About the state of health of the Gulf of Thailand (5)

18 Mar
March 18, 2014

In situ simulation of eutrophication and overfishing in a coral reef of Koh Phangan, Thailand

- Effects on sediment surface parameters -

Soureya Becker (MSc.)

the magic shower

Soureya Becker


The Gulf of Thailand is a highly under-investigated area that experiences increases in anthropogenic stressors. Intense coastal development and mass tourism in the Gulf of Thailand result in overfishing and eutrophication. These factors cause uncontrolled proliferation of algae in coral reefs and lead to phase shifts which means a subsequent potential death of reef organisms.

 Our study aims to link predation by the fish community and the inorganic nutrient availability and their effect on the surrounding sediments. Therefore, overfishing (fish exclusion via cage deployment) and eutrophication (controlled addition of fertiliser) were simulated in the patch reef of Mae Haad, located in the Northwest of the island Koh Phangan, a typical bay influenced by tourism and river input. Sediment samples were collected weekly in addition to the assessment of key environmental parameters including background concentrations of inorganic nutrients, fish biomass and diversity, benthic community composition and water movement.

 The results show a significant effect of fish exclusion on the sediment surface cover and the sedimentary chlorophyll a content (as a measure of microphytobenthos) but not on the microbial activity. Unfortunately too little is known about limitations of microphytobenthos, a direct link between fish exclusion and microphytobenthos growth could not be established. Difference in microphyotbenthic growth and microbial activity in response to nutrient input could not be verified in this study.

The photos taken every week of the sediment area in the subplots were  used for comparison of the visible coverage.. Five categories were defined: almost clean sand (1), brownish colouring of the sand (2), appearance of fleshy algae (3), accentuation of the colour and larger distribution of fleshy algae (4) and algae mat (5).

The photos taken every week of the sediment area in the subplots were  used for comparison of the visible coverage.. Five categories were defined: almost clean sand (1), brownish colouring of the sand (2), appearance of fleshy algae (3), accentuation of the colour and larger distribution of fleshy algae (4) and algae mat (5).

The photos taken every week of the sediment area in the subplots were used for comparison of the visible coverage.. Five categories were defined: almost clean sand (1), brownish colouring of the sand (2), appearance of fleshy algae (3), accentuation of the colour and larger distribution of fleshy algae (4) and algae mat (5).

The observed lack of nutrient enrichment effects may indicate that nutrients are already present in high concentrations at the study location. Indeed, own supplementary measurements confirmed that high phosphate concentrations are entering the bay via river input. Mae Haad is a reef already impacted by pollution and fishing.

Pictures of waste water pipes originating from a resort in the north of the bay (A) and of river discharge at the beach (B).

Pictures of waste water pipes originating from a resort in the north of the bay (A) and of river discharge at the beach (B).

Pictures of waste water pipes originating from a resort in the north of the bay (A) and of river discharge at the beach (B).

For future investigation, an understanding of benthic food-web relationships is essential, since it has implications not only for fundamental ecology but also for properly interpreting and predicting the effects of environmental perturbations: effects at one trophic level (fish, invertebrates, or microalgae) could lead to responses at another level. All results suggest that the investigated reef is already highly impacted by eutrophication and overfishing. Regular monitoring and more detailed investigations of site specific and setup properties may sharpen the picture.

This is Matvey (3), the youngest son of Evgeny, "our" videographer on KPG. It will be 7 years before Matvey can dive, but he wants to start now. Because of his dad's whale shark videos. You can help him to see one in 7 years, they're getting a little bit rare...

