Survival, Growth, and Productivity of Rhizophora racemosa Transplanted in Natural Ecosystems: Implications for Mangrove Restoration

Abstract

Mangroves are coastal wetland ecosystems of tropical and subtropical regions. Their development and trajectories are mainly driven by water and substrate salinities. Therefore, understanding how main mangrove species respond to salinity gradient when transplanted in natural environment is essential for their restoration. This study assessed the survival, growth, and productivity of Rhizophora racemosa seedlings in response to gradient of salinity. Seedlings were grown in nursery under low (3-5 psu) and medium (15-17 psu) water salinities for thirty days and transplanted to three mangrove sites with various salinities (4.6, 11.41, and 18.27 psu). Seedling survival and growth were monitored monthly for 6 months. At the end of month 6, total biomass was harvested and partitioned. Results showed that growth, survival, and productivity of R. racemosa were mainly in uenced not by the salinity under which the propagules were raised in nursery but rather by site. Survival was higher (88.33%) at the site with the highest salinity. Total plant biomass was similar across sites, but root biomass and root weight ratio were higher on sites with higher salinity. Biomass was disproportionately higher in stems (45-54%) than in roots (28-37%), and leaves (15-18%). We suggest that restoration is done in appropriate period, ideally one month before the start of rainy season not only to allow seedlings to well establish their rooting system in the substrate before rains start but also to favour seedling growth, because of substrate salinity dilution by fresh water from rains and ows from uplands.

Recruitment and mortality of Rhizophora mangle L. seedlings in the Tropical Southwestern Atlantic mangrove

“…Those variables were also evaluated in studies with other mangrove species in controlled conditions (mesocosm experiments) (Balke et al, 2013;Gillis et al, 2019;Silva and Maia, 2019;van Hespen et al, 2022) and in field situations (Ewel and Baldwin, 2022;Sinsin et al, 2022;Sloey et al, 2022). Despite these studies, there are gaps in knowledge about the relationship between recruitment dynamics and seedling mortality.…”