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Jackson, GA, Checkley DM.  2011.  Particle size distributions in the upper 100 m water column and their implications for animal feeding in the plankton. Deep-Sea Research Part I-Oceanographic Research Papers. 58:283-297.   10.1016/j.dsr.2010.12.008   AbstractWebsite

We deployed autonomous particle-sensing SOLOPC floats more than eight times during five cruises, amassing almost 400 profiles of particle size (d > 90 mu m) and abundance between the ocean surface and 100 m. The profiles consistently had subsurface maxima in particle volume. The median (by volume) equivalent spherical diameter for the particle distribution was 0.4-0.8 mm and increased with depth in a manner similar to that observed in coagulation simulations. There was a sharp cutoff at the bottom of the high particle concentration region. Estimation of particle fluxes made using the size distributions show an increasing downward movement through the particle field above the sharp particle cutoff. The increase of particle flux with depth through the euphotic zone implies a partial spatial separation of production and consumption. The sharp drop in particle volume and flux implies that the base of the particle-rich zone is a region of active particle consumption, possibly by zooplankton flux feeding. Our data show greater concentrations of zooplankton-type particles relative to marine snow-type particles below the particle maximum. Such behavior could explain why zooplankton are frequently observed at and immediately below the particle maximum rather than the productivity maximum and suggests an important role for flux feeding in carbon and nutrient cycling at the base of the particle maximum. This implies that zooplankton act as gatekeepers for the movement of organic matter to the mesopelagic. The ability of the SOLOPC to sample hourly with high resolution in the upper 100 m of the ocean provides a powerful complement for the study of particles where it has been difficult to use sediment traps. (C) 2011 Elsevier Ltd. All rights reserved.

Checkley, DM, Barth JA.  2009.  Patterns and processes in the California Current System. Progress in Oceanography. 83:49-64.   10.1016/j.pocean.2009.07.028   AbstractWebsite

The California Current System (CCS) is forced by the distribution of atmospheric pressure and associated winds in relation to the west coast of North America. In this paper, we begin with a simplified case of winds and a linear coast, then consider variability characteristic of the CCS, and conclude by considering future change. The CCS extends from the North Pacific Current (similar to 50 degrees N) to off Baja California, Mexico (similar to 15-25 degrees N) with a major discontinuity at Point Conception (34.5 degrees N). Variation in atmospheric pressure affects winds and thus upwelling. Coastal, wind-driven upwelling results in nutrification and biological production and a southward coastal jet. Offshore, curl-driven upwelling results in a spatially large, productive habitat. The California Current flows equatorward and derives from the North Pacific Current and the coastal jet. Dominant modes of spatial and temporal variability in physical processes and biological responses are discussed. High surface production results in deep and bottom waters depleted in oxygen and enriched in carbon dioxide. Fishing has depleted demersal stocks more than pelagic stocks, and marine mammals, including whales, are recovering. Krill, squid, and micronekton are poorly known and merit study. Future climate change will differ from past change and thus prediction of the CCS requires an understanding of its dynamics. Of particular concern are changes in winds, stratification, and ocean chemistry. (C) 2009 Elsevier Ltd. All rights reserved.

Devries, AL, Checkley DM, Raymond JA.  1972.  Physiology and biochemistry of freezing resistance in Antarctic fishes. Antarctic Journal of the United States. 7:78-79. AbstractWebsite
Checkley Jr., DM, Cooper T, Lennert C.  1996.  Plankton pattern within and below the surface mixed layer. EOS Trans. AGU. 76:198. Abstract
Curtis, KA, Checkley DM, Pepin P.  2007.  Predicting the vertical profiles of anchovy (Engraulis mordax) and sardine (Sardinops sagax) eggs in the California Current System. Fisheries Oceanography. 16:68-84.   10.1111/j.1365-2419.2006.00414.x   AbstractWebsite

Several published models exist for simulating vertical profiles of pelagic fish eggs, but no one has rigorously assessed their capacity to explain observed variability. In this study, we applied a steady-state model, with four different formulations for vertical diffusivity, to northern anchovy (Engraulis mordax) and Pacific sardine (Sardinops sagax) eggs in the California Current region. Vertical mixing profiles, based on wind speed and hydrography, were combined with estimated terminal ascent velocities of the eggs based on measurements of egg buoyancy and size, to simulate the vertical profiles of the eggs. We evaluated model performance with two data sets: (1) vertically stratified tows for both species and (2) paired samples for sardine eggs from 3-m depth and in vertically integrated tows. We used two criteria: whether the model predicted individual observed vertical profiles (1) as well as the observed mean and (2) better than the observed mean. Model predictions made with the formulation producing the most gradual profile of vertical diffusivity provided the best match to observations from both data sets and for both species. Addition of a random error term to the terminal ascent velocity further improved prediction for anchovy eggs, but not sardine. For the paired data, model prediction of integrated abundance from abundance at 3-m depth had significantly lower mean square error than prediction based on a linear regression of 3 m on integrated abundance. Our results support the feasibility of using data from the Continuous Underway Fish Egg Sampler quantitatively as well as qualitatively in stock assessments.