About the state of health of the Gulf of Thailand (4)

17 Mar
March 17, 2014

Ines Stuhldreier (MSc, PhD candidate)

In 2012 I had the pleasure to spend 4 months on the beautiful island Koh Phangan in the Gulf of Thailand, to enjoy the stunning under-water-world, hang out on tropical beaches, meet awesome people, eat looooots of good Thai food, get cheap massages… oh yeah, and to conduct the fieldwork for my Master thesis.
My supervisor Prof. Christian Wild from the Leibniz Center for Tropical Marine Ecology in Bremen told me about CoreSea and the research some students did the year before (read the blog-posts of Hauke and Susanne). From their results it was visible that the coral reef ecosystems around the island were affected by human influences in comparison to the nearby Marine National Park in terms of fish abundances and live coral cover. We, a group of three students, now were interested to find out how the anthropogenic stressors overfishing and eutrophication can influence the functioning of the coral reefs on Koh Phangan.

How the scientific community looks on their day-off

How the scientific community looks on their day-off


Nutrient source in Mae Haad bay, Koh Phangan

Nutrient source in Mae Haad bay, Koh Phangan

Overfishing is a big problem in South East Asian reefs, and in the Gulf of Thailand in particular, as local communities largely depend on fisheries for food and income. As fisheries management is often inadequate, lots of species are fully fished or overfished. Especially the removal of large algal-grazing fishes decreases reef health, asherbivores (the vegetarians of the fish community) play an important role by limiting the establishment and growth of algal communities (= top-down control) (Green & Bellwood 2009). From the other end of the ‘food chain’, algae are promoted by high nutrient concentrations in the water (= bottom-up control). Additional to natural nutrient concentrations, large amounts are introduced from land. As many coastal communities and hotels in South East Asian lack effective water treatment facilities, wastewater is often discharged untreated into the ocean. This wastewater contains high concentrations of nutrients and act as fertilizer for reef algae. In a nutshell, there is an ongoing competition for space in a reef between corals and algae, and fishing of herbivores as well as the addition of nutrients will tip the balance in favor of algae. There have been numerous studies on the relative importance of the stressors overfishing and eutrophication on coral reefs, but the results are highly variable and depend on region

Top down vs bottom up

Top down vs bottom up

or groups of algae and herbivores. Southeast Asian reefs have hardly been studied in this regard, although they have been classified as the most threatened reefs in the world with overfishing and pollution as major threats (Wilkinson 2008; Burke et al. 2012).
With my Master Thesis I wanted to find out which on is the more important factor influencing reef algae growth on Koh Phangan’s reefs. At the same time, my colleagues Soureya and Pepe looked at responses in sediment parameters and invertebrate recruitment (baby corals, baby worms, …) to the same stressors

Material & Methods

To find out how anthropogenic influences alter these parameters, we constructed colorful set-ups from blue and yellow pipe and equipped them with terracotta tiles serving as settlement ground for algae and invertebrates. We simulated the stressors overfishing and eutrophication in these mini-ecosystems by wrapping some of the frames in fishing net (mesh size 2 cm) to exclude fish, added nutrients by deploying bags with slow-release fertilizer, or applied a combination of both. We deployed our set-ups along the outer reef edge in Mae Haad, our office for the following months.

experimental cage design

experimental cage design

Every week over a period of 12 weeks we sampled tiles from each set-up and sediment from below to analyze them in the CoreSea laboratory. First I incubated the algae settlement tiles in glass jars within coolboxes for an hour in the light as well as in the dark to find out how much oxygen the algal community on it can produce by photosynthesis or use by respiration. After this I took a picture of each tile to later analyze the % cover of different algae growing on the tiles with the help of the software CPCe 4.1. Then I scraped off all the algae from the tiles with a razor blade to collect the algal biomass in little tinfoil packages which we later dried in our self-made solar driven oven (This was honestly the least fun part of the week and I am happy I had help from my colleagues and lots of audiobooks on my computer). The dried algal samples were taken back to Bremen, ground to powder with mortar and pestle and analyzed for organic Carbon and Nitrogen content.
Besides working with tiles we conducted benthic-, fish- and invertebrate-surveys as well as feeding observations on the cages at the study site to evaluate benthic community composition and to quantify the influence of herbivores. As the bay Mae Haad has a little river seeping through the sand into the ocean, we suspected the introduction of nutrients by this source and therefore analyzed water and sediment parameters from 6 stations along a transect from the river to the outer reef edge where our set-ups were located. We measured phosphate concentrations and water as well as sediment chlorophyll a, indicators for eutrophication.

