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Ian Hawes
University of Waikato, New Zealand

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Journal article
Published: 30 July 2021 in Journal of Marine Science and Engineering
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Upwelling and downwelling spectral (320–920 nm) distributions and photosynthetic active radiation (PAR) intensities were measured below a first-year land-fast sea ice in a western Greenland fjord with and without a snow cover. Time-series of surface upwelling PAR, downwelling PAR, and under-ice PAR were also obtained. Spectral distributions of upwelling and downwelling irradiances were similar except for reduced intensities in the UV, the red, and NIR parts of the spectrum when the ice was snow-covered. Upwelling PAR amounted to about 10% of downwelling intensities, giving 5.1 µmol photons m−2 s−1 at the bottom of the ice with a snow cover and 8.2 µmol photons m−2 s−1 without. PAR partitioning analyses showed that the upwelling was related to scattering by suspended particles in the water column. A snow melt increased under-ice daily maximum downwelling PAR from 50 to 180 µmol photons m−2 s−1 and overall under-ice PAR of 55 and 198 µmol photons m−2 s−1 with 10% upwelling. It is concluded that upwelling PAR below sea ice might be an important factor regarding sea ice algae photophysiology and performance with a 10% higher PAR; specifically when PAR >Ek the light saturation point of the sea ice algae.

ACS Style

Lars Lund-Hansen; Michael Bjerg-Nielsen; Tanja Stratmann; Ian Hawes; Brian Sorrell. Upwelling Irradiance below Sea Ice—PAR Intensities and Spectral Distributions. Journal of Marine Science and Engineering 2021, 9, 830 .

AMA Style

Lars Lund-Hansen, Michael Bjerg-Nielsen, Tanja Stratmann, Ian Hawes, Brian Sorrell. Upwelling Irradiance below Sea Ice—PAR Intensities and Spectral Distributions. Journal of Marine Science and Engineering. 2021; 9 (8):830.

Chicago/Turabian Style

Lars Lund-Hansen; Michael Bjerg-Nielsen; Tanja Stratmann; Ian Hawes; Brian Sorrell. 2021. "Upwelling Irradiance below Sea Ice—PAR Intensities and Spectral Distributions." Journal of Marine Science and Engineering 9, no. 8: 830.

Journal article
Published: 27 July 2021 in Journal of Marine Science and Engineering
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Snow cover on sea ice is the most important factor controlling light availability for sea ice algae, but it is predicted by climate models to become more variable and stochastic. Here, we document effects of a sudden, complete loss of the entire snow cover on first-year sea ice at Kangerlussuaq Fjord, West Greenland, due to a natural Föhn wind event that caused a ca. 17 °C air temperature increase over 36 h. We applied Imaging-PAM fluorometry to examine effects of snow cover on algal distribution and photobiology and observed a rapid decrease in algal biomass associated with loss of the skeletal ice crystal layer on the underside of the ice that had supported most of the visible algae. Furthermore, the remaining algae were photobiologically stressed, as seen in a significant decrease in the dark-acclimated fluorescence yield (ΦPSII_max) from 0.55 before snow loss to 0.41 after. However, recovery in the dark suggested that non-photosynthetic quenching was successfully dissipating excess energy in the community and that there was little photodamage. An observed decrease in the photosynthetic efficiency α from 0.22 to 0.16 µmol é m−2 s−1 is therefore likely to be due to photoacclimation and the change in community composition. Centric diatoms and flagellates were the main taxa lost in the snow loss event, whereas the sea ice specialist Nitzschia frigida increased in numbers. These observations are similar to those seen in artificial snow-clearing experiments and consistent with snow clearing being a useful approach for investigating the complex interactions between snow cover, irradiance fluctuations, and ice algal performance.

ACS Style

Brian Sorrell; Ian Hawes; Tanja Stratmann; Lars Lund-Hansen. Photobiological Effects on Ice Algae of a Rapid Whole-Fjord Loss of Snow Cover during Spring Growth in Kangerlussuaq, a West Greenland Fjord. Journal of Marine Science and Engineering 2021, 9, 814 .

AMA Style

Brian Sorrell, Ian Hawes, Tanja Stratmann, Lars Lund-Hansen. Photobiological Effects on Ice Algae of a Rapid Whole-Fjord Loss of Snow Cover during Spring Growth in Kangerlussuaq, a West Greenland Fjord. Journal of Marine Science and Engineering. 2021; 9 (8):814.

Chicago/Turabian Style

Brian Sorrell; Ian Hawes; Tanja Stratmann; Lars Lund-Hansen. 2021. "Photobiological Effects on Ice Algae of a Rapid Whole-Fjord Loss of Snow Cover during Spring Growth in Kangerlussuaq, a West Greenland Fjord." Journal of Marine Science and Engineering 9, no. 8: 814.

Journal article
Published: 31 May 2021 in ISPRS International Journal of Geo-Information
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Seagrass provides a wide range of essential ecosystem services, supports climate change mitigation, and contributes to blue carbon sequestration. This resource, however, is undergoing significant declines across the globe, and there is an urgent need to develop change detection techniques appropriate to the scale of loss and applicable to the complex coastal marine environment. Our work aimed to develop remote-sensing-based techniques for detection of changes between 1990 and 2019 in the area of seagrass meadows in Tauranga Harbour, New Zealand. Four state-of-the-art machine-learning models, Random Forest (RF), Support Vector Machine (SVM), Extreme Gradient Boost (XGB), and CatBoost (CB), were evaluated for classification of seagrass cover (presence/absence) in a Landsat 8 image from 2019, using near-concurrent Ground-Truth Points (GTPs). We then used the most accurate one of these models, CB, with historic Landsat imagery supported by classified aerial photographs for an estimation of change in cover over time. The CB model produced the highest accuracies (precision, recall, F1 scores of 0.94, 0.96, and 0.95 respectively). We were able to use Landsat imagery to document the trajectory and spatial distribution of an approximately 50% reduction in seagrass area from 2237 ha to 1184 ha between the years 1990–2019. Our illustration of change detection of seagrass in Tauranga Harbour suggests that machine-learning techniques, coupled with historic satellite imagery, offers potential for evaluation of historic as well as ongoing seagrass dynamics.

