Sangeeta uncovers the secrets of Kenya’s coral reefs

The secrets of the coral reefs lying along the coast of Kenya in Africa have been uncovered following years of painstaking research by Sangeeta Mangubhai.

Sangeeta, a PhD student with Southern Cross University, is back in Australia to complete the final part of her study, which she hopes will lead to better understanding and management of the reefs along the East African coast.

“The Western Indian Ocean experienced a temperature-related mass coral bleaching event in 1998 and a lot of the reefs suffered wide-scale damage and loss of their corals,” Sangeeta said.

“We need to understand when and how often the corals reproduce, and how successful those reproductive events are to be able to understand the potential for reef recovery.

“This is even more important now with coral bleaching events becoming an almost annual occurrence world-wide, with different regions affected to differing degrees.

“A lot of these developing countries haven’t had the expertise to do the research I am focusing on. The timing of spawning was not known in Kenya or other parts of East Africa, and I wanted to fill this big knowledge gap.”

Sangeeta moved to Australia from Fiji with her family in 1989. After completing her undergraduate studies, she worked in the Moreton Bay Marine Park and then in Fiji with the World Wide Fund for Nature coordinating their regional marine program in the South Pacific. She has spent the past five years living and working in Kenya.

“When I was starting my PhD I was more interested in the impacts of coral bleaching on coral reefs, but Peter Harrison (Associate Professor at Southern Cross University) put the idea in my head to look at coral reproduction on reefs in Kenya. We looked at a world map and he pointed to the Western Indian Ocean and told me that we knew virtually nothing about coral reproduction patterns in the region, and on equatorial reefs such as those in Kenya,” she said.

“He made me realise this was a chance to do something no-one had done before.”

Following years of research and many hours in the water, Sangeeta has documented for the first time how and when the coral spawn in that region.

“On the Great Barrier Reef here in Australia the coral spawning is a very concentrated synchronised event across hundreds of kilometres of reefs. More than a quarter of known species on the Great Barrier Reef spawn within a one-week period just after the full moon in the austral spring and summer, and it is consistent and predictable each year,” she said.

“In Kenya the spawning is also synchronised to the lunar night, but we have a much more extended reproductive season. Individual species spawn over two to five months.”

The spawning occurs during the north-east monsoon season, when the seas and winds are calmer and the water temperature is warmer.

“During the south-east monsoon the winds are stronger, the water temperature is cooler and the sea is rough. Only one of my 26 species spawned during this period, though it was not a large event,” Sangeeta said.

“In Kenya, spawning starts around October and then dribbles in throughout November and December. However, it is during January, February and March when a large percentage of the populations of different species spawn.

“At the moment we haven’t quite figured out what is the main driving factor that determines when corals spawn and why spawning is well synchronised in some parts of the world like the Great Barrier Reef, and less so in others such as Kenya.

“We believe it is likely to be a combination of temperature and light that play a large role in governing the timing of reproduction. We also think corals use lunar and tidal cycles to determine the month and night of spawning.”

Sangeeta said she hoped this new information on the reproductive patterns in Kenya would allow much better management of the reefs.

“There are lots of issues that need to be addressed along the coast, including poverty, and the reefs are heavily fished. My work will at least tell managing authorities when is the most important time for the coral reproduction and to perhaps minimise the damage during those times.”

Sangeeta said isolation was one of the biggest challenges she faced during her study.

“There were only a few people who I could talk to on a regular basis about my research, but I did come back every year for two to three months to meet with my supervisor (Peter Harrison) and we were in regular email and phone contact while I was in Kenya,” she said.

“I was also provided in-kind and some financial support by CORDIO East Africa, a regional organisation involved in coral reef research and monitoring.

“I would go out regularly to the reefs. The advantage in Kenya is you get much more time in the water and the reefs are more accessible. I used to paddle out on my surfboard into the lagoon to visit one of my sites.

“Sometimes my sites were difficult to find especially when you are lying on a surf board and it is an overcast day. The local fishermen who knew the reefs well would point me in the right direction if I looked a bit lost.

“My work involved collecting small samples from corals each month and looking inside their tissue to determine the maturity of eggs. Many coral eggs start off as white and four to six weeks prior to spawning they become brightly coloured.

“Once I saw coloured eggs in the field, I would bring pieces of corals into my ‘home-grown’ laboratory so that I could determine the exact night of spawning. New Year’s Eve 2004 is when I saw coral spawning for the first time, and it was a perfect start to the new year.”

Once her PhD is completed, Sangeeta said she planned to work again in developing countries in the area of coral reef conservation and science.

“There are so many really excellent coral biologists in Australia like my own supervisor and the other PhD students I interact with. I believe I can achieve a lot more in developing countries, probably in the Asia-Pacific, where expertise may be limited or lacking,” she said.

In the meantime she is planning a visit to Heron Island with Peter Harrison in November to witness the coral spawning in the Great Barrier Reef.

The trip is part of a prize she was awarded for her oral presentation during the annual Australian Coral Reef Society national conference.

“It’s quite exciting for me. Because snorkelling at night in Kenya was not feasible I only got to see my corals spawn in tanks. When I go up to the Great Barrier Reef it will be the first time I will see the spawning in the wild and I will get the chance to learn about coral larval rearing techniques by helping Peter with his own work. It will be a grand finale to my PhD,” Sangeeta said.

Photo: Sangeeta Mangubhai in a lagoon off the coast of Kenya.