Combined use of rapid bioassessment protocols and sediment quality triad to assess stream quality

Physical, chemical and biological conditions at five stations on a small southeastern stream were evaluated using the Rapid Bioassessment Protocols (RBP) and the Sediment Quality Triad (SQT) to assess potential biological impacts of a municipal wastewater treatment facility (WWTF) on downstream resources. Physical habitat, benthic macroinvertebrates and fish assemblages were impaired at Stations 1 and 2 (upstream of the WWTF), suggesting that the degraded physical habitat was adversely impacting the fish and benthic populations. The SQT also demonstrated that Stations 1 and 2 were degraded, but the factors responsible for the impaired conditions were attributed to the elevated concentrations of polycylclic aromatic hydrocarbons (PAHs) and metals (Mn, Pb) in the sediments. The source of contaminants to the upper reaches of the stream appears to be storm-water runoff from the city center. Increased discharge and stabilized base flow contributed by the WWTF appeared to benefit the physically-altered stream system. Although the two assessment procedures demonstrated biological impairment at the upstream stations, the environmental factors identified as being responsible for the impairment were different: the RBP provided insight into contributions associated with the physical habitat and the SQT contributed information on contaminants and sediment quality. Both procedures are important in the identification of physical and chemical factors responsible for environmental impairment and together they provide information critical to the development of appropriate management options for mitigation.     

Assessing the Effects of Non-Point Source Pollution on American Samoa’s Coral Reef Communities

Surveys were completed on Tutuila Island, American Samoa, to characterize reef development and assess the impacts of non-point source pollution on adjacent coral reefs at six sites. Multivariate analyses of benthic and coral community data found similar modern reef development at three locations; Aoa, Alofau, and Leone. These sites are situated in isolated bays with gentle sloping foundations. Aoa reefs had the highest estimates of crustose coralline algae cover and coral species richness, while Leone and Alofau showed high abundances of macroalgae and Porites corals. Aoa has the largest reef flat between watershed discharge and the reef slope, and the lowest human population density. Masefau and Fagaalu have a different geomorphology consisting of cemented staghorn coral fragments and steep slopes, however, benthic and coral communities were not similar. Benthic data suggest Fagaalu is heavily impacted compared with all other sites. Reef communities were assessed as bio-criteria indicators for waterbody health, using the EPA aquatic life use support designations of (1) fully supportive, (2) partially supportive, and (3) non-supportive for aquatic life. All sites resulted in a partially supportive ranking except Fagaalu, which was non-supportive. The results of this rapid assessment based upon relative benthic community measures are less desirable than long-term dataset analyses from monitoring programs, however it fills an important role for regulatory agencies required to report annual waterbody assessments. Future monitoring sites should be established to increase the number of replicates within each geological and physical setting to allow for meaningful comparisons along a gradient of hypothesized pollution levels.     

Application Of Artificial Neural Network Models To Analyse The Relationships Between Gammarus pulex L. (Crustacea, Amphipoda) And River Characteristics

This study aimed at analysing the relationship between river characteristics and abundance of Gammarus pulex. To this end, four methods which can identify the relative contribution and/or the contribution profile of the input variables in neural networks describing the habitat preferences of this species were compared: (i) the ‘PaD‘ (‘Partial Derivatives‘) method consists of a calculation of the partial derivatives of the output in relation to the input variables; (ii) the ‘Weights‘method is a computation using the connection weights of the backpropagation Artificial Neural Networks; (iii) the ‘Perturb‘method analyses the effect of a perturbation of the input variables on the output variable; (iv) the ‘Profile‘ method is a successive variation of one input variable while the others are kept constant at a fixed set of values. The dataset consisted of 179 samples, collected over a three-year period in the Zwalm river basin in Flanders, Belgium. Twenty-four environmental variables as well as the log-transformed abundance of Gammarus pulex were used in this study. The different contribution methods gave similar results concerning the order of importance of the input variables. Moreover, the stability of the methods was confirmed by gradually removing variables. Only in a limited number of cases a shift in the relative importance of the remaining input variables could be observed. Nevertheless, differences in sensitivity and stability of the methods were detected, probably as a result of the different calculation procedures. In this respect, the ‘PaD‘method made a more severe discrimination between minor and major contributing environmental variables in comparison to the ‘Weights‘, ‘Profile‘ and ‘Perturb‘ methods. From an ecological point of view, the input variables ‘Ammonium‘ and to a smaller extent ‘COD‘, were selected by these methods as dominant river characteristics for the prediction of the abundance of Gammarus pulex in this study area.     

Thio arsenosugars in freshwater mussels from the Danube in Hungary

In contrast to the large body of data on naturally-occurring arsenic compounds in marine organisms, relatively little is known about arsenic speciation in freshwater biota. We report an investigation using HPLC-ICPMS into the arsenic compounds in five species of freshwater mussels collected from five sites from the Danube in Hungary. Total arsenic concentrations in the mussels ranged from 3.8-12.8 mg As kg(-1). The arsenic speciation patterns were broadly similar for mussels representing each of the five species and five sites, but quite different from those reported for marine mussels. The major extractable arsenicals were two oxo arsenosugars (glycerol sugar and phosphate sugar), and their thio analogues (thio glycerol sugar and thio phosphate sugar). Arsenobetaine, usually the major arsenical in marine organisms, was not a significant compound in the freshwater mussels and was detected in only three of the 11 samples. This is the first report of thio arsenosugars in freshwater biota and suggests that these compounds may be common and widespread naturally-occurring arsenicals.     

Adsorption of antimony(V) by floodplain soils, amorphous iron(III) hydroxide and humic acid

Antimony (Sb) emissions to the environment are increasing, and there is a dearth of knowledge regarding Sb fate and behaviour in natural systems. In particular, there is a lack of understanding of sorption of the oxidised Sb(V) species onto soils and soil phases. In this study sorption of Sb(V) by two organic rich soils with high levels of oxalate extractable Fe was examined over the pH range of 2.5-7. Furthermore, the sorption behaviour of Sb(V) was examined in two phases mimicking those dominant in the experimental soils, namely a solid humic acid and an amorphous Fe(OH)3, across the same pH range. Sorption of Sb by the soils and the humic acid fitted a Freundlich type isotherm, with the equation parameters reflecting changes in bonding affinity corresponding to pH changes. The soils sorbed >75% of the added Sb in all trials, and 80-100% at pH values less than approximately 6.5. The Fe(OH)3 retained >95% of the added Sb in all experiments. The humic acid sorbed up to 60% of the added Sb at acidic pH values, but sorption decreased to zero at higher pH values. Further adsorption studies are recommended, such as examining the effects of ion competition and changes in ionic strength.     

Evidence for life history changes in high-altitude populations of three perennial forbs

Relatively little is known about how the life histories of perennial forb species, and especially their lifetime patterns of growth, vary across environmental gradients. We used a post hoc approach (herb-chronology) to determine plant age and previous growth (width of successive annual rings in roots) in three species of perennial forb (two long-lived species [Penstemon venustus, Lupinus laxiflorus] and one short-lived [Rudbeckia occidentalis]) along a 1000-m altitudinal gradient in the Wallowa Mountains (northeast Oregon, USA). Plants from the highest altitude tended to be considerably older and produced up to five times as many flowering shoots as lowland plants. In addition, mean ring widths of high-altitude plants were about half those of lowland plants. In plants from low and intermediate altitudes, ring width either decreased linearly or varied inconsistently during the life of the plant. In contrast, ring widths of high-altitude plants increased at first and later decreased, resulting in curvilinear growth trajectories that were highly consistent among species. Together, these data for three ecologically distinct forb species provide evidence of a consistent shift toward more conservative and strongly constrained life histories at higher altitudes. More generally, the results indicate the possible importance of changes in selection pressures across strong environmental gradients on life history strategies within a single species.     

A reevaluation of the cultural eutrophication of Lake Okeechobee using multiproxy sediment records.

Lake Okeechobee, the hydrological lynchpin of the Everglades ecosystem, is the subject of an ambitious, multiagency restoration effort aimed at reducing phosphorus inputs and resulting algal blooms and impaired water clarity. This restoration is predicated on returning the lake to something closer to its predisturbance condition, but that goal has been challenged on the premise that the lake has always been eutrophic. The resolution of this debate and the appropriateness of the nutrient reduction goals thus depend on obtaining a reliable sediment record of past limnological conditions--the aim of this study. Because of the potential for severe sediment mixing from tropical storms, this investigation used multiple dating tools to examine the integrity of the sediment record and then analyzed proxies for nutrient enrichment, phytoplankton composition, and paleoproductivity. Sediment profiles for atmospheric pollutants, fertilizer contaminants, and radiocesium from three widely spaced cores showed good preservation of stratigraphic detail and coherence with the 210Pb chronologies. These results demonstrated that sediment stratigraphy is largely intact and retains a reliable record of limnological change. Geochemical proxies provide strong evidence of increased nutrient loading beginning ca. 1950. Concentrations of sediment P double, and N:P and C:N ratios drop, while those for N isotopes (delta15N) increase. At the same time, tracers of phosphate fertilizers (uranium, vanadium, and arsenic) rise. These changes are synchronous among cores and constitute a robust, internally consistent record of increasing water-column P. Biotic responses are manifested in higher concentrations and in changing composition of fossil algal pigments, including (1) large increases in the concentrations of chemically robust carotenoids, (2) corresponding decreases in the ratios of pigments from diatoms to chlorophyte and cyanobacterial algae, and (3) increases in UVR-photo-protective compounds indicating greater prevalence of surface algal blooms. This study provides strong evidence that Lake Okeechobee has experienced accelerated eutrophication linked with post-1950s land use changes in its watershed, a conclusion consistent with the nutrient reduction goals of the Lake Okeechobee Protection Program. The results contradict recent claims that the lake's trophic state has not changed over time, as well as the assertion that sediments of large shallow lakes cannot support a reliable chronology of past events.