Philippines
In the Philippines, Enhalus is one of the most prominent seagrass species in mixed seagrass beds1. In the reef flats off Cape Bolinao, this species is able to colonize various habitat types1: muddy to coarse sandy substratum, turbid to clear waters and splash zones above zero datum to ca. 3m depth. Across this range in environmental conditions, Enhalus shoots differ in morphology, biomass and density1. Flowering occurs year-round, but the intensity varies temporally and correlates with mean water temperature1. Spatially, differences in flowering intensity correlated with available light as affected by turbidity and water depth. Exposure duration of female flowers to air seems to be crucial for pollination and subsequent seed setting, resulting in higher numbers of fruits in shallower sites. Based on reconstruction techniques1 estimated that at Cape Bolinao, Enhalus produces 2.8 flowers per shoot per year on average and allocates up to 20% of its aboveground production to flowering and fruiting. Contrary to most seagrass species, E. acoroides invests substantial resources in reproduction (20% of annual above ground productivity1), and pollination occurs at the water surface. The length of the female peduncle limits successful pollination to low tide depths shallower than ca. 0.5 m. Vegetatively, the species occurs substantially deeper1. Rhizome branching frequency and longevity of shoots and rhizomes give rise to a patchy distribution of clonal fragments, with the gaps filled by other seagrasses, macroalgae or bare sediment. It has been suggested that production of gas bubbles in photosynthesis plays a key role in the release of male flowers, rather than the generally accepted belief that release of male flowers is a result of low spring tidal level. Allocation of biomass and nutrients (N, P) over various plant components suggests that sexual reproduction involves high cost in E. acoroides 1.
Similar to other tropical seagrasses, Enhalus acoroides in Cape Bolinao are limited by the availability of nitrogen1. The extent of nutrient limitation of E. acoroides is high variability both in space and time.
The other prominent seagrass species in Bolinao is Thalassia hemprichii. However, no persistent seed bank has been reported to be the present1. The survival of buried seeds was assessed experimentally since such a capacity is a prerequisite for the formation of seed bank. Rollon et al.1 found a rapid germination of non-dormant seeds and development into seedlings. Such seedlings could not survive under buried conditions (5 and 10 cm) for longer than a week.
One of the most significant threats to seagrasses in SE Asia and the Philippines includes increased siltation from deforestation1. Philippine seagrass species richness and community leaf biomass decline sharply when the silt and clay content of the sediment exceeds 15%1. Syringodium isoetifolium and Cymodocea rotundata are generally only present in multispecific meadows, while Enhalus acoroides is the only species which can remain in heavily silted sediments. The following ranking of species sensitivity to siltation is (from the least to most sensitive): S. isoetifolium → C. rotundata → Thalassia hemprichii → Cymodocea serrulata → Halodule uninervis → Halophila ovalis → Enhalus acoroides. Positive correlations have been found between species richness and both community leaf biomass and the leaf biomass of individual seagrass species. The relationships between percent silt and clay in the sediment and seagrass community leaf biomass and species richness provides useful dose–response relationships which can be used to set allowable or threshold siltation loads in SE Asian coastal waters, and indicate that species loss from seagrass meadows is an early warning of detrimental siltation loads1.
Seagrass meadows in Bolinao and the Philippines are of significant importance to artisanal fisheries. One of the most important fishes includes the rabbitfish. Seagrass landscape patterns have been shown to influence fish abundance in Bolinao, but only in terms of continuity of vegetation 1.
In the Philippines, production ecology of seagrasses1 and seagrass epiphytes1 has been quantified. Thalassia hemprichii accounted for 80-93% of seagrass leaf biomass at Bolinao1. Growth rate of seagrass was 6.6 mm per shoot per day, or 2.3 mg AFDW per shoot per day. Production of seagrass leaves per unit area of seagrass bed varied with location from 870 to 1850 mg AFDW m -2 day -1. Between 20 and 60% of the highly productive periphyton assemblage at Bolinao, is grazed by an epifaunal community dominated by gastropods1. Approximately 24% of annual seagrass production is grazed by urchins, but owing to large changes in urchin population structure and density, grazing impact is expected to vary from < 5% to > 100% at different times of year.
Seagrass-Watch in Philippines
To provide an early warning of change, long-term monitoring has been established in Philippines as part of the Seagrass-Watch, Global Seagrass Observing Network (www.seagrasswatch.org). Establishing a network of monitoring sites in Philippines provides valuable information on temporal trends in the health status of seagrass meadows in the region and provides a tool for decision-makers in adopting protective measures. It encourages local communities to become involved in seagrass management and protection. Working with both scientists and local stakeholders, this approach is designed to draw attention to the many local anthropogenic impacts on seagrass meadows which degrade coastal ecosystems and decrease their yield of natural resources.
Location
Bolinao
Monitoring: Suspended
Location: located at the north-westernmost part of Oriental Mindoro, and at the south-western end of the Isla Verde Passage, about 130 kilometers south of Manila
Site code: BS
Comments: The seagrass meadows of Cape Bolinao form the base of fishery resources for 35 barangays (a Philippine political unit). The seagrass of Bolinao are seriously threatened through the direct and indirect effects of human settlement and coastal development leading to intense pressure and anthropogenic disturbances to the said habitat.
