Navigating the Depths: A Comprehensive Review of 40 Years of Marine Oil Pollution Studies in the Philippines (1980 to 2024)

Abstract

This review synthesizes four decades (1980–2024) of marine oil spill research in the Philippines, analyzing 80 peer-reviewed publications sourced from Scopus, Web of Science, Clarivate, and Google Scholar. Findings show that oil spill research activity spikes after major spills, particularly the 2006 Guimaras incident, which accounts for over half of the reviewed studies and were mostly concentrated in the field of biology, followed by social sciences. Mangroves are the most studied as they are the widely affected ecosystem in the Philippines. Despite the number of published articles on oil spills in the Philippines, only the major events were emphasized, and small-scale spills remain under documented. Research on small-scale oil spills and the country’s two recent big oil spills (Mindoro Oil Spill and Manila Bay Oil Spill), particularly in a country’s environmentally sensitive areas, must be conducted in collaboration with academic institutions and relevant stakeholders to gain a deeper understanding and formulate appropriate countermeasures in the event of future spills. The review also highlights limited application of advanced techniques such as hydrocarbon fingerprinting, geospatial analysis, and next-generation DNA sequencing, limiting comprehensive assessments of oil fate and ecological effects. Addressing these gaps through interdisciplinary collaboration is critical to improving oil spill response, environmental management, and policy formulation in the Philippines’ complex archipelagic setting.

1. Introduction

Oil spills are major environmental disasters that may occur worldwide on different scales and in various forms [1], as well as in various types of environmental matrices, on land, at sea, and in freshwater systems [2]. Oil spills are considered one of the inevitable catastrophic events that serve as a significant threat across various ecosystems, as they often lead to a series of detrimental long-term environmental effects [3,4], impose negative socioeconomic impacts [5,6], and affect the overall health and well-being of the people [7,8].

Globally, there has been a rapid increase in the extraction, use, and demand for oil and petroleum-based products, which has led to an increase in marine oil pollution [9,10]. It is projected that by the year 2030, global oil consumption will increase to more than 113 million barrels per day [11]. In addition, sources of oil spills are not limited to vessel sources only but also include non-vessel sources [12], such as industrial and urban runoff, leakage from pipelines, and natural seepage. Therefore, there are a high number of oil spill incidents in the world; the overall quantity of oil spilled into the environment is relatively small compared to the total amount of oil being utilized globally [13]. Nevertheless, the occurrence of major oil spills has considerably devastating impacts, which depend on the amount and nature of the spill, the ambient conditions, and the level of sensitivity of the affected organisms, as well as their habitats [14].

The Philippines is known for its mega-diverse marine resources and location within the Coral Triangle, which has great potential as a blue economy (House Bill No. 69, 2022) [15]. With over 7000 islands surrounding the Philippine archipelago and one of the longest coastlines in the world, the country is extensively involved in domestic and international marine operations, fostering trade and cultural exchange throughout history [16], which plays a significant role in the country’s economy. The Verde Passage, lying between Batangas and Mindoro alone, is renowned for being home to a highly diverse marine species, accounting for approximately 60% of the world’s known marine organisms. Globally, the Philippines is hailed as one of the top contributors to the world fisheries ranking, ranking 13th among the top fish producers and 4th in seaweed production worldwide [17]. On top of that, maritime transport has been the leading means of transportation across the country’s islands. The total number of domestic vessels in the Philippines has significantly increased over the years. In 2015, the number of registered vessels was 25,063, which was 91% more than in 2011 [18]. Similarly, in 2021, the Maritime Industry Authority recorded 31,814 registered vessels, which was 6% more than the 29,974 registered vessels in 2020 [19].

As maritime activities grow in the Philippines, the risk of oil spills and the possibility of ship collisions increases, potentially harming the environment and human health [20,21]. The Philippine Coast Guard (PCG) has created the National Oil Spill Contingency Plan (NOSCOP) to address such risks. This plan provides clear guidelines for government agencies and non-government organizations (NGOs) in responding to oil spills [12], and it can be adjusted based on the severity and scale of an oil spill incident [13]. Beyond emergency response, the National Integrated Marine and Coastal Area Management (IMCAM) promotes sustainable practices, conservation efforts, and community engagement to protect marine and coastal areas [15]. Additionally, by studying oil spills and using scientific data, authorities can create better emergency response plans, predict risks, and reduce the damage oil spills cause to the environment and communities [22].

Alea et al. (2022) reviewed aquatic oil spills in the Philippines from 2000 to 2021, focusing on the number, size, sources, and causes of spills using data from the Philippine Coast Guard, NDRRMC, and media reports [12]. While their work offers valuable information on oil spill incidents during that time period, the current review adopts a broader approach by analyzing peer-reviewed publications across multiple disciplines. This review aims to synthesize the published literature on oil spill events in the Philippines spanning 40 years from 1980 to 2024 to establish a comprehensive understanding of their impacts on the environment, economy, and local communities. Specifically, this study seeks to: 1. analyze research trends related to oil spills across different disciplines in the Philippines; 2. identify and categorize the organisms studied in oil spill research in the Philippines; and 3. identify research gaps in oil spill studies in the Philippines.

2. Materials and Methods

A literature search on oil spills in the Philippines was performed in February 2025 using Scopus, Clarivate Web of Science, and Google Scholar. The search included keywords such as “oil spill Philippines”, “marine spill Philippines”, “heavy oil Philippines”, “Guimaras oil spill”, “Mindoro oil spill”, “hydrocarbon Philippines”, “Manila Bay oil spill”, and “oil biodegradation Philippines”. The following criteria were used during the screening process to ensure that the selected studies were relevant: 1. published in peer-reviewed journals; 2. specifically address oil spills within the Philippines; 3. include empirical data rather than just review articles; and 4. published between 1980 and 2024. Review papers and articles that did not meet the said criteria were excluded.

