The use of palaeoecological and contemporary macroinvertebrate community data to characterize riverine reference conditions

Abstract

Defining reference conditions is a crucial element in quantifying the extent of anthropogenic modification and for identifying restoration targets in riverine ecosystems. Despite palaeoecological approaches being widely applied in lakes to establish reference conditions, their use in lotic ecosystems remains limited. In this study, we examine contemporary, historical (1930 and 1972), and palaeoecological macroinvertebrate biodiversity and biomonitoring scores in Eastburn Beck, a headwater tributary of the River Hull (UK) to determine if palaeoecological approaches can be used to characterize lotic system reference conditions. Palaeoecological samples comprised a greater gamma diversity (18 taxa) than contemporary samples (8 taxa), samples taken in 1972 (11 taxa) and 1930 (8 taxa). Palaeoecological samples supported taxonomically different Gastropoda, Trichoptera, and Coleoptera (GTC) communities compared with contemporary and historical samples (1930 and 1972). Results from biomonitoring indices using the GTC community indicated that the palaeochannel had (a) similar invertebrate biological quality, (b) a less energetic flow regime, and (c) increased fine sediment deposits compared with the contemporary channel. The results clearly illustrate that palaeoecological data can provide a suitable method to characterize reference conditions for lotic habitats. However, it is important to recognize that faunal data from palaeochannel deposits provide a short‐term “snapshot” of the conditions within the river immediately prior to its hydrological isolation. River restoration activities should therefore draw on multiple lines of evidence, including palaeoecological information where possible, to characterize a range of reference conditions to reflect the highly dynamic nature of lotic ecosystems.

Learning from the past: opportunities for advancing ecological research and practice using palaeoecological data

“…This is because restoration and rewilding are inherently about recreating previous ecological conditions. Detailed understanding of past habitats, species dynamics and ecological interactions is essential both to allow restoration aims to be clearly articulated and to inform optimal methods to realise those aims (Seddon et al 2019). For example, it was always assumed that, during the climax communities found in Europe after the last ice age ~4,000-9,000 years ago, land was covered by continuous and relatively-closed wildwood.…”

“…While Webb and Goodenough's study involved using palaeoecological data to test the appropriateness of an indictor system widely-used in modern ecological contexts, the work of Seddon et al (2019) provides a nice example of how the same indicator system can be used to enable temporal comparisons when applied to palaeoecological, historical and contemporary data, this time within the aquatic environment. The authors compared data on Gastropoda, Trichoptera and Coleoptera using Biological Monitoring Working Party (BMWP) and Average Score Per Taxon (ASPT) biotic indices (Furse et al 1981;Armitage et al 1983) to consider likely oxygen levels, and thus water quality, in a UK chalk river from the ~1840s to 2011.…”

“…Examples include studies in terrestrial New Zealand (Wilmshurst et al 2013), freshwater ecosystems in the UK (Bennion et al 2018;Bishop et al 2019) and marine environments off the west coast of the Iberian Peninsula (Ribeiro et al 2012) and in the Mediterranean (Agiadi and Albano 2020). These "recent past" timeframes are often vital to understand current patterns and processes in terrestrial and marine environments (Finney et al 2002;Rull 2010), and palaeoecological approaches are especially valuable where there are incomplete primary survey data or documentary evidence (Davidson et al 2005;Salgado et al 2010;Bishop et al 2019;Seddon et al 2019). A terrestrial example of this is afforded by Sherriff et al (2014), who undertook spatiallyexplicit modelling of fire regimes in Colorado over 300 years using both primary survey and palaeoecological data to show that recent fires were larger than those experienced historically and to identify specific high-risk areas outside of historical norms.…”

Professor Geoffrey Petts (1953–2018): An outstanding interdisciplinary river scientist

“…Gell, Reid, and Wilby () consider even longer‐term changes in the floodplain wetlands of the southern Murray Darling basin, Australia but emphasise more recent consequences of human actions and an adaptive management framework, which may drive a pathway towards more sustainable management in the future. Finally, Seddon et al () illustrate how investigations of palaeoecological and contemporary macroinvertebrate communities can provide evidence to characterise reference lotic conditions and in doing so provide a direct link between themes 7 and 8.…”

Considering the Adaptive Cycle and Resilience of the Ecosystem to Define Reference Conditions for Wetland Restoration

“…The European Union provided a strategy for the protection and restoration of aquatic ecosystems; the goal was to find a point that did not exhibit impact of human activities based on paleoecology and then use it as a marker for lake restoration efforts (European Union, 2000). There are many examples worldwide defining reference conditions for wetland restoration based on these methods (Clarkson et al., 2017; Dearing et al., 2012; Kress et al., 2019; Proulx et al., 2018; E. Seddon et al., 2019), which contributes greatly to wetland management. Nevertheless, most cases failed to consider the ecosystem's adaptive cycle and resilience to human pressures.…”