Integrating periphyton and surfacewater–groundwatermethods to understand lake ecosystem processes

Abstract

Groundwater-surface water (GW-SW) interactions represent an important, but less visible, linkage in lake ecosystems. Periphyton is most abundant at the GW-SW interface and can rapidly assimilate nutrients from the water column. Despite the importance of periphyton in regulating whole-lake metabolism, they are less well studied or monitored in comparison with planktonic taxa and pelagic systems. This is in stark contrast to studies of flowing waters and wetlands, where variability in GW-SW connectivity and periphyton productivity is more often incorporated into study designs. To bridge the gap between groundwater's influence on lake benthic communities, this synthesis aims to prime researchers with information necessary to incorporate groundwater and periphyton sampling into lake studies and equip investigators with tools that will facilitate crossdisciplinary collaboration. Specifically, we (1) propose how to overcome barriers associated with studying littoral ecological-hydrological dynamics; (2) summarize field, laboratory, and modeling techniques for assessing spatiotemporal periphyton patterns and benthic hydrological fluxes; and (3) identify paths for hydrological techniques to be incorporated into ecological studies, deepening our understanding of whole-lake ecosystem function. We argue that coupling hydrological and periphyton measurements can yield dualistic insights into lake ecosystem functioning: how benthic periphyton modulate constituents within groundwater, and conversely, the extent to which constituents in groundwater modulate the productivity of periphyton assemblages. We assert that priming ecologists and hydrologists alike with a shared understanding of how each discipline studies the nearshore zone presents a tangible path forward for both integrating these disciplines and further contextualizing lake processes within the limnological landscape.

National-scale remotely sensed lake trophic state from 1984 through 2020

“…These patterns indicate that in certain lakes, the models were unable to distinguish the spectral signatures that are potentially attributable to sediment or benthic algae as well as shoreline vegetation and soil. The spectral similarity between shallow oligotrophic and deep eutrophic lakes is relevant to active research trajectories in limnology, particularly those examining the relatively high contributions of benthic algal communities to whole lake productivity in oligotrophic lakes 58,[60][61][62][63][64] . Given the potential for lakebed effects to alter classifications, research questions could consider the influence of depth-related misclassifications.…”

Warming‐induced changes in benthic redox as a potential driver of increasing benthic algal blooms in high‐elevation lakes

“…abundance (Timoshkin et al 2018; Meyer et al 2022). Similarly, Lake Tahoe has experienced increased periphyton biomass likely due to a mix of wastewater‐associated eutrophication, groundwater leachate, and complex physical and hydrological processes (Naranjo et al 2019; Atkins et al 2022). Although observations of increased periphyton blooms in lakes with adjacent human population can draw links between human activity and in‐lake periphyton responses (e.g., Rosenberger et al 2008), these blooms also appear to be increasing in remote, high‐elevation systems that lack permanent human settlements (Oleksy et al 2020).…”

“…We have demonstrated in principle that microbially mediated nutrient release in tandem with the physical constraints of temperature‐dependent oxygen saturation may be a ubiquitous mechanism for driving nearshore benthic algal blooms in clear lakes that are warming, but the data necessary to test this hypothesis are lacking. Limnology has focused on offshore water column dynamics, infrequently including nearshore or benthic measurements, much less those across the varied substrates of littoral zones (Vadeboncoeur et al 2021; Atkins et al 2022). Where data exist, we see that clear mountain lakes can exhibit higher temperatures nearshore, relative to offshore water, but temperature and oxygen measurements that include the sediment and the overlying water column are uncommon.…”