Results & Discussion

Results showed that nutrient enrichment neither influenced algae dry mass, algae cover, organic Carbon, Nitrogen content nor oxygen fluxes. Herbivore exclusion on the other hand had a significant effect on algae dry mass and organic Carbon and resulted in phenotypic differences in algal community. All tiles in all treatments were dominated by small, filamentous turf algae. However, caged tiles showed less dense fouling and 3-4 times taller turf algae compared to dense but very short turf algae on uncaged tiles. From week 7, small individuals of fleshy brown macroalgae were growing on caged tiles. Combined effects of herbivore exclusion and nutrient enrichment were negligible as caging effects dominated all response parameters. Temporal changes were evident in algal cover, dry mass, N and organic C content on settlement tiles, all increasing significantly over time. Whereas biomass and cover was highest in herbivore exclusion treatments in week 10 with a 5 fold increase in algal dry weight compared to control treatments, nutrient enrichment led to highest biomass values in week 12 with a 2 fold increase in algal dry mass compared to controls.

How the scientific community looks on their day-off

Cage installation

Analysis of water and sediment parameters on the river-ocean transect revealed 10-times higher concentrations of phosphate and significantly higher water and sediment chlorophyll a concentrations in the river water. This proves that the river is a source of nutrients and organic material to the bay which likely influences reef functioning. Besides the effect of eutrophication on algae growth, nutrients are a problem for reefs by reducing calcification rates in corals (Ferrier-Pages et al. 2000, Fabricius et al. 2005) and increasing the abundance of microorganisms eroding the reef substrate (Holmes et al. 2000). Accordingly, the observed coral cover of 20 ± 4 % was rather small compared to the majority of reefs in the Indo-Pacific. Although macroalgal cover in the reef was low during the study time (4 ± 6 %), high turf algae cover in the reef (42 ± 6 %) indicated elevated nutrient concentrations in the bay, as these fast growing algae benefit from high nutrient concentrations. The abundance of sea-urchins and fish biomass in Mae Haad (0.002 ± 0.003 ind. and 0.137 ± 0.040 respectively) were low compared to a nearby Marine Protected Area or average values from the Indo-Pacific. This indicates that the reef in Mae Haad already impacted by overfishing.
From the study of similar experiments I expected much larger responses of algae biomass to nutrient enrichment and herbivore exclusion. Whereas in other studies the biomass in caged treatments was elevated 300-fold compared to controls (e.g. Jessen et al. 2013), an increase by 5 fold seems quite small. This effect was due to the fact that even in open control plots, the algal biomass on tiles was comparatively high. Obviously, the herbivorous fish community of Mae Haad was not able to control the establishment of algal communities on the substrate, although they prevented growth of macroalgae on open tiles. Furthermore, the lack of responses to nutrient enrichment suggest that ambient nutrient concentrations already satisfied algal growth so additional supply did not have an effect on algal parameters

the magic shower

the magic shower


Clearly the reef in Mae Haad is already impacted by both overfishing and eutrophication. Effects of herbivore exclusion on algal parameters was larger than effects of nutrient enrichment, which is why I concluded that herbivory is the more important controlling factor of algal growth at the study site. Management plans to improve coral reef health should always focus on the key controls of ecosystem functioning at a local scale. For management plans this would mean to first strengthen the status of Mae Haad as marine protected area and reinforce the existing fishing ban. Additional efforts should be made to reduce the input of nutrients from land via the river.

