Multiproxy paleolimnological records provide evidence for a shift to a new ecosystem state in the Northern Great Plains, USA

Abstract

Wetlands in the Prairie Pothole Region of the North American Northern Great Plains perform multiple ecosystem services and are biodiversity hotspots. However, climatological changes can result in sudden shifts in these important ecosystems. For example, marked increases in precipitation in the last few decades have resulted in a widespread shift in wetlands across the Prairie Pothole Region to a new ecohydrological state. We used multiproxy analyses (diatom community composition and invertebrate stable isotopes) of 210Pb‐dated sediment cores from two adjacent, but morphologically and hydrologically different, prairie‐pothole wetlands to assess the effects of hydroclimatic variability on these wetland ecosystems. Our results provide evidence that the recent ecohydrological shift in the region's wetlands is unprecedented over the past ca. 178 yr. Oxygen stable isotopes in chironomid head capsules provide a record of paleohydrology changes. The most recent sediments (i.e., those deposited after the state shift) from both wetlands revealed novel changes in diatom communities that differed greatly from earlier community compositions. In addition, a depleted signal in deuterium and 13C carbon stable isotopes observed in chironomid head capsules and Daphnia ephippia, respectively, after 1993 is likely related to an increase in methane production in these wetlands. Our study highlights the importance of considering basin morphometry including whether a wetland has an overflow point, and multiple biological indicators to study climate‐change influences on freshwater ecosystems. Research using these techniques can lead to an improved understanding of recent ecosystem shifts, an understanding that will be essential for future climate‐change adaptation and mitigation in this ecologically important region.

Climate and Land Use Driven Ecosystem Homogenization in the Prairie Pothole Region

“…A major mechanism in these losses was the invasion of reed canary grass and hybrid cattails. The rise of invasive cattails and reed canary grass in shallow-marsh and wet-meadow zones has been observed in other studies within the region as well [94,104]. Jones, 2022, [74]) found that for many wetlands restored in North Dakota where heavily invaded by non-native cool season grasses, this was likely attributed to weak, natural wetland seed banks and mechanically seeding the upland areas to cool season gasses that make up dense nesting cover.…”

“…While current wet conditions in the U.S. portion of the PPR have likely not been experienced in the last 500 years [30] there is also paleo-limnological evidence that historically semi-permanently ponded wetlands did not typically contain vegetative communities associated with permanent waterbodies for about 8000-10,000 years [93]. This change to more permanent hydrological conditions has also been indicated by changes in diatom assemblages and daphnia ephippia in sediment cores of prairie-pothole wetlands [94] Linking the recently observed increases in depressional ponds and surface-water area to ecosystem homogenization is not necessarily intuitive. However, the ecosystem functions of these wetlands typically have less to do with the amount of water and are more connected to the period of time they pond water and their location on the landscape (spatial organization and hydrogeologic setting), determining many of their physical and biological characteristics.…”

Cascading, interactive, and indirect effects of climate change on aquatic communities, habitats, and ecosystems

“…While it was suggested that observed changes may be connected to the El Niño and the Southern Oscillation climate oscillation, the stochastic nature of the forcing, and changes in seasonal cycles (which were more pronounced in the wet period) further indicate the need for longer‐term datasets. In the northern Great Plains wetlands, a recent increase in production of the potent greenhouse gas methane was inferred from changes in benthic and pelagic communities and their trophic interactions (Hu et al 2023). The identification of the emergence of a new type of wetland habitat by Hu et al (2023) and the hypotheses generated by the repeat observations by Douglas et al (2023) highlight the opportunities continuous studies provide for understanding our biosphere, support discovery of new patterns and processes, and possibly help to develop safer and more powerful mitigation strategies.…”

“…In the northern Great Plains wetlands, a recent increase in production of the potent greenhouse gas methane was inferred from changes in benthic and pelagic communities and their trophic interactions (Hu et al 2023). The identification of the emergence of a new type of wetland habitat by Hu et al (2023) and the hypotheses generated by the repeat observations by Douglas et al (2023) highlight the opportunities continuous studies provide for understanding our biosphere, support discovery of new patterns and processes, and possibly help to develop safer and more powerful mitigation strategies.…”

“…It is a strength of this special issue to be representative of diverse habitats and scales, including alpine streams (Leathers et al 2023), wetlands of the North American Great Plains (Hu et al 2023), lakes (Hébert et al 2023; Katkov and Fussmann 2023; Su et al 2023), estuaries (Douglas et al 2023; Franzè et al 2023), tropical reefs (Lange et al 2023), and the arctic ocean (Ramondenc et al 2023), as well as diverse organisms, from single celled algal primary producers (Vrana et al 2023) to top consumers such as right whales (Meyer‐Gutbrod et al 2023). Moreover, contributions cover ecologically and climate‐relevant ranges of scales, including laboratory experimentation lasting days (Bomfim et al 2023; Carrier‐Bellau et al 2023, Fields et al 2023), mesocosm experiments of 1‐month duration (Katkov & Fussmann 2023; Wang et al 2023), as well as the paleorecord (Hu et al 2023). Despite this diversity of habitats and scales, the contributions to the special issue reflect only a subset of breadth, approaches, and geographic coverage; several gaps in contributions of climate‐oriented aquatic research are apparent.…”