Quantitative structure–activity relationship methods for the prediction of the toxicity of pollutants

Environmental Chemistry Letters - Continuous flow of toxic and persistent compounds to the environment is a global health issue. However, assessing the toxic effects of compounds...     

The relative influence of habitat loss and fragmentation: do tropical mammals meet the temperate paradigm?

The relative influence of habitat loss vs. habitat fragmentation per se (the breaking apart of habitat) on species distribution and abundance is a topic of debate. Although some theoretical studies predict a strong negative effect of fragmentation, consensus from empirical studies is that habitat fragmentation has weak effects compared with habitat loss and that these effects are as likely to be positive as negative. However, few empirical investigations of this issue have been conducted on tropical or wide-ranging species that may be strongly influenced by changes in patch size and edge that occur with increasing fragmentation. We tested the relative influence of habitat loss and fragmentation by examining occupancy of forest patches by 20 mid- and large-sized Neotropical mammal species in a fragmented landscape of northern Guatemala. We related patch occupancy of mammals to measures of habitat loss and fragmentation and compared the influence of these two factors while controlling for patch-level variables. Species responded strongly to both fragmentation and loss, and response to fragmentation generally was negative. Our findings support previous assumptions that conservation of large mammals in the tropics will require conservation strategies that go beyond prevention of habitat loss to also consider forest cohesion or other aspects of landscape configuration.     

Do microbial processes regulate the stability of a coral atoll's enclosed pelagic ecosystem?

Complex marine ecosystems contain multiple feedback cycles that can cause unexpected responses to perturbations. To better predict these responses, complicated models are increasingly being developed to enable the study of feedback cycles. However, the sparseness of ecological data often limits the direct empirical parameterization of all model parameters. Here we use a Bayesian inverse analysis approach to synthesize empirical data and ecological theory derived from published studies of a coral atoll's enclosed pelagic ecosystem (Takapoto Atoll, French Polynesia). We then use the estimates of flux magnitudes to parameterize probabilistic compartment models with two forms of heterotrophic consumption: (1) “bottom-up” donor-controlled heterotrophic consumption and (2) “top-down” mass-action heterotrophic consumption. We explore how the flux magnitudes affect the ecosystem's stability properties of resilience, reactivity, and resistance under both assumptions for heterotrophic consumption. The models suggest that the microbial uptake of dissolved organic carbon (DOC) regulates the long term rate of return to steady state following a temporary or pulse perturbation (resilience), and the cycling of carbon between abiotic pools and heterotrophic compartments regulates the short-term response (reactivity). In the bottom-up process model, the sensitivity of steady state masses following a sustained or press perturbation (resistance) is highest for the DOC pool following a sustained change to the microbial uptake rate of DOC. Further, a change in the microbial uptake of DOC propagates through the ecosystem and affects the steady state values of zooplankton. The analysis suggests that the food web is highly dependent on the recycling between the abiotic and biotic carbon pools, particularly as mediated by the microbial consumption of DOC, and this recycling determines how the ecosystem responds to perturbations.     

The role of water in the development of The Netherlands— a historical perspective

In this paper an overview is presented of the landscape development of the low-lying parts of The Netherlands. It is shown that water has played an important role in this development. Since prehistoric times, but especially since about 800 AD, man has gradually occupied the low lands along the sea and the main rivers. Through these settlements a chain of actions and reactions of man and his physical environment was set into motion. This chain of events is briefly outlined. It is stated and also illustrated that not only the characteristics of the landscape of the western part of The Netherlands, but also the organization of the Dutch society has been influenced strongly by manÕs need to cope with the omnipresence of water and the threats and opportunities posed by that. It is concluded that the outlined events can only be understood properly if interdisciplinary research takes a more prominent role than it does now.     

A dynamic size-structured population model: does disturbance control size structure of a population of the massive coral Gardineroseris planulata in the Eastern Pacific?

