Benthic algal biomass and assemblage changes following environmental flow releases and unregulated tributary flows downstream of a major storage

© CSIRO 2014. A large dam reducing the magnitude of flows regulates the Severn River, Australia. Environmental flows (EFs) are designed to increase the magnitude of flow and improve ecological outcomes such as reducing filamentous algal biomass and re-setting algal succession. The effectiveness of EF releases to alter benthic algal assemblages is poorly understood. We examined benthic algal biomass and assemblage structure at two cobble-dominated riffle sites downstream of Pindari Dam, before and after two EFs. Both EFs had discharges of ∼11.6m3 s-1 (velocity of ∼0.9ms -1). Neither EF reduced benthic algal biomass, and sometimes led to increases, with density of some filamentous algae increasing (Stigeoclonium and Leptolyngbya). An unregulated flow from a tributary between the two sites increased discharge to 25.2m3 s-1 (velocity of ∼1.2ms-1), decreasing biomass and density of filamentous algae. The similarity in flow velocities between scouring and non-scouring events suggests that thresholds may exist and/or suspended sediments carried from unregulated tributaries may contribute to reduce algal biomass. Identifying velocities needed to reduce algal biomass are useful. Accordingly, EFs with flow velocities ∼1.2ms-1 may achieve this in river cobble-dominated riffle sections dominated by filamentous algae. Lower flow velocities of <0.9ms-1 may result in no change or an increase in filamentous algae

Anti-Human Tissue Factor Antibody Ameliorated Intestinal Ischemia Reperfusion-Induced Acute Lung Injury in Human Tissue Factor Knock-In Mice

BACKGROUND: Interaction between the coagulation and inflammation systems plays an important role in the development of acute respiratory distress syndrome (ARDS). Anti-coagulation is an attractive option for ARDS treatment, and this has promoted development of new antibodies. However, preclinical trials for these antibodies are often limited by the high cost and availability of non-human primates. In the present study, we developed a novel alternative method to test the role of a humanized anti-tissue factor mAb in acute lung injury with transgenic mice. METHODOLOGY/PRINCIPAL FINDINGS: Human tissue factor knock-in (hTF-KI) transgenic mice and a novel humanized anti-human tissue factor mAb (anti-hTF mAb, CNTO859) were developed. The hTF-KI mice showed a normal and functional expression of hTF. The anti-hTF mAb specifically blocked the pro-coagulation activity of brain extracts from the hTF-KI mice and human, but not from wild type mice. An extrapulmonary ARDS model was used by intestinal ischemia-reperfusion. Significant lung tissue damage in hTF-KI mice was observed after 2 h reperfusion. Administration of CNTO859 (5 mg/kg, i.v.) attenuated the severity of lung tissue injury, decreased the total cell counts and protein concentration in bronchoalveolar lavage fluid, and reduced Evans blue leakage. In addition, the treatment significantly reduced alveolar fibrin deposition, and decreased tissue factor and plasminogen activator inhibitor-1 activity in the serum. This treatment also down-regulated cytokine expression and reduced cell death in the lung. CONCLUSIONS: This novel anti-hTF antibody showed beneficial effects on intestinal ischemia-reperfusion induced acute lung injury, which merits further investigation for clinical usage. In addition, the use of knock-in transgenic mice to test the efficacy of antibodies against human-specific proteins is a novel strategy for preclinical studies

The Extended Cleavage Specificity of Human Thrombin

Thrombin is one of the most extensively studied of all proteases. Its central role in the coagulation cascade as well as several other areas has been thoroughly documented. Despite this, its consensus cleavage site has never been determined in detail. Here we have determined its extended substrate recognition profile using phage-display technology. The consensus recognition sequence was identified as, P2-Pro, P1-Arg, P1′-Ser/Ala/Gly/Thr, P2′-not acidic and P3′-Arg. Our analysis also identifies an important role for a P3′-arginine in thrombin substrates lacking a P2-proline. In order to study kinetics of this cooperative or additive effect we developed a system for insertion of various pre-selected cleavable sequences in a linker region between two thioredoxin molecules. Using this system we show that mutations of P2-Pro and P3′-Arg lead to an approximate 20-fold and 14-fold reduction, respectively in the rate of cleavage. Mutating both Pro and Arg results in a drop in cleavage of 200–400 times, which highlights the importance of these two positions for maximal substrate cleavage. Interestingly, no natural substrates display the obtained consensus sequence but represent sequences that show only 1–30% of the optimal cleavage rate for thrombin. This clearly indicates that maximal cleavage, excluding the help of exosite interactions, is not always desired, which may instead cause problems with dysregulated coagulation. It is likely exosite cooperativity has a central role in determining the specificity and rate of cleavage of many of these in vivo substrates. Major effects on cleavage efficiency were also observed for residues as far away as 4 amino acids from the cleavage site. Insertion of an aspartic acid in position P4 resulted in a drop in cleavage by a factor of almost 20 times

Carnivore Translocations and Conservation: Insights from Population Models and Field Data for Fishers (Martes pennanti)

Translocations are frequently used to restore extirpated carnivore populations. Understanding the factors that influence translocation success is important because carnivore translocations can be time consuming, expensive, and controversial. Using population viability software, we modeled reintroductions of the fisher, a candidate for endangered or threatened status in the Pacific states of the US. Our model predicts that the most important factor influencing successful re-establishment of a fisher population is the number of adult females reintroduced (provided some males are also released). Data from 38 translocations of fishers in North America, including 30 reintroductions, 5 augmentations and 3 introductions, show that the number of females released was, indeed, a good predictor of success but that the number of males released, geographic region and proximity of the source population to the release site were also important predictors. The contradiction between model and data regarding males may relate to the assumption in the model that all males are equally good breeders. We hypothesize that many males may need to be released to insure a sufficient number of good breeders are included, probably large males. Seventy-seven percent of reintroductions with known outcomes (success or failure) succeeded; all 5 augmentations succeeded; but none of the 3 introductions succeeded. Reintroductions were instrumental in reestablishing fisher populations within their historical range and expanding the range from its most-contracted state (43% of the historical range) to its current state (68% of the historical range). To increase the likelihood of translocation success, we recommend that managers: 1) release as many fishers as possible, 2) release more females than males (55–60% females) when possible, 3) release as many adults as possible, especially large males, 4) release fishers from a nearby source population, 5) conduct a formal feasibility assessment, and 6) develop a comprehensive implementation plan that includes an active monitoring program

The influence of flow on benthic assemblages in the Severn River, New South Wales, Australia

University of Technology, Sydney. Faculty of Science.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. The hardcopy may be available for consultation at the UTS Library.NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- The effects of flow regulation and to a lesser extent flow restoration on stream ecosystems are increasingly well documented and studied internationally. Australian stream ecosystems have changed in response to flow alteration, but little is known how they might change should flow volumes and variability increase through the introduction of environmental flows. The Severn River is an upland river in northern NSW, Australia. It is a tributary of the Border Rivers sub-catchment, a part of the Murray–Darling River System. Pindari Dam on the Severn River, which can store 312 GL, regulates its flow. Typically, high flows to meet irrigation demands (up to 1,000 ML d⁻¹) occur in warmer months (October-March). Unlike many other regulated rivers that experience higher flows than pre-regulated conditions in summer, the seasonality of high flows in the Severn River has not been reversed. However, natural flow variation is lost as releases of ~10 ML d⁻¹ are discharged at other times. A Water Sharing Plan (WSP) governs management of flows in the Severn River including an environmental flow release from Pindari Dam. Seasonal water chemistry, benthic algal and macroinvertebrate assemblage data were collected at sites on the regulated Severn and unregulated Mole and Dumaresq Rivers. Sites differed in the level of hydrological variation. Flows in the Severn River never ceased and were relatively stable, compared to unregulated sites on the Mole and Dumaresq Rivers that experienced high flows after rainfall and no flow periods when base flows ceased. Severn River sites had a higher abundance of benthic algae (including filamentous algae) but lower algal diversity than that at sites of the Mole and Dumaresq Rivers. Macroinvertebrate densities in all rivers were comparable; however, regulated sites were typically characterised by a higher density of filter feeding macroinvertebrates. Two environmental flow scenarios designed to reduce the density of benthic algae were trialled in the Severn River at Glenora Bridge and Ashford Bridge. Flows that peaked at ~1,000 ML d⁻¹ (velocity of ~0.9 m s⁻¹) increased the density of benthic algae particularly filamentous algae such as Stigeoclonium and Leptolyngbya. A third flow event from an unregulated tributary with its confluence between sites, increased flows to 2,180 ML d⁻¹ (velocity of ~1.2 m s⁻¹), which reduced chlorophyll a and filamentous algal abundance. The similarity in flow velocities suggests that suspended sediments in the unregulated tributary flow may be important in reducing of algal biomass. Benthic algal biomass accrual (measured as chlorophyll a concentration) and community changes were determined after artificial scouring of cobbles. Algal biomass and diversity on scoured cobbles took two weeks to return to levels similar to that on the reference cobbles in summer and took five weeks in winter. Chlorophyll a concentrations on cobbles in summer were initially 0.24 ± 0.06 mg m⁻², but by day 16 had increased to 9.74 ± 1.97 mg m⁻² and were no longer significantly different (P >0.05) from that on reference cobbles. Chlorophyll a concentrations in winter were initially 0.47 ± 0.13 mg m⁻², but by day 37 increased to 44.7 ± 10.9 mg m⁻² and were no longer significantly different (P >0.05) from that on reference cobbles. Peak chlorophyll a concentration accrual during summer and winter was 1.64 and 2.63 mg m d⁻¹, respectively. Diatoms such as Cocconeis, Synedra, and Fragilaria dominated the early succession assemblages, while an abundance of the filamentous green alga Stigeoclonium indicated a late succession assemblage. The Severn River does not experience natural flow variations and periods of drying due to dam operation, although naturally they would have occurred. Summer and winter experiments to determine the response of algal assemblages to drying for 1, 2, 4 or 9 d and re-immersion periods of 13 or 28 d were performed to determine if drying could be used to reduce biomass and re-set algae to early stage assemblages. In winter, drying reduced the abundance of green algae, including Stigeoclonium and other filamentous algal taxa. Chlorophyll a concentrations declined from 22.92 ± 4.71 mg m⁻² to 4.85 ± 0.42 mg m⁻². In summer, drying promoted the growth of Cocconeis and chlorophyll a concentrations were stable at 2.33 ± 0.36 mg m⁻². A grazer-exclusion experiment was conducted to determine macroinvertebrate grazing preferences for early and late succession algal assemblages. Grazers did not prefer the early succession algal assemblages as expected; instead, more grazers were found on late succession cobbles. Treatments with grazing increased chlorophyll a concentrations (from 9.69 ± 0.69 mg m⁻² to 13.15 ± 2.46 mg m⁻²) more than grazer excluded cobbles. Similarly, mean overall abundance (as cells cm⁻²) was greater on grazed cobbles (1030.4 ± 38.7) than cobbles without grazing (881.9 ± 19.2). The filamentous green alga Oedogonium and the chain-forming diatom Fragilaria decreased in abundance in the presence of grazing. This study answered important research questions in the Severn River, focussed on flow management and the effectiveness of proposed environmental flows from Pindari Dam as gazetted in the Border Rivers WSP. Current environmental flow volumes will not be effective in reducing algal growths and will probably increase growths. Environmental flow velocities >1.2 m s⁻¹ should be more effective at reducing algal growths however regrowth to original conditions in warmer times may occur within several weeks. Drying periods could be used to better simulate natural conditions. After drying, benthic algal assemblages had less regrowth of filamentous algae taxa. Because of the work carried out in the study, it is possible that the findings and collected knowledge regarding the effects of flow on benthic algal assemblages contained herein will be used in other regulated streams locally, nationally and internationally. Particularly when increases to flow downstream of a water storage are proposed

