title: The Fate and Effects of Contaminants in Estuarine Environments

authors: Huteau, Julien

subjects: estuary

abstract: Estuaries are sensitive environments regarding their response to anthropogenic events. The accumulation of toxic trace elements, such as Cd and Pb, has detrimental consequences on benthic community composition and function that can lead to human health issues when seafood is consumed. Eutrophic water can generate blooms of macroalgae and can induce adverse changes in the structure of an entire food web. 
Environmental research is of fundamental importance to understand the sources, fates and effects of contaminants. It will permit the development of remediation strategies to improve sustainable practices. The approach taken in the research presented is focused on the measurement of trace elements in sediment, water and biota, and the application of stable isotopes in the detection of sources of contaminants. A novel set of data on New Zealand estuarine species, not usually screened for pollutants, has been assembled in the context of a number of estuarine systems that have been influenced by a range of anthropogenically generated contamination events. The combined use of diffuse gradient ‘in thin films’ (DGT) and the analysis of δ15N-NO3 and δ18O-NO3 in water, are new for New Zealand estuarine systems; the correlations generated will enhance baseline datasets for future environmental studies. This research additionally led to the development of a novel environmental indicator, “Ecohardness”, reflecting the estuarine chemical budget by the analysis of the material strength of cockle shell. 
From this research, lead, cadmium and zinc were found to be the most concerning polluting elements in the study location, with levels above sedimentary ANZECC safety guidelines. Phosphorus was found in high concentration in urban and rural estuaries heavily impacted by agricultural practices. Isotopic analysis confirmed sources of pollution with higher values of δ13C and δ15N near treated wastewater ponds. The accumulation of contaminants was also associated with river and stormwater inputs and the intensive use of fertilisers. The accumulation of trace elements was specifically associated with metal pathways rather than sedimentary composition. However, metal speciation is of fundamental importance in ecotoxicology and is regarded as more significant than bulk concentrations in water and sediment in the understanding of biological response of organisms to trace elements. Accumulation of trace elements in biota was found to be strongly associated to those that were captured in DGT devices deployed in the water (‘DGT-labile’ elements). DGT-labile elements can be defined as the “bioavailable” fraction, as this technique uses a hydrogel layer to control the diffuse transport of trace elements in solution, to a binding resin. All labile elements were found in higher concentration in the stream/estuarine environment than the ocean, demonstrating the characteristic of estuaries as a sink for trace elements. Further insight into the speciation of the various elements was permitted by calculating the rate of accumulation in different hydrogel thicknesses. Each element could be classified according to their behaviour ranking from putatively free simple inorganic cations with no resupply from complex ligands (e.g. Cd at Bureta), to fully sustained conditions with a constant degree of resupply of free ions and labile complexes (e.g. Ni, Fe and Cu at Bureta). 
The development of a novel environmental parameter “EcoHardness”, has application to examining pollutant response in estuarine bivalves. While microhardness has been measured previously in bivalves (cockle shell) and correlated to microstructure, this is the first time that microhardness for the same species was analysed in different estuaries that have different anthropogenic pollution attributes. The method demonstrated an increase of microhardness in response to a decrease of Ca content, that appeared to be inversely correlated to an increase of trace elements that were associated with the general chemical state of estuaries. Hence, harder shells were associated with more polluted estuarine areas. This parameter could be a valuable tool in the assessment of environmental changes linked to the increase of trace metal pollutants as observed around the world in the last few decades. 
This work has extended research into the environmental health of estuaries by combining a number of known analytical methodologies in a novel manner and through the development of a new technology. In addition, the work has examined a relevant trophic cascade of species further providing an insight into ecosystem functioning against a backdrop of human presence.

