Browsing Cullen, John by Title
Now showing items 1-20 of 37
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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 ... -
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 ... -
Changes in buoyancy and chemical composition during growth of a coastal marine diatom: Ecological and biogeochemical consequences
Growth and sinking of the coastal marine diatom Thalassiosira weissflogii was studied during experiments in a 2.1 m tall water column. Under nutrient-replete conditions, T. weissflogii grew rapidly in the upper layer of ... -
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Distributions of Pigments and Primary Production in a Gulf-Stream Meander
An investigation was made of physical effects of Gulf Stream meandering on the vertical and horizontal distributions of photosynthetic pigments and primary production. Cruises were conducted in the vicinity of a meander ... -
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Fine-Scale Vertical Resolution of Chlorophyll and Photosynthetic Parameters in Shallow-Water Benthos
The vertical distributions of chlorophyll concentration and photosynthetic parameters of sediment-associated microalgae were measured with a resolution of 1 mm. Sediment and the overlying water were sampled at 3 sandy, ... -
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 ... -
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. ... -
Inferred influence of nutrient availability on the relationship between Sun-induced chlorophyll fluorescence and incident irradiance in the Bering Sea
This study examines variability in the relationship between Sun-induced chlorophyll fluorescence and incident solar irradiance as a potential diagnostic of the nutritional status of phytoplankton. The study site is the ... -
Inhibition of marine photosynthesis by ultraviolet radiation: Variable sensitivity of phytoplankton in the Weddell-Scotia Confluence during the austral spring
To assess the potential impacts of ozone depletion on photosynthesis in the Southern Ocean, we need to know more about effects of ultraviolet radiation (UV) on phytoplankton in Antarctic waters, where, in addition to ... -
Mapping coastal optical and biogeochemical variability using an autonomous underwater vehicle and a new bio-optical inversion algorithm
Autonomous underwater vehicles (AUVs) can map water conditions at high spatial ( horizontal and vertical) and temporal resolution, including under cloudy conditions when satellite and airborne remote sensing are not feasible. ... -
Methyl iodide in the NW Atlantic; spatial and seasonal variation
While the global ocean is an important source of atmospheric methyl iodide (CH (sub 3) I), the major producers of CH (sub 3) I within the ocean remain unclear. During a seasonal study in the NW Atlantic, the relationship ... -
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. ... -
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 ... -
New production in the warm waters of the Tropical Pacific Ocean
The average depth-integrated rate of new production in the tropical Pacific Ocean was estimated from a calculation of horizontal and vertical nitrate balance over the region enclosed by the climatological 26 degree C ... -
Ocean Fertilization Science, Policy, and Commerce
Over the past 20 years there has been growing interest in the concept of fertilizing the ocean with iron to abate global warming. This interest was catalyzed by basic scientific experiments showing that iron limits primary ...
