Interlinking association between Red-clawed Crab, Perisesarma bidens (De Hann, 1835) and Grey Mangrove, Avicennia marina (Forskk.) Vierh. in Nakti Creek (Gulf of Kachchh), Gujarat, Western India

Mangroves are the most productive and biologically important ecosystems of the world, as they provide ecological balance, goods, and services to humans; plays a vital role in nature by nurturing ecological, protection and social services. The main purpose of this study was to establish an interlinking association among mangrove litter, crabs and sediment nutrients to derive inter-dependent effects. For this, Nakti Creek (Gulf of Kachchh), Gujarat, Western India, was selected for a study period of 6 months (January to June, 2014), as it harbors substantial population of Red-Clawed Crab, Perisesarma bidens (PB) and Avicennia marina (AM). The area reflects spatio-temporal heterogeneity of mangrove domains e.g. Dense (DMN), Peripheral (PMN), Sparse (SMN), Scanty (SCMN) and Non-Mangrove (NMN). Before commencement of the study, it was hypothesized that PB enhance the growth of mangrove trees, which was well-substantiated at the end of this study. DMN was highly enriched with pH, Total S, Total N, TOC, TOM and K, compared to other domains, PMN with Salinity, SCMN with Total P, and NMN with Salinity, Ca & Mg. Correlation Coefficient Matrix (r) revealed the strong positive correlation between pH & TOM, Salinity & Ca, Ca & Mg, Mg & Total P, Total S & Total N, Total N & Total P with TOM, and TOC & TOM with K. Tree height was flourished in SMN, SCMN & NMN, GBH in NMN, No. of fallen leaves in SCMN, No. of leaves in crab burrows in PMN, Mean length of leaves in SMN & SCMN, Mena width of leaves in DMN & PMN, and Wet weight of leaves in SCMN. Tree height & K exhibited highest correlation with Mean length of leaves, GBH with No. of fallen leaves, No. of fallen leaves with Wet weight of leaves, No. of leaves in burrows with Mean width of leaves, and Mean length of leaves with Wet weight of leaves. Except Salinity, all parameters exhibited highest correlation with Mean width of leaves. Salinity was strongly correlated with No. of leaves in burrows. PMN harbored maximum no. of crab burrows, and SMN with no. of crabs outside burrows. Number of crab burrows was highly correlated with Total P & Mean width of leaves, and No. of crabs outside burrows with TOC & TOM. The present study would have better perception about interaction between abiotic and biotic factors for efficient management and restoration of dwindling mangrove ecosystem. The authors conclude that the presence of Sesarmid Crabs in mangrove forest is vital for enriching the soil with nutrients by enhancing nutrient cycling by feeding on mangrove plant derivatives and making burrows that make the gas exchanges more easier between soil and atmosphere, and hence, it helps in maintaining the growth of mangroves. As a stepping-stone, more elaborative study on effects of PM on AM and vice-versa, is advised for combating ecological degradation of mangrove ecosystem in future.