Metabolic disposition of lactate in the horseshoe crab Limulus polyphemus and the stone crab Menippe mercenaria

The metabolism of ¹⁴C-labelled lactate was investigated in the horseshoe crab Limulus polyphemus and the stone crab Menippe mercenaria. When a bolus of (¹⁴C-U)-D-lactate was injected into L. polyphemus, there was substantial release pf ¹⁴CO₂ into the medium. In the case of M. mercenaria, ¹⁴CO₂ release was also observed after injection of (¹⁴C-U)-L-lactate into experimental individuals. Analysis of the distribution of radioactivity in whole body extracts of both species revealed easily detectable amounts of radioactivity in the glycogen fraction, although the bulk of the radioactivity was in the cation, anion/neutral and CO₂ fractions. To investigate the metabolism of lactate further, ¹⁴C-labelled lactate was injected into large individuals of L. polyphemus and M. mercenaria, and the distribution of radioactivity was determined in the hemolymph, muscle and hepatopancreas. Utilization of (¹⁴C-U)-D-lactate by L. polyphemus resulted in the accumulation of significant amounts of labelled glucose in all three body compartments as well as the production of labelled glycogen in the telson levator muscle and hepatopancreas. Utilization of (¹⁴C-U)-L-lactate resulted in a similar pattern of glucose and glycogen labelling in the hemolymph, cheliped muscle and hepatopancreas of M. mercenaria. These studies demonstrate that both L. polyphemus and M. mercenaria have the capacity for glyco- and gluconeogenesis using lactate as the substrate.     

The influence of pH on the degradation of phenol and chlorophenols by potassium ferrate

This paper presents information concerning the influence of solution pH on the aqueous reaction between potassium ferrate and phenol and three chlorinated phenols: 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP). The redox potential and aqueous stability of the ferrate ion, and the reactivity of dissociating compounds, are known to be pH dependent. Laboratory tests have been undertaken over a wide range of pH (5.8-11) and reactant concentrations (ferrate:compound molar ratios of 1:1 to 8:1). The reactivity of trichloroethylene was also investigated as a reference compound owing to its non-dissociating nature. The extent of compound degradation by ferrate was found to be highly pH dependent, and the optimal pH (maximum degradation) decreased in the order: phenol/CP, DCP, TCP; at the optimal pH the degree of degradation of these compounds was similar. The results indicate that for the group of phenol and chlorophenols studied, the presence of an increasing number of chlorine substituent atoms corresponds to an increasing reactivity of the undissociated compound, and a decreasing reactivity of the dissociated compound.     

The degradation of endocrine disruptor di-n-butyl phthalate by UV irradiation: a photolysis and product study

The direct photolysis of an important endocrine disruptor compound, di-n-butyl phthalate (DBP), has been investigated under monochromatic UV irradiation at 254 nm over a wide pH range (3-11). The investigation was carried out under idealized conditions and has considered both reaction kinetics and the degradation mechanism. It was found that more than 90% of DBP can be degraded within an hour of irradiation in water. A simple model has been developed and used to predict the initial DBP photolysis rate constant at different pH values and initial DBP concentrations. The major decomposition mechanism of DBP is believed to involve the hydrolytic photolysis of the carbon in the alpha and/or beta-position of the ester chain with the production of aromatic carboxylic derivatives. Additionally, multi-degradation pathways are proposed for acid-catalyzed hydrolytic photolysis (pH 3-5), which was found to be useful in explaining the photo-degradation of DBP under acidic conditions. The use of 254 nm UV to photo-degrade DBP was found to be a relatively fast and clean process, especially in neutral to basic conditions.     

Climate change effects on river flow to the Baltic Sea

River flow to the Baltic Sea originates under a range of different climate regimes in a drainage basin covering some 1,600,000 km2. Changes to the climate in the Baltic Basin will not only affect the total amount of freshwater flowing into the sea, but also the distribution of the origin of these flows. Using hydrological modeling, the effects of future climate change on river runoff to the Baltic Sea have been analyzed. Four different climate change scenarios from the Swedish Regional Climate Modelling Programme (SWECLIM) were used. The resulting change to total mean annual river flow to the Baltic Sea ranges from -2% to +15% of present-day flow according to the different climate scenarios. The magnitude of changes within different subregions of the basin varies considerably, with the most severe mean annual changes ranging from -30% to +40%. However, common to all of the scenarios evaluated is a general trend of reduced river flow from the south of the Baltic Basin together with increased river flow from the north.     

Sustainability and the primary extraction industries: theories and practice

This paper reflects on how sustainability is being interpreted both theoretically and in practice for the primary extraction industries. Two contrasting perspectives can be adopted: one states that continued extraction of non-renewable resources is a necessary part of sustainable development, whilst the other states that extraction of these resources must be greatly reduced or even eliminated. It is shown that these different approaches can be traced back to underlying, often unarticulated, assumptions about the acceptability of trade-offs between different societal goals; attitudes towards uncertainties in scientific analysis and the reliability of management systems; and the perceived appropriateness of system boundaries at different conceptual scales. These assumptions are founded in the self-perception of organisations and individuals about their roles in society, and the cultural context within which these organisations and individuals define their raison d'être.     

