Flooding drives a macroinvertebrate biomass boom in ephemeral floodplain wetlands

McInerney, Paul; Stoffels, Rick J.; Shackleton, Michael; Davey, Chris D.

doi:10.1086/694905

Cited by 31 publications

(15 citation statements)

References 65 publications

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“…Water chemistry was affected by an increase in six variables, including the nutrient TN and a decrease in the nutrient SRP. Our observed increase in TN may be associated with its release from terrestrial litter accumulation over time (Baldwin & Mitchell, 2000;McInerney et al, 2017). An increase in TP may not have been documented here as SRP decreased presumably by uptake from aquatic plants.…”

Section: Relationships Between Time Since Connection and Water Chemismentioning

confidence: 77%

“…Following inundation of dry oodplain wetlands nutrients are released from sediments stimulating primary and secondary production (Lake et al, 2006;McInerney et al, 2017). Invertebrates occupy an important role in oodplain wetlands linking aquatic and terrestrial carbon sources and nutrients to higher trophic levels such as sh and waterbirds (Boon & Shiel, 1990;Lindholm & Hessen, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Effects of Inundation on Water Chemistry and Invertebrates in Floodplain Wetlands

Tsoi¹,

Growns²,

Southwell³

et al. 2021

Preprint

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Floodplain wetlands play a significant role in the storage of sediment and water and support high levels of nutrient cycling that lead to substantial primary production and high biodiversity. This storage, cycling and production system is driven by intermittent inundation. In regulated rivers the link between channel flows and floodplain inundation is often impacted with reduction in the frequency and duration of inundation. Managed floodplain inundation is us being used as a tool to help restore floodplain wetland processes and rehabilitate river systems. However, the use of managed water for the environment remains contentious and it is important to quantify the outcomes of re-introducing water to floodplain wetland systems. We examined the effects of environmental floodplain watering on water chemistry and three groups of invertebrates, including benthic and pelagic invertebrates and macroinvertebrates, in wetlands on the Gwydir River system in the north of the Murray-Darling Basin. We hypothesised that wetlands that were inundated for longer periods of time would have altered water chemistry and support a greater richness and abundance of invertebrates, thus altering their assemblage structures. Water chemistry and the assemblage structure of all three invertebrate groups in the wetlands was significantly influenced by the time since connection (TSC) to their respective rivers and therefore inundation period. The microinvertebrate abundance of was positively associated with TSC, but not macroinvertebrates. This suggests that the duration of connection between the channel and floodplain is important in maintaining the ecology and food webs in the wetlands.

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Section: Relationships Between Time Since Connection and Water Chemismentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Effects of Inundation on Water Chemistry and Invertebrates in Floodplain Wetlands

Tsoi¹,

Growns²,

Southwell³

et al. 2021

Preprint

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show abstract

“…Conceptual diagram synthesizing mechanisms by which floodplains may influence essential nutrient dynamics in riverine food webs: (1) Initial flood pulse and floodplain connectivity—liberation of DOC from terrestrial litter and nutrient release from floodplain sediments (e.g., McInerney et al 2017). (2) Disconnection—DOC and nutrients drive microbial activity in floodplain habitats, including synthesis of essential nutrients by algae and bacteria.…”

Section: Discussionmentioning

confidence: 99%

“…We expected that planktonic organic matter sources in the water column (i.e., seston) would be a dynamically controlling basal food resource for aquatic animals (Hladyz et al 2012). In light of inundation responses of aquatic invertebrates (e.g., increased biomass—McInerney et al 2017) and fish (e.g., increased recruitment and body condition—Beesley 2012) inhabiting floodplains, we hypothesized that wetland and anabranch habitats would sustain higher concentrations of dissolved organic carbon (leached from floodplain litter) and planktonic algae within the water column than river habitats. Subsequently, we expected that wetland and anabranch seston would supply higher concentrations of essential fatty acids for animals than seston in the river channel.…”

mentioning

confidence: 99%

Basal resource quality and energy sources in three habitats of a lowland river ecosystem