ACS Style

Nam-Thang Ha; Merilyn Manley-Harris; Tien-Dat Pham; Ian Hawes. Detecting Multi-Decadal Changes in Seagrass Cover in Tauranga Harbour, New Zealand, Using Landsat Imagery and Boosting Ensemble Classification Techniques. ISPRS International Journal of Geo-Information 2021, 10, 371 .

AMA Style

Nam-Thang Ha, Merilyn Manley-Harris, Tien-Dat Pham, Ian Hawes. Detecting Multi-Decadal Changes in Seagrass Cover in Tauranga Harbour, New Zealand, Using Landsat Imagery and Boosting Ensemble Classification Techniques. ISPRS International Journal of Geo-Information. 2021; 10 (6):371.

Chicago/Turabian Style

Nam-Thang Ha; Merilyn Manley-Harris; Tien-Dat Pham; Ian Hawes. 2021. "Detecting Multi-Decadal Changes in Seagrass Cover in Tauranga Harbour, New Zealand, Using Landsat Imagery and Boosting Ensemble Classification Techniques." ISPRS International Journal of Geo-Information 10, no. 6: 371.

Journal article
Published: 16 March 2021 in Genes
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Sulfide inhibits oxygenic photosynthesis by blocking electron transfer between H2O and the oxygen-evolving complex in the D1 protein of Photosystem II. The ability of cyanobacteria to counter this effect has implications for understanding the productivity of benthic microbial mats in sulfidic environments throughout Earth history. In Lake Fryxell, Antarctica, the benthic, filamentous cyanobacterium Phormidium pseudopriestleyi creates a 1–2 mm thick layer of 50 µmol L−1 O2 in otherwise sulfidic water, demonstrating that it sustains oxygenic photosynthesis in the presence of sulfide. A metagenome-assembled genome of P. pseudopriestleyi indicates a genetic capacity for oxygenic photosynthesis, including multiple copies of psbA (encoding the D1 protein of Photosystem II), and anoxygenic photosynthesis with a copy of sqr (encoding the sulfide quinone reductase protein that oxidizes sulfide). The genomic content of P. pseudopriestleyi is consistent with sulfide tolerance mechanisms including increasing psbA expression or directly oxidizing sulfide with sulfide quinone reductase. However, the ability of the organism to reduce Photosystem I via sulfide quinone reductase while Photosystem II is sulfide-inhibited, thereby performing anoxygenic photosynthesis in the presence of sulfide, has yet to be demonstrated.

ACS Style

Jessica Lumian; Anne Jungblut; Megan Dillion; Ian Hawes; Peter Doran; Tyler Mackey; Gregory Dick; Christen Grettenberger; Dawn Sumner. Metabolic Capacity of the Antarctic Cyanobacterium Phormidium pseudopriestleyi That Sustains Oxygenic Photosynthesis in the Presence of Hydrogen Sulfide. Genes 2021, 12, 426 .

AMA Style

Jessica Lumian, Anne Jungblut, Megan Dillion, Ian Hawes, Peter Doran, Tyler Mackey, Gregory Dick, Christen Grettenberger, Dawn Sumner. Metabolic Capacity of the Antarctic Cyanobacterium Phormidium pseudopriestleyi That Sustains Oxygenic Photosynthesis in the Presence of Hydrogen Sulfide. Genes. 2021; 12 (3):426.

Chicago/Turabian Style

Jessica Lumian; Anne Jungblut; Megan Dillion; Ian Hawes; Peter Doran; Tyler Mackey; Gregory Dick; Christen Grettenberger; Dawn Sumner. 2021. "Metabolic Capacity of the Antarctic Cyanobacterium Phormidium pseudopriestleyi That Sustains Oxygenic Photosynthesis in the Presence of Hydrogen Sulfide." Genes 12, no. 3: 426.

Article
Published: 09 February 2021 in Environmental Management
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The McMurdo Dry Valleys are the largest single ice-free area in Antarctica, and of considerable scientific and conservation value as an extreme polar desert. This is recognised through the McMurdo Dry Valleys Antarctic Specially Managed Area (ASMA), where management’s goals focus on protection of its unique features, while facilitating science access. Using a mix of remote sensing and existing cartography, we have identified over 6000 lakes and ponds in the ASMA. This study develops a classification of those aquatic ecosystems to provide a framework for management. It uses a limited top-down, hierarchical classification to define 13 class separations based on physical attributes that could largely be ascribed from existing databases or remotely sensed information. The first hierarchical level was based on landscape position, separating coastal kettle holes (reflecting recent glacial history), from other “topographic” water bodies. The second level was based on endorheic vs exorheic drainage, the third on mid-summer ice condition (no-ice cap; ice capped; frozen to base) and the fourth on source of inflow (glacial or non-glacial). Kettles were sub-classed by mid-summer ice only. Classes were tested against a set of field observations and an expert workshop validation process considered management implications for the ASMA. This study shows how the classification assists our understanding of Dry Valley landscapes and addresses management issues faced by researchers, environmental managers and policy makers. The approach to classification, rather than the detailed classes that may be specific to the Dry Valleys, has potential for wider use in other polar landscapes.

ACS Style

Ian Hawes; Clive Howard-Williams; Neil Gilbert; Kurt Joy. Towards an Environmental Classification of Lentic Aquatic Ecosystems in the McMurdo Dry Valleys, Antarctica. Environmental Management 2021, 67, 600 -622.

AMA Style

Ian Hawes, Clive Howard-Williams, Neil Gilbert, Kurt Joy. Towards an Environmental Classification of Lentic Aquatic Ecosystems in the McMurdo Dry Valleys, Antarctica. Environmental Management. 2021; 67 (4):600-622.

