Spotlight on Coral – Threats to Coral

Spotlight on Coral – Threats to Coral

Threats to Coral Reefs

If we are to be able to protect coral reef systems it is very important to know what kind of threats corals are dealing with right now!
We can divide these threats in three groups: abiotic threats, biological threats and anthropogenic threats. So let’s take a look…

Abiotic threats to Coral Reefs

Abiotic threats are caused by physical or chemical factors that  affect living organisms and the functioning of an ecosystem. For instance in reef systems temperature, light, pH and salinity but also things like chemical components in soil and water.
A current and widely known result of changes in physical factors is coral bleaching. Coral bleaching happens when corals lose their vibrant colors and turn white.

But there’s a lot more to it than that. Coral are bright and colorful because of microscopic algae called zooxanthellae. The zooxanthellae live within the coral in a mutually beneficial relationship, each helping the other survive. But when the ocean environment changes, particularly to an increase in temperature, the coral is put under stress and expels the algae. When the algae is expelled, the coral’s colors fade until it looks like it’s been bleached. If the temperature stays high, the coral won’t let the algae back, and the coral will die. The leading cause of coral bleaching is climate change. A warming planet means a warming ocean, and a small change in water temperature—as little as 2 degrees Fahrenheit—can cause coral to drive out algae. Coral may bleach for other reasons, like extremely low tides, pollution, too much sunlight, change in pH. 

Other abiotic threats can be the wind, weather and the waves that cause the physical damage of coral reefs. Turbidity can cause a lack of sunlight for the corals, this makes the corals unable to perform photosynthesis. Other things that may cause stress to the corals are a change in sediment levels, pressure, salinity, current, ocean depth and nutrients.

bleached coral
bleached coral costa rica

Biotic threats to Coral Reefs

Biotic threats are caused by the living components of an ecosystem, for instance the fishes, invertebrates and competing corals. They are mostly natural interactions between corals, parasites, predators, or coral disease. They can also be non natural threats, like invasive parasites, predators and coral diseases that have been introduced to a coral ecosystem.

Anthropogenic threats to Coral Reefs

Anthropogenic threats are threats caused by humans. Humans may also be indirectly responsible for many biotic and abiotic threats; like ocean warming and the introduction of non-native species in many ecosystems all round the globe.
Most coral reefs occur in shallow water near shore. As a result, they are particularly vulnerable to the effects of human activities. This is both through direct exploitation of reef resources, and through indirect impacts from adjacent human activities on land and in the coastal zone. Many of the human activities that degrade coral reefs are inextricably woven into the social, cultural, and economic fabric of regional coastal communities. 

Pollution, overfishing, destructive fishing practices such as using dynamite or cyanide, collecting live corals for the aquarium market, mining coral for building materials, and a warming climate are some of the many ways that people damage reefs all around the world every day. 

One of the most significant threats to reefs is pollution. Land-based runoff and pollutant discharges can result from dredging, coastal development, agricultural and deforestation activities, and sewage treatment plant operations. This runoff may contain sediments, nutrients, chemicals, insecticides, oil, and debris.

When some pollutants enter the water, nutrient levels can increase, promoting the rapid growth of algae and other organisms that can smother corals.

Coral reefs also are affected by leaking fuels, anti-fouling paints and coatings, and other chemicals that enter the water. Petroleum spills do not always appear to affect corals directly because the oil usually stays near the surface of the water, and much of it evaporates into the atmosphere within days. However, if an oil spill occurs while corals are spawning, the eggs and sperm can be damaged as they float near the surface before they fertilize and settle. So, in addition to compromising water quality, oil pollution can disrupt the reproductive success of corals, making them vulnerable to other types of disturbances.

Ocean acidification is mainly caused by increased levels of carbon dioxide gas in the atmosphere dissolving into the ocean. This leads to a lowering of the water’s pH, making the ocean more acidic. This in turn causes the hard limestone skeletons of coral to become weaker and in some areas the reef is crumbling away.

