Effects of sublethal concentrations of mercuric chloride on ammonium-limitedSkeletonema costatum

The effect of sublethal additions of mercuric chloride on the marine diatomSkeletonema costatum (Grev.) Cleve grown in NH₄-limited chemostats and batch cultures was assessed. In short-term Hg exposure experiments (up to 5 h), the effect of Hg on ammonium uptake rates was studied by simulatneously perturbing the culture with 5 M NH₄ Cl and Hg concentrations ranging from 0.04 to 5.52 nM HgCl₂. The threshold of Hg toxicity occurred between 1.8 and 3.7 nM, based on a decrease in ammonium uptake rates. When the NH₄-limited culture was starved of ammonium for 30 h, the threshold of Hg toxicity decreased about an order of magnitude to 0.2 nM. In long-term Hg exposure experiments (679.5 h), NH₄-limited continuous cultures were semi-continuously exposed to 0.37 and 3.68 nM HgCl₂. After 4 days, the cell density in the Hg-treated chemostats began to drastically decline. After about 16 days these populations recovered, even though Hg additions continued. At the end of the experiment (26 days), cell densities had reached the levels observed at the beginning of the experiment. The reason for the recovery is unknown, but several possibilities are discussed. Ammonium uptake rates determined during the time-course of this long-term Hg exposure, indicated that these NH₄-limited cultures exhibited a significant loss in their ability to take up ammonium at low concentrations (e.g. 1 M). Thus, mercury pollution may seriously decrease the ability of a species to utilize the limiting nutrient during periods of seasonal nutrient limitation.     

Kinship,demography, and belding's ground squirrel nepotism

Summary Social behavior and demography of a freeliving population of individually marked Belding's ground squirrels (Spermophilus beldingi) were studied from 1974 through 1980 at Tioga Pass, California. Relative frequencies of fighting, chasing, cooperation in chasing conspecifics, and assisting conspecifics who were being chased were recorded for adult (1-year-old) female kin of nine different degrees of matrilineal relatedness. The animals' mortality and dispersal patterns were also analyzed.Mothers and daughters, littermate sisters, and nonlittermate (half-) sisters were cooperative; their cooperation varied in proportion to relatedness. In contrast, grandmothers and granddaughters, aunts and nieces, great grandmothers and great granddaughters, aunts and half-nieces, first cousins, and first cousins once removed did not cooperate; their behavior was indistinguishable from that of nonrelatives.While there were no consistent spatial differences among the burrows of the nine categories of female kin, only mothers and daughters, littermate sisters, and nonlittermate sisters were consistently alive simultaneously. The apparent correspondence between the relatives that received social favoritism and those that consistently co-occurred suggests that demography, particularly survivorship, may have determined the extent of ground squirrel favoritism, while kinship influenced its pattern.     

A closer look at detectability

Environmental and Ecological Statistics - The theory underlying line transect and variable circular plot surveys—distance sampling—begins with an assumed detectability function, giving...     

Honeybees maximize efficiency by not filling their crop

Summary Honeybees often abandon non-depleting food sources with a partially filled crop. This behaviour does not maximise the net rate of energy extraction from the food sources, and thus contradicts predictions of some common models for central place foragers. We show that including the metabolic costs of transport of nectar leads to models that predict partial crop-loading. Furthermore, the observed crop loads of honeybees are less consistent with those predicted by maximization of delivery rate to the hive (net energetic gain/ unit time), than with those predicted by maximization of energetic efficiency (net energetic gain/unit energy expenditure). We argue that maximization of energetic efficiency may be an adaptation to a limited flight-cost budget. This constraint is to be expected because a worker's condition seems to deteriorate as a function of the amount of flight performed.     

Reproductive ecology of <Emphasis Type="Italic">Fungiacyathus marenzelleri</Emphasis> from 4100 m depth in the northeast Pacific Ocean

Fungiacyathus marenzelleri (Vaughan, 1906) is a deep-water solitary coral, cosmopolitan in distribution that is found at depths of 300–6,328 m. This study examined gametogenesis, inter-annual variability and reproductive periodicity of F. marenzelleri collected from Station M (34°50′N, 123°00′W) in the northeast Pacific at a depth of 4,100 m. Samples were collected (May, June, October 1996; August 1998; February, June 2001; and June 2002) and histologically processed with spermatogenic stage, oocyte size and fecundity measured. Four stages of spermatogenesis were identified and all males contained multiple stages of sperm development in each seasonal sample. Three stages of oocyte development were identified; previtellogenic (<28–150 μm), vitellogenic (150–300 μm) and late vitellogenic (300–400 μm). Comparison of mean oocyte diameters among sampling dates showed there were no inter-annual variations or seasonal differences. Overall, fecundity was 1,290 (±407) oocytes polyp⁻¹, and with no significant differences between sample months. Fecundity was not polyp-size dependent. This study shows a similar quasi-continuous mode of reproduction to this species examined from the Northeast Atlantic Ocean, but the fecundity is reduced by 50%. The reproductive output may fluctuate in relation to the input of organic material at this site, as shown by non-significant trends in the oocyte size-frequency and fecundity data. A quasi-continuous output of gametes would promote successful fertilisation and wide dispersal of the lecithotrophic larvae.     

