Richmond River Research Articles

Digital stewardship for river stewardship: creating the Richmond River open access repository

ABSTRACT The catchment of the Richmond River in Lismore, Australia, presents a challenge for record collection and preservation. Firstly, material records belonging to the community are periodically destroyed in flooding. The places where these are physically located as historical archives are often situated in the floodplain. Secondly, relevant records are dispersed across multiple government levels and organizations, posing further threats to their preservation and access. This paper seeks to explore those challenges and describe the development of a river repository at Southern Cross University, funded in part through a grant for flood recovery projects. The repository and our research are motivated by the challenges and considerations surrounding the preservation and management of cultural and scientific materials in the current era, characterized by human impact on the environment and climate change and the integration the Anthropocene heralds between the human and non-human world. Digital stewardship encompasses caring for and managing records and data, goals we extend to the Richmond River and its health.

Pesticide occurrence in a subtropical estuary, Australia: Complementary sampling methods

Monitoring pesticide run-off in the aquatic environment is ecologically important. Effective methods are required to detect the wide range of possible pesticides that enter estuaries from the surrounding catchment. Here, we investigate the occurrence of pesticides in the Richmond River estuary, Australia, and compare the effectiveness of using oysters and Chemcatcher® passive sampling devices against composite water samples. Samples were collected from six sites during two sampling periods: from January to March 2020 (4 weekly composite water samples and oyster collections) and from February to March 2021 (8 twice weekly composite water samples and Chemcatcher® deployment). Samples were analysed for up to 174 pesticides. A total of 21 pesticides were detected across all sites using all methods. The number of pesticides and mixture of pesticides detected in the 2020 sampling was higher in oyster samples than in water samples. In 2021, Chemcatcher® samplers detected more pesticides than in water samples. Herbicides were the most common in all samples. Insecticides and most fungicides were detected only in oysters and Chemcatcher®. Overall, the use of three complementary sampling approaches demonstrated a high level of pesticide input into the Richmond River estuary, highlighting the usefulness of oysters as biomonitors for some pesticides.

Bioaccumulation of estuarine pollutants in leaf oysters (Isognomon ephippium) on the mid-north coast, New South Wales, Australia

Filter feeding bivalves are useful bioindicators for the detection of biologically available pollutants. We investigated trace metals, metalloids, and pesticides in leaf oyster (Isognomon ephippium) soft tissue and shells and compared them to sediment in five estuaries in northern New South Wales, Australia. Concentrations of Pb, Cr, Mn, Ni, Fe and Al were higher in sediments, whereas Zn, Cd, Ag, Hg, Se and As bioaccumulated in the soft tissue. The amount of Cu, Hg and Ni in the sediment from Tweed and Richmond River estuaries exceeded the Australian national sediment quality guideline values. Only one pesticide, atrazine, was detected in leaf oyster soft tissue. Combinations of six elements in the soft tissue were the best predictors of oyster condition index and shell size, whereas sediment contaminants showed weak relationships. Overall, the bioaccumulation of metals and metalloids increases with leaf oyster size and reduces leaf oyster condition, suggesting these large bivalves are useful bioindicators for pollution in estuarine environments.

Speaking with the river: Confluence and interdisciplinarity in rivers and river systems

This article is underpinned by the hypothesis that if Australia is to reassess and improve its relationship to and use of rivers and river systems, then more holistic ways of understanding rivers, and strategies for representing and communicating this understanding, must be developed and brought together. Held over two days in August 2019 at the Lismore campus of Southern Cross University, ‘Speaking With the River’ was an interdisciplinary symposium exploring the capacities of creative research practice to develop new understandings of rivers and river systems as simultaneously environmental, cultural, historical and economic phenomena. In this article, we bring together the voices and disciplinary insights from the symposium and the rivers of Northern New South Wales, and we reflect on the way that riverine language ran throughout our discussions and ideas, providing a connective model of confluences and conjunctions for the interdisciplinary enterprise we were engaged in. This article presents perspectives on rivers and river systems from law, history, art and science, exploring common ground and common purposes. Developing a legal framework for recognising the rights and ‘voices’ of rivers, that is informed by Indigenous knowledges, historical contexts, and scientific understanding, and that employs artistic innovation in representation and translation, is to us the ultimate goal of such an enquiry. While this paper does not undertake the formal steps of developing this framework, it provides the necessary background and instantiates its elements and working methods within the context of the Richmond River in Northern New South Wales.