After this process, a total of 80 journal articles were selected and organized into a Microsoft Excel file, starting with the oldest studies on oil spills in the Philippines down to the most recent ones. These articles were then categorized into different disciplines, including biology, social sciences, chemistry, engineering, modeling, biotechnology, and toxicology, with interdisciplinary studies also considered. To further examine the biological impacts of oil spills, studies in the biology category were grouped based on the organisms they investigated, such as corals, bacteria, fish, mangroves, shrimp, seagrass, fungi, echinoderms, plankton, terrestrial species, and mollusks. Additionally, to capture the specific focus areas within broader disciplines, engineering and social science fields were further classified into sub-disciplines. The engineering field included studies in environmental engineering, mechanical/marine engineering, geospatial/remote sensing, materials engineering, electronics/electrical engineering, systems engineering, and computer engineering, while the social sciences field covered areas such as interdisciplinary studies, public health, economics, history, public administration, development studies, sociology, policy studies, and maritime studies. Lastly, the selected articles were analyzed based on publication trends over five-year intervals and mapped according to the geographic location of the oil spills (Luzon, Visayas, or Mindanao) and the reported volume of oil spilled.

While this study does not claim to cover all existing research on the topic, the selection of 80 journal articles reflects the literature available in major academic databases at the time of the search. Other potential sources were not included, such as non-indexed journals, gray literature like government reports and theses, or studies using different terminology.

3. Results and Discussion

3.1. Distribution and Volume of Oil Spills

As mentioned by Musk (2012) [23], there has been a significant and ongoing decline in the global average number of oil spills that release seven tons or more of oil over the past 60 years. Globally, the number of oil spill incidents consistently decreased from 2010 to 2014, which may be a result of the combined efforts of the governing bodies in enhancing safety and pollution control measures [24]. However, 34, 38, and 42 oil spills were recorded in the Philippines in 2008, 2012, and 2018, respectively. Most of these oil spills were recorded as minor spills [12].

As shown in Figure 1, three of the six oil spill incidents mentioned in the published articles happened in Visayas, while the other three happened in Luzon. Based on this information alone, we cannot determine which specific area in the Philippines experiences the most oil spills, as the incidents displayed in

Table 1. Oil spill events in the Philippines mentioned in the published articles from 1984 to 2024.

Name of Oil Spill	Location	Date (yyyy-mm-dd)	Cause	Source	Volume (Liters)	Impacts
Guimaras Oil Spill	Guimaras Island, Visayas	2006-08-11	Sinking of M/T Solar 1 Oil Tanker	Vessel	2,100,000	heavily damaged the mangrove forests, affected other marine organisms, and disrupted the communities’ livelihood activities
Diesel Spill	Polillo Island, Quezon Province	2012-04-03	Leak in the generator of NAPOCOR’s power source	Power plants and power barges	10,000	the oil leaked extended to the shore with fetid smell, causing nausea to the nearby residents
MV Sulpicio Express 7 Oil Spill	Talisay City, Cebu	2013-08-16	Ferry ship M/V St. Thomas Aquinas collided with cargo ship Sulpicio Express 7	Vessel	160,000	damaged ~5000 ha of mangroves, affected the livelihood of local fishermen and vendors
Estancia Oil Spill	Estancia, Iloilo	2013-11-08	Power Barge No. 103 ran aground at the shores of Estancia during the height of typhoon Haiyan	Vessel	800,000	contaminated the coast, river, and mangroves, causing a threat to the communities’ livelihood
Mindoro Oil Spill	Oriental Mindoro	2023-02-28	M/T Princess Empress sank	Vessel	800,000	damaged marine protected areas and ecological sanctuaries, affected tourism, caused loss in the livelihood of the local community
Manila Bay Oil Spill	Manila Bay	2024-07-25	Tanker Terranova sank	Vessel	1,400,000	heavily affected the livelihoods of the fisherfolk

are only those investigated in the published articles and are insufficient to represent the entire record of oil spills. Moreover, areas with high shipping activity, such as areas near coastlines, ports, and oil infrastructures, are more likely to experience oil spills [4,25], as these risks positively correlate with high levels of maritime traffic [26].

The Guimaras oil spill in 2006 was the most extensively documented oil spill incident in the reviewed literature, accounting for 55% (44 articles) of the total studies. This event occurred on 11 August 2006, when the SOLAR 1, an oil tanker weighing 998 gross tons (GT), sank in the Guimaras Strait, releasing approximately 2,100,000 L of oil. The spill resulted in the contamination of over 450 hectares of protected mangroves, extensive coastal pollution [27], and severe disruptions to fishing activities, adversely affecting coastal communities [28]. Thus, the impacts of an oil spill incident need to be thoroughly assessed across various perspectives, including social and economic ones [29]. On the other hand, only two articles have been published on the Mindoro Island oil spill in 2023, despite releasing 800,000 L of oil. Potentially serious consequences could have resulted, necessitating further analysis and more publications. Similarly, the Manila Bay Oil Spill in July 2024, the most recent oil spill, has only one published article available. This could be because the incident is still new, and investigations might remain ongoing. It is also possible that research on the spill is in the process of being published.

Since the scope of the impact has not been fully determined yet, it makes sense that there is limited published work so far. Additionally, these studies often take time to gather data and evaluate the environmental, economic, and social effects before they can be fully reported. Because of this, the full extent of the spill’s impact has yet to be assessed.