About the state of health of the Gulf of Thailand (3)

15 Mar
March 15, 2014

As part of my diploma thesis, I joined the CORE-SEA-Team from February to May 2011. Rapidly increasing tourist numbers in the area of the lower Gulf of Thailand, accompanied with water pollution, overexploitation of marine resources and disturbances by dive activities, are expected to influence the composition of coral reefs significantly. Sewage water of hotels and resorts is discharged directly into the ocean, thereby potentially polluting reefs permanently. The increased demand of fish by tourists results in the overfishing of local coral reefs, often accompanied with destructive fishing practices. Moreover, the elevated dive activities, especially around the coral reefs of Koh Tao, are causing long-term disruption in reefs.

Susanne Egli (MSc.)

Susanne Egli (MSc.)

My thesis investigated the changes in species composition of herbivorous reef fishes and sea urchins in disturbed coral reefs as well as their impact on the algae composition. Specifically, I tested the hypothesis that high abundance of tourists causes low occurrence of herbivores in the adjacent coral reefs. The decline of herbivorous fishes and other keystone grazers like sea urchins has been identified as the leading cause of increased algal abundance on reefs, which negatively affects the growth, reproduction, and survivorship of the corals. Six different coral reefs around the islands of Koh Phangan, Koh Tao and the barely populated Ang Thong National Park were surveyed, counting the abundance of all occurring herbivorous fish species and sea urchins along a 50 metres long transect line (UVC Method of Reef Check Program). Additionally, the total number of carnivorous fish species was recorded to analyze differences of total fish abundance between the sites. Based on countings of resorts and bungalows along the beach, sampling sites were classified as under “high”, “intermediate”, and “low” influence of tourists. For more precise information about the present tourist number, hotel owners and workers were interviewed about the actual capacity utilization of the resorts on sampling days. Additionally, people on the beach were counted instantaneous after the actual surveying. To estimate the influence of fishing activities on fish species composition, fishing boats along the sampling bays were counted on survey days.

Additionally, changes of species richness during high season from February to March and low season from April to May were investigated conducting surveys in both seasons on the three study sites of Koh Phangan.

Results showed significantly higher herbivore species richness and total fish abundance in the undisturbed reef of Ang Thong Marine Park than on Koh Phangan or Koh Tao. The stronger frequented island of Koh Tao didn`t reveal significantly lower fish or sea urchin abundances than the less visited Koh Phangan. However, lower frequented study sites on the islands showed significantly higher fish abundances than the tourist influenced sampling bays. Numbers of sea urchins tend to be higher on both islands on study sites with high tourist densities. Significant changes in fish species abundance with the beginning of low season was verifiable in 2 of 3 surveyed coral reefs, whereas sea urchin abundance didn`t change significantly.

Scientific diving in the marine park

Scientific diving in the marine park

These descriptive studies were linked with experimental in situ studies, using cage experiments in order to simulate extreme overfishing and following disappearance of benthic or pelagic herbivory. Different cage designs were used to test the effects of exclusion of occurring herbivores on algae growth. Three replicates of closed, semi-closed and open cage designs were deployed on one study site of Koh Phangan. While the closed cages excluded both the herbivore fishes and sea urchins, the semi-closed ones with an open top were used just to prevent the sea urchins from feeding on the tiles, whereas the fishes could enter the cages from above. The open cages were acting as controls, giving both the fishes and the sea urchins the opportunity to feed on the algae growing on the tiles. Cages were placed in identical water depth of 5m on dead corals or stones in the reef to ensure that living corals were not threatened. Every cage was equipped with 12 tiles, each having a size of 2×2,8 cm. Wire of the cages (mesh size 2,5 cm) was cleaned once a week by a steel brush to avoid overgrowth of the cages and consequential lack of light inside, potentially leading to negative effects on growth on the tiles. Biweekly from March to June, one random tile was removed from each cage to analyze algae growth on it. However, the cage experiments couldn`t reveal clear answers of herbivory effects on algae growth, as some cages were repeatedly destroyed and the survey period was too short for expressive findings.

This study was linked with further analysis of water, sediment and benthic community at identical reefs. Several results of these studies were considered at the interpretation of own results to gain a comprehensive data set about the condition of surveyed coral reefs.IMG_3148

Susanne Egli


The biodiversity puzzle

14 Mar
March 14, 2014

Core Sea life has been insanely cool the last couple of days, because we’ve been going out and diving with the Department of Marine and Coastal Resources, the Thai government organization that monitors the Gulf.

