The Application of a Macroinvertebrate Indicator in Afrotropical Regions for Pesticide Pollution

Abstract

Many biotic integrity indices are not able to isolate community effects due to pesticide exposure as the communities also respond to other anthropogenic and natural stressors. A macroinvertebrate trait bioindicator system that is pesticide specific was therefore developed to overcome these challenges. This system, called SPEAR (SPEcies At Risk), was applied in South Africa as an indicator to link known pesticide catchment usage to changes in the macroinvertebrate community, especially when analytical methods are inconclusive. In addition, the SPEARsalinity index within the SPEAR suite of tools was also evaluated for its effectiveness in South Africa. The results indicated that all of the sites have either been exposed to the same pesticide pressure or not been exposed to pesticides as the SPEAR results were similar when compared to the pesticide intensity. The interaction with other factors like nutrients or salinity was likely a factor that confounded the SPEARpesticides indicator.

Calibration of the SPEARpesticides Bioindicator for Cost-effective Pesticide Monitoring in East African Streams

“…Thus, the studied species composition, pesticide exposure patterns and ecological conditions may differ from those in other continents such as in sub-Saharan Africa. Malherbe et al (2018) found only a non-significant response of SPEARpesticides values to pesticide pollution in South African streams. In contrast, SPEARpesticides has been successfully applied and validated to assess pesticide pollution in various streams ranging from Southern to Northern Europe (Liess et al 2008), and (after minor modification) in Australia (Schaefer et al 2011a) and Argentina (Hunt et al 2017).…”

“…It should be noted that Malherbe et al (2018) used a very coarse toxicity estimation based on the sampling site location, assuming that pesticide pollution increases from upstream to downstream of the irrigation system. Toxicity estimation thus did not consider pesticide input from outside the irrigation scheme, whereas our data show that subsistence farming may considerably contribute to pesticide pollution.…”

“…These case studies illustrate the growing interest in the use of bioindicators for freshwater monitoring but did not explicitly consider effects of a specific stressor such as pesticide pollution. Apart from our study, the only application of SPEARpesticides in sub-Saharan Africa we are aware of has been described in Malherbe et al (2018). The authors applied a previous version of the European SPEARpesticides index and the Australian SPEARpesticides index (Schaefer et al 2011a) to macroinvertebrate samples from the Crocodile River and the Harts River in South Africa.…”

“…Toxicity estimation thus did not consider pesticide input from outside the irrigation scheme, whereas our data show that subsistence farming may considerably contribute to pesticide pollution. Therefore, the poor performance of SPEARpesticides in Malherbe et al (2018) may be partly related to uncertainties in the assessment of pesticide exposure. Additionally, the authors sampled macroinvertebrates from large rivers, whereas SPEARpesticides has been developed for small to medium streams.…”

“…The SPEARpesticides concept is based on ecotoxicological traits rather than taxonomic relations and thus provides a mechanistic linkage of pesticide stress and the community response; in contrast to classical taxonomy-based bioindicators, trait-based approaches can overcome issues with natural taxonomic variability and may thus be applicable even across different climatic regions (Menezes et al 2010). For freshwater macroinvertebrates in the Southern hemisphere, information on ecotoxicological traits is very scarce (Schaefer et al 2011a, Malherbe et al 2018). However, Wang et al (2014) found that related saltwater invertebrates from temperate and tropical regions differ only slightly in their acute sensitivity to toxicants.…”