3.2. Oil Spills in the Published Literature

From 2000 to 2001, 467 oil spill incidents were recorded in the Philippines, as reported in the study of Alea et al. (2022) [12]. However, out of the 80 published articles reviewed in this study, only 6 oil spill incidents were systematically investigated from 1980 to 2024 (Table 1). Of these 80 articles, the 2006 Guimaras oil spill accounted for 55% of the studies, making it the most extensively researched event. It is the largest oil spill in Philippine history, releasing 2,100,000 L of heavy oil, contaminating approximately 200 km of shoreline across neighboring islands. This extensive impact prompted numerous studies across various fields, including sediment and water contamination, bacterial population dynamics, damage assessment of the marine environment, and evaluating the social and economic impacts, among others.

Accordingly, research concerning oil spills heavily favors more severe occurrences [25], focusing predominantly on extensive negative impact. In contrast, oil spills of medium to minor intensity receive less attention and consequently are not documented. However, on 24 March 1989, the Exxon Valdez oil tanker released 37,000 metric tons (260,000 barrels) of crude oil when it accidentally grounded in Prince William Sound, Alaska. Despite being smaller in volume, it gained significant public and scientific attention due to its devastating effects on marine life, fisheries, and coastal ecosystems, leading to 91 published studies [30]. Similarly, the largest marine oil spill in history was recorded in the Gulf of Mexico when the Deepwater Horizon spill incident happened in April 2010, releasing 4.9 million barrels (780,000 metric tons) of crude oil [30]. Its scale and complexity prompted extensive scientific investigations, resulting in 150 published studies covering biodegradation, chemical dispersants, microbial responses, and ecosystem recovery.

Although major oil spills attract more attention, leading to numerous studies that provide an array of knowledge and understanding beneficial not only to the scientific community but also the governing bodies in predicting, drafting, and establishing countermeasures for future oil spills, this focus overshadows the occurrence and effects of more minor spills. As a result, the impacts of smaller spills on the environment and human health are not well understood or recognized across communities. Despite their smaller volume, minor oil spills are much more frequent, greater in number, and more geographically widespread than the larger spills [2,31].

3.3. Sources and Causes of Oil Spills

Oil spills come from a wide variety of sources and have multiple causes. Table 1 shows four causes of oil spills in the Philippine literature: ship sinking, ship collisions, ship grounding, and leakage. As mentioned by Schmidt-Etkin (2011) [2], oil transport by tankers and leakage from pipelines have been considered the major causes of oil spills for the past 20 years. Oil spills due to ship collisions are increasing due to heavy shipping traffic [32]. In addition, about 30–50% of oil spills are caused by human actions, while 20–40% are due to equipment failure [9]. Another reason for oil spills is unfavorable weather conditions, which are well known to cause ships to run aground or sink [23]. Given the Philippines’ vulnerability to storms and typhoons, it is necessary to strengthen ports and vessels to increase their ability to withstand adverse weather conditions.

On the other hand, vessels have been the major source of oil spills [33]. This trend is reflected in the Philippines, where 55% of the 467 oil spills recorded were caused by ships [12]. In this study, the majority of the sources of the oil spills investigated in the literature were due to ships, with only one due to a leak from an electrical power generator. Although oil spills can be considered as abrupt events, establishing a baseline data set of their trends and patterns, as well as improving the National Oil Spill Contingency Plan (NOSCOP), will not only help to mitigate the consequences of oil spills but also strengthen countermeasures to prevent such incidents.

3.4. Literature Published over Time

The number of articles published is shown in Figure 2, from 1980 to 2024, with a five-year interval. The year interval shows that the number of articles published was highest in 2011–2015, followed by 2006–2010 and 2021–2024. These intervals are interconnected due to a massive oil spill incident in Guimaras on 11 August 2006 [34]. The incident heavily impacted the coastlines of several nearby and adjacent islands. As a result, the published articles for these year intervals were abundant. Nevertheless, there were no articles published in the year the spill occurred, and it took two years before the first articles on the Guimaras oil spill were published. On the other hand, studies from 2016 to 2024 mainly reported the analysis of marine bacterial community structure using next-generation sequencing [21] and material characterization of natural zeolites for oil pollution remediation [35].

From 1980 to 1985, the research focused on oil spill contingency planning and trajectories specific to the countries near or in the South China Sea, including the Philippines. Earlier studies focused more on the impact of oil spills on marine resources [36,37], and later, a simulation program was developed to predict future oil spill trajectories [38]. These studies paved the way for developing more advanced modeling techniques to mitigate actual oil spill tragedies. By this time, there had already been a study on using water washing to speed up the biodegradation process of heavy oil contaminants [39]. Although Figure 2 shows no published literature for the following year, the lack of major oil spills in the country at that time may have contributed to the lack of published studies. From 1996 to 2000, there was a study in the field of biotechnology in the Philippines using bacteria for its oil-degrading activity in a laboratory setting. This study area of research still needs more attention, as the Philippines has a wide variety of natural resources that can potentially remediate oil spills.

3.5. Research Field in Oil Spill Research

Figure 3 illustrates the changes in the number of published articles across different research fields over time. The graphical depiction reveals a greater prevalence of published articles in biology, followed by social sciences, chemistry, and engineering. Following the Guimaras Oil Spill, the notable surge in published articles in the field of biology is attributed to the research focusing on the direct impacts of the catastrophic spill on marine species. These studies examined the impact of oil contamination on mangroves [40], bacteria [41], fish, corals, plankton [42], echinoderms, fungi [43], and seagrass [44].

Following the field of biology, the social sciences were the second most prolific field of study. This can be attributed to the studies investigating the effects of the Guimaras oil spill on various aspects of human life, including livelihood [45,46,47], health [48,49], food security [28], community security [50,51,52,53], and other aspects. Meanwhile, the field of chemistry continues to be an abundant research field. Most studies in chemistry primarily focused on two main areas: the monitoring of polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs in aquatic organisms one month after the 2006 Guimaras oil spill [27], and examining the influence of PAHs on bacteria involved in oil degradation [27,54,55].

