Invasive species in the Anthropocene: Help or hindrance?

Under predicted climate change scenarios many parts of the world will be hotter. Higher temperature extremes present significant physiological challenges to ectothermic freshwater species that cannot regulate body temperature. Willows (Salix spp.) are highly invasive deciduous northern hemisphere shrubs and trees that have colonised riparian zones of southern hemisphere streams. Non-native willows are criticised for their high consumption of water and their capacity to form dense monostands along the margins and within waterways that limit light to streams in summer, alter the timing and quality of allochthonous inputs and modify ecosystem function. As such, governments invest heavily in the removal of willows from streams in order to preserve ecosystem integrity. Although detrimental effects of non-native willows are well documented, little attention has been focussed on consideration of potential ecosystem services that non-native willow infestation may provide under predicted climate warming. Here, we use a case study to illustrate that shading by non-native willows can provide thermal refugia for temperature sensitive endemic taxa and we provide a holistic approach to non-native willow removal that may provide benefits to aquatic species amid changing climate. We present a simple decision matrix for prioritising willow removal activities that may be applied to other invasive species and we discuss traditional views of invasive species management and river restoration and their relevance in a rapidly warming world. The concepts we discuss are of immediate relevance to environmental managers challenged with maintaining and restoring ecosystems that are rapidly changing in structure and function in response to climate warming.

A case report of transverse testicular ectopia with testicular microlithiasis.

Transverse testicular ectopia is a rare congenital anomaly in which both testes migrate along the same inguinal canal toward the scrotum. This report describes the case of the rarest form of transverse testicular ectopia in a 23-year-old man with coexisting testicular microlithiasis in one of the two testes as diagnosed on sonography and confirmed on MRI. We are unaware of any previous published reports of this association. Although the etiology of both conditions is debatable, each is believed to be associated with an increased risk of testicular malignancy, and this poses a dilemma for the future management of this patient.

Patient-specific risk of undetected malignant disease after investigation for haematuria, based on a 4-year follow-up.

OBJECTIVES: • To estimate the diagnostic accuracy of a guidelines-based haematuria clinic protocol by measuring the incidence of undetected malignancy during a follow-up period. • To estimate an individual's post-test risk of having undetected malignancy using the protocol likelihood ratio and the population prevalence of disease. METHODS: • Data were collected prospectively on a cohort of 4020 consecutive patients who were referred to a 'one-stop' haematuria clinic between 1998 and 2003. • All patients had a plain radiograph taken and underwent ultrasonography and flexible cystoscopy as a part of 'first-line' investigation. • Intravenous urography was performed where indicated after abnormal first-line tests or in patients with persistent haematuria where no abnormality had been detected. • Records of the initial 687 participants from the first year of the study were reviewed 4 years after the original consultation. Missed diagnoses of urinary tract malignancy were recorded and sensitivities, likelihood ratios and the post-test probability of missing all disease and upper tract malignancy were calculated. RESULTS: • As previously reported, the overall prevalence of malignant disease was 12.1% (18.9% for macroscopic haematuria compared with 4.8% for microscopic haematuria). • The records of the first year's cohort of patients (N = 687) were analysed 4 years after their original consultation and 10 potentially 'missed' tumours were identified. • The sensitivity of the protocol was 90.9% for the detection of all urinary tract malignancy (95% CI, 82.4 to 95.5) and 71% for upper tract tumours alone (95% CI, 45.4-88.3). The latter improves to 78.6% (95% CI, 52.4-92.4) with the addition of further upper tract testing. • The probability of missing malignant disease overall was 1.7% (95% CI, 0.95-3.04) but this rose sharply to >4% for males over 60 with macroscopic haematuria. • For those with non-visible haematuria, the percentage probability of missed malignant disease was less than 1%. CONCLUSIONS: • The haematuria clinic protocol described is robust but it is not infallible. • The risk of missing malignant disease in the higher risk groups identified in the study is much greater than previous studies would suggest. • If additional upper tract testing or interval follow-up were to be recommended, it could be rationally targeted at these groups, given the measurable risk shown here.

2019-2020 Bushfire impacts on sediment and contaminant transport following rainfall in the Upper Murray River catchment.