They are a very kind and smiley bunch. It’s funny, because the first day we worked with them, they were really impressed with how much Thai Hektor could speak, but by the second day they were laughing about how bad the Thai he could speak was. Hektor told us he was happy though, because being made fun of is the first step to being accepted. Very wise, that man.

3We took the Spirit of Gaia and sailed our way out into outer Chaloklum Bay. Maddi, Lydia, Freddy, and I watched as the DMCR people pulled out all of these sciencey tools. One woman had a container connected to a long skein of rope, which was connected to a machine that displayed the depth, salinity, PH, temperature, and oxygen levels of the water at whatever level the container was at. Another two women were hauling this big silver contraption that looked like a miniature bulldozer scooper out of the water. They then opened the jaws, and tons of grey mucky sludge from the sea spattered into a round green tub. Bits of projects and measurements and data were flying all around the back of the boat, and we watched, fascinated. Real science!

After they’d finished all of the measurements, the boat went over to Haad Yao, a side of the island I’d never been on before. We assembled our dive gear and placed our BCD’s into a grey zodiac, which they then drove out a little ways from the boat. We struggled into our kits and threw ourselves off the small vessel. We descended along a transact that the DMCR had laid out, and while they took pictures every meter, we followed along  behind them counting and tallying fish on our slates. The visibility was a good 5 or a poor 10, much better than the day before.

After the transect finished, Maddi and I decided to stay under for longer. We cruised the reef, pointing out cool creatures and enjoying the freedom of the dive.

1Back on the boat, I dismantled my gear quickly and packed it all away. I was filled with an unshakeable need to flip off of the boat. You can take the girl out of gymnastics, but you can’t take the gymnastics out of the girl. As I ran up the ladder to the top deck, one of the DMCR men grabbed the long string attached to the zipper of my wetsuit, so when I climbed up, the wetsuit unzipped completely. They all laughed and gave me big teasing smiles.

On the top of the boat, I ducked under the safety railing so I was standing on the narrow edge of the deck. It dawned on me, now that everyone was watching, that I hadn’t actually done a backflip in about 2 years. But my body remembered how, and in the moment just after the flip and just before I hit the water, I remembered how good it feels to fly.

On the way back to the pier, Tom talked me through film photography. He has an old Nikon with a 50 mm lens. I love film photography. Digital is great when I’m doing jobs or traveling, but there is something so beautiful about how manual a film camera is. All of the settings are buttons and levers and switches, not clicks on a screen. And it’s heavier and you can watch the aperture change. And when you’ve taken your shot and you develop the film, you’re really creating the image with all of the different washes you do. I would love to get into film.

2Working with the DMCR was really interesting. Up until now, I’ve been doing a lot of measurements and transacts and fish counting, but I’ve never seen the results of all that data. Now I understand. It’s like fitting pieces of a puzzle together to get the big picture of what’s going on with this lovely patch of the world. The counting is a piece. The transect is a piece. All of these little bits of information make no sense by themselves, but when they are all combined, a greater understanding becomes a little clearer.

Today, we went to Mea Haad to do a survey on anchor damage. We need this information because then we can explain why it’s so important we have buoys in Mea Haad and at Sail Rock. I didn’t realize how much anchor damage there was on the reef until I learned how to spot it. And then it was everywhere. Huge chunks of coral broken off of rocks. You could see the fracture lines and the places where it all used to fit together. It was heartbreaking.

Nobody wants anchors dropped on the reef. The boats don’t like it because oftentimes the anchor gets caught on all the coral and it has to be cut loose, and new anchors are expensive. The conservationists don’t like it for well, obvious reasons :]

4I leave the day after tomorrow. I’m sad, but I’m also ready to go. I’m headed to Bangkok, where I will be staying with Justin and his girlfriend for a couple days, exploring the city.

