Taxonomy of the Gracilariaceae (Rhodophyta) from Western Macajalar Bay, Philippines

Philippine Journal of Science 150 (S1): 165-171, Special Issue on Biodiversity ISSN 0031 - 7683 Date Received: 29 Sep 2020 Taxonomy of the Gracilariaceae (Rhodophyta) from Western Macajalar Bay, Philippines Ma. Czarmayne Victoria Jude T. Escoro1,2, Elaine A. Villaluz2, and Lawrence M. Liao3* 1The Marine Science Institute, University of the Philippines Diliman, Quezon City 1101 Philippines 2Department of Biology, Xavier University–Ateneo de Cagayan Cagayan de Oro City 8400 Philippines 3Graduate School of Integrated Sciences for Life, Hiroshima University Higashi-Hiroshima 739-8528 Japan Species of the marine red algal family Gracilariaceae are distributed in tropical and warm temperate waters of the world where they are harvested for their agar content. In the Philippines, the level of exploitation of these species is low despite their high diversity and potentially large harvestable biomass. A taxonomic survey of the Gracilariaceae was conducted along the western corridor of Macajalar Bay in northern Mindanao for the first time. Six common species were found in three sampling sites. The findings of this study will contribute to the baseline marine biodiversity information, can promote the use of the various species among coastal inhabitants, and provide guidance towards better policy formulation for more effective resource management. Keywords: algae, agarophyte, biodiversity, Gracilariales, Mindanao, seaweed INTRODUCTION is in the food packaging industry where agar-based films are developed to provide renewable, biodegradable, food- In the past several years, species of the marine red algal grade, and edible food packages (Mostafavi and Zaeim family Gracilariaceae have sparked global interest as 2020) that can potentially help address the serious problem a commercially important source of agar. They grow of plastics pollution and waste. in tropical countries, particularly in Southeast Asia where high biomass is obtained from natural stocks The tropical species of the Gracilariaceae have traditionally and aquaculture facilities (Chen et al. 2009). In 2018, been recognized within the loosely defined genus China was the world’s top exporter of agar while Gracilaria with about 150 species until molecular data Japan, the United States, and Russia were among the suggested recognizing them under segregate genera largest importers. The agar biopolymer has traditionally (Gurgel et al. 2018). The first major monographic work found its application in the microbiological (mainly as documenting the diversity of Gracilaria sensu lato in culture media) and food industries (gelatin products the Philippines was published by Trono et al. (1983), and food additives). Species of Gracilaria contain who described and reported eight species. Later, Silva et various chemicals with untapped bioactive and industrial al. (1987) incorporated all previously published records, potentials. But one of its latest and innovative applications resulting in 24 species and two varieties of Gracilaria *Corresponding Author: [email protected] as occurring in the Philippines. The latest summary of Philippine marine algae documented 38 species, two 165 Philippine Journal of Science Escoro et al.: Taxonomy of Macajalar Bay Gracilariaceae Vol. 150 No. S1, Special Issue on Biodiversity varieties, and one form of the Gracilariaceae (Ang et MATERIALS AND METHODS al. 2013). Four new species of the Gracilariaceae have been described based on Philippine samples – namely, Samples were collected from three sites along the Gracilaria salicornia (C. Agardh) E.Y. Dawson and G. intertidal areas of western Macajalar Bay at low tide manilaensis Yamamoto & Trono both from Manila Bay, during the transition of the dry and wet season of the year G. sullivanii Yamamoto & Trono from Batangas, and (September–November 2012). These sites were selected Hydropuntia divergens (B.M. Xia & I.A. Abbott) M.J. as they show high diversity of marine flora as observed Wynne from Sorsogon (originally as Polycavernosa in an earlier assessment (Quiaoit et al. 2010). The three divergens B.M. Xia & I.A. Abbott). sites are briefly described below: Reports on the marine flora of the southern Philippine 1. Barangay Moog, Laguindingan, Misamis Oriental island of Mindanao are few and sporadic, compared to (8°36’6”N, 124°28’19”E) those emanating from the northern and central sections The site is located approximately 1 km from the of the archipelago. The earliest report seems to be that eastern end of the runway of the Laguindingan of Gracilaria dactyloides Sonder by Dickie (1876), who International Airport and the nearest human studied the samples collected by the HMS Challenger settlement is about 1 km. It is characterized by hard Expedition that dropped anchor off Zamboanga. Other