Chicago/Turabian Style

Ian Hawes; Clive Howard-Williams; Neil Gilbert; Kurt Joy. 2021. "Towards an Environmental Classification of Lentic Aquatic Ecosystems in the McMurdo Dry Valleys, Antarctica." Environmental Management 67, no. 4: 600-622.

Journal article
Published: 13 January 2021 in Marine Drugs
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Most marine biotoxins are produced by microalgae. The neurotoxin tetrodotoxin (TTX) has been reported in many seafood species worldwide but its source is unknown, making accumulation and depuration studies in shellfish difficult. Tetrodotoxin is a water-soluble toxin and cannot be directly ingested by shellfish. In the present study, a method was developed which involved binding TTX to solid particles of humic acid and encapsulating them in agar-gelatin capsules. A controlled quantity of TTX-containing microcapsules (size range 20–280 μm) was fed to Paphies australis, a bivalve known to accumulate TTX in the wild. The TTX-containing microcapsules were fed to P. australis every second day for 13 days. Ten P. australis (including five controls fed non-toxic microalgae) were harvested after 7 days and ten after 13 days. Paphies australis accumulated TTX, reaching concentrations of up to 103 µg kg−1 by day 13, exceeding the European Food Safety Authority recommended concentration of 44 μg kg−1 in shellfish. This novel method will allow future studies to explore the effects, accumulation and depuration rates of TTX in different animals and document how it is transferred through food webs.

ACS Style

Laura Biessy; Kirsty F. Smith; Susanna A. Wood; Annabel Tidy; Roel Van Ginkel; Joel R. D. Bowater; Ian Hawes. A Microencapsulation Method for Delivering Tetrodotoxin to Bivalves to Investigate Uptake and Accumulation. Marine Drugs 2021, 19, 33 .

AMA Style

Laura Biessy, Kirsty F. Smith, Susanna A. Wood, Annabel Tidy, Roel Van Ginkel, Joel R. D. Bowater, Ian Hawes. A Microencapsulation Method for Delivering Tetrodotoxin to Bivalves to Investigate Uptake and Accumulation. Marine Drugs. 2021; 19 (1):33.

Chicago/Turabian Style

Laura Biessy; Kirsty F. Smith; Susanna A. Wood; Annabel Tidy; Roel Van Ginkel; Joel R. D. Bowater; Ian Hawes. 2021. "A Microencapsulation Method for Delivering Tetrodotoxin to Bivalves to Investigate Uptake and Accumulation." Marine Drugs 19, no. 1: 33.

Journal article
Published: 21 August 2020 in Journal of Marine Science and Engineering
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Seagrass meadows are vulnerable to fine sediment (mud) pollution, with impacts usually attributed to reduction in submerged light. Here we tested two non-exclusive hypotheses, that mud particles (−3), porewater ammonium concentration (65 µM), and a more reduced redox profile (negative redox at only 2 cm soil depth) as well as a lower light availability when submerged compared to other habitats, while total daily light exposure differed little between habitats. This suggests that failure of seagrass to recolonize historical seagrass habitat reflects substrate muddiness and consequent unfavorable rhizosphere conditions. Our results provide evidence for the multi-stressor effects of fine sediment on seagrasses, with substrate suitability for seagrass being detrimentally affected even where light exposure seems sufficient.

ACS Style

Iñigo Zabarte-Maeztu; Fleur E. Matheson; Merilyn Manley-Harris; Robert J. Davies-Colley; Megan Oliver; Ian Hawes. Effects of Fine Sediment on Seagrass Meadows: A Case Study of Zostera muelleri in Pāuatahanui Inlet, New Zealand. Journal of Marine Science and Engineering 2020, 8, 645 .

AMA Style

Iñigo Zabarte-Maeztu, Fleur E. Matheson, Merilyn Manley-Harris, Robert J. Davies-Colley, Megan Oliver, Ian Hawes. Effects of Fine Sediment on Seagrass Meadows: A Case Study of Zostera muelleri in Pāuatahanui Inlet, New Zealand. Journal of Marine Science and Engineering. 2020; 8 (9):645.

Chicago/Turabian Style

Iñigo Zabarte-Maeztu; Fleur E. Matheson; Merilyn Manley-Harris; Robert J. Davies-Colley; Megan Oliver; Ian Hawes. 2020. "Effects of Fine Sediment on Seagrass Meadows: A Case Study of Zostera muelleri in Pāuatahanui Inlet, New Zealand." Journal of Marine Science and Engineering 8, no. 9: 645.

Preprint content
Published: 14 July 2020
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Freshwater ecosystems are considered hotspots of biodiversity in Antarctic polar deserts. Anticipated warming is expected to change the hydrology of these systems due to increased meltwater and reduction of ice cover, with implications for environmental conditions and physical connectivity between habitats. Using 16S rRNA sequencing, we evaluated the structure of microbial mat and planktonic communities within a connected watershed in the McMurdo Wright Valley, Antarctica to determine the roles of connectivity and habitat conditions in controlling microbial assemblage composition. We examined benthic and planktonic samples from glacial Lake Brownworth, the perennially ice-covered Lake Vanda, and the Onyx River, which connects the two. In Lake Vanda, we found distinct microbial assemblages occupying sub-habitats at different lake depths, while the communities from Lake Brownworth and Onyx River were structurally similar between them. Despite the higher connectivity between bacterial communities in the shallow parts of the system, environmental filtering dominated over dispersal in driving bacterial community structure. Functional metagenomics predictions identified genes related to degradation of halogenated aromatic compounds in surface microbial mats exposed to changes in water regimes, which progressively disappeared with increasing depth. Shifting environmental conditions due to increasing connectivity, rather than dispersal, may become the dominant drivers of bacterial diversity and functioning in Antarctic freshwater ecosystems.

ACS Style

Josep Ramoneda; Ian Hawes; Alberto Pascual-Garcia; Tyler J. Mackey; Dawn Y. Sumner; Anne D. Jungblut. Environmental controls and habitat connectivity of phototrophic microbial mats and bacterioplankton communities in an Antarctic freshwater system. 2020, 1 .