Exposure to multiple elements reduces the health of Saccostrea glomerata: An assessment of the Richmond River estuary, NSW, Australia.

This study investigated relationships between Sydney Rock Oyster (SRO) health and element concentrations in sediments and oysters from the Richmond River estuary. Six sites were sampled between November 2019 and May 2020. Multivariate permutational analysis of variance was used to compare oyster health parameters and element concentrations between sites, wet and dry conditions, and in oyster and sediment samples. Statistical analysis revealed significant spatial differences in oyster mortality, condition index, and size. Metal concentrations in oyster flesh significantly differed from metals in sediments. Most metals in sediments were below guideline values, except for Ni at some sites. Mortality, condition index, and weight correlated negatively with individual elements in oyster flesh (P, Zn, Mg, Al, Ni). BEST statistical models included various combinations of metals in sediment and flesh. This study highlights that spatial differences in SRO health tend to be related to site-specific metal compositions in sediment and oysters.

Impacts of the 2019 wildfires on large trees and stags in Barking Owl Ninox connivens territories in the lower Richmond River district, north-eastern New South Wales

ABSTRACT In November and December 2019, wildfires in the lower Richmond River district of north-eastern New South Wales burned large tracts of forest including the territories of three pairs of Barking Owls Ninox connivens where breeding activity and two active nests were being monitored. Fortunately, an inventory of large trees and stags (≥60 cm diameter at breast height (dbh)) had been conducted on site prior to the impact of the fires. The two nests were destroyed and many large trees and stags were lost or severely damaged. In the four months following the fires, two 1ha plots were established at the centre of each of the three owl territories. Assessments of these plots demonstrated that 22.6% of the large trees and stags were lost or severely damaged, with a third of this total being ≥100 cm dbh. Despite wide variation in the pre-fire canopy tree structure and floristics, and fire extent and severity among the three territory centres, the percentage large tree loss or severe damage was not substantially different among the territories. Overall, there was a slightly higher percentage of smooth-barked canopy tree species lost or damaged compared to rough-barked species, but this result was biased by the absence of rough-barked species from one of the territory centres. The factor that appeared to be the major influence on large tree and stag loss or severe damage across the owl territories was the pre-fire presence of medium or large-sized basal fire-scars. A total of 72.7% of trees and stags with medium or large basal fire-scars was lost compared with a total of only 12.9% of trees and stags with small basal fire-scars. The loss of, or severe damage to 22.6% of large trees and stags recorded by this study from one wildfire event is considered unsustainable given the increase in frequent severe fires predicted by current climate change modelling. Pro-active protection measures are required to counter such losses of large trees and stags in these forests, and examples are provided of some specific measures recommended for this purpose.

Water quality and the health of remnant leaf oyster (Isognomon ephippium) populations in four Australian estuaries

Leaf oysters (Isognomon ephippium) are large intertidal bivalves that form shellfish reefs. They have a patchy and restricted distribution in estuaries in northern New South Wales, Australia, where the water quality is impacted by a range of anthropogenic stressors from coastal agriculture, urbanisation, industry and recreational activities, along with natural stochastic events such as flooding. Little, however, is currently known about the tolerance of leaf oysters to poor water quality. This study investigated the condition of leaf oyster populations in four estuaries, by assessing the density, size-frequency and condition index. These biological parameters were modelled against habitat water quality parameters including nutrient loads, organic and inorganic carbon, algal biomass, sedimentation and total alkalinity. The water quality assessments were replicated during dry conditions and after rain in two estuaries. Leaf oyster density, size, and body condition significantly differed among the four estuaries. Density ranged from as few as 0.04 oysters per m2 in the heavily impacted Richmond River, up to 267 oysters per m2 in the Tweed River. Overall water quality was also significantly different among the four estuaries, and significant declines in water quality were observed after rain. Distance based linear models revealed significant correlations between biological indicators of leaf oyster reef health and a range of water quality parameters. Leaf oysters with higher condition occur in locations with high dissolved oxygen and salinity levels, whereas low pH and high nutrient run-off were associated with low density and poorer oyster condition. Nevertheless, dense populations were found to persist in areas with pH below 7.9, in high turbidity (over 27 NTU) and areas dominated by fine silt. Their ability to form dense reefs on estuarine soft muddy bottom habitats with low water flow, suggests that leaf oysters could be used to complement rock oysters in future intertidal shellfish reef restoration programs.

Exposure to Multiple Elements Reduces the Health of Saccostrea Glomerata: An Assessment of the Richmond River Estuary, Nsw Australia

Exposure to Multiple Elements Reduces the Health of Saccostrea Glomerata: An Assessment of the Richmond River Estuary, Nsw Australia

‘A very very great part of our life’: Storytelling about the Richmond River

Acts of remembering a river may have a performative function in environmental history and debates around human impact and waterways. The process of remembering and search for meaning are shaped in the present moment when the Richmond is one of the most degraded river systems on the east coast of Australia. Imbued with sentimentality, however, residents speak to the fundamental importance of the river to their lives as they were growing up in and around Lismore. Such histories may provide context for understanding contemporary affective responses to rivers and how emotion shapes our relationships with nature more broadly.

Riverine Complexity: Islandness, socio-spatial perceptions and modification—a case study of the lower Richmond River (Eastern Australia)

In its initial incarnation, island studies regarded islands as highly distinct entities that justified a relatively closed discipline. This orientation was first widened by address to issues such as the linkage of (pre-existent) islands to adjacent areas and, over the last decade, has been further modified by consideration of island-like areas. The latter has led to an increasing acknowledgement that, in some contexts, at least, islands form components of complex aquatic and terrestrial systems in which islandness is a less distinctive attribute than in the case of archetypal (usually marine) islands. While neglected by island studies, river systems that include islands, peninsulas and/or engineered waterfront developments are significant for problematising the distinctiveness of islands and thereby merit attention. This article sets out to map some of the complexities around islands and rivers with specific regard to the Richmond River in northern New South Wales, Australia. We profile this river since its lower reaches feature a range of natural and artificial island and island-like features, including the engineered area known as Ballina Island. We develop our study with regard to both Indigenous perceptions of the riverine space and disruptions, interventions and innovations resulting from European settlement in the region. As such, the article attempts to progress island studies’ research on riverine environments, to problematise the notion of discrete islands/islandness in such contexts and to prompt greater disciplinary reflection on the issues arising from such scrutiny.

The value of estuarine producers to fisheries: A case study of Richmond River Estuary.

Nutrient input from estuarine producers underpins coastal fisheries production and knowing which producers are the most responsible for fish diet helps effectively protect and restore coastal ecosystems. Focussing on the Richmond River in Australia as a case study, we sampled the main estuarine producers and estimated their proportional contributions of nutritional input to seven commercially important fisheries species using Bayesian isotope mixing models. We valued the dietary input of estuarine producers to the commercial fisheries by combining dietary contribution estimates with total annual catch data from commercial fishers. A conservative estimate is that estuarine producers in the Richmond River Estuary contribute at least 82 725kg (78%) of the total annual catch of the seven commercially important fish with an estimated annual value of $AU 450 117. Sea mullet and Mud crab contributed 95% of the total catch, and 93% of the total value assigned to estuarine producers. The two highest valued estuarine producers were tidal marsh (Juncus kraussii) $AU 82 432 and seagrass (Zostera capricorni) $AU 65 423. This study demonstrates the substantial role of estuarine producers to commercial fisheries production and the fisheries economy more broadly. With large areas of estuarine producers under threat globally from land clearing for agriculture, aquaculture and urbanisation, the results presented here provide evidence to support the value of coastal habitats and benefits of their preservation and restoration.

Modelling sediment (dis)connectivity across a river network to understand locational‐transmission‐filter sensitivity for identifying hotspots of potential geomorphic adjustment

