Search

Your search keyword '"Wilding, John G"' showing total 3 results
Start Over Author "Wilding, John G"
3 results on '"Wilding, John G"'

2. Regional to Global Assessments of Phytoplankton Dynamics From The SeaWiFS Mission

Author

Siegel, David, Behrenfeld, Michael, Maritorena, Stephanie, McClain, Charles R, Antoine, David, Bailey, Sean W, Bontempi, Paula S, Boss, Emmanuel S, Dierssen, Heidi M, Doney, Scott C, Eplee, R. E., Jr, Evans, Robert H, Feldman, Gene C, Fields, Erik, Franz, Bryan A, Kuring, Norman A, Mengelt, Claudia, Nelson, Norman B, Patt, Fred S, Robinson, Wayne D, Sarmiento, J. L, Swan, C. M, Werdell, Paul J, Westberry, T. K, Wilding, John G, and Yoder, J. A

Subjects
Earth Resources And Remote Sensing, Oceanography
Abstract

Photosynthetic production of organic matter by microscopic oceanic phytoplankton fuels ocean ecosystems and contributes roughly half of the Earth's net primary production. For 13 years, the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) mission provided the first consistent, synoptic observations of global ocean ecosystems. Changes in the surface chlorophyll concentration, the primary biological property retrieved from SeaWiFS, have traditionally been used as a metric for phytoplankton abundance and its distribution largely reflects patterns in vertical nutrient transport. On regional to global scales, chlorophyll concentrations covary with sea surface temperature (SST) because SST changes reflect light and nutrient conditions. However, the oceanmay be too complex to be well characterized using a single index such as the chlorophyll concentration. A semi-analytical bio-optical algorithm is used to help interpret regional to global SeaWiFS chlorophyll observations from using three independent, well-validated ocean color data products; the chlorophyll a concentration, absorption by CDM and particulate backscattering. First, we show that observed long-term, global-scale trends in standard chlorophyll retrievals are likely compromised by coincident changes in CDM. Second, we partition the chlorophyll signal into a component due to phytoplankton biomass changes and a component caused by physiological adjustments in intracellular chlorophyll concentrations to changes in mixed layer light levels. We show that biomass changes dominate chlorophyll signals for the high latitude seas and where persistent vertical upwelling is known to occur, while physiological processes dominate chlorophyll variability over much of the tropical and subtropical oceans. The SeaWiFS data set demonstrates complexity in the interpretation of changes in regional to global phytoplankton distributions and illustrates limitations for the assessment of phytoplankton dynamics using chlorophyll retrievals alone.

Published
2013
Full Text
View/download PDF

3. Satellite-Derived Photic Depth on the Great Barrier Reef: Spatio-Temporal Patterns of Water Clarity.

Author

Weeks, Scarla, Werdell, P. Jeremy, Schaffelke, Britta, Canto, Marites, Zhongping Lee, Wilding, John G., and Feldman, Gene C.

Subjects
MARINE organisms, TELECOMMUNICATION satellites, LIGHT transmission, SPATIO-temporal variation, SEASONAL variations in biogeochemical cycles, CLIMATE change, COMPOSITION of water, REGRESSION analysis
Abstract

Detecting changes to the transparency of the water column is critical for understanding the responses of marine organisms, such as corals, to light availability. Long-term patterns in water transparency determine geographical and depth distributions, while acute reductions cause short-term stress, potentially mortality and may increase the organisms' vulnerability to other environmental stressors. Here, we investigated the optimal, operational algorithm for light attenuation through the water column across the scale of the Great Barrier Reef (GBR), Australia. We implemented and tested a quasi-analytical algorithm to determine the photic depth in GBR waters and matched regional Secchi depth (ZSD) data to MODIS-Aqua (2002-2010) and SeaWiFS (1997-2010) satellite data. The results of the in situ ZSD/satellite data matchup showed a simple bias offset between the in situ and satellite retrievals. Using a Type II linear regression of log-transformed satellite and in situ data, we estimated ZSD and implemented the validated ZSD algorithm to generate a decadal satellite time series (2002-2012) for the GBR. Water clarity varied significantly in space and time. Seasonal effects were distinct, with lower values during the austral summer, most likely due to river runoff and increased vertical mixing, and a decline in water clarity between 2008-2012, reflecting a prevailing La Niña weather pattern. The decline in water clarity was most pronounced in the inshore area, where a significant decrease in mean inner shelf ZSD of 2.1 m (from 8.3 m to 6.2 m) occurred over the decade. Empirical Orthogonal Function Analysis determined the dominance of Mode 1 (51.3%), with the greatest variation in water clarity along the mid-shelf, reflecting the strong influence of oceanic intrusions on the spatio-temporal patterns of water clarity. The newly developed photic depth product has many potential applications for the GBR from water quality monitoring to analyses of ecosystem responses to changes in water clarity. [ABSTRACT FROM AUTHOR]

Published
2012
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results