Safety in numbers and the spatial scaling of density-dependent mortality in a coral reef fish

In coral reef fishes, density-dependent population regulation is commonly mediated via predation on juveniles that have recently settled from the plankton. All else being equal, strong density-dependent mortality should select against the formation of high-density aggregations, yet the juveniles of many reef fishes aggregate. In light of this apparent contradiction, we hypothesized that the form and intensity of density dependence vary with the spatial scale of measurement. Individual groups might enjoy safety in numbers, but predators could still produce density-dependent mortality at larger spatial scales. We investigated this possibility using recently settled juvenile bluehead wrasse, Thalassoma bifasciatum, a small, aggregating reef fish. An initial caging experiment demonstrated that juvenile bluehead wrasse settlers suffer high predation, and spatial settlement patterns indicated that bluehead wrasse juveniles preferentially settle in groups, although they are also found singly. We then monitored the mortality of recently settled juveniles at two spatial scales: microsites, occupied by individual fish or groups of fish and separated by centimeters, and sites, consisting of approximately 2400-m2 areas of reef and separated by kilometers. At the microsite scale, we measured group size and effective population density independently and found that per capita mortality decreased with group size but was not related to density. At the larger spatial scale, however, per capita mortality increased with settler density. This shift in the form of density dependence with spatial scale could reconcile the existence of small-scale aggregative behavior typical of many reef fishes with the population-scale density dependence that is essential to population stability and persistence.     

Direct and indirect methods for chromium identification in industrial wastes

The examinations of selected wastes and stream sediments from the vicinity of a chemical plant by sequential extraction procedures and direct methods, SEM/EDX and XRD, were carried out in order to identify the different forms of chromium, particularly as they are released to potential mobility. The results show that the top and bottom waste samples contain 37,756 and 53,650 μg g¹ Cr, respectively, but about 7% and 2% of the total chromium type Cr(VI). The chemical extraction results show that the mobility of Cr in the upper part of the waste pile is significantly higher than in the bottom section; the exchangeable form of Cr accounts for 25% and < 1%, respectively, the last one irrespective of redox conditions. About 50% of Cr is associated with the reducible fraction of the top waste, and similar with the residual fraction in the bottom waste. Oxidation of the bottom waste shift some portion of Cr from residual to the moderately reducible fraction. The major Cr-forms in the river sediments are compounded with Fe-oxides. The < 2 μm size fraction of the selected sediment sample, particular enriched in chromium contained up to 73,000 μg g¹ Cr with about 95% of this in the moderately reducible fraction, predominantly bound with oxyhydroxides. SEM/EDX and XRD analysis of wastes and river sediment indicate that the main insoluble Cr-phase is ferroan — (Mg, Fe) (Cr, Al)²O⁴ which would be dissolved mainly in the residual fraction.     

Spawning and development in <Emphasis Type="Italic">Osedax</Emphasis> boneworms (Siboglinidae,Annelida)

We report observations on spawning and early development in bone-eating worms of the genus Osedax. Individual females of Osedax rubiplumus were observed at 1820 m depth freely spawning hundreds of oocytes, and females of an undescribed species, Osedax “orange collar”, were observed spawning in laboratory aquaria. Cytological and molecular analysis of the spawned oocytes of two Osedax species revealed no evidence for the bacterial endosymbionts that the female worms require for their nutrition, suggesting that the bacteria must be acquired later from the environment, as they are in other siboglinids. Individual O. “orange collar” females released an average of 335 (±130) eggs per day, but the number of oocytes spawned per day varied greatly, suggesting that not all the females spawned daily. Fertilization rates of the spawned oocytes varied from 0 to 100%, though most females showed nearly 100% fertilization rates. Oocytes spawned in the laboratory at 4–6°C were negatively buoyant. If fertilized, these oocytes extruded polar bodies and then after at least four hours cleaved unequally. Subsequent cleavages occurred in a spiral pattern at roughly 2-h intervals, resulting in free-swimming trochophore larvae after 24 h. These lecithotrophic trochophores swam for 9–16 days before settling with several hooked chaetae, similar to those of dwarf Osedax males. The larval life span of the Osedax species studied in the laboratory appears to be shorter than in closely related Vestimentifera. Osedax rubiplumus, on the other hand, has much larger oocytes and so may have greater dispersal potential than these other Osedax species. The high fecundity and apparently continuous reproduction of Osedax boneworms permits the opportunistic exploitation of sunken vertebrate bones. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Aggressive mating as a tragedy of the commons in the water strider Aquarius remigis