The lowest number of articles was observed in toxicology [56] and biotechnology [57]. However, these studies were not limited to a single field but included several fields using interdisciplinary approaches. For example, the study of Abejero et al. [58] spans engineering, biology, and chemistry. Although the graph highlights the studies within specific disciplines, few articles integrate multiple fields, such as biology, social sciences, engineering, chemistry, modeling, toxicology, and biotechnology, to comprehensively understand oil spills’ impacts on marine ecosystems and human societies.

In biology, the number of articles increased significantly between 2006 and 2010, followed by a decline in the following periods: 2011 to 2014, 2016 to 2020, and 2021 to 2025 (Figure 3). However, biology has the highest number of articles among all fields throughout the timeline. The remarkable number of articles in this field can be attributed to the occurrence of the massive Guimaras oil spill that happened in 2006 [34] and other more minor oil spills in the Philippines [12]. Researchers have also explored the ecological impacts of oil spills on various organisms such as shrimp [59], fungi [43], fish, corals, plankton [42], bacteria [41], and phytoplankton [60], as well as the effects of polycyclic aromatic hydrocarbons (PAHs) on aquatic life [55].

Between 2006 and 2010, social science research on oil spill-related studies increased, with a significant spike between 2011 and 2015. This increase is mainly due to studies exploring the impacts and effects of oil spills on people’s livelihoods, health and safety, and the local economy. During this period, research also focused on oil spill preparedness [38,52], and the role of NGOs in disaster response [53]. From 2011 to 2024, there was a rise in studies in chemistry and engineering, which was driven by new technologies. These included research on oil spill monitoring using remote sensing [61,62,63] and the development of floating devices with non-contact infrared sensors to detect crude oil [64]. Many studies focused on improving early detection methods, like the work of Matkan et al. [65], who used radar images and machine learning techniques to detect oil spills, such as the Synthetic Aperture Radar and Support Vector Machine.

3.6. Organisms as Indicators and Remediators

Figure 4 shows the different types of organisms studied in the biology articles included in the present review. Of the 40 species studied, mangroves were the most widely studied, with nine articles (22.0%). This is followed by bacteria (17.1%), which are often used in studies due to their biodegradation potential, and plankton (14.6%). Terrestrial flora accounted for 9.8%, while fish, seagrass, and mollusks each represented 7.3%, mainly due to their importance in food security and the economy. The least studied organisms are echinoderms, coral, fungi, and crustaceans (shrimps), ranging from 2.9% to 4.9%, with fewer than three studies for each group.

Mangroves are the most studied organism type in the reviewed literature. This is due to their role in the coastal ecosystem, and they are the most affected and visible habitat in the Philippine environment. Most marine resources, such as fish, spawn in mangrove forests, providing subsistence activities for fish in the area [28]. However, it is also the most vulnerable coastal ecosystem in the country. It is worth noting that globally, 238 oil spills have occurred along mangrove coastlines [66]. Thus, studies on the effects of oil spills on mangroves are the most abundant in the oil spill literature. It could be of great interest to investigate the phytoremediation potential of mangroves to mitigate oil spills, as studies using plants are pretty scarce, as shown in Figure 4. Bacteria are the second most studied type of organism in the reviewed literature, and these microorganisms play a significant role in the biodegradation of crude oil compounds [41]. Studies involving these organisms require DNA analysis equipment to unravel further the bacterial consortia that degrade high levels of oil compounds [21].

Most studies of oil spills focus on intertidal or sublittoral areas, where the effects of such spills are more obvious than the species present in the planktonic community and other marine organisms in the pelagic zone [67]. The planktonic community, which is at the base of the food web, is crucial in the marine ecosystem, particularly in nutrient cycling [68]. They are also key players in the productivity of marine ecosystems [69]. At the onset of an oil spill, these organisms are usually the first to come into contact with the oil compounds due to their proximity to the surface water carried by the current, and the effect on the plankton assemblage could be transmitted through the next trophic level in the aquatic food chain [70]. Therefore, plankton may be sensitive indicators of the occurrence and extent of oil spills. Plankton are studied for their abundance and diversity in the literature reviewed before and after an oil spill. However, the studies on plankton have focused more on their role as environmental bioindicators; they could also be used in the remediation of these pollutants.

Overall, organismal oil spill research in the Philippines has excellent potential to provide comprehensive data for oil spill mitigation and management of affected natural resources. Coastal communities are directly affected by this incident; therefore, their knowledge should also be studied to assess the severity of oil spills on the lives of those who depend on marine resources. There is a lot of potential in studying the fate of oil spills in the environment, such as marine snow, tarball formation, oil weathering, and photooxidation, and how these flora and microorganisms can be used for bioremediation potential. What the country lacks, however, are research facilities that could address a wide range of issues related to oil spills.

3.7. Engineering Sub-Discipline in Oil Spill Research in the Philippines

Engineering is critical in advancing oil spill research, particularly in developing response systems, detection technologies, modeling tools, and remediation materials. Figure 5 shows the distribution of various engineering sub-disciplines investigated in the engineering studies included in the review. Environmental engineering emerged as the most dominant field (36%), consistent with the ecological nature of oil spill mitigation, focusing on sorbent materials, clean-up systems, and spill response modeling [71]. This is followed by Geospatial and Remote Sensing (21%), which involves using SAR and optical satellite images, GIS-based oil extent mapping, and image classification techniques for monitoring and detection [72]. Other relevant disciplines include materials engineering (14%), commonly seen in studies that developed natural or modified oil sorbents like kapok fiber [58], zeolite [35], and activated carbon [73]. Systems engineering (14%) was represented by studies applying system dynamics modeling, hydrodynamic simulation using EFDC, and an oil trajectory forecasting tool like GNOME [74]. Computer engineering (7%) appeared in studies incorporating machine learning approaches to improve the accuracy of oil detection from satellite imagery [75]. Lastly, a smaller portion of the studies involved electronics/electrical engineering (4%) and mechanical/marine engineering (4%), which covered sensor-integrated buoy systems and the physical design and deployment of ocean monitoring equipment, respectively [64]. This distribution underscores the interdisciplinary nature of oil spill engineering research in the Philippines, while indicating fields that are less represented that could improve future research through more integrated and holistic approaches.

