Francis O. Arimoro

Guides to the Freshwater Invertebrates of Southern Africa. Volume 7: Insecta I. Ephemeroptera, Odonata and Plecoptera

April 2003, Water Research Commission, Pretoria, South Africa, Soft cover, 288 pages. WRC Report No. TT 207/03; ISBN 978-1-77005-017-4; price R100 (South Africa), US

The impact of water quality deterioration on macroinvertebrate communities in the Swartkops River, South Africa: a multimetric approach

50 (international), Obtainable from the Water Research Commission, Private Bag X03, Gezina, Pretoria 0031, South Africa, or orders@wrc.org.za

Exploring stream communities in a tropical biodiversity hotspot: biodiversity, regional occupancy, niche characteristics and environmental correlates

A multimetric approach, using 21 metrics representing five categories — abundance, composition, richness, diversity and biotic indices — was applied to investigate the impacts of water quality deterioration on macro-invertebrate communities in the Swartkops River. Macroinvertebrates were sampled seasonally between August 2009 and July 2010 using the South African Scoring System version 5 (SASS5) protocol at one reference site upstream of Uitenhage and three downstream sites. Assessment of water quality impacts on macroinvertebrates was based on the discriminatory ability of metrics between the reference and impaired sites, and on their correlation with the physico-chemical variables. The metrics’ discriminatory ability was explored using box plots, and their relationships with water chemistry variables elucidated with Pearsons correlation. Trichoptera abundance, %Chironomidae + Oligochaeta, %Ephemeroptera–Trichoptera–Odonata–Coleoptera (ETOC), %Trichoptera, Ephemeroptera–Plecoptera–Trichoptera (EPT) richness, ETOC richness, Margalefs family richness index, equitability, Shannon and Simpson diversity indices, SASS5 score and average score per taxon (ASPT) discriminated between the reference and impacted sites, and also exhibited significant correlations (p < 0.05) with water chemistry variables. Conversely, Gastropoda abundance, EPT abundance, ETOC abundance, EPT:Chironomidae ratio, %EPT, %Corixidae, %Oligochaeta + Hirudinae, Chironomidae + Oligochaeta abundance and Hemiptera + Diptera richness did not discriminate between the reference and impacted sites.

Patterns of chironomid body-size distribution in an effluent-impacted river in the Eastern Cape, South Africa

Exploring and describing biodiversity and the mechanisms structuring it is fundamental to advancing ecology. This is particularly pertinent in understudied biogeographical regions, such as the Afrotropics, that are characterised by strong seasonal climatic shifts. We investigated the characteristics of stream biodiversity in the Niger Delta region of Nigeria, a tropical biodiversity hotspot, by examining patterns in 20 stream invertebrate communities across both the wet and dry seasons. For this, we took a multi-faceted approach accounting for the three levels of biodiversity (α, β and γ), including partitioning the nestedness and turnover components of β diversity, regional occupancy-abundance patterns, niche characteristics, and the environmental drivers of community structure. α diversity was low in these streams, with strong turnover between sites leading to high β diversity contributing to regional biodiversity, but there was little variation in communities between seasons. The proportion of sites occupied by taxa declined with increasing niche position, and decreasing niche breadth. Occupancy was predicted well by a combination of these two factors (niche position and breadth), but not mean local abundance, as the abundance-occupancy link was an upper-limit unimodal relationship. On average, community structure was linked more strongly to environmental variables in the wet season. Our findings demonstrate the clear role of spatial, but not temporal, turnover in assemblages, which likely reflects the environmental heterogeneity of this region. This is further supported by the fact that regional occupancy was mostly related to niche characteristics, particularly niche position. We emphasise the importance of continued basic and applied ecological work in this important biogeographic region to enable better protection of its biodiversity.

Mouthpart deformities in Chironomidae (Diptera) as bioindicators of heavy metals pollution in Shiroro Lake, Niger State, Nigeria

Body size is an important determinant of assemblage structure in rivers and streams impacted by elevated concentrations of pollutants such as salts and metals. In the present study, because of the larger surface-area-tovolume ratio of small-bodied chironomid species compared with large-bodied species, it was hypothesised that the relative abundance of the small-bodied species would decrease at the impacted sites by elevated concentrations of total dissolved solids compared with that at the less-impacted control site. The aim of this study was to analyse and compare patterns of chironomid final instar body-size classes at impacted sites with those at the control site. Chironomid larvae were sampled seasonally from August 2009 to September 2012 from one control site and three impacted sites (Sites 2, 3 and 4) in the Swartkops River, Eastern Cape. Site 2 was impacted by diffuse pollution sources, whereas Sites 3 and 4 were impacted by wastewater effluent discharges in addition to diffuse pollution sources. Small-bodied species dominated the assemblage at the control site and declined significantly at the impacted sites, suggesting that chironomid body size responds predictably to deteriorating water quality in the Swartkops River.

Ecology and abundance of oligochaetes as indicators of organic pollution in an urban stream in southern Nigeria.

In this study, mouthpart deformities in Chironomid larvae (Diptera) were investigated in relation to sediment contamination in the Shiroro Lake in Nigeria. Metals and chironomids were sampled monthly at three stations (A-C) between August 2013 and January 2014. Across the stations, zinc ranged (3.9-75mg/g), manganese (1.29-1.65mg/g), lead (0.00-0.10mg/g), iron (101-168mg/g) and copper (0.13-0.17mg/g). The metal ions did not differ significantly (P > 0.05) between the sampling stations. However, zinc and iron ions were significantly different between the sampling seasons (P < 0.05). Thirteen chironomid species were recorded, with Chironomus sp., Polypedilum sp. and Ablabesmyia sp. dominating the assemblage structure. Mouthpart deformities were significantly higher at Station A compared with Station C, and seasonally significantly higher during dry season compared with wet season. Elevated incidences of deformity were recorded in Chironomus spp larvae as compared to other genera therefore for further studies in this region assessments should be based solely on Chironomus species and ignoring the rest. Strategies need to be developed to reduce the contaminations and the biological effects.