Ecosystems

, Volume 4, Issue 5, pp 430–451

The Function of Marine Critical Transition Zones and the Importance of Sediment Biodiversity

  • Lisa A. Levin
  • Donald F. Boesch
  • Alan Covich
  • Cliff Dahm
  • Christer Erséus
  • Katherine C. Ewel
  • Ronald T. Kneib
  • Andy Moldenke
  • Margaret A. Palmer
  • Paul Snelgrove
  • David Strayer
  • Jan Marcin Weslawski

Abstract

Estuaries and coastal wetlands are critical transition zones (CTZs) that link land, freshwater habitats, and the sea. CTZs provide essential ecological functions, including decomposition, nutrient cycling, and nutrient production, as well as regulation of fluxes of nutrients, water, particles, and organisms to and from land, rivers, and the ocean. Sediment-associated biota are integral to these functions. Functional groups considered essential to CTZ processes include heterotrophic bacteria and fungi, as well as many benthic invertebrates. Key invertebrate functions include shredding, which breaks down and recycles organic matter; suspension feeding, which collects and transports sediments across the sediment–water interface; and bioturbating, which moves sediment into or out of the seabed. In addition, macrophytes regulate many aspects of nutrient, particle, and organism dynamics above- and belowground. Animals moving within or through CTZs are vectors that transport nutrients and organic matter across terrestrial, freshwater, and marine interfaces. Significant threats to biodiversity within CTZs are posed by anthropogenic influences; eutrophication, nonnutrient pollutants, species invasions, overfishing, habitat alteration, and climate change affect species richness or composition in many coastal environments. Because biotic diversity in marine CTZ sediments is inherently low whereas their functional significance is great, shifts in diversity are likely to be particularly important. Species introductions (from invasion) or loss (from overfishing or habitat alteration) provide evidence that single-species changes can have overt, sweeping effects on CTZ structure and function. Certain species may be critically important to the maintenance of ecosystem functions in CTZs even though at present there is limited empirical evidence that the number of species in CTZ sediments is critical. We hypothesized that diversity is indeed important to ecosystem function in marine CTZs because high diversity maintains positive interactions among species (facilitation and mutualism), promoting stability and resistance to invasion or other forms of disturbance. The complexity of interactions among species and feedbacks with ecosystem functions suggests that comparative (mensurative) and manipulative approaches will be required to elucidate the role of diversity in sustaining CTZ functions.

Key Words: climate change; diversity; ecosystem function; estuaries; eutrophication; functional group; habitat alteration; mangrove; overfishing; salt marsh; species invasion; wetlands. 

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Copyright information

© Springer-Verlag New York Inc. 2001

Authors and Affiliations

  • Lisa A. Levin
    • 1
  • Donald F. Boesch
    • 2
  • Alan Covich
    • 3
  • Cliff Dahm
    • 4
  • Christer Erséus
    • 5
  • Katherine C. Ewel
    • 6
  • Ronald T. Kneib
    • 7
  • Andy Moldenke
    • 8
  • Margaret A. Palmer
    • 9
  • Paul Snelgrove
    • 10
  • David Strayer
    • 11
  • Jan Marcin Weslawski
    • 12
  1. 1.Marine Life Research Group, Scripps Institution of Oceanography, La Jolla, California 92093-0218, USAUS
  2. 2.University of Maryland Center for Environmental Studies, P.O. Box 775, Cambridge, Maryland 21613, USAUS
  3. 3.Fishery and Wildlife Biology, Colorado State University, Ft. Collins, Colorado 80523, USAUS
  4. 4.Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131, USAUS
  5. 5.Department of Invertebrate Zoology, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, SwedenSE
  6. 6.USDA Forest Service, Pacific Southwest Research Station, Institute of Pacific Islands Forestry, 1151 Punchbowl Street, Suite 323, Honolulu, Hawaii 96813, USAUS
  7. 7.University of Georgia Marine Institute, Sapelo Island, Georgia 31327, USAUS
  8. 8.Department of Entomology, Oregon State University, Corvallis, Oregon 97331, USAUS
  9. 9.Department of Biology, University of Maryland, College Park, Maryland 20742, USAUS
  10. 10.Fisheries Conservation Group, Memorial University of Newfoundland, P.O. Box 4290, St. Johns, Newfoundland, A1C 5R3, CanadaCA
  11. 11.Institute of Ecosystem Studies, P.O. Box AB, Millbrook, New York 12545, USA; andUS
  12. 12.Institute of Oceanology, Polish Academy of Sciences, Sopot 81-712, Powstancow, Warszawy 66, PolandPL

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