Economic growth,public welfare and sustainability: an empirical system analysis

SUMMARY

This paper explores the relationships between economic activity and sustainability, growth, and welfare. The issues regarding the nature of the relationships were framed by Ekins in questions which are addressed empirically across countries and the states of the US. The sustainability issue is addressed by comparing nonrenewable energy throughput, a surrogate for impacts, to the renewable energy throughput in the associated ecosystem. The effect of a changing energy intensity, in developing and developed countries, on socioeconomic variables provides clues to social welfare. In developing countries a rising energy throughput (economic growth) and energy intensity is positively related to public welfare while impacts are generally moderate. The reverse appears to be true in developed countries, i.e. as energy throughput and intensity rise in developed countries and the US states, pollution and impacts also rise while socioeconomic variables worsen, so public welfare begins to decline. Economic development appears to pass through three phases which can be characterized by the nature and extent of its energy use. Each phase exhibits characteristic energy, pollution, structural and socioeconomic trends.     

Defensive anointing: extended chemical phenotype and unorthodox ecology

Summary. Many animals acquire substances on their integument from heterospecifics through anointing. In active or self-anointing, animals rub against scent sources or they apply them by appendage or mouth. In passive anointing, animals adsorb emitted chemicals. Most investigators suggest that chemicals appropriated via anointing deter predators, ectoparasites, and/or microbial pathogens. Similarly, nesting birds and brood parasites of social insects acquire chemicals from and reside unmolested near or within insect colonies. The acquisition through anointing of chemicals that deter predators, ectoparasites, microbial pathogens, and other offenders, i.e. defensive anointing, constitutes an extended phenotype: the genetic machinery by which defensive compounds are synthesized does not reside with the anointing organisms, but the sensory mechanisms and/or behavioral tendencies by which chemicals are appropriated from heterospecifics do. The ecological relationships between anointing organisms and chemical donors, and between chemical donors and those responding to chemicals appropriated via anointing, may be unorthodox. Interactions between anointing organisms and chemical donors typically entail abrasive contact with or other damage to the latter. These encounters sometimes are evidenced by telltale marks on chemical donors or by chemicals deposited on the integument of anointing organisms. The organisms furnishing chemicals and those affected by them may not interact, and they may even occupy different habitats, because mobile anointing organisms are the medium by which chemicals are disseminated. Thus, in allelochemical studies where anointing is involved, species can be tested, with ecological legitimacy, using chemicals from organisms they might fail to interact with in nature. Practical implications of anointing stem from its potential importance in conservation and captive management, where consideration is given to the protection that animals derive by accessing topically acquired chemicals from heterospecifics.     

Bayes Estimation of a Distribution Function Using Ranked Set Samples

Aranked set sample (RSS), if not balanced, is simply a sample of independent order statistics gener- ated from the same underlying distribution F. Kvam and Samaniego (1994) derived maximum likelihood estimates of F for a general RSS. In many applications, including some in the environ- mental sciences, prior information about F is available to supplement the data-based inference. In such cases, Bayes estimators should be considered for improved estimation. Bayes estimation (using the squared error loss function) of the unknown distribution function F is investigated with such samples. Additionally, the Bayes generalized maximum likelihood estimator (GMLE) is derived. An iterative scheme based on the EM Algorithm is used to produce the GMLE of F. For the case of squared error loss, simple solutions are uncommon, and a procedure to find the solution to the Bayes estimate using the Gibbs sampler is illustrated. The methods are illustrated with data from the Natural Environmental Research Council of Great Britain (1975), representing water discharge of floods on the Nidd River in Yorkshire, England     

Quantifying species recovery and conservation success to develop an IUCN Green List of Species

Stopping declines in biodiversity is critically important, but it is only a first step toward achieving more ambitious conservation goals. The absence of an objective and practical definition of species recovery that is applicable across taxonomic groups leads to inconsistent targets in recovery plans and frustrates reporting and maximization of conservation impact. We devised a framework for comprehensively assessing species recovery and conservation success. We propose a definition of a fully recovered species that emphasizes viability, ecological functionality, and representation; and use counterfactual approaches to quantify degree of recovery. This allowed us to calculate a set of 4 conservation metrics that demonstrate impacts of conservation efforts to date (conservation legacy); identify dependence of a species on conservation actions (conservation dependence); quantify expected gains resulting from conservation action in the medium term (conservation gain); and specify requirements to achieve maximum plausible recovery over the long term (recovery potential). These metrics can incentivize the establishment and achievement of ambitious conservation targets. We illustrate their use by applying the framework to a vertebrate, an invertebrate, and a woody and an herbaceous plant. Our approach is a preliminary framework for an International Union for Conservation of Nature (IUCN) Green List of Species, which was mandated by a resolution of IUCN members in 2012. Although there are several challenges in applying our proposed framework to a wide range of species, we believe its further development, implementation, and integration with the IUCN Red List of Threatened Species will help catalyze a positive and ambitious vision for conservation that will drive sustained conservation action.     

Ordering effects and choice set awareness in repeat-response stated preference studies

We present an experiment designed to investigate the presence and nature of ordering effects within repeat-response stated preference (SP) studies. Our experiment takes the form of a large sample, full-factorial, discrete choice SP exercise investigating preferences for tap water quality improvements. Our study simultaneously investigates a variety of different forms of position-dependent and precedent-dependent ordering effect in preferences for attributes and options and in response randomness. We also examine whether advanced disclosure of the choice tasks impacts on the probability of exhibiting ordering effects of those different types. We analyze our data both non-parametrically and parametrically and find robust evidence for ordering effects. We also find that the patterns of order effect in respondents' preferences are significantly changed but not eradicated by the advanced disclosure of choice tasks a finding that offers insights into the choice behaviors underpinning order effects.