AMA Style

Josep Ramoneda, Ian Hawes, Alberto Pascual-Garcia, Tyler J. Mackey, Dawn Y. Sumner, Anne D. Jungblut. Environmental controls and habitat connectivity of phototrophic microbial mats and bacterioplankton communities in an Antarctic freshwater system. . 2020; ():1.

Chicago/Turabian Style

Josep Ramoneda; Ian Hawes; Alberto Pascual-Garcia; Tyler J. Mackey; Dawn Y. Sumner; Anne D. Jungblut. 2020. "Environmental controls and habitat connectivity of phototrophic microbial mats and bacterioplankton communities in an Antarctic freshwater system." , no. : 1.

Original paper
Published: 29 March 2020 in Polar Biology
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Rich in both microbial mat biomass and species diversity, the meltwater ponds of the McMurdo Ice Shelf (MIS) form important biodiversity and productivity elements in an otherwise barren landscape. These ponds are thought to be sensitive indicators of climate change-driven fluxes in pond water balance but our ability to predict such effects is confounded by our poor understanding of the inherent variability of these communities in response to the physico-chemical environment. Understanding how microbial communities are shaped across broad physico-chemical gradients may allow better predictions of the effects of climate change on the MIS wetlands. Our study found that distinct clustering of community types against environmental variables was apparent for both the diatom and cyanobacterial communities. For diatoms, conductivity was correlated with the separation of five significantly distinct communities. Significant differences in NH4–N concentrations were correlated to the three distinct cyanobacterial communities but many of the cyanobacteria morphotypes were recorded across a wide ecological range. More distinct community types suggested that diatoms were more sensitive to environmental change in these ponds than the cyanobacteria, despite the latter’s overall dominance. Distinct community clusters for diatoms, and to a lesser extent cyanobacteria, suggest that changes at a functional group level may be more important than at the level of individual species. Further understanding of diatom functional groups would provide us with the opportunity to hindcast past climates and water budgets within the Antarctic region. However, the disconnect between biomass and community composition currently prevents hindcasting past productivities in relation to environmental changes.

ACS Style

Donna L. Sutherland; Clive Howard-Williams; Peter Ralph; Ian Hawes. Environmental drivers that influence microalgal species in meltwater pools on the McMurdo Ice Shelf, Antarctica. Polar Biology 2020, 43, 467 -482.

AMA Style

Donna L. Sutherland, Clive Howard-Williams, Peter Ralph, Ian Hawes. Environmental drivers that influence microalgal species in meltwater pools on the McMurdo Ice Shelf, Antarctica. Polar Biology. 2020; 43 (5):467-482.

Chicago/Turabian Style

Donna L. Sutherland; Clive Howard-Williams; Peter Ralph; Ian Hawes. 2020. "Environmental drivers that influence microalgal species in meltwater pools on the McMurdo Ice Shelf, Antarctica." Polar Biology 43, no. 5: 467-482.

Journal article
Published: 21 January 2020 in Remote Sensing
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Seagrass has been acknowledged as a productive blue carbon ecosystem that is in significant decline across much of the world. A first step toward conservation is the mapping and monitoring of extant seagrass meadows. Several methods are currently in use, but mapping the resource from satellite images using machine learning is not widely applied, despite its successful use in various comparable applications. This research aimed to develop a novel approach for seagrass monitoring using state-of-the-art machine learning with data from Sentinel–2 imagery. We used Tauranga Harbor, New Zealand as a validation site for which extensive ground truth data are available to compare ensemble machine learning methods involving random forests (RF), rotation forests (RoF), and canonical correlation forests (CCF) with the more traditional maximum likelihood classifier (MLC) technique. Using a group of validation metrics including F1, precision, recall, accuracy, and the McNemar test, our results indicated that machine learning techniques outperformed the MLC with RoF as the best performer (F1 scores ranging from 0.75–0.91 for sparse and dense seagrass meadows, respectively). Our study is the first comparison of various ensemble-based methods for seagrass mapping of which we are aware, and promises to be an effective approach to enhance the accuracy of seagrass monitoring.

ACS Style

Nam Thang Ha; Merilyn Manley-Harris; Tien Dat Pham; Ian Hawes. A Comparative Assessment of Ensemble-Based Machine Learning and Maximum Likelihood Methods for Mapping Seagrass Using Sentinel-2 Imagery in Tauranga Harbor, New Zealand. Remote Sensing 2020, 12, 355 .

AMA Style

Nam Thang Ha, Merilyn Manley-Harris, Tien Dat Pham, Ian Hawes. A Comparative Assessment of Ensemble-Based Machine Learning and Maximum Likelihood Methods for Mapping Seagrass Using Sentinel-2 Imagery in Tauranga Harbor, New Zealand. Remote Sensing. 2020; 12 (3):355.

Chicago/Turabian Style

Nam Thang Ha; Merilyn Manley-Harris; Tien Dat Pham; Ian Hawes. 2020. "A Comparative Assessment of Ensemble-Based Machine Learning and Maximum Likelihood Methods for Mapping Seagrass Using Sentinel-2 Imagery in Tauranga Harbor, New Zealand." Remote Sensing 12, no. 3: 355.

