Survival of crucian carp,Carassius carassius,exposed to a high low-molecular weight inorganic aluminium challenge

Crucian carp were exposed to three combinations of pH and inorganic aluminium concentrations for 25 days. Mortality, plasma chloride and haematocrit, and gill aluminium content were investigated. No mortality was observed in any of the three exposures. Crucian carp survived acidic Al-rich water (pH 5.17) with a high concentration of low-molecular weight inorganic Al species (242 µgl^–1) for 25 days. These fish had lowered plasma chloride levels and high amounts of aluminium on their gills compared to fish exposed to acidic Al-poor water (pH 5.16 and 12 µgl^–1 Al_i) and control water (pH 6.29 and 4 µgl^–1 Al_i). Haematocrit was the same in all three exposures. Because aluminium was not acutely toxic to the anoxia tolerant crucian carp, the present results give support to the hypothesis that Al polymerization with subsequent hypoxia is of high importance for the mechanism of acute Al toxicity to fish.     

Collaborative Management of Public Rangeland in Wyoming: Lessons in Co-Management

Collaborative processes are gaining acceptance as a means to integrate different values and interests in the management of natural resources. This paper examines one form of collaboration, Coordinated Resource Management (CRM), as it is being applied to public rangeland management in Wyoming. The study included personal and telephone interviews of participants in CRM groups, document review, and personal observation to understand how the process works to achieve consensus among diverse stakeholders. Groups used five mechanisms to deal with different values and interests in their processes: (1) elimination of unnecessary or “overlay” conflict; (2) limitation of values and visions considered; (3) use of broad goals to guide actions; (4) casting value differences as disagreement over facts; (5) a search for and faith in win-win solutions. These mechanisms vary in their usefulness for achieving co-management ideals. Where interests or values have come into open conflict, as in some conflict-resolution groups, CRM has had limited success. This paper suggests that successful co-management requires more than power-sharing structures. We have yet to develop highly effective processes that can work with conflicting interests. It is also argued that struggles among various interests for greater recognition (and hence power) will continue to undergird the power-sharing collaborative and co-management processes.     

Organic Matter Sources Supporting Lower Food Web Production in the Tidal Freshwater Portion of the York River Estuary, Virginia

The Mattaponi River is part of the York River estuary in Chesapeake Bay. Our objective was to identify the organic matter (OM) sources fueling the lower food web in the tidal freshwater and oligohaline portions of the Mattaponi using the stable isotopes of carbon (C) and nitrogen (N). Over 3 years (2002–2004), we measured zooplankton densities and C and N stable isotope ratios during the spring zooplankton bloom. The river was characterized by a May–June zooplankton bloom numerically dominated by the calanoid copepod Eurytemora affinis and cladocera Bosmina freyi. Cluster analysis of the stable isotope data identified four distinct signatures within the lower food web: freshwater riverine, brackish water, benthic, and terrestrial. The stable isotope signatures of pelagic zooplankton, including E. affinis and B. freyi, were consistent with reliance on a mix of autochthonous and allochthonous OM, including OM derived from vascular plants and humic-rich sediments, whereas macroinvertebrates consistently utilized allochthonous OM. Based on a dual-isotope mixing model, reliance on autochthonous OM by pelagic zooplankton ranged from 20% to 95% of production, declining exponentially with increasing river discharge. The results imply that discharge plays an important role in regulating the energy sources utilized by pelagic zooplankton in the upper estuary. We hypothesize that this is so because during high discharge, particulate organic C loading to the upper estuary increased and phytoplankton biomass decreased, thereby decreasing phytoplankton availability to the food web.     

