Climate change-induced salinity variation impacts on a stenoecious mangrove species in the Indian Sundarbans

Abstract

The alterations in the salinity profile are an indirect, but potentially sensitive, indicator for detecting changes in precipitation, evaporation, river run-off, glacier retreat, and ice melt. These changes have a high impact on the growth of coastal plant species, such as mangroves. Here, we present estimates of the variability of salinity and the biomass of a stenoecious mangrove species (Heritiera fomes, commonly referred to as Sundari) in the aquatic subsystem of the lower Gangetic delta based on a dataset from 2004 to 2015. We highlight the impact of salinity alteration on the change in aboveground biomass of this endangered species that, due to different salinity profile in the western and central sectors of the lower Gangetic plain, shows an increase only in the former sector, where the salinity is dropping and low growth in the latter, where the salinity is increasing.

Keywords: Aboveground biomass; Climate change; Gangetic plain; Glacier melting; Heritiera fomes; Salinity.

Fig. 1

Study sites in the Indian Sundarbans. The three western stations and the three central stations, all in India, are shown divided by an imaginary red line on the map (coordinates are provided in Table S1)

Fig. 2

Temporal variations of phosphate (P, in μg l⁻¹), nitrate (N, in μg l⁻¹) and temperature (T, in °C) in the central and western sectors of the lower Gangetic delta (annual mean values ± SD bars)

Fig. 3

Temporal variations of surface water salinity and aboveground biomass in the central and western sectors of the lower Gangetic delta (annual mean values in psu ± SD and tonnes ha⁻¹ ± SD, respectively)

Fig. 4

Aboveground biomass values (ordinate) plotted against salinity levels (abscissae) in the western (a) and central (b) sectors of the lower Gangetic delta