Review
Published: 16 January 2020 in Water
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In this overview (introductory article to a special issue including 14 papers), we consider all main types of natural and artificial inland freshwater habitas (fwh). For each type, we identify the main biodiversity patterns and ecological features, human impacts on the system and environmental issues, and discuss ways to use this information to improve stewardship. Examples of selected key biodiversity/ecological features (habitat type): narrow endemics, sensitive (groundwater and GDEs); crenobionts, LIHRes (springs); unidirectional flow, nutrient spiraling (streams); naturally turbid, floodplains, large-bodied species (large rivers); depth-variation in benthic communities (lakes); endemism and diversity (ancient lakes); threatened, sensitive species (oxbow lakes, SWE); diverse, reduced littoral (reservoirs); cold-adapted species (Boreal and Arctic fwh); endemism, depauperate (Antarctic fwh); flood pulse, intermittent wetlands, biggest river basins (tropical fwh); variable hydrologic regime—periods of drying, flash floods (arid-climate fwh). Selected impacts: eutrophication and other pollution, hydrologic modifications, overexploitation, habitat destruction, invasive species, salinization. Climate change is a threat multiplier, and it is important to quantify resistance, resilience, and recovery to assess the strategic role of the different types of freshwater ecosystems and their value for biodiversity conservation. Effective conservation solutions are dependent on an understanding of connectivity between different freshwater ecosystems (including related terrestrial, coastal and marine systems).

ACS Style

Marco Cantonati; Sandra Poikane; Catherine M. Pringle; Lawrence E. Stevens; Eren Turak; Jani Heino; John S. Richardson; Rossano Bolpagni; Alex Borrini; Núria Cid; Martina Čtvrtlíková; Diana M. P. Galassi; Michal Hájek; Ian Hawes; Zlatko Levkov; Luigi Naselli-Flores; Abdullah A. Saber; Mattia Di Cicco; Barbara Fiasca; Paul B. Hamilton; Jan Kubečka; Stefano Segadelli; Petr Znachor. Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation. Water 2020, 12, 260 .

AMA Style

Marco Cantonati, Sandra Poikane, Catherine M. Pringle, Lawrence E. Stevens, Eren Turak, Jani Heino, John S. Richardson, Rossano Bolpagni, Alex Borrini, Núria Cid, Martina Čtvrtlíková, Diana M. P. Galassi, Michal Hájek, Ian Hawes, Zlatko Levkov, Luigi Naselli-Flores, Abdullah A. Saber, Mattia Di Cicco, Barbara Fiasca, Paul B. Hamilton, Jan Kubečka, Stefano Segadelli, Petr Znachor. Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation. Water. 2020; 12 (1):260.

Chicago/Turabian Style

Marco Cantonati; Sandra Poikane; Catherine M. Pringle; Lawrence E. Stevens; Eren Turak; Jani Heino; John S. Richardson; Rossano Bolpagni; Alex Borrini; Núria Cid; Martina Čtvrtlíková; Diana M. P. Galassi; Michal Hájek; Ian Hawes; Zlatko Levkov; Luigi Naselli-Flores; Abdullah A. Saber; Mattia Di Cicco; Barbara Fiasca; Paul B. Hamilton; Jan Kubečka; Stefano Segadelli; Petr Znachor. 2020. "Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation." Water 12, no. 1: 260.

Journal article
Published: 08 October 2019 in Remote Sensing
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Developments in the capabilities and affordability of unmanned aerial vehicles (UAVs) have led to an explosion in their use for a range of ecological and agricultural remote sensing applications. However, the ubiquity of visible light cameras aboard readily available UAVs may be limiting the application of these devices for fine-scale, high taxonomic resolution monitoring. Here we compare the use of RGB and multispectral cameras deployed aboard UAVs for assessing intertidal and shallow subtidal marine macroalgae to a high taxonomic resolution. Our results show that the diverse spectral profiles of marine macroalgae naturally lend themselves to remote sensing and habitat classification. Furthermore, we show that biodiversity assessments, particularly in shallow subtidal habitats, are enhanced using six-band discrete wavelength multispectral sensors (81% accuracy, Cohen’s Kappa) compared to three-band broad channel RGB sensors (79% accuracy, Cohen’s Kappa) for 10 habitat classes. Combining broad band RGB signals and narrow band multispectral sensing further improved the accuracy of classification with a combined accuracy of 90% (Cohen’s Kappa). Despite notable improvements in accuracy with multispectral imaging, RGB sensors were highly capable of broad habitat classification and rivaled multispectral sensors for classifying intertidal habitats. High spatial scale monitoring of turbid exposed rocky reefs presents a unique set of challenges, but the limitations of more traditional methods can be overcome by targeting ideal conditions with UAVs.

ACS Style

Leigh Tait; Jochen Bind; Hannah Charan-Dixon; Ian Hawes; John Pirker; David Schiel. Unmanned Aerial Vehicles (UAVs) for Monitoring Macroalgal Biodiversity: Comparison of RGB and Multispectral Imaging Sensors for Biodiversity Assessments. Remote Sensing 2019, 11, 2332 .

AMA Style

Leigh Tait, Jochen Bind, Hannah Charan-Dixon, Ian Hawes, John Pirker, David Schiel. Unmanned Aerial Vehicles (UAVs) for Monitoring Macroalgal Biodiversity: Comparison of RGB and Multispectral Imaging Sensors for Biodiversity Assessments. Remote Sensing. 2019; 11 (19):2332.

Chicago/Turabian Style

Leigh Tait; Jochen Bind; Hannah Charan-Dixon; Ian Hawes; John Pirker; David Schiel. 2019. "Unmanned Aerial Vehicles (UAVs) for Monitoring Macroalgal Biodiversity: Comparison of RGB and Multispectral Imaging Sensors for Biodiversity Assessments." Remote Sensing 11, no. 19: 2332.

Communication
Published: 24 July 2019 in Toxins
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Understanding of colony specific properties of cyanobacteria in the natural environment has been challenging because sampling methods disaggregate colonies and there are often delays before they can be isolated and preserved. Microcystis is a ubiquitous cyanobacteria that forms large colonies in situ and often produces microcystins, a potent hepatotoxin. In the present study a new cryo-sampling technique was used to collect intact Microcystis colonies in situ by embedding them in a sheet of ice. Thirty-two of these Microcystis colonies were investigated with image analysis, liquid chromatography-mass spectrometry, quantitative polymerase chain reaction and high-throughput sequencing to assess their volume, microcystin quota and internal transcribed spacer (ITS) genotype diversity. Microcystin quotas were positively correlated to colony volume (R2 = 0.32; p = 0.004). Individual colonies had low Microcystis ITS genotype diversity and one ITS operational taxonomic unit predominated in all samples. This study demonstrates the utility of the cryo-sampling method to enhance the understanding of colony-specific properties of cyanobacteria with higher precision than previously possible.

