for the analysis of Corexit® component dioctyl sodium sulfosuccinate (DOSS) at trace levels. The chromatographic method included the use of a C8 stationary phase with a gradient elution and quantitation by an internal standard approach based on mass spectrometer instrument response. Validation studies gave recoveries of 72 ± 1.7% with an accuracy of 94%. Calibration curves were shown to have a linear range of 0 – 200 μg.L⁻¹. Application of the method to the available environmental samples showed no presence of DOSS.
An attempt was made to apply the instrumental method to heavy fuel oil (HFO) tar-balls and oiled sand samples. Multiple extraction techniques were trialled including liquid-liquid extraction, sonication assisted extraction and anion exchange chromatography with recovery experiments for each method being carried out. Analysis of the extracts showed that quantitative recovery of DOSS had not been achieved for any of the methods investigated.
The difficulties associated with extracting DOSS from HFO tar-balls and oil sands suggest that the application of DOSS to surface oil slicks results in the preferential partitioning of DOSS into HFO. This has implications with respect to the distribution of DOSS in the environment following application, subsequent environmental monitoring and the degradation of HFO components by microbial communities.

year: 2015

title: Landsat remote sensing of chlorophyll a concentrations in central North Island lakes of New Zealand

authors: Allan, Mathew Grant

subjects: Landsat Enhanced Thematic Mapper

abstract: We investigated the use of Landsat Enhanced Thematic Mapper (ETM) imagery to synoptically quantify chlorophyll a (chl a) concentrations. Two adjoining pairs of images of the central North Island were acquired on two different days in summer and spring 2002. 6sv atmospheric correction was compared to the cosine of the solar zenith angle correction (COST) dark object subtraction (DOS) atmospheric correction. The highest correlation between 6sv ln(Band 3) water surface reflectance and ln(chl a) was found in the 24 January 2002 image (r² = 0.954). 6sv atmospheric correction was preferable to COST-DOS as it gave more realistic reflectance values at a clear-water reference site and produced the highest correlation coefficient. The results from this investigation suggest that remote sensing provides a valuable tool to assess temporal and spatial distributions of chl a in unmonitored areas within lakes and that predictions may also be extended to unmonitored lakes within the domain of satellite image capture.

text: Landsat remote sensing of chlorophyll a concentrations in central North Island lakes of New Zealand We investigated the use of Landsat Enhanced Thematic Mapper (ETM) imagery to synoptically quantify chlorophyll a (chl a) concentrations. Two adjoining pairs of images of the central North Island were acquired on two different days in summer and spring 2002. 6sv atmospheric correction was compared to the cosine of the solar zenith angle correction (COST) dark object subtraction (DOS) atmospheric correction. The highest correlation between 6sv ln(Band 3) water surface reflectance and ln(chl a) was found in the 24 January 2002 image (r² = 0.954). 6sv atmospheric correction was preferable to COST-DOS as it gave more realistic reflectance values at a clear-water reference site and produced the highest correlation coefficient. The results from this investigation suggest that remote sensing provides a valuable tool to assess temporal and spatial distributions of chl a in unmonitored areas within lakes and that predictions may also be extended to unmonitored lakes within the domain of satellite image capture.

year: 2011

title: 2016 Subtidal Ecological Survey of Tauranga Harbour and development of benthic health models

authors: Clark, Dana

abstract: This report summarises the results of biological and physical data collected from a broad-scale subtidal survey of Tauranga Harbour conducted between March and May 2016. The survey was designed to understand more fully the role of various anthropogenic stressors on ecosystem health and feed into management of the harbour. Community-based models of ecosystem health called Benthic Health Models (BHMs) were developed to assess ecosystem health in response to mud and metal loading. This is the first comprehensive quantitative survey of Tauranga Harbour’s subtidal environment since 1990/91. 
The research was conducted as part of the Oranga Taiao Oranga Tangata (OTOT) programme. The wider research project aims to provide knowledge and toolsets to support co-management of estuaries. The three phases of this programme include 1) gathering Mātauranga Māori (a body of knowledge of Māori experience in the area) from local iwi/hapū, 2) consolidating the ecological knowledge of the Tauranga Harbour and providing modelling and indicators of estuarine ecosystem health, resilience and functioning, and 3) creating an Integrative Spatial Planning Tool (ISPT) that can help inform decision making in the harbour. The subtidal survey fits into the latter two research objectives, as the information collected will be used to develop indicators of ecosystem health, which will be used as components of the ISPT. 
Water, sediment and benthic macrofauna samples were collected from 45 subtidal sites across the harbour. Subtidal sediments were predominantly sandy with low levels of nutrients and metal loading. Upper reaches of channels tended to have higher mud, organic content and nutrient concentrations than sites closer to the main channels. Maximum subtidal sediment metal concentrations were well below guideline values and all metals, except lead, were less than median national values for intertidal estuarine sites. Highest metal concentrations were in the urbanised southern harbour or in areas of high mud deposition. 
Many of the numerically dominant macrofaunal taxa were present in both the 1990/91 and 2016 subtidal surveys, with pipi the most abundant bivalve in both surveys. Although the 2016 survey was not designed to quantitatively measure large bivalves, compared with the 1990/91 survey, fewer scallops and horse mussels were observed. The apparent decline in these species is concerning as large bivalves stabilise the sediment and provide complex physical structure to soft sediment habitats, providing predation refuges and settlement substrate for epifauna. The invasive Asian date mussel, on the other hand, has also become common in the harbour. 
Mud and metals were identified as key variables affecting the ecology of the harbour. To determine how environmental gradients in these variables affected ecosystem health, two Benthic Health Models (BHMs) were developed based on variability in community structure, one for each environmental gradient. The BHM approach is a useful management tool that can be used to determine the relative health of benthic communities at a single point in time, or track sites over time to assess whether communities are moving towards a more healthy or unhealthy state. It has been found to be more sensitive to changing ecosystem health than simple univariate community measures because it preserves more information about the community. 
Most sites were ranked in the lower BHM groups, suggesting Tauranga Harbour had fairly healthy subtidal communities with regard to mud and metal impacts. This was supported by values from other biotic indices, which indicated that all subtidal sites in Tauranga would be classified as having ‘good’ ecological status. Sites identified as most impacted by elevated mud and metals were generally located in the upper reaches of estuaries or near the urbanised southern portion of the harbour. In terms of mud, this to some extent reflects the natural progression of an estuary from land to sea; however, the rates of accumulation of sediments have been accelerated because of anthropogenic land-based activities. Although currents and mud were highly coupled in Tauranga’s subtidal environment, the Mud BHM could draw out community responses that were only associated with mud.

