Alan D. Weidemann

Dr. Weidemann is an adjunct faculty member at University of Southern Mississippi, Department of Marine Science, as well as a researcher at the Naval Research Laboratory. His areas of specialization are optical oceanography, propagation of ultraviolet, visible and near-IR electromagnetic radiant energy in oceanic environments, and relationship between inherent and apparent optical properties. Present research is measurement of optical properties on unmanned gliders and development of a flow cytometer to function on the unmanned glid

Optical Properties of the Kara Sea

This study was motivated by the need to understand dispersion processes which affect the redistribution of nuclear wastes in the Arctic from dump sites in the Kara Sea and in the rivers which flow into the Kara Sea. We focus on vertical profiles of light beam transmission and fluorometry made over the delta region fronting the Ob and Yenisey Rivers and over the East Novaya Zemlya Trough (ENZT). The delta region fronting the Ob River Estuary contains a large repository of particles in a dense bottom nepheloid layer with a maximum centered similar to 100 km in front of the estuary entrance and covering an area of roughly 200 km diameter. This suspended particle mass repository appears to contain both sediments and detritus and lends credence to the Lisitsyn [1995] concept of the marginal filter zone. In the deep water of the ENZT we found a strong increase of beam attenuation with depth, indicating a relatively large increase of particle mass concentration from similar to 50 m to the bottom (depths in excess of 300 m). The strongest concentration was adjacent to the southeast coast of Novaya Zemlya. We suggest that a type of hyperpycnical flow occurs from accumulation of sediments in the bottom waters of Novaya Zemlya fjords which then cascades down the steep slopes adjacent to the island, producing the particle mass distribution as observed by the transmissometer. The accumulation of these repositories of high particle mass concentrations in suspension would suggest that the residence time is high but that storm-driven events could act to disperse the material

A Maritime Advanced Geospatial Intelligence Craft for Oil Spill Response: White Paper

In line with current research thrusts on unmanned systems, the University of New Orleans has formed a collaborative team from industry, academia, and government (e.g., Department of Homeland Security). UNO’s intent is to work with organizations such as the Bureau of Safety and Environmental Enforcement (BSEE) to experiment and demonstrate the potential offered by Unmanned Surface Vessels within the Gulf of Mexico

A Maritime Advanced Geospatial Intelligence Craft for Oil Spill Response: White Paper

In line with current research thrusts on unmanned systems, the University of New Orleans has formed a collaborative team from industry, academia, and government (e.g., Department of Homeland Security). UNO’s intent is to work with organizations such as the Bureau of Safety and Environmental Enforcement (BSEE) to experiment and demonstrate the potential offered by Unmanned Surface Vessels within the Gulf of Mexico

Bio-optical Properties of Cyanobacteria Blooms in Western Lake Erie

There is a growing use of remote sensing observations for detecting and quantifying freshwater cyanobacteria populations, yet the inherent optical properties of these communities in natural settings, fundamental to bio-optical algorithms, are not well known. Toward bridging this knowledge gap, we measured a full complement of optical properties in western Lake Erie during cyanobacteria blooms in the summers of 2013 and 2014. Our measurements focus attention on the optical uniqueness of cyanobacteria blooms, which have consequences for remote sensing and bio-optical modeling. We found the cyanobacteria blooms in the western basin during our field work were dominated by Microcystis, while the waters in the adjacent central basin were dominated by Planktothrix. Chlorophyll concentrations ranged from 1 to over 135 μg/L across the study area with the highest concentrations associated with Microcystis in the western basin. We observed large, amorphous colonial Microcystis structures in the bloom area characterized by high phytoplankton absorption and high scattering coefficients with a mean particle backscatter ratio at 443 nm \u3e 0.03, which is higher than other plankton types and more comparable to suspended inorganic sediments. While our samples contained mixtures of both, our analysis suggests high contributions to the measured scatter and backscatter coefficients from cyanobacteria. Our measurements provide new insights into the optical properties of cyanobacteria blooms, and indicate that current semi-analytic models are likely to have problems resolving a closed solution in these types of waters as many of our observations are beyond the range of existing model components. We believe that different algorithm or model approaches are needed for these conditions, specifically for phytoplankton absorption and particle backscatter components. From a remote sensing perspective, this presents a challenge not only in terms of a need for new algorithms, but also for determining when to apply the best algorithm for a given situation. These results are new in the sense that they represent a complete description of the optical properties of freshwater cyanobacteria blooms, and are likely to be representative of bloom conditions for other systems containing Microcystis cells and colonies

