Shell preference in a hermit crab: comparison between a matrix of paired comparisons and a multiple-alternative experiment

The preference of the hermit crab, Calcinus californiensis, among six species of shells, was tested by two different experiments. The first experiment used pair-wise trials, analyzing the preference by Chi-square tests using two different constructions of the null hypothesis. One hypothesis was based on a no-preference among shell species, the second on comparing the number of crabs changing for a particular shell species when two options were given versus the changing when no options were offered. The second experiment was a multiple-alternative test based on a rank ordering of the shell preference. This method has both statistical and resource-saving advantages over the traditional pair-wise comparisons. The sequence of shell preference was similarly independent of the procedure used. The preferred shell species are heavy and might be associated with hydrodynamic advantages and with the protection against predation. The shell preference matches with the pattern of shell occupancy indicating that the shell use in nature is determined by the crab’s preference. The information generated may be used for further research on shell preference as a methodological alternative.     

Who’s what? Prompt recognition of social status in crayfish

Crayfish are excellent model organisms to study the proximate mechanisms underlying the maintenance of dominance hierarchies in invertebrates. Our aim here was to investigate whether Procambarus clarkii males use social eavesdropping to discriminate dominant from subordinate crayfish. To this end, we conducted an experiment composed of a “passive” and an “active” phase. In the passive phase, “focal” individuals were allowed (treatment 1) or not (treatment 2) to see and smell two size-matched crayfish fighting while, in the subsequent active phase, they were allowed to freely interact with the fighting dyad. None of the recorded variables showed any significant difference between the two treatments, but, invariably, focal individuals were able to promptly discriminate dominant from subordinate crayfish. This study provides evidence that male crayfish recognize the social status of a conspecific without the need of direct or indirect experience with it and avoid dominants—and thus dangerous opponents—by means of a badge of status. A form of “winner and loser effects” could also contribute to the structuring of dominance/subordinate relationships. The implication of these results in understanding the maintenance of dominance hierarchies in invertebrates are discussed and compared with findings previously achieved in the context of mate choice by P. clarkii females, who do appear to use eavesdropping to identify dominants and subordinates.     

Are breaking waves,bores, surges and jumps the same flow?

The flow structure in the aerated region of the roller generated by breaking waves remains a great challenge to study, with large quantities of entrained air and turbulence interactions making it very difficult to investigate in details. A number of analogies were proposed between breaking waves in deep or shallow water, tidal bores and hydraulic jumps. Many numerical models used to simulate waves in the surf zone do not implicitly simulate the breaking process of the waves, but are required to parameterise the wave-breaking effects, thus relying on experimental data. Analogies are also assumed to quantify the roller dynamics and the energy dissipation. The scope of this paper is to review the different analogies proposed in the literature and to discuss current practices. A thorough survey is offered and a discussion is developed an aimed at improving the use of possible breaking proxies. The most recent data are revisited and scrutinised for the use of most advanced numerical models to educe the surf zone hydrodynamics. In particular, the roller dynamics and geometrical characteristics are discussed. An open discussion is proposed to explore the actual practices and propose perspectives based on the most appropriate analogy, namely the tidal bore.     

Achieving attainable outcomes from good science in an untidy world: case studies in land and air pollution

While scientific understanding of environmental issues develops through careful observation, experiment and modelling, the application of such advances in the day to day world is much less clean and tidy. Merseyside in northwest England has an industrial heritage from the earliest days of the industrial revolution. Indeed, the chemical industry was borne here. Land contamination issues are rife, as are problems with air quality. Through the examination of one case study for each topic, the practicalities of applied science are explored. An integrated, multidisciplinary response to pollution needs more than a scientific risk assessment. The needs of the various groups (from public to government) involved in the situations must be considered, as well as wider, relevant contexts (from history to European legislation), before a truly integrated response can be generated. However, no such situation exists in isolation and the introduction of environmental investigations and the exploration of suitable, integrated responses will alter the situation in unexpected ways, which must be considered carefully and incorporated in a rolling fashion to enable solutions to continue to be applicable and relevant to the problem being faced. This integrated approach has been tested over many years in Merseyside and found to be a robust approach to ever-changing problems that are well described by the management term, “wicked problems”.     

