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Landry, MR, Ohman MD, Goericke R, Stukel MR, Barbeau KA, Bundy R, Kahru M.  2012.  Pelagic community responses to a deep-water front in the California Current Ecosystem: overview of the A-Front Study. Journal of Plankton Research. 34:739-748.   10.1093/plankt/fbs025   AbstractWebsite

In October 2008, we investigated pelagic community composition and biomass, from bacteria to fish, across a sharp frontal gradient overlying deep waters south of Point Conception, California. This northsouth gradient, which we called A-Front, was formed by the eastward flow of the California Current and separated cooler mesotrophic waters of coastal upwelling origin to the north, from warm oligotrophic waters of likely mixed subarcticsubtropical origin to the south. Plankton biomass and phytoplankton growth rates were two to three times greater on the northern side, and primary production rates were elevated 5-fold to the north. Compared with either of the adjacent waters, the frontal interface was strongly enriched and uniquely defined by a subsurface bloom of large diatoms, elevated concentrations of suspension-feeding zooplankton, high bioacoustical estimates of pelagic fish and enhanced bacterial production and phytoplankton biomass and photosynthetic potential. Such habitats, though small in areal extent, may contribute disproportionately and importantly to regional productivity, nutrient cycling, carbon fluxes and trophic ecology. As a general introduction to the A-Front study, we provide an overview of its design and implementation, a brief summary of major findings and a discussion of potential mechanisms of plankton enrichment at the front.

Lee, ZP, Marra J, Perry MJ, Kahru M.  2015.  Estimating oceanic primary productivity from ocean color remote sensing: A strategic assessment. Journal of Marine Systems. 149:50-59.   10.1016/j.jmarsys.2014.11.015   AbstractWebsite

It has long been realized that approaches using satellite ocean-color remote sensing are the only feasible means to quantify primary productivity (PP) adequately for the global ocean. Through decades of dedicated efforts and with the help of various satellite ocean-color missions, great progresses have been achieved in obtaining global PP as well as its spatial and temporal variations. However, there still exist wide differences between satellite estimations and in situ measurements, as well as large discrepancies among results from different models. The reasons for these large differences are many, which include uncertainties in measurements, errors in satellite-derived products, and limitations in the modeling approaches. Unlike previous round-robin reports on PP modeling where the performance of specific models was evaluated and compared, here we try to provide a candid overview of three primary modeling strategies and the nature of present satellite ocean-color products. We further highlight aspects where efforts should be focused in the coming years, with the overarching goal of reducing the gaps between satellite modeling and in situ measurements. (C) 2014 Elsevier B.V. All rights reserved.

Leising, AW, Schroeder ID, Bograd SJ, Bjorkstedt EP, Field J, Sakuma K, Abell J, Robertson RR, Tyburczy J, Peterson WT, Brodeur R, Barcelo C, Auth TD, Daly EA, Campbell GS, Hildebrand JA, Suryan RM, Gladics AJ, Horton CA, Kahru M, Manzano-Sarabia M, McClatchie S, Weber ED, Watson W, Santora JA, Sydeman WJ, Melin SR, DeLong RL, Largier J, Kim SY, Chavez FP, Golightly RT, Schneider SR, Warzybok P, Bradley R, Jahncke J, Fisher J, Peterson J.  2014.  State of the California Current 2013-14: El Nino looming. California Cooperative Oceanic Fisheries Investigations Reports. 55:51-87. AbstractWebsite

In 2013, the California current was dominated by strong coastal upwelling and high productivity. Indices of total cumulative upwelling for particular coastal locations reached some of the highest values on record. Chlorophyll a levels were high throughout spring and summer. Catches of upwelling-related fish species were also high. After a moderate drop in upwelling during fall 2013, the California current system underwent a major change in phase. Three major basin-scale indicators, the PDO, the NPGO, and the ENSO-MEI, all changed phase at some point during the winter of 2013/14. The PDO changed to positive values, indicative of warmer waters in the North Pacific; the NPGO to negative values, indicative of lower productivity along the coast; and the MEI to positive values, indicative of an oncoming El Nino. Whereas the majority of the California Current system appears to have transitioned to an El Nino state by August 2014, based on decreases in upwelling and chlorophyll a concentration, and increases in SST, there still remained pockets of moderate upwelling, cold water, and high chlorophyll a biomass at various central coast locations, unlike patterns seen during the more major El Ninos (e.g., the 97-98 event). Catches of rockfish, market squid, euphausiids, and juvenile sanddab remained high along the central coast, whereas catches of sardine and anchovy were low throughout the CCS. 2014 appears to be heading towards a moderate El Nino state, with some remaining patchy regions of upwelling-driven productivity along the coast. Superimposed on this pattern, three major regions have experienced possibly non-El Nino-related warming since winter: the Bering Sea, the Gulf of Alaska, and offshore of southern California. It is unclear how this warming may interact with the predicted El Nino, but the result will likely be reduced growth or reproduction for many key fisheries species.

