SUMMARY1. The aquatic invertebrate 'seedbank' comprises life stages that remain viable in the bed sediments of temporary freshwaters during dry phases. This seedbank promotes persistence of temporary-stream macroinvertebrates, but how its inhabitants respond to extended dry phases or repeated transitions between wet and dry phases remains unknown. 2. We rehydrated samples collected from the dry bed of a temperate-zone stream during a supra-seasonal drought, to examine the seedbank assemblage. Samples were first collected in autumn, from 12 sites along the ephemeral (4 sites), intermittent (2) and near-perennial (6) reaches, which had been dry for up to 8 months. Our first hypothesis was that assemblage composition would be related to the dry-phase duration preceding sampling, with longer dry phases reducing abundance and richness. 3. We revisited the same sites in three subsequent seasons, collecting and rehydrating sediments from all dry sites: five sites in early spring, three in late spring and four in late summer. Unpredictable flow resumption and redrying occurred between sampling dates. Our second hypothesis was that repeated wet-dry cycles would not degrade the assemblage because temporary-stream taxa would be adapted to fluctuating hydrological conditions. 4. Multiple individuals of only Chironomidae, Oligochaeta and Pisidium were present at sites that experienced the longest dry phases, providing some support for our first hypothesis. An additional 21 taxa were recorded across the remaining (shorter dry phase) sites in autumn, indicating that such sites act as refuges and potential recolonist sources following flow resumptions. 5. Although several insect orders first recorded in early spring were absent in later seasons, taxon-specific life cycles indicated that these absences were probably seasonal and not due to repeated wet-dry cycles. 6. We recorded 38 taxa in total, highlighting the seedbank as a dry-phase resistance mechanism for many temporary-stream macroinvertebrates. Our results also suggest that seedbank diversity may be threatened by increases in drought extent and duration.

The identification of hydrological indices for the characterization of macroinvertebrate community response to flow regime variability. Hydrological Sciences Journal, 59 (3-4), 645-658.Abstract The importance of flow regime variability for maintaining ecological functioning and integrity of river ecosystems has been firmly established in both natural and anthropogenically modified systems. River flow regimes across lowland catchments in eastern England are examined using 47 variables, including those derived using the Indicators of Hydrologic Alteration (IHA) software. A principal component analysis method was used to identify redundant hydrological variables and those that best characterized the hydrological series (1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005). A small number of variables (<6) characterized up to 95% of the statistical variability in the flow series. The hydrological processes and conditions that the variables represent were found to be significant in structuring the in-stream macroinvertebrate community Lotic-invertebrate Index for Flow Evaluation (LIFE) scores at both the family and species levels. However, hydrological variables only account for a relatively small proportion of the total ecological variability (typically <10%). The research indicates that a range of other factors, including channel morphology and anthropogenic modification of in-stream habitats, structure riverine macroinvertebrate communities in addition to hydrology. These factors need to be considered in future environmental flow studies to enable the characterization of baseline/reference conditions for management and restoration purposes.

24The duration, intensity and frequency of hydrological droughts are predicted to increase significantly 25 over the 21 st century globally, threatening the long-term stability of lotic communities. In this paper 26 we examine the recovery and recolonization of macroinvertebrate taxa in ephemeral and near 27 perennial reaches of the River Lathkill (UK) after a supra-seasonal drought event. Following flow 28 resumption, species accumulation (recolonization) occurred rapidly over a four-month period, with a 29 steady increase observed thereafter. Taxonomic richness was significantly higher in the section with 30 near perennial flow after the first month of the study than the naturally ephemeral reach. Serial 31 correlation was observed in the near perennial section but not in the upstream ephemeral reach. Serial 32 correlation in the near perennial section may reflect: (1) the ongoing process of recovery or (2) the 33 macroinvertebrate community following a new ecological trajectory. Our results suggest that supra-34 seasonal droughts may cause initial reductions in lotic diversity during stream desiccation events but 35 may re-set ecological succession and / or temporarily provide new ecological niches, thereby 36 supporting increased taxonomic diversity when the full range of hydrological conditions are 37 considered. Quantifying the recovery of ecological communities following supra-seasonal drought can 38 provide information to help develop ecologically effective conservation and management strategies. 39 40 streams, lotic habitat. 42Global climate models predict that the duration, intensity and frequency of drought events are likely 43 to increase significantly over the 21st century (Prudhomme et al. 2014). Climatic variability combined 44 with increasing abstraction pressures and the construction of artificial impoundments to supply 45 increasing human populations globally, is likely to increase the number of waterbodies that 46 experience channel drying (Larned et al. 2010), extend the duration of drying events in waterbodies 47 that already experience dewatering (Benejam et al. 2010; Rahiz and New 2013; Skoulikidis et al.48 2017) and lead to significant changes to biological communities, such as the loss of taxa poorly 49 adapted to drying events (Datry et al. 2014).50 51 Supraseasonal drought is defined here as an extended duration of reduced rainfall and surface water 52 availability over multiple seasons or years (Lake 2011). This differs from seasonal drought which is 53 characterised by seasonal reductions in rainfall and water availability, such as those regularly 54 experienced in semi-arid or Mediterranean ecosystems (Gasith and Resh 1999). Extreme, high 55 magnitude but low frequency supra-seasonal events may significantly increase the spatial and 56 temporal extent of stream drying (Boulton 2003; Wood and Armitage 2004) and in some instances 57 affect historically perennially flowing sites (Stubbington et al. 2015).58 59 Surface water drying is a primary determinant of aquatic floral and faunal di...