3.8. Social Science Sub-Disciplines in Oil Spill Research in the Philippines

Studies under the discipline of social science cover different socio-economic factors to understand and address the impacts of marine oil spills, contributing to policy, disaster risk reduction, and assessment of social well-being. In Figure 6, economics accounts for 26% of the studied articles within the discipline, with most focusing on assessing the loss of livelihood to the fisherfolk due to oil spills and estimating its monetary value [76]. This sub-discipline has the highest number of published studies due to its timely relevance in understanding the aftermath of disaster. This was followed by interdisciplinary studies (19%), which integrates perspectives from different fields. Combining social and ecological studies, they help identify the effects of oil spills in different aspects [56]. Meanwhile, public health and development studies represent 13% of this discipline, studying the exposure risks of oil spills to human health [56] and analyzing how oil spills impact local development [77]. Studies under public administration (10%) focus on how government agencies respond to spills, sociology (6%) on community resilience, while policy studies assessed the oil spill preparedness of the Southeast Asian region and potential collaboration among industry stakeholders and the government [78].

Lastly, maritime studies and history, each with 3% distribution in the discipline, studied the volume of oil spills in seas with high maritime traffic and the establishment of oil fields [37]. Social sciences bridge the gap between ecological and real-world applications by emphasizing social, economic, and political dynamics. Filling in the gaps in studies would give a more holistic view of mitigating impacts from this man-made disaster.

3.9. Oil Spills Caused by Marine Vessels

The primary source of oil spills reported in the Philippines was predominantly from vessels [12]. The M/T Solar 1 oil tanker from the 2006 Guimaras oil spill was the most frequently mentioned marine vessel in published studies from 2008 to 2024 (Figure 7). The M/T Solar 1 oil spill, which happened in 2006, received significant attention as it has been described as one of the worst in Philippine history [79]. The spill caused significant damage to the environment, harming marine life, coastal communities, and local economies [80]. It has since become a significant case study to understand the impact of oil spills in the Philippines.

Another major spill that happened in 2023, caused by the sinking of the MT Princess Impress in Oriental Mindoro, has drawn significant attention due to its size and the serious risks it posed to marine biodiversity in the Verde Island Passage, a sensitive but vital area for many species [76]. The MV St. Thomas Aquinas ferry disaster has also sparked research interest, raising essential questions about maritime safety, regulations, and passenger welfare [81]. These events highlight the importance of understanding the broader ecological and economic consequences of oil spill pollution in the marine ecosystem. Research on these spills tends to focus more on the bigger, more damaging events like the MT Solar 1 spill [25]. The media coverage, public interest, and political factors also play a big role in shaping which incidents attract more research [82]. The Manila Bay Oil Spill in July 2024, caused by the sinking of the MT Terra Nova near the country’s industrial and economic hub, is another example of an environmental disaster with potential long-term consequences. Unfortunately, the scientific literature assessing the said spill is still limited despite Manila Bay’s importance in the country’s economy.

3.10. The 2006 Guimaras Oil Spill Incident

One of the most catastrophic marine oil spills in Philippine history is the 2006 Guimaras Oil Spill incident. The spill occurred on 11 August 2006 at the coast of Guimaras Island and was caused by the oil tanker M/T Solar I vessel chartered by Petron Corporation from Sunshine Maritime Development Corporation to transport 13,000 barrels (2,067,000 L) of industrial fuel oil from Lamao, Bataan to Zamboanga City [83]. The vessel sank to a depth of 640 m due to rough seas causing a spill of approximately 200,000 L of industrial fuel oil [28]. The spill incident polluted about 200 km of shoreline starting from the Guimaras Island extending to Panay and Negros islands [55], posing risks to marine and coastal ecosystems including mangrove forests, coral reefs, and seagrass beds [34,84,85]. The spill affected 46 barangays in six municipalities. This includes the Nueva Valencia, Sibunag, San Lorenzo and Buenavista in Guimaras and Ajuy and Conception in Iloilo [43,86,87].

The environmental impacts of the spill were extensive and long-lasting. Approximately 650 hectares of mangrove forests, including areas within the Taklong Island National Marine Reserve, were contaminated [28]. Adjacent seagrass meadows also exhibited a notable decline in percent cover, shoot density, and biomass, particularly in areas closest to the spill site, indicating severe physiological stress and habitat degradation [44]. These disturbances to mangroves and seagrasses compromised the ecological integrity of the marine coastal ecosystem, causing cascading effects on biodiversity and ecosystem services [88,89]. Notably, the degradation of the mangrove and seagrass habitats, which serve as critical nursery grounds for various fish species, led to a significant decline in local fish catch, directly affecting the livelihoods of coastal communities dependent on small-scale fisheries [90,91]. However, the loss of income among fishers was not solely due to habitat degradation. The oil spill incident immediately disrupted fishing activities, which were the primary livelihood of approximately 20,000 fishers across the islands of Guimaras, Panay, and Negros, due to health and safety concerns [45,92]. Moreover, the contamination of marine resources reduced consumer demand, and many fishers were compelled to temporarily abandon their livelihoods to participate in cleanup operations [34,86].

