Top-down Control on Sponges in the Philippines

Anjali Arutchelvam • Oct 02, 2019

CCC support an MSc Thesis that looks at the evidence of top-down control on sponges by vertebrate predators in the Philippine reef system!

The thesis, “No Evidence of Top-Down Control on Sponges by Vertebrate Predators in a Philippine Reef System”, produced by Sara Basso MSc, University of Essex, and supported by CCC, aims to comprehend if small-scaled Marine Protected Areas (MPA) supply an increased spongivore (an animal adapted to feeding on sponges) abundance which would help prevent a shift in the dominant benthic community from corals to sponge.

This paper was developed by Sara for her Msc in Tropical Marine Biology at the University of Essex in 2018.

It is estimated that the total area of coral reefs worldwide has decreased by 19%. Sponges contribute the highest benthic biomass in coral reefs, after scleractinian corals. Although they tend to be in competition with scleractinian corals for substrate, sponges are relevant benthic organisms that perform important roles in coral reefs and in many marine ecosystems. This study assesses and analyses: 1. If small no-take areas maintain increased spongivore abundance; 2. Sponge-coral interactions and growth form assemblages of sponges in an overfished and protected site, in order to evaluate the effect of spongivore in preventing out-competition of corals by sponges; 3. Coral and sponge cover across four reefs, in order to compare their abundances with corals in sites where spongivores have varying abundance levels.

The study was conducted in Sogod Bay in the province of Southern Leyte, Philippines. The reefs surveyed were situated in the barangays of Napantao, Bahay, Cagbungalon, Catig, Tabugon and Gudan. The reefs in Napantao, Catig, Bahay and Tabugon are considered protected as they have established MPAs. As control sites forNapantao and Catig, transects were placed outside of MPAs; whereas Cagbungalon and Gudan were used as control sites for Bahay and Tabugon respectively.

The surveys at all the sites were performed using SCUBA and were conducted at both 6 m and 12 m depths. The data for the spongivore abundance and substrate type were conducted with an augmented Reef Check protocol; whereas the fish data were collected within a 5 m belt transect along 20 m of each replicate of the 100 m transect. Substrate data were recorded along the same replicates of the point-intercept transect at intervals of 0.5 m.

To positively avoid the exclusion of fish that potentially feed on sponges, spongivores were considered at the family level. A deepened review of the literature was performed to identify the spongivore families for the Indo-Pacific region. Eight families (Acanthuridae, Chaetodontidae, Nemipteridae, Pomacanthidae, Siganidae, Scaridae, Tetraodontidae and Zanclidae) were selected for this study. To avoid bias of fish species that were included that do not feed on sponges, the same analyses were repeated considering just Pomacanthidae. From 2017-2018, the mean spongivore abundance was 42.33 inside the MPA and 17.20 outside the MPA; with the lowest value being in Gudan at 16.19 and the highest value being in Napantao at 59.33.

At the survey site in Catig, a total of 2, 125 sponges were counted inside the MPA and 1,791 were counted outside. Encrusting sponges were the most abundant growth form, accounting for 61.67% and 55.90% of the total composition for inside and outside the MPA respectively. nMDS analyses showed the morphological assemblages did not differ between the protected and non-protected area of Catig when all the spongivore families were considered but when only the Pomacanthidae were considered, it showed that they had an influence on sponge morphology between the two sites.

The comparison of sponge abundances with spongivore abundances across the four MPAs and likewise overfished sites showed no relationship between spongivore and sponge abundance. This shows that there is no evidence of top-down control by sponge vertebrate predators along the fringing reefs in Sogod Bay. The absence of sponge abundance control by predators in all the survey sites may explain the lack of diverse morphological assemblages in Catig. In the surveyed reefs, the visibility was often less than 20 m and a moderate current was recorded which could have had an impact on sponge growth as sponges are negatively affected by increasingly turbid environments, particularly in proximity with the coast.

