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Dive into the research topics where Judith M. O'Neil is active.

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Featured researches published by Judith M. O'Neil.


Marine Pollution Bulletin | 2008

Ocean urea fertilization for carbon credits poses high ecological risks

Patricia M. Glibert; Rhodora V. Azanza; Michele Astrid Burford; Ken Furuya; E Abal; Adnan Al-Azri; Faiza Al-Yamani; P. Andersen; Donald M. Anderson; J Beardall; Gry Mine Berg; Larry E. Brand; Deborah A. Bronk; Justin D. Brookes; JoAnn M. Burkholder; A Cembella; William P. Cochlan; Jackie L. Collier; Yves Collos; Robert J. Diaz; Martina A. Doblin; T Drennen; Sonya T. Dyhrman; Yasuwo Fukuyo; Miles Furnas; James N. Galloway; Edna Granéli; Dv Ha; Gustaaf M. Hallegraeff; John A. Harrison

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.


Estuaries and Coasts | 2006

Nitrogen, phosphorus, silica, and carbon in Moreton Bay, Queensland, Australia: Differential limitation of phytoplankton biomass and production

Patricia M. Glibert; Cynthia A. Heil; Judith M. O'Neil; William C. Dennison; Mark J. O'donohue

Subtropical estuaries have received comparatively little attention in the study of nutrient loading and subsequent nutrient processing relative to temperate estuaries. Australian estuaries are particularly susceptible to increased nutrient loading and eutrophication, as 75% of the population resides within 200 km of the coastline. We assessed the factors potentially limiting both biomass and production in one Australian estuary, Moreton Bay, through stoichiometric comparisons of nitrogen (N), phosphorus (P), silicon (Si), and carbon (C) concentrations, particulate compositions, and rates of uptake. Samples were collected over 3 seasons in 1997–1998 at stations located throughout the bay system, including one riverine endmember site. Concentrations of all dissolved nutrients, as well as particulate nutrients and chlorophyll, declined 10-fold to 100-fold from the impacted western embayments to the eastern, more oceanic-influenced regions of the bay during all seasons. For all seasons and all regions, both the dissolved nutrients and particulate biomass yielded N:P ratios <6 and N:Si ratios <1. Both relationships suggest strong limitation of biomass by N throughout the bay. Limitation of rates of nutrient uptake and productivity were more complex. Low C:N and C:P uptake ratios at the riverine site suggested light limitation at all seasons, low N:P ratios suggested some degree of N limitation and high N:Si uptake ratios in austral winter suggested Si limitation of uptake during that season only. No evidence of P limitation of biomass or productivity was evident.


Marine and Freshwater Research | 2006

Effects of iron additions on filament growth and productivity of the cyanobacterium Lyngbya majuscula

Kathleen S. Ahern; Judith M. O'Neil; James Udy; Simon Albert

The bioavailability of iron, in combination with essential macronutrients such as phosphorus, has been hypothesised to be linked to nuisance blooms of the toxic cyanobacterium Lyngbya majuscula. The present laboratory study used two biological assay techniques to test whether various concentrations of added iron (inorganic and organically chelated) enhanced L. majuscula filament growth and productivity (C-14-bicarbonate uptake rate). Organically chelated iron (FeEDTA) with adequate background concentrations of phosphorus and molybdenum caused the largest increases (up to 4.5 times the control) in L. majuscula productivity and filament growth. The addition of inorganic iron (without added phosphorus or molybdenum) also stimulated L. majuscula filament growth. However, overall the FeEDTA was substantially and significantly more effective in promoting L. majuscula growth than inorganic iron (FeCl3). The organic chelator (EDTA) alone and molybdenum alone also enhanced L. majuscula growth but to a lesser extent than the chelated iron. The results of the present laboratory study support the hypothesis that iron and chelating organic compounds may be important in promoting blooms of L. majuscula in coastal waters of Queensland, Australia.


Limnology and Oceanography | 2001

Virus-like particle distribution and abundance in sediments and overlying waters along eutrophication gradients in two subtropical estuaries

Ian Hewson; Judith M. O'Neil; Jed A. Fuhrman; William C. Dennison


Limnology and Oceanography | 2006

Nitrogen fixation and release of fixed nitrogen by Trichodesmium spp. in the Gulf of Mexico

Margaret R. Mulholland; Peter W. Bernhardt; Cynthia A. Heil; Deborah A. Bronk; Judith M. O'Neil


Marine Pollution Bulletin | 2005

Blooms of the cyanobacterium Lyngbya majuscula in coastal Queensland, Australia: disparate sites, common factors

Simon Albert; Judith M. O'Neil; James Udy; Kathleen S. Ahern; Cherie M. OSullivan; William C. Dennison


Journal of Plankton Research | 1998

The colonial cyanobacterium Trichodesmium as a physical and nutritional substrate for the harpacticoid copepod Macrosetella gracilis

Judith M. O'Neil


Aquatic Microbial Ecology | 2001

Effects of concentrated viral communities on photosynthesis and community composition of co- occurring benthic microalgae and phytoplankton

Ian Hewson; Judith M. O'Neil; Cynthia A. Heil; Gunnar Bratbak; William C. Dennison


Estuarine Coastal and Shelf Science | 2013

Elucidating terrestrial nutrient sources to a coastal lagoon, Chincoteague Bay, Maryland, USA

B. Fertig; Judith M. O'Neil; Kris Beckert; C.J. Cain; D.M. Needham; Tim J. B. Carruthers; William C. Dennison


Harmful Algae | 2005

Ecophysiology of the marine cyanobacterium, (Oscillatoriaceae) in Moreton Bay, Australia

Andrew R. Watkinson; Judith M. O'Neil; William C. Dennison

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William C. Dennison

University of Maryland Center for Environmental Science

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Simon Albert

University of Queensland

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Cynthia A. Heil

Florida Fish and Wildlife Conservation Commission

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JoAnn M. Burkholder

North Carolina State University

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Patricia M. Glibert

University of Maryland Center for Environmental Science

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Ian Hewson

University of Queensland

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