These compounding factors resulted in significant socio-economic losses, with estimates of opportunity costs, including foregone income and lost recreational benefits, ranging from PHP 970 million to PHP 1 billion (approximately USD 18–19 million) [34,46]. The local tourism sector also suffered, with projected losses amounting to around PHP 3.7 million (USD 71,400) due to reduced tourist arrivals [93]. Additionally, the Bureau of Fisheries and Aquatic Resources (BFAR) reported that approximately PHP 63 million (USD 1.14 million) worth of marine resources, particularly those in fish cages and pens, were destroyed as a result of the spill [93].

In response to the extent of these economic and environmental damages, various recovery and clean-up initiatives were initiated to alleviate losses and rehabilitate impacted areas. The majority of the recovery efforts occurred in 2006, where an intensive clean-up was conducted for 5 months and lasted for a year after the spill [94]. It was reported that in 2006, there were about 9000 L of oil recovered by a high-tech deep-sea operation using Remotely Operated Vehicles (ROVs) [77]. However, there was no documentation, records, or studies on the amount of oil recovered from the clean-up efforts conducted by local and national agencies. Only an estimated 282,000 bags (2100 tons) of natural materials used for the spill booms and recovered oil were documented [28]. This clean-up was followed by a small-scale recovery operation in 2007 [95]. From 2007 onwards, there were no reports or articles that were publicly documented on oil spill clean-up recovery since the focus of national and local agencies was diverted into recoveries and rehabilitation of the affected ecosystems and livelihoods [52,77,80]. Despite the clean-up recovery efforts in 2006 and 2007, there is still a significant portion of the estimated liters of oil that remained uncollected or unrecorded. These gaps highlight the need for future studies on tracking the fate of this remaining oil, and whether it still persists in our environment or has been gradually degraded over time.

3.11. Philippine Oil Spill Response

The 2006 Guimaras oil spill response was slow and lacked coordination [77,95]. The Philippine Coast Guard used improvised materials like banana leaves and rice straw to contain the oil [28]. There were no advanced tools or tracking systems, which allowed the oil to spread and damage coral reefs and mangroves [12,34]. During this time, aside from the response managed by Philippine National Oil Company, government agencies, academic institutions, and private contractors faced challenges in controlling and cleaning up the oil spill [77,96].

Several international experts helped the Philippines respond to the oil spill. A U.S. team, including members from the U.S. Coast Guard and NOAA, worked in the spill area for three weeks, giving advice and technical support to the local responders [28]. In addition, Japan sent a disaster relief expert team to Guimaras to assess the damage and support the cleanup efforts [97], demonstrating the extent to which the Philippines depended on international support at the time.

Over the years, the country has evolved its oil spill response framework, particularly after the incident in Guimaras. This event revealed severe gaps in preparedness and response capacity, prompting comprehensive reforms in national policy and strategy [98]. Following the Solar 1 disaster, the Philippine government revised and promulgated the National Oil Spill Contingency Plan (NOSCP) in 2008 to create a structured response protocol for oil spill incidents [99]. The Philippine Coast Guard (PCG), through its Marine Environmental Protection Command (MEPCOM) and National Operations Center for Oil Pollution (NOCOP), was designated as the lead agency for managing marine pollution [100]. The NOSCP outlines a three-tier response framework: Tier 1 (handled by the polluter), Tier 2 (regional PCG command), and Tier 3 (national-level response under the NOSCP). The creation of the Oil Pollution Management Fund (OPMF) in 2007 was another critical reform [101]. Administered by the PCG, this fund provides financial support for cleanup and compensation in the event of significant spills, mitigating reliance on external aid.

Recent incidents such as the 2023 Oriental Mindoro spill and the 2024 MT Terra Nova spill demonstrate measurable progress. Although improvised booms were still utilized [102], the PCG’s use of satellite tracking, real-time coordination platforms like IORIS [103], and inter-agency collaboration significantly improved response outcomes, including recovery rates [104].

Despite these structural advances, response operations face significant challenges. Natural factors such as strong monsoons, variable wave conditions, and complex coastal geomorphology hinder containment and cleanup efforts [12]. Changes in the composition and physical properties of oil during weathering are also important for guiding oil spill response, evaluating environmental damage, and their effects [105,106]. In addition, there are limitations in dispersant-use waste disposal logistics and trained manpower, and scientific modeling for tropical marine conditions remains underdeveloped, which constrain oil spill response effectiveness.

3.12. Climatic and Coastal Factors

The Philippines has two main monsoon seasons, the Southwest Monsoon (Habagat) and the Northeast Monsoon (Amihan) [107]. During Habagat, strong winds and waves push oil quickly toward shorelines. This happened in the 2006 Guimaras spill and again in the 2024 Bataan spill [104]. Enhanced by the Southwest Monsoon and Typhoon Carina, MT Terra Nova sank near the coast of Lamao Point in Limay, Bataan on 25 July 2024, making it harder to use equipment like booms and skimmers for cleanup [108]. Amihan brings drier weather and cooler temperatures, with winds that push oil away from the coast [107]. This can delay the oil from reaching shore but also makes it harder to track, as it spreads over a wider area [12]. The cleanup process is made more difficult by strong ocean currents, rough waves, and the varied shapes of coastlines [12,52]. Coastlines with mangroves and muddy, low-oxygen soils can hold oil for a long time, as seen in Guimaras [34,77]. Meanwhile, rocky shorelines are more likely to be cleaned naturally by wave action [28]. These natural conditions affect how oil spreads, how long it stays in one place, and which cleanup methods are effective [109]. As climate change intensifies the frequency and scale of extreme weather [110], adapting to environmental variability will be critical for the Philippines’ preparedness and long-term coastal protection.

