Variability and control of carbon consumption, export, and accumulation in marine communities

Abstract

Elucidating the extent and controls of the routes followed by primary production in marine communities (i.e., consumption by herbivores, decomposition, transportation of plant material beyond the community boundariesreferred to as export-or accumulation as biomass or detritus) is essential to understand how much and why they differ in their capacity to fuel secondary production, both within or out of the community, and in their role as sinks in the oceanic carbon budget. Here, using an extensive compilation of published reports, I compare the magnitude of these routes across and within a wide range of community types, including oceanic and coastal phytoplanktonic communities, benthic microalgal communities, coral reef algal beds, macroalgal beds, seagrass meadows, marshes, and mangroves. Furthermore, I examine whether the variability in the magnitude of these routes among and within types is associated with that in the magnitude of primary production. In general, different community types showed similar levels of consumption by herbivores and export, in spite of substantial within-type variability. On the contrary, substantial differences in detritus decomposition and accumulation were found among types: coral reef algal beds and benthic microalgal communities tended to show the highest and lowest levels of decomposition, respectively, whereas marshes and oceanic phytoplanktonic communities tended to show the largest and smallest levels of detritus accumulation. The results also identify primary production as a robust (i.e., applicable to a wide range of environmental conditions and communities) control of the variability in herbivory and decomposition among marine communities. The role of primary production as a control of export and detritus accumulation is generally minor and only restricted to coastal phytoplanktonic and benthic microalgal communities, for export, and marshes and mangroves for detritus accumulation.

Global patterns of kelp forest change over the past half-century

“…The potential for this decline is considered more likely for species with slow postdisturbance recovery rates [e.g., corals (38)], those species that display little seasonal variability in abundance [e.g., mangroves (39)], or those species experiencing stressors of sufficiently widespread and high magnitude [e.g., fishes (1)]. However, for many taxa, globally coherent signals of change are unlikely when the identity and magnitude of drivers vary widely on local and regional scales (4,17,40), where species and ecotypes within taxonomic groups respond variably to change, or where abiotic and biotic contexts vary widely across geographic locations (41).…”

Seasonal dependence on seagrass detritus and trophic niche partitioning in four copepod eco-morphotypes

“…An important proportion of seagrass and macroalgae productivity is exported as shed biomass, accumulating on the sea bottom to form habitats called 'exported macrophytodetritus accumulations' (hereafter EMAs) (e.g. Vetter, 1995;Hyndes and Lavery, 2005;Lepoint et al, 2006;Boudouresque et al, 2016) and fuelling the detrital pool (Cebrian, 2002). The endemic and highly productive Neptune grass, Posidonia oceanica (L.) Delile, covers from 25 to 45.10 3 km 2 and the meadows it forms represent one of the dominant ecosystems found in the coastal Mediterranean (Pasqualini et al, 1998).…”

Carbon sources supporting benthic mineralization in mangrove and adjacent seagrass sediments (Gazi Bay, Kenya)

“…The current estimates of the fate of seagrass production (compiled e.g. in Duarte and Cebrián, 1996;Cebrián, 2002) are typically based on quantitative process measurements (e.g. communtiy respiration), and since such measurements inherently do not include a characterization of the sources of C fuelling mineralization, they may represent a biased view of the importance of mineralization as a fate of seagrass carbon.…”