Significant seabird mortality on the Oregon (OR) and Washington (WA) coast in 2009 has been attributed
to a massive bloom of the dinoflagellate Akashiwo sanguinea (K. Hirasaka) G. Hansen & Ø. Moestrup.
Initial, albeit limited, observations suggested this bloom began in WA and reached OR waters through
southward transport. Here,...
Significant seabird mortality on the Oregon (OR) and Washington (WA) coast in 2009 has been attributed
to a massive bloom of the dinoflagellate Akashiwo sanguinea (K. Hirasaka) G. Hansen & Ø. Moestrup.
Initial, albeit limited, observations suggested this bloom began in WA and reached OR waters through
southward transport. Here,...
We report significant rates of dinitrogen (N₂) fixation in the central basins of the Gulf
of California (GC) during July–August 2005. Mixing model estimates based upon
δ¹⁵N values of particulate matter in the surface mixed layer indicate that N₂ fixation
provides as much as 35% to 48% of the phytoplankton-based...
Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45′N, 158°00′W) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further...
The relative lability, elemental stoichiometry, and remineralization rates of various particulate organic matter (POM) substrates by natural heterotrophic marine microorganisms was investigated. POM was harvested from laboratory cultures of a marine diazotroph (Trichodesmium IMS101), a cosmopolitan diatom (Thalassiosira weissflogii), a common marine cyanobacteria (Prochlorococcus MED4), and from surface waters off...
We investigated the effects of elevated pCO₂ on cultures of the unicellular N₂-fixing cyanobacterium Crocosphaera watsonii
WH8501. Using CO₂-enriched air, cultures grown in batch mode under high light intensity were exposed to initial conditions
approximating current atmospheric CO₂ concentrations (~400 ppm) as well as CO₂ levels corresponding to low- and...
The biological transformation of dinitrogen gas (N2) into combined forms(termed N2 fixation) by certain genera of oceanic cyanobacteria represents the largest incoming flux of nitrogen to the global ocean. As such, biological nitrogen fixation
plays a significant role in the regulation of oceanic productivity and the export of
carbon and...
The particle size distribution (PSD) is a critical aspect of the oceanic ecosystem. Local variability in the PSD can be indicative of shifts in microbial community structure and reveal patterns in cell growth and loss. The PSD also plays a central role in particle export by influencing settling speed. Satellite-based...
During the summer of 2012, we used laser diffractometry to investigate the temporal and vertical variability of the particle size spectrum (1.25–100 µm in equivalent diameter) in the euphotic zone of the North Pacific Subtropical Gyre. Particles measured with this optical method accounted for ∼40% of the particulate carbon stocks...
Di-nitrogen (N₂) fixation plays a well-recognized role in the enhancement of primary production
and arguably particle export in oligotrophic regions of the subtropical and tropical oceans.
However, recent evidence suggests that N₂ fixation may also be significant in regions of the
surface ocean proximate to or overlying zones of intense...
Since 1958 when Alfred C. Redfield (1) recognized the similarity between the ratios of elements in living biomass and those dissolved in the surrounding seawater, we have understood that microorganisms largely control the concentrations, distribution, and molecular makeup of nutritional resources in the ocean. The primary elemental ingredients for life,...
The accumulation of domoic acid (DA) and saxitoxins (STX), phycotoxins produced by some species of Pseudo-nitzschia and Alexandrium, respectively, in coastal food webs are a focus of research on the West Coast of the United States due to the deleterious effects they have on coastal ecosystems and economies. Results are...
We report the development of a numerical model simulating vertical movement of the
cyanobacterium Trichodesmium spp. Given a range of physiological parameters derived from the literature,
resultant model solutions allow us to explore the ecological significance of vertical migration
by Trichodesmium colonies in a stratified oligotrophic oceanic system such as...
Significant seabird mortality on the Oregon (OR) and Washington (WA) coast in 2009 has been attributed to a massive bloom of the dinoflagellate Akashiwo sanguinea (K. Hirasaka) G. Hansen & Ø. Moestrup. Initial, albeit limited, observations suggested this bloom began in WA and reached OR waters through southward transport. Here,...
Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45′N, 158°00′W) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further...
Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45′N, 158°00′W) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further...
We investigated the effects of elevated pCO₂ on cultures of the unicellular N₂-fixing cyanobacterium Crocosphaera watsonii
WH8501. Using CO₂-enriched air, cultures grown in batch mode under high light intensity were exposed to initial conditions
approximating current atmospheric CO₂ concentrations (~400 ppm) as well as CO₂ levels corresponding to low- and...
We investigated the effects of elevated pCO₂ on cultures of the unicellular N₂-fixing cyanobacterium Crocosphaera watsonii
WH8501. Using CO₂-enriched air, cultures grown in batch mode under high light intensity were exposed to initial conditions
approximating current atmospheric CO₂ concentrations (~400 ppm) as well as CO₂ levels corresponding to low- and...
We conducted laboratory experiments to assess the bioelemental plasticity of cultures of Trichodesmium
IMS101 under phosphorus (P)-replete, P-restricted, and light-limited conditions. The results reveal a high degree
of stoichiometric flexibility. Specifically, Trichodesmium IMS101 is capable of growth with carbon (C) : nitrogen
(N) : P ratios of C₅₈₅±₅₆ : N₉₀±₁₀...
We conducted 11 independent short-term carbon dioxide (CO₂) manipulation experiments using colonies of
the filamentous cyanobacteria Trichodesmium isolated on three cruises in the North Pacific Subtropical Gyre
(NPSG). Dinitrogen (N₂) and carbon (C) fixation rates of these colonies were compared over CO₂ conditions
ranging from ~ 18 Pa (equivalent to...
We present a spatially extensive record of dinitrogen (N₂) fixation rates and distributions
of N₂ fixing microorganisms along with the results of exogenous phosphorus (P) addition experiments
conducted during a series of cruises in the North Pacific Subtropical Gyre (NPSG). We measured the
N₂ and carbon (C) fixation rates of...