Numerical Modeling of Unsaturated Flow in Wastewater Soil Absorption Systems

It is common practice in the United States to use wastewater soil absorption systems (WSAS) to treat domestic wastewater. WSAS are expected to provide efficient, long-term removal of wastewater contaminants prior to ground water recharge. Soil clogging at the infiltrative surface of WSAS occurs due to the accumulation of suspended solids, organic matter, and chemical precipitates during continued wastewater infiltration. This clogging zone (CZ) creates an impedance to flow, restricting the hydraulic conductivity and rate of infiltration. A certain degree of clogging may improve the treatment of wastewater by enhancing purification processes, in part because unsaturated flow is induced and residence times are significantly increased. However, if clogging becomes excessive, the wastewater pond height at the infiltrative surface can rise to a level where system failure occurs. The numerical model HYDRUS-2D is used to simulate unsaturated flow within WSAS to better understand the effect of CZs on unsaturated flow behavior and hydraulic retention times in sandy and silty soil. The simulations indicate that sand-based WSAS with mature CZs are characterized by a more widely distributed flow regime and longer hydraulic retention times. The impact of clogging on water flow within the silt is not as substantial. For sand, increasing the hydraulic resistance of the CZ by a factor of three to four requires an increase in the pond height by as much as a factor of five to achieve the same wastewater loading. Because the degree of CZ resistance directly influences the pond height within a system, understanding the influence of the CZ on flow regimes in WSAS is critical in optimizing system design to achieve the desired pollutant-treatment efficiency and to prolong system life.     

Temperature dependence of CO2 fugacity in seawater

Ideally, the correction of the measured CO₂ fugacity (fCO₂) at temperature T_m to fCO₂ at the in-situ temperature T_in should be made by using at least 2 known parameters (pH-A_T, C_T-A_T,…) and the reliable constants for carbonic acid. In practice however, a measured CO₂ property pair is not always available. When fCO₂ is measured alone, one must make an estimate of the effect of temperature on seawater fCO₂ from the accurate knowledge of seawater salinity and temperature and the approximate knowledge of the carbonate parameters. In this paper we present an empirical relationship that can be used to estimate the effect of temperature on fCO₂. The equation is of the form:

ƒCO_2[t] − ƒCO_2[20]=A + Bt + Ct² + Dt³ + Et⁴

where fCO_2[t] and fCO_2[20] represent fCO₂ at temperatures t°C and 20°C, respectively; the parameters A, B, etc. are functions of the ratio X = C_T/A_T:

E = e₀ + e₁X + e₂X²ln(X) + e₃exp(X) + e₄/ln(X)

where the parameters a_i, b_i, etc. are functions of salinity.The 25-parameter equation is fitted by the values of fCO₂ calculated using the constants of Goyet and Poisson (1989), when X varies from 0.8 to 1.0, t varies from −1dgC to 40°C, and S varies from 30 to 40. For T_m - T_in within ± 10°C, direct measurements of fCO₂ as a function of the temperature (from −I to 30°C verify this equation within less than ±5 μatm.     

Low-temperature incubation of walleye pollock (Theragra chalcogramma) eggs from the southeast Bering Sea shelf and Shelikof Strait, Gulf of Alaska

To determine the effect of low water temperature on development, walleye pollock (Theragra chalcogramma) eggs from the Bering Sea were reared at −0.6°C, 0.4°C, 2.0°C, and 3.8°C. One group of eggs was reared at 3.9°C under a diel light cycle (14 h light, 10 h dark) to observe the effect of light on development and hatching. Development was normal for all temperatures except −0.6°C; abnormal development of the tail and lack of development of eyes occurred in some embryos. Time to 50% hatch was 820, 620, and 424 h at 0.4°C, 2.0°C, and 3.8°C. Eggs incubated in diel light at 3.9°C developed at the same rate as eggs incubated in constant dark at 3.8°C, but required an additional 72 h to reach 50% hatch. A piece-wise regression model was generated to predict egg age for incubation temperatures of −0.6°C to 3.8°C. For temperatures recorded in the southeastern Bering Sea 1995–1998, the model predicted incubation periods for walleye pollock eggs that varied by 13 days between the warmest and coldest years.Walleye pollock eggs from Shelikof Strait, Alaska, were incubated at 0.2°C, 1.8°C, and 2.8°C. Development was normal for all temperatures. A piece-wise regression model (as above) was generated for incubation temperatures 0.2–2.8°C. When the regression models were compared, Bering Sea eggs (1.4–1.7 mm in diameter), required more time for development prior to hatch than Shelikof Strait eggs (1.2–1.3 mm in diameter) at 1.8°C and 2.8°C. However, for temperatures 0.2–2.0°C, Bering Sea walleye pollock began hatching earlier and at a developmentally younger age than Shelikof Strait walleye pollock.     

