Abstract
Resource pulses are thought to structure communities and food webs through the assembly of consumers. Aggregated consumers represent a high quality resource subsidy that becomes available for trophic transfer during and after the pulse. In estuarine systems, riverine flood pulses deliver large quantities of basal resources and make high quality habitat available for exploitation by consumers. These consumers represent a change in resources that may be available for trophic transfer. We quantified this increased consumer resource availability (nekton density, biomass, energy density) provided by riverine flood pulsing in Breton Sound, Louisiana, USA. We used water level differences between an area subject to two experimental riverine flood pulses (inflow) and a reference area not receiving inflow to identify the percentage of nekton standing stock and energy density that may be attributable solely to riverine pulsing and may represent a consumer resource subsidy. Riverine pulsing accounted for more than 60% of resident nekton density (ind m−2), biomass (g m−2), and energy density (cal m−2) on the flooded marsh surface during two experimental pulse events in 2005. Our results document the potential subsidy of resident nekton standing stock from a riverine flood pulse available for export to subtidal habitats. Given predicted large scale changes in river discharge globally, this approach could provide a useful tool for quantifying the effects of changes in riverine discharge on consumer resource availability.
Highlights
Resource pulses affect many terrestrial and aquatic systems and are thought to structure communities and food webs through the assembly of consumers, generalist species [1,2,3,4,5]
Several examples provide evidence of allochthonous resource subsidies propagating through secondary consumers in terrestrial and aquatic systems [6,7,8,9,10,11], yet there are few studies that document the value of the change in consumer resource availability that is made available by an estuarine resource pulse [12]
We propose to quantify the potential subsidy provided by riverine pulse events
Summary
Resource pulses affect many terrestrial and aquatic systems and are thought to structure communities and food webs through the assembly of consumers, generalist species [1,2,3,4,5]. Freshwater inflow delivers basal (terrestrial) resources to large expanses of estuarine habitat and makes high-quality habitat available for exploitation by consumers that rapidly assemble to flooded habitats. These consumers represent a measurable resource subsidy that will become available to higher-order pelagic consumers after the pulse ends [13,20]. Measuring the standing stock of these aggregated resident nekton during riverine flood pulses may provide a means to quantify the effects of the resource pulse and the resulting consumer subsidy available for trophic transfer to pelagic habitats
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