Many factors contribute to rising carbon dioxide levels. Currently, the burning of fossil fuels such as coal, oil and gas for human industry is one of the major causes.

diseased coral

In many areas, coral reefs are destroyed when coral heads and brightly-colored reef fishes are collected. They are sold for the aquarium and jewelry trade. Careless or untrained divers can trample fragile corals, and many fishing techniques can be destructive. In blast fishing, dynamite or other heavy explosives are detonated to startle fish out of hiding places.

This practice indiscriminately kills other species and can demolish or stress corals so much that they expel their zooxanthellae. As a result, large sections of reefs can be destroyed. Cyanide fishing involves spraying or dumping cyanide onto reefs to stun and capture live fish. This can kill coral polyps and degrades the reef habitat. More than 40 countries are affected by blast fishing, and more than 15 countries have reported cyanide fishing activities.

Other damaging fishing techniques include deep water trawling. This involves dragging a fishing net along the sea bottom. There is also muro-ami netting, in which reefs are pounded with weighted bags to startle fish out of crevices. Often, fishing nets left as debris can be problematic in areas of wave disturbance. In shallow water, live corals become entangled in these nets and are torn away from their bases. In addition anchors dropped from fishing vessels onto reefs can break and destroy coral colonies.


What can we do to stop threats to coral reefs?


Without a doubt, at this time, humans are causing the most threats to coral reef systems. Coral have thrived on earth for it is thought to be over 500 million years. Humans have been around for the last 200,000 years. With industrialization and the greed in recent decades, there is a real possibility that we could wipe them out in the next 50 years.
Coral restoration projects can only do so much. We all need to make positive changes in our lifestyles to help coral reefs. If we can slow climate change, reduce C02 emissions, and choose to spend money on sustainably produced products, we might be able to make a difference!

So next time you turn off a light or walk to work, remember you are helping coral reefs!

If you would like to support our project, we accept donations through PayPal at paypal.me/Marinecostarica 

sebastiaan marine conservation intern

Sebastiaan Moesbergen joins us from the Netherlands. He is currently studying applied Biology at University and has been enrolled in our internship program since the beginning of March. As part of his internship he is assisting us with research and investigation and has been spearheading our spotlight on coral articles. Thank you Sebastian!

Spotlight on Coral – Pavona gigantea

Spotlight on Coral – Pavona gigantea

We are continuing our Spotlight on Coral Series of Blog. This week we look at another or our 3 types of hard coral that we are fragmenting in our coral restoration project at Marine Conservation Costa Rica. So here’s an indepth look at Pavona gigantea…..

What is Pavona gigantea?

Pavona gigantea is known as plate coral or leaf coral. It is a common coral that grows in relatively shallow and protected areas. Pavona has a naturally occurring growth rate of between 9 and 12 mm each year and also grows large plate colonies. They have visible coralites with a width of between 3 and 6 mm. The colonies tend to have a furry appearance due to the extension of their tentacles during the day.

Restoration Success with Pavona gigantea

Fragment of Pavona
restoration of Pavona Gigantea

Pavona gigantea can be relatively easy to harvest and fragment, as it often grows in plate formation. The younger growth to the edge of a plate is often thin and can be easily harvested. The older growth is thicker and extremely dense. The Pavona has responded well to micro fragmentation in our restoration project. Pavona gigantea seems to be reasonably resilient to stress and we have had a low mortality rate.

Geographic Range of Pavona gigantea

Pavona gigantea is found in the pacific ocean, growing along the coast of middle america from Mexico to Ecuador and in the Galapagos and Cocos Islands. In the Mid- Western Pacific, it is found in reefs located in the middle of the ocean. This is around the body of water between Japan and Papua New Guinea.

Feeding methods of Pavona Gigantea

Pavona Gigantea in Costa Rica

Corals consume particulate organic matter and absorb dissolved organic matter. However, their consumption of plankton is limited to zooplankton that is in the 200- 400​ ​μm size range. They use their tentacles to obtain this food. The same as other hard corals, Pavona gigantea depends on receiving most of its energy from it’s symbiotic relationship with the Zooxanthellae. These use photosynthesis to harness energy..