Soil moisture response to white ash mortality following emerald ash borer invasion

Emerald ash borer (EAB) (Agrilus planipennis Fairmaire), an invasive forest insect first identified in southeastern Michigan in 2002, is established in at least 32 US states and three Canadian provinces. Ash (Fraxinus spp.) mortality rates in some forested areas exceed 90%, but to date, little is known about the potential effects of EAB-caused ash mortality on hydrological processes. More broadly, there is a need for information on the timing and magnitude of soil moisture response to species-specific mortality of overstory vegetation in deciduous forest systems. Soil moisture was examined in 28 forested sites where 0–100% of the white ash basal area (Fraxinus americana L.) was killed by EAB. Synoptic measurements of near-surface (0–6 cm depth) soil moisture were collected from 112 plots (18 m radius) within the sites. Three plots were also instrumented with soil moisture sensors at 10 and 25 cm depth to log hourly measurements from May to October. Synoptic data showing white ash mortality and soil moisture were positively correlated in the 34 plots with ≥?5% mortality (by total basal area). In the intensively monitored plots, volumetric soil moisture declined from 37 to 16% between July and September where white ash mortality was low (0.6% of basal area killed), but remained near field capacity (~?30%) throughout the monitoring period in the high mortality plot (8.6% of basal area killed), meriting further investigation to assess effects of white ash mortality on evapotranspiration and soil moisture dynamics in heterogeneous upland forests. Altered soil moisture may have implications for regrowth dynamics, infiltration/runoff partitioning, and nutrient cycling, but additional study to quantify the extent and duration of EAB-related ash mortality on hydrology at the plot and watershed scale is necessary.     

Local variability in the timing and intensity of tropical dry forest deciduousness is explained by differences in forest stand age

Tropical Dry Forest deciduousness is a behavioral response to climate conditions that determines ecosystem-level carbon uptake, energy flux, and habitat conditions. It is regulated by factors related to stand age, and landscape scale variability in deciduous phenology may affect ecosystem functioning in forests throughout the tropics. This study determines whether observed phenological differences are explainable by forest age in the southern Yucatán Peninsula in Mexico, where forest clearing for shifting cultivation has created a mosaic of forest stands of varying age. Matched-pair statistical tests compare neighboring forest pixels of different age class (12–22 years versus 22+ years) and detect significant differences in Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI)-derived metrics related to the timing and intensity of deciduousness during three dry seasons (2008–2011). In all seasons, young forests exhibit significantly more intense deciduousness, measured as total seasonal change of EVI normalized by annual maximum EVI (p < 0.001), and larger normalized EVI change during successive dry season months relative to start-of-dry-season EVI (p < 0.001), than neighboring older forests subject to similar environmental conditions.     

The final fifth: autobiography, reflexivity and interpretation in cross-cultural research

Summary This paper addresses concerns about the complexities of cross-cultural field- work, and the importance of the positionality of researchers and translators in the research process. These concerns build upon debates within the social sciences about autobiography, reflexivity and the research process, as well as notions of validity, reliability and 'truth'. The paper re-examines these debates in the context of cross-cultural research by focusing on praxis—actual experiences in the field.     

Pre-eruptive physical conditions of El Reventador volcano (Ecuador) inferred from the petrology of the 2002 and 2004–05 eruptions

A petrological study of the eruptive products of El Reventador allowed us to infer the magmatic processes related to the 2002 and 2004–05 eruptions of this andesitic stratovolcano. On November 3, 2002, El Reventador experienced a highly explosive event, which was followed by emplacement of two lava flows in November–December 2002. Silica contents range from 62 to 58 wt.% SiO₂ for the November 3 pyroclastic deposits to 58–56 and 54–53 wt.% SiO₂ for the successive lava flows. In November 2004 eruptive activity resumed supplying four new lava flows (56–54 wt.% SiO₂) between November 2004 and August 2005.