text: The Fate and Effects of Contaminants in Estuarine Environments Estuaries are sensitive environments regarding their response to anthropogenic events. The accumulation of toxic trace elements, such as Cd and Pb, has detrimental consequences on benthic community composition and function that can lead to human health issues when seafood is consumed. Eutrophic water can generate blooms of macroalgae and can induce adverse changes in the structure of an entire food web. 
Environmental research is of fundamental importance to understand the sources, fates and effects of contaminants. It will permit the development of remediation strategies to improve sustainable practices. The approach taken in the research presented is focused on the measurement of trace elements in sediment, water and biota, and the application of stable isotopes in the detection of sources of contaminants. A novel set of data on New Zealand estuarine species, not usually screened for pollutants, has been assembled in the context of a number of estuarine systems that have been influenced by a range of anthropogenically generated contamination events. The combined use of diffuse gradient ‘in thin films’ (DGT) and the analysis of δ15N-NO3 and δ18O-NO3 in water, are new for New Zealand estuarine systems; the correlations generated will enhance baseline datasets for future environmental studies. This research additionally led to the development of a novel environmental indicator, “Ecohardness”, reflecting the estuarine chemical budget by the analysis of the material strength of cockle shell. 
From this research, lead, cadmium and zinc were found to be the most concerning polluting elements in the study location, with levels above sedimentary ANZECC safety guidelines. Phosphorus was found in high concentration in urban and rural estuaries heavily impacted by agricultural practices. Isotopic analysis confirmed sources of pollution with higher values of δ13C and δ15N near treated wastewater ponds. The accumulation of contaminants was also associated with river and stormwater inputs and the intensive use of fertilisers. The accumulation of trace elements was specifically associated with metal pathways rather than sedimentary composition. However, metal speciation is of fundamental importance in ecotoxicology and is regarded as more significant than bulk concentrations in water and sediment in the understanding of biological response of organisms to trace elements. Accumulation of trace elements in biota was found to be strongly associated to those that were captured in DGT devices deployed in the water (‘DGT-labile’ elements). DGT-labile elements can be defined as the “bioavailable” fraction, as this technique uses a hydrogel layer to control the diffuse transport of trace elements in solution, to a binding resin. All labile elements were found in higher concentration in the stream/estuarine environment than the ocean, demonstrating the characteristic of estuaries as a sink for trace elements. Further insight into the speciation of the various elements was permitted by calculating the rate of accumulation in different hydrogel thicknesses. Each element could be classified according to their behaviour ranking from putatively free simple inorganic cations with no resupply from complex ligands (e.g. Cd at Bureta), to fully sustained conditions with a constant degree of resupply of free ions and labile complexes (e.g. Ni, Fe and Cu at Bureta). 
The development of a novel environmental parameter “EcoHardness”, has application to examining pollutant response in estuarine bivalves. While microhardness has been measured previously in bivalves (cockle shell) and correlated to microstructure, this is the first time that microhardness for the same species was analysed in different estuaries that have different anthropogenic pollution attributes. The method demonstrated an increase of microhardness in response to a decrease of Ca content, that appeared to be inversely correlated to an increase of trace elements that were associated with the general chemical state of estuaries. Hence, harder shells were associated with more polluted estuarine areas. This parameter could be a valuable tool in the assessment of environmental changes linked to the increase of trace metal pollutants as observed around the world in the last few decades. 
This work has extended research into the environmental health of estuaries by combining a number of known analytical methodologies in a novel manner and through the development of a new technology. In addition, the work has examined a relevant trophic cascade of species further providing an insight into ecosystem functioning against a backdrop of human presence.

year: 2017

title: Extent estimates and land cover relationships for functional indicators in non-wadeable rivers

authors: Collier, Kevin J.