Sexual Reproduction of Pavona Gigantea

Typically Pavona gigantea colonies are gonochoristic, broadcast spawners. This is that there are both male and female colonies releasing eggs into the water column. Spawning takes place at the beginning of the rainy season, normally between May and July. Interestingly, in a few studies of Pavona gigantea, hermaphroditic colonies have also been discovered! This is likely to be an example of sequential cosexuality. It is when corals can begin their reproductive life as males and then become hermaphroditic. It has been suggested that sequential cosexuality is an adaption to guarantee sexual reproduction and increase connectivity among populations.

Specific Living Conditions for Pavona gigantea

Temperature: 18 °C -29 °C
Salinity: 34- 37 parts per thousand
Depth: abundant between:0,5 -20 meters Ph: 8,1
Dissolved oxygen concentration: 4.55 mL/L

Nitrate concentration: 0.831 ​μmol/L Phosphate concentration: 0.357 μmol/L Silicate concentration: 1.776 μmol/L

We hope you learnt something. Thank you Sebastian for the great info and help with this. If you want to learn more about our project you can contact us here or apply to become a volunteer or intern here in Costa rica.

Sebastiaan intern with marine conservation costa rica

Sebastiaan Moesbergen joins us from the Netherlands. He is currently studying applied Biology at University and has been enrolled in our internship program since the beginning of March. As part of his internship he is assisting us with research and investigation and has been spearheading our spotlight on coral articles. Thank you Sebastian!

What is coral bleaching? Why does it happen?

What is coral bleaching? Why does it happen?

coral bleaching
 Image credit: Wikipedia via CC license

Coral bleaching, the phenomenon, the event that has brought scientists from all around the world together to discuss a single question- what is happening to our coral? Climate change skeptics and environmental downfall contributors have no other option than to acknowledge the reality of this current mass global issue.

An event that has been trending and turning heads from all over, even reaching world news. It has made its way to fame and has quickly gotten the attention of the human race- but do you really know what coral bleaching is?

So what is coral?

Looking at coral from its outward appearance, it can be disguised as a simple being that has no other purpose than for fish to inhabit and feed on. Some even mimic a rock substance. It is only when you look within that you realize that it is not a simple being at all.

bleached coral

Coral colonies are made up of tiny, yet extraordinary polyps that resemble sea anemones. An algae called Zooxanthellae, or Zoox,  benefits the coral by living inside the polyps and photosynthesizing. This provides the necessary nutrition a coral needs to be able to be, well, coral.

Benefits of coral

Scientists are fascinated with the advantages that coral provides. In reality, these ancient and complex animals are what millions depend on for their survival. Some benefits of the reef include protection from tropical storms and waves. Also tourism, food, habitat and protection for many marine species, and even medicine. Imagine what would happen if we were to lose all of this due to the recklessness of our own generation? Well, the truth is that we already are on our way to doing so.

Our environment is sufferering

When you take a step back from the normality that our society has been convinced is sufficient and ideal, you will be shocked. As humans we have developed this hunger for more. We can’t get enough whether its money, power, food, clothes, etc. Then we are basing these needs off the idea that we will never run out, thus mass producing. It is only when we wake up from this false mentality that we can see what we are doing to our planet. The environment has been silently suffering from our carelessness for a long time. But it is finally grabbing our attention through natural disasters such coral bleaching. 

a bleached coral reef
Coral bleaching at Molokini Crater

Our carbon pollution is affecting our climate worldwide, especially our oceans. With life as fragile as coral, the rising temperature of only a few degrees can dramatically alter their ability to function. This can almost certainly lead to fatality, or otherwise known as bleaching. Car pollution, factory pollution, mining and burning of coal, and other destructive actions of man are collectively working together to kill coral reefs by stressing them out.

Like humans who react to fevