title: How low can they go: A comparison between dog (Canis familiaris) and environmental DNA detection of invasive koi carp (Cyprinus rubrofuscus)

authors: Collins, Melissa Anne

subjects: scent detection dogs

abstract: Carp (Cyprinus sp.) are a highly invasive fish that pose a significant threat to freshwater ecosystems worldwide. At high biomasses (i.e., ≥100 kg/ha), the benthic feeding behaviour of carp can have deleterious ecosystem effects, often changing clear, macrophyte dominant waterbodies to turbid-phytoplankton dominant ecosystems. To prevent carp from reaching ecologically harmful biomasses, early detection (i.e., before population establishment) and rapid control actions are vital. Boat electrofishing, netting, and environmental DNA (eDNA) are commonly used to survey for carp, but these methods can be expensive or time inefficient when fish densities are low. Scent-detection dogs have proven efficacious at detecting terrestrial and aquatic species and could represent an efficient method for early detection of carp invasions. Here, we investigated a dog’s sensitivity and specificity to carp scent using a multiple probe design experiment. The dog was trained to use an automated carousel independently of its handler and assessed water samples from aquaria containing either no fish scent (n = 3, nontarget), goldfish (Carassius auratus) scent (n = 5, non-target) or carp scent (n = 9, target). The goldfish samples and six of the target samples were presented to the dog at a standard fish biomass concentration of 15.5 mg/L. The remaining three target samples (probes) were systematically diluted to determine the dog’s detection threshold. Results showed that the dog could detect carp housed under laboratory conditions down to a dilution equivalent biomass of 9.3 kg/ha (i.e., 0.5 mg carp/L), which is well below the likely biomass threshold of carp known to cause significant ecological impacts. The dog’s scent-detection performance was then compared with eDNA, an existing survey method. Quantitative PCR conducted on DNA extracted from laboratory aquaria filtrate revealed that the species-specific primer could detect carp at 9.3 kg/ha, but amplification rates at this dilution were low, as were all dilutions below the limit of quantification (≈160 kg/ha). These findings suggest that dogs could provide an accurate and highly sensitive method invasive fish detection. However, before deployment as a carp surveillance method, dogs’ performance on water samples collected from natural aquatic systems (i.e., lakes, ponds, rivers) needs to be evaluated. To our knowledge this is the first published study of its kind comparing a dog’s sensitivity to eDNA, and investigating the potential utility of dogs as an invasive fish detection method.

text: How low can they go: A comparison between dog (Canis familiaris) and environmental DNA detection of invasive koi carp (Cyprinus rubrofuscus) Carp (Cyprinus sp.) are a highly invasive fish that pose a significant threat to freshwater ecosystems worldwide. At high biomasses (i.e., ≥100 kg/ha), the benthic feeding behaviour of carp can have deleterious ecosystem effects, often changing clear, macrophyte dominant waterbodies to turbid-phytoplankton dominant ecosystems. To prevent carp from reaching ecologically harmful biomasses, early detection (i.e., before population establishment) and rapid control actions are vital. Boat electrofishing, netting, and environmental DNA (eDNA) are commonly used to survey for carp, but these methods can be expensive or time inefficient when fish densities are low. Scent-detection dogs have proven efficacious at detecting terrestrial and aquatic species and could represent an efficient method for early detection of carp invasions. Here, we investigated a dog’s sensitivity and specificity to carp scent using a multiple probe design experiment. The dog was trained to use an automated carousel independently of its handler and assessed water samples from aquaria containing either no fish scent (n = 3, nontarget), goldfish (Carassius auratus) scent (n = 5, non-target) or carp scent (n = 9, target). The goldfish samples and six of the target samples were presented to the dog at a standard fish biomass concentration of 15.5 mg/L. The remaining three target samples (probes) were systematically diluted to determine the dog’s detection threshold. Results showed that the dog could detect carp housed under laboratory conditions down to a dilution equivalent biomass of 9.3 kg/ha (i.e., 0.5 mg carp/L), which is well below the likely biomass threshold of carp known to cause significant ecological impacts. The dog’s scent-detection performance was then compared with eDNA, an existing survey method. Quantitative PCR conducted on DNA extracted from laboratory aquaria filtrate revealed that the species-specific primer could detect carp at 9.3 kg/ha, but amplification rates at this dilution were low, as were all dilutions below the limit of quantification (≈160 kg/ha). These findings suggest that dogs could provide an accurate and highly sensitive method invasive fish detection. However, before deployment as a carp surveillance method, dogs’ performance on water samples collected from natural aquatic systems (i.e., lakes, ponds, rivers) needs to be evaluated. To our knowledge this is the first published study of its kind comparing a dog’s sensitivity to eDNA, and investigating the potential utility of dogs as an invasive fish detection method.

year: 2022

title: Symmetry operators and separation of variables for spin-wave equations in oblate spheroidal coordinates

authors: Kalnins, Ernie G.

subjects: Mathematics

abstract: A family of second-order differential operators that characterize the solution of the massless spin s field equations, obtained via separation of variables in oblate spheroidal coordinates and using a null tetrad is found. The first two members of the family also characterize the separable solutions in the Kerr space-time. It is also shown that these operators are symmetry operators of the field equations in empty space-times whenever the space-time admits a second-order Killing–Yano tensor.

text: Symmetry operators and separation of variables for spin-wave equations in oblate spheroidal coordinates A family of second-order differential operators that characterize the solution of the massless spin s field equations, obtained via separation of variables in oblate spheroidal coordinates and using a null tetrad is found. The first two members of the family also characterize the separable solutions in the Kerr space-time. It is also shown that these operators are symmetry operators of the field equations in empty space-times whenever the space-time admits a second-order Killing–Yano tensor.

