The hyporheic zone and its functions: revision and research status in Neotropical regions

Abstract

The hyporheic zone (HZ), as the connecting ecotone between surface-and groundwater, is functionally part of both fluvial and groundwater ecosystems. Its hydrological, chemical, biological and metabolic features are specific of this zone, not belonging truly neither to surface-nor to groundwater. Exchanges of water, nutrients, and organic matter occur in response to variations in discharge and bed topography and porosity. Dynamic gradients exist at all scales and vary temporally. Across all scales, the functional significance of the HZ relates to its activity and connection with the surface stream. The HZ is a relatively rich environment and almost all invertebrate groups have colonized this habitat. This fauna, so-called hyporheos, is composed of species typical from interstitial environment, and also of benthic epigean and phreatic species. The hyporheic microbiocenose consists in bacteria, archaea, protozoa and fungi. The HZ provides several ecosystem services, playing a pivotal role in mediating exchange processes, including both matter and energy, between surface and subterranean ecosystems, functioning as regulator of water flow, benthic invertebrates refuge and place of storage, source and transformation of organic matter. The hyporheic zone is one of the most threatened aquatic environments, being strongly influenced by human activities, and the least protected by legislation worldwide. Its maintenance and conservation is compelling in order to preserve the ecological interconnectivity among the three spatial dimensions of the aquatic environment. Although several researchers addressed the importance of the hyporheic zone early, and most contemporary stream ecosystem models explicitly include it, very little is known about the HZ of Neotropical regions. From a biological standpoint, hyporheos fauna in Neotropical regions are still largely underestimated. This review focuses on a brief presentation of the hyporheic zone and its functions and significance as an ecotone. We also highlighted the key aspects considering also the current status of research in Neotropical regions.Keywords: Enterobacteriaceae, groundwater, meiofauna, macroinvertebrates, water exchange. A zona hiporréica e as suas funções: revisão e estado da arte da pesquisa na região neotropical ResumoA zona hiporréica, como ecótono de ligação entre a superfície e as águas subterrâneas, é parte funcional seja dos ecossistemas fluviais seja das águas subterrâneas. As características hidrológicas, as características químicas, biológicas e metabólicas são específicas desta zona, não pertencendo verdadeiramente nem a superfície nem às águas subterrâneas. Trocas de água, nutrientes e matéria orgânica ocorrem em resposta a variações na descarga, topografia do álveo e porosidade. Gradientes dinâmicos existem em todas as escalas e variam temporalmente. Em todas as escalas, o significado funcional da zona hyporheic relaciona-se com a sua conexão e atividades com a água superficial. O HZ é um ambiente relativamente rico e quase todos os grupos de ...

Effects of Student-Induced Trampling on Aquatic Macroinvertebrates in Agricultural Headwater Streams

“…We also observed that the majority of the taxa captured in all riffle types on each sampling day were small-bodied macroinvertebrates that may have resided below the sediment surface and been less prone to catastrophic drift or being crushed by moving substrate. Six (Leuctridae, Hydracarina, Chironomidae, Tipulidae, Baetidae, Elmidae) of the eight most common taxa we found have been documented in the hyporheic zone [50][51][52][53] and these taxa are all characterized by a flexible, elongate body shape and/or small body size suspected to confer mobility advantages in navigating the interstices [50]. Furthermore, substrate disturbances are known to knock loose and remove fine particles of sediment and organic matter, thus opening more interstitial space for hyporheic dwellers [54].…”

Evaluation of Meiofauna in the Hyporheic Zone of the Beberibe River, Pernambuco, Brazil

“…Meiofaunal and microbiotic communities have strong interactions. In the hyporheic zone, biogeochemical cycling, microbial ecology, and the ecology of invertebrate communities should not be considered as discrete systems, but rather as being interactive (Mugnai et al, 2015). The hyporheic microbiocenose consists of bacteria, archaea, protozoa, and fungi; and can be found in the plankton system; in interstitial areas, both immobile and in movement form; and in biofilms (Griebler and Lueders, 2009).…”

“…The flowpath of water through the hyporheic zone is modified by friction with the biofilm that covers inorganic granules. Thus, it is understood that a microbial community increases flow resistance and may result in clogging of the drainage system (Mugnai et al, 2015). Given that meiofauna influence microbial growth and abundances in other benthic systems, meiofauna are likely to play a central role, and influence many processes in the hyporheic stream (Hakenkamp and Palmer, 2000).…”

Integrating ecosystem services into conservation strategies for freshwater and marine habitats: a review

“…Many aquatic habitats are transitional ecotones (e.g. marine intertidal zones, mangrove belts, riparian zones, hyporheic zones) across which services flow and where gradients in ecosystem functions provide numerous ecosystem services (Sanon et al, ; Clerici et al, ; Mugnai et al, ). Conservation of ecosystem services in these transitional habitats, especially at the land–water interface, is particularly challenging because of jurisdictional ambiguities between administrations, competing demands for ecosystem services and inherent vulnerability to terrestrial and aquatic pressures (Walters et al, ; Maltby et al, ).…”