Consumer regulation of the carbon cycle in coastal wetland ecosystems

Abstract

Despite escalating anthropogenic alteration of food webs, how the carbon cycle in ecosystems is regulated by food web processes remains poorly understood. We quantitatively synthesize the effects of consumers (herbivores, omnivores and carnivores) on the carbon cycle of coastal wetland ecosystems, ‘blue carbon’ ecosystems that store the greatest amount of carbon per unit area among all ecosystems. Our results reveal that consumers strongly affect many processes of the carbon cycle. Herbivores, for example, generally reduce carbon absorption and carbon stocks (e.g. aboveground plant carbon by 53% and aboveground net primary production by 23%) but may promote some carbon emission processes (e.g. litter decomposition by 32%). The average strengths of these effects are comparable with, or even times higher than, changes driven by temperature, precipitation, nitrogen input, CO 2 concentration, and plant invasions. Furthermore, consumer effects appear to be stronger on aboveground than belowground carbon processes and vary markedly with trophic level, body size, thermal regulation strategy and feeding type. Despite important knowledge gaps, our results highlight the powerful impacts of consumers on the carbon cycle and call for the incorporation of consumer control into Earth system models that predict anthropogenic climate change and into management strategies of Earth's carbon stocks. This article is part of the theme issue ‘Integrative research perspectives on marine conservation’.

Integrative research perspectives on marine conservation

“…They predict higher dominance of species with feeding larvae and shorter developmental pelagic phases, especially in tropical regions. He et al [57] then use a meta-analysis of 125 studies in coastal wetlands to show how much ecosystem functioning (as carbon cycling) depends on the biotic composition of the consumer guild. They find that the absence or presence of consumer guilds altered the carbon cycle by e.g.…”

Biota‐mediated carbon cycling—A synthesis of biotic‐interaction controls on blue carbon

“…Meta‐analysis synthesising these effects has been provided for seagrasses (Hughes et al, 2004; Poore et al, 2012; Verges et al, 2018) as well as coastal wetlands (i.e. across salt marshes and mangroves) (He et al, 2020; He & Silliman, 2016). In marshes and mangroves, the effects of herbivory are usually found to be weaker below‐ than aboveground, owing, at least in part, to the scarcity of belowground data, but also to allocation shifts from above‐ to belowground production under herbivory (Davidson et al, 2017; He et al, 2020).…”

“…across salt marshes and mangroves) (He et al, 2020; He & Silliman, 2016). In marshes and mangroves, the effects of herbivory are usually found to be weaker below‐ than aboveground, owing, at least in part, to the scarcity of belowground data, but also to allocation shifts from above‐ to belowground production under herbivory (Davidson et al, 2017; He et al, 2020). In seagrass beds, the effects of herbivores on ecosystem production are complex, because here herbivores consume both seagrass tissue and algal autotrophs attached to or associated with seagrasses, for example as epiphytes.…”

“…BCEs belong to the coastal zone, representing the transition between terrestrial and marine environments with pronounced temporal and spatial heterogeneity in salinity, hydrology and oxygen availability (Odum, 1988). The resulting diverse range of habitats supports a high diversity of biota (Duarte et al, 2020; McCauley et al, 2015) and a complex network of biotic interactions ranging from mutualistic plant–microbe interactions at the micro‐environmental scale of the rhizosphere (van der Heide et al, 2012; Martin et al, 2020; Welsh, 2000) to competitive plant–plant interactions and complex consumer–resource interactions at ecosystem and landscape scales (Atwood et al, 2015; Bertness & Ellison, 1987; He et al, 2020).…”

Chelate-assisted phytoextraction using Brassicaceae plants

“…The use of 5mM EDTA upgrades the uptake of heavy metal [40][41][42]. It has been reported that EDTA enhances the availability of heavy metal to plants and thus increases the accumulation in their shoots [43][44][45].…”