Seasonal increases in fish trophic niche plasticity within a flood‐pulse river ecosystem (Tonle Sap Lake, Cambodia)

Pool, Thomas K.; Holtgrieve, Gordon W.; Elliott, Vittoria; McCann, Kevin S.; McMeans, Bailey; Rooney, Neil; Smits, Adrianne P.; Thach, Phanara; Cooperman, Michael S.; Clark, Sydney; Phen, Chheng; Chhuoy, Samol

doi:10.1002/ecs2.1881

Cited by 55 publications

(49 citation statements)

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“…Lastly, similar patterns were observed in a flood‐pulse ecosystem whereby the niche widths and isotopic values of different species of fish expanded/contracted and shifted within δ‐space during the wet (when floodplain habitat was inundated thereby increasing the range of feeding habitats and or diversity in available food resources) vs. the dry season, respectively (Pool et al. ).…”

Section: Discussionsupporting

confidence: 56%

Trophic compression of lake food webs under hydrologic disturbance

et al. 2018

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. 2018. Trophic compression of lake food webs under hydrologic disturbance. Ecosphere 9(6):e02304. 10. 1002/ecs2.2304 Abstract. The need to protect biostructure is increasingly recognized, yet empirical studies of how human exploits affect ecological networks are rare. Studying the effects of variation in human disturbance intensity from decades past can help us understand and anticipate ecosystem change under alleviated or amplified disturbance over decades to come. Here, we use stable isotopes and an innovative analytical approach to compare the food webs of two akin lake ecosystems subject to disparate water use regimes, a pervasive, yet unappreciated stressor. We show that intensive water use (persistent, early season, rapid lake-level drawdown) can compress trophic diversity by 46%, necessitating reorganization of biostructural elements configuring lake food webs. Compression occurred over the d 13 C axis indicating erosion of basal trophic diversity, but food chain length remained intact over the period and intensity of disturbance examined. This study demonstrates the potential for water use, like other disturbances (warming, eutrophication, and invasive species), to mute opportunity for benthic-pelagic coupling and benefits to lake food webs and the inherent capacity of lake ecosystems to adapt to stress. Trophically compressed lakes may be less able to adapt to intensified water use.

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Section: Discussionsupporting

confidence: 56%

Trophic compression of lake food webs under hydrologic disturbance

et al. 2018

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“…In this study, we investigate how the TSL fish assemblage composition varies across floodplain mesohabitats and seasons. Despite advances in our understanding of TSL hydro‐ecological processes, including trophic interactions (Pool et al., ), flood pulse dynamics (Arias et al., ), and energy transfer (Costa‐Cabral et al., ; Holtgrieve et al., ) at the whole system scale, interactions among the lake's hydrology, floodplain mesohabitats and food web structure remain largely unexplored. Thus, we investigate fishes’ taxonomic patterns within the TSL and identify how their life‐history characteristics underpin those patterns within the complex floodplain environment.…”

Section: Introductionmentioning

confidence: 99%

Fish assemblage composition within the floodplain habitat mosaic of a tropical lake (Tonle Sap, Cambodia)

et al. 2019

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Understanding how habitat heterogeneity is linked to biodiversity patterns within flood–pulse catchments is needed for their effective conservation. To study those communities, researchers have begun to explore how local environmental factors influence species composition patterns at relatively fine scales within complex habitat mosaics. However, a robust description of the link between communities’ composition and their floodplain habitat characteristics remains poorly articulated. In the Tonle Sap Lake (TSL) of Cambodia, we evaluated whether mesohabitat‐scale (1–5 km) factors throughout the floodplain structured the fish assemblage temporally and spatially. First, we determined whether TSL fish assemblage changed seasonally and, if so, what assemblage components were driving that change. Second, we determined whether environmental factors structured fish composition across floodplain mesohabitat patches during the wet season. Third, we evaluated whether dominant species displayed affinities for specific areas within the floodplain during the wet season, potentially identifying critical mesohabitat patches for the fish assemblage. Fish were collected from nine sites along an elevational gradient traversing the floodplain every 3 months from March 2014 through January 2015. Correspondence analysis and analysis of variance were used to assess seasonal variation in the species composition. Canonical correspondence analysis and a mantel test were then used to identify the significance of environmental factors structuring the fish assemblage. Fish assemblages changed across seasons; in particular, migratory species occurrence decreased during the dry season. During the wet season, the fish assemblage was structured spatially by mesohabitat‐scale factors such as vegetation and water quality. Furthermore, the flooded forest mesohabitat directly adjacent to the permanent lake displayed particularly high species richness and abundance. However, a majority of TSL species appeared to be highly mobile, occurring across multiple floodplain mesohabitats. We concluded that fish assemblage structure and floodplain mesohabitat use within TSL may depend strongly upon the maintenance of the natural flow regime. Since the flow regime will probably be modified by upstream dam development, trade‐offs will emerge between the cycle of fishing on which local residents depend, and the hydropower and agricultural benefits of damming the Mekong River system.

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“…At a community level, diet diversity within and among species is widely considered important for dampening competition and promoting coexistence of fishes in tropical floodplains (Winemiller and Pianka , Pool et al. , Costa‐Pereira et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…, Pool et al. ). Some evidence argues for consistent increases in trophic position across the fish assemblage during the dry season (Wantzen et al.…”

Section: Introductionmentioning

confidence: 99%

Consumer trophic positions respond variably to seasonally fluctuating environments

McMeans

Kadoya

Pool

et al. 2019

Ecology

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The effects of environmental seasonality on food web structure have been notoriously understudied in empirical ecology. Here, we focus on seasonal changes in one key attribute of a food web, consumer trophic position. We ask whether fishes inhabiting tropical river–floodplain ecosystems behave as seasonal omnivores, by shifting their trophic positions in relation to the annual flood pulse, or whether they feed at the same trophic position all year, as much empirical work implicitly assumes. Using dietary data from the Tonle Sap Lake, Cambodia, and a literature review, we find evidence that some fishes, especially small piscivores, increased consumption of invertebrates and/or plant material during the wet season, as predicted. However, nitrogen stable isotope (δ15N) data for 26 Tonle Sap fishes, spanning a broader range of functional groups, uncovered high variation in seasonal trophic position responses among species (0 to ±0.52 trophic positions). Based on these findings, species respond to the flood pulse differently. Diverse behavioral responses to seasonality, underpinned by spatiotemporal variation at multiple scales, could be central for rerouting matter and energy flow in these dynamic ecosystems. Seasonally flexible foraging behaviors warrant further study given their potential influence on food web dynamics in a range of fluctuating environments.

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Seasonal increases in fish trophic niche plasticity within a flood‐pulse river ecosystem (Tonle Sap Lake, Cambodia)

Cited by 55 publications

References 55 publications

Trophic compression of lake food webs under hydrologic disturbance

Trophic compression of lake food webs under hydrologic disturbance

Fish assemblage composition within the floodplain habitat mosaic of a tropical lake (Tonle Sap, Cambodia)

Consumer trophic positions respond variably to seasonally fluctuating environments

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