AbstractRivers act as ‘jerky conveyor belts’ that transmit fluxes of flow and sediment downstream. This transmission of fluxes can be highly variable within a drainage basin resulting in either abrupt or gradational sediment (dis)connectivity patterns and processes. This study assesses sediment (dis)connectivity across a basin as a means to understand the locational, transmission and filter sensitivity properties of a fluvial system. Drawing upon the case study of Richmond River Catchment, New South Wales, Australia we use the concepts of effective catchment area and buffers, along with graph theory and an empirical sediment transport model CASCADE (Catchment Sediment Connectivity and Delivery), to assess (1) the degree to which modelled sediment cascades along the river network are connected or disconnected (2) how the position, pattern and configuration of (dis)connection facilitates or restricts geomorphic adjustment in different parts of a catchment, and (3) use the findings as a basis to explain the locational‐transmission‐filter sensitivity of the catchment. We use this analysis to segregate supply limited and transport limited reaches and identify various controls on sediment dynamics: in‐stream sediment storage units, junctions between different geomorphic river types, tributary confluences and sediment storage units within partly confined floodplain units. Such analysis lays the foundation for network scale identification of potential hotspots of geomorphic adjustment.

Geomorphic controls on the diversity and patterns of fluvial forms along longitudinal profiles

A mix of catchment-scale controls operate to determine geomorphic river diversity in a catchment. These are contextualised here as imposed and flux controls. Imposed controls do not adjust over geomorphic timeframes and produce the environmental setting in which a river functions. Flux controls are dynamic interactions between flow and sediment that heavily influence geomorphic river diversity. We measure and statistically analyse the network scale mix of imposed and flux controls occurring along longitudinal profiles of various shape. We use this to explain the diversity, pattern and sequence of river types at different positions in a catchment. Using the Richmond River catchment, New South Wales, Australia, as our case study we analyse the imposed controls of slope and valley bottom width and the flux controls of bed material size and gross stream power for five river types, ranging from confined continuous rivers in headwaters to laterally unconfined discontinuous rivers in lowland plains. We find that slope and gross stream power are strong, positively correlated controls on all river types, but act most strongly on rivers with continuous channels. In contrast, bed material size is a dominant control on rivers with discontinuous channels. Slope and gross stream power are also critical for determining the downstream pattern of river types along longitudinal profiles. However, the relationship between these controls is complex as not all rivers are influenced by these controls in the same way. Understanding the mix and patterns of controls operating along longitudinal profiles can be used to explain the variability and pattern of river types we see in the landscape.

An approach for assessing geomorphic river sensitivity across a catchment based on analysis of historical capacity for adjustment

Contemporary river forms and processes can be heavily influenced by the legacies of anthropogenic disturbances to river systems. Knowledge of the historical range of river adjustment can be used to develop an understanding of a river's ‘expected’ character and behaviour. Drawing upon the case study of Richmond River Catchment, New South Wales, Australia, we track the history of geomorphic river adjustment from the time of European colonisation in the mid-late nineteenth century. We use this study to develop an approach, called the ‘Behavioural sensitivity logical tree’ that can be applied to assess and quantify reach scale behavioural sensitivity, defined as the ease with which geomorphic units and associated water, sediment and vegetation interactions adjust within the expected behavioural regime. We use the results to categorise rivers as Fragile, Active sensitive, Passive sensitive, Insensitive and Resistant.Fragile rivers have a behavioural sensitivity >75% and have the propensity to undergo wholesale river change such that a new river type and behavioural regime is created. Active sensitive rivers have a behavioural sensitivity ranging from 50%–75% and have the ability to re-configure within their contemporary behavioural regime. The behavioural sensitivity of Passive sensitive rivers lies between 20%–50%. These rivers have the ability to maintain their behavioural regime and withstand adjustment. Insensitive rivers have a behavioural sensitivity ranging from 5%–20%. They do not readily adjust and may contain significant antecedent elements that limit geomorphic adjustment. Resistant rivers have a behavioural sensitivity <5% and because of the imposed geological setting cannot readily adjust. We further discuss the evolutionary nature of behavioural sensitivity itself and how rivers can dynamically evolve and shift to a different sensitivity category over time in response to different forms of direct and indirect disturbances.