Cumulative and Residual Effects of Repeated Sewage Sludge Applications: Forage Productivity and Soil Quality Implications in South Florida,USA (9 pp)

Background, Aim and Scope The cow-calf (Bos taurus) industry in subtropical United States and other parts of the world depends almost totally on grazed pastures. Establishment of complete, uniform stand of bahiagrass (BG) in a short time period is important economically. Failure to obtain a good BG stand early means increased encroachment of weeds and the loss of not only the initial investment costs, but production and its cash value. Forage production often requires significant inputs of lime, N fertilizer, and less frequently of P and K fertilizers. Domestic sewage sludge or biosolids, composted urban plant debris, waste lime, phosphogypsum, and dredged materials are examples of materials that can be used for fertilizing and liming pastures. Perennial grass can be a good choice for repeated applications of sewage sludge. Although sewage sludge supply some essential plant nutrients and provide soil property-enhancing organic matter, land-application programs still generate some concerns because of possible health and environmental risks involved. The objectives of this study were to evaluate the cumulative and residual effects of repeated applications of sewage sludge on (i) bahiagrass (BG, Paspalum notatum Flügge) production over years with (1997–2000) and without (2001–2002) sewage sludge applications during a 5-yr period, and (ii) on nutrients status of soil that received annual application of sewage sludge from 1997 to 2000 compared with test values of soils in 2002 (with no sewage sludge application) in South Florida.Methods The field experiment was conducted at the University of Florida Agricultural Research and Education Center, Ona, FL (27o26’N, 82o55’W) on a Pomona fine sandy soil. With the exception of the control, BG plots received annual sewage sludge and chemical fertilizers applications to supply 90 or 180 kg total N ha–1 yr–1 from 1997 to 2000. Land application of sewage sludge and fertilizer ceased in 2001 season. In early April 1998, 1999, and 2000, plots were mowed to 5-cm stubble and treated with the respective N source amendments. The experimental design was three randomized complete blocks with nine N-source treatments: ammonium nitrate (AMN), slurry biosolids of pH 7 (SBS7), slurry biosolids of pH 11 (SBS11), lime-stabilized cake biosolids (CBS), each applied to supply 90 or 180 kg N ha–1, and a nonfertilized control (Control). Application rates of sewage sludge were calculated based on the concentration of total solids in materials as determined by the American Public Health Association SM 2540G method and N in solids. The actual amount of sewage sludge applications was based on the amount required to supply 90 and 180 kg N ha–1. Sewage sludge materials were weighed in buckets and uniformly applied to respective BG plots. Soil samples were collected in June 1997, June 1999, and in June 2002 from 27 treatment plots. In 1997 and 1999, soil samples were collected using a steel bucket type auger from the 0- to 20-, 20- to 40-, 40- to 60-, and 60- to 100-cm soil depths. Forage was harvested on 139, 203, 257, and 307 day of year (DOY) in 1998; 125, 202, 257, and 286 DOY in 1999; 179, 209, 270, and 301 DOY in 2000; and on 156 and 230 DOY in 2002 (no sewage sludge applications) to determine the residual effect of applied sewage sludge following repeated application. Forage yield and soils data were analyzed using analysis of variance (PROC ANOVA) procedures with year and treatment as the main plot and sub-plot, respectively. As a result of significant year effects on forage yield, data were reanalyzed annually (i.e., 1998, 1999, 2000, and 2002).Results and Discussion All sewage sludges used in this study were of class B in terms of USEPA’s pathogens and pollutant concentration limit. Pathogen and chemical composition of the class B sewage sludge that were used in the study were all in compliance with the USEPA guidelines. The liquid sludge (SBS11) had the lowest fecal coliform counts (0.2 x 106 CFU kg–1) while the cake sewage sludge (CBS) had the greatest coliform counts of 178 x 106 CFU kg–1. The fecal coliform counts for SBS7 was about 33 x 106 CFU kg–1. Average soil test values in June 2002 exhibited: i) decrease in TIN (NO3-N + NH4-N), TP, K, Ca, Mg, Mn, and Fe; and ii) slight increase in Zn and Cu when compared with the June 1997 soil test results. The overall decrease in soil test values in 2002 might be associated with nutrient cycling and plant consumption. Although the average BG forage yield in 2002 (2.3 ± 0.7 Mg ha–1) was slightly lower than in 2000 (3.5 ± 1.2 Mg ha–1), yield differences in 2002 between the control (1.2 + 0.2 Mg ha–1) and treated plots (2.3 ± 0.5 Mg ha–1 to 3.3 ± 0.6 Mg ha–1) were indicative of a positive residual effect of applied sewage sludge. This study has shown that excessive build up of plant nutrients may not occur in beef cattle pastures that repeatedly received sewage sludge while favoring long-term increased forage yield of BG. All sources of N (sewage sludge and AMN) gave better forage production than the unfertilized control during years with sewage sludge application (1997–2000) and also during years with no sewage sludge application (2001–2002). The favorable residual effects of applied sewage sludge in 2002 may have had received additional boost from the amount of rainfall in the area.Conclusions Repeated applications of sewage sludge indicate no harmful effects on soil quality and forage quality. Our results support our hypothesis that repeated land application of sewage sludge to supply 90 and 180 kg N ha–1 would not increase soil sorption for nutrients and trace metals. Results have indicated that the concentrations of soil TIN and TP declined by almost 50% in plots with different nitrogen sources from June 1997 to June 2002 suggesting that enrichment of nitrogen and phosphorus is insignificant. The concentrations of soil nitrogen and phosphorus in 2002 following repeated application of sewage sludge were far below the contamination risk in the environment. The residual effect of these sewage sludge over the long term can be especially significant in many areas of Florida where only 50% of the 1 million ha of BG pastures are given inorganic nitrogen yearly.Recommendation and Outlook Successive land application of sewage sludge for at least three years followed by no sewage sludge application for at least two years may well be a good practice economically because it will boost and/or maintain sustainable forage productivity and at the same time minimize probable accumulation of nutrients, especially trace metals. Consecutive applications of sewage sludge may result in build up of some trace metals in some other states with initial high metallic content, but in this study, no detrimental effects on soil chemical properties were detected. The possibilities for economically sound application strategies are encouraging, but more and additional research is required to find optimal timing and rates that minimizes negative impacts on soil quality in particular or the environment in general. For proper utilization of sewage sludge, knowledge of the sewage sludges’ composition, the crop receiving it, are absolutely crucial, so that satisfactory types and rates are applied in an environmentally safe manner. There is still much to be learned from this study and this investigation needs to continue to determine whether the agricultural and ecological objectives are satisfied over the longer term.     