Lin, JF, Lee Z, Ondrusek M, Kahru M.  2016.  Attenuation coefficient of usable solar radiation of the global oceans. Journal of Geophysical Research-Oceans. 121:3228-3236.   10.1002/2015jc011528   AbstractWebsite

Usable solar radiation (USR) represents spectrally integrated solar energy in the spectral range of 400-560 nm, a domain where photons penetrate the most in oceanic waters and thus contribute to photosynthesis and heating at deeper depths. Through purely numerical simulations, it was found that the diffuse attenuation coefficient of downwelling USR (K-d(USR), m(-1)) is nearly a constant vertically in the upper water column for clear waters and most turbid waters. Subsequently an empirical model was developed to estimate Kd(USR) based on the diffuse attenuation coefficient at 490 nm (Kd(490), m(-1)). We here evaluate this relationship using data collected from a wide range of oceanic and coastal environments and found that the relationship between Kd(490) and Kd(USR) developed via the numerical simulation is quite robust. We further refined this relationship to extend the applicability to "clearest" natural waters. This refined relationship was then used to produce sample distribution of Kd(USR) of global oceans. As expected, extremely low Kd(USR) (similar to 0.02 m(-1)) was observed in ocean gyres, while significantly higher Kd(USR) (similar to 5.2 m(-1)) was found in very turbid coastal regions. A useful application of Kd(USR) is to easily and accurately propagate surface USR to deeper depths, potentially to significantly improve the estimation of basin scale primary production and heat fluxes in the upper water column.

Lluch-Cota, SE, Aragon-Noriega EA, Arreguin-Sanchez F, Aurioles-Gamboa D, Bautista-Romero JJ, Brusca RC, Cervantes-Duarte R, Cortes-Altamirano R, Del-Monte-Luna P, Esquivel-Herrera A, Fernandez G, Hendrickx ME, Hernandez-Vazquez S, Herrera-Cervantes H, Kahru M, Lavin M, Lluch-Belda D, Lluch-Cota DB, Lopez-Martinez J, Marinone SG, Nevarez-Martinez MO, Ortega-Garcia S, Palacios-Castro E, Pares-Sierra A, Ponce-Diaz G, Ramirez-Rodriguez M, Salinas-Zavala CA, Schwartzlose RA, Sierra-Beltran AP.  2007.  The Gulf of California: Review of ecosystem status and sustainability challenges. Progress in Oceanography. 73:1-26.   10.1016/j.pocean.2007.01.013   AbstractWebsite

The Gulf of California is unique because of its geographical location and conformation. It hosts diverse ecosystems and important fisheries that support industry and provide livelihood to coastal settlements. It is also the site of interests and problems, and an intense interaction among managers, producers, and conservationists. In this report, we scrutinize the abiotic (hydrography, climate, ocean circulation, and chemistry) and biotic (phyto- and zooplankton, fish, invertebrates, marine mammals, birds, and turtles) components of the marine ecosystem, and some particular aspects of climate variability, endemisms, harmful algal blooms, oxygen minimum layer, and pollution. We also review the current conditions and conflicts around the main fisheries (shrimp, small and large pelagic fishes, squid, artisanal and sportfishing), the most important human activity in the Gulf of California. We cover some aspects of management and conservation of fisheries, especially the claimed overexploitation of fish resources and the ecosystems, and review proposals for creating networks of marine protected areas. We conclude by identifying main needs for information and research, particularly the integration of data bases, the implementation of models and paleoreconstructions, establishment of monitoring programs, and the evaluation of fishing impacts and management actions. (c) 2007 Elsevier Ltd. All rights reserved.