Variation in Seagrass Carbon Stocks Between Tropical Estuarine and Marine Mangrove-Fringed Creeks

Abstract

Seagrass and associated blue carbon ecosystems are important carbon sinks, and hence understanding their spatial and temporal variability is vital in appreciating their potential roles in climate change mitigation and adaptation. The Indo-Pacific region has the highest seagrass biodiversity, yet little focus has been made to compare seagrass habitat extent and carbon dynamics with their temperate counterparts. The present study assessed habitat characteristics and seagrass species distribution, diversity, and carbon storage in Eastern (marine) and Western (estuarine) mangrove-fringed creeks of Gazi Bay, Kenya. Data on species composition, canopy cover, biomass, and sediment organic carbon were collected in 80 plots of 0.25 × 0.25 m laid along transects established perpendicular to the waterline. Five species formation, viz., Thalassia hemprichii, Cymodocea rotundata, Cymodocea serrulata, Enhalus acoroides, and Thalassidendron ciliatum, were encountered as either single or mixed stands. There was a significant difference in total seagrass biomass between creeks (p < 0.01), with the Eastern creek recording a mean of 10.2 ± 0.6 Mg C ha −1 while the Western creek recording 4.3 ± 0.3 Mg C ha −1. In addition, sediment carbon to 1-m depth varied significantly (p < 0.01) between species in the two creeks and ranged from 98 to 302 Mg C ha −1 , with the Eastern and Western creeks recording means of 258 ± 90 and 107 ± 21 Mg C ha −1 , respectively. The total carbon stock from 50 ha of seagrasses in the Eastern creek was 13,420 Mg C, whereas in the 70 ha of the Western creek it was 7,769 Mg C. The study shows that seagrass community attributes such as species composition and productivity can vary dramatically over a small spatial extent due to differences in biophysical conditions and caution estimations of site-specific carbon stocks using generalized global values.

Dynamics and fate of blue carbon in a mangrove–seagrass seascape: influence of landscape configuration and land-use change

“…Ea, Cym/Th and Tc) constituted the focal habitats of this study due to their wide distribution (Gullström et al 2002) and high potential as carbon sinks in the western Indian Ocean region (e.g. Githaiga et al 2017;Gullström et al 2018;Juma et al 2020). The bay also contained vast scattered sandy areas with low densities of intermixed small-sized seagrasses belonging to the Fig.…”

Ecological connectivity of seagrasses with mangroves increases the carbon storage of tropical seagrass meadows of an island ecosystem

“…Ecological connectivity between seagrass and mangroves is a multifaceted process and plays an important role in the ecological functioning of coastal ecosystems (Berkström et al 2020;Mishra and Apte 2020;Carlson et al 2021). This connectivity between seagrass and mangrove ecosystems positively influences the carbon storage capacity in the seagrass ecosystems (Juma et al 2020;Asplund et al 2021). The present study quantified the carbon storage in ecologically connected seagrass and mangrove ecosystems in a tropical island (ANI) ecosystem and observed that seagrass meadows adjacent to mangrove ecosystems store a higher amount of carbon in their sediment and biomass compared to seagrass ecosystems without mangroves.…”

Blue carbon storage in Fijian seagrass meadows: First insights into carbon, nitrogen and phosphorus content from a tropical southwest Pacific Island

“…To determine the amount of carbon in the two seagrass meadows, the carbon stocks for each species was summed up for each site and the sum multiplied by the sampling area (Juma et al, 2020). The variabilities and errors associated with the measurements were determined by calculating the standard error for each species at each site and multiplying by the area of the sampling site (Juma et al, 2020).…”

“…Seagrass meadows consist of different species that vary in size, form, growth and turnover rates, and may be persistent or transitory (Kilminster et al, 2015). As a result, carbon sequestration in seagrass meadows vary in different regions (Lavery et al, 2013;Serrano et al, 2018) and within meadow landscapes themselves (Gullström et al, 2018;Ricart et al, 2017;Juma et al, 2020).…”