Use of the ouput of a lead risk assessment model to establish soil lead cleanup levels

Three general methods to calculate soil contaminant cleanup levels are assessed: the truncated lognormal approach, Monte Carlo analysis, and the house-by-house approach. When these methods are used together with a lead risk assessment model, they yield estimated soil lead cleanup levels that may be required in an attempt to achieve specified target blood lead levels for a community. The truncated lognormal approach is exemplified by the Society for Environmental Geochemistry and Health (SEGH) model, Monte Carlo analysis is exemplified by the US EPA's LEAD Model, and the house-by-house approach is used with a structural equation model to calculate site-specific soil lead cleanup levels. The various cleanup methods can each be used with any type of lead risk assessment model. Although all examples given here are for lead, the cleanup methods can, in principle, be used as well with risk assessment models for other chemical contaminants to derive contaminant-specific soil cleanup levels.     

Loss of mating opportunities influences refuge use in the Iberian rock lizard,<Emphasis Type="Italic"> Lacerta monticola</Emphasis>

Because time spent in refuge may be costly if prey lose opportunities to forage, fight, or mate, prey allow predators to approach closer before beginning to flee when opportunity costs are high. Because the same opportunity costs may apply to refuge use as to escape, prey should make similar trade-offs between risk of emerging and cost of remaining in refuge. In the Iberian rock lizard, Lacerta monticola, we studied the effects of sex, reproductive season, speed of predator approach, and potential loss of mating opportunities on time spent in refuge following simulated predatory attacks. Lizards of both sexes adjusted refuge use to the level of risk by spending more time in refuge when approached rapidly than slowly. Females remained in refuge for equal times in the mating and postreproductive seasons, but males emerged sooner during the mating season, suggesting adjustment to a cost of lost opportunity to search for mates during the mating season. When a tethered female was nearby, males emerged from refuge earlier than if no female was present, indicating a trade-off between risk and mating opportunity. Approach speed affected emergence time when females were absent, but not when a female was present. Approach speed did not affect the probability that, after emerging, a male would return to court the female. For males that courted females intensely (bit them) before entering refuge, approach speed did not affect latency to emerge, but males that courted less intensely emerged sooner if approached slowly than rapidly. These findings show that males adjust the length of time spent in refuge to both risk of predation and reproductive cost of refuge use.Communicated by A. Mathis     

Symmetry, male dominance and female mate preferences in the Iberian rock lizard, Lacerta monticola

Female preference for dominant males is widespread and it is generally assumed that success in male-male competition reflects high quality. However, male dominance is not always attractive to females. Alternatively, relatively symmetric individuals may experience fitness advantages, but it remains to be determined whether males with more symmetrical secondary sexual traits experience advantages in both intra- and intersexual selection. We analysed the factors that determine dominance status in males of the lizard Lacerta monticola, and their relationship to female mate preference, estimated by the attractiveness of males' scents to females. Sexually dimorphic traits of this lizard (head size and femoral pores) appear to be advanced by different selection pressures. Males with relatively higher heads, which give them advantage in intrasexual contests, were more dominant. However, head size was unimportant to females, which preferred to be in areas marked by relatively heavier males, but also by males more symmetric in their counts of left and right femoral pores. Chemicals arising from the femoral pores and other glands might honestly indicate quality (i.e. related to the symmetry levels) of a male to females and may result from intersexual selection. Females may use this information because the only benefit of mate choice to female lizards may be genetic quality. Chemical signals may be more reliable and have a greater importance in sexual selection processes of lizards than has previously been considered.     

Precipitation of aragonite by calcitic bivalves in Mg-enriched marine waters

To understand the relative importance of biological versus physicochemical control over biomineralization, we have tested if the chemical composition of the medium (i.e., the Mg/Ca ratio) can change the mineralogy of mollusk shells. The shells of mollusks are made of calcite and/or aragonite, which are by far the most common CaCO₃ polymorphs. Several species of bivalves with predominantly calcitic shells have been cultivated in artificial seawater with a Mg/Ca molar ratio within the range of 8.3–9.2, well above the present value for seawater (5.2). Four out of six species used (the scallop Chlamys varia, the oyster Ostrea edulis, the saddle oyster Anomia ephippium and the mussel Mytilus edulis) survived long enough to secrete significant amounts of calcium carbonate. The deposits (sometimes extensive) formed on the interior shell surfaces were predominantly aragonitic. Three individuals of C. varia also increased their length by adding new shell at the margin. Contrary to the internal shell deposits, these margins were high-Mg calcite. This implies that the marginal mantle is able to exert a more strict control on the secreted mineral phase than the mantle facing the internal shell surface. This is the first report on an in vivo experimentally forced switch in bivalve shell mineralogy, from calcite to aragonite due to a change in water chemistry.     