text: 2016 Subtidal Ecological Survey of Tauranga Harbour and development of benthic health models This report summarises the results of biological and physical data collected from a broad-scale subtidal survey of Tauranga Harbour conducted between March and May 2016. The survey was designed to understand more fully the role of various anthropogenic stressors on ecosystem health and feed into management of the harbour. Community-based models of ecosystem health called Benthic Health Models (BHMs) were developed to assess ecosystem health in response to mud and metal loading. This is the first comprehensive quantitative survey of Tauranga Harbour’s subtidal environment since 1990/91. 
The research was conducted as part of the Oranga Taiao Oranga Tangata (OTOT) programme. The wider research project aims to provide knowledge and toolsets to support co-management of estuaries. The three phases of this programme include 1) gathering Mātauranga Māori (a body of knowledge of Māori experience in the area) from local iwi/hapū, 2) consolidating the ecological knowledge of the Tauranga Harbour and providing modelling and indicators of estuarine ecosystem health, resilience and functioning, and 3) creating an Integrative Spatial Planning Tool (ISPT) that can help inform decision making in the harbour. The subtidal survey fits into the latter two research objectives, as the information collected will be used to develop indicators of ecosystem health, which will be used as components of the ISPT. 
Water, sediment and benthic macrofauna samples were collected from 45 subtidal sites across the harbour. Subtidal sediments were predominantly sandy with low levels of nutrients and metal loading. Upper reaches of channels tended to have higher mud, organic content and nutrient concentrations than sites closer to the main channels. Maximum subtidal sediment metal concentrations were well below guideline values and all metals, except lead, were less than median national values for intertidal estuarine sites. Highest metal concentrations were in the urbanised southern harbour or in areas of high mud deposition. 
Many of the numerically dominant macrofaunal taxa were present in both the 1990/91 and 2016 subtidal surveys, with pipi the most abundant bivalve in both surveys. Although the 2016 survey was not designed to quantitatively measure large bivalves, compared with the 1990/91 survey, fewer scallops and horse mussels were observed. The apparent decline in these species is concerning as large bivalves stabilise the sediment and provide complex physical structure to soft sediment habitats, providing predation refuges and settlement substrate for epifauna. The invasive Asian date mussel, on the other hand, has also become common in the harbour. 
Mud and metals were identified as key variables affecting the ecology of the harbour. To determine how environmental gradients in these variables affected ecosystem health, two Benthic Health Models (BHMs) were developed based on variability in community structure, one for each environmental gradient. The BHM approach is a useful management tool that can be used to determine the relative health of benthic communities at a single point in time, or track sites over time to assess whether communities are moving towards a more healthy or unhealthy state. It has been found to be more sensitive to changing ecosystem health than simple univariate community measures because it preserves more information about the community. 
Most sites were ranked in the lower BHM groups, suggesting Tauranga Harbour had fairly healthy subtidal communities with regard to mud and metal impacts. This was supported by values from other biotic indices, which indicated that all subtidal sites in Tauranga would be classified as having ‘good’ ecological status. Sites identified as most impacted by elevated mud and metals were generally located in the upper reaches of estuaries or near the urbanised southern portion of the harbour. In terms of mud, this to some extent reflects the natural progression of an estuary from land to sea; however, the rates of accumulation of sediments have been accelerated because of anthropogenic land-based activities. Although currents and mud were highly coupled in Tauranga’s subtidal environment, the Mud BHM could draw out community responses that were only associated with mud.

year: 2018