Persistent “upwelling shadows” and their influence on zooplankton distributions

Physical (temperature and salinity) and biological (zooplankton) properties were sampled over a 15 mo period in 1988 and 1989 to monitor nearshore environmental variability in northern Monterey Bay, California, USA. During the upwelling seasons of 1988 and 1989, there were two distinct bodies of water along the sampling transect. The offshore water body was characterized by recently upwelled water (typically <12°C) while the nearshore body was significantly warmer (approaching 16°C). A sharp thermal gradient (=front) separated the two water bodies. This front persisted 6.5 km from shore throughout the upwelling season of 1988 and was present again in 1989. Zooplankton-assemblage analysis confirmed the presence of two distinct regions in northern Monterey Bay. We refer to this phenomenon as an upwelling shadow, which is the result of the advection of recently upwelled water bearing nutrients and larvae past coastal recesses which are equatorward of upwelling centers.     

Sensitivity to assumptions in models of generalist predation on a cyclic prey

Ecological theory predicts that generalist predators should damp or suppress long-term periodic fluctuations (cycles) in their prey populations and depress their average densities. However, the magnitude of these impacts is likely to vary depending on the availability of alternative prey species and the nature of ecological mechanisms driving the prey cycles. These multispecies effects can be modeled explicitly if parameterized functions relating prey consumption to prey abundance, and realistic population dynamical models for the prey, are available. These requirements are met by the interaction between the Hen Harrier (Circus cyaneus) and three of its prey species in the United Kingdom, the Meadow Pipit (Anthus pratensis), the field vole (Microtus agrestis), and the Red Grouse (Lagopus lagopus scoticus). We used this system to investigate how the availability of alternative prey and the way in which prey dynamics are modeled might affect the behavior of simple trophic networks. We generated cycles in one of the prey species (Red Grouse) in three different ways: through (1) the interaction between grouse density and macroparasites, (2) the interaction between grouse density and male grouse aggressiveness, and (3) a generic, delayed density-dependent mechanism. Our results confirm that generalist predation can damp or suppress grouse cycles, but only when the densities of alternative prey are low. They also demonstrate that diametrically opposite indirect effects between pairs of prey species can occur together in simple systems. In this case, pipits and grouse are apparent competitors, whereas voles and grouse are apparent facilitators. Finally, we found that the quantitative impacts of the predator on prey density differed among the three models of prey dynamics, and these differences were robust to uncertainty in parameter estimation and environmental stochasticity.     

Stable lead isotope profiles in smelter and general urban communities: a comparison of environmental and blood measures

High-precision lead isotope ratios and lead concentrations have been compared statistically and graphically in women of child-bearing age (n = 77) from two smelter communities and one general urban community to evaluate the relative contributions to blood lead of tissue lead stores and lead from the contemporaneous environment (soil, floor dust, indoor airborne dust, water, food). Blood lead (PbB) contents were generally low (e.g. <10 g dL^–1). Statistically significant isotopic differences in blood and environmental samples were observed between the three cities although isotopic differences in blood for individual subjects living in close proximity (200 m radius) was as large as the differences within a city. No single environmental measure dominated the biological isotope profile and in many cases the low levels of blood lead meant that their isotopic profiles could be easily perturbed by relatively small changes of environmental exposure. Apportioning of sources using lead isotopes is possibly not feasible, nor cost effective, when blood lead levels are <5 g dL^–1. Interpretations based on statistical analyses of city-wide data do not give the same conclusions as when the houses are considered individually. Aggregating data from multiple subjects in a study such as this obscures potentially useful information. Most of the measures employed in this study, and many other similar studies, are markers of only short-to-medium integration of lead exposure. Serial sampling of blood and longer sampling times, especially for household variables, should provide more meaningful information.     

A framework for understanding climate change impacts on coral reef social–ecological systems

Corals and coral-associated species are highly vulnerable to the emerging effects of global climate change. The widespread degradation of coral reefs, which will be accelerated by climate change, jeopardizes the goods and services that tropical nations derive from reef ecosystems. However, climate change impacts to reef social–ecological systems can also be bi-directional. For example, some climate impacts, such as storms and sea level rise, can directly impact societies, with repercussions for how they interact with the environment. This study identifies the multiple impact pathways within coral reef social–ecological systems arising from four key climatic drivers: increased sea surface temperature, severe tropical storms, sea level rise and ocean acidification. We develop a novel framework for investigating climate change impacts in social–ecological systems, which helps to highlight the diverse impacts that must be considered in order to develop a more complete understanding of the impacts of climate change, as well as developing appropriate management actions to mitigate climate change impacts on coral reef and people.