PhD adventures in the Philippines: coring around Lake Bulusan 

The lowland rainforests of south-east Asia are renowned for their exceptional biodiversity but are among the most threatened ecosystems on Earth. Mass flowering events in lowland tropical rainforests are generally triggered by environmental cues, particularly climatic changes such as drought or temperature fluctuations. However, there is increasing evidence that nutrient availability, particularly phosphorus, may also play a critical role in regulating these events and, through them, forest development. Phosphorus is an essential macronutrient for plant growth and productivity, but it is often a limited nutrient in tropical rainforest soils, which are highly weathered and nutrient poor.

In lakes, particles from a diverse range of inorganic, organic and biogenic detritus and volcanic ash can settle through the water column and onto the lake floor. Over time, layers of particles accumulate that can contain a wealth of information about the past environmental conditions in the lake and its watershed. My research aims to answer fundamental questions about how concentrations of essential nutrients, particularly phosphorus, derived from volcanic ash affect tropical forest composition, structure and flowering dynamics. In May 2025, I conducted a two-week fieldtrip to collect lake sediment cores and fresh soil and water samples at the Bulusan Volcano Natural Park, Sorsogon Province, Philippines.  

Lake Bulusan

Bulusan Volcano Natural Park is located in Sorsogon Province, Philippines, and stretches over 3673 hectares. It was first designated as a National Park in 1935. It consists of mixed dipterocarp forests, giant ferns and other plant species including ground orchids. Lake Bulusan itself is a 0.28 km² lake lying at the foothills of Mt Bulusan and has no inlets or outlets; instead it comprises a closed system fed primarily by precipitation and groundwater. The lake’s location and its ability to catch volcanic ash from volcanic eruptions over time makes it the perfect study site for my PhD project.

Fieldtrip

Conducting the fieldwork in the Philippines was not without challenges. Firstly, all necessary agreements and permits needed to be in place beforehand; this process was carried out during the first 15 months of the PhD project. In the week leading up to the trip, the volcano, which is located close to the fieldtrip site, erupted briefly and put the whole fieldtrip in jeopardy. Luckily the eruption did not cause any danger to the public or surrounding areas.

Our first stop was Manila, where the correct wildlife permit was provided by the Department of the Environment and Natural Resources — Biodiversity Management Bureau (DENR-BMB) to allow us to collect the samples. We then travelled down to Sorsogon Province, where we met up with our local collaborator Dr Ellen Funesto (University of the Philippines — Cebu) and lake coring expert Dr Wes Farnsworth (University of Iceland). After a day of recovery, the team headed into the Bulusan Volcano Natural Park to access Lake Bulusan for lake coring and sampling activities.

The lake coring was done on a semi-luxury 4 × 3 m raft equipped with a table to sit at and an umbrella for shade, and we were assisted by six local fishermen who were all interested in the research and lake coring processes. Two local guides also helped the team navigate around the lake and through the forest, finding the best spots to collect fresh soil samples from the forest surrounding the lake.

Learning about the culture

As we collected samples, we also had time to enjoy some of the Filipino cuisine. With recommendations from our local collaborator, we tasted a range of dishes that are must-tries (at least in our opinion!) when visiting the Philippines, ranging from local fish bangus, through pork sisig to chicken teriyaki from the local chicken shop.

Additionally, the Philippines’ landscape offers scenery unlike anything I have seen before:  beautiful beaches, waterfalls, volcanoes and forest. Beyond the incredible food and stunning environment, the local people in the rural parts of the Philippines are some of the friendliest people I have met. They were welcoming and those who joined us on site to collect samples brought joy to the fieldwork at the natural park.

Next steps

The samples are now back at the BGS headquarters in Keyworth and, over the next few months, we plan to explore the palaeo-nutrient histories hidden within the lake sediments, using core scanning alongside geochemical and stable isotope methods. In addition, there will be a trip to the University of Copenhagen, Denmark, later this year to extract ancient environmental DNA, which will help us understand how nutrient inputs from volcanic ash affect the tropical rainforest system.

Thanks

Thanks to our collaborators Dr Ellen Funesto and Dr Wes Farnsworth; without your assistance and expertise to the team the fieldwork would not have been possible. A special thanks also goes to Eleanor Lacsi De La Cruz from the Provincial Environment and Natural Resources Office (PENRO), who was on site all day and worked hard in both helping coring and securing all the necessary permits to export the samples back to Keyworth.

The work would not have been possible without the support of a huge number of people, especially the DENR-BMB, PENRO and DENR regional offices who issued the permits and have supported the project over the last two years.

About the author

Christopher Bengt is a second-year PhD student enrolled at Lancaster University. His PhD is funded through the Envision Doctoral Training Partnership and the BGS University Funding Initiative.