Effects of locally rare taxa on the precision and sensitivity of RIVPACS bioassessment of freshwaters

1. An overall aim in freshwater bioassessment is to use biological methods, metrics and forms of indices which are precise, in that they give repeatable results between replicate samples, but which are also sensitive to changes in environmental impacts and stresses. Here we studied the effects of excluding taxa with site‐specific River Invertebrate Prediction and Classification System (RIVPACS)‐type model expected probabilities less than (or equal to) a threshold P_t (0.0, 0.1, 0.2,…,0.9) on the value, precision and power to detect biological effects of environmental stress using the observed to expected ratios (O/E) of biotic indices used to assess the ecological status of U.K. river sites. 2. Amongst the 614 high quality GB RIVPACS reference sites, excluding taxa with low expected probabilities of occurrence gave less total variation (i.e. lower SD) in the estimates O/E for number of taxa (O/E_TAXA) and the average score per taxon (O/E_ASPT). 3. A separate analysis of a replicated sampling study of sites from a wide range of physical types and qualities revealed that sampling variances in O/E for reference condition sites decreased as more locally rare taxa were excluded (but only up to P_t = 0.5 for O/E_ASPT). However, for moderately impacted and poor quality sites, estimates of both O/E_TAXA and O/E_ASPT based on all (P_t = 0.0) or most taxa (i.e. P_t ≤ 0.3) had lower sampling variances and were more precise. 4. Within a very large independent set of test sites with a wide range of perceived levels of environmental stress, increasing the threshold P_t led to systematic compression of the realised O/E scale towards unity. Specifically, with increasing threshold, O/E values >1 are on average reduced, while O/E values <1 have a tendency to be higher and closer to unity (with the exception of O/E_ASPT for the most severely stressed sites). 5. Accuracy and statistical power to detect environmental stress (measured by the percentage of stressed sites with O/E below the lower 10‐percentile value for reference sites) was very similar using O/E_TAXA for P_t up to 0.7. Using O/E_ASPT, power to detect overall general stress decreased slowly as P_t was increased; the rate of fall in power was slightly faster when restricted to sites subject to moderate or severe stress from organic inputs. 6. Taxa which are more sensitive to (organic) stresses [i.e. have high Biological Monitoring Working Party (BMWP) scores] tend to be naturally less widespread (i.e. amongst reference sites) and thus were found to have considerably lower average site‐specific expected probabilities; this may explain why the use of higher thresholds P_t can exclude more such sensitive taxa and lead to underestimation of the extent of impacts. 7. The standard U.K. RIVPACS sampling and sample processing procedures aim to identify all taxa within a sample. This may lead to a longer distribution tail of rarer (low probability) taxa than sampling methods based on a fixed count subsample and influence the practical effects of excluding rare taxa with low expected probabilities from bioassessments.     

Turning food waste to energy and resources towards a great environmental and economic sustainability: An innovative integrated biological approach

Food waste (FW) management is a global conundrum because of the rapid population growth and growing economic activity. Currently, incineration and landfill are still the main means for FW management, while their environmental sustainability and economic viability have been in question. Recently, the biological processes including anaerobic digestion, aerobic composting, bioethanol fermentation, feed fermentation etc. have attracted increasing interest with the aims for energy and resource recovery from FW. However, these biological approaches have inherent drawbacks, and cannot provide a comprehensive solution for future FW management. Therefore, this review attempts to offer a critical and holistic analysis of current biotechnologies for FW management with the focus on the challenges and solutions forward. The biological approaches towards future FW management should be able to achieve both environmental sustainability and economic viability. In this instance, the concept of zero solid discharge-driven resource recovery has thus been put forward. According to which, several innovative biological processes for FW management are further elucidated with critical analysis on their engineering feasibility and environmental sustainability. It turns out that is an urgent need for turning current single task-orientated bioprocess to an integrated biological process with multiple tasks of concurrent recovery of water, resource and energy together with zero-solid discharge.