Evaluation of faecal glucocorticoid monitoring as a non-invasive assessment of stress in captive white rhinoceros (Ceratotherium simum) after ACTH stimulation

Capturing and holding of white rhinoceros (Ceratotherium simum) for the reintroduction to new reserves or breeding in zoos often involves a risk of mortality. Non-invasive techniques to monitor the stress experienced by these animals may guide the selection of management techniques that reduce risks to animal well-being. The aim of the study was to evaluate the biological relevance of a developed technique to monitor stress hormone metabolites in faecal samples of wild-caught and captive-bred white rhinoceros. Faecal corticosterone concentrations were measured via radioimmunoassay (125I RIA), in seven white rhinoceros (3 males and 4 females), at three sites, before and after an adrenocorticotropic hormone (ACTH) challenge test and control saline injection. Administration of ACTH resulted in a significant increase in faecal corticosterone concentrations (up to 350% above pre-ACTH baseline) within 1-2 days of injection, returning to baseline 4 days post-injection. It was found that individual baseline corticosterone concentrations fluctuate naturally and vary between individual animals, suggesting that an adequate baseline period of faecal sampling is needed in order to accurately assess responses to ACTH stimulation. Furthermore, the technique proved sensitive enough to detect elevations in faecal corticosterone concentrations due to environmental stressors. Data of faecal corticoid concentrations were correlated with gastrointestinal transit (GIT) times before and after ACTH and saline treatment by using art glitter as a digestive marker. This showed that gut passage times correlated to the ACTH-induced time to peak. Overall the results confirm that measurements of faecal corticosterone metabolites with the validated 125I RIA is a useful diagnostic tool to monitor adrenocortical activity in white rhinoceros. This study can therefore provide a methodology for examining chronically heightened adrenal activity in these animals and consequently be used to inform management strategies that aim to improve the welfare of white rhinoceros in captivity.Dissertation (MSc)--University of Pretoria, 2011.Anatomy and Physiologyunrestricte

Heterogeneity of epiphytic diatoms in shallow lakes : implications for lake monitoring

Current diatom assessments of shallow lakes typically use littoral epiphytic diatoms as bioindicators for eutrophication pressure. However, challenges in establishing robust ecological assessments still exist because of the natural pressures that shallow lakes are subjected to which are difficult to quantify (e.g., water-level fluctuations or wave action). Information on the spatial and temporal variability of epiphytic communities within a shallow lake is limited although important for the development of robust bioassessment protocols. We compared epiphytic diatom taxa and functional group compositions between the littoral and pelagic zone of three least-disturbed shallow lakes in the northeastern part of South Africa along a temporal gradient. In comparison to the pelagic zone, the littoral zone was characterized by almost double in species richness. Temporal variability was significantly higher for littoral diatom communities and littoral water physico-chemistry than those of the pelagic. Overall, water depth was a good predictor of the epiphytic diatom taxa and functional group composition. We also found that pelagic diatom taxa and functional groups correlated better with pelagic physico-chemistry than littoral diatoms to littoral physico-chemistry. This could be attributed to un-modeled factors related to natural physical pressures that will have more of an impact on littoral habitats than less exposed pelagic habitats. Given these findings, using pelagic epiphytic diatoms as a bioindicator in shallow lake monitoring programs could be more efficient than littoral diatoms at providing robust ecological assessments due to their relatively low variability.Waterlab (Pty) Ltd. and J.C. Taylor, a recipient of South African National Research Foundation (NRF) incentive funding.http://www.elsevier.com/locate/ecolind2021-04-01hj2020Paraclinical Science

Zooplankton and diatoms of temporary and permanent freshwater pans in the Mpumalanga Highveld region, South Africa

This paper provides a description of the zooplankton and epiphytic diatom communities of permanent and temporary freshwater pans in the Mpumalanga Highveld region of South Africa. Few studies have investigated the biota of pans in this area, which is seriously threatened by mining and agricultural development. Nineteen pan sites within a 20 km radius covering a wide range of water chemistries were sampled once for zooplankton, epiphytic diatoms and water physico-chemical data in 2009. Collected zooplankton and diatom samples were identified to species or genus level. Many of the zooplankton taxa reported in this study were not recorded in similar pan studies in South Africa and southern Africa. The study revealed a difference among the compositions of zooplankton and diatom communities between temporary pans and permanent pans. Zooplankton found exclusively in freshwater temporary pans included cladocerans (Megafenestra aurita and Scapholeberis kingi), calanoids (Mesocyclops major and Thermodiaptomus mixtus), a cyclopoid (Acanthocyclops vernalis) and a rotifer (Platyias quadricornis). Permanent pans were characterized by taxa such as cladocerans (Ceriodaphnia rigaudi and Dunhevedia crassa), a calanoid (Metadiaptomus transvaalensis), cyclopoids (Paracyclops fimbriatus and Eucyclops gibsoni) and rotifers (Brachionus dimidiatus and Brachionus plicatilis). The most commonly occurring diatom taxa in temporary pans included taxa indicative of slightly acidic to circumneutral, dystrophic and nutrient-poor waters such as Nitzschia acidoclinata, Gomphonema gracile and Eunotia bilunaris. Permanent pan assemblages were characterized by taxa typical of saline waters, including Nitzschia frustulum, Amphora veneta and Planothidium engelbrechtii. Species of the genera Pinnularia and Eunotia were almost totally absent from permanent pans.http://africanzoology.journals.ac.za/am2014mn201

