Abstract
The diversity and abundance of bivalves and gastropods were studied from April to July 2015. Two sampling stations, Tinib and Esteves, in Casiguran, Aurora were selected based on the presence of mangrove forest, bivalves, gastropods, muddy substrate, and gleaners for the establishment of a transect line. Each station was laid with 100 meters transect line overlaid continuously with 2 m × 2 m quadrat along each transect. A total of 50 sampling units covering 0.02 ha area per sampling station were surveyed. The transect line recorded six species of bivalves distributed among five families and 12 species of gastropods belonging to eight families. Three species of bivalves and five species of gastropods were common to both sampling stations. However, Tinib station had most diverse species of bivalves (0.55) while Esteves station had most diverse species of gastropods (0.43). Both stations revealed Dendrostrea folium (43%) (bivalve) and Cerithidea cingulata (93%) (gastropods) as most frequently occurring species. Dendostrea folium also emerged as the densest (10,640 ind∙ha−1 and 6850 ind∙ha−1) and most abundant (58.52% and 77.84%) bivalve species. For gastropods, Terebralia sulcata (249,250 ind∙ha−1) was the densest and most abundant (96.97%) in Tinib while Terebralia palustris was the densest (747,050 ind∙ha−1) and most abundant (70.44%) in Esteves. Pooled results for bivalve species maintained Dendrostrea folium as the densest (8750 ind∙ha−1) and most abundant (64.81%). However, for gastropods, Terebralia palustris emerged as the densest (373,525 ind∙ha−1) and most abundant (56.70%) species. The mangrove forests of Casiguran, Aurora thus contain a variety of bivalves and gastropods with Tinib station dominated by bivalves while Esteves station dominated by gastropods.
Highlights
Mangrove forest is composed of salt-tolerant trees and shrubs living in coastal intertidal zone
The transect line recorded six species of bivalves distributed among five families and 12 species of gastropods belonging to eight families
A total of 6 bivalves and 12 gastropods were found during a random shell collection within the mangrove forest (Table 1)
Summary
Mangrove forest is composed of salt-tolerant trees and shrubs living in coastal intertidal zone. Its root systems are shallow and partly exposed to the air allowing them to breathe, as these are flooded, during high tide. The two dominant classes of mollusks present in a mangrove forest are Bivalves and gastropods. These organisms are living in the mangrove forest at surface substrate, in substrate, and sticking on roots, stems, and mangrove leaves. These take shelter on mangrove roots during high tide and feed on leaf litters making them an important link in the transfer of organic matter from mangroves to the third trophic level such as fish and birds [1]
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