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The Saudi Arabian Gulf coast is witnessing many industrial, recreational and other developmental activities. Impact of these activities on the intertidal macrofaunal communities of this region has not been documented well. Thirty four stations falling under four zones along this coast were sampled to study the benthic macrofaunal community. A total of 81 taxa were recorded and the species richness varied between the zones. Among the 48 polychaetespecies found, Exogone heterosetosa, Dialychone collaris, Ophelina longicaudata, Paraprionospio pinnata, Perinereis falsovariegata and Scololepis squamata were dominant. Species such as Littoraria scabra, Bullia vittata, Incatella cingulata, Meretrix meretrix, Donax sp. and Maoricardium setosum were dominant among the twelve gastropod species. The thirteen species of macrofauna identified to occur in all the zones comprised eight species of gastropods besides two species each of amphipods and isopods and one species of cumacean. ANOSIM showed significant differences in assemblage overall among the four zones and in pairwise comparison. Distance based linear modeling (DISTLM) showed the environmental parameters to explain 55.67% of the variability in macrofauna with variables such as pH, salinity, temperature, pebble and gravel showing significant relationship with macrofauna and explained higher variability. The alpha diversity values were comparatively lower in zone 3 which had high anthropogenic pressure. Shannon–Wiener​ diversity, Margalef richness and more importantly the M-AMBI showed the healthy nature of the study area. The findings of the present study are helpful in tracing the future changes in the intertidal habitat due to anthropogenic activities in this fast developing geographical area.

The snail, Littoraria scabra , is a dominant grazer on tropical mangrove trees, and may play an important role in the food web dynamics of these ecosystems. Its daily vertical migration to avoid tidal submersion results in exposure to varying food types and abundances. A comprehensive diet analysis – gut contents, fatty acid profiles, and stable isotopes ( δ 15 N and δ 13 C) – was conducted on snails migrating along mangrove trees and snails maintained in non-tidal mesocosms at Nananu-i-ra, Fiji Islands. In addition, fatty acid profiles and stable isotope signatures were obtained from surface scrapings of mangrove roots, trunks, branches, and leaves. Results from this multi-technique study indicate that L. scabra is mainly a generalist herbivore, which easily shifts diets depending on food availability, and which also has the ability to ingest and assimilate zooplankton. Ingestion of greater quantities of diverse foods (i.e., microalgae, foliose/corticated macrophytes, filamentous algae, mangrove tissues, zooplankton) takes place in the bottom areas of mangrove trees (roots and trunks) during low tides, while top areas (branches and leaves) provide limited food resources for snails feeding during high tides. However, snails preferentially assimilate microalgae and bacteria, regardless of their feeding habitat (different areas within mangrove trees and non-tidal mesocosms). The daily vertical movements of this snail result in variable feeding times, ingestion of different food types and amounts, and different assimilations. These findings also suggest that organic matter derived from mangrove tissues may not be readily transferred to higher trophic levels through this grazing pathway.

The distribution of mobile species such as grazing snails may be influenced by migration patterns, which often are excluded from ecological studies. To highlight this point, the migration patterns of Littoraria scabra on mangrove trees were investigated during incoming and outgoing tides at Nanaru-i-ra, Fiji Islands. Marked snails were used to track the position of snails, relative to the ground, during advancing and receding tides. Snails were found to move quickly upward during incoming tides, potentially to avoid immersion. During the outgoing tide, snails migrated downward, but at a slower pace than upward movement, presumably as a consequence of active feeding on the newly replenished micro-organisms on the mangrove structures (i.e., stems and roots). Aggregation behavior during migration was also recorded by measuring the distance of marked snails to two nearest neighbors. Affinity to neighboring snails was found to be maintained throughout tidal cycles, although greater affinity was observed during...

Mangroves function as important shelter and feeding habitats for marine fauna, but the degree to which mangrove-derived carbon contributes to local food webs has long been debated. In this study, stable isotope analysis was used as a technique to elucidate the role of mangrove carbon in the diets of the macroinvertebrate and fish fauna of an intertidal fringing mangrove forest and adjacent intertidal/subtidal mudflats in a macrotidal Tanzanian estuary. The expectation was that sessile species and those with low motility depend to a larger extent on local carbon sources than highly motile species. A clear distinction in δ13C was present between primary producers from mangrove and mudflat habitats. Macroinvertebrates revealed a gradient in their δ13C where Sesarma crabs were the only species that directly utilised mangrove carbon by feeding on mangrove leaves/detritus. Uca crabs and the gastropod Littoraria scabra showed a higher dependence on microphytobenthos from the mangrove substratum. Among the fish fauna, the amphibious mudskipper was the only species to which the mangroves were accessible during low tide. Consequently this was the only fish species for which it was clear that it fed in the mangrove habitat, most commonly on mangrove-associated Uca crabs. All other species of sessile as well as motile macroinvertebrates and fish from the mangrove and mudflat habitat showed a high degree of utilisation of mudflat carbon. Overall, mangrove carbon thus contributed little to the mangrove and mudflat food webs, despite the high tidal amplitude and the resulting potential for exchange of carbon and fauna in the estuary studied here. Utilisation of mangrove carbon appears to depend more on the ecology of the species in consideration (e.g., species-specific use of zones within the mangrove habitat) than on their potential motility or tolerance to exposure during low tide.