Using a long-term data set of Gardineroseris planulata (Dana) on Uva Island reef, Panamá, we developed a simulation model that relates size-specific schedules of growth and partial mortality to predation by Acanthaster planci (Linnaeus) and El Niño–Southern Oscillation (ENSO)-related elevation of water temperature. We compared the model predictions to field observations for both the subpopulation of colonies that was used for model development and for the entire population. No statistically significant differences in the size-frequency distributions of the real and modeled coral populations were found for the subpopulation during any of 9 yr or for the entire population during 4 yr. These results suggested that the model relationships were reflecting field conditions. Longer-term (100 yr) simulations were conducted to assess the relative importance of predation and ENSO-related colony losses in determining the size structure of the coral population. Predation by A. planci was of overwhelming importance due to both stronger effects of predation (larger transitions) and the frequency of predation (yearly) compared to ENSO (episodically). Even the least-frequent predation scenario skewed the distribution toward smaller colonies, while simulations where populations were subjected to frequent ENSO events (≥3 yr) still maintained colonies in the largest size class. The model results suggested that sea star predators may not have been in the present abundance on this reef prior to the last 30 yr; with predators present, the model predicts that the distribution would be skewed toward smaller colonies.     

The As-Contaminated Elqui River Basin: a Long Lasting Perspective (1975–1995) Covering the Initiation and Development of Au–Cu–As Mining in the High Andes of Northern Chile

The Elqui watershed (northern Chile) constitutes a highly contaminated river system, with arsenic exceeding by up to three orders of magnitude the average for river waters. There are three main reasons that explain this contamination: (1) the regional geology and hydrothermal (mineralizing) processes that developed in this realm during Miocene time; (2) the later unroofing–erosion–oxidation–leaching of As–Cu rich sulfide ores, a process that have been taking place for at least 10,000 years; and last but not least (3) mining activities at the high-altitude (>4000 m above sea level) Au–Cu–As El Indio mine, from the late 1970s onwards. The El Indio mineral deposit hosted large veins of massive sulfides, including the important presence of enargite (Cu₃AsS₄). The continuous natural erosion of these veins and their host rocks (also rich in As and Cu) during Holocene time, led to important and widespread metal dispersion along the river system. During the studied pre mining period (1975–1977), the high altitude river Toro waters already showed very large As concentrations (0.36–0.52 mg l⁻¹). The initiation of full scale mining at El Indio (1980 onwards) led to an increase of these values, reaching a concentration of 1.51 mg l⁻¹ As in 1995. During the same year other rivers of the watershed reached peak As concentrations of 0.33 (Turbio) and 0.11 mg l⁻¹ (Elqui). These figures largely exceed the USEPA regulations for drinking water (0.01 mg l⁻¹ As), and about 10% of the total As data from the river Elqui (and 70% from the river Turbio) are above the maximum level allowed by the Chilean law for irrigation water (0.1 mg l⁻¹ As).     

Behavioral type–environment correlations in the field: a study of three-spined stickleback

Behavioral type–environment correlations occur when specific behavioral types of individuals are more common in certain environments. Behavioral type–environment correlations can be generated by several different mechanisms that are probably very common such as niche construction and phenotypic plasticity. Moreover, behavioral type–environment correlations have important ecological and evolutionary implications. However, few studies have examined behavioral type–environment correlations in natural populations. In this study, we asked whether some behavioral types of three-spined stickleback were more likely to occur in certain social environments (alone or in a shoal with other stickleback) or in certain microhabitats in a river (in the open or under cover). We found that individuals that were in shoals with other stickleback at the time of collection from the field emerged from a refuge more quickly compared to individuals that were found alone. In addition, fish that were alone in an open microhabitat explored more of a pool compared to fish that were alone in cover, but this difference did not occur among fish that were in shoals at the time of collection. Subsequent analyses of gut contents suggested that differences in microhabitat use were consistent over time. Our study provides some of the first evidence for behavioral type–environment correlations in a natural population of non-human animals.     

