title: Detecting shifts in ecosystem functioning: the decoupling of fundamental relationships with increased pollutant stress on sandflats.
abstract: In this study, we investigated the influence of low level contamination by copper, lead and zinc on the functioning of estuarine sandflat ecosystems by comparing the strength and variability of relationships between benthic macrofauna and fluxes (oxygen and nutrients) at three clean and three mildly contaminated sites. Specifically, as indicators of ecosystem functioning, we examined relationships between bivalve biomass, total benthic respiration and ammonium release, and ammonium uptake and benthic primary production. Furthermore, a small amount of organic matter was added to experimental plots at all sites (35 g/0.2 m²) to evaluate stress-on-stress responses relative to controls. Relationships were strongest at the clean sites (steepest slopes, highest r² values, lowest p-values) and weakest at the mildly contaminated sites and in organically enriched plots. Our results suggest that changes in ecosystem functioning may be occurring at mild (<ERL) levels of pollution that are unlikely to cause widespread mortality of macrofauna.
authors.affiliation: National Institute of Water and Atmospheric Research-NIWA, PO Box 11-115, Hillcrest, Hamilton 3216, New Zealand. d.lohrer@niwa.co.nz
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Lohrer
authors.forename: Michael
authors.initials: M
authors.lastname: Townsend
authors.forename: Iván F
authors.initials: IF
authors.lastname: Rodil
authors.forename: Judi E
authors.initials: JE
authors.lastname: Hewitt
authors.forename: Simon F
authors.initials: SF
authors.lastname: Thrush
mesh_terms: D000818:Animals; D003300:Copper / Q000032:analysis / Q000633:toxicity; D017753:Ecosystem; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D007854:Lead / Q000032:analysis / Q000633:toxicity; D008670:Metals / Q000032:analysis* / Q000633:toxicity; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000633:toxicity; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data; D015032:Zinc / Q000032:analysis / Q000633:toxicity
chemical_list: D008670:Metals; D014874:Water Pollutants, Chemical; D007854:Lead; D003300:Copper; D015032:Zinc