The tragedy of the commons usually refers to the overexploitation of resources such as food or water. Here, we show in a laboratory study that competition among males for females can also result in a tragedy of the commons’ situation. Male water striders (Aquarius remigis) vary widely in their aggressiveness toward pursuing females. The most aggressive males prevent females from feeding and cause them to leave the water surface, where they are unavailable to all males. Groups of nonaggressive males are collectively three times more fit than groups of hyperaggressive males, but hyperaggressive males are more successful than nonaggressive males within mixed groups. This is the classic tragedy of the commons’ situation, and it is likely to occur in many species that exhibit sexual conflict. We have also shown that individual differences in male aggression are stable across time and are not influenced by food or light regime, although all individuals become nonaggressive in the presence of fish predators.     

Organisational resilience following the Darfield earthquake of 2010

This paper presents the preliminary findings of a study on the resilience and recovery of organisations following the Darfield earthquake in New Zealand on 4 September 2010. Sampling included organisations proximal and distal to the fault trace, organisations located within central business districts, and organisations from seven diverse industry sectors. The research captured information on the challenges to, the impacts on, and the reflections of the organisations in the first months of recovery. Organisations in central business districts and in the hospitality sector were most likely to close, while organisations that had perishable stock and livestock were more heavily reliant on critical services. Staff well‐being, cash flow, and customer loss were major concerns for organisations across all sectors. For all organisations, the most helpful factors in mitigating the effects of the earthquake were their relationship with staff members, the design and type of buildings, and critical service continuity or swift reinstatement of services.     

The Effects of Liming On Soil Chemistry at Loch Fleet,Scotland

An experiment to investigate how the water quality of acid lakes can be improved by liming the surrounding catchment was begun at Loch Fleet, Scotland in 1984. the effects on the soils of three sectors of the catchment where limestone was added in 1986 are reported here, following analysis of soils sampled in 1987, 1988 and 1991. the effect of the lime on soil chemistry was still evident in 1991, with about 15% of free lime remaining in the hydrochemical reaction zone of sectors IV and VI and nearly 50% in sector VII. However, this free lime appeared to be dissolving too slowly to maintain large amounts of exchangeable calcium in the soils, indicating that the treatment is starting to become less effective. the fall in the mean exchangeable calcium in the reaction zone between 1988 and 1991 was mirrored by a drop in mean soil pH over the 5 years post-liming from 6.1 to 5.6 on sector IV and from 5.9 to 5.4 on sector VI, whereas mean pH remained constant at about 6.0 in the limed areas of sector VII. Using soil data to predict longevity suggests that the exchangeable calcium remaining on the catchment at the end of 1991 will maintain target water quality in the loch until sometime during 1994. the soil pH is likely to fall to between 5.2 and 5.3 by this time. If the region of hydrochemical reaction is assumed to extend to a depth of 20 cm rather than 5 cm, target water quality is predicted to be maintained until the end of 1995. When the free lime remaining on the catchment is included as a source of acid neutralising capacity, calculations show that treatment may remain effective until around the year 2000.     

