Macroinvertebrate seedbank composition in relation to antecedent duration of drying and multiple wet‐dry cycles in a temporary stream

Abstract

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.

Direct observations of the effect of fine sediment deposition on the vertical movement of Gammarus pulex (Amphipoda: Gammaridae) during substratum drying

“…Many macroinvertebrate populations persist during dry events by employing a range of survival strategies including behavioural adaptations, such as vertical movement into the saturated riverbed sediments (Stubbington, 2012;Vander Vorste et al, 2016a;Vadher et al, 2017), or physiological adaptations to desiccation (Strachan et al, 2015;Stubbington et al, 2016) and declining water quality (van Vliet & Zwolsman, 2008). Lotic macroinvertebrate taxa have been recorded and observed in the saturated subsurface sediments of drying streams, indicating that they may serve as a habitat where fauna may persist (Hose et al, 2005;Fenoglio et al, 2006), and from which populations may recolonize waterbodies following the resumption of flow (Vander Vorste et al, 2016a).…”

Aquatic insects in a multistress environment: cross-tolerance to salinity and desiccation

“…Some aquatic insects face droughts in situ in microrefuges (e.g. Stubbington et al, 2016), whereas others with flying adults disperse to more favourable wet habitats (Bilton, 2014;Strachan et al, 2015). During dispersal, aquatic insects may experience important water losses associated with exposure to the desiccating aerial medium and flight activity (Dudley, 2000).…”

Variación temporal de la diversidad taxonómica y rasgos funcionales de los macroinvertebrados acuáticos en ríos temporales en la isla de Providencia, Colombia

“…Esta resistencia se atribuye a la presencia de estructuras tales como branquias (Dero, Ancylidae Mf., Pyrgophorus), conchas para proteger el cuerpo o pigmentos como la hemoglobina (Chironomus), así como de mecanismos especializados que les permiten salvaguardarse de dichas condiciones. Estas formas de especialización de los macroinvertebrados ante las condiciones físicas y químicas adversas encontradas en la isla de Providencia concuerdan con lo hallado para ríos intermitentes de Australia, España y Estados unidos (Beche et al 2006, Bonada et al 2007, Dézerald et al 2015, Huryn et al 2008, Stubbington et al 2016). …”

“…Los rasgos que predominan varían dependiendo de si la sequía es estacional predecible o si es un evento impredecible (Bogan et al 2015, Lake 2003. En general, se ha encontrado en ecosistemas mediterráneos y templados que los rasgos funcionales asociados con mayor adaptación a la temporalidad son: ciclos vitales flexibles (sincronización de los ciclos de vida acuáticos con las temporadas de lluvias), desarrollo ligado con la temperatura del agua, diapausa, huevos protegidos contra la desecación y alto poder de dispersión (Bonada et al 2007, Boulton 1989, Dézerald et al 2015, Dole-Olivier et al 1997, Lake 2003, McDonough et al 2011, Stubbington et al 2016, Williams y Hynes 1977, así como alimentación de tipo generalista (Dieterich y Anderson 2000).…”