Carbon and nitrogen stable isotope analyses indicate the influence of land use on allochthonous versus autochthonous trophic pathways for a freshwater Atyid shrimp

Aquatic ecosystem community dynamics are affected by anthropogenic pressures and subsequent environmental change. This study investigated the influence of land use in the Richmond River Catchment (New South Wales, Australia) on dietary sources for the freshwater Atyid shrimp Paratya australiensis. Carbon and nitrogen stable isotopes and Bayesian modelling determined the contribution to shrimp diets of two autochthonous sources (microphytobenthos and macrophytes) and two allochthonous sources (C3 and C4 plants) across sites characterised by five different land uses: forest, macadamia, grazing, sugar cane and urban. It was hypothesised that allochthonous sources would contribute more to shrimp diets at sites with more extensive riparian zones, but this was not substantiated. Autochthonous sources dominated shrimp diets across all land uses, although their dietary contribution varied with land use, likely reflecting changes in riparian and in-stream habitats and source availability. Autochthonous contributions were lowest and allochthonous contributions were highest, for shrimp at grazing and sugar cane sites, despite minimal riparian vegetation. A complex array of interactions may influence diets of in-stream consumers. This micro-catchment scale study demonstrated that land use changes play a key role in affecting carbon and nitrogen sources for P. australiensis and have the potential to change community dynamics in freshwater streams.

Towards a systematic revision of the eastern Australian land snail Austrochloritis Pilsbry, 1891 (Eupulmonata, Camaenidae): re-description of its type species, A. porteri (Cox, 1866)

Helix porteri Cox, 1866 is the type species of Austrochloritis Pilsbry, 1891, a speciose genus of camaenid land snail with a known range in eastern Australia stretching from Wilson’s Promontory in Victoria to southeastern Queensland. This species was first described based on material from two locations in New South Wales, “Upper Clarence River at Guy Faux Station” and “Upper Richmond River, at Cowlong”. These two locations are about 230 km apart from each other while all type material is considered to be lost. Comparative morpho-anatomy of specimens collected in the proximity of both type localities shows that the original concept of Helix porteri is based on two distinct species. Here we designate a neotype for this species from the Upper Richmond River area and provide a detailed redescription in order to remove any ambiguity about the identity of Austrochloritis porteri. Material from the vicinity of the second site mentioned in the original description of H. porteri, Guy Fawkes Station, is identified as Austrochloritis speculoris Shea & Griffiths, 2010. We describe key diagnostic features distinguishing both species.

Complementary land use in the Richmond River catchment: Evaluating economic and environmental benefits

Agricultural land uses can contribute to land degradation, water quality decline, and loss of ecosystem function and biodiversity in the surrounding catchment. Trees can assist in catchment management, and re-afforestation strategies have been implemented in an effort to mitigate agricultural impacts and improve degraded land and waterways worldwide. Re-afforestation strategies often target private land, and their success relies on landholder participation. Landholders’ decisions about land-use allocation are driven primarily by the private financial costs and benefits associated with different farming strategies. This research assesses the private on-farm financial impact and the public environmental benefit of land use transition from beef grazing to a mixed beef grazing-forestry system in the Richmond River catchment on the east coast of Australia. GIS analysis identified more than 30% of the catchment as beef grazing land potentially available for re-afforestation, across a variety of soil types and geomorphic characteristics. We used a farm-scale financial model to assess the costs and benefits associated with transition from grazing to a variety of cattle-forestry mixtures that were determined on the basis of their suitability to soil type and slope in different parts of a catchment. We also used a multi-criteria approach to assess the environmental outcomes associated with each transition. The results demonstrate that diversification to a mixed beef grazing-forestry system consistently provides environmental benefit, but the financial impact on landholders varies depending on soil type. Landholders on ferrosol and vertosol soils in this catchment have favourable options that can simultaneously deliver private and public benefits, whereas landholders on kurosol and dermosol soils are more restricted, with environmental improvements possible only as a trade-off with farm financial performance. Based on these results, we suggest that different policy mechanisms are required to encourage graziers in different parts of the catchment to shift towards mixed cattle-forestry systems.

A comparison of macroinvertebrate-based indices for biological assessment of river health: A case example from the sub-tropical Richmond River Catchment in northeast New South Wales, Australia