Effects of catalytic hydrogenation on coal liquids which exhibit microbial mutagenic activity

An interdisciplinary strategy is outlined for characterizing the disposition of bioactive (toxic, teratogenic, mutagenic, and/or carcinogenic) materials in coal‐derived hydrocarbon liquids during upgrading processing. Engineering input is required to select representative PDU and pilot‐scale samples and appropriate processing schemes and conditions for upgrading experiments to ensure reliable extrapolation of results to demonstration and commercial scale. Biology expertise is required to perform and interpret short‐term in vitro cellular assays and whole‐animal toxicity and carcinogenesis testing on raw and upgraded samples. Chemical separation and identification of active classes and components in the samples aid in interpreting bioactivity results and in quantifying effects of various upgrading processes and conditions. The end result will be a data base for reliably assessing and addressing potential occupational and environmental safety and health concerns associated with upgraded coal‐derived liquids.

An example of the value of this interdisciplinary approach is given by work performed on generically representative raw and hydrotreated SRC‐II gas oil samples. Biological and chemical characterization indicates significant loss of bioactivity during hydrotreatment, with one postulated mechanism being removal of primary amine groups from multi‐ring aromatic compounds.     

Network position: a key component in the characterization of social personality types

In recent years, animal social interactions have received much attention in terms of personality research (e.g. aggressive or cooperative interactions). However, other components of social behaviour such as those describing the intensity, frequency, directedness and individual repeatability of interactions in animal groups have largely been neglected. Network analysis offers a valuable opportunity to characterize individual consistency of traits in labile social groups and therein provide novel insights to personality research in ways previously not possible using traditional techniques. Should individual network positions be consistently different between individuals under changing conditions, they might reflect expressions of an individual's personality. Here, we discuss a conceptual framework for using network analyses to infer the presence of individual differences and present a statistical test based on randomization techniques for testing the consistency of network positions in individuals. The statistical tools presented are useful because if particular individuals consistently occupy key positions in social networks, then this is also likely to have consequences for their fitness as well as for that of others in the population. These consequences may be particularly significant since individual network position has been shown to be important for the transmission of diseases, socially learnt information and genetic material between individuals and populations.     

Energy expenditure and food consumption of foraging Imperial cormorants in Patagonia, Argentina

Energy management during the breeding season is crucial for central place foragers since parents need to feed themselves and their offspring while being spatially and temporally constrained. In this work, we used overall dynamic body acceleration as a measure of activity and also to allude to the foraging energy expenditure of breeding Imperial cormorants Phalacrocorax atriceps. We also analyzed how changes in the time or energy allocated to different activities affected the foraging trip energy expenditure and estimated the daily food requirements of the species. Birds spent 42 % of the total energy flying to and from the feeding areas and 16 % floating at sea. The level of activity underwater was almost 1.5 times higher for females than for males. The most expensive diving phase in terms of rate of energy expenditure was descending though the water column. The total foraging trip energy expenditure was particularly sensitive to variation in the amount of time spent flying. During the breeding season, adult cormorants breeding along the Patagonian coast would consume approximately 10,000 tons of food.     

Metabolism of shallow and deep-sea benthic crustaceans and echinoderms in Hawaii

Little is known about the metabolism of deep-living, benthic invertebrates, despite its importance in estimating energy flow through individuals and populations. To evaluate the effects of depth and broad taxonomic group/locomotory mode, we measured the respiration rates of 25 species of benthic decapod crustaceans and 18 species of echinoderms from the littoral zone to the deep slope of Hawaii. Specimens were collected by hand, trap, or submersible and maintained in the laboratory at temperatures close to ambient temperatures recorded at the time of collection. After acclimatization to laboratory conditions, oxygen consumption was measured for each individual in closed chambers. Overall, crustaceans had higher metabolic rates than echinoderms, and within the crustaceans, caridean shrimps had higher rates than crabs and lobsters. These differences are probably related to locomotory mode and general levels of activity. At in situ environmental temperatures, metabolic rates of deeper-living invertebrates are much lower than those of shallower living species, but this decline is explained by changes in temperature. When the data were compared with similar data sets collected off California and in the Mediterranean, Hawaiian crabs, lobsters, and echinoderms had lower metabolic rates than similar species in the other regions after adjustments for temperature were made. Some of these differences could be methodological. Regional food web models should use broad taxonomic groupings and region-specific data when possible.