In summary, this thesis demonstrates that there is still no clear definition if sponges are top-down controlled by the presence of their predators or bottom-up regulated by nutrient availability. This paper also shows the possible efficacy of forbidding any fishing practice in incrementing fish abundance, underlining the relevance and importance of no-take areas in maintaining adequate fish abundances.



If you would like more information about the study, you can contact Sara at sara.basso1994@gmail.com or alternatively, our Head of Science at headofscience@coralcay.org

by Harriet Tyley 15 Dec, 2020
We would love to learn some more about you, how you found our Scholarship Programme and how it has helped you achieve your goals in the Philippines since graduating! 1) What year did you join the Scholarship Programme? I joined the Coral Cay team in Napantao, Southern Leyte from August to September 2016. In June 2017, I also came back to Coral Cay to help in survey dives for three weeks. Glad to have been given the chance to stay in the base twice with two different groups! 2) Could you please tell us a bit more about yourself? For example, what are your interests, where abouts in the Philippines are you from? etc. I am Carm, a development professional working in the intersection of environmental conservation and human development. I currently work for the Department of Agriculture, helping run projects that aim to improve protected area management in selected key biodiversity sites, at the same time, improve the socio-economic condition in the nearby coastal communities. Aggregation of whalesharks and manta rays are common in where I am currently based so it is a really exciting place to be! I am a Divemaster candidate looking to go “Pro” and I’m also in graduate school studying marine affairs. I love to cycle, hike, climb, fish, camp, discover new places, volunteer in causes, read non-fiction and watch silly rom-coms in my other time.
by Harriet Tyley 07 Dec, 2020
We would love to learn some more about you, how you found our Scholarship Programme and how it has helped you achieve your goals in the Philippines since graduating! What year did you join the Scholarship Programme? I was a Filipino scholar in August of 2013. Could you please tell us a bit more about yourself? For example, what are your interests, whereabouts in the Philippines are you from? etc. My name is Ara and I was born and raised in Manila. I grew up in a family of entrepreneurs and weekends would be spent in my grandparents house talking about business over lunch. The fast-paced life of the city was all I ever knew. In University, I took up Communication Technology Management and Minored in Marketing because I also wanted to start my own business someday. As I grew older, I had a constant need to get out of Manila and just travel. When I was not working, I would be exploring some remote island in the Philippines or visiting neighboring countries in Asia. In the past 15 years, I have held job titles like photographer, store manager, photo editor, production manager, operations manager, jewelry maker, mug maker, and now a business owner. Despite the frequent changes in job descriptions and careers, being a traveler, and now a scuba diver, are the only things that have remained constant in my life. What was it about Coral Cay Conservation that made you decide to apply for the scholarship programme? I learned about Coral Cay Conservation from one of my best friend and travel buddy, Jem. One day we were discussing where we could go next and she told me that she would not be available on certain dates because she got accepted as a dive scholar in Coral Cay Conservation. She told me that will be gone for a month doing reef surveys in Napantao, Southern Leyte. I had never heard of Coral Cay Conservation nor of a place called Napantao until that moment, so this peaked my interest even more. One month learning about the conservation and diving almost everyday for free? It seemed to good to be true! The more I read about the scholarship programme, the more I wanted to join. I have always wanted to learn scuba diving but kept pushing it down my bucket list. The idea of learning how to scuba dive for free in my own country was really a no-brainer for an ocean-lover like myself. I knew right away I couldn’t pass up on this opportunity.
by Harriet Tyley 01 Dec, 2020
