Targeting Ecosystem Features for Conservation: Standing Crops in the Florida Everglades

Authors

  • Andrew M. Turner,

    1. Southeast Environmental Research Program and Department of Biological Sciences,
      Florida International University, Miami, FL 33199, U.S.A.
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  • Joel C. Trexler,

    Corresponding author
    1. Southeast Environmental Research Program and Department of Biological Sciences,
      Florida International University, Miami, FL 33199, U.S.A.
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  • C. Frank Jordan,

    1. Department of Biological Sciences, Loyola University of New Orleans, New Orleans, LA 70118, U.S.A.
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  • Sarah J. Slack,

    1. Southeast Environmental Research Program and Department of Biological Sciences,
      Florida International University, Miami, FL 33199, U.S.A.
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  • Pamela Geddes,

    1. Southeast Environmental Research Program and Department of Biological Sciences,
      Florida International University, Miami, FL 33199, U.S.A.
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  • John H. Chick,

    1. Southeast Environmental Research Program and Department of Biological Sciences,
      Florida International University, Miami, FL 33199, U.S.A.
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  • William F. Loftus

    1. Southeast Environmental Research Program and Department of Biological Sciences,
      Florida International University, Miami, FL 33199, U.S.A.
    2. U.S. Geological Survey, Biological Research Division, Everglades National Park Field Station,
      40001 State Road 9336, Homestead, FL 33034, U.S.A.
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§ Address correspondence to J. Trexler, email trexlerj@fiu.edu

Abstract

Abstract: The Everglades in southern Florida, U.S.A., is a major focus of conservation activities. The freshwater wetlands of the Everglades do not have high species richness, and no species of threatened aquatic animals or plants live there. We have, however, identified a distinctive ecological feature of the Everglades that is threatened by canal construction, draining, and nutrient enrichment from agricultural runoff. Compared to values reported from other freshwater systems, standing stocks of periphyton in relatively undisturbed areas of the Everglades were unusually high, and standing stocks of invertebrates and fish were unusually low. Averaging data gathered from nine sites and five sampling periods spanning 1 year, we found that periphyton standing crop was 88.2 g/m2 (ash-free dry mass), invertebrate standing stock was 0.64 g/m2 (dry mass), and fish standing stock was 1.2 g/m2 (dry mass of large and small species combined). We found that fish standing stocks were much higher in phosphorus-enriched sites than in nearby reference sites but that invertebrate standing stocks were similar in enriched and reference sites. Our results support the notion that oligotrophy is at least partially responsible for the low standing stocks of fish, but they also suggest that species interactions and a paucity of deep-water refugia are important. Anthropogenic eutrophication in Everglades marshes will lead to the loss of distinctive ecosystem features. A focus on species richness and “hot spots” of threatened species provides no basis for conservation of ecosystems like the Everglades. If oligotrophic ecosystems often have low species richness, they will be underrepresented in preservation networks based on some common criteria for establishing conservation priorities.

Abstract

Resumen: Los Everglades en el sur de los Estados Unidos constituyen un importante centro de actividades de conservación. Los humedales dulceacuícolas de los Everglades no tienen una riqueza de especies alta, y ninguna especie animal o vegetal amenazada vive ahí. Sin embargo, hemos identificado un rasgo ecológico distintivo de los Everglades que esta amenazado por la construcción de canales, el drenado y el enriquecimiento de nutrientes por actividades agrícolas. En comparación con los valores reportados para otros sistemas dulceacuícolas, la productividad del perifiton en áreas relativamente no perturbadas fue inusualmente alta, mientras que la productividad de invertebrados y peces fue inusualmente baja. El promedio de datos obtenidos en nueve sitios y durante cinco períodos de muestreo a lo largo de un año mostró que la productividad de perifiton fue de 88.2 g/m2 (peso seco sin cenizas), la de invertebrados fue de 0.64 g/m2 (peso seco) y la de peces fue de 1.2 g/m2 (peso seco de especies pequeñas y grandes combinadas). Encontramos que la productividad de peces fue mayor en sitios enriquecidos que en sitios de referencia cercanos, pero la productividad de invertebrados fue similar en sitios enriquecidos y de referencia. Nuestros resultados apoyan la idea de que la oligotrofía es responsable, por lo menos parcialmente, de la baja productividad de peces, pero también sugieren la importancia de las interacciones de especies y la escasez de refugios en aguas profundas. La eutroficación antropogénica en las marismas de los Everglades conducirá a la pérdida de rasgos distintivos del ecosistema. Enfocar la riqueza de especies y los “sitios críticos” para especies amenazadas no proporcionan bases para la conservación de ecosistemas como los Everglades. Si los ecosistemas oligotróficos tienen baja riqueza de especies, estarán subrepresentados en redes de conservación basadas en criterios comunes para el establecimiento de prioridades de conservación.

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