Nitrogen loading alters seagrass ecosystem structure and support of higher trophic levels

  • Published source details Deegan L.A., Wright A., Ayvazian S.G., Finn J.T., Golden H., Merson R.R. & Harrison J. (2002) Nitrogen loading alters seagrass ecosystem structure and support of higher trophic levels. Aquatic Conservation: Marine and Freshwater Ecosystems, 12, 193-212.


This study is summarised as evidence for the following.

Action Category

Restore biogenic habitats (other methods) - Restore seagrass beds/meadows

Action Link
Subtidal Benthic Invertebrate Conservation
  1. Restore biogenic habitats (other methods) - Restore seagrass beds/meadows

    A replicated, randomized, controlled, before-and-after study in 1990 of eight estuarine plots in Waquoit Bay, Massachusetts, North Atlantic Ocean, USA (Deegan et al. 2002) found that four months after restoration of common eelgrass Zostera marina beds by removing macroalgae, abundance of mobile invertebrates (decapods) had increased and was higher in restored than unrestored plots, but abundance of sessile invertebrates had not increased. Prior to restoration, all plots had similar abundance of decapods (restored: 24 vs unrestored: 27/m2) and sessile invertebrates (26,000 vs 22,000/m2). After four months, decapod abundance had increased and was higher in restored (82) than unrestored plots (35/m2), while sessile invertebrate abundance had decreased overall and remained similar across plots (restored: 5,000; unrestored: 8,000/m2). Following restoration, macroalgae biomass decreased in all plots (restored: from 96 to 20; unrestored: from 127 to 33 g/m2), and eelgrass abundance increased in all plots and was higher in restored plots (restored: from 3 to 19; unrestored: from 3 to 7 shoots/m2). Two 25 × 25 m experimental areas were selected, each with four 100 m2 plots. In May 1990, eelgrass was restored in one randomly selected area by manually removing macroalgae weekly. A second area was left unrestored. Plots were surveyed in April and monthly in June–September. Sessile invertebrates (>0.5 mm) were sampled in 3 plots/area using two cores (0.073 m2) and counted. Macroalgae were obtained from the cores and dry-weighed. Decapods (> 3 mm) were sampled using one 1 m2 throw net/plot and counted. Eelgrass shoots were counted along one 14 m2 diagonal transect/plot.

    (Summarised by: Anaëlle Lemasson)

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