ACS Style

Jonathan Puddick; Eric O. Goodwin; Ian Hawes; David P. Hamilton; Susanna A. Wood. In Situ Collection and Preservation of Intact Microcystis Colonies to Assess Population Diversity and Microcystin Quotas. Toxins 2019, 11, 435 .

AMA Style

Jonathan Puddick, Eric O. Goodwin, Ian Hawes, David P. Hamilton, Susanna A. Wood. In Situ Collection and Preservation of Intact Microcystis Colonies to Assess Population Diversity and Microcystin Quotas. Toxins. 2019; 11 (8):435.

Chicago/Turabian Style

Jonathan Puddick; Eric O. Goodwin; Ian Hawes; David P. Hamilton; Susanna A. Wood. 2019. "In Situ Collection and Preservation of Intact Microcystis Colonies to Assess Population Diversity and Microcystin Quotas." Toxins 11, no. 8: 435.

Review article
Published: 19 July 2019 in Chemosphere
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Tetrodotoxin (TTX) is a potent neurotoxin responsible for countless human intoxications and deaths around the world. The distribution of TTX and its analogues is diverse and the toxin has been detected in organisms from both marine and terrestrial environments. Increasing detections seafood species, such as bivalves and gastropods, has drawn attention to the toxin, reinvigorating scientific interest and regulatory concerns. There have been reports of TTX in 21 species of bivalves and edible gastropods from ten countries since the 1980's. While TTX is structurally dissimilar to saxitoxin (STX), another neurotoxin detected in seafood, it has similar sodium channel blocking action and potency and both neurotoxins have been shown to have additive toxicities. The global regulatory level for the STX group toxins applied to shellfish is 800 μg/kg. The presence of TTX in shellfish is only regulated in one country; The Netherlands, with a regulatory level of 44 μg/kg. Due to the recent interest surrounding TTX in bivalves, the European Food Safety Authority established a panel to assess the risk and regulation of TTX in bivalves, and their final opinion was that a concentration below 44 μg of TTX per kg of shellfish would not result in adverse human effects. In this article, we review current knowledge on worldwide TTX levels in edible gastropods and bivalves over the last four decades, the different methods of detection used, and the current regulatory status. We suggest research needs that will assist with knowledge gaps and ultimately allow development of robust monitoring and management protocols.

ACS Style

Laura Biessy; Michael J. Boundy; Kirsty F. Smith; D. Tim Harwood; Ian Hawes; Susanna A. Wood. Tetrodotoxin in marine bivalves and edible gastropods: A mini-review. Chemosphere 2019, 236, 124404 .

AMA Style

Laura Biessy, Michael J. Boundy, Kirsty F. Smith, D. Tim Harwood, Ian Hawes, Susanna A. Wood. Tetrodotoxin in marine bivalves and edible gastropods: A mini-review. Chemosphere. 2019; 236 ():124404.

Chicago/Turabian Style

Laura Biessy; Michael J. Boundy; Kirsty F. Smith; D. Tim Harwood; Ian Hawes; Susanna A. Wood. 2019. "Tetrodotoxin in marine bivalves and edible gastropods: A mini-review." Chemosphere 236, no. : 124404.

Chapter
Published: 14 May 2019 in Advances in Environmental Microbiology
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Microbial mats growing under the permanent ice cover of Antarctic lakes occupy an exceptionally low-disturbance regime. Constant temperature, the absence of bioturbation or physical disturbance from wind action or ice formation allow mats to accumulate, as annual growth layers, over many decades or even centuries. In so doing they often assume decimetre scale, three-dimensional morphologies such as elaborate pinnacle structures and conical mounds. Here we combine existing and new information to describe microbial structures in three Antarctic lakes—simple prostrate mats in Lake Hoare, emergent cones in Lake Untersee and elaborate pinnacles in Lake Vanda. We attempt to determine whether structures emerge simply from uncoordinated organism-environment interactions or whether they represent an example of “emergent complexity”, within which some degree of self-organisation occurs to confer a holistic functional advantage to component organisms. While some holistic advantages were evident from the structures—the increase in surface area allows greater biomass and overall productivity and nutrient exchange with overlying water—the structures could also be understood in terms of potential interactions between individuals, their orientation and their environment. The data lack strong evidence of coordinated behaviour directed towards holistic advantages to the structure, though hints of coordinated behaviour are present as non-random distributions of structural elements. The great size of microbial structures in Antarctic lakes, and their relatively simple community composition, makes them excellent models for more focused research on microbial cooperation.

ACS Style

Ian Hawes; Dawn Sumner; Anne D. Jungblut. Complex Structure but Simple Function in Microbial Mats from Antarctic Lakes. Advances in Environmental Microbiology 2019, 91 -120.

AMA Style

Ian Hawes, Dawn Sumner, Anne D. Jungblut. Complex Structure but Simple Function in Microbial Mats from Antarctic Lakes. Advances in Environmental Microbiology. 2019; ():91-120.

Chicago/Turabian Style

Ian Hawes; Dawn Sumner; Anne D. Jungblut. 2019. "Complex Structure but Simple Function in Microbial Mats from Antarctic Lakes." Advances in Environmental Microbiology , no. : 91-120.