The benefit of obligate versus facultative strategies in a shrimp–goby mutualism

Obligate mutualists are predicted to benefit more from mutualism than facultative mutualists and harbor traits that help derive this extra benefit. I tested these predictions with a shrimp–goby mutualism. Individual shrimp (Alpheus floridanus) construct burrows that are shared with individual gobiid fishes that warn shrimp when emergence from burrows is unsafe. The benefit to gobies is refuge from predation. I compared predator avoidance performance of obligate (Nes longus) and facultative (Ctenogobius saepepallens) shrimp-associated gobies with access to a shell, a shrimp burrow, or no shelter. The two gobies performed similarly with shells and no shelter, but N. longus outperformed C. saepepallens with shrimp burrows. Thus, N. longus benefits more from mutualism than C. saepepallens. Also, N. longus has four behavioral traits that likely allow it to benefit from mutualism more than does C. saepepallens: (1) diving into the nearest shrimp burrow when confronted with predators, (2) long flight initiation distance, (3) long time-until-re-emergence after taking refuge, and (4) remaining close to shelter. The latter three likely come with a cost to foraging or mate acquisition as they limit searching range outside the burrow and detract from time spent outside burrows. Thus, N. longus likely harbors traits that allow it to deal with these costs. I discuss a framework for determining whether traits crucial to obligate association with shrimp (both for reaping benefits and dealing with costs) are pre-adaptations or are created through coevolution with shrimp.     

The flow structure in the wake of a fractal fence and the absence of an “inertial regime”

Recent theoretical work has highlighted the importance of multi-scale forcing of the flow for altering the nature of turbulence energy transfer and dissipation. In particular, fractal types of forcing have been studied. This is potentially of real significance in environmental fluid mechanics where multi-scale forcing is perhaps more common than the excitation of a specific mode. In this paper we report the first results studying the detail of the wake structure behind fences in a boundary layer where, for a constant porosity, we vary the average spacing of the struts and also introduce fractal fences. As expected, to first order, and in the far-wake region, in particular, the response of the fences is governed by their porosity. However, we show that there are some significant differences in the detail of the turbulent structure between the fractal and non-fractal fences and that these override differences in porosity. In the near wake, the structure of the fence dominates porosity effects and a modified wake interaction length seems to have potential for collapsing the data. With regards to the intermittency of the velocities, the fractal fences behave more similarly to homogeneous, isotropic turbulence. In addition, there is a high amount of dissipation for the fractal fences over scales that, based on the energy spectrum, should be dominated by inter-scale transfers. This latter result is consistent with numerical simulations of flow forced at multiple scales and shows that what appears to be an “inertial regime” cannot be as production and dissipation are both high.     

Convergence of stakeholders’ environmental threat perceptions following mass coral bleaching of the Great Barrier Reef

Managing human use of ecosystems in an era of rapid environmental change requires an understanding of diverse stakeholders’ behaviors and perceptions to enable effective prioritization of actions to mitigate multiple threats. Specifically, research examining how threat perceptions are shared or diverge among stakeholder groups and how these can evolve through time is increasingly important. We investigated environmental threat perceptions related to Australia's Great Barrier Reef and explored their associations before and after consecutive years of mass coral bleaching. We used data from surveys of commercial fishers, tourism operators, and coastal residents (n = 5254) conducted in 2013 and 2017. Threats perceived as most serious differed substantially among groups before bleaching but were strongly aligned after bleaching. Climate change became the most frequently reported threat by all stakeholder groups following the coral bleaching events, and perceptions of fishing and poor water quality as threats also ranked high. Within each of the 3 stakeholder groups, fishers, tourism operators, and coastal residents, the prioritization of these 3 threats tended to diverge in 2013, but convergence occurred after bleaching. These results indicate an emergence of areas of agreement both within and across stakeholder groups. Changes in perceptions were likely influenced by high-profile environmental-disturbance events and media representations of threats. Our results provide insights into the plasticity of environmental-threat perceptions and highlight how their convergence in response to major events may create new opportunities for strategic public engagement and increasing support for management.     

