Browsing Cullen, John by Submit Date
Now showing items 1-20 of 37
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A semi-analytical model of the influence of phytoplankton community structure on the relationship between light attenuation and ocean color
A model was developed to examine the influence of phytoplankton community structure on the relationship between diffuse attenuation and ratios of upwelling radiance. Shifts in phytoplankton communities were represented by ... -
Assessment of the relationships between dominant cell size in natural phytoplankton communities and the spectral shape of the absorption coefficient
Size-fractionated chlorophyll concentration and phytoplankton absorption spectra were compared for a wide variety of natural communities. We found that, in general, when phytoplankton abundance increases, larger size-classes ... -
The spectral effects of clouds on solar irradiance
Knowledge of the spectral attenuation associated with clouds is important for accurate estimates of natural irradiance at the Earth's surface. We compare spectral measurements of visible downwelling irradiance, under varying ... -
Photosynthetic characteristics and estimated growth rates indicate grazing is the proximate control of primary production in the Equatorial Pacific
Macronutrients persist in the surface layer of the equatorial Pacific Ocean because the production of phytoplankton is limited. Measurements of photosynthesis as a function of irradiance (P-I) provide information on the ... -
Hypotheses to Explain High-Nutrient Conditions in the Open Sea
Oceanic high-nutrient, low-chlorophyll waters are characterized principally by the persistence of major nutrients at the sea surface. This condition indicates control of autotrophic production by something other than NO3 ... -
Optical detection and assessment of algal blooms
Concerns about harmful algal blooms (HABs) have grown in recent years. There is a pressing need for robust, quantitative, and cost-effective methods to detect and characterize algal blooms. Critical applications of these ... -
Biological processes and optical measurements near the sea surface: Some issues relevant to remote sensing
There is good evidence that bio-optical relationships are altered near the surface: (1) the fluorescence yield from chlorophyll declines, leading to bias in the estimation of pigment from fluorometry; (2) the modeled ... -
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Predicting and verifying the intended and unintended consequences of large-scale ocean iron fertilization
Ocean iron fertilization (OIF) is being considered as a strategy for mitigating rising atmospheric CO2 concentrations. One model for implementation is the sale of carbon offsets. Modeling studies predict that OIF has the ... -
Optical detection and assessment of algal blooms
Concerns about harmful algal blooms (HABs) have grown in recent years. There is a pressing need for robust, quantitative, and cost-effective methods to detect and characterize algal blooms. Critical applications of these ... -
Retrieval of phytoplankton biomass from simultaneous inversion of reflectance, the diffuse attenuation coefficient, and Sun-induced fluorescence in coastal waters
[1] A model has been developed to retrieve phytoplankton absorption, a proxy for phytoplankton biomass, from observations of reflectance ( R) and the diffuse attenuation coefficient (K-d) collected by moored radiometers ... -
New algorithms for MODIS sun-induced chlorophyll fluorescence and a comparison with present data products
We discuss important sources of variability in sun-induced chlorophyll fluorescence and examine difficulties in deriving fluorescence data products from satellite imagery, with a focus on the MODerate-resolution Imaging ... -
Phytoplankton Growth and Light-Absorption as Regulated by Light, Temperature, and Nutrients
Numerous studies of the growth of phytoplankton in the laboratory have demonstrated the dependence of cellular pigment concentration and growth rate upon light intensity, photoperiod, temperature, and nutrient supply. These ... -
Impact of ultraviolet radiation on marine crustacean zooplankton and ichthyoplankton: a synthesis of results from the estuary and Gulf of St. Lawrence, Canada
The objectives of the research program reported upon here were (1) to measure ambient levels of UV radiation and determine which variables most strongly affected its attenuation in the waters of the estuary and Gulf of St. ... -
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Modeling the effects of ultraviolet radiation on embryos of Calanus finmarchicus and Atlantic cod (Gadus morhua) in a mixing environment
It is well established that ultraviolet radiation (UVR, 280-400 nm) harms aquatic organisms. Reductions in productivity have been reported for phytoplankton, ichthyoplankton, and zooplankton in incubations exposed to UVR. ...