Biomechanical model of the P-type ion pumps of the cell

The mechanisms of the Na/K pump and of the primary Ca pumps of the cell have not yet been clarified. A biomechanical model of these so-called p-type ion pumps is proposed here. It is based on the assumption that the Na ⁺ and Ca ²⁺ ions are occluded by a contracting protein chain cooperating with the ATPase section of the pump. After transfer of the chain into the region of high Na ⁺ or Ca ²⁺ concentration, the ions are released through stretching of the chain by the ATPase. In the backward transfer of the chain, a retrograde transport of Na ⁺ ions is prevented through occlusion of K ⁺ ions by another region of the same chain. In the case of Ca ²⁺ ions, a similar effect is expected from hydrated Mg ²⁺ ions. The two sections of the chain discriminate between the electrical field strength at the surface and the polarizability of the ions. The most likely mechanism for the transfer of the ion-binding chain is considered to involve a thermally induced transition of a pump dimer between two almost equivalent stable orientations in the membrane.     

Innovation and the dynamics of global warming

Global warming and the carbon cycle are a dynamic system with positive feedbacks. Fossil fuels are exhaustible resources. These two facts mean that innovation in clean energy technology, rather than mitigating global warming, can lead to a permanently higher temperature path. This paper explores the impact of innovation in the simplest model linking the economic theory of exhaustible resources with positive feedback dynamics in the carbon cycle.     

Coefficient of variation of sea surface temperature (SST) as an indicator of coral bleaching

Coral bleaching has become a major problem on reefs around the world in recent decades. It is believed that mean temperature alone is the primary force driving this ecological phenomenon. We propose that variance in temperature in the short term is just as important as the mean. Thirty years of daily sea surface temperature (SST) data have been collected by the University of Puerto Rico at Mayaguez Marine Laboratory in La Parguera, PR. These data were collated and analyzed initially (by Amos Winter) for their relationship to coral bleaching in this area. We found that the data fell into three categories: high mean temperatures associated with severe bleaching, cooler mean temperatures associated with no bleaching, and years of high SSTs but with no coral bleaching. Here, we examined the relationship between mean temperature during those months in which bleaching occurred, temperature variance (as measured by standard deviation), and coefficient of variation (CV; i.e., SD standardized by the mean). We also derived a critical threshold temperature and level of resolution in time for calculating these statistics to clearly describe the circumstances of bleaching versus non-bleaching events, particularly at marginal bleaching temperatures. These characteristics were compared for the four warmest months of the year (July–October) for four warm bleaching years (1969, 1987, 1990, and 1995), four cool non-bleaching years (1984, 1985, 1986, and 1988), and two warm non-bleaching years (1994 and 2000). No relationship was found between the mean SST and SD in terms of predicting bleaching. The two primary statistics which, in concert, did indicate bleaching, however, were the short-term, biweekly mean temperature and its the associated CV. Bleaching occurs in association with both high temperatures and a high CV. The CV becomes a critical determinant of bleaching only when temperatures are ∼29.1–29.8°C. The warm, non-bleaching years were generally characterized by a CV of < 1.9 and a temperature range between 28.5 and 29.9°C. We conclude that increased mean SSTs alone are not sufficient to induce coral bleaching; a high variance in SST at marginal, lower bleaching temperatures can induce bleaching, and likewise, a low variance of such will not induce bleaching. This variance is most clearly described by the CV.     

Effects of natural organic matter on the microporous sorption sites of black carbon in a Yangtze River sediment

Black carbon (BC), characterized by high microporosity and high specific surface area (SSA), has been demonstrated to have substantial contributions to the sorption of hydrophobic organic chemicals in soils and sediments. Other naturally occurring organic matters provide soft and penetrable sorption domains while may cling to BC and affect its original surface properties. In this work, we studied the sorption sites of a Yangtze River sediment sample with organic carbon (OC) content of 3.3 % and the preheated sediment (combusted at 375 °C) with reduced OC content (defined as BC) of 0.4 % by gas and pyrene sorption. The SSA and microporosity of the pristine and preheated sediments were characterized by N₂ and CO₂ adsorption. The results suggest that the adsorption of N₂ was hindered by amorphous organic carbon (AOC) in the pristine sediment but CO₂ was not. Instead, the uptake of CO₂ was higher in the presence of AOC, likely due to the partition of CO₂ molecules into the organic matter. The pyrene adsorptions to BC in pristine and preheated sediments show a similar adsorption capacity at high concentration, suggesting that AOC of ca. 2.9 % in the pristine sediment does not reduce the accessibility to the sorption sites on BC for pyrene.     

