Richard Marchant

A trait database of stream invertebrates for the ecological risk assessment of single and combined effects of salinity and pesticides in South-East Australia

We compiled a database on a priori selected traits for South-East Australian freshwater macroinvertebrate families and used this data for the development of a biotic indicator for the detection of the effects of salinisation on freshwater communities (SPEAR(salinity)) and for the adaptation of the existing SPEAR(pesticides) index for South-East Australian taxa. The SPEAR(salinity) indicator showed a reasonably high relationship (0.38≤r(2)≤0.5) with salinity in terms of logarithmic electrical conductivity (log EC) using field biomonitoring data from 835 pools and riffle sites in Victoria and South Australia. Several other biotic indexes that were calculated for comparison purpose exhibited a lower relationship with log EC. In addition, SPEAR(salinity) was the only indicator that did not respond to other water quality variables and was therefore most selective. We used log EC data and modelled pesticide exposure for sites in Victoria in concert with SPEAR(salinity) and the existing SPEAR(pesticides) index to assess whether pesticides interacts with effects of salinity on invertebrate communities and vice versa. No interaction with pesticides was found for the effect of log EC on SPEAR(salinity), whereas EC interacted with the estimated pesticide exposure on the invertebrate communities. To foster the development of further trait-based ecological indicators, we suggest a conceptual model that predicts response traits based on the disturbance regime and disturbance mode of action of the stressor. Biotic indicators based on a priori selected traits represent a promising biomonitoring tool even for regions where ecological information is scarce.

The definition of species richness used by species sensitivity distributions approximates observed effects of salinity on stream macroinvertebrates

The risk of chemicals for ecological communities is often forecast with species sensitivity distributions (SSDs) which are used to predict the concentration which will protect p% of species (PCp value). However, at the PCp value, species richness in nature would not necessary be p% less than at uncontaminated sites. The definition of species richness inherent to SSDs (contaminant category richness) contrasts with species richness typically measured in most field studies (point richness). We determine, for salinity in eastern Australia, whether these definitions of stream macroinvertebrate species richness are commensurable. There were strong relationships (r2≥0.87) between mean point species, family and Ephemeroptera, Trichoptera and Plecoptera species richness and their respective contamination category richness. Despite differences in the definition of richness used by SSDs and field biomonitoring, their results in terms of relative species loss from salinity in south-east Australia are similar. We conclude that in our system both definitions are commensurable.

Temporal persistence of benthic invertebrate communities in south-eastern Australian streams: taxonomic resolution and implications for the use of predictive models

Benthic macroinvertebrates are commonly used to monitor the condition of rivers and streams. Predictive models and biological objectives used in environmental policies, two tools for assessing stream condition, rely on the assumption that the communities from which the invertebrates are derived are sufficiently stable or persistent over time for valid comparisons to be made with test sites sampled years afterwards. There has only been limited testing of this in Australia and there has been no formal programme established to assess long-term changes in aquatic ecosystems. In this paper, data sets collected from the Latrobe and Yarra river systems in south-eastern Australia, sampled over periods of up to 20 years between initial and final samplings, were examined. Using multivariate analyses, it was found that stream communities were persistent at the taxonomic level of family, but significant temporal changes were apparent using species-level data. Tests of rank abundance (Friedmans and Spearman rank correlation) gave mixed results but generally lead to the same conclusions. The implications of these results are discussed with regard to changes in faunal composition, stability of rank abundances, impacts on the use of predictive models and biological objectives, and possible links to major environmental features.

Effects of sediment pollution on food webs in a tropical river (Borneo, Indonesia)

The impact of pollution on the trophic ecology of the Kelian River (Borneo, Indonesia) was studied by comparing food webs (on the basis of gut analysis and field and laboratory observations) at six sites. The upper sites were in pristine rainforest but the river became increasingly polluted downstream, largely owing to sedimentation from alluvial gold mining activities. Four previous studies all showed a downstream decrease in macroinvertebrates (mean abundance: 272 per 400 cm2 at Site 1 dropped to 2.6 at Site 6; mean number of taxa: 37.6 at Site 1 down to 1.6 at Site 6), and this was highly correlated with suspended solids. Food webs also reflected the effect of pollution. Cleaner sites had more complex food webs, with more elements, links, higher linkage density and higher complexity than did downstream polluted sites, which lacked grazers, shredders and filterers. Several taxa that were grazers at clean sites became collector-gatherers at polluted sites. Despite the enormous impact of pollution, cessation of alluvial mining activities resulted in some recovery. The resilience of the fauna is likely to be enhanced by the tropical conditions with high rainfall, rapid flow rates and high temperatures, coupled with rapid life cycles. Fish distribution and diets did not appear to be affected by pollution.

River conservation in a changing world: invertebrate diversity and spatial prioritisation in south-eastern coastal Australia

Concentration of human populations with likely impacts of climate change present major challenges for river conservation in the south-eastern coastal region of Australia. Quantitative methods for spatial prioritisation of conservation actions can play a major role in meeting these challenges. We examined how these methods may be applied to help plan for potential impacts of climate change in the region, using macroinvertebrate assemblages as surrogates of river biodiversity. Environmental gradients explaining broad-scale patterns in the composition of macroinvertebrate assemblages are well represented in protected areas; however, their effectiveness for conserving river biodiversity with climate change depends on linking management inside and outside protected areas. Projected increases in temperature and sea level may be used to prioritise conservation to counter likely major impacts in high-altitude zones and the coastal fringes, whereas elsewhere, considerable uncertainty remains in the absence of better downscaled projections of rainfall. Applying such spatial prioritisations using biodiversity surrogates could help river-focussed conservation around the world.