There is real need to take initiatives to protect, conserve and maintain the resources. Seagrass plays a very important role in the community since many of their livelihoods rely heavily on the seagrass meadows. At present, most people in the community understand that the existing resource provides their livelihood. But the importance of linkage of seagrass meadows with the other two major components of the marine ecosystem, mangroves and coral reefs, is not seriously considered.
Location
Palawan
Monitoring: Suspended
Location: Palawan is an island province of the Philippines located 600 km southwest of Manila and is flanked by the South China Sea on the west and the Sulu Sea on the east.
Comments: At least 10 species of seagrass are known from Palawan. Enhalus acroides is to be the most common seagrass occurring in Palawan. Since 1997, staff from the Palawan Council for Sustainable Development have conducted coastal resource assessments to generate information on the general condition of Palawan’s Coastal resources. Seagrasses were surveyed at a number of sites using a transect/quadrat technique. They reported that nearly half of Palawan’s seagrass resources or in a “poor” condition.
Data generated from surveys of coral reefs and seagrasses across Palawan is input to coastal resource management planning, Environmentally Critical Areas Network (ECAN) zoning and environmental monitoring.
Under ECAN zoning, identify potential core zones which may include habitat of rare and endangered marine species, fish sanctuaries (declaring certain areas as fish sanctuaries to enhance sustainable fisheries).
The effects of eutrophication and siltation are insignificant due to the lack of urbanization and scarce coastal population especially in Balabac waters. There are several factors that have contributed to this fortunate condition. First, as Palawan houses 232 endemic species, the province was proclaimed as Fish and Wildlife Sanctuary in 1967.
Because of this proclamation, coastal development activities that lead to excessive earthworks are almost absent in Palawan. Secondly, major crops in Palawan such as corn, cashew and coconut have limited use of fertilizers and agrochemicals. These crops are not a major source of agrochemical pollutants in the marine ecosystem.
Furthermore, these types of crops cultivation cause very little soil erosion and alteration of physical terrestrial environment. Lastly, commercial logging has ceased in Palawan with the cancellation of timber license agreements in 1993. Water pollution may still occur in other parts of Palawan. Small operations of illegal logging activities occur in the mountain range especially in Quezon and Rizal have contributed to siltation along the coastal areas. In addition, nickel mining and processing plant in Rio Tuba and quarry activities in Rizal contribute to coastal pollution and sedimentation.
Dugong were commonly found in Palawan waters before they were excessively hunted. The sightings of dugong herds in Palawan are considered rare nowadays. In 1991, dugong conservation took a leap with the issuance of Department of Environment and Natural Resources of the Philippines (DENR) Administrative Order (AO) No. 55, which made the dugong the first marine mammal protected in Philippine waters. As stipulated in this AO, any person who hunts, kills, wounds, takes away, possesses, transports and/or disposes of a dugong, dead or alive, its meat or any of its by-products shall be punished by imprisonment from 6 months to 4 years or fined Php 500 to 5,000 or both (equivalent to RM 35 to 350).
Community-based management plays an important role for a province like Palawan that is isolated from other parts of the country. In 1993, the Provincial government created community police forces such as “bantay Palawan” and “bantay dagat” to protect Palawan’s marine resources.
Philippines’ legislation supports empowerment of the community through its 1990 Republic Act 7160. The Act devolves authority so that “territorial and political subdivisions of the State shall enjoy genuine and meaningful local autonomy to enable them to attain their fullest development as self reliant communities and make them more effective development partners”.
The extent of the 15 km of Palawan’s coastal water as municipal waters by the 1990 Local Government Code has given a major mandate in the implementation of the community based management. Before success in marine resources management can be achieved, the locals especially in the rural areas need to be educated. The UNESCO Commission on Science and Technology and the Department of Environment and Natural Resources plan to initiate such an education campaign in Palawan.
In the Philippines, it is not only dugong, turtle and fish which eat seagrass. The rhizome of Enhalus acoroides is served as delicacy in some coastal villages. The seeds are eaten by children and recently the starch from seeds has been extracted for baking cookies (hoped to be a viable commercial venture). Another species, Halophila ovalis, is pickled and used as salad vegetable. Importantly, dried seagrass leaves are found to cure diarrhea. Seagrass also has other uses apart from a food source. The handicraft and furniture industries have utilized seagrass blades as a component and accent parts of selected furniture, handicrafts and other saleable household items.
Location
Puerto Galera
Monitoring: Suspended
Location: located at the north-westernmost part of Oriental Mindoro, and at the south-western end of the Isla Verde Passage, about 130 kilometers south of Manila
Site code: PU
Status (July 2007):
- Sites are similar in species composition and abundance. Enhalus acoroides, Cymodocea rotundata, Halodule uninervis, Halophila ovalis and Thalassia hemprichii dominated the approximately 500 m seagrass bed in the area.
- At least three species of sea urchins were found in the meadow.
- Each site has only been sampled once.
- From anecdotal reports, seagrass meadows in the Puerto Galera region are in a fair condition, and no major losses are apparent.
- Insufficient data to describe long-term trends.