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Variation in copepod egg production rate across spatial gradients in the California Current Ecosystem

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Presenter/Primary Author: 
Catherine Nickels
Mark D. Ohman

Areas of the ocean where two water parcels meet, know as fronts, define regions of sharp spatial gradients. Fronts often separate coastal, high productivity waters from oligotrophic, offshore zones but the frontal features themselves may also be areas of elevated nutrient fluxes and phytoplankton and microzooplankton concentrations.   Under such conditions, suspension-feeding copepods, crustacean zooplankters that feed on microplankton, would be expected to have elevated ingestion rates within the frontal region. This increase in food intake could result in an increase in copepod reproductive success through an enhanced rate of egg production and recruitment.  On CCE-LTER process cruises in the California Current Ecosystem up to three species of copepods (Calanus pacificus, Metridia pacifica, and Eucalanus californicus) were collected at sites across 2 frontal regions and incubated at sea in simulated in situ conditions to determine their egg production rates and egg hatching success. These rates were then analyzed to test the hypothesis of enhanced copepod reproductive success in regions of sharp frontal gradients.

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Background Photo by: Nicole Hansen - Jornada (JRN) LTER