Seagrass metabolism and carbon dynamics in a tropical coastal embayment

Abstract

Net ecosystem metabolism and subsequent changes in environmental variables were studied seasonally in the seagrass-dominated Palk Bay, located along the southeast coast of India. The results showed that although the water column was typically net heterotrophic, the ecosystem as a whole displayed autotrophic characteristics. The mean net community production from the seagrass meadows was 99.31 ± 45.13 mM C m d, while the P/R ratio varied between 1.49 and 1.56. Oxygen produced through in situ photosynthesis, exhibited higher dependence over dissolved CO and available light. Apportionment of carbon stores in biomass indicated that nearly three-fourths were available belowground compared to aboveground. However, the sediment horizon accumulated nearly 40 times more carbon than live biomass. The carbon storage capacities of the sediments and seagrass biomass were comparable with the global mean for seagrass meadows. The results of this study highlight the major role of seagrass meadows in modification of seawater chemistry. Though the seagrass meadows of Palk Bay are increasingly subject to human impacts, with coupled regulatory and management efforts focused on improved water quality and habitat conservation, these key coastal ecosystems will continue to be valuable for climate change mitigation, considering their vital role in C dynamics and interactions with the overlying water column.

Seasonal metabolism and carbon export potential of a key coastal habitat: The perennial canopy‐forming macroalga Fucus vesiculosus

“…Community NEM rates of various seafloor habitats worldwide on (A) daily and (B) annual timescales. Daily NEM (a) mean ± SD (large open symbols) and number of observations ( n ) for datasets that compute the daily NEM from continuous diel measurements over 24 h (Maerl beds: Attard et al [], Martin et al [], and Martin et al []; bare sediments: Attard et al [], Attard et al [], Berg et al [], Chipman et al [], Hume et al [], Rheuban et al [], and Walpersdorf et al []; macroalgae: Gruber et al [] and this study; Seagrass: Ganguly et al [], Gruber et al [], Hume et al [], Lee et al [], Long et al [], Moriarty et al [], Olivé et al [], Pollard and Moriarty [], and Rheuban et al []). Annual data (B) are from studies that consider daily and seasonal NEM when computing the annual estimate (Maerl beds: Attard et al [] and Martin et al []; bare sediments: Attard et al [], Chipman et al [], and Rheuban et al []; Seagrass: Rheuban et al []; Macroalgae: this study).…”

Carbon Balance in Salt Marsh and Mangrove Ecosystems: A Global Synthesis

“…Global seagrass area from [195], macroalgae area from [196] and area of other ecosystems from [188], except the global coastal ocean [194], which encompasses estuaries, other wetlands, and continental shelves. Seagrass data [188] updated from [197][198][199][200][201][202][203][204][205][206][207][208][209][210] and macroalgae data from . Plankton GPP and R in salt marshes from [237] and in mangroves from [52].…”

Seagrass and macrophyte mediated CO2 and CH4 dynamics in shallow coastal waters

“…In contrast, limited seasonality was observed for pCO 2 and CO 2 fluxes from the CS waters. In addition to salinity stress, human induced stressors such as increase in turbidity through aquaculture, untreated domestic wastes, boating and fishing activities have led to a deterioration of seagrass health and its capacity to assimilate C [ 30 ].…”

“…In India, seagrass meadows are distributed in various pockets along the east and west coasts, with a total area of ~517 km 2 [ 28 ]. There have been a few studies focused on seagrass productivity [ 29 , 30 ] from Indian coastal waters. This study is the first in determining the air-water fluxes of key GHGs (CO 2 and CH 4 ) from a seagrass meadow in India.…”