Laura T. David

Sea-surface temperature and thermal stress in the Coral Triangle over the past two decades

Increasing ocean temperature has become one of the major concerns in recent times with reports of various related ecological impacts becoming commonplace. One of the more notable is the increased frequency of mass coral bleaching worldwide. This study focuses on the Coral Triangle region and utilizes the National Oceanic and Atmospheric Administration-Coral Reef Watch (NOAA-CRW) satellite-derived sea surface temperature (SST) and Degree Heating Weeks (DHW) products to investigate changes in the thermal regime of the Coral Triangle waters between 1985 and 2006. Results show an upward trend in SST during this period with an average rate of 0.2°C/decade. However, warming within this region is not uniform, and the waters of the northern and eastern parts of the Coral Triangle are warming fastest. Areas in the eastern part have experienced more thermal stress events, and these stress events appear to be more likely during a La Niña.

Automated benthic counting of living and non-living components in Ngedarrak Reef, Palau via subsurface underwater video

We introduce an automated benthic counting system in application for rapid reef assessment that utilizes computer vision on subsurface underwater reef video. Video acquisition was executed by lowering a submersible bullet-type camera from a motor boat while moving across the reef area. A GPS and echo sounder were linked to the video recorder to record bathymetry and location points. Analysis of living and non-living components was implemented through image color and texture feature extraction from the reef video frames and classification via Linear Discriminant Analysis. Compared to common rapid reef assessment protocols, our system can perform fine scale data acquisition and processing in one day. Reef video was acquired in Ngedarrak Reef, Koror, Republic of Palau. Overall success performance ranges from 60% to 77% for depths of 1 to 3 m. The development of an automated rapid reef classification system is most promising for reef studies that need fast and frequent data acquisition of percent cover of living and nonliving components.

Past and future fisheries modeling approaches in the Philippines

Philippines coastal fisheries research started during the colonization period in the 1800s with the basic taxonomic identification of the countries aquatic resources and a description of their distribution in national waters. Research further evolved with the change from localized fisheries governance to a centralized one, presently, with a combination of both. The dramatic postwar expansion of Philippine fisheries in the mid 1940s led to the need for sustainable resources management. In the mid-1970s, single-species fisheries approaches (i.e. specifically surplus production models) indicated the overfished state of the Philippine coastal fisheries resources. These early models together with additional ecological and socioeconomic studies, served as inputs to coastal resources management initiatives, in the context of an ecosystem approach. The implementation of further management schemes such as marine reserves and fish sanctuaries also resulted from these initiatives. The decentralization of governance of coastal resources in the 1990s led to participatory or co-management approaches for the local governance of coastal resources. The development and great improvement of ecosystem-based models in fisheries science (such as Ecopath with Ecosim [EwE]) during this period allowed for investigations into the interactions of the multispecies and multigear fisheries dynamics. Complementary models derived from single-species such as Yield per Recruit and Surplus production in conjunction with ecosystem-based (EwE-type) approaches are both needed in Philippine fisheries research. An emerging framework for sustainable Philippine fisheries management system requires mainstreaming of coastal governance with science based adaptive management for Philippine aquatic resources governance.

Fish population estimation and species classification from underwater video sequences using blob counting and shape analysis

Fish population estimation and classification of fish species have been an integral part of marine science research. These tasks are important for the assessment of fish abundance, distribution and diversity in marine environments. We describe an efficient method for fish detection, counting, and species classification from underwater video sequences (UWVS) using blob counting and shape analysis. The video sequences were obtained with a moving camera resulting in rapid viewpoint changes thereby making it difficult to employ motion detection schemes in extracting fish images from background. Video preprocessing involved blackening out the corals from the underwater videos. This is done in order to effectively estimate fish count in the environment, though excluding those that are against a coral background. We then applied histogram comparison to initially blacken out the occlusions using blue and non-blue templates obtained randomly from the UWVS. We then introduced an erasure procedure to further aid in removing the coral background For fish detection, Canny edge detection was applied to extract fish contours. After the latter have been delineated, blob counting is then employed to in order to compute the fish count. Due to rapid frame changes, the average fish count per unit time is computed from the counts in each frame. For shape analysis, blob size is initially estimated and when a threshold is exceeded, Zernike moment-based shape analysis is performed on the blob for comparison with moment signatures of selected fish species stored in a database. The label of the best matching moments identifies the species of the fish blob. The shape-based classification algorithm is designed to identify the two most common species of fish found in the Tubbathaha reef in Sulu Sea, Philippines.