Journal article
Published: 02 May 2019 in Aquatic Botany
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Loss of a long-term stable submerged macrophyte community reverses shallow lakes from a clear into a turbid water state. Stuckenia pectinata densely colonised the marginal area of a shallow coastal lagoon Te Waihora (Lake Ellesmere) before its removal by the 1968 “Wahine” storm. This study aims to understand the current light availability for S. pectinata growth in Te Waihora with high turbidity and water level fluctuations. In a greenhouse experiment, acclimations in S. pectinata to lower light intensities involved elongation in stems and leaves, and an increase in photosynthetic efficiency per unit dry weight for both leaves and stems. However, these acclimations did not reduce the daily compensation irradiance (under which daily net photosynthesis equals zero) that was identified at 8.8 ± 0.9 μmol photons m−2 s-1. Subsequently, we estimated light compensation depth (LCD), based on the derived daily compensation irradiance, incident irradiance at the water surface, and light attenuation coefficients for the lake. In areas shallower than LCD, there is no light limitation for the growth of S. pectinata. The LCD ranged from 0.23 to 0.54 m and well explained the growth range of S. pectinata in Te Waihora during the 2016–2017 ecological survey. The estimated LCD also suggests low turbidity levels in early spring are critical for the growth of S. pectinata with the current water level fluctuation regimes. LCD is a useful parameter for understanding the growth of submerged macrophytes in shallow turbid lakes from the perspective of light availability.

ACS Style

Qian Hu; Matthew Turnbull; Ian Hawes. Estimated light compensation depth explains growth of Stuckenia pectinata in Te Waihora. Aquatic Botany 2019, 156, 57 -64.

AMA Style

Qian Hu, Matthew Turnbull, Ian Hawes. Estimated light compensation depth explains growth of Stuckenia pectinata in Te Waihora. Aquatic Botany. 2019; 156 ():57-64.

Chicago/Turabian Style

Qian Hu; Matthew Turnbull; Ian Hawes. 2019. "Estimated light compensation depth explains growth of Stuckenia pectinata in Te Waihora." Aquatic Botany 156, no. : 57-64.

Journal article
Published: 23 February 2019 in Toxicon: X
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Tetrodotoxin (TTX) is a potent neurotoxin responsible for many human intoxications globally. Despite its potency and widespread occurrence in taxonomically diverse species, the primary source of TTX remains uncertain. Paphies australis, an endemic clam found in New Zealand, has been found to contain TTX in several locations. However, it is unknown if this represents endogenous production or accumulation from an external source. To address this question, the concentrations of TTX in whole P. australis and dissected organs (siphons, foot, digestive gland and the ‘rest’) from thirteen sites around New Zealand were determined using liquid chromatography-tandem quadrupole mass spectrometry analysis (LC-MS/MS). Depuration rate of TTX was also investigated by harvesting and measuring concentrations in P. australis maintained in captivity on a toxin-free diet every three to 15 days for 150 days. The LC-MS/MS analyses of the spatial samples showed that TTX was present in P. australis from all regions tested, with significantly (p < 0.001) higher concentrations (15 – 50 μg kg-1) observed at lower latitudes of the North Island compared with trace levels (0.5 – 3 μg kg-1) in the South Island of New Zealand. Tetrodotoxin was detected in all the dissected organs but the siphons contained the highest concentrations of TTX at all sites analysed. A linear model of the depuration data identified a significant (p < 0.001) decline in total TTX concentrations in P. australis over the study period. The siphons maintained the highest amount of TTX across the entire depuration study. The digestive glands contained low concentrations at the start of the experiment, but this depurated rapidly and only traces remained after 21 days. These results provide evidence to suggest that P. australis does not produce TTX endogenously but obtains the neurotoxin from an exogenous source (e.g., diet) with the source more prevalent in warmer northern waters. The association of higher TTX concentrations in shellfish with warmer environments raises concerns that this toxin’s distribution and abundance could become an increasing human health issue with global warming.

ACS Style

Laura Biessy; Kirsty F. Smith; D. Tim Harwood; Michael J. Boundy; Ian Hawes; Susanna A. Wood; Tim Harwood. Spatial variability and depuration of tetrodotoxin in the bivalve Paphies australis from New Zealand. Toxicon: X 2019, 2, 100008 .

AMA Style

Laura Biessy, Kirsty F. Smith, D. Tim Harwood, Michael J. Boundy, Ian Hawes, Susanna A. Wood, Tim Harwood. Spatial variability and depuration of tetrodotoxin in the bivalve Paphies australis from New Zealand. Toxicon: X. 2019; 2 ():100008.

Chicago/Turabian Style

Laura Biessy; Kirsty F. Smith; D. Tim Harwood; Michael J. Boundy; Ian Hawes; Susanna A. Wood; Tim Harwood. 2019. "Spatial variability and depuration of tetrodotoxin in the bivalve Paphies australis from New Zealand." Toxicon: X 2, no. : 100008.

Journal article
Published: 01 September 2018 in Freshwater Science
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Proliferations of benthic cyanobacteria in the genus Phormidium are a global concern because of their increasing prevalence and ability to produce harmful toxins. Most studies have been observational and have linked physicochemical variables to Phormidium cover measured at the reach scale. Authors of these studies have alluded to nutrients and flow as key factors in accrual. Our goal was to use an experimental approach to examine how changes in velocity and NO3− concentrations influence Phormidium accrual. We hypothesized that: 1) Phormidium biomass accrual would be positively correlated with stream velocity; 2) biomass accrual would be positively related to NO3− concentration, which would have a stronger effect during early accrual; 3) an NO3− × velocity interaction would arise from saturation of accrual at high NO3− and high velocity; and 4) the probability of detachment would increase with decreasing velocity. We assessed mat expansion, biomass (as phycoerythrin and chlorophyll a [Chl a] concentrations, and biovolume), and algal assemblage composition in flow-through channel mesocosms for 16 d. We crossed 2 velocity treatments (0.1 and 0.2 m/s, slow and fast, respectively) with 3 NO3− treatments (0.02, 0.1, and 0.4 mg/L, ambient, medium, and high, respectively). Velocity was positively correlated with all measures of Phormidium biomass, but patch expansion rates increased at similar rates across all treatments. NO3− had no effect during early accrual, but phycoerythrin concentrations increased with increasing NO3− in fast-velocity treatments. At the end of the experiment, patch size was greater in the high-velocity treatments because of a greater number of partial or full patch detachments in slow-velocity treatments. These results suggest that NO3− concentrations do not affect Phormidium expansion and detachment, but may be important during colonization (not investigated), and that mat expansion occurs at a similar rate regardless of velocity, but termination of accrual cycles occurs earlier in slow velocities.