subjects: metabolism

abstract: Functional indicators are being increasingly used to assess waterway health but their responses to pressure in non-wadeable rivers have not been widely documented or applied in modern survey designs that provide unbiased estimates of extent. This study tests the response of river metabolism and loss in cotton strip tensile strength across a land use pressure gradient in non-wadeable rivers of northern New Zealand, and reports extent estimates for river metabolism and decomposition rates. Following adjustment for probability of selection, ecosystem respiration (ER) and gross primary production (GPP) for the target population of order 5–7 non-wadeable rivers averaged −7.3 and 4.8 g O2 mˉ² dˉ¹, respectively, with average P/R < 1 indicating dominance by heterotrophic processes. Ecosystem respiration was <−3.3 g O2 mˉ² dˉ¹ for 75% of non-wadeable river length with around 20% of length between −10 and −20 g O2 mˉ² dˉ¹. Cumulative distribution functions of cotton strength loss estimates indicated a more-or-less linear relationship with river km reflecting an even spread of decay rates (range in k 0.0007–0.2875 dˉ¹) across non-wadeable rivers regionally. A non-linear relationship with land cover was detected for GPP which was typically <5 g O2 mˉ² dˉ¹ where natural vegetation cover was below 20% and greater than 80% of upstream catchment area. For cotton strength loss, the relationship with land cover was wedge-shaped such that sites with >60% natural cover had low decay rates (<0.02 dˉ¹) with variability below this increasing as natural cover declined. Using published criteria for assessing waterway health based on ER and GPP, 232–298 km (20–29%) of non-wadeable river length was considered to have severely impaired ecosystem functioning, and 436–530 km (42–50%) had no evidence of impact on river metabolism.

text: Extent estimates and land cover relationships for functional indicators in non-wadeable rivers Functional indicators are being increasingly used to assess waterway health but their responses to pressure in non-wadeable rivers have not been widely documented or applied in modern survey designs that provide unbiased estimates of extent. This study tests the response of river metabolism and loss in cotton strip tensile strength across a land use pressure gradient in non-wadeable rivers of northern New Zealand, and reports extent estimates for river metabolism and decomposition rates. Following adjustment for probability of selection, ecosystem respiration (ER) and gross primary production (GPP) for the target population of order 5–7 non-wadeable rivers averaged −7.3 and 4.8 g O2 mˉ² dˉ¹, respectively, with average P/R < 1 indicating dominance by heterotrophic processes. Ecosystem respiration was <−3.3 g O2 mˉ² dˉ¹ for 75% of non-wadeable river length with around 20% of length between −10 and −20 g O2 mˉ² dˉ¹. Cumulative distribution functions of cotton strength loss estimates indicated a more-or-less linear relationship with river km reflecting an even spread of decay rates (range in k 0.0007–0.2875 dˉ¹) across non-wadeable rivers regionally. A non-linear relationship with land cover was detected for GPP which was typically <5 g O2 mˉ² dˉ¹ where natural vegetation cover was below 20% and greater than 80% of upstream catchment area. For cotton strength loss, the relationship with land cover was wedge-shaped such that sites with >60% natural cover had low decay rates (<0.02 dˉ¹) with variability below this increasing as natural cover declined. Using published criteria for assessing waterway health based on ER and GPP, 232–298 km (20–29%) of non-wadeable river length was considered to have severely impaired ecosystem functioning, and 436–530 km (42–50%) had no evidence of impact on river metabolism.

year: 2013

title: How is the circular economy emerging in Aotearoa New Zealand? Research Brief

authors: Diprose, G

abstract: The results of the environmental scan show that there is grass-roots activity and that we have some high level conceptualisations of circular economies (CE) however there is little in-between. As such, it is in the middle that activity needs to occur to transition towards a circular economy. We see a need to move beyond business-as-usual with an entity focus to an ‘ecosystem phase.’ This means that for CE, partnerships are needed across business, organisations, Treaty partners, institutions, NGOs and stakeholders to form collaborations around material and people flows in order for ecosystems to form and create circular economies.

text: How is the circular economy emerging in Aotearoa New Zealand? Research Brief The results of the environmental scan show that there is grass-roots activity and that we have some high level conceptualisations of circular economies (CE) however there is little in-between. As such, it is in the middle that activity needs to occur to transition towards a circular economy. We see a need to move beyond business-as-usual with an entity focus to an ‘ecosystem phase.’ This means that for CE, partnerships are needed across business, organisations, Treaty partners, institutions, NGOs and stakeholders to form collaborations around material and people flows in order for ecosystems to form and create circular economies.

year: 2022