Microhabitat use of juvenile coral reef fish in Palau

While relationships between adult fish density and structural habitat features are well established, relatively little is known about the habitat associations of juvenile reef fish. In a reserve system in Palau, we quantified microhabitat association with juvenile reef fish community structure, and determined the influence of foraging space, predator size and confamilial attraction on juvenile and adult pomacentrid abundance. Habitat structure and juvenile reef fish communities differed significantly among microhabitats with one exception: no difference was found between foliose and consolidated rubble microhabitats. Overall, pomacentrids characterised the juvenile community structure of each microhabitat. The abundance of early juvenile pomacentrids is simultaneously determined by microhabitat structure and predator size, with little evidence for settlement selection near adults. The results also suggest that the influence of habitat structure become weaker with ontogeny which in part, drives large predators to negatively influence the abundance of adult pomacentrids. The results have important implications on management, specifically in prioritizing areas for protection, and in modeling the impacts of habitat loss on reef fish communities.

I-C-SEA Change: A participatory tool for rapid assessment of vulnerability of tropical coastal communities to climate change impacts

We present a synoptic, participatory vulnerability assessment tool to help identify the likely impacts of climate change and human activity in coastal areas and begin discussions among stakeholders on the coping and adaptation measures necessary to minimize these impacts. Vulnerability assessment tools are most needed in the tropical Indo-Pacific, where burgeoning populations and inequitable economic growth place even greater burdens on natural resources and support ecosystems. The Integrated Coastal Sensitivity, Exposure, and Adaptive Capacity for Climate Change (I-C-SEA Change) tool is built around a series of scoring rubrics to guide non-specialists in assigning scores to the sensitivity and adaptive capacity components of vulnerability, particularly for coral reef, seagrass, and mangrove habitats, along with fisheries and coastal integrity. These scores are then weighed against threat or exposure to climate-related impacts such as marine flooding and erosion. The tool provides opportunities for learning by engaging more stakeholders in participatory planning and group decision-making. It also allows for information to be collated and processed during a “town-hall” meeting, facilitating further discussion, data validation, and even interactive scenario building.

The saga of community learning: Mariculture and the Bolinao experience

The per capita fish consumption in the Philippines has not significantly changed through the years (1987–2003), but the increase in human population has created an ever-increasing demand for food fish. The Philippine Bureau of Fisheries and Aquatic Resources has responded to the food fish shortage by promoting mariculture. We support this policy within a comprehensive planning and management framework that includes siting and density of mariculture facilities. The case of Bolinao-Anda, Pangasinan is presented in this article to highlight the multi-faceted process for a successful mariculture enterprise. We use remote sensing tools to track the responses of stakeholder groups to various local legislation, mariculture-induced disasters, and scientific recommendations. Using hydrodynamic models, we assess these responses and highlight potential adjustments that may alleviate the pressure on and maintain the ecosystem health of the Bolinao-Anda coastal waters.

Drifters as preliminary site assessment tool for ocean current-based renewable energy for straits and channels in the Philippines

We study the possibility of using ocean surface drifting buoys (“drifters”) as a low-cost alternative to assess the potential of a tidal channel to deliver useful renewable energy. Instead of using Acoustic Doppler Current Profilers (ADCP) for underwater ocean current measurement, we propose the use of drifters released on localized areas of interest which is more affordable and flexible for use of coastal communities in the Philippines. We discuss the drifters used in our experiments and show our methodology with field results obtained from an actual drifter deployment on April 2010 in the Mactan-Olango Channel of Cebu, and in Ligpo island, Anilao, Batangas, Philippines. Since power extraction devices and systems used for tidal currents primarily take into account flow speed in the channel, we present flow speed data derived from the Mactan-Olango and Ligpo drifter deployments. We also discuss how this effort can be refined and replicated to yield site assessment guidelines including power prediction estimation using drifter data.