4. Research Gaps

4.1. Chemistry and Analytical Techniques

When crude oil is spilled into the open sea, it quickly spreads in the surface water as a thin film, with its thickness depending on the wind or wave current’s strength [111,112]. The way oil spreads and changes after being spilled into the sea depends on sunlight, temperature, and the location of the spill, as different groups of hydrocarbons behave differently under these conditions [79,113,114,115]. Oil weathering is a process by which oil is transformed as it passes through different phases. Typically, oil can be broken down by degraders found in nature, such as microorganisms [105,115,116]. Oil biodegradation is also influenced by environmental factors, such as oxygen, salinity, oil type, oil concentration, and others [117,118]. In the case of a large oil spill, dispersants are often used to break down massive amounts of oil that do not readily biodegrade. However, weathering processes can potentially affect the application of dispersants, as it is a key process in removing light crude oils [105]. Ultraviolet radiation from hydrocarbons can also affect the microbial structure in the marine ecosystem [119]. When an oil spill spreads, it can be exposed to the sun’s harmful rays, which can decrease bacterial diversity and inhibit the performance of biodegraders [115].

However, studies on the fate of oil (as illustrated in Figure 8) after exposure to sunlight under Philippine conditions remain limited in the realm of the published literature on oil spill research. Specifically, the study of oil metabolites and their degradation in different environmental compartments, such as mangrove sediments, beaches, coastal waters, and seagrass beds, is notably lacking. There is a gap in our understanding of which hydrocarbons are effectively degraded in these diverse environments. Furthermore, Sombito et al. (2009) [41] confirmed the presence of petroleum hydrocarbon-degrading bacteria in some affected areas in Guimaras. However, the analysis of bacteria existing in tarballs, a common consequence of oil spills in the environment [105], is also an area that has not received adequate attention and further study. In addition, the examination of residual hydrocarbons within tarballs remains unexplored. This study direction can be undertaken in the Philippine environment due to the country’s tropical climate. Currently, there are no studies on the role of dispersants on the fate of marine oil and its interaction with organisms including phytoplankton, zooplankton, microorganisms, and other macroorganisms. The effect of intense solar radiation on the fate of the oil and the impacts on the environment are relatively unknown under ambient conditions. Filling these gaps would significantly contribute to a comprehensive understanding of the ecological impacts and recovery processes following oil spills in the Philippine context.

Chemical analysis techniques are crucial in oil analysis research. It helps to understand the amount and composition of chemical substances and materials. Although some of the studies in the Philippines use gas chromatography-mass spectrometry for the chemical analysis of oil [55], biomarker fingerprinting to trace the source of the oil [120] is limited. Pyrolysis GC with mass spectrometry (MS), a rapid but thorough technique for analyzing oil residues, has been applied recently for this analysis [30]. GC tandem with two MS (GC-MS/MS) was applied to quantify hydrocarbons in oil residues, unveiling several chemical compounds [121]. (GC/APCI-MS/MS) was utilized to fingerprint crude oil and environmental samples from the largest accidental marine oil spill in history (the Macondo oil spill in the Gulf of Mexico, 2010) [67], unravelling significant compounds in tarball samples. To understand the evolution of oil chemistry in oil spill events in a tropical archipelago like the Philippines, applying these techniques could provide more insights into the fingerprint of oil residues and their potential impact as they travel to different environmental compartments and come into contact with different organisms.

4.2. Biology

Bacteria produce extracellular polymeric substances (EPS) and their ability to break down oil in surface water was reported following the 2010 Deepwater Horizon oil spill [119]. The presence of oil and dispersants significantly boosted EPS production in oil-degrading bacteria. Out of 100 bacterial isolates, 9 bacterial isolates were identified as belonging to genera like Alteromonas, Thalassospira, Aestuariibacter, and Escherichia. However, the role of EPS and marine snow in the behavior of oil in Philippine waters has yet to be explored. Based on the collected literature, only the distribution and the changes in the polycyclic aromatic hydrocarbons (PAHs) in shellfish [55] were investigated as an effect of the Guimaras oil spill, showing that the total PAHs in shellfish were eightfold higher in comparison to before the oil spill. Thus, future research should also focus on investigating the relationship between EPS production and oil-degrading bacteria to further the knowledge of oil degradation in the marine environment and to understand the role of marine snow in particle transport across the water column to develop strategies for mitigating the impacts of oil spills.

Moreover, the response of deep-sea sediment bacteria in the nGoM to light Louisiana sweet crude oil, in terms of community composition and hydrocarbon metabolism, was also studied by Gemmell et al. [68]. The result shows that PAHs were readily degraded when the oil was added, but alkane degradation occurred more slowly. This shows that bacteria can influence the degradation of hydrocarbons, based on changes in oil composition. However, in the Philippines, we lack similar studies on how they impact the seafloor, the ecosystem surrounding the spill, the bacterial communities in such environments, and the associated flora and fauna. Many spills such as the Solar I or Guimaras oil spill and Mindoro Oil Spill released from deepwater or the bottom of the ocean, and we do not have studies on how environmental factors such as nutrients, temperature, sunlight, oxygen, type of oil, oil concentration, pressure, shoreline energy, pH, bacterial community, mineral particles, and salinity [118] could impact the biodegradation of these spills in the Philippine setting. In addition, we do not have any published studies that explore the dark, cold, high-pressure and challenging environments in our ocean that will help broaden our understanding of the factors affecting the biodegradation of spilled oil in marine environments.

The studies on oil spills in the Philippines focus more on marine events, and no studies have been recorded on terrestrial oil spills. There is a lack of studies on oil spills in rivers, lakes, and on land. Oil spills affect soil and vegetation, and affect soil properties and the presence of heavy metals [122]. Oil spills and heavy metals make the soil more acidic and reduce key nutrients like organic carbon and minerals. This also affects soil structure, texture, pH, and microbial activity, which can result in lower crop yields. However, similar research has not been undertaken in the land areas of the Philippines. More studies are needed to understand how oil spills affect soil, spread pollution, and impact ecosystems and human health. This research could help policymakers and farmers reduce crop losses, improve soil recovery, and protect food safety in affected areas.

