The annual cycle and biological effects of the Costa Rica Dome

NOAA/National Marine Fisheries Service (NMFS), Southwest Fisheries Science Center, P.O. Box 271, La Jolla, CA 92038, USA
Deep Sea Research Part I Oceanographic Research Papers (Impact Factor: 2.57). 02/2002; 49(2):321-338. DOI: 10.1016/S0967-0637(01)00057-7


The Costa Rica Dome is similar to other tropical thermocline domes in several respects: it is part of an east–west thermocline ridge associated with the equatorial circulation, surface currents flow cyclonically around it, and its seasonal evolution is affected by large-scale wind patterns. The Costa Rica Dome is unique because it is also forced by a coastal wind jet. Monthly climatological fields of thermocline depth and physical forcing variables (wind stress curl and surface current divergence) were analyzed to examine the structure and seasonal evolution of the dome. The annual cycle of the dome can be explained by wind forcing in four stages: (1) coastal shoaling of the thermocline off the Gulf of Papagayo during February–April, forced by Ekman pumping on the equatorward side of the Papagayo wind jet; (2) separation from the coast during May–June when the intertropical convergence zone (ITCZ) moves north to the countercurrent thermocline ridge, the wind jet stops, and the North Equatorial Countercurrent extends toward the coast on the equatorward flank of the ridge; (3) countercurrent thermocline ridging during July–November, when the dome expands to the west as the countercurrent thermocline ridge shoals beneath a band of cyclonic wind stress curl on the poleward side of the ITCZ; and (4) deepening during December–January when the ITCZ moves south and strong trade winds blow over the dome. Coastal eddies may be involved in the coastal shoaling observed during February–March. A seasonally predictable, strong, and shallow thermocline makes the Costa Rica Dome a distinct biological habitat where phytoplankton and zooplankton biomass are higher than in surrounding tropical waters. The physical structure and biological productivity of the dome affect the distribution and feeding of whales and dolphins, probably through forage availability.

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Available from: Paul C. Fiedler,
    • "Offshore upwelling in the CRD, separated from the coast, becomes distinctly visible in satellite images of sea surface cooling and elevated chlorophyll (Chl a) between June and August (Fiedler, 2002). Enhanced primary production suggested by the high Chl a in satellite images of the CRD (Pennington et al., 2006) is accompanied by uniquely high concentrations of Synechococcus, exceeding 10 6 cells mL 21 (Fiedler, 2002; Saito et al., 2005). Productivity of the CRD is further believed to be trace-metal limited, suppressing diatoms (Franck et al., 2005) and blooms of larger phytoplankton cells that typically characterize upwelling features. "
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    ABSTRACT: We investigated standing stocks and grazing rates of mesozooplankton assemblages in the Costa Rica Dome (CRD), an open-ocean upwelling ecosystem in the eastern tropical Pacific. While phytoplankton biomass in the CRD is dominated by picophytoplankton (<2-µm cells) with especially high concentrations of Synechococcus spp., we found high mesozooplankton biomass (∼5 g dry weight m−2) and grazing impact (12–50% integrated water column chlorophyll a), indicative of efficient food web transfer from primary producers to higher levels. In contrast to the relative uniformity in water-column chlorophyll a and mesozooplankton biomass, variability in herbivory was substantial, with lower rates in the central dome region and higher rates in areas offset from the dome center. While grazing rates were unrelated to total phytoplankton, correlations with cyanobacteria (negative) and biogenic SiO2 production (positive) suggest that partitioning of primary production among phytoplankton sizes contributes to the va
    Journal of Plankton Research 10/2015; · 2.41 Impact Factor
    • "The Costa Rica Dome (CRD), residing several hundred kilometers off the coast of Central America 98N, 908W, is one such system. Openocean upwelling develops seasonally at the CRD associated with the western shoaling of the 108N thermocline ridge (Fiedler, 2002). In mid-summer satellite images, the CRD is often the most prominent open-ocean area of elevated chlorophyll in the northern ETP. "

    Journal of Plankton Research 10/2015; DOI:10.1093/plankt/fbv089 · 2.41 Impact Factor
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    • "The marine area represents 0.16% of the world's ocean surface but harbors 3.5% of the known marine biodiversity [42] [43]. The Costa Rican Dome (8–10°N, 88–90°W) is an area with high primary production that supports a high zooplankton biomass [44] [45] contributing to the high biodiversity. "
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