year: 1990-07

title: Microplastics in the marine environment: Sediment contaminant and bioaccumulation rates in bivalves within the Bay of Plenty

authors: Lewis, Anita

subjects: Microplastic

abstract: Microplastic pollution is recognised as a significant anthropogenic issue in coastal ecosystems around the world. The accumulation of microplastics in coastal environments causes both direct and indirect effects on these already vulnerable ecosystems. Limited information was available of the scale of microplastic pollution across New Zealand, including the Bay of Plenty. To enable a greater understanding of microplastic accumulation in sediment and bioaccumulation in bivalves sampling  within the Bay of Plenty area was conducted.
The presence of  microplastic particles was investigated from sediment and shellfish samples collected across the Bay of Plenty, from Waihī Beach in the West, to Ōpōtiki in the East. Three species of shellfish were collected that differed in their functional feeding modes (filter feeder vs deposit feeder): tuangi (cockle: Austrovenus stuchburyi), hanikura (wedge shell: Macomona liliana), and tuatua (surf clam: Paphies subtriangulata). Microplastic particles from sediment and bivalves were separated from the sediment and shellfish samples in the laboratory and identified using visual light stereomicroscopy. Microplastic particles were identified and quantified into three categories: fragments, fibres, and films. 
Significant numbers of fibres, as well as some fragments and films were found to be present in the sediment throughout all sampling locations. The highest density of microplastic particles in sediment (up to 11,087.9 per m²) were observed at sites that were closed to municipal sewage outfalls and populated areas, and the lowest densities were observed at Matakana Island (63 particles per m²). Sites in Ōhiwa Harbour showed an average of 504.6 particles per m² at the high tide zone and 477.6 particles per m² at the intertidal zone in the sediment. Ohiwa Harbour showed similar levels of microplastic accumulation in sediment compared to Tauranga Harbour. However, higher levels of microplastic particles were found in the sediment at open coast sites.
All shellfish sampled had at least one microplastic particle found in their tissues. The highest number of microplastics in shellfish were found in the wedge shell (23 particles), with the least from the cockles (1). Statistical analysis reveal that the deep burrowing deposit feeder (Macomona liliana) demonstrated an elevated amount of microplastic particles ingested relative to the shallow burrowing suspension feeding cockle (Austrovenus stutchburyi). A notable amount of microplastic particles were also found at all sampling locations for the culturally important tuatua (Paphies subtriangulata). However, comparing all three bivalve species, the deposit feeding M. liliana, ingested higher amounts than both the A. stutchburyi and P. subtriangulata, which could be related to their different functional feeding modes in the marine environment. This research provides baseline information to assess the extent of microplastic pollution in sediments and the potential for bioaccumulation in bivalve species with differentiated feeding modes and functional roles in the marine environment. 
The problem with microplastics is a global emerging contaminant. Preventing the problem of plastic wastes in New Zealand will require change across all aspects of society, along with policy regulations to mitigate the issue of microplastic pollution.

text: Microplastics in the marine environment: Sediment contaminant and bioaccumulation rates in bivalves within the Bay of Plenty Microplastic pollution is recognised as a significant anthropogenic issue in coastal ecosystems around the world. The accumulation of microplastics in coastal environments causes both direct and indirect effects on these already vulnerable ecosystems. Limited information was available of the scale of microplastic pollution across New Zealand, including the Bay of Plenty. To enable a greater understanding of microplastic accumulation in sediment and bioaccumulation in bivalves sampling  within the Bay of Plenty area was conducted.
The presence of  microplastic particles was investigated from sediment and shellfish samples collected across the Bay of Plenty, from Waihī Beach in the West, to Ōpōtiki in the East. Three species of shellfish were collected that differed in their functional feeding modes (filter feeder vs deposit feeder): tuangi (cockle: Austrovenus stuchburyi), hanikura (wedge shell: Macomona liliana), and tuatua (surf clam: Paphies subtriangulata). Microplastic particles from sediment and bivalves were separated from the sediment and shellfish samples in the laboratory and identified using visual light stereomicroscopy. Microplastic particles were identified and quantified into three categories: fragments, fibres, and films. 
Significant numbers of fibres, as well as some fragments and films were found to be present in the sediment throughout all sampling locations. The highest density of microplastic particles in sediment (up to 11,087.9 per m²) were observed at sites that were closed to municipal sewage outfalls and populated areas, and the lowest densities were observed at Matakana Island (63 particles per m²). Sites in Ōhiwa Harbour showed an average of 504.6 particles per m² at the high tide zone and 477.6 particles per m² at the intertidal zone in the sediment. Ohiwa Harbour showed similar levels of microplastic accumulation in sediment compared to Tauranga Harbour. However, higher levels of microplastic particles were found in the sediment at open coast sites.
All shellfish sampled had at least one microplastic particle found in their tissues. The highest number of microplastics in shellfish were found in the wedge shell (23 particles), with the least from the cockles (1). Statistical analysis reveal that the deep burrowing deposit feeder (Macomona liliana) demonstrated an elevated amount of microplastic particles ingested relative to the shallow burrowing suspension feeding cockle (Austrovenus stutchburyi). A notable amount of microplastic particles were also found at all sampling locations for the culturally important tuatua (Paphies subtriangulata). However, comparing all three bivalve species, the deposit feeding M. liliana, ingested higher amounts than both the A. stutchburyi and P. subtriangulata, which could be related to their different functional feeding modes in the marine environment. This research provides baseline information to assess the extent of microplastic pollution in sediments and the potential for bioaccumulation in bivalve species with differentiated feeding modes and functional roles in the marine environment. 
The problem with microplastics is a global emerging contaminant. Preventing the problem of plastic wastes in New Zealand will require change across all aspects of society, along with policy regulations to mitigate the issue of microplastic pollution.

year: 2021