Fish and flows: Abiotic drivers influence the recruitment response of a freshwater fish community throughout a regulated lotic system of the Murray-Darling Basin,Australia

1. Fish assemblages in dryland rivers have life-history strategies that have evolved in response to environmental conditions and triggers, particularly water temperatures and flow regimes. The regulation of rivers through the construction of dams, weirs and other water diversion structures has altered natural flow regimes and the associated ecological processes of river systems worldwide.
2. Over a 3-year period, using standardized fish sampling and daily otolith ageing, the recruitment of eight freshwater fish species was monitored in response to various abiotic drivers, including hydrology and water temperatures, throughout the Macquarie River, a large regulated river system of the Australian Murray-Darling Basin.
3. A data-driven statistical classification system is provided that groups species into reproductive guilds, based on their recruitment response to hydrology and water temperature, specifically designed for use in environmental flow management.
4. The eight species were grouped into three distinct reproductive guilds that showed similar recruitment responses to the abiotic drivers. Murray-Darling rainbowfish, Murray cod, and eel-tailed catfish were considered as a single guild, characterized by seasonal recruitment during a relatively narrow thermal window under low to moderate stable discharges. The second group included common carp, bony herring, and golden perch, which recruited primarily in association with larger flow events. Un-specked hardyhead and Australian smelt formed a more differentiated guild, recruiting over a broad range of temperatures and discharges. Limitations associated with using a reproductive guild approach to simplify water management are discussed.
5. This study highlighted important relationships among hydrology, water temperatures, and successful recruitment that can, in turn, be used to inform development of adaptive flow management plans and effective use of environmental water for the conservation management of native fish communities. Important considerations in the design of studies that aim to examine relationships between recruitment and abiotic drivers are also discussed.

     

Bryophytes as potential indicators of forest integrity

Forest integrity has been proposed as one conservation endpoint that integrates desirable characteristics such as natural biodiversity, stand structure and continuity. Although its defining criteria are still under discussion, any surrogates must effectively represent or predict their status, and be easier to measure than the criteria themselves. Bryophytes have been proposed as such surrogates, because they are important components of forest integrity, and considerable research indicates that some groups are sensitive to the changes associated with specific forest management regimes. The objectives of this paper are (1) to review the issues in determining indicators of forest integrity, including desirable qualities in such indicators, (2) to review the state of knowledge concerning bryophytes as components of forest integrity (i.e. their responses to forest management practices), and (3) to assess bryophytes as potential indicators of forest integrity, in terms of both qualities desirable in indicators and our understanding of bryophyte response patterns. Although bryophytes possess some characteristics that suggest potential indicator value, many challenges prevent their reliable application. I highlight key areas in which research is required to identify operational bryophyte indicators of forest integrity. Along with a standardized protocol to select and calibrate such indicators, we urgently require strategic research to compile data on undisturbed reference forests on which to base selection of endpoints; species-specific ecological tolerances, with consideration of complex interactions; mechanisms of response to disturbance, with consideration of temporal aspects; population viability thresholds; and recruitment effects on community assembly. Whether we succeed in finding bryophyte indicators of forest integrity, this research would also provide the data to monitor and interpret the integrity of the bryophyte community.     

Radiative absorption enhancements due to the mixing state of atmospheric black carbon

Atmospheric black carbon (BC) warms Earth's climate, and its reduction has been targeted for near-term climate change mitigation. Models that include forcing by BC assume internal mixing with non-BC aerosol components that enhance BC absorption, often by a factor of ~2; such model estimates have yet to be clearly validated through atmospheric observations. Here, direct in situ measurements of BC absorption enhancements (E(abs)) and mixing state are reported for two California regions. The observed E(abs) is small-6% on average at 532 nm-and increases weakly with photochemical aging. The E(abs) is less than predicted from observationally constrained theoretical calculations, suggesting that many climate models may overestimate warming by BC. These ambient observations stand in contrast to laboratory measurements that show substantial E(abs) for BC are possible.     

