Ecological resilience in tropical Andean lakes: A paleolimnological perspective

Abstract

Little is known about whether changes in lake ecosystem structure over the past 150 years are unprecedented when considering longer timescales. Similarly, research linking environmental stressors to lake ecological resilience has traditionally focused on a few sentinel sites, hindering the study of spatially synchronous changes across large areas. Here, we studied signatures of paleolimnological resilience by tracking change in diatom community composition over the last 2000 years in four Ecuadorian Andean lakes with contrasting ecoregions. We focused on climate and anthropogenic change, and the type of biological responses that these changes induced: gradual, elastic, or threshold. We combined multivariate ordination techniques with nonlinear time‐series methods (hierarchical generalized additive models) to characterize trajectories of community responses in each lake, and coherence in such trajectories across lakes. We hypothesized that remote, high‐elevation lakes would exhibit synchronous trends due to their shared climatic constraints, whereas lower elevation lakes would show less synchronous trends as a consequence of human density and land‐cover alteration. We found that gradual and elastic responses dominated. Threshold‐type responses, or regime shifts, were only detected in the less remote lake, after a long period of gradual and elastic changes. Unexpected synchrony was observed in diatom assemblages from geographically distant and human‐impacted lakes, whereas lakes under similar broad‐scale environmental factors (climate and ecoregion) showed asynchronous community trajectories over time. Our results reveal a complex ecological history and indicate that Andean lakes in Ecuador can gradually adapt and recover from a myriad of disturbances, exhibiting resilience over century to millennial timescales.

Nonlinear dynamics, resilience, and regime shifts in aquatic communities and ecosystems: an overview

“…Tadpole grazing effects were not completely replaceable by compensatory responses from insects, and shifts in grazing effects were not uniform across habitats. This study also points to a topic considered in several other papers about changes in biodiversity and its consequences (e.g., Benito et al 2022; Li et al 2022; Rii et al 2022). Resilience is often tied to biodiversity, and the rapid loss of species from aquatic systems, particularly lakes and rivers, suggests widespread loss of resilience.…”

“…In this volume, long‐term studies of larger and deeper lakes reveal regimes of water clarity and phytoplankton related to food web shifts in a north temperate lake (Trout Lake, Wisconsin, USA) (Martin et al 2022) and to climate‐driven changes in the inputs of colored dissolved organic carbon in a subtropical lake (Lake Annie, Florida, USA) (Sullivan et al 2022). Collectively these studies of regime shifts, as well as others presented in this volume (e.g., Benito et al 2022), indicate that ecosystems under the influence of changing internal and external forces can move quickly to a different and long‐lasting state, affecting ecosystem services. The studies expand our understanding of the causes of resilience, the places where regime shifts occur, and highlight the value of long‐term data.…”

“…The future of aquatic ecosystems is contingent on past and present conditions, which makes empirical analysis challenging due to the short‐term nature of most research programs. Several contributions consider historical attributes using paleo‐analyses to characterize changes in communities of diatoms in Ecuadorian lakes (Benito et al 2022), and chironomids in both Chinese (Zheng et al 2022) and Alaskan (Mayfield et al 2022) lakes. While chironomid shifts show the strong impact of human disturbances, diatom communities demonstrate remarkable resilience over the past two centuries.…”

Anthropogenic activities in the páramo trigger ecological shifts in Tropical Andean lakes

“…In the absence of long-term observational and monitoring data from the CNP, sediments from these lakes have been used as natural archives to gain insights into aquatic ecological shifts since the Industrial Revolution (Michelutti et al, 2015;Benito et al, 2022). Fossil diatom assemblages obtained from these lacustrine sediments have revealed abrupt replacements of species in the past ∼50 yr. Based on the assumption that the lakes are pristine and isolated from direct human activities in their catchments, it was suggested that rising temperatures and longer periods of thermal stratification in the lakes are the main mechanisms behind elevated abundances of certain diatom taxa (Michelutti et al, 2015(Michelutti et al, , 2016.…”

Exploring the Physiological Multiplicity of Native Microalgae from the Ecuadorian Highland, Italian Lowland and Indoor Locations in Response to UV-B

“…However, less is known about the detailed defense mechanisms involved in the UV-B response in microalgae, especially in those native strains adapted to extreme and unexplored ecosystems. For instance, the high Andean lakes are a still unexplored source of photosynthetic microorganisms that are well adapted to extreme environmental conditions characteristic of the equatorial zone, such as altitude, high UV radiation, constant temperatures, and constant photoperiods [ 20 ]. Therefore, the aim of the present study was to investigate the differential effects of UV-B on the inhibition or activation of protective mechanisms in native microalgae from highland, lowland, and indoor conditions under an eco-physiological context.…”