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Invasive species are widely recognised as one of the major threats to marine biodiversity worldwide. With increasingly faster and more frequent transoceanic shipping, propagule pressure in the marine environment is likely to further increase, leading to a need for effective strategies for the early detection, prevention and control of marine invasive species. However, such strategies are often difficult to implement as many marine species cannot be accurately categorised as either native or non-native. For these reasons molecular genetic methods have increasingly been utilised for the study of marine invasive species. The potential for molecular data to enhance traditional morphology-based information is recognised and there has been huge progress in the application of molecular genetic methods to the study of marine bioinvasions in th...
The relationship between heterocyte frequency, water temperature, nutrient concentrations and densities of Anabaena planktonica was examined in monomictic, eutrophic Lower Karori Reservoir (max. depth 21 m, area 0.034 km2), Wellington, New Zealand. Anabaena planktonica formed blooms and strongly dominated the phytoplankton assemblage during summer. The development of blooms of A. planktonica was associated with the set-up of stratification and increases in surface water temperature, with the peak of the bloom almost synchronous with maximum water temperature. The annual peak in heterocyte frequency preceded the bloom and occurred during a period of intensifying stratification. At this time, there were sustained low concentrations of dissolved inorganic nitrogen (DIN: nitrate-N + ammonium-N) and the lowest ratios of DIN to soluble react...
The detection of invasive species soon after an incursion, when the population is confined to a small area and at a low density, maximizes the probability of successful eradication. In response a number of sensitive molecular methods have been developed for identifying the larvae of marine invertebrate pests at extremely low concentrations. In this study we developed a highly sensitive real-time PCR assay targeting the 18S ribosomal DNA for the rapid and accurate identification of the Asian clam Corbula amurensis in environmental samples. Larvae of C. amurensis were spiked into commonly encountered sampling matrices including benthic assemblages, biofilms, sediment grabs and plankton net hauls, and the sensitivity of the assay was assessed. In this study the assay reliably detected one larva in up to 10 g of sediment, and five larvae i...
Considerable progress in our understanding of the population genetic changes associated with biological invasions has been made over the past decade. Using selectively neutral loci, it has been established that reductions in genetic diversity, reflecting founder effects, have occurred during the establishment of some invasive populations. However, some colonial organisms may actually gain an ecological advantage from reduced genetic diversity because of the associated reduction in inter-colony conflict. Here we report population genetic analyses, along with colony fusion experiments, for a highly invasive colonial ascidian, Didemnum vexillum. Analyses based on mitochondrial cytochrome oxidase I (COI) partial coding sequences revealed two distinct D. vexillum clades. One COI clade appears to be restricted to the probable native region (...
Mitochondrial cytochrome oxidase I (COI) gene sequencing (DNA barcoding) of Ciona specimens from New Zealand (NZ) led to the first record of the solitary ascidian Ciona savignyi in the Southern Hemisphere. We sought to quantify C. savignyi COI genetic diversity around the NZ archipelago and to compare this with diversity within C. savignyi's native range in the north-west Pacific. Ciona savignyi specimens were collected from two NZ sites and from three sites around Japan. COI sequences (595 bp) were amplified and measures of genetic diversity were calculated. Based on differences between their COI sequences we developed a PCR-based assay to distinguish C. savignyi from the morphologically similar C. intestinalis. A total of 12 C. savignyi COI haplotypes were recovered from the 76 samples. Of the four haplotypes observed in NZ, two were...
Most surveillance programmes for marine invasive species (MIS) require considerable taxonomic expertise, are laborious, and are unable to identify species at larval or juvenile stages. Therefore, marine pests may go undetected at the initial stages of incursions when population densities are low. In this study, we evaluated the ability of the benchtop GS Junior??? 454 pyrosequencing system to detect the presence of MIS in complex sample matrices. An initial in-silico evaluation of the mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear small subunit ribosomal DNA (SSU) genes, found that multiple primer sets (targeting a ca. 400 base pair region) would be required to obtain species level identification within the COI gene. In contrast a single universal primer set was designed to target the V1???V3 region of SSU, allowing...
A culture collection of freshwater planktonic and benthic cyanobacteria collected from sites across New Zealand has been established at the Cawthron Institute, Nelson, New Zealand. Limited resources led to uncertainty regarding the long-term maintenance of this collection. The present study demonstrates cryopreservation to be a viable method for long-term storage of cyanobacteria. Seventeen of 20 strains evaluated were successfully cryopreserved using the permeating cryopreservation agent dimethyl sulfoxide (Me2 SO), at a final concentration of 15% (v/v). Cyanotoxin analysis was undertaken on selected strains known to produce microcystins, nodularin, anatoxin-a, and saxitoxins. All strains retained their ability to produce these toxins following cryopreservation.
The assessment of biological samples is critical for measuring the health of New Zealand aquatic environments. Analysis of these samples commonly requires species identification and enumeration, which usually involves microscopy or microbiological methods. These techniques can be time-consuming, laborious, and are dependent on taxonomic expertise. Recent advances in molecular methods provide promising tools for assessing environmental samples. A range of molecular techniques are now used in New Zealand including: fluorescent in situ hybridisation; automated ribosomal intergenic spacer analysis; quantitative polymerase chain reaction; and, most recently, next-generation sequencing. The organisms (or targets) and environments monitored are equally diverse, ranging from cyanobacteria, rotifers and invasive fish in lakes, to macroinvertebr...
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