A comparison of bacterial, ciliate and macroinvertebrate indicators of stream ecological health

Abstract

We evaluate the reliability of communities of bacteria and ciliated protozoa as indicators of freshwater ecological health. Samples of epilithic biofilm were taken from 18 freshwater streams, impacted by varying types and degrees of catchment modification. Communities of bacteria and ciliates were characterised using DNA fingerprinting techniques (automated ribosomal intergenic spacer analysis and terminal restriction fragment length polymorphism, respectively) and macroinvertebrate data also obtained, for comparison. Similar to the macroinvertebrates, the taxa richness of ciliate communities was reduced in more developed stream catchments; significant differences in the evenness of ciliate communities were also detected. We could identify no significant relationship between the richness of bacterial taxa and the percentage catchment development. However, a significant trend was detected between bacterial community structure and the predominant catchment land use (rural vs. urban) using a Bray-Curtis measure of similarity, a relationship not detected for the ciliate and macroinvertebrate communities. These findings indicate that stream bacterial, ciliate and macroinvertebrate communities each respond differently to various catchment conditions and highlight the potential of microbial communities to provide novel, alternative indicators of stream ecosystem health.

In search of microbial indicator taxa: shifts in stream bacterial communities along an urbanization gradient

“…The bacterial community structure shifted with increasing urban land cover but with no impacts on alpha diversity assessed through relative diversity indices (OTU richness, Shannon index, evenness), as previously observed in other studies (Lear et al, ; Zeglin, ; Roberto et al, ). These results are in contrast with widely reported decreases in the diversity of ciliate, macroinvertebrate and fish communities in urban streams (Helms et al, ; Moore and Palmer, ; Lear et al, ).…”

“…The bacterial community structure shifted with increasing urban land cover but with no impacts on alpha diversity assessed through relative diversity indices (OTU richness, Shannon index, evenness), as previously observed in other studies (Lear et al, 2011;Zeglin, 2015;Roberto et al, 2018). These results are in contrast with widely reported decreases in the diversity of ciliate, macroinvertebrate and fish communities in urban streams (Helms et al, 2005;Moore and Palmer, 2005;Lear et al, 2011). This finding is consistent with the hypothesis recently put forward by Hosen et al, (2017), who suggested that similar levels of bacterial diversity are maintained across the urbanization gradient because the introduction of novel bacterial taxa from sewage, water distribution or septic systems, and stormwater may compensate for the loss of taxa sensitive to urban conditions.…”

Environmental effects on biofilm bacterial communities: a comparison of natural and anthropogenic factors in New Zealand streams

“…The average taxon richness of bacterial communities was observed to range from 177 OTUs (rural streams) to 194 OTUs (exotic forest), with native forest and urban streams having 184 and 185 OTUs, respectively. This is a key point of difference when compared with existing biological indicators such as macroinvertebrates, which are often depauperate in impacted streams, with the result that ecosystem assessments are forced to rely on a few 'tolerant' species (Boothroyd & Stark, 2000;Lear et al, 2011). The taxon richness of bacterial communities in these streams can be attributed to the inherent (or adapted) high tolerance of certain biofilm members to a wide range of environmental stressors such as pH, temperature, chemical composition including toxicant and heavy metal concentrations (Ager et al, 2010;Ancion, Lear & Lewis, 2010;Wang et al, 2011).…”

“…In New Zealand, such metrics are generally limited to the analysis of communities of invertebrates (Boothroyd & Stark, ; Collier, ) and fish (Joy & Death, ). However, recent investigations of bacterial biofilm communities using modern molecular biology techniques suggest that these could offer an additional tool for assessing stream ecological health (Lear et al ., ; Vinten et al ., ). Bacterial biofilm communities have benefits as indicators since they provide responses to environmental stresses at the basal trophic levels that are detectable before the effects are relayed to upper layers of the stream ecosystem food web (Lewis & Turner, ; Lewis et al ., ).…”

A novel bacterial community index to assess stream ecological health

“…This creates a paradox, whereby the locations where management interventions are undertaken in an effort to improve ecological health are the locations where detecting any improvement is challenging because of the limitations of existing biological indicators. In contrast, bacterial community diversity in impacted sites has been found to remain relatively high, with anthropogenic impact resulting in changes in bacterial community composition, but not a significant loss of diversity (Lear et al, 2011;Reis et al, 2013;Washington et al, 2013). The high bacterial diversity that is maintained even in highly degraded streams provides the potential for a sensitive biological indicator that can operate across the full range of impacted sites.…”