The Fish Health Risk Indicator: linking water quality and river flow data with fish health to improve our predictive capacity around fish death events

Severe drought conditions contributed to three mass fish mortality events in the Darling River near Menindee, part of the Murray–Darling Basin, Australia, during the summer of 2018–19. An independent assessment recommended the need for improved modelling approaches to identify when sections of rivers may be more susceptible to fish kill events. We present a geographic information system (GIS)-based tool that combines meteorological forecasts with river flow and algal biomass datasets to identify river reaches where additional stresses on fish health may produce an increased risk of mass fish deaths. At present the tool is still in development and will require the addition of extra datasets and testing using historical datasets to further validate its accuracy. Despite the tool being in its development stage, the decision support tool has been widely accepted and provides natural resource managers with a rapid way to understand and communicate risks to fish health, supporting improved water management options across the Murray–Darling Basin that may ultimately help reduce the frequency and severity of large-scale fish mortality events.</jats:p

Succession and accrual of benthic algae on cobbles of an upland river following scouring

Flow releases from dams can be used to scour benthic algae, simulating the effects of natural spates and maintaining benthic algae in an early successional stage for increased grazer palatability. The timing of releases needs to consider the natural periodicity of flow events and the speed of regrowth and community succession changes. We studied benthic algal regrowth and succession using manipulative field experiments during summer and winter in the upland regulated Severn River, New South Wales, Australia. Benthic algal biomass accrual as chlorophyll a and community changes were determined after artificially scoured cobbles were returned to the river. In summer, algal biomass and diversity on scoured cobbles took 2 weeks to return to levels similar to reference cobbles and 5 weeks in winter. Chlorophyll a during summer was initially 0.24 ± 0.06 mg m-2 on scoured cobbles, but by day 16 had increased to 9.74 ± 1.97 mg m-2 and was no longer significantly different from reference cobbles. In winter, chlorophyll a was initially 0.47 ± 0.13 mg m-2 on scoured cobbles, but by day 37 had increased to 44.7 ± 10.9 mg m-2 and was no longer significantly different from reference cobbles. Peak chlorophyll a accrual during summer and winter was 1.64 and 2.63 mg m-2 d-1, respectively. Early succession in both experiments was dominated by diatoms such as Cocconeis, Synedra, and Fragilaria. A proliferation of the filamentous green alga Stigeoclonium was indicative of a late succession community. The implications for flow management based on resetting of benthic algae by scouring in riffle reaches of rivers are discussed. © International Society of Limnology 2012