Hi Daff, we would love to learn some more about you, how you found our Scholarship Programme and how it has helped you achieve your goals in the Philippines since graduating! 1) What year did you join the Scholarship Programme? I joined the CCC Scholarship Program in November of 2016. I learned about the program from a few acquaintances. It took me at least a year to finally apply and see where it takes me. During that time, I was working with the Department of Tourism. I had a good number of projects that involved eco-tourism, fisheries management, and marine conservation, which kind of made me decide to try and apply. It only took a couple of months for the head office to get me on board and informed me that I was accepted! It was a long trip to Napantao but I enjoyed it since it was my first time in that part of the country. When I arrived, I was met by Claire (field base manager), and of course, the ever-welcoming Coral and Shrimp! 2) Could you please tell us a bit more about yourself? For example, what are your interests, where in the Philippines are you from? etc. I grew up in a small town in Iloilo. We were living fairly in the middle of farmlands and the sea. As a result, most of the people in my place are either farmers or fishermen. My interest in the environment started way back when I was a kid and eventually became more involved as I got my education. I spent two years in a fisheries school where I studied during the first half of my high school. I eventually got into the outdoor movement, which brought me to mountain and cave explorations. It made me appreciate the world and the things around it more. It also gave me a better perspective on how we can help and do better in protecting the environment. During my professional career, I first got into research where I had the opportunity to work with fishing communities. There, I was able to experience first-hand how our oceans are under threat due to climate change and human activities.
by Harriet Tyley 24 Nov, 2020
We would love to learn some more about you, how you found our Scholarship Programme and how it has helped you achieve your goals in the Philippines since graduating! 1) What year did you join the Scholarship Programme? I joined Coral Cay Conservation’s Scholarship Program this year, 2020, specifically last March. And it’s probably the best thing that’s ever happened to me. I will forever thank myself for applying for it because it was such a beautiful opportunity. 2) Could you please tell us a bit more about yourself? For example, what are your interests, where abouts in the Philippines are you from? etc. Well, my name is Easter and that’s because I was born on Easter Sunday. I live in the small town of Hilongos Leyte, just two or more hours away from Southern Leyte. And just as how every other kid that grew up in a province with the beach just a walk away, I, too, grew up loving it. I remember just being in the water and finding comfort in it. I started taking swimming classes in Cebu City every summer I get the chance too, and I remember feeling so new to the feel of the pool, my swimming cap, and goggles. I never really wore these in the beach, my siblings and I would literally swim with or without goggles with our eyes wide open. I competed twice and didn’t do badly for a beginner. The city has a special spot in my heart because, before coming to Coral Cay, I worked at Turtle’s Nest Book Café & Gallery in Lahug. I worked behind the bar there and made cheap coffee while entertaining locals, regulars, and tourists. I guess I just love amusing people and learning about them. 3) What was it about Coral Cay Conservation that made you decide to apply for the scholarship programme? I found out about Coral Cay Conservation when I googled environmental conservation organizations near me. At the time, I was still in school but had already decided on taking a different path. I’ve always wanted to learn more about conservation, but the expenses in volunteering camps always hindered me until I saw Coral Cay Conservation’s Scholarship Program. I read what it included and what it did not and got excited about learning about corals! I’m not going to lie but during this time I didn’t know corals are animals, so, that got me so hooked and I just started reading about it! And since this was CCC’s specialty, I decided to apply. 4) What was the most exciting part of your scholarship placement? And what were your favourite moments? The most exciting part of the scholarship was scuba diving. I had only ever seen it in movies, the Discovery Channel or on National Geographic. I never thought I would be ever be learning about it and doing scuba diving myself. Also, because it made me see a part of the underwater world that I only ever hear in the news, see in movies, and read in books. And I have so many favorite moments with CCC, a few would be the pointy dives, dinner talks, Sundays when we’re supposed to be dry but we’d still choose to snorkel to see more of what’s under, and, honestly, just the whole of it! I have never been in a place with so much understanding and learning and good food and people! 