Abstract Globally, river health is deteriorating due to increased anthropogenic pressures. Accurately assessing river health is crucial for the management of river resources with macroinvertebrates commonly used as biological indicators of ecological integrity. Complex biological data is made more straightforward using indices as they offer the ability to rapidly communicate complex science in a simple form. Management decisions are often based on the results of biological river health assessments, making the identification of the most appropriate, robust and sensitive macroinvertebrate-based index vital when undertaking catchment specific assessments. Selection of a macroinvertebrate-based index should rely on a scientific method rather than arbitrary selection criteria. This study aimed to compare the performance of several macroinvertebrate-based indices to identify the index or indices most appropriate to the Richmond River Catchment (RRC) in northern New South Wales, Australia. River health within the RRC is poor with a clear pollution gradient from upper to lower catchment sites. Six commonly used indices were calculated using family-level identification. The biological assessment supported the physicochemical results with a gradient in river health from upper to lower catchment. Family Richness and Family Richness Percent were assessed as the most usable indices. In studies that have restricted time, budget and expertise they will provide accurate but limited information on river health. SIGNAL2 was identified as the most valid index for assessing river health due to its overall sensitivity to changes in river health, and level of detail on anthropogenic impacts. The poor performance of the AUSRIVAS, EPT and BCI limits or precludes their use for river health assessment in the RRC. While this model for identification and selection of an appropriate macroinvertebrate-based index for catchment scale river health assessments was useful in this context, it needs to be improved with a larger dataset and a greater environmental gradient of river health to make a less subjective evaluation.

Emulator-enabled approximate Bayesian computation (ABC) and uncertainty analysis for computationally expensive groundwater models

Bayesian inference provides a mathematically elegant and robust approach to constrain numerical model predictions with system knowledge and observations. Technical challenges, such as evaluating a large number of models with long runtimes, have restricted the application of Bayesian inference to groundwater modeling. To overcome such technical challenges, we use Gaussian process emulators to replace a transient regional groundwater MODFLOW model for computing objective functions during model constraining. The regional model is designed to assess the potential impact of a proposed coal seam gas (CSG) development on groundwater levels in the Richmond River catchment, Clarence-Moreton Basin, Australia. The emulators were trained using 4000 snapshots derived from the MODFLOW model and subsequently used to replace the MODFLOW model in an Approximate Bayesian Computation (ABC) scheme. ABC was deemed the more appropriate choice as it relaxes the need to derive an explicit likelihood function that the formal Bayesian analysis requires. The study demonstrated the flexibility of the Gaussian process emulators, which can accurately reproduce the original model behavior at a fraction of the computational cost (from hours to seconds). The gain in computational efficiency using the proposed approach allows the global calibration and uncertainty algorithms to become more feasible for computationally demanding groundwater models. Based on the ABC analysis, the probability for the simulated CSG development causing a water table change of more than 0.2 m was less than 5%. In addition to a probabilistic estimate of the prediction, an added value of emulator-assisted ABC inference is providing information on the extent to which observations can constrain parameters and predictions, as well as the flexibility to include various quantitative and qualitative parameter constraining information.

The influence of land use in a highly modified catchment: Investigating the importance of scale in riverine health assessment

Riverine landscapes are studied at varying scales, investigating the complex cause-effect pathways between rivers and their physical, chemical and biological attributes. Policy development, management and planning are often formulated and applied at the regional or catchment scale, however the ecological evidence required to inform at this scale is typically collected from the much smaller scale. This research was aimed at determining if patterns in diatom and macroinvertebrate community composition can be attributed to a specific/single land use in a catchment with multiple land uses. The impacts of forest, macadamia, grazing, sugar cane and urban land uses in the Richmond River Catchment of Northern NSW, Australia were investigated at 20 micro-catchment scale sites. A total of 124 diatom species from 43 genera, along with 92 families and three sub-families of macroinvertebrates, were collected and used to calculate the Richmond River Diatom Index (RRDI), AUSRIVAS and SIGNAL2 scores. Statistical analyses showed distinct groupings of land use categories providing evidence of cause-effect pathways attributed to individual land uses. The RRDI, AUSRIVAS and SIGNAL2 scores all showed distinctions between land use categories, though they were clearer in the RRDI. The RRDI indicated that the grazing sites had the poorest health of the land use categories, followed by sugar cane and urban while the macadamia and forest sites were relatively healthy. Signal 2 scores showed similar trends to the RRDI, while the AURIVAS scores did not present clear trends, particularly in the edge habitat of macadamia land use sites. The results indicated that riparian vegetation and instream habitat play an important role in attenuating inputs and that rehabilitation efforts could potentially improve water quality at a micro-catchment scale and subsequently, result in river health improvement at the catchment scale. The research collected at this micro-catchment scale presents new evidence that further informs and affects decisions made at the catchment scale, where policy and planning is developed and implemented.