The Role of a Salt Marsh Plant on Trace Metal Bioavailability in Sediments. Estimation By Different Chemical Approaches * (7 pp)

Goal, Scope and Background The presence or absence of vegetation can condition sediment characteristics. The main aim of this work was to investigate the influence of the sea rush Juncus maritimus on metal (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) availability to organisms living on or in estuarine sediments, from Douro River (NW Portugal), by comparing the characteristics and chemical behaviour of rhizosediments (collected within the plant assemblage) and those of sediment (collected around the plant). In order to evaluate whether and how sediment characteristics condition the role of plants on metal availability, sandy and muddy sediments colonised by J. maritimus were studied in parallel. Methods Metal availability was estimated by enzymatic digestion with pepsin (ED), which may provide an estimate of metal availability to organisms living at estuarine sediments. Nevertheless, since no consensus exists yet on the most suitable methodologies to estimate metal bioavailability in sediments, two more conventional approaches, BCR sequential extraction (SE) and AVS/SEM model, were also used, in parallel, and the information these approaches provided was compared with that provided by ED. Total-recoverable metal contents were determined by atomic absorption spectrophotometry after sediment digestion using a high-pressure microwave system. Results and Discussion Plants could concentrate metals around its roots and rhizomes. In addition, they were capable of oxidizing (release of oxygen by the roots) the anaerobic medium surrounding their roots in muddy sediment (reducing AVS). As sulphide oxidation renders metals (Cd, Cu, Ni, Pb and Zn) into more soluble forms, according to the AVS/SEM model, metals from muddy sites would be more available in rhizosediment than in sediment. The SE approach led to a similar conclusion. Nevertheless, the results provided by ED pointed at opposite conclusion, particularly for Cd and Zn, indicating less availability at rhizosediments than in the surrounding sediment. ED results were interpreted as a consequence of an enrichment of the rhizosediment in organic ligands exuded by the roots or liberated by dead plants. The effect of complexation of metals by organic compounds, which ED could not decompose/dissolve, seemed to overcome that caused by sediment oxidation. In general, a comparison of the information about metal availability by ED, SE, AVS/SEM, showed that it did not always match and in few cases it was even contradictory. Conclusion and Outlook Therefore, a thorough evaluation of the metal availability in sediments requires a combination of different chemical approaches, so as to take into consideration differences in ways of organism exposure (interstitial water and/or ingestion of sediment particles). - * The basis of this peer-reviewed paper is a presentation at the 9th FECS Conference on 'Chemistry and Environment', 29 August to 1 September 2004, Bordeaux, France.     