During the 2019-2020 Australian bushfire season, large expanses (~47%) of agricultural and forested land in the Upper Murray River catchment of southeastern (SE) Australia were burned. Storm activity and rainfall following the fires increased sediment loads in rivers, resulting in localized fish kills and widespread water-quality deterioration. We collected water samples from the headwaters of the Murray River for sediment and contaminant analysis and assessed changes in water quality using long-term monitoring data. A robust runoff routing model was used to estimate the effect of fire on sediment loads in the Murray River. Peak turbidity in the Murray River reached values of up to 4200 nephelometric turbidity units (NTU), shown as pitch-black water coming down the river. The increase in suspended solids was accompanied by elevated nutrient concentrations during post-bushfire runoff events. The model simulations demonstrated that the sediment load could be five times greater in the first year after a bushfire than in the prefire condition. It was estimated that Lake Hume, a large reservoir downstream from fire-affected areas, would receive a maximum of 600 000 metric tonnes of sediment per month in the period immediately following the bushfire, depending on rainfall. Total zinc, arsenic, chromium, nickel, copper, and lead concentrations were above the 99% toxicant default guideline values (DGVs) for freshwater ecosystems. It is also likely that increased nutrient loads in Lake Hume will have ongoing implications for algal dynamics, in both the lake and the Murray River downstream. Information from this study provides a valuable basis for future research to support bushfire-related policy developments in fire-prone catchments and the mitigation of postfire water quality and aquatic ecosystem impacts. Integr Environ Assess Manag 2021;17:1203-1214. © 2021 Commonwealth of Australia. Integrated Environmental Assessment and Management © 2021 Society of Environmental Toxicology & Chemistry (SETAC).

Managed floodplain inundation maintains ecological function in lowland rivers.

Managed environmental flows are one mechanism by which managers may restore carbon dynamics, diversity and ecological function of rivers affected by anthropogenic activities. Empirical studies that quantify such interactions in detail are few, so we measured the amounts of dissolved organic carbon, nutrients, algae and invertebrates in the main river channel following a managed environmental flow that inundated an adjacent floodplain forest. Dissolved organic carbon (DOC), seston carbon, total nitrogen (TN), and chlorophyll-a (chl-a) concentrations were greatly increased downstream. The net yield of DOC, seston carbon, TN and chl-a from the floodplain peaked at approximately 100, 50, 5 and 0.1 t d-1, respectively during the major flow event. Total phosphorus mobilisation peaked at approximately 0.4 t d-1. Stable isotope analysis showed that allochthonously-derived carbon was rapidly incorporated into biofilm and grazing macroinvertebrates, persisting in riverine food webs for up to four months following the flood. During a subsequent smaller flow event, the floodplain either generated no further carbon or nutrients, or was a sink for carbon and nutrients. Our results provide empirical support for the River Wave Concept and show that allowing floodplain water to return to the river downstream of forests is important for maintaining ecological function within the river channel.

Dissolved organic matter and metabolic dynamics in dryland lowland rivers.

Dissolved organic matter (DOM) within freshwaters is essential for broad ecosystem function. The concentration and type of DOM within rivers depends on the relative contributions of allochthonous sources and the production and consumption of DOM by microbes. In this work we have examined the temporal patterns in DOM quality and productivity in three lowland rivers in dryland Australia using fluorescence excitation emission scans. We assessed the production and consumption of DOM within light and dark bottle assays to quantify the relative contribution of bacteria and algae to the DOM pool and simultaneously assessed whether the systems were autotrophic or heterotrophic. DOM varied temporally within the three river systems over the course of the study period. Characterisation of DOM within light and dark bottles following a 6-hour incubation revealed microbial consumption of a humic-like component and production of protein-like components similar in nature to the amino acids tryptophan and tyrosine. The lack of a significant difference in DOM quality between the light and dark bottles indicated that the protein-like DOM is likely derived from bacterial activity. Respiration was shown to be higher than gross primary production in both whole river and bottle assays, yielding negative net production values and demonstrating that these rivers were predominately heterotrophic. Our work suggests that bacterial metabolism of DOM may be a significant contributor to the production of protein-like components within heterotrophic freshwater systems.

Macroinvertebrate Responses to Conductivity in Different Bioregions of Victoria, Australia.

The use of field data to derive guideline water quality trigger values is likely to be more environmentally relevant than laboratory estimates. In the present study, macroinvertebrate responses to conductivity (specific conductance at 25 °C) within 5 bioregions in Victoria, Australia, were derived from 19 yr of macroinvertebrate field data. Varying response to electrical conductivity (EC) occurred among taxa. Ninety-five percent extirpation concentrations (XC95) for EC were calculated for each genus and species and ranged from 25 to 23 600 µS/cm. Hazardous concentration 5th percentiles (HC05) were calculated for each bioregion from species sensitivity distributions developed using genus and species XC95 values. Genus HC05 values varied substantially between bioregions: bioregion 1 (29 µS/cm), 2 (78 µS/cm), 3 (143 µS/cm), 4 (1068 µS/cm), and 5 (2226 µS/cm). No substantial differences in HC05 values were shown between genus- and species-level calculations in bioregions 1 to 3 and 5; however, a decrease of approximately 300 µS/cm was shown for bioregion 4. The substantial differences in HC05 values between bioregions supports the need for region-specific determination of effects of EC. We explore the use of HC05 values as water quality guidelines across a bioregion gradient and provide a comprehensive analysis of macroinvertebrate responses to changes in EC, with important implications for waterway management. Environ Toxicol Chem 2019;38:1334-1342. © 2019 SETAC.