Investigating toxic metal levels in popular edible fishes from the South Durban basin: implications for public health and food security

Contamination of the ocean by heavy metals may have ecosystem-wide implications because they are toxic even if present in trace levels, and the relative ease of their bioaccumulation by marine organisms may affect human health, primarily through consumption of contaminated fish. We evaluated metal concentrations in six different popular edible fish species and estimated the potential health risks from consumption of contaminated fish. There was no correlation between fish length and average metal accumulation although the fish species tended to accumulate significantly more Al and Zn (P?<?0.05) than any of the other metals. Significantly higher Mn concentrations were found in fish gills compared to other body parts in all fish species. Bronze seabream, Catface rockcod, and Slinger seabream had significantly higher mean Cr concentration in the liver than in either the tissues or gills. The highest concentration of Zn in fleshy tissue was in Horse mackerel (56.71 μg g^?1) followed by Bronze seabream (31.07 μg g^?1). Al levels ranged from 5.6 μg g^?1 in Atlantic mackerel to 35.04 μg g^?1 in Horse mackerel tissue while Cu and Cr concentrations were highest in the tissues of Horse mackerel (6.83 and 1.81 μg g^?1, respectively) followed by Santer seabream (3.15; 1.09 μg g^?1) and Bronze seabream (3.09; 1.30 μg g^?1), respectively. The highest tissue concentration of Mn was detected in Bronze seabream (8.23 μg g^?1) followed by Catface rockcod (6.05 μg g^?1) and Slinger seabream (5.21 μg g^?1) while Pb concentrations ranged from a high of 8.44 μg g^?1 in Horse mackerel to 1.09 μg g^?1 in Catface rockcod. However, the estimated potential health risks from fish consumption as determined by the target hazard quotient (THQ) and hazard index (HI) were significantly lower than 1, implying that metals were not present in sufficiently high quantities to be of any health and/or food and security concern in the studied fishes.     

Guest Editorial of the SEEM-2019 conference EEST special issue

Environmental and Ecological Statistics -     

The importance of tangible and intangible factors in human–carnivore coexistence

Conflict with humans is one of the major threats facing the world's remaining large carnivore populations, and understanding human attitudes is key to improving coexistence. We surveyed people living near Hwange National Park about their attitudes toward coexisting with lions. We used ordinal regression models with the results of the survey to investigate the importance of a range of tangible and intangible factors on attitudes. The variables investigated included the costs and benefits of wildlife presence, emotion, culture, religion, vulnerability, risk perception, notions of responsibility, and personal value orientations. This was for the purpose of effectively tailoring conservation efforts but also for ethical policy making. Intangible factors (e.g., fear and ecocentric values) were as important as, if not more important than, tangible factors (such as livestock losses) for understanding attitudes, based on the effect sizes of these variables. The degree to which participants’ fear of lions interfered with their daily activities was the most influential variable. The degree to which benefits accrue to households from the nearby protected area was also highly influential, as was number of livestock lost, number of dependents, ecocentric value orientation, and participation in conflict mitigation programs. Contrary to what is often assumed, metrics of livestock loss did not dominate attitudes to coexistence with lions. Furthermore, we found that socioeconomic variables may appear important when studied in isolation, but their effect may disappear when controlling for variables related to beliefs, perceptions, and past experiences. This raises questions about the widespread reliance on socioeconomic variables in the field of human–wildlife conflict and coexistence. To facilitate coexistence with large carnivores, we recommend measures that reduce fear (through education and through protective measures that reduce the need to be fearful), reduction of livestock losses, and ensuring local communities benefit from conservation. Ecocentric values also emerged as influential, highlighting the need to develop conservation initiatives tailored to local values.     

Seasonal and spatio-temporal distribution of faecal-indicator bacteria in Tyume River in the Eastern Cape Province, South Africa

We assessed the incidence of faecal-indicator bacteria in Tyume River over a 12-month period between August 2010 and July 2011. Total coliforms, faecal coliforms and enterococci were determined by the membrane filtration method. Total coliforms were detected in counts ranging from 2.1?×?10² to 3.4?×?10⁴?CFU/100 ml. Faecal coliform counts ranged from 1?×?10² to 1.6?×?10⁴?CFU/100 ml while enterococci counts were in the range of 3.3?×?10¹ to 5.1?×?10³?CFU/100 ml. Indicator bacteria counts increased from upstream to downstream sampling sites. Counts of indicator bacteria at all sites were significantly affected by seasonal changes. The bacteriological qualities of the river water were poor, exceeding the guideline of 200 CFU/100 ml and 33 CFU/100 ml for faecal coliforms and enterococci, respectively, for recreational water. Faecal coliform counts also exceeded the 1,000 CFU/100 ml guideline for water used in fresh produce irrigation. Microbial source tracking results showed that faecal pollution was predominantly of human origin during spring at all sampling sites. During other seasons, human faecal pollution was largely confined to midstream and downstream sampling sites. Generally, the presence of faecal-indicator bacteria in the river water samples suggests faecal pollution of this freshwater resource, raising the possibility of the presence of pathogenic microorganisms in the water and a threat to public health.     

