Preliminary Study on Biogeography and Diversity of Red Alga Halymenia in Manila Bay, Philippines

Halymenia, a red seaweed is widely distributed all throughout the world. It has wide economic importance; however, its species diversity, abundance, and distribution have been rarely studied. In Philippines, the literature on red alga Halymenia is poorly documented. In this light, this study aimed to investigate the species diversity, abundance, and distribution of Halymenia in Manila Bay. Specifically, it identified and characterized the Halymenia species present in the bay, described its distribution and abundance, determined its density, relative density, frequency, and relative frequency, and determined its species diversity by employing several diversity indices. The line transect method was used to identify and quantify the seaweeds observed in five established stations divided into five quadrates. Purposive and systematic samplings were employed as sampling techniques. The keys suggested by Trono Jr. (1997) and De Smedt et al. (2001) were used to identify and characterize the species observed. Using the scale recommended by Odum (1955), the abundance of species was determined. Density, relative density, frequency, and relative frequency of the species were determined using the appropriate formulae suggested by Baleta and Nalleb (2016). Simpson’s index of diversity (1-D) was used in order to determine its species diversity. The study was able to identify four species of Halymenia such as H. dilatata, H. maculata, H. durvillaei, and H. formosa. The most abundant species was H. formosa while the least abundant was H. maculata. These seaweed species were exclusively found in Brgy. Bucana, Ternate, Cavite. Its absence in other stations made its abundance, density, relative density, frequency, relative frequency and species diversity very low during the study period. Findings of the study recommended that sampling should be done in a monthly basis all year round in order to better account its distribution in the bay. Its life cycle should be studied in order to understand better its seasonality in distribution and abundance.

Keyterms: Abundance; distribution; diversity, Halymenia; Manila Bay.