Decision support systems optimising effluent release in sub tropical estuarine environment - An Australian case study

Gold Coast Water is responsible for the management of the water and wastewater assets of the City of the Gold Coast on Australia’s east coast. Treated wastewater is released at the Gold Coast Seaway on an outgoing tide in order for the plume to be dispersed before the tide changes and renters the Broadwater estuary. Rapid population growth over the past decade has placed increasing demands on the receiving waters for the release of the City’s effluent. The Seaway SmartRelease Project is designed to optimise the release of the effluent from the City’s main wastewater treatment plant in order to minimise the impact of the estuarine water quality and maximise the cost efficiency of pumping. In order to do this an optimisation study that involves water quality monitoring, numerical modelling and a web based decision support system was conducted. An intensive monitoring campaign provided information on water levels, currents, winds, waves, nutrients and bacterial levels within the Broadwater. These data were then used to calibrate and verify numerical models using the MIKE by DHI suite of software. The decision support system then collects continually measured data such as water levels, interacts with the WWTP SCADA system, runs the models in forecast mode and provides the optimal time window to release the required amount of effluent from the WWTP. The City’s increasing population means that the length of time available for releasing the water with minimal impact may be exceeded within 5 years. Optimising the release of the treated water through monitoring, modelling and a decision support system has been an effective way of demonstrating the limited environmental impact of the expected short term increase in effluent disposal procedures. (PDF contains 5 pages)

Seasonal ITCZ migration dynamically controls the location of the (sub)tropical Atlantic biogeochemical divide

Inorganic nitrogen depletion restricts productivity in much of the low-latitude oceans, generating a selective advantage for diazotrophic organisms capable of fixing atmospheric dinitrogen (N2). However, the abundance and activity of diazotrophs can in turn be controlled by the availability of other potentially limiting nutrients, including phosphorus (P) and iron (Fe). Here we present high-resolution data (∼0.3°) for dissolved iron, aluminum, and inorganic phosphorus that confirm the existence of a sharp north–south biogeochemical boundary in the surface nutrient concentrations of the (sub)tropical Atlantic Ocean. Combining satellite-based precipitation data with results from a previous study, we here demonstrate that wet deposition in the region of the intertropical convergence zone acts as the major dissolved iron source to surface waters. Moreover, corresponding observations of N2 fixation and the distribution of diazotrophic Trichodesmium spp. indicate that movement in the region of elevated dissolved iron as a result of the seasonal migration of the intertropical convergence zone drives a shift in the latitudinal distribution of diazotrophy and corresponding dissolved inorganic phosphorus depletion. These conclusions are consistent with the results of an idealized numerical model of the system. The boundary between the distinct biogeochemical systems of the (sub)tropical Atlantic thus appears to be defined by the diazotrophic response to spatial–temporal variability in external Fe inputs. Consequently, in addition to demonstrating a unique seasonal cycle forced by atmospheric nutrient inputs, we suggest that the underlying biogeochemical mechanisms would likely characterize the response of oligotrophic systems to altered environmental forcing over longer timescales.

Rare occurrence of a bigeye tuna Thunnus obesus in British waters, with notes on other occurrences of sub-tropical tunas

A freshly dead bigeye tuna Thunnus obesus was washed ashore near Burry Port, Wales (51 degrees 40' N; 4 degrees 15' W) in August, 2006. This is only the third occasion that the species has been observed in British waters, and is the largest and most northerly recorded specimen.

Simulating maize yield in sub-tropical conditions of southern Brazil using Glam model

The objective of this work was to evaluate the feasibility of simulating maize yield in a sub‑tropical region of southern Brazil using the general large area model (Glam). A 16‑year time series of daily weather data were used. The model was adjusted and tested as an alternative for simulating maize yield at small and large spatial scales. Simulated and observed grain yields were highly correlated (r above 0.8; p<0.01) at large scales (greater than 100,000 km2), with variable and mostly lower correlations (r from 0.65 to 0.87; p<0.1) at small spatial scales (lower than 10,000 km2). Large area models can contribute to monitoring or forecasting regional patterns of variability in maize production in the region, providing a basis for agricultural decision making, and Glam‑Maize is one of the alternatives.

