Invertebrate seedbanks: rehydration of soil from an unregulated river floodplain in the south‐eastern U.S.

Abstract

1. We investigated the responsiveness of aquatic invertebrates to rehydration of floodplain soil in a south-eastern U.S. river floodplain. Non-inundated soil divots containing invertebrate seedbanks were collected from three floodplain elevations with different inundation histories (inundated for 2, 38, and 78% of a year), and subjected to rehydration (experimental inundation) in aquaria for 10 weeks. 2. Before rehydration, samples were collected to assess the initial density and composition of invertebrates in non-inundated soil at each elevation. After rehydration, benthic samples were collected biweekly and emergence of aquatic insects was collected weekly from aquaria. 3. The surviving invertebrates were classified as aquatic, semi-aquatic and terrestrial. Some aquatic invertebrates survived the non-inundated period in an active state (e.g. Chironomidae and Ceratopogonidae), while others appeared to be dormant (e.g. Heptageniidae, microcrustaceans and Chironomidae). The response for several invertebrates (e.g. Chironominae, Oligochaeta, Collembola and terrestrial invertebrates) depended on the length of rehydration and inundation history. 4. The capacity of aquatic invertebrates to survive and recover was greatest at the most frequently inundated site. Despite variation in floodplain environments, both active and dormant invertebrates persisting in non-inundated floodplain soil contributed to the floodplain assemblage during flooding. Thus, maintaining the connection between river and floodplain appears to be important in sustaining the invertebrate seedbank and its capacity to recover during inundation. River channelisation and regulation that severs this connection may result in a loss of diversity and abundance.

Invertebrate and microbial responses to inundation in an ephemeral river reach in New Zealand: effects of preceding dry periods

“…Other aquatic taxa may survive dry periods as active larvae. For example, chironomid dipterans from the subfamilies Orthocladiinae and Chironominae are frequently classed as desiccation-tolerant, active larvae (e.g., Tronstad et al, 2005), and Orthocladiinae were common in our samples after dry periods > 200 d. However, some chironomids in ephemeral environments undergo anhydrobiosis (Kikawada et al, 2005), and it is not clear whether assumptions about active larvae are accurate.…”

“…Hot moments include metazoan responses as well as microbial responses. Inundation of dry substrata can trigger hatching in desiccation-resistant eggs and cysts of aquatic invertebrates, and terminate diapause and aestivation (Brock et al, 2003;Tronstad et al, 2005). For terrestrial invertebrates that colonize ephemeral river channels during dry periods, inundation kills some organisms, and cues others to migrate or enter inundation-resistant stages (Tamm, 1984;Adis and Junk, 2002).…”

Just add water: sources of chironomid drift in a large river floodplain

“…All of these colonization pathways have been demonstrated to occur for floodplain invertebrate communities (e.g., Smock, 1999), and specifically among Chironomidae. Certain chironomid species exploit temporary water sources with several different life history strategies, including desiccation-resistant eggs (Tronstead et al, 2005) and larvae (Cantrell & McLachlan, 1982), drought resistant cocoon formation and diapause (Grodhaus, 1980;Steinhart, 2000a, b), and rapid colonization by ovipositing females (Clement et al, 1977). Although several of these potential floodplain colonization pathways have been examined for zooplankton (Jenkins & Boulton, 2003), we are not aware of similar work on the colonization of floodplain waters by aquatic insects.…”

Recolonisation potential of zooplankton propagule banks in natural and agriculturally modified sections of a semiarid temporary stream (Doñana, Southwest Spain)

“…Propagule banks in temporary wetlands are important sources of species diversity and facilitate the recolonisation of the watercolumn by many aquatic invertebrates after rehydration of the habitat (Wiggins et al, 1980;Gyllstrom & Hansson, 2004;Tronstad et al, 2005). Emergence patterns from propagule banks are potentially useful indicators of the ecological integrity of wetlands (Angeler & Garcia, 2005).…”