The effects of preen oils and soiling on the UV–visible reflectance of carotenoid-pigmented feathers

Plumage coloration, particularly when carotenoid-based, is important in social signaling in birds. Although feather color is a relatively stable trait, individuals may modify it with “cosmetic” substances such as preen oils. In addition, dirt accumulation may influence plumage coloration and further affect signal perception by receivers. Here, we analyze the separate potential effects of preen oils and soil accumulation on the reflectance properties of carotenoid-pigmented feathers across the visual range of most bird species, which includes the ultraviolet (UV). Using the yellow portion of tail feathers of Bohemian waxwings (Bombycilla garrulus), we performed two separate experiments where: (a) preen oils and/or soil were removed, or (b) preen oils (from black-billed magpies Pica pica or eagle owls Bubo bubo) were added. Preen oil addition reduced brightness but increased UV hue and yellow chroma. UV chroma was reduced by the addition of magpie (but not owl) preen oil. Soil accumulation had little effect on plumage reflectance in the UV range but significantly reduced yellow chroma. According to models of avian vision, both of these effects are detectable by birds and biologically meaningful when compared with natural variation between the sexes and age classes. We conclude that preen oil and soil accumulation can significantly affect the UV–visible reflectance of carotenoid-based plumages. As such traits typically advertise individual quality, preening and soiling have the potential to modify the information content of carotenoid-based plumage traits and how these signals are perceived by receivers.     

Effects of bedform migration on nutrient fluxes at the sediment–water interface: a theoretical analysis

Environmental Fluid Mechanics - Nutrient fluxes at the sediment–water interface are essential for water quality and aquatic ecosystems. In this study, a unified expression for the sediment...     

The impact of a cement company’s CSR programmes on the lifestyles of a rural community: a case study in the Ring 1 area in Tuban,East Java,Indonesia

The studies about patterns and impacts of a company’s corporate social responsibility (CSR) programmes on the local communities have been conducted in a number of developed countries. The similar studies, however, were still rarely conducted in developing countries, particularly in Indonesia. This study aims at discussing the impact of the CSR programmes of a cement company on the lifestyles of a rural community in six villages in Tuban district of East Java Province in Indonesia. The study was conducted from January to September 2015, using qualitative data collection and analysis. This study found that the presence of the cement company has made both positive and negative impacts to the rural community. For the positive impacts, we can see the development of infrastructure that makes the villages become more representative; the emergence of new business opportunities, such as food stalls and boarding houses; and the improvement of the quality of human resources through free health care, education, and religious activities. The supports from the cement company, however, have not been distributed equally among the villagers. In addition, we can also see the following negative impacts: the increase of social tense among the villagers due to the tight competition to obtain work in the cement company; the uneasy relation between the local people and the immigrants who work in the cement company; the decrease in the number of people working in agricultural sectors, as most of them have moved or wish to move to the cement company.     

The spider and fly revisited: ploy–counterploy behavior in a unique predator–prey system