Foraging by the omnivorous crab Pachygrapsus transversus affects the structure of assemblages on sub-tropical rocky shores

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of atypical pluviosity on phytoplankton assemblages in a stretch of a large sub-tropical river (Brazil)

This study aimed to evaluate the influence of alterations in pluviosity and ecological variables on microphytoplankton (> 20 mu m) structure (composition, richness, diversity, and abundance) and its biomass (chlorophyll-a), comparing different regions in a stretch of the low Igua double dagger u River and in some tributaries. Phytoplankton was sampled in 10 stations (5 in Igua double dagger u River and 5 in tributaries) during a dry period (April/2004) and an atypical rainy period (June/2004). The conductivity showed significant difference among the sampling points. Temperature, dissolved oxygen, pH, silicate, and nitrate showed significant differences between the dry and wet periods. Phytoplankton was composed of 149 taxa, and the most representative class was Chlorophyceae (71 taxa), followed by Bacillariophyceae (35 taxa), and Cyanophyceae (25 taxa). During the rainy period, stations of Igua double dagger u River showed higher taxa number and total density compared to the tributaries, but the values were similar in the dry period. Tributaries presented higher diversity and equitability in both periods. Except by two stations in Igua double dagger u River, the higher taxa number, densities and biomass occurred in the dry period, associated to low levels of suspended matter. The canonical correspondence analysis indicated the dominance of Bacillariophyceae and Chrysophyceae in the rainy period related to nitrate and suspended matter. Two other groups were observed in the dry period: one formed by Cyanophyceae, Dinophyceae, and Rhodophyceae, related to temperature and nitrite and other by Euglenophyceae and Chlorophyceae related to total phosphorus and silicate. The groups suggest adequate conditions of the physical, chemical and climatic factors to the establishment of the algae classes. Phytoplanktonic assemblages responded quickly to the environmental regional variations under strong influence of pluviosity, while in the dry period, homogeneity among stations and environmental variables was observed. The importance of climatic events is relevant in ecological studies in a temporal scale.

Feeding ecology of the Brazilian silverside Atherinella brasiliensis (Atherinopsidae) in a sub-tropical estuarine ecosystem

The feeding ecology of the Brazilian silverside, Atherinella brasiliensis, in a sub-tropical estuary of Brazil was investigated through the gut analysis of 1431 individuals. We described dietary composition and analysed seasonal, estuarine habitat, and body size variations in the diet; trophic level; feeding diversity; and gut fullness indices. Results reveal that A. brasiliensis is a typical, generalistic and opportunistic predator that makes use of a wide array of prey types (at least 89 different types), with zooplankton (mainly calanoids), diatoms, terrestrial insects, and plant detritus making up the bulk of the overall diet. The exotic calanoid Temora turbinata ranked as the primary prey. A wide feeding diversity (mean H` = 2.26), low trophic level (mean TROPH = 2.57), and high gut replenishment were persistent across seasons and habitats. Diet composition varied largely and significantly with respect to habitat, season, and body size. A closer assessment showed that habitat and season had a stronger effect on diet than fish size.

Feeding ecology of the American freshwater goby Ctenogobius shufeldti (Gobiidae, Perciformes) in a sub-tropical estuary

The feeding ecology of the American freshwater goby Ctenogobius shufeldti in a low salinity salt-marsh habitat in the Paranagua Bay estuarine complex (Brazil) was assessed through the gut analysis of 632 individuals. The effects of a set of abiotic factors (type of sediment, salinity, temperature and estuarine reach), season and body size on dietary composition were analysed. Seasonal and size-related changes in feeding strategy, feeding intensity and trophic level were assessed. The effects of gape and body size on prey size use were also analysed. The results showed that C. shufeldti is a typical omnivorous, generalized benthic predator of low trophic levels throughout the seasons and size classes, feeding on 56 dietary items; tanaids, chlorophyte algae, ostracods, gastropods, detritus and benthic diatoms made up the bulk of its diet. The tanaid Kalliapseudes schubarti was the main prey item in both numerical and volumetric terms. The gut fullness was persistently high across the seasons. As expected for a typical generalized, opportunistic omnivorous feeder: (1) seasonal and spatial-temporal variability of abiotic factors had a significant effect on diet structure, (2) season accounted for most of the dietary variation and (3) diet composition and the size of prey consumed did not vary across the size classes.