Furthermore, knowing how local microbes in Philippine marine environments respond to oil contamination is important. This includes looking at microbial diversity, their ability to break down oil, how environmental factors affect this degradation process, and the impact of oil dispersants in the marine ecosystem. Understanding how these microbes degrade oil, especially in deep-sea sediments, is key to assessing the natural strength of marine ecosystems and creating effective oil spill response strategies for the Philippines. This will aid response groups to estimate the fate of oil in the open waters in the event of future spills in the country’s very rich archipelagic waters.

4.3. Social Sciences

Social science research often looks at the wide effects of oil spills on people’s health, livelihoods, and economy. However, a significant gap remains in understanding how local communities in the Philippines perceive and respond to oil spills, particularly regarding their knowledge, attitudes, and practices (KAP). Conducting a KAP survey is important to understand what people know, how they feel, and how they act when oil spills happen. This data is essential for designing effective strategies that drive behavior change, empower communities, and help stakeholders develop targeted, evidence-based solutions to address specific challenges [123]. Without KAP studies on oil spills in the Philippines, we lack insight into the local community’s perspectives on risks and impacts, which hinders their participation in decision-making, preparation, and response efforts. Additionally, future research should explore how factors such as age, gender, occupation, and cultural background shape disaster responses, as no existing studies have examined these influences in the context of oil spills.

Oil spills are not just environmental disasters. They are catastrophes with far-reaching consequences for the entire economy. In the study of Lizada et al. (2009) [124], they estimated the damage of the Solar I oil spill on mangroves in Guimaras. The result shows that the losses based on a tree mortality of 0.97 hectares are equivalent to PHP 92,255 for the initial year. Potential losses range from PHP 3.99 million to PHP 6.6 million under the assumed best-case scenario of 6.45 hectares or 1% damage of mangrove cover, and PHP 59.8 million to PHP 98.7 million under the worst-case assumption of 15% damage. On the other hand, the study of Lizada et al. (2011) [46] shows that the indicative direct use value of the environmental damages due to the oil spill in Guimaras ranged from about PHP 970 million to PHP 1 billion. These represent the income lost due to the inability to engage in livelihood and recreational activities by the residents of Guimaras Island. Concerning this, further studies should focus on the impact of other oil spill events, such as the Mindoro Oil Spill, and how they could affect the entire economy and the livelihood of the people in the long run. Since there are no similar studies to this, future studies will help us to understand the overall economic impact caused by the oil spill.

4.4. Remediation of Spilled Oil

In the Philippines, although there are studies on oil spill recovery technologies through bioremediation using plant fibers of Miscanthus sinensis (Silver Grass) [125], Oryza sativa [126], and Ananas bracteatus [127], there is still a gap in studying oil spill recovery technologies using the physical, chemical, and in situ burning to efficiently treat and recover from oil spills and oil slicks, helping promote environmental cleanup. In the study of Hung et al. (2019) [128] in Vietnam, they presented the use of technologies such as booms and skimmers for physical dispersants and solidifiers for chemicals, and presented the in situ burning method as the safest solution for oil spills and oil slick remediation.

The Oriental Mindoro Oil Spill in the Philippines created an opportunity for studies to use natural resources to develop technology for oil spill remediation. Such a study involves using bio-based polyurethane foam made from coconut oil, which can absorb oil and is reusable. This foam, called “Cocoflexsorb”, developed at NICER (Niche Centers in the Regions for R&D) Center for Sustainable Polymers (CSP), Mindanao State University–Iligan Institute of Technology (MSU-IIT), is said to absorb different oil types such as light, vegetable, kerosene, engine, and bunker oil with superior capacity [129]. However, while the foam shows the absorbance of crude oil, much of the oil spilled had been weathered and had to be scooped manually. Thus, further studies are still needed to improve this technology to absorb large amounts of weathered oil [130]. Despite these advancements, we are still falling behind in effectively addressing oil spills and their aftermath. This lack of remediation capabilities poses environmental risks and economic and social challenges that demand urgent attention and action.

5. Conclusions and Future Perspectives

This article comprehensively reviewed the literature on oil spills in the Philippines over 40 years, from 1980 to 2024. The results show that published studies peaked around large oil spills, such as the catastrophic 2006 Guimaras oil spill, with a predominant focus on assessing the biological and socio-economic impacts. However, medium and small oil spills have received less attention, even though their cumulative effects can be significant and can spread over a large area. Mangroves are the most studied organisms, likely due to their importance in coastal ecosystems and local economies. However, there is a significant gap in research regarding the utilization of the country’s natural resources (plants and microorganisms) for oil spill management. More research is also needed that combines various disciplines, such as biology, social sciences, engineering, chemistry, toxicology, and biotechnology. These interdisciplinary approaches are essential for developing a sustainable and effective science-based solution to the complex challenges of oil spills.

Overall, the current research on oil spills in the Philippines reveals apparent gaps that need urgent attention. While researchers have tried to understand and reduce the impacts of oil spills, many key areas remain underexplored. This review highlights the need for more in-depth studies, particularly on the 2023 Mindoro Oil Spill and the 2024 Manila Bay Oil Spill, as well as on minor oil spills, to better understand the fate of spilled oil and its long-term effects, so that researchers can develop better ways to manage future spills. The environmental behavior of oil and its impacts on the natural ecosystem, the economy, and society need to be systematically studied (Figure 9). By addressing these gaps and fostering interdisciplinary collaboration, future research can enhance oil spill preparedness, improve the response strategies, and strengthen community resilience across the Philippines, an archipelago with one of the longest coastlines in the world.