Abstract
Abstract. Seagrass meadow metabolism has been measured for decades to gain insight into ecosystem energy, biomass production, food web dynamics, and, more recently, to inform its potential in ameliorating ocean acidification (OA). This extensive body of literature can be used to infer trends and drivers of seagrass meadow metabolism. Here, we synthesize the results from 56 studies reporting in situ rates of seagrass gross primary productivity, respiration, and/or net community productivity to highlight spatial and temporal variability in oxygen (O2) fluxes. We illustrate that daytime net community production (NCP) is positive overall and similar across seasons and geographies. Full-day NCP rates, which illustrate the potential cumulative effect of seagrass beds on seawater biogeochemistry integrated over day and night, were also positive overall but were higher in summer months in both tropical and temperate ecosystems. Although our analyses suggest seagrass meadows are generally autotrophic, the effects on seawater oxygen are relatively small in magnitude. We also find positive correlations between gross primary production and temperature, although this effect may vary between temperate and tropical geographies and may change under future climate scenarios if seagrasses approach thermal tolerance thresholds. In addition, we illustrate that periods when full-day NCP is highest could be associated with lower nighttime O2 and increased diurnal variability in seawater O2. These results can serve as first-order estimates of when and where OA amelioration by seagrasses may be likely. However, improved understanding of variations in NCPDIC:NCPO2 ratios and increased work directly measuring metabolically driven alterations in seawater pH will further inform the potential for seagrass meadows to serve in this context.
Highlights
Seagrasses are productive marine macrophytes, lauded for numerous ecosystem functions including habitat formation for diverse species assemblages, stabilization of marine sediments, storm surge buffering, and many others
In recognition of the substantial temporal diel variability in O2 fluxes associated with daytime net community production (NCP) and nighttime respiration, as well as the uncertainty in our understanding of how this temporal variability translates to pH variability and is integrated by vulnerable marine organisms associated with seagrass beds, we focus on both hourly rates of NCP taken during peak daylight hours and full-day NCP
We identified 56 published papers that reported in situ rates of seagrass community metabolism (Table S1 in the Supplement)
Summary
Seagrasses are productive marine macrophytes, lauded for numerous ecosystem functions including habitat formation for diverse species assemblages, stabilization of marine sediments, storm surge buffering, and many others. Seagrass meadow productivity has been studied for decades, with community metabolism work published as early as 1956 (Odum, 1956). Foundational work assessed the role of seagrass community metabolism in local food web dynamics and ecosystem energy exchanges (e.g., Odum and Hoskin, 1958; Murray and Wetzel, 1987). Seagrass metabolism has been highlighted for its potential role in reducing aqueous CO2 concentrations, thereby locally mitigating ocean acidification (OA) (e.g., Hendriks et al, 2014; Ricart et al, 2021) – an ecosystem function that has led to renewed interest in metabolism research.
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