McInerney

Holt

Lester

et al. 2020

Limnology & Oceanography

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Understanding energy flow through ecosystems and among sub-habitats is critical for understanding patterns of biodiversity and ecosystem function. It can also be of considerable applied interest in situations where managing for connectivity among habitats is important for restoring degraded ecosystems. Here, we describe patterns of basal resource quality and identify primary basal energy sources in three habitats-river channels, anabranches and wetlands-of a lowland river floodplain in the Murray River catchment, Australia during a period of disconnected surface flow. We used a combination of stable isotope and fatty acid analyses to determine which basal resources were assimilated by the backswimmer Anisops thienemanni and the Eastern mosquitofish Gambusia holbrooki and assessed food quality across the three habitats. Seston was a primary basal resource for both animals in all three habitats, but was of higher quality within floodplain habitats than in the river channel. Although floodplain seston contained higher concentrations of essential fatty acids, fatty acid profiles of animals from different habitats remained similar. Our research suggests that inundation of floodplains and subsequent reconnection to the river could be valuable to afford riverine animals the opportunity to access high quality resources, but highlights a need to quantitatively assess the transfer of essential fatty acids between trophic levels to determine how much riverine animals are in fact limited by poorer quality food resources. We demonstrate the importance of estimating the quality of organic matter fluxes into food webs, and the potential role of targeted environmental flows to re-establish high quality energy pathways in riverine ecosystems. Food webs represent an important facet of ecosystem function and describe the energy pathways between resources and animals (Hladyz et al. 2012). Within freshwater ecosystems, research has focused on understanding the contribution and importance of terrestrially-and aquatically-derived carbon to food webs (e.g., Rees et al. 2020). Less attention has been oriented towards determining the quality of food resources (e.g., Guo 2018) and the dominant pathways for energy to reach higher trophic levels. Understanding which resources underpin food webs and factors influencing resource availability to animals is key to improving our capacity to gauge ecosystem health (Holland et al. 2020). Food quality, in its coarsest form, may be assessed by ecological stoichiometry (e.g., C : N) however, animals can be limited by availability of complex organic compounds such as amino acids (Dwyer et al. 2018), sterols and fatty acids (Twining et al. 2016). Within freshwater ecosystems, algae and, in particular, diatoms are considered high-quality food resources for herbivorous taxa due to their high concentration of inorganic nutrients (nitrogen and phosphorous) and longchain polyunsaturated fatty acids (e.g. Guo 2018). Some omega-3 (ω3) and omega-6 (ω6) polyunsaturated fatty acids, such as eicosapentaenoic (EPA;...

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“…Given this general shift in diet, growth of larger adult Murray cod may increase most during years that coincide with high rates of production of forage fishes and larger crustaceans. In river‐floodplain systems, such years are usually characterized by a flood pulse of some magnitude, whereupon rewetting of habitats higher in the riverscape results in pulses of energy through the food web (Balcombe & Arthington, 2009; Bayley, 1991; Benke, 2001; McInerney et al., 2017; Winemiller, 2004).…”

Section: Discussionmentioning

confidence: 99%

Stage‐dependent effects of river flow and temperature regimes on the growth dynamics of an apex predator

Stoffels

Weatherman

Bond

et al. 2020

Global Change Biology

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In the world's rivers, alteration of flow is a major driver of biodiversity decline. Global warming is now affecting the thermal and hydrological regimes of rivers, compounding the threat and complicating conservation planning. To inform management under a non-stationary climate, we must improve our understanding of how flow and thermal regimes interact to affect the population dynamics of riverine biota. We used long-term growth biochronologies, spanning 34 years and 400,000 km 2 , to model the growth dynamics of a long-lived, apex predator (Murray cod) as a function of factors extrinsic (river discharge; air temperature; sub-catchment) and intrinsic (age; individual) to the population. Annual growth of Murray cod showed significant, curvilinear, life-stage-specific responses to an interaction between annual discharge and temperature. Growth of early juveniles (age 1+ and 2+ years) exhibited a unimodal relationship with annual discharge, peaking near median annual discharge. Growth of late juveniles (3+ to 5+) and adults (>5+) increased with annual discharge, with the rate of increase being particularly high in adults, whose growth peaked during years with flooding. Years with very low annual discharge, as experienced during drought and under high abstraction, suppress growth rates of all Murray cod life-stages. Unimodal relationships between growth and annual temperature were evident across all life stages. Contrary to expectations of the Temperature Size Rule, the annual air temperature at which maximum growth occurred increased with age. The stage-specific response of Murray cod to annual discharge indicates that no single magnitude of annual discharge is optimal for cod populations, adding further weight to the case for maintaining and/or restoring flow variability in riverine ecosystems. With respect to climate change impacts, on balance our results indicate that the primary mechanism by which climate change threatens Murray cod growth is through alteration of river flows, not through warming annual mean temperatures per se.

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Flooding drives a macroinvertebrate biomass boom in ephemeral floodplain wetlands

Cited by 31 publications

References 65 publications

Effects of Inundation on Water Chemistry and Invertebrates in Floodplain Wetlands

Effects of Inundation on Water Chemistry and Invertebrates in Floodplain Wetlands

Basal resource quality and energy sources in three habitats of a lowland river ecosystem

Stage‐dependent effects of river flow and temperature regimes on the growth dynamics of an apex predator

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