Fishing, trophic cascades, and the process of grazing on coral reefs

Since the mass mortality of the urchin Diadema antillarum in 1983, parrotfishes have become the dominant grazer on Caribbean reefs. The grazing capacity of these fishes could be impaired if marine reserves achieve their long-term goal of restoring large consumers, several of which prey on parrotfishes. Here we compare the negative impacts of enhanced predation with the positive impacts of reduced fishing mortality on parrotfishes inside reserves. Because large-bodied parrotfishes escape the risk of predation from a large piscivore (the Nassau grouper), the predation effect reduced grazing by only 4 to 8%. This impact was overwhelmed by the increase in density of large parrotfishes, resulting in a net doubling of grazing. Increased grazing caused a fourfold reduction in the cover of macroalgae, which, because they are the principal competitors of corals, highlights the potential importance of reserves for coral reef resilience.     

Efficacy of vaporised ethyl formate/carbon dioxide formulation against stored‐grain insects: effect of fumigant concentration,exposure time and two grain temperatures

BACKGROUND: The ethyl formate/carbon dioxide (CO₂) formulation Vapormate? is a rapid‐acting fumigant being developed for the control of stored‐grain insects. The effects have been investigated of concentration, exposure times of 1, 3, 24 and 72 h and two grain temperatures, 15 and 25 °C, on its efficacy against mixed‐stage cultures of Sitophilus oryzae (L.) Tribolium castaneum (Herbst) and strongly phosphine‐resistant Rhyzopertha dominica (F.) strain QRD569. RESULTS: High mortalities (≥92%) of mixed‐stage cultures of all three species were obtained when grain was fumigated with the formulation (193 g m^?3 ethyl formate) for 1 h. Complete control of R. dominica QRD569 and T. castaneum was achieved with 63 and 76 g m^?3 ethyl formate respectively, with exposure for 24 h, whereas mean mortality of S. oryzae was 86% under the same conditions. Mortalities of S. oryzae juvenile stages were significantly lower than adults under the conditions tested, which was due to pronounced tolerance of mid‐stage pupae to the fumigant. Reducing grain temperature from 25 to 15 °C had no effect on insect mortality. CONCLUSION: Ethyl formate/CO₂ formulation is highly effective against stored‐grain insects over a range of concentrations and exposure times. Efficacious fumigations were conducted in as little as 1 h, and a strongly phosphine‐resistant R. dominica strain was readily controlled with the fumigant. Copyright © 2009 CSIRO, Australia. Published by John Wiley & Sons, Ltd     

Effects of age and allergen exposure on transepidermal water loss in a house dust mite-sensitized beagle model of atopic dermatitis

Transepidermal water loss (TEWL) was measured as assessment of barrier function in house dust mite-sensitized atopic ( n  = 24) and normal ( n  = 21) beagle dogs before and after allergen challenge. Dogs of the two groups were matched for age and housed in the same environment. Ten sites were evaluated including both areas of high and low predisposition to atopic lesion formation. On day 0 (before allergen exposure) and day 3 (3 days after allergen exposure), TEWL measurements were taken using an open-chamber evaporimeter. On day 0, significant differences (one-way ANOVA) were found between normal and atopic dogs in the chin, pinna, periocular region, axilla, antebrachium and thorax. Within the atopic group, a significant increase (one-way ANOVA) in TEWL was found in the axilla on day 3. Such a difference was particularly marked in young dogs (chin, pinna, axilla, antebrachium and groin). Within the normal group, allergen challenge did not change TEWL except for the chin. When atopic and nonatopic sites were compared within the atopic group, a significant difference in TEWL was found on day 0. A two-way ANOVA showed a significant effect of site, a significant effect of time but no site × time (i.e. allergen exposure) interaction. It is concluded that the house dust mite-sensitized atopic beagle dogs used in this study have altered barrier function in 'atopic' areas and that such differences are more evident in young individuals and are aggravated by allergen exposure.