The Use of Urban Wastewater for the Colorado River Delta Restoration

AbstractThe environmental changes due to the Colorado River damming, have affected the ecological functioning of the nursery river delta and consequently the population of fishermen that live of the natural marine resources of the upper Gulf of California. We propose the use of urban wastewaters as a source of nutrients to fertilize the estuary, increase the primary productivity and therefore increase the population size of the estuarine dependent species, which are important for the fisheries in the region. In this way, we could partially restore the delta's ecological functioning and thus solve environmental, social, and economic problems. With a wastewater flow of 800 l·s-1 from “Las Arenitas” treatment plant, we could increase the primary organic productivity and ~1000 metric tons (mT) of shrimp landings of the region. These calculations are just for one fishery, but in a magnitude that could also increase in others

Quantifying the effects of climate change and water abstraction on a population of barramundi (Lates calcarifer), a diadromous estuarine finfish

Many aquatic species are linked to environmental drivers such as temperature and salinity through processes such as spawning, recruitment and growth. Information is needed on how fished species may respond to altered environmental drivers under climate change so that adaptive management strategies can be developed. Barramundi (Lates calcarifer) is a highly prized species of the Indo-West Pacific, whose recruitment and growth is driven by river discharge. We developed a monthly age- and length-structured population model for barramundi. Monte Carlo Markov Chain simulations were used to explore the population's response to altered river discharges under modelled total licenced water abstraction and projected climate change, derived and downscaled from Global Climate Model A1FI. Mean values of exploitable biomass, annual catch, maximum sustainable yield and spawning stock size were significantly reduced under scenarios where river discharge was reduced; despite including uncertainty. These results suggest that the upstream use of water resources and climate change have potential to significantly reduce downstream barramundi stock sizes and harvests and may undermine the inherent resilience of estuarine-dependent fisheries. © 2012 CSIRO

The effect of El Niño on the nutrients and total organic cabon of a coastal lagoon of northwestern Baja California

Nutrients (NO3 + NO2, PO4) and total organic carbon (TOC) from Estero de Punta Banda, a coastal lagoon of Baja California (Mexico), were studied during the 1992–93 El Niño. Samples were collected at four sites distributed along the main channel of the lagoon, during four different tidal stages. According to reports in the literature, this coastal lagoon behaves as an antiestuary most of the time, with salinity increasing significantly from the mouth inwards. Greater input of fresh water due to a larger rainfall, well above the annual mean (393 mm), caused the Estero to behave as an estuary, with salinity values of <25 and with an increase of NO3 + NO2, PO4 and TOC. PO4 values fluctuated between 0.5 and 3.5 µM, and those of TOC between 2.3 and 9.8 mg L–1, with a clear tendency to increase from the entrance to the interior of the lagoon. NO3 values fluctuated between 0.2 and 2.3 µM in September 1992, and between 1.4 and 6.8 µM in March 1993, also with a clear tendency to increase towards the lagoon´ s interior in the latter case. PO4 had a significant negative correlation (P < 0.05) with salinity in March 1993. The change of this lagoon from antiestuary to estuary for long periods, of almost up to one year, is related to meteorological phenomena influenced by large scale events like El Niño