Delineating optimal settlement areas of juvenile reef fish in Ngederrak Reef, Koror state, Republic of Palau

Establishing the effectiveness of habitat features to act as surrogate measures of diversity and abundance of juvenile reef fish provides information that is critical to coral reef management. When accurately set on a broader spatial context, microhabitat information becomes more meaningful and its management application becomes more explicit. The goal of the study is to identify coral reef areas potentially important to juvenile fishes in Ngederrak Reef, Republic of Palau, across different spatial scales. To achieve this, the study requires the accomplishment of the following tasks: (1) structurally differentiate the general microhabitat types using acoustics; (2) quantify microhabitat association with juvenile reef fish community structure; and (3) conduct spatial analysis of the reef-wide data and locate areas optimal for juvenile reef fish settlement. The results strongly suggest the importance of branching structures in determining species count and abundance of juvenile reef fish at the outer reef slope of Ngederrak Reef. In the acoustic map, the accurate delineation of these features allowed us to identify reef areas with the highest potential to harbor a rich aggregation of juvenile reef fish. Using a developed spatial analysis tool that ranks pixel groups based on user-defined parameters, the reef area near the Western channel of Ngederrak is predicted to have the most robust aggregation of juvenile reef fish. The results have important implications not only in management, but also in modeling the impacts of habitat loss on reef fish community. At least for Ngederrak Reef, the results advanced the utility of acoustic systems in predicting spatial distribution of juvenile fish.

Insights into the dynamics of harmful algal blooms in a tropical estuary through an integrated hydrodynamic-Pyrodinium-shellfish model

In contrast to temperate Harmful Algal Blooms (HABs), knowledge on the mechanisms driving tropical HABs are less well studied. The interaction of a seasonal temperature window, cysts (for certain species) and large-scale transport are some of the key processes in temperate HABs. In the Philippines, HABs occur not along long open coastlines, but in embayments that are highly influenced by run-off and stratification. These embayments are typically also the sites of cultured or wild harvest shellfish and other aquaculture activities. Sorsogon Bay in the northeastern Philippines has experienced prolonged shellfish-harvesting bans due to blooms by Pyrodinium bahamense var. compressum severely affecting the fisheries industry in this area, as well as leading to Paralytic Shellfish Poisoning illnesses and fatalities. A novel integrated model was developed that mechanistically captures the interactions between hydrodynamic conditions, nutrients, the life history (cells and cysts) of Pyrodinium, as well as the cultured shellfish within the bay and their ensuing toxicities due to ingestion of toxic Pyrodinium cells and cysts. This is the second model developed for HABs in the Philippines, and the first to integrate different components of Pyrodinium bloom dynamics. The model is modularly composed of a watershed nutrient and diffusion model, a 3D hydrodynamic model, a Pyrodinium population model and a shellfish toxin model. It was able to capture the observed temporal variations of Pyrodinium and shellfish toxicity. It was also able to represent some aspects of the spatial distribution in Sorsogon Bay though there were discrepancies. To explore the dynamics of blooms, the linkages between the bloom and decline of the Pyrodinium population with shellfish toxicity as affected by temperature, salinity and nutrients were investigated. Comparisons with field results showed the seasonality of blooms in Sorsogon Bay is driven by increased rainfall. The timing of these conditions is important in facilitating Pyrodinium excystment and reproduction. Model results showed as well the potential significance of shellfish grazing and dinoflagellate cell mortality in influencing the decline of the bloom, and toxicity levels. This approach is promising in helping to understand mechanisms for HABs more holistically, and the model can be further improved to provide more precise quantitative information.