substrate and coral rubbles. There were few patches genera and species of the Gracilariaceae have also been of seagrass, while seaweed communities are scarce reported from Mindanao, including undetermined species of throughout the site. Polycavernosa by Yamamoto (1989) and Gracilariopsis by 2. Barangay Tambaling, El Salvador, Misamis Oriental Hurtado-Ponce and Liao (1998) – all from Zamboanga City. (8°34’15”N, 124°30’50”E) The shores of Macajalar Bay in the northern section of It is located about 100 m from the edge of the Mindanao lie within the province of Misamis Oriental Butuan-Cagayan-Iligan highway and adjacent to and are heavily impacted by industrial development and human settlements. The substrate is essentially urbanization (Felisilda et al. 2019). Such impacts are made up of coral rubbles and muddy-sandy bottom. mainly concentrated in the coastlines of the large city of Dense seagrass beds can be found while seaweed Cagayan de Oro and suburban areas situated on the southern individuals are sparsely distributed. Groyne fringes of the Bay. A number of heavy industries have structures are also present in the site, which could been built around Macajalar Bay and most of them very have influenced the water movement resulting in close to the coasts, thereby presenting potential sources of low water clarity during collection. anthropogenic impact on the various marine ecosystems 3. Barangay Poblacion, Opol, Misamis Oriental there – including mangrove forests, seagrass beds, and (8°31’8”N, 124°34’45”E) coral reefs. Very recently, marine pollution in the form The site is adjacent to the Butuan-Cagayan-Iligan of generated microplastics has been recently identified as highway and lined with restaurants and human a major concern (Kalnasa et al. 2019). In addition, algal settlements with their effluents discharged directly blooms caused by a mixture of green macroalgae have been to the shore. The substrate is a mixture of silt, mud, reported in the suburban areas and traceable to unregulated and sand, and progresses to a hard substrate with organic discharges to the sea from human settlements and shallow tide pools. Seagrass beds can be found industrial estates (Villaluz et al. 2016). The western corridor in few patches, while seaweed communities are of Macajalar Bay is expected to see unabated economic common on the seaward portion. Bloom-forming and infrastructural development in the coming years as green algae are also common, leaving little substrate commercial traffic between the Cagayan de Oro metropolis for other biota and even covering some seagrass and and the new international airport in Laguindingan town seaweeds. to its west increases. Terrestrial and marine biota will expectedly be affected by further industrial development In all sites, representative samples of the Gracilariaceae and anthropogenic outputs. Among the marine life there, were collected along ten parallel transect walks per seaweed communities that support fisheries and the marine sampling site, each transect walk 100 m long and 5 m apart food web will likely be impacted, if not already. This study from each other. Samples were placed in plastic bags and accounts for the species of marine red algae belonging taken to the laboratory for photography and preservation, to the economically important Gracilariaceae along this following the method of Hurtado et al. (2006). Samples corridor that is showing increased economic activity and were dried into herbarium specimens, curated, and development. The data may be useful in conserving these deposited in the Xavier University Department of Biology resources towards greater ecosystem stability and proper herbarium. Cross-sections were made by freehand management and exploitation. sectioning using a double-edged razor blade, rehydrated and stained with aniline blue-phenol solution, mounted 166 Philippine Journal of Science Escoro et al.: Taxonomy of Macajalar Bay Gracilariaceae Vol. 150 No. S1, Special Issue on Biodiversity in glycerine medium on a clean microscope glass slide, locality: Makassar, Indonesia) due to their dense and and topped with a coverslip, which is then sealed on all corymbose habit with frequent upcurved distal portions sides by colorless nail polish. Sections were examined (Trono 2004), different morphologically from the type under a compound microscope, cellular features were variety from the Red Sea with arcuate thalli and secund measured using a stage micrometer, and photomicrographs branching. This variety is also the most frequently reported taken with a digital camera mounted on the microscope. form throughout Southeast Asia. Samples were identified using pictorial field guides and taxonomic references. An emphasis is made to use and cite Gracilaria canaliculata Sonder taxonomic

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