Siti Maryam Yaakub

Chronic light reduction reduces overall resilience to additional shading stress in the seagrass Halophila ovalis

Seagrasses have substantial capacity to survive long periods of light reduction, but how acclimation to chronic low light environments may influence their ability to cope with additional stress is poorly understood. This study examines the effect of temporal light reduction by adding two levels of shading to Halophila ovalis plants in two meadows with different light histories, one characterized by a low light (turbid) environment and the other by a relatively high light (clear) environment. Additional shading resulted in complete mortality for both shading treatments at the turbid site while the clear site showed a pattern of decreased shoot density and increased photochemical efficiency (Fv/Fm) with increased shading. These contrasting results for the same species in two different locations indicate that acclimation to chronic low light regimes can affect seagrass resilience and highlights the importance of light history in determining the outcome of exposure to further (short-term) stress.

Courage under fire: Seagrass persistence adjacent to a highly urbanised city-state

Due to increasing development Southeast Asias coastlines are undergoing massive changes, but the associated impacts on marine habitats are poorly known. Singapore, a densely populated island city-state, is a quintessential example of coastal modification that has resulted in the (hitherto undocumented) loss of seagrass. We reconstructed the historic extent and diversity of local seagrass meadows through herbarium records and backwards extrapolation from contemporary seagrass locations. We also determined the current status of seagrass meadows using long-term monitoring data and identified the main threats to their presence in Singapore. Results show that, even though ∼45% of seagrass has been lost during the last five decades, species diversity remains stable. The main cause of seagrass loss was, and continues to be, land reclamation. We conclude that strict controls on terrestrial runoff and pollution have made it possible for seagrass to persist adjacent to this highly urbanised city-state.

Regional Comparison of the Ecosystem Services from Seagrass Beds in Asia

Coastal ecosystems offer valuable services to human society. However, these ecosystems are facing multiple impacts of human-induced stress, including overexploitation, eutrophication, land construction, and global climate change. The prediction of long-term changes in coastal ecosystems under multiple impacts is difficult because nonlinear and cumulative effects operate simultaneously. This difficulty is especially true for Asian regions, where coastal biodiversity is the world’s highest but the least studied. In this chapter, we compare ecosystem services of coastal areas of Asia based on the expert knowledge of practioners who study coastal ecosystems at each locality. We especially focused on seagrass beds, which provide important services to humans including provision of seafood and regulation of water conditions. We selected the six most important ecosystem services at each of 13 seagrass beds ranging from Japan to India and evaluated the direction of changes over the past two decades. We also evaluated public awareness and data certainty for each service. Food provisioning, water purification and waste treatment, erosion regulation, recreation and ecotourism, and educational values were selected as major ecosystem services of seagrass beds. Degradation during the over past 10–20 years was reported for most provisioning and regulating services, whereas improving trend was found for cultural services in most sites. Public awareness and certainty of information were generally high for provisioning services, but low for most regulating services. Regional variation along latitude, and differences between temperate and tropical seagrass beds, were not detected for the examined variables. Regional comparisons of ecosystem services shed light on general and specific aspects of the status of seagrass beds, which will provide baseline data for planning effective conservation and management strategies under multiple human impacts.

Seagrass in Southeast Asia: a review of status and knowledge gaps, and a road map for conservation

Abstract Southeast Asia has the highest diversity of seagrass species and habitat types, but basic information on seagrass habitats is still lacking. This review examines the known distribution, extent, species diversity, and research and knowledge gaps of seagrasses in Southeast Asia by biogeographic region of the Marine Ecoregions of the World (MEOW). The extent of seagrass meadows in Southeast Asia is ~36,762.6 km2 but this is likely an underestimate as some ecoregions were not well-represented and updated information was lacking. There is a paucity of information from the Western Coral Triangle Province, with no areal extent data available for the Indonesian regions of Kalimantan, Central and Southeast Sulawesi, the Maluku Islands, and West Papua. Regional research output has increased in the last two decades, with a trend towards more experimental, rather than descriptive research. However, there are knowledge gaps in socio-cultural-economic themed research, despite growing awareness of the importance of seagrass-human relationships in this region. Obstacles to advancing seagrass research, knowledge and conservation are rooted in either lack of expertise and training or the failure of effective management and policies. We propose a roadmap for seagrass conservation, with suggested solutions, including 1) encouraging collaboration between research institutions and scientists in the region to build capacity and share knowledge; 2) engaging with policymakers and governments to encourage science-based policies; 3) engaging with communities to raise awareness and foster stewardship of seagrass in the region.

A proposed decision support tool for prioritising conservation planning of Southeast Asian seagrass meadows: combined approaches based on ecosystem services and vulnerability analyses

Abstract Seagrass habitats provide a range of goods and benefits to coastal communities by supporting ecosystem functioning, food provisioning, and cultural values. However, they are at risk worldwide from anthropogenic activities, climate change impacts and limited resources, which hamper efforts to protect them. Effective conservation planning requires prioritisation of sites based on multiple factors, including their relative value and vulnerability (VU). The current study examines the efficacy of combining two well-established approaches – ecosystem service assessments and habitat VU analyses – to test a method for determining conservation priority for selected seagrass meadows in Southeast Asia. Seven seagrass meadows around Southeast Asia were selected and scored by the authors based on (1) the cumulative contribution of 12 ecosystem services (ES) and the condition of the meadows, (2) VU from 16 anthropogenic threats, which were each ranked against five factors (spatial scale, frequency, functional impact, resistance and recovery time) and (3) the combination of the two approaches to create a single numerical index. Prioritisation of sites differed when meadows were scored solely for the ES they provide, compared to how vulnerable they are to anthropogenic threats. The new combined analysis brought the two metrics together to give conservation priority to sites where management intervention will yield maximum conservation benefits from conservation effort, and resulted in the prioritisation of three sites: Barrang Lompo (Indonesia), Cape Bolinao (Philippines) and Beting Tanjung Kupang (Malaysia). This method is easy to use and does not require great technical expertise. It is also auditable, allowing for clear and transparent understanding of decision-making process.

The diet and feeding rates of gastropod grazers in Singapore’s seagrass meadows

Abstract A wide variety of organisms are known to graze on seagrasses and their associated epiphytes, and this plant-animal interaction can affect the health of seagrass meadows. Grazing patterns tend to vary across meadows and faunal groups, and little is known regarding how gastropod grazers influence meadows in the tropics. To better understand this interaction, we surveyed the gastropod diversity in five meadows in Singapore. Further, grazing potential (i.e. potential food sources and feeding rates) of common gastropod species was quantified through ex situ grazing experiments, while their diet compositions were elucidated using dual δ13C and δ15N stable isotope analyses. The surveys revealed a high diversity of 274 gastropod species/morphospecies while PERMANOVA and SIMPER analyses showed that communities differed significantly among sites but not among seagrass species. Diet composition analysis indicated that seagrass leaves were the main food source for most gastropod species examined while epiphytes were important for microsnail (shell size <5 mm) species. However, all the gastropod species tested fed on epiphytes in the ex situ experiments. These findings contribute new insights into grazing by marine gastropods on tropical seagrass meadows, and highlight the potential importance of both direct grazing and epiphyte removal on tropical meadows.