New adventures on the horizon!!


Lina B.

Maybe you should do some research, and form your own opinion

13 Mar
March 13, 2014

I have tried and failed to write this post about four times now.

It is because, no matter how I fit my words together, I can’t describe in writing how much this place has changed my life.

It could be said that the profound changes in perspective and personality I have experienced since coming to Core Sea are based solely on the fact that I am in a different country, on my own, and that is enough to have a huge effect on anyone. But I think it’s more than that.

all“Core” in the dictionary, means “a central and often foundational part usually distinct from the enveloping part by a difference in nature” (Miriam-Webster). In the context of Core Sea, the ‘Core’ is an acronym for the Center for Oceanic Research and Education, and was named without thought of the literal definition of the word. And yet, this organization and these pe0ple embody the central and foundational part of this conservation work more gracefully and effectively than I thought possible.

The other day, when we were coming back from working with the DMCR, Eike was telling us about how he got into conservation work. He started out working animal conservation in Africa. He was describing to us how heartbreaking it is to work with animals because you do so much to save them but you can save a lion every single day for a year and they’ll keep dying as long as the habitat doesn’t get taken care of. This is why he eventually transitioned into marine conservation, and with it, habitat conservation. Because conserving the planet is the core of conserving everything else on it.

Before I came to Core Sea, I was surrounded by people who were just about to start college. Standing on the brink of the cliff that is leaving home and starting school and giving the next four years of your life to figuring out your role in society feels so big. But then I came here, and I’m around people who have already lived through those four years, and are now picking up the gauntlet they spent all that time learning about. At the end of the day, college isn’t the greatest adventure you will ever have. It is only four years out of many.

linaI’d recommend Core Sea for anyone who wants to be on the offense of this whole world-saving thing. It’s more than just measurements and fish counting. There are days where it is our job to simply dive and appreciate. Appreciate the way that bright purple anemones sway gently with the current like hair of the sea. Appreciate the way that sunbeams are broken by the water, throwing more colors into light than we knew existed. Appreciate how truly beautiful fish are when they swim. Appreciation is the key to the locked minds of society. When someone cares about something, they don’t have to be convinced to help save it, they’ll just want to. So we don’t tell them it’s a crisis, and we don’t tell them we’re all screwed. We say not all hope is gone, and we tell them to appreciate what’s out there. It’s easy, when you’re involved in all of the science stuff and the statistics that say all the reefs are gone in 5 years to completely lose motivation. But when we slow down and appreciate it, we realize that 5 years doesn’t actually exist. Fish are never late. Time is a concept humans invented. Because of this, we hold a fear that no other animal experiences–a fear of time running out.

This doom and gloom approach is felt throughout many conservation organizations because once you have your eyes opened to the problems of the planet, it’s hard to think anything you do could save it in time. But Core Sea is located on a slow-paced, relaxed little island, where time is more of an idea than an actual practice. So I feel like here, it’s balanced out. You can get all of the depressing information without feeling like you’re rushed to do something about it, which then makes it easier to take action.

I came to Core Sea with nothing, and I was welcomed with answers to questions I’d never even thought of and a family of people bonded by the desire to make a difference. I’m leaving with passion and a bunch of new knowledge.

I was also lucky enough to be here at the time I was, because I got to witness so many beginnings. All of the plans they’d spent years working on finally began to take shape. Eike led the publicity war, bringing the Core Sea Facebook page from 600 likes to over 10,000 in 6 weeks. We kicked off the Save Sail Rock campaign. We started putting in buoys. I am so sad to be going but so happy I was here.

naiThis is real world stuff. Anyone who wants to come to Core Sea will not be disappointed. You will be welcomed with enthusiasm. You will be challenged. You will be taught secrets of the sea and insanely cool science. And the best part of it is, you will actually make a difference on the planet.

But like Eike always says: “this is just my opinion. Maybe you should do some research, and form your own.”

Lina B. (click here for blog)hope