This is my second season in the paradise called Perhentian Islands working with the Perhentian Turtle Project. I am still overwhelmed about the beauty of the sea and still get excited every time I see a turtle. Being on marine surveys, diving into this blue paradise and taking pictures of the turtles is the best part of the day for me. You forget the time, everything around you and just enjoy the freedom of the ocean while being in the crystal clear water.
Most of the turtles we find around the islands are green sea turtles. Green turtles got their name due to their internal fat which is green from the seagrass they eat. A lot of people are not aware that turtles are actually doing a good job by eating seagrass and they are helping to maintain a healthy marine ecosystem. Seagrass has a lot of beneficial functions and its importance is very often underestimated. Although this small plant often receives little attention, it ensures there is good water quality by absorbing nutrients that have runoff from the land which can be damaging for marine life. Seagrass also reduces bacteria pathogenic to humans. With reports from areas in the world that have little or no seagrass of people got ill after being in the sea. In these places coral reefs were found to have infections with bacteria and fungi as well. Seagrass therefore makes the water cleaner and safer for us and helps us to enjoy our holidays and the beauty of the sea while swimming, snorkelling and diving. Furthermore, all divers and snorkelers know how important a good visibility for an awesome dive or snorkelling trip is. But a lot of people don`t know that seagrass influences even that. The roots of seagrass trap and stabilize the sediment which improves the water clarity and quality and even slow down water currents.
Seagrasses also provide shelter and food for a diverse number of fish, crabs and marine mammals. Without healthy seagrass beds the populations of many species of fish that we eat would decline. It also takes up nutrients from the soil and releases them through their leaves, making the water richer in nutrients which is a benefit, especially in nutrient poor regions. Seagrasses are known as the “lungs of the sea” because they generate so much oxygen every day through photosynthesis and help to take carbon dioxide out of the atmosphere. However, everything in life needs to be in balance, so does seagrass. If there is too much seagrass very often one species is dominant and competes with other species of seagrass which leads to a less biodiversity.
Green sea turtles eat this seagrass and so help to keep it in balance. The grazing doesn’t just prevent an unhealthy increase in seagrass biomass but it also has positive effects on the seagrass as well. Studies showed that grazing increases seagrass production, thereby increasing the food availability for green turtles and the amount of biomass and nutrients exported by the turtles. This export by turtles is thought to be the most controlling factor for seagrass under grazing and high nutrient loads. Grazing alleviates the negative effects of eutrophication by stimulation of seagrass production and related nutrient uptake and the increased export of nutrients. That is just another reason why it is so important to conserve these animals and prevent the decline of the population.
Marine ecosystems are very complex and humans tend to underestimate the smallest parts in it. Sometimes we forget that even we rely on a healthy marine ecosystem, not just on our holidays. So next time when you are on a dive or snorkelling trip, keep your eyes open and pay attention to the smaller, unremarkable things in your environment as well. I hope that more people start to understand the complexity of the marine ecosystem and how important every marine life is for us. And if I come back in 10 years to the Perhentian Islands, I hope I will still find the turtles here, feeding the sea grass around the island and resting on the colourful and beautiful corals here.
- Ramona Pfortner, ex-PTP staff member