Asunto(s)
Clorofila/química , Arrecifes de Coral , Monitoreo del Ambiente/métodos , Eutrofización , Animales , Clorofila ARESUMEN
Long-term monitoring data show that hard coral cover on the Great Barrier Reef (GBR) has reduced by >70 % over the past century. Although authorities and many marine scientists were in denial for many years, it is now widely accepted that this reduction is largely attributable to the chronic state of eutrophication that exists throughout most of the GBR. Some reefs in the far northern GBR where the annual mean chlorophyll a (Chl a) is in the lower range of the proposed Eutrophication Threshold Concentration for Chl a (~0.2-0.3 mg m⻳) show little or no evidence of degradation over the past century. However, the available evidence suggests that coral diseases and the crown-of-thorns starfish will proliferate in such waters and hence the mandated eutrophication Trigger values for Chl a (~0.4-0.45 mg m⻳) will need to be decreased to ~0.2 mg m⻳ for sustaining coral reef communities.
Asunto(s)
Clorofila/química , Arrecifes de Coral , Monitoreo del Ambiente/métodos , Eutrofización , Animales , Antozoos , Australia , Clorofila A , Océano Pacífico , Fósforo , Factores de Tiempo , Contaminación del AguaRESUMEN
The results from the multimillion dollar Enrichment of Nutrients on Coral Reefs Experiment (ENCORE) on One Tree Island Reef (OTIR) suggest that increased nutrient loads to coral reefs will have little or no effect on the algal growth rates and, hence, on the associated effects that increased algal growth might have on the functioning and stability of coral reefs. However, a comparison of the concentrations of nutrients within the OTIR lagoon with the proposed nutrient threshold concentrations (NTC) for coral reefs suggests that all sites, including the control sites, were saturated with nutrients during ENCORE, and, hence, one would not expect to get any differences between treatments in the algal-growth related measurements. Thus, ENCORE results provide strong support for the proposed NTCs and support the ecological principle that algal productivity and, consequently, the functioning of coral reefs are sensitive to small changes in the background concentrations of nutrients. The principal conclusion of ENCORE, namely that the addition of nutrients did not cause the "pristine" OTIR to convert from coral communities to algal dominated reefs, is contrary to the fact that there was prolific macroalgal growth on the walls and crests of the experimental microatolls by the end of ENCORE.
Asunto(s)
Cnidarios/efectos de los fármacos , Modelos Teóricos , Nitrógeno/farmacología , Fósforo/farmacología , Contaminantes Químicos del Agua/farmacología , Animales , Bivalvos/efectos de los fármacos , Bivalvos/metabolismo , Cnidarios/metabolismo , Crustáceos/efectos de los fármacos , Crustáceos/metabolismo , Eucariontes/efectos de los fármacos , Eucariontes/metabolismo , Peces , Biología Marina , Nitrógeno/farmacocinética , Fósforo/farmacocinética , Fitoplancton/efectos de los fármacos , Fitoplancton/metabolismo , Dinámica Poblacional , Queensland , Contaminantes Químicos del Agua/farmacocinéticaRESUMEN
Active filters, which facilitate phosphorus (P) removal via precipitation and/or adsorption, offer a promising 'appropriate technology' for upgrading small wastewater treatment systems. Research on active filters for P removal using steel slag material has been conducted in laboratories across the world, however, field experiments have been limited and long-term data is practically non-existent. This paper presents a decade of experience on P removal by active slag filters at a full-scale treatment plant. During 1993-1994 the filter removed 77% of the total phosphorus (TP), and over the first 5 years of the filter's operation it reduced the mean effluent TP concentration to 2.3 mgl(-1). However during the sixth year of operation P removal was significantly reduced. Over the 11 years of monitoring, 22.4 tonnes of TP was removed by the filter, 19.7 tonnes of this in the first 5-year period. It was determined that the slag material maintained its maximum removal potential until reaching a P-retention ratio of 1.23 kg TP per tonne of slag. This paper provides the first long-term field data for slag filters, and shows that they can provide P removal for a half a decade before filter replacement/rejuvenation is required.