Diatom-based models for inferring water chemistry and hydrology in temporary depressional wetlands

Information on the response of temporary depressional wetland diatoms to human-induced disturbances is a limited and important component for the development of temporary wetland biological assessments in human-modified landscapes. Establishing a reference condition of variation due to natural disturbances in depressional wetlands using diatoms is necessary for further investigations of anthropogenic impacts. We examined the temporal and spatial responses of epiphytic diatom communities to natural environmental disturbances within three least disturbed wetlands in the Mpumalanga Province, South Africa. Alkalinity, Na+ and Cl−, water depth and total relative evapotranspiration (ETo) accounted for the highest proportion of temporal variation in composition of epiphytic diatoms, as revealed by canonical correspondence analysis (CCA). Alkalinity, Na+, and Cl− explained a much higher proportion of species variation, using partial CCA. A simple WA with inverse deshrinking produced reasonably robust models for Na+ (rboot2 = 0.71), depth (rboot2 = 0.64) and alkalinity (rboot2 = 0.46), not for Cl− and ETo. We determined species optima and tolerances for Na+, depth and alkalinity which can facilitate identification of anthropogenic impacts based on changes of indicator taxa assemblages. Our study provides a basis for newly developed quantitative tools to be used in biomonitoring studies and evaluations of reference conditions for temporary wetland management.Luisa Riato was supported by a Coaltech Research Association Research Fellowship.http://link.springer.com/journal/107502018-08-30hj2017Paraclinical Science

Development of a diatom-based multimetric index for acid mine drainage impacted depressional wetlands

Acid mine drainage (AMD) from coal mining in the Mpumalanga Highveld region of South Africa has caused severe chemical and biological degradation of aquatic habitats, specifically depressional wetlands, as mines use these wetlands for storage of AMD. Diatom-based multimetric indices (MMIs) to assess wetland condition have mostly been developed to assess agricultural and urban land use impacts. No diatom MMI of wetland condition has been developed to assess AMD impacts related to mining activities. Previous approaches to diatom-based MMI development in wetlands have not accounted for natural variability. Natural variability among depressional wetlands may influence the accuracy of MMIs. Epiphytic diatom MMIs sensitive to AMD were developed for a range of depressional wetland types to account for natural variation in biological metrics. For this, we classified wetland types based on diatom typologies. A range of 4–15 final metrics were selected from a pool of ~ 140 candidate metrics to develop the MMIs based on their: (1) broad range, (2) high separation power and (3) low correlation among metrics. Final metrics were selected from three categories: similarity to reference sites, functional groups, and taxonomic composition, which represent different aspects of diatom assemblage structure and function. MMI performances were evaluated according to their precision in distinguishing reference sites, responsiveness to discriminate reference and disturbed sites, sensitivity to human disturbances and relevancy to AMD-related stressors. Each MMI showed excellent discriminatory power, whether or not it accounted for natural variation. However, accounting for variation by grouping sites based on diatom typologies improved overall performance of MMIs. Our study highlights the usefulness of diatom-based metrics and provides a model for the biological assessment of depressional wetland condition in South Africa and elsewhere.Luisa Riato was supported by a Coaltech Research Association Fellowship. We thank the CSIR for assistance with research expenses and technical support.http://www.elsevier.com/locate/scitotenv2019-01-15hj2017Paraclinical Science

A diatom functional-based approach to assess changing environmental conditions in temporary depressional wetlands

Functional-based assessments to identify the effects of human-induced disturbances on diatom communities are increasingly used. However, information on the response of functional groups to natural disturbances in temporary depressional wetlands is limited although important for the development of temporary wetland biological assessments. We assessed how diatom life-form and ecological guilds responded to a seasonal hydrological and hydrochemical gradient in three least human-disturbed, temporary depressional wetlands. We assigned species to their respective life-form and ecological guild groups and compared metric composition along the gradient. Overall, temporal variability in alkalinity and ionic composition, essentially Na+, as well as hydrological factors, wetland depth and total relative evapotranspiration (ETo), were good predictors of diatom species and functional group composition. Low profile guilds dominated by pioneer life-forms showed the strongest relationship with higher disturbance levels (i.e. increasing Na+, alkalinity with a decrease in depth). Similarly, the planktonic guild and tube-living, rosette and adnate life-forms dominated at higher disturbance levels whereas the high profile diatoms displayed the reverse trend. Our study shows the effectiveness of functional-based assessments beyond traditional species-based approaches for understanding and predicting community responses to temporal changes in environmental conditions. We also highlight the benefit of using both life-forms and ecological guilds where a broad set of metrics can enhance our understanding of the mechanisms relating diatom composition to environmental stressors and provide signs of underlying ecological processes.Luisa Riato was supported by a Coaltech Research Association Research Fellowship. J.C. Taylor is the recipient of South African National Research Foundation (NRF) incentive funding.http://www.elsevier.com/locate/ecolind2018-07-30hj2017Paraclinical Science

