Longitudinal variability in lateral hydrologic connectivity shapes fish occurrence in temporary floodplain ponds

Dynamic flow regimes maintain critical connections between main channel and adjacent floodplain habitats that provide fish access to shelter, foraging, and spawning opportunities. Our study advances the understanding of these processes by exploring the importance of coupled longitudinal–lateral connectivity for determining species occurrence in headwater streams of the Amazon. Using a multispecies occupancy model, we revealed a clear pattern of species addition in the downstream direction in temporary floodplain ponds, associated with changes in the pool of potential colonists present in the channel and with increasing lateral hydrologic connectivity. Species that are more tolerant of stagnant waters and those able to disperse in shallow habitats (e.g., Anablepsoides micropus) occurred frequently in ponds along the entire longitudinal extent, whereas those species preferring lotic habitats were present only in the most downstream sites. We also observed increasing similarity of pond and channel communities with distance downstream. This study provides insights on the spatial structuring of tropical fish communities in response to flood-induced hydrologic connectivity and further highlights the vulnerability of floodplain fishes to modification in flooding regimes.

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Movement and mortality of Murray cod, Maccullochella peelii, during overbank flows in the lower River Murray, Australia

Australian Journal of Zoology ◽

10.1071/zo12124 ◽

2013 ◽

Vol 61 (2) ◽

pp. 160 ◽

Cited By ~ 16

Author(s):

Sandra J. Leigh ◽

Brenton P. Zampatti

Keyword(s):

Dissolved Oxygen ◽

Large Scale ◽

Main Channel ◽

Small Scale ◽

Substantial Impact ◽

Endangered Fish ◽

Flood Peak ◽

Murray Cod ◽

Floodplain Habitats ◽

Overbank Flows

Conservation of Murray cod (Maccullochella peelii), a large endangered fish species of Australia’s Murray–Darling Basin, relies on a detailed understanding of life history, including movement patterns and habitat use. We used radio-tracking to investigate the movement of 36 Murray cod in main channel and anabranch habitats of the lower River Murray during a flood and associated hypoxic blackwater event. During a flood peak of ~93 000 ML day–1, dissolved oxygen decreased to 1.2 mg L–1. Four movement types were observed: (1) localised small-scale movement, (2) broad-scale movement within anabranch habitats, (3) movement between anabranch and main channel habitats, and (4) large-scale riverine movement. Murray cod exhibited high fidelity to anabranch habitats but also moved extensively between anabranches and the main channel. Fish were consistently located in the main channel or permanent anabranches, suggesting that use of ephemeral floodplain habitats is limited, and highlighting the importance of connectivity between off-channel and main channel habitats. Mortality of radio-tagged fish was considerable (25%) in association with low dissolved oxygen concentrations, indicating that hypoxic blackwater may have had a substantial impact on Murray cod populations in the lower River Murray.

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Modelling floodplain conveyance in compound channel flows

Canadian Journal of Civil Engineering ◽

10.1139/l95-078 ◽

1995 ◽

Vol 22 (4) ◽

pp. 660-667 ◽

Cited By ~ 1

Author(s):

Jean G. Chatila ◽

Ron D. Townsend

Keyword(s):

Field Data ◽

Single Channel ◽

Laboratory Data ◽

Main Channel ◽

Channel Flows ◽

Interface Plane ◽

Data Sets ◽

Compound Channel ◽

Dynamic Flow ◽

Composite Flow

Floodplain conveyance in compound channel flows is examined through applications of the dynamic flow routing model DWOPER to both laboratory and field data sets. Three different approaches regarding the modelling of off-channel storage are considered, namely, the single-channel approach and two interface-plane methods, which artificially separate main channel flows from floodplain flows, using (i) vertical and (ii) diagonal interface planes. The single-channel method, which views composite flow fields as single units without storage, produced significant differences between simulated and observed stage and discharge hydrographs. The vertical interface method gave generally good results in the case of the laboratory data, but was less successful when applied to the field data. The diagonal interface method, which in this instance applied outward-facing diagonal interface planes at the junctions of the main channel and floodplain zones, produced superior results overall. Key words: floodplain, conveyance, unsteady flow, compound channels, off-channel storage, interface planes.

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Flooding and hydrologic connectivity modulate community assembly in a dynamic river-floodplain ecosystem

10.1101/557405 ◽

2019 ◽

Author(s):

Stefano Larsen ◽

Ute Karaus ◽

Cecile Claret ◽

Ferdinand Sporka ◽

Ladislav Hamerlík ◽

...

Keyword(s):

Community Assembly ◽

Species Turnover ◽

Compositional Variation ◽

Hydrologic Connectivity ◽

Aquatic Communities ◽

Species Sorting ◽

River Floodplains ◽

Annual Dynamic ◽

Variation Explained ◽

Floodplain Habitats

SummaryBraided river floodplains are highly dynamic ecosystems, where aquatic communities are strongly regulated by the hydrologic regime. So far, however, understanding of how flow variation influences assembly mechanisms remains limited.We collected benthic chironomids and oligochaetes over a year across a lateral connectivity gradient in the semi-natural Tagliamento River (Italy). Four bankfull flood events occurred during the study, allowing the assessment of how flooding and hydrologic connectivity mediate the balance between stochastic and deterministic community assembly.While invertebrate density and richness were positively correlated with connectivity, diversity patterns showed no significant correlation. Species turnover through time increased with decreasing connectivity. Contrary to expectations, hydrologic connectivity did not influence the response of community metrics (e.g. diversity, density) to floods.Invertebrate composition was weakly related to connectivity, but changed predictably in response to floods. Multivariate ordinations showed that faunal composition diverged across the waterbodies during stable periods, reflecting differential species sorting across the lateral gradient, but converged again after floods. Stable hydrological periods allowed communities to assemble deterministically with prevalence of non-random beta-diversity and cooccurrence patterns and larger proportion of compositional variation explained by local abiotic features. These signals of deterministic processes clearly declined after flooding events. This occurred despite no apparent evidence of flood-induced homogenisation of habitat conditions.This study is among the first to examine the annual dynamic of aquatic assemblages across a hydrologic connectivity gradient in a natural floodplain. Results highlight how biodiversity can exhibit complex relations with hydrologic connectivity. However, appraisal of the assembly mechanisms through time indicated that flooding shifted the balance from deterministic species sorting across floodplain habitats, towards stochastic processes related to organisms redistribution and the likely resetting of assembly to earlier stages.

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