Regional and local species diversity patterns for lotic invertebrates across multiple drainage basins in Victoria

Regional (RSR) and local species richness (LSR) was recorded for stream invertebrate communities at reference sites in 25 drainage basins in Victoria. Regional species richness was defined as the total number of species recorded at all reference sites within a basin, and LSR as the total numbers of species recorded at a single reference site. Records were obtained from bank and channel habitats and analysed separately. Regressions between LSR and RSR indicated a proportional or linear relationship in both habitats. This applied to the whole data set and to subgroups representing Ephemeroptera, Plecoptera and Trichoptera (EPT as a group), Hemiptera, Diptera, and Coleoptera. All data sets thus represented communities in which no upper limit to LSR was observed. Multiple regressions between LSR and RSR, number of samples per site (N) and seven physical variables showed that RSR and N were nearly always significantly related to LSR. Few of the physical variables were significant except conductivity (for EPT and Coleoptera). Multidimensional scaling ordinations revealed an east-west gradient in compositional similarity of invertebrates, upon which variations in RSR had a major influence. Investigation of factors that regulate RSR will thus be necessary for a broad scale view of what regulates LSR.

Evaluation and application of methods for biological assessment of streams: summary of papers

During the past decade, new biological assessment methods have been developed for use in inland waters. Less work has gone into objective testing of the individual methods and their diagnostic or other capabilities, and very little effort has been devoted to comparing methods. This special issue of Hydrobiologia brings together a number of the most recently developed bioassessment methods, or aspects of them, so readers can begin to compare their potential value and practical usefulness.

The productivity of the macroinvertebrate prey of the platypus in the upper Shoalhaven River, New South Wales

The platypus (Ornithorhynchus anatinus) feeds almost exclusively on benthic macroinvertebrates, yet no attempt has been made to link its energy demands with the productivity of its benthic macroinvertebrate prey. In the upper Shoalhaven River, New South Wales, we estimated macroinvertebrate production (in 2009 and 2011) from benthic samples and recorded platypus diet (2009 only) from cheek pouch samples. Ephemeroptera, Trichoptera and Chironomidae were the most numerous of six major groups in both the cheek pouches and the benthic samples. Three other groups (Odonata, Coleoptera, Sphaeriidae) were much less abundant in the benthos, but Odonata were common in the cheek pouches. In both years the Ephemeroptera, Trichoptera and Chironomidae had levels of production that were an order of magnitude higher than those of the three other groups. Rank correlation indicated that the most productive taxa were those most likely to occur in the cheek pouches. Total macroinvertebrate production for the six groups varied from 7.8gDWm–2year–1 in 2009 to 13.1gDWm–2year–1 in 2011. Previous estimates of field metabolic demand of the platypus enabled calculation of the number that could be supported by a given level of production. The observed levels of production were sufficient to support 13–27 platypuses in 2009 and 22–45 in 2011 along a 1.5-km reach of the river. Despite considerable landscape change, productive foraging habitat persists in the upper Shoalhaven River.

Trophic relationships of the platypus: insights from stable isotope and cheek pouch dietary analyses

The unique Australian monotreme, the platypus (Ornithorhynchus anatinus) potentially exerts a strong top-down influence on riverine food webs in eastern Australia. However, despite considerable interest in the evolutionary history and physiology of the platypus, little is known of its trophic relationships. To address this lack of knowledge we used stable isotope analysis, in combination with the analysis of food items stored in cheek pouches, to determine its position in a typical riverine food web. This was the essential first step in the process of designing a larger study to investigate the relative importance of top-down and bottom-up effects in rivers where the platypus occurs. We found that platypuses were feeding on a wide range of benthic invertebrates, particularly insect larvae. The similarity of δ13C and δ15N values recorded for the platypus, a native fish (Galaxias sp.) and the exotic mosquitofish (Gambusia holbrooki) indicated dietary overlap and potential competition for the same resources. Although cheek pouch studies identify most of the major groups of prey organisms, the potential for contribution of the soft-bodied organisms such as larval dipterans, is suggested by stable isotope analysis, indicating that the use of both techniques will be important in future ecological investigations.

The imperative need for nationally coordinated bioassessment of rivers and streams

Declining water quality and ecological condition is a typical trend for rivers and streams worldwide as human demands for water resources increase. Managing these natural resources sustainably is a key responsibility of governments. Effective water management policies require information derived from long-term monitoring and evaluation. Biological monitoring and assessment are critical for management because bioassessment integrates the biological, physical and chemical features of a waterbody. Investment in nationally coordinated riverine bioassessment in Australia has almost ceased and the foci of management questions are on more localised assessments. However, rivers often span political and administrative boundaries, and their condition may be best protected and managed under national policies, supported by a coordinated national bioassessment framework. We argue that a nationally coordinated program for the bioassessment of riverine health is an essential element of sustainable management of a nation’s water resources. We outline new techniques and research needed to streamline current arrangements to meet present-day and emerging challenges for coordinating and integrating local, regional and national bioassessment activities. This paper draws on international experience in riverine bioassessment to identify attributes of successful broad-scale bioassessment programs and strategies needed to modernise freshwater bioassessment in Australia and re-establish national broad-scale focus.