Development of diatom-based monitoring tools for assessing depressional wetland condition in the Mpumalanga Highveld region South Africa

Diatoms have a successful history of use in assessments of wetland biological condition. In North America and across Europe, diatom assemblages are used for routine wetland condition assessments to meet the statutory requirements of the European Water Framework Directive and the National Aquatic Resource Survey by the US Environmental Protection Agency. In South Africa, the use of diatom assemblages as indicators of wetland condition may be a promising alternative to the traditional biotic assemblages employed, such as macroinvertebrates or macrophytes, which have proven to be ineffective. We present a preliminary investigation on the feasibility of diatoms in wetland biological assessments in South Africa by evaluating the use of diatoms as indicators of biological condition for depressional wetlands in the Mpumalanga Highveld region of South Africa. Depressional wetlands typically found in this region are either temporary (seasonally inundated) or permanent depressions. Temporary depressional wetlands are expected to be affected by natural environmental disturbances (e.g., seasonal fluctuations in water-level which may cause changes in water chemistry) as compared to relatively stable permanent ones. Establishing whether diatoms are suitable indicators of natural environmental disturbances in temporary depressional wetlands in this region is necessary for further investigations of anthropogenic disturbances. We sampled epiphytic diatoms from three least human-disturbed temporary depressional wetlands during various stages of inundation and showed that the species composition of epiphytic diatom communities were strong indicators of temporally changing environmental conditions. Using the same diatom and physical and chemical data, we also demonstrated that simplifying the taxonomy by using the functional composition (ecological guilds, life-forms) of the epiphytic diatom communities, can assess temporally changing environmental conditions as effectively as the species composition. Moreover, these functional groups provide valuable ecological information that is not available from the species data. Acid mine drainage (AMD) is the predominant stressor in permanent depressional wetlands of the Mpumalanga Highveld region, where coal mines utilise these wetlands for storage of AMD, which has severe impacts on the structure and function of the ecosystem. In order to develop an approach for impact assessment and management of depressional wetlands in the region, we developed an epiphytic diatom multimetric index (MMI) for AMD impacted permanent depressional wetlands. This is also the first diatom index to quantify AMD impacts in wetland habitats. Data collected from 34 sites that represented a range of conditions along an AMD gradient within the Mpumalanga Highveld was used to select responsive diatom metrics which we combined into a multimetric index. We developed separate MMIs for classes of depressional wetland types in order to account for natural variation among diatom assemblages, and compared their performance with an MMI that did not account for natural variation. To account for natural variation, we classified reference sites based on diatom typologies and hypothesised that by using this approach, we would improve MMI performance. Overall, all MMIs performed considerably well, although grouping sites by diatom typology to account for natural variation improved MMI performance, especially the precision, responsiveness and sensitivity to disturbance. We conclude that diatoms have strong potential for use in wetland ecological assessments in South Africa. The experimental and statistical approaches used in this study should expand our knowledge of diatom ecology and further advance the research and development of diatom bioassessment.Thesis (PhD)--University of Pretoria, 2017.Paraclinical SciencesPhDUnrestricte

Genus-level, trait-based multimetric diatom indices for assessing the ecological condition of rivers and streams across the conterminous United States

Taxonomic inconsistency in species-level identifications has constrained use of diatoms as biological indicators in aquatic assessments. We addressed this problem by developing diatom multimetric indices (MMIs) of ecological condition using genus-level taxonomy and trait-based autecological information. The MMIs were designed to assess river and stream chemical, physical and biological condition across the conterminous United States. Trait-based approaches have the advantage of using both species-level and genus-level data, which require less effort and expense to acquire than traditional species-based approaches and eliminate the persistent taxonomic biases introduced over vast geographic extents. For large-extent assessment programs that require multiple taxonomic laboratories to process samples, such as the United States Environmental Protection Agency’s (U.S. EPA’s) National Rivers and Streams Assessment (NRSA), the trait approach can eliminate discrepancies in species-level identification or nomenclature that hinder diatom data interpretation. We developed trait-based MMIs using NRSA data for each of the three large ecoregions across the U.S. - the East, Plains, and West. All three MMIs performed well in discriminating least-disturbed from most-disturbed sites. The MMI for the East had the greatest discrimination ability, followed by MMIs for the Plains and West, respectively. The performance of the MMIs was comparable to that observed in existing NRSA fish and macroinvertebrate MMIs. Our research shows that trait-based diatom indices constructed on genus-level taxonomy can be effective for large-scale assessments, and may also allow programs such as NRSA to assess trends in freshwater condition retrospectively, by revisiting older diatom datasets. Moreover, our genus-based approach facilitates including of diatoms into other assessment programs that have limited monitoring resources