ACS Style

Tara G. McAllister; Susanna A. Wood; Michelle J. Greenwood; Felix Broghammer; Ian Hawes. The effects of velocity and nitrate on Phormidium accrual cycles: a stream mesocosm experiment. Freshwater Science 2018, 37, 496 -509.

AMA Style

Tara G. McAllister, Susanna A. Wood, Michelle J. Greenwood, Felix Broghammer, Ian Hawes. The effects of velocity and nitrate on Phormidium accrual cycles: a stream mesocosm experiment. Freshwater Science. 2018; 37 (3):496-509.

Chicago/Turabian Style

Tara G. McAllister; Susanna A. Wood; Michelle J. Greenwood; Felix Broghammer; Ian Hawes. 2018. "The effects of velocity and nitrate on Phormidium accrual cycles: a stream mesocosm experiment." Freshwater Science 37, no. 3: 496-509.

Original article
Published: 11 July 2018 in Sedimentology
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Perennially ice‐covered lakes can have significantly different facies than open‐water lakes because sediment is transported onto the ice, where it accumulates, and sand grains preferentially melt through to be deposited on the lake floor. To characterize the facies in these lakes, sedimentary deposits from five Antarctic perennially ice‐covered lakes were described using lake‐bottom observations, underwater video and images, and sediment cores. One lake was dominated by laminated microbial mats and mud (derived from an abutting glacier), with disseminated sand and rare gravel. The other four lakes were dominated by laminated microbial mats and moderately well to moderately sorted medium to very coarse sand with sparse granules and pebbles; they contained minor interstitial or laminated mud (derived from streams and abutting glaciers). The sand was disseminated or localized in mounds and 1 m to more than 10 m long elongate ridges. Mounds were centimetres to metres in diameter; conical, elongate or round in shape; and isolated or deposited near or on top of one another. Sand layers in the mounds had normal, inverse, or no grading. Nine mixed mud and sand facies were defined for perennially ice‐covered lakes based on the relative proportion of mud to sand and the style of sand deposition. While perennially ice‐covered lake facies overlap with other ice‐influenced lakes and glaciomarine facies, they are characterized by a paucity of grains coarser than granules, a narrow range in sand grain sizes, and inverse grading in the sand mounds. These facies can be used to infer changes in ice cover through time and to identify perennially ice‐covered lakes in the rock record. Ancient perennially ice‐covered lakes are expected on Earth and Mars, and their characterization will provide new insights into past climatic conditions and habitability.

ACS Style

Frances Rivera‐Hernandez; Dawn Y. Sumner; Tyler J. Mackey; Ian Hawes; Dale T. Andersen. In a PICL: The sedimentary deposits and facies of perennially ice‐covered lakes. Sedimentology 2018, 66, 917 -939.

AMA Style

Frances Rivera‐Hernandez, Dawn Y. Sumner, Tyler J. Mackey, Ian Hawes, Dale T. Andersen. In a PICL: The sedimentary deposits and facies of perennially ice‐covered lakes. Sedimentology. 2018; 66 (3):917-939.

Chicago/Turabian Style

Frances Rivera‐Hernandez; Dawn Y. Sumner; Tyler J. Mackey; Ian Hawes; Dale T. Andersen. 2018. "In a PICL: The sedimentary deposits and facies of perennially ice‐covered lakes." Sedimentology 66, no. 3: 917-939.

Journal article
Published: 06 July 2018 in Toxins
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Tetrodotoxin (TTX) is one of the most potent neurotoxins known. It was originally thought to only occur in puffer fish but has now been identified in twelve different classes of freshwater and marine organisms, including bivalves. Despite being one of the world’s most studied biotoxins, its origin remains uncertain. There is contradictory evidence regarding the source of TTX and its pathway through food webs. To date, the distribution of TTX has not been examined in bivalves. In the present study, 48 Paphies australis, a TTX-containing clam species endemic to New Zealand, were collected. Thirty clams were dissected, and organs and tissues pooled into five categories (siphons, digestive gland, adductor muscles, and the ‘rest’) and analyzed for TTX using liquid chromatography-mass spectrometry (LC-MS). The micro-distribution of TTX was visualized in the remaining 18 individuals using an immunohistological technique incorporating a TTX-specific monoclonal antibody. The LC-MS analysis revealed that siphons contained the highest concentrations of TTX (mean 403.8 µg/kg). Immunohistochemistry analysis showed TTX in the outer cells of the siphons, but also in the digestive system, foot, and gill tissue. Observing TTX in organs involved in feeding provides initial evidence to support the hypothesis of an exogenous source in P. australis.

ACS Style

Laura Biessy; Kirsty F. Smith; Michael J. Boundy; Stephen C. Webb; Ian Hawes; Susanna A. Wood. Distribution of Tetrodotoxin in the New Zealand Clam, Paphies australis, Established Using Immunohistochemistry and Liquid Chromatography-Tandem Quadrupole Mass Spectrometry. Toxins 2018, 10, 282 .

AMA Style

Laura Biessy, Kirsty F. Smith, Michael J. Boundy, Stephen C. Webb, Ian Hawes, Susanna A. Wood. Distribution of Tetrodotoxin in the New Zealand Clam, Paphies australis, Established Using Immunohistochemistry and Liquid Chromatography-Tandem Quadrupole Mass Spectrometry. Toxins. 2018; 10 (7):282.

Chicago/Turabian Style

Laura Biessy; Kirsty F. Smith; Michael J. Boundy; Stephen C. Webb; Ian Hawes; Susanna A. Wood. 2018. "Distribution of Tetrodotoxin in the New Zealand Clam, Paphies australis, Established Using Immunohistochemistry and Liquid Chromatography-Tandem Quadrupole Mass Spectrometry." Toxins 10, no. 7: 282.