Coral Predators

Posted on January 17, 2025January 17, 2025 by Annabel Thomas

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Coral Predators

by Fahmi, AMD-B’s 2024 Divemaster Intern

Coral reefs are vibrant ecosystems, and like any environment, they have species that interact in different ways. Some creatures feed on corals as part of the natural balance of life on the reef. While it might seem concerning at first, this predation is usually just a part of maintaining a healthy ecosystem.

Key Coral Predators

Crown-of-Thorns Starfish (COTS):
The Crown-of-Thorns Starfish is one of the most well-known coral predators. These spiny creatures feed on coral polyps, digesting the living tissue and leaving behind the skeleton. While they’re a natural part of the ecosystem, outbreaks can lead to significant damage to coral reefs.

Parrotfish:
Parrotfish are famous for grazing on coral. Their strong, beak-like teeth allow them to scrape away pieces of coral, which they digest and later excrete as sand. While this sounds harmful, they also help control algae, preventing it from overtaking the reef. In moderation, their coral consumption is part of the reef’s healthy balance.

Drupella Snails:
These small snails feed on coral polyps and can leave marks on the coral. They usually don’t cause widespread damage but can be a part of the natural predation cycle on reefs.

Butterflyfish:
These colorful fish feed on soft corals and polyps. Their impact is relatively minor, and they’re another example of how coral predation is part of the reef’s life cycle.

When Populations Get Out of Control

In most cases, coral predators are just a part of reef life. However, when their populations grow too large, they can cause significant harm. One example is the Crown-of-Thorns Starfish outbreaks. These outbreaks occur when the starfish population spikes, often due to factors like pollution or overfishing of their natural predators. During an outbreak, the starfish can consume large areas of coral, leaving behind dead coral skeletons.

Such outbreaks can severely weaken coral reefs, making them more vulnerable to other threats like climate change, ocean acidification, and storms. When the balance shifts too far, the reef can struggle to recover.

Manta Rays

Posted on December 26, 2024December 26, 2024 by Annabel Thomas

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Manta Rays: Their Life Cycle and Why They are Vulnerable

by Fahmi, AMD-B’s 2024 Divemaster Intern

Manta rays have a unique but slow reproductive process. Female manta rays give birth to live pups after a pregnancy lasting about a year. What makes them vulnerable is that they typically produce only one pup at a time and may take two to five years before reproducing again. Once born, the pup is left to survive on its own and spends nearly a decade growing and maturing. This slow reproduction rate means manta populations struggle to recover when their numbers are reduced.

Manta rays are highly migratory creatures, travelling vast distances in search of food and suitable habitats. While this behaviour is essential for their survival, it increases their exposure to various threats. Overfishing, entanglement in fishing gear, and habitat destruction—such as the loss of coral reefs that serve as feeding or cleaning stations—pose significant risks. Climate change and pollution also impact the plankton populations that mantas depend on for food, making their survival even more challenging.

Why Manta Rays Matter

Although manta rays do not have a massive ecological role compared to species like sharks or corals, they contribute to marine tourism in a significant way. Destinations like Nusa Penida and Raja Ampat attract divers and snorkellers eager to witness these majestic animals. The revenue from manta ray tourism supports local economies and often funds conservation projects, creating a positive cycle of benefits for both humans and the environment.

The Importance of Protecting Manta Rays

Manta rays are not just symbols of marine biodiversity; they are also indicators of ocean health. Their vulnerability reminds us of the delicate balance in marine ecosystems. Protecting manta rays is not only about saving a species—it’s about safeguarding the health of our oceans, promoting sustainable tourism, and respecting the interconnectedness of life underwater.

Microplastics Inside the Coral Tissue

Posted on November 15, 2024November 19, 2024 by Annabel Thomas

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Microplastics – How do They End Up in the Ocean

by Fahmi, AMD-B’s 2024 Divemaster Intern

Microplastic are tiny fragments of plastic, usually less than 5 millimeters in size, that originate from textiles, such as microfiber shedding, personal care products or cosmetics, paint, tires, and the fragmentation of larger plastics we use. Like the plastic we are familiar with, microplastics are not biodegradable. The problem now is that they are resilient and ubiquitous. Microplastics have been found in nearly every environment, including animal digestion, and even humans. Due to their tiny size, microplastics spread through things like rainfall, rivers, and direct waste dumping. These particles make their way into our oceans, spreading across marine environments and impacting ecosystems everywhere.

Why are Corals Found with Microplastics

As filter feeders, corals pull in tiny particles from the water, mistaking microplastics for food. Because of their size, microplastics closely resemble natural food sources for coral, making them easy to ingest. Studies have shown that some types of coral might even prefer these plastic particles. Unfortunately, this means microplastics get lodged in coral tissues, often staying there for a long time.

How do Researchers Study Microplastics in Coral

To investigate, scientists collect coral samples and apply special dyes to make any microplastic particles stand out. They also use methods like spectrometry and fluorescence microscopy to locate and identify plastics at the microscopic level, helping to determine how much plastic is really being taken in by coral. In some cases, researchers use a process called acid digestion, where a mild acid dissolves the calcium carbonate skeleton, leaving behind microplastic particles. This method, used by one of our team members, enables a clear analysis of embedded plastics without damaging them.

What Microplastics Mean for Coral and Marine Life

For corals, microplastics are a big concern. These particles can get trapped in coral tissues or on coral surfaces, affecting their health. When corals absorb microplastics, it can lead to physical damage, reduced feeding efficiency, and even increased vulnerability to diseases. Corals rely on tiny algae called zooxanthellae, which help them get energy through photosynthesis. Microplastics can block light, disturbing this process and possibly contributing to coral bleaching.

Marine life that depends on corals for shelter or food can also suffer. Fish, crustaceans, and other creatures might ingest microplastics, which can lead to internal injuries, malnutrition, or chemical contamination, affecting entire marine ecosystems.