5) What would you say to people thinking of applying to Coral Cay Conservations scholarship programme? Any words of wisdom or advice!? To anyone who’s planning to apply for Coral Cay Conservation’s Scholarship Program, please do. You’re going to learn a whole lot (more) about the ocean, the reefs, our planet, people and culture from different corners of the world, and butterflyfish! Do it. It’s going to be worth it! 6) Since finishing your scholarship with Coral Cay Conservation, where has life taken you? How have the skills and experience received from the scholarship benefited you since graduating? Given the current situation now, with COVID-19 and the halt to almost everything, I haven’t really done much since graduating. But I now have more confidence about the path I want to take and am in. With this, I revamped the organization—Kuntahay—that I started in September last year. Kuntahay is a Visayan term for “imagine” and with and through it, I want people to see the beauty of both under and above water. It also follows the conscious and careful lifestyle, hoping to encourage more people to be in the fight against climate change and systemic oppression. And the skills and experience that I have acquired in CCC have truly benefited me in some ways. I can now identify fishes, corals, coral bleaching and diseases! And when my friends and I go snorkeling in the neighboring town that has a dying/growing reef in it, I would share with them the exciting parts! But right now, I’m looking forward to enrolling to Marine Biology next school year, and it’s such a relief to be looking forward to something I know I actually want to pursue because I’ve been in and out of school for a while now, due to not having a clear idea of where I really want to go. But ever since my time in CCC, I’ve been introduced to new things and re-introduced to, what I believe I have nearly forgotten about in my years of being in the city, the ocean and its importance.
by Harriet Tyley 03 Nov, 2020
Biodiversity Restoration David Attenborough: A Life On Our Planet, opens our eyes to truths many of us have tried to ignore. Our planet is changing at an accelerated and unprecedented rate, and it is up to us to try and change this uncertain trajectory. Biodiversity loss is considered to be one of the severest threats to our environment, and without action, over half the world’s marine species could be nearing extinction by 2100. The ocean is home to over 90% of the habitable space on our planet, but only about 5% of the worlds ocean and adjacent seas are protected, compared to 12% of the worlds land . 50% of the oxygen on our planet is created in the ocean , by microscopic phytoplankton, which forms the very base of the marine food chain and enables life. The ocean is a critical carbon sink, and the blue carbon locked in our marine habitats may be up to 5 times the amount of carbon stored in tropical forests . And unfortunately, it is thought that between 3 0-35% of global critical marine habitats (seagrass, coral reefs and mangroves) have been destroyed.
by Harriet Tyley 27 Oct, 2020
David Attenborough: A Life On Our Planet, reflects on previous trips to coral reefs, which were once colourful, vibrant, and full of life. When returning to these exact reefs however, he notices a very stark contrast in the corals appearance; they are white. But what is coral bleaching and why is it something that we should be aware of, and increasingly concerned about? What is a coral? For many, corals are a confusing organism: Is it a rock, a plant, or an animal? Corals are marine invertebrates in the class Anthozoa, of the phylum Cnidaria, which also includes jellyfish, hydroids (Portuguese men-of-war), sea anemones and sea fans! Corals are sessile animals, and once their larval stage is complete, are permanently attached to the ocean floor. When we think of a coral, we are not really thinking about an individual coral, but in fact a colony of corals, made up of thousands of individual polyps! In reef-building corals, these soft-tissue polyps secrete a hard-outer skeleton made up of calcium carbonate, which over millions of years creates vast expansive biological structures that can sometimes be seen from space ! Producing and secreting these calcium deposits is energetically costly, so corals have evolved a unique symbiotic relationship with an algae called zooxanthellae. These microscopic algae reside within the coral tissue and create energy via photosynthesis. An incredible 90% of the organic material produced photosynthetically by zooxanthellae can be transferred to the host coral , giving the coral sufficient energy to live, thrive and grow! Why are corals valuable? Coral reefs cover less than 0.1% of the oceans floor but house a staggering 25% of the oceans biodiversity! Corals provide a wealth of eco-system services, acting as nursery habitats for commercially valuable species, providing a source of primary protein for coastal communities, creating a source of income through tourism and recreation, and also protecting coastal areas from storm surges. It is estimated that the economic goods and services provided by coral reefs amount to an annual value of $375 billion! Corals have been around for millions of years and have even survived global mass extinctions, but due to raising ocean temperatures the future of corals is scarily uncertain – and this is largely due to coral bleaching.
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