title: Deposit-feeding sea cucumbers enhance mineralization and nutrient cycling in organically-enriched coastal sediments.
abstract: BACKGROUND
  Bioturbators affect multiple biogeochemical interactions and have been suggested as suitable candidates to mitigate organic matter loading in marine sediments. However, predicting the effects of bioturbators at an ecosystem level can be difficult due to their complex positive and negative interactions with the microbial community.
  
  
  RESULTS
  We quantified the effects of deposit-feeding sea cucumbers on benthic algal biomass (microphytobenthos, MPB), bacterial abundance, and the sediment-seawater exchange of dissolved oxygen and nutrients. The sea cucumbers increased the efflux of inorganic nitrogen (ammonium, NH(4) (+)) from organically enriched sediments, which stimulated algal productivity. Grazing by the sea cucumbers on MPB (evidenced by pheopigments), however, caused a net negative effect on primary producer biomass and total oxygen production. Further, there was an increased abundance of bacteria in sediment with sea cucumbers, suggesting facilitation. The sea cucumbers increased the ratio of oxygen consumption to production in surface sediment by shifting the microbial balance from producers to decomposers. This shift explains the increased efflux of inorganic nitrogen and concordant reduction in organic matter content in sediment with bioturbators.
  
  
  CONCLUSIONS
  Our study demonstrates the functional role and potential of sea cucumbers to ameliorate some of the adverse effects of organic matter enrichment in coastal ecosystems.
authors.affiliation: Department of Marine Science, University of Otago, Dunedin, New Zealand.
authors.forename: Thomas
authors.initials: T
authors.lastname: Mactavish
authors.forename: Jeanie
authors.initials: J
authors.lastname: Stenton-Dozey
authors.forename: Kay
authors.initials: K
authors.lastname: Vopel
authors.forename: Candida
authors.initials: C
authors.lastname: Savage
mesh_terms: D000641:Ammonia / Q000737:chemistry; D000818:Animals; D018533:Biomass; D017753:Ecosystem; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology*; D009566:Nitrates / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry; D012616:Sea Cucumbers / Q000254:growth & development*; D012623:Seawater / Q000737:chemistry / Q000382:microbiology
chemical_list: D009566:Nitrates; D010758:Phosphorus; D000641:Ammonia; D010100:Oxygen