The influence of tropical climates on european constitutions : to which is added tropical hygiene or the preservation of health in all hot climates /

Mode of access: Internet.

The Application of Geographic Information Systems to climate change & land evaluation : a study of the effects of climate change upon crop productivity in a sub-tropical environment

This research investigates the contribution that Geographic Information Systems (GIS) can make to the land suitability process used to determine the effects of a climate change scenario. The research is intended to redress the severe under representation of Developing countries within the literature examining the impacts of climatic change upon crop productivity. The methodology adopts some of the Intergovernmental Panel on Climate Change (IPCC) estimates for regional climate variations, based upon General Circulation Model predictions (GCMs) and applies them to a baseline climate for Bangladesh. Utilising the United Nations Food & Agricultural Organisation's Agro-ecological Zones land suitability methodology and crop yield model, the effects of the scenario upon agricultural productivity on 14 crops are determined. A Geographic Information System (IDRISI) is adopted in order to facilitate the methodology, in conjunction with a specially designed spreadsheet, used to determine the yield and suitability rating for each crop. A simple optimisation routine using the GIS is incorporated to provide an indication of the 'maximum theoretical' yield available to the country, should the most calorifically significant crops be cultivated on each land unit both before and after the climate change scenario. This routine will provide an estimate of the theoretical population supporting capacity of the country, both now and in the future, to assist with planning strategies and research. The research evaluates the utility of this alternative GIS based methodology for the land evaluation process and determines the relative changes in crop yields that may result from changes in temperature, photosynthesis and flooding hazard frequency. In summary, the combination of a GIS and a spreadsheet was successful, the yield prediction model indicates that the application of the climate change scenario will have a deleterious effect upon the yields of the study crops. Any yield reductions will have severe implications for agricultural practices. The optimisation routine suggests that the 'theoretical maximum' population supporting capacity is well in excess of current and future population figures. If this agricultural potential could be realised however, it may provide some amelioration from the effects of climate change.

Climatic Controls on Phytoplankton Biomass in a Sub-tropical Estuary, Florida Bay, USA

The extraction of climatic signals from time series of biogeochemical data is further complicated in estuarine regions because of the dynamic interaction of land, ocean, and atmosphere. We explored the behavior of potential global and regional climatic stressors to isolate specific shifts or trends, which could have a forcing role on the behavior of biogeochemical descriptors of water quality and phytoplankton biomass from Florida Bay, as an example of a sub-tropical estuary. We performed statistical analysis and subdivided the bay into six zones having unique biogeochemical characteristics. Significant shifts in the drivers were identified in all the chlorophyll a time series. Chlorophyll a concentrations closely follow global forcing and display a generalized declining trend on which seasonal oscillations are superimposed, and it is only interrupted by events of sudden increase triggered by storms which are followed by a relatively rapid return to pre-event conditions trailing again the long-term trend.

Forest Resource Islands in a Sub-tropical Marsh: Soil–Site Relationships in Everglades Hardwood Hammocks

Spatial heterogeneity in soils is often characterized by the presence of resource-enriched patches ranging in size from a single shrub to wooded thickets. If the patches persist long enough, the primary constraint on production may transition from one limiting environmental factor to another. Tree islands that are scattered throughout the Florida Everglades basin comprise nutrient-enriched patches, or resource islands, in P-limited oligotrophic marshes. We used principal component analysis and multiple regressions to characterize the belowground environment (soil, hydrology) of one type of tree island, hardwood hammocks, and examined its relationship with the three structural variables (basal area, biomass, and canopy height) indicative of site productivity. Hardwood hammocks in the southern Everglades grow on two distinct soil types. The first, consisting of shallow, organic, relatively low-P soils, is common in the seasonally flooded Marl Prairie landscape. In contrast, hammocks on islands embedded in long hydroperiod marsh have deeper, alkaline, mineral soils with extremely high P concentrations. However, this edaphic variation does not translate simply into differences in forest structure and production. Relative water depth was unrelated to all measures of forest structure and so was soil P, but the non-carbonate component of the mineral soil fraction exhibited a strong positive relationship with canopy height. The development of P-enriched forest resource islands in the Everglades marsh is accompanied by the buildup of a mineral soil; however, limitations on growth in mature islands appear to differ substantively from those that dominate incipient stages in the transformation from marsh to forest. Key words: resource island; tree