Variations in the physicochemical characteristics of the Buffalo River in the Eastern Cape Province of South Africa

The physicochemical characteristics of the Buffalo River in the Eastern Cape Province of South Africa were evaluated using standard methods. The assessment was carried out with total of 72 water samples collected from six sites over a 12-month period, from August 2010 to July 2011. Water temperature ranged from 11 to 28 °C, while pH varied from 6.6 to 10.7 and turbidity from 1.7 to 133 NTU. Electrical conductivity, total dissolved solids (TDS) and salinity showed drastic variations (42.3–46,693 μS/cm, 20.3–23,350 mg/l and 0.02–33.8 PSU, respectively) and the significantly (P?<?0.05) higher mean values of these parameters recorded at Parkside reflect the influence of seawater at the Buffalo River estuary. The concentrations of other parameters ranged as follows: chloride (3.7–168 mg/l), DO (6.9–11.1), BOD (0.6–9.4), COD (3.7–45.9), nitrite–nitrogen (0.02–0.21), nitrate–nitrogen (1–4.47) and orthophosphate (0.01–1.72). There was a significant positive correlation between water temperature and DO (r?=?0.200; P?<?0.01). Significant (P?<?0.01) positive correlations also existed between TDS and salinity (r?=?0.921), COD and each of salinity (r?=?0.398), TDS (r?=?0.375) and chloride (r?=?0.330), nitrate and phosphate (r?=?0.323) and BOD and turbidity (r?=?0.290). Significant (p?<?0.01) inverse relationships existed between DO and each of phosphate (r?=??0.295) and nitrate (r?=??0.168). We conclude that the Buffalo River water quality deteriorated in the plains, compared with the upper reaches. Urgent measures are needed to safeguard the river in view of the potential health concerns as many households rely solely on the untreated river water.     

The utility of earth observation technologies in understanding impacts of land reform in the eastern region of Zimbabwe

Land tenure and land policies influence the spatial variations of land use/cover (LULC) at any given time or place. Thus, it is important to evaluate the role of land tenure policies on land cover changes. In this study, we evaluate the utility of Landsat Thematic Mapper (TM) images in understanding the impacts of the 2000 fast track land reform (FTLR) policy on LULC in the eastern region, Zimbabwe. Landsat images for the year 1995, 2000, 2005 and 2011 were classified using traditional image classification techniques (i.e. the maximum likelihood (ML) classifier) in a geographic information system (GIS) environment. Results indicate that forested areas drastically decreased by approx. 30% between the year 2000 and 2005 (during and after the FTLR), while croplands marginally increased by (approx. 30%) the results further showed that slight increase in bare lands (degraded lands) and disturbed lands. The observed LULC changes after FTLR were mostly induced by human activities resulting from changes in land tenure. Overall, the findings of this study underscores the importance of remotely sensed data in assessing the impact of FTLR on forest resources for purposes of informed and sustainable forest management.     

Assessment of the Risks for Human Health of Adenoviruses,Hepatitis A Virus,Rotaviruses and Enteroviruses in the Buffalo River and Three Source Water Dams in the Eastern Cape

Buffalo River is an important water resource in the Eastern Cape Province of South Africa. The potential risks of infection constituted by exposure to human enteric viruses in the Buffalo River and three source water dams along its course were assessed using mean values and static quantitative microbial risk assessment (QMRA). The daily risks of infection determined by the exponential model [for human adenovirus (HAdV) and enterovirus (EnV)] and the beta-Poisson model (for hepatitis A virus (HAV) and rotavirus (RoV)) varied with sites and exposure scenario. The estimated daily risks of infection values at the sites where the respective viruses were detected, ranged from 7.31 × 10^?3 to 1 (for HAdV), 4.23 × 10^?2 to 6.54 × 10^?1 (RoV), 2.32 × 10^?4 to 1.73 × 10^?1 (HAV) and 1.32 × 10^?4 to 5.70 × 10^?2 (EnV). The yearly risks of infection in individuals exposed to the river/dam water via drinking, recreational, domestic or irrigational activities were unacceptably high, exceeding the acceptable risk of 0.01 % (10^?4 infection/person/year), and the guideline value used as by several nations for drinking water. The risks of illness and death from infection ranged from 6.58 × 10^?5 to 5.0 × 10^?1 and 6.58 × 10^?9 to 5.0 × 10^?5, respectively. The threats here are heightened by the high mortality rates for HAV, and its endemicity in South Africa. Therefore, we conclude that the Buffalo River and its source water dams are a public health hazard. The QMRA presented here is the first of its kinds in the Eastern Cape Province and provides the building block for a quantitatively oriented local guideline for water quality management in the Province.     

Studies on the bacteriological qualities of the Buffalo River and three source water dams along its course in the Eastern Cape Province of South Africa

The Buffalo River and its dams are major surface water sources used for fresh produce irrigation, raw water abstraction and recreation in parts of the Eastern Cape Province in South Africa. Over a 12-month period (August 2010 to July 2011), we assessed the bacteriological qualities of water from the river and 3 source water dams along its course. Faecal indicator bacteria (FIB), including total coliform (TC), faecal coliform (FC) and enterococci (ENT) counts, were high and ranged as follows: 1.9?×?10²–3.8?×?10⁷, 0–3.0?×?10⁵ and 0–5.3?×?10⁵?cfu/100 ml for TC, FC and ENT, respectively. Significantly (P?<?0.05) higher concentrations of FC and ENT were observed at the sampling sites located at the lower reaches of the river compared to the upper reaches, and at Bridle Drift Dam compared to the other two dams. FIB counts mostly exceeded the recommended maximum values suggested by national and international guidelines for safe fresh produce irrigation, domestic applications, full-contact recreation and livestock watering. These results show that the bacteriological qualities of the Buffalo River and dams were poor, and suggest that sewage was dumped into the Buffalo River during the study period. Urban runoffs and effluents of wastewater treatment plants appear to be important sources of faecal contamination in the river. We conclude that these water bodies represent significant public health hazards. Provision of adequate sanitary infrastructure will help prevent source water contamination, and public health education aimed at improving personal, household and community hygiene is imperative.     

Pivotal discrepancy measures for Bayesian modelling of spatio-temporal data

Environmental and Ecological Statistics - Within the field of geostatistics, Gaussian processes are a staple for modelling spatial and spatio-temporal data. Statistical literature is rich with...