The Confidence Database

Understanding how people rate their confidence is critical for the characterization of a wide range of perceptual, memory, motor and cognitive processes. To enable the continued exploration of these processes, we created a large database of confidence studies spanning a broad set of paradigms, participant populations and fields of study. The data from each study are structured in a common, easy-to-use format that can be easily imported and analysed using multiple software packages. Each dataset is accompanied by an explanation regarding the nature of the collected data. At the time of publication, the Confidence Database (which is available at https://osf.io/s46pr/) contained 145 datasets with data from more than 8,700 participants and almost 4 million trials. The database will remain open for new submissions indefinitely and is expected to continue to grow. Here we show the usefulness of this large collection of datasets in four different analyses that provide precise estimations of several foundational confidence-related effects

Alan D. Weidemann

Dr. Weidemann is an adjunct faculty member at University of Southern Mississippi, Department of Marine Science, as well as a researcher at the Naval Research Laboratory. His areas of specialization are optical oceanography, propagation of ultraviolet, visible and near-IR electromagnetic radiant energy in oceanic environments, and relationship between inherent and apparent optical properties. Present research is measurement of optical properties on unmanned gliders and development of a flow cytometer to function on the unmanned glid

Phytoplankton Spectral Absorption as Influenced by Community Size Structure and Pigment Composition

Assessments were made of the relative importance of package effects and pigment composition in contributing to variations in spectral absorption in shelf waters off North Carolina during May 1997 and off west Florida during October 1998. Measurements of spectral absorption of size-fractionated particulate material on glass fibre filters were made using two methods, the transmittance-reflectance (T-R) method and the quantitative filter technique (QFT). Spectral absorption of phytoplankton pigments was decomposed into a series of 13 Gaussian absorption bands, and absorption band peak heights were related to concentrations of major pigment classes. Maximum weight-specific pigment absorption coefficients for individual absorption bands (p*(m)) derived from the fit of a hyperbolic tangent function to the data were found to be similar for North Carolina and west Florida shelf waters. The values were used to reconstruct spectral absorption in the absence of pigment packaging, which was then compared to measured absorption to provide an assessment of pigment packaging. Package effects were found to be responsible for up to a 62% reduction in the amplitude of major absorption bands, particularly for samples from low-salinity waters and for populations dominated by larger (\u3e3 mum) phytoplankton. Variations in pigment composition were also found to have an impact, although it was smaller (10-28%), on variations in total absorption. Potential bio-optical applications of the Gaussian decomposition approach include the estimation of pigment concentrations from in situ or remotely sensed ocean colour observations. Alternatively, where pigment concentrations are known, it may be possible to estimate absorption. Successful application of such techniques may necessitate characterizations of coefficients specific to a given region and time

Variations in Phytoplankton Pigments, Size Structure and Community Composition Related to Wind Forcing and Water Mass Properties on the North Carolina Inner Shelf

Variations in phytoplankton pigments, size structure and community composition were examined in inner shelf waters off North Carolina in relationship to water mass properties subject to the influence of low salinity outflow from the Chesapeake Bay, alternations in wind forcing and interactions with shelf water masses. Observations were made aboard the R/V Edwin Link during May 1997. Episodes of upwelling-favorable conditions were accompanied by detachment of the low salinity outflow plume from the coast, and enhanced dispersion and mixing with shelf waters. Distinct water masses were identified using cluster analysis of temperature-salinity (T-S) properties. Two major clusters, distinguished on the basis of relatively high and low salinities, were identified as ambient coastal water (A) and modified bay water (B). Each of these could be further separated into two water mass types characterized by relatively high and low temperatures. The pigment and taxonomic composition of these water masses were examined. The carotenoid fucoxanthin was generally the most abundant accessory pigment. Zeaxanthin and chlorophyll b were also relatively abundant at most stations. Ratios to chlorophyll a of 19\u27-hexanoyloxyfucoxanthin and peridinin were higher for the high salinity clusters. A shift to downwelling-favorable conditions toward the latter part of the cruise gave rise to a narrow, southward flowing jet of low salinity Chesapeake Bay water corresponding to the low salinity, relatively high temperature water mass identified by cluster analysis. Fucoxanthin dominated the accessory pigments in this low salinity feature. Proportions of chlorophyll a associated with different phytoplankton classes, as estimated using CHEMTAX software (Mar. Ecol. Prog. Ser. 144 (1996) 265), varied among groups in a manner consistent with pigment composition. A diverse assemblage of diatoms, cyanobacteria, cryptophytes and prasinophytes accounted for the majority of chlorophyll a at most stations. Haptophytes and dinoflagellates were relatively more abundant in warmer, higher salinity stations. The low salinity jet exhibited high biomass and low diversity compared to other water masses. Its phytoplankton population was dominated by diatoms larger than 8 mum in diameter. The results demonstrate that phytoplankton community composition varies substantially among the different water masses in this coastal region and is subject to event scale (i.e., days to weeks) changes in relation to wind forcing and shelf circulation processes. (C) 2003 Elsevier Ltd. All rights reserved