Earlier studies have shown that the sarcophagid fly Arachnidomyia lindae is the principal egg-sac predator of the colonial orb-weaving spider Metepeira incrassata, and that risk of egg-sac loss increases with group size. Observations of specialized behaviors for attack (flies) and defense (spiders) suggest that this predator-prey relationship may incorporate elements of ploy and counterploy behavior. Here we explore this relationship in detail and test hypotheses regarding efficacy of attack and defense behaviors. Egg-sac guarding by the spider includes defensive behaviors specific to this fly predator, which were observed during experimental "attacks" with tethered A. lindae, but not with similar presentations of non-predatory Musca domestica. Experimental studies also show that Metepeira incrassata recognizes this predatory fly by airborne cues (i.e., the signature frequency of wing-beats), and can distinguish between this predator and other flies (potential prey) on the basis of wing-beat frequency differences. Removal of female spiders results in a significantly higher probability of unguarded egg-sacs being parasitized, demonstrating the adaptive value of spider defensive behaviors. We also present evidence that A. lindae utilizes a behavioral ploy for circumventing spider guarding behavior (aggressive mimicry - producing vibrations of captured prey in the web), and that Metepeira incrassata, in turn, exhibits a counter-ploy behavior (signal thread cutting) to eliminate this potentially distracting vibratory information. While previous studies have shown that this colonial web-building spider uses a number of general attack-abatement mechanisms against a diversity of predators and parasitoids, results of this study suggest that selection pressures from a highly specialized predator may also result in evolution of predator-specific prey responses.     

The recent 500th anniversary of Leonardo da Vinci’s death: a reminder of his contribution in the field of fluid mechanics

Environmental Fluid Mechanics - In this work, a summary of Leonardo da Vinci’s contribution in the field of fluid mechanics is reported. Some theoretical laws or fluid flows analyzed or drawn...     

The relationship between maternal phenotype and offspring quality: do older mothers really produce the best offspring?

Maternal effects are increasingly recognized as important drivers of population dynamics and determinants of evolutionary trajectories. Recently, there has been a proliferation of studies finding or citing a positive relationship between maternal size/age and offspring size or offspring quality. The relationship between maternal phenotype and offspring size is intriguing in that it is unclear why young mothers should produce offspring of inferior quality or fitness. Here we evaluate the underlying evolutionary pressures that may lead to a maternal size/age-offspring size correlation and consider the likelihood that such a correlation results in a positive relationship between the age or size of mothers and the fitness of their offspring. We find that, while there are a number of reasons why selection may favor the production of larger offspring by larger mothers, this change in size is more likely due to associated changes in the maternal phenotype that affect the offspring size-performance relationship. We did not find evidence that the offspring of older females should have intrinsically higher fitness. When we explored this issue theoretically, the only instance in which smaller mothers produce suboptimal offspring sizes is when a (largely unsupported) constraint on maximum offspring size is introduced into the model. It is clear that larger offspring fare better than smaller offspring when reared in the same environment, but this misses a critical point: different environments elicit selection for different optimal sizes of young. We suggest that caution should be exercised when interpreting the outcome of offspring-size experiments when offspring from different mothers are reared in a common environment, because this approach may remove the source of selection (e.g., reproducing in different context) that induced a shift in offspring size in the first place. It has been suggested that fish stocks should be managed to preserve these older age classes because larger mothers produce offspring with a greater chance of survival and subsequent recruitment. Overall, we suggest that, while there are clear and compelling reasons for preserving older females in exploited populations, there is little theoretical justification or evidence that older mothers produce offspring with higher per capita fitness than do younger mothers.     

Extension of the skin shear stress Li’s relationship to the flat bed

A proper estimation of the skin shear stress τ _s is necessary for a proper evaluation of sediment flux at the sediment–fluid interface. Several empirical formulas of the skin shear stress have been proposed in the literature for rippled bed as function of the factor form η/λ (η and λ are respectively the height and wavelength of the bedform). These formulas express that in the presence of bedform, τ _s is a partition of the total shear stress τ _b . In contrast, when the bottom is flat, τ _s is exactly equal to τ _b . Based on in situ measurements, Li (J Geophys Res 99:791–799, 1994) has proposed a new formula of τ _s depending on u _*/η (u _* is the friction velocity, ${u_{*}=\sqrt{\tau_{b}/\rho}}$ ), but not as a function of η/λ. This formulation appears physically more realistic, but does not cover the flat bottom range. The purpose of this short note is therefore the extension of the Li’s expression to this type of bottom.