The role of root organic acids in the tolerance of Festuca rubra to zinc,lead and cadmium

Abstract

Festuca rubra L. plants are pseudometallophytes colonizing abandoned Pb/Zn mine areas, successfully employed in phytostabilization. To study the contribution of low-molecular weight organic acids to metal tolerance, F. rubra plants were grown for three months in hydroponics with Cd (1.8, 18 and 36 µmol?L^?1), Pb (50, 250 and 500?µmol?L^?1) and Zn (0.3, 3 and 6?mmol?L^?1), separately, and in ternary combination (18?µmol?L^?1 Cd + 250?µmol?L^?1 Pb + 0.3?mmol?L^?1 Zn). The roots retained most of the metals but their distribution from shoot to root was altered when the plants were treated with the ternary combination. The main organic acids in roots were citrate and malate. At the lowest concentrations, the metals caused small reductions in biomass, had no effects on photosynthetic pigments nor on malondialdehyde, but led to increases in root organic acids. At higher concentrations, phytotoxic responses were observed, associated with a decline of citrate and malate in the roots.     

Forest cover dynamics in the Selva Maya of Central and Southern Quintana Roo,Mexico: deforestation or degradation?

ABSTRACT

Forest cover dynamics (1993-2018) was assessed in two regions on the Yucatan Peninsula: Zona Maya (ZM), 67% indigenous with shifting cultivation and community forestry; and Bacalar–Rio Hondo (BRH), mainly commercial agriculture and pastureland. Degradation (12,915 ha y^?1) exceeded deforestation (5882 ha y^?1) and was worse in BRH. In BRH there was a net forest loss (?1.6% y^?1) associated with pastureland and commercial agriculture. In ZM, mature forest recovery (1.4% y^?1) and dynamic forest cover (continuous loss and gain) were associated with shifting cultivation. Changes were more intense during 2011–2018 and gains of mature forest in ZM and deforested areas in BRH targeted secondary vegetation. Fragments of mature and secondary vegetation decreased, and connectivity improved in ZM, but opposite trends occurred in BRH. Reporting and monitoring deforestation using Global Forest Watch data is inadequate since 62% of forest cover loss represent degrading or recovering forest cover.     

Comparison of Spatial Methods for the Assessment of Planktonic Patches

Planktonic patches are defined as areas where the abundance of plankters is above a threshold value τ. The estimation of patch size and shape can be approached using spatial statistical tools, using truncated random fields or indicator random fields as classifiers. In all cases there is the risk of false positive and false negative errors. In this paper we present the results of a comparative study on the performance of four commonly used methods: conditional simulation and kriging, both in the original measurement units of the data and under an indicator transform. We used a misclassification cost function to compare the four methods. Our results show that conditional simulation in the original measurement units attains the lowest misclassification cost. We also illustrate how the point at which this minimum is attained can be used to chose an optimal cut-off value for binary classification. Received: December 2003 / Revised: June 2005     

A cost worth paying: energetically expensive interactions with males protect females from intrasexual aggression

When approached by males, females of the Amarillo fish (Girardinichthys multiradiatus) perform a behaviour called vibration or they are aggressively challenged. We quantified vibration and assessed whether it compromises the rate of feeding attempts in dyads kept in outdoor enclosures. Male approaches resulted in female vibration and in a reduced feeding rate. Vibration was not evoked by female–female aggression, which was frequent and always ended in the subordinate fleeing from the dominant female. Using a closed respirometer we found that vibration is costly; oxygen consumption of females was greater in the presence of a male (which evoked vibration) than in the presence of a non-familiar female (when no vibration occurred). By recording interactions of females confined in aquaria in the presence and in the absence of males, we confirmed that escaping is the only available response to deal with female aggression. Females kept without males participated in frequent aggressive (even lethal) interactions that did not abate while the subordinate female was in sight of the dominant, and which caused premature births and injuries. Yet in the alternative treatment aggression ceased when a male approached, prompting vibration in both females. Thus, in the Amarillo, in as much as it evokes energetically costly female vibrations, male courtship is an expression of sexual conflict. However, in the absence of males, frequent female aggression potentially annuls the benefits of not vibrating. We propose that a complete appraisal of the consequences of sexual conflict must include an assessment of the costs imposed by intra-sexual interactions.     

Control of reproduction in social insect colonies: individual and collective relatedness preferences in the paper wasp, Polistes annularis

Social insect colonies often have one or a few queens. How these queens maintain their reproductive monopoly, when other colony members could gain by sharing in the reproduction, is not generally known. DNA microsatellite genotyping is used to determine reproductive interests of various classes of colony members in the paper wasp, Polistes annularis. The relatedness estimates show that the best outcome for most individuals is to be the reproductive egg-layer. For workers, this depends on the sex of offspring: they should prefer to lay their own male eggs, but are indifferent if the queen lays the female eggs. The next-best choice is usually to support the current queen. As a rule, subordinates and workers should prefer the current queen to reproduce over other candidates (though subordinates have no strong preference for the queen over other subordinates, and workers may prefer other workers as a source of male eggs). This result supports the theory that reproductive monopoly stems from the collective preferences of non-reproductives, who suppress each other in favor of the queen. However, we reject the general hypothesis of collective worker control in this species because its predictions about who should succeed after the death of the present queen are not upheld. The first successor is a subordinate foundress even though workers should generally prefer a worker successor. If all foundresses have died, an older worker succeeds as queen, in spite of a collective worker preference for a young worker. The results support the previous suggestion that age serves as a conventional cue serving to reduce conflict over queen succession. Received: 3 May 1996 / Accepted after revision: 22 September 1996