A model to estimate chlorophyll-a concentration and yellow substance absorption at 440 nm from irradiance measurements made at varying depths is examined. The derivation of the model, requiring irradiance measurements at three wavebands, is presented and tested on data collected in oligotrophic (with low chlorophyll concentrations) waters and in coastal...
The eastern South Pacific (ESP) oxygen minimum zone (OMZ) is a permanent hydrographic feature located directly off the coasts of northern Chile and Peru. The ESP OMZ reaches from coastal waters out to thousands of kilometers offshore, and can extend from the near surface to depths greater than 700 m....
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...
Measurements at the Hawaii Ocean Time-series (HOT) Station ALOHA (22 degrees 45'N, 158 degrees W) have revealed a significant, approximately 50% increase in euphotic zone depth-integrated rates of primary production ( PP; mol C fixed m(-2) d(-1)) based on in situ C-14 experiments. The character of the nearly two-decade increasing...
Nitrate concentrations, chlorophyll a (Chl a) fluorescence, radiance, salinity, and
temperature were measured on the Hawaii Air-Sea Logging Experiment, A Long-Term
Oligotrophic Habitat Assessment (HALE ALOHA) mooring located near the Hawaii
Ocean Time-Series (HOT) Program’s Station ALOHA (22°45’N; 158°W). Nitrate
concentrations were determined with OsmoAnalyzers deployed at depths of 120...
During austral summer 1997, satellite imagery revealed enhanced chlorophyll associated with the Antarctic Polar Front at 170°W. Phytoplankton growth conditions during the early stages of the spring increase were investigated on the Antarctic Environment and Southern Ocean Process Study Survey I cruise using flow cytometry (FCM) and microscopy to characterize...
The euphotic zone below the deep chlorophyll maximum layer (DCML) at Station ALOHA (a long-term oligotrophic habitat assessment; 22º45′N, 158º00′W) transects the nearly permanently stratified upper thermocline. Hence, seasonal changes in solar radiation control the balance between photosynthesis and respiration in this lightlimited region. Combining profiles of radiance reflectance, algal...
Despite the importance of the spring phytoplankton bloom off Oregon as a food source for zooplankton, little is known about the sources of phytoplankton seed stock for the bloom or its timing. Experiments were conducted in the late winter to determine if the benthic boundary layer (BBL) could be a...
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...
Satellite-derived data provide the temporal means and seasonal and nonseasonal
variability of four physical and biological parameters off Oregon and Washington
(41°–48.5°N). Eight years of data (1998–2005) are available for surface chlorophyll
concentrations, sea surface temperature (SST), and sea surface height, while six years of
data (2000–2005) are available for...
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...
We constructed an experimental apparatus that used lasers to provide the probe beams for measuring the transient absorption kinetics of bacterioplankton that contain proteorhodopsin, a microbial protein that binds retinal and is analogous to animal rhodopsin. With this approach we were able to observe photocycles characteristic of functioning retinylidene ion...
The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra spacecraft contains spectral bands that allow retrieval of solar-induced phytoplankton chlorophyll fluorescence emission radiance. Concurrent airborne laser-induced (and water-Raman normalized) phytoplankton chlorophyll fluorescence data is used to successfully validate the MODIS chlorophyll fluorescence line height (FLH) retrievals within Gulf Stream, continental...