Contaminant Exposure and Effects—Terrestrial Vertebrates Database: Trends and Data Gaps for Atlantic Coast Estuaries

In order to examine the condition of biota in Atlantic coast estuaries, "Contaminant Exposure and Effects—Terrestrial Vertebrates" database (CEE-TV) has been compiled through computerized search of published literature, review of existing databases, and solicitation of unpublished reports from conservation agencies, private groups, and universities. Summary information has been entered into the database, including species, collection date (1965–present), site coordinates, estuary name, hydrologic unit code, sample matrix, contaminant concentrations, biomarker and bioindicator responses, and reference source, utilizing a 98-field character and numeric format. Currently, the CEE-TV database contains 3699 geo-referenced records representing 190 vertebrate species and >140,000 individuals residing in estuaries from Maine through Florida. This relational database can be directly queried or imported into a Geographic Information System to examine spatial patterns, identify data gaps and areas of concern, generate hypotheses, and focus ecotoxicological field assessments. Information on birds made up the vast majority (83%) of the database, with only a modicum of data on amphibians (<0.1%). Of the >75,000 chemical compounds in commerce, only 118 commonly measured environmental contaminants were quantified in tissues of terrestrial vertebrates. There were no CEE-TV data records in 15 of the 67 estuaries located along the Atlantic coast and Florida Gulf coast. The CEE-TV database has a number of potential applications including focusing biomonitoring efforts to generate critically needed ecotoxicological data in the numerous "gaps" along the coast, reducing uncertainty about contaminant risk, identifying areas for mitigation, restoration or special management, and ranking ecological conditions of estuaries.     

Monitoring the formation of structures and patterns during initial development of an artificial catchment

The objective of this paper is to present observations, results from monitoring measurements, and preliminary conclusions about the development of patterns and structures during the first 5 years of development of an artificial catchment starting from point zero. We discuss the high relevance of initial system traits and external events for the system development and draw conclusions for further research. These investigations as part of a Collaborative Research Center, aim to disentangle and understand the feedback mechanisms and interrelationships of processes and their co-development with spatial and temporal structures and patterns by studying an initial, probably less complex ecosystem. Therefore, intensive measurements were carried out in the catchment with regard to the development of surface structures, hydrological patterns, vegetation dynamics, water chemistry, and element budgets. During the first 5 years, considerable changes within the catchment were observed. Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the artificial catchment. Initial structures formed by the construction process and initial substrate characteristics were decisive for the distribution and flow of water. External factors like episodic events triggered erosion and dissection during this initial phase, promoted by the low vegetation cover, and the unconsolidated sandy substrate. The transformation of the initial geosystem into areas with evolving terrestrial or aquatic characteristics and from a very episodic to a more permanent stream network and discharge, together with the observed vegetation dynamics increased site diversity and heterogeneity with respect to water and nutrient availability and transformation processes compared with the more homogenous conditions at point zero. The processes and feedback mechanisms in the initial development of a new landscape may deviate in rates, intensity, and dominance from those known from mature ecosystems. It is therefore crucial to understand these early phases of ecosystem development and to disentangle the increasingly complex interactions between the evolving terrestrial and aquatic, biotic, and abiotic compartments of the system. Long-term monitoring of initial ecosystems may provide important data and parameters on processes and the crucial role of spatial and temporal structures and patterns to solve these problems. Artificially created catchments could be a suitable tool to study these initial developments at the landscape scale under known, designed, and defined boundary conditions.     

Export of nutrients from golf courses on the Precambrian Shield

Annual export rates, or fluxes, of total nitrogen (TN), nitrate, total phosphorus (TP) and potassium from four streams on two golf courses on the Precambrian Shield were compared with those from forested reference locations. Overall, the mean annual fluxes of K, TN, NO(3) and TP from golf courses were greater than from forested areas by 10, 2, 6 and 2 times, respectively. The overall mean export coefficients (kg/ha/yr) were 16 for K, 5.2 for TN, 2.1 for NO(3) and 0.14 for TP. For TN and TP, these are similar to those reported from cropland in Canada by Chambers and Dale.