Population‐specific resilience of Halophila ovalis seagrass habitat to unseasonal rainfall, an extreme climate event in estuaries

Abstract

1. Extreme climate events are predicted to alter estuarine salinity gradients exposing habitat-forming species to more frequent salinity variations. The intensity and duramost estuarine biota will be resistant to some fluctuations in salinity via phenotypic plasticity in salinity tolerance, so the ecosystem resilience will depend upon the ability to resist and/or recover from the disturbance. This in turn is dependent upon the characteristics of the disturbance such as the direction, intensity, magnitude of change and the duration of exposure (Kültz, 2015;Lee & Petersen, 2003). Scientists are using frameworks to define ECEs such as marine heatwaves (Hobday et al., 2016), and to understand accurate predictions about ecological responses to climate change and identifies which populations may 'future proof' ecosystem resilience. 6. Synthesis. Following an extreme rainfall event, we found seagrass populations that are exposed to variable salinities recovered while those from a stable salinity environment were unable to recover within the study time frame. These findings expand upon existing evidence, derived primarily from other ecosystems, that show new sources of resilience may be uncovered by accounting for between-population variation.

Reconciling resilience across ecological systems, species and subdisciplines

“…Hoover et al (2021) demonstrate that the long-term effects of seasonal droughts on soil moisture can impact the resistance and recovery of plant biomass and phenology in Colorado, USA. Webster et al (2021) show how following extreme rainfall events the resistance to changes in biomass and leaf density of seagrass populations, and the recovery to pre-disturbance historical values, depends on the salinity levels to which these have been exposed previously. Leverkus et al (2020) use a meta-analysis approach to highlight how local environmental factors also play a key role in the resilience of trees to logging.…”

“…Webster et al. (2021) show how following extreme rainfall events the resistance to changes in biomass and leaf density of seagrass populations, and the recovery to pre‐disturbance historical values, depends on the salinity levels to which these have been exposed previously. Leverkus et al.…”

Seagrass Meadows under the Changing Climate: A Review of the Impacts of Climate Stressors

“…It could change estuarine salinity gradients, hence the ecosystem therein. In southwestern Australia, a gush of freshwater into an estuary during an extreme rainfall event in 2017 altered the biomass of Halophila ovalis [42] . In estuarine areas with variable salinity, the seagrass communities demonstrated more plastic salinity tolerance and their reduced biomass recovered within 9 to 11 months.…”

“…In estuarine areas with variable salinity, the seagrass communities demonstrated more plastic salinity tolerance and their reduced biomass recovered within 9 to 11 months. In areas with more constant salinity, the ensuing loss of biomass was more significant and the recovery took more than 22 months [42] . The responses of seagrasses to variations in salinity are often population-specific.…”

“…In addition, the impacts of climate change on seagrasses are often species and population specific and it may involve voluminous studies to understand how different species and communities of seagrass respond to various climate stressors [42] . Climate stressors frequently work together instead of separately to affect seagrass meadows.…”