Phytoplankton Community and Chlorophyll a as Trophic State Indices of Lake Skadar (Montenegro,Balkan) (7 pp)

Background, Aims and Scope Phytoplankton, as a first step in trophic cascades of lakes, can be a good indicator of trophic states, considering that every environmental change affects this community and many species of this community are sensitive to changes, and that they response very quickly. In this study, we tried to assess and predict the trophic state of Lake Skadar according to phytoplankton data.Methods Water samples were collected using Ruttner sampling bottle. Temperature, dissolved oxygen, ph, conductivity and transparence were measured in situ using portable equipment. Nutrients and chlorophyll a were measured using standard spectrophotometric methods. A determination of phytoplankton species was performed using relevant keys and the counting of cells was performed using sedimentation methods.Results and Discussion The species composition of Lake Skadar revealed 95 taxa, with Chlorophyceae and Bacillariophyceae being represented best. According to an average chlorophyll a concentration of 5.9 µg/l, Lake Skadar belongs to the mesotrophic level of the trophic scale. Developed prediction equation for chlorophyll a revealed a good prediction (R2=0.71) and the parameter Secchi depth was primarily correlated with chlorophyll a concentration. Trophic state indices derived from chlorophyll a and transparency, were close together, but both were below the phosphorous index. Values of trophic state indices rank the Lake Skadar as being mesotrophic. This study also showed that indices of diversity based on phytoplankton are weak indicators of trophic status and that they can well characterize only differences between assemblages and associations. According to calculated saprobic indices (ranging from 1.5 to 2.15), Lake Skadar is on betamesosaprobic level of saprobity, which means that it is moderately polluted with organic compounds. Conclusions Total phosphorus is not the main limiting factor for the phytoplankton community in Lake Skadar. Disagreements between chlorophyll and the transparency index, on the one hand, and the total phosphorus index, on the other, suggest that the phytoplankton in Lake Skadar is probably limited by other factors than phosphorus, such as nitrogen, toxic substances or intense zooplankton grazing. According to the majority of investigated parameters and indices derived from phytoplankton data, Lake Skadar is mesotrophic, with tendencies toward eutrophic levels during the summer period. Recommendations and Outlook Long-term monitoring is required for a better estimation of state and the conditions of Lake Skadar. Further studies on factors influencing the phytoplankton community, especially zooplankton grazing and toxic substances, which were not included in this study, should be continued in the future to improve the efficiency of phytoplankton usage in estimating the ecological and trophic conditions of Lake Skadar.     

Rejection of emerging organic micropollutants in nanofiltration-reverse osmosis membrane applications.

The rejection of emerging trace organics by a variety of commercial reverse osmosis (RO), nanofiltration (NF), and ultra-low-pressure RO (ULPRO) membranes was investigated using TFC-HR, NF-90, NF-200, TFC-SR2, and XLE spiral membrane elements (Koch Membrane Systems, Wilmington, Massachusetts) to simulate operational conditions for drinking-water treatment and wastewater reclamation. In general, the presence of effluent organic matter (EfOM) improved the rejection of ionic organics by tight NF and RO membranes, as compared to a type-II water matrix (adjusted by ionic strength and hardness), likely as a result of a decreased negatively charged membrane surface. Rejection of ionic pharmaceutical residues and pesticides exceeded 95% by NF-90, XLE, and TFC-HR membranes and was above 89% for the NF-200 membrane. Hydrophobic nonionic compounds, such as bromoform and chloroform, exhibited a high initial rejection, as a result of both hydrophobic-hydrophobic solute-membrane interactions and steric exclusion, but rejection decreased significantly after 10 hours of operation because of partitioning of solutes through the membranes. This resulted in a partial removal of disinfection byproducts by the RO membrane TFC-HR. In a type-II water matrix, the effect of increasing feed water recoveries on rejection of hydrophilic ionic and nonionic compounds was compound-dependent and not consistent for different membranes. The presence of EfOM, however, could neutralize the effect of hydrodynamic operating condition on rejection performance. The ULPRO and tight NF membranes were operated at lower feed pressure, as compared to the TFC-HR, and provided a product water quality similar to a conventional RO membrane, regarding trace organics of interest.     

Using the analytical hierarchy process to assess the environmental vulnerabilities of basins in Taiwan

Every year, Taiwan endures typhoons and earthquakes; these natural hazards often induce landslides and debris flows. Therefore, watershed management strategies must consider the environmental vulnerabilities of local basins. Because many factors affect basin ecosystems, this study applied multiple criteria analysis and the analytical hierarchy process (AHP) to evaluate seven criteria in three phases (geographic phase, hydrologic phase, and societal phase). This study focused on five major basins in Taiwan: the Tan-Shui River Basin, the Ta-Chia River Basin, the Cho-Shui River Basin, the Tseng-Wen River Basin, and the Kao-Ping River Basin. The objectives were a comprehensive examination of the environmental characteristics of these basins and a comprehensive assessment of their environmental vulnerabilities. The results of a survey and AHP analysis showed that landslide area is the most important factor for basin environmental vulnerability. Of all these basins, the Cho-Shui River Basin in central Taiwan has the greatest environmental vulnerability.