Effects of Community Structure on the Seagrass Thalassia testudinum

Craig D. Rose, Clinton J. Dawes

Research output: Contribution to journalArticlepeer-review

Abstract

The influence of community structure on the seagrass Thalassia testudinum was studied in 3 distinct communities: low and high density monocultures, and patches intermixed with Halodule wrightii , in Cockroach Bay, Tampa, Florida. T. testudinum shoot-specific leaf mass and growth were significantly higher in low density monocultures, and both variables were negatively correlated with short-shoot density. Intraspecific, competition-density effects in high-density seagrass beds may be responsible for the relatively lower shoot-specific leaf mass and growth rates, possibly due to the reduction of available light from dense leaf canopies. These observations are supported by significantly higher T. testudinum leaf C:N and delta(13)C in low density monocultures, which suggests that high rates of growth are coupled with high C and N demands and reduced discrimination of C. Lower T. testudinum shoot-specific leaf mass and growth in mixed species patches may be partially explained by interspecific competition with H. wrightii ; however, the exact mechanisms by which these species interact were not discovered. Differences among communities in sediment NH4+ and PO43-, and T. testudinum leaf C:N:P and delta(15)N suggest that community structure in seagrass meadows plays an important role in sediment nutrient dynamics and, potentially, nutrient availability. However, low leaf C:N and C:P ratios suggest that nutrients are not limiting in this system. This study shows that intraspecific competition, and to a lesser degree, interspecific interactions with H. wrightii , are important determinants of T. testudinum productivity and, potentially, seagrass community structure in Cockroach Bay.

Original languageAmerican English
JournalMarine Ecology - Progress Series
Volume184
DOIs
StatePublished - Jul 28 1999

Keywords

  • seagrass
  • Thalassia testudinum
  • heterogeneous
  • community structure
  • intraspecific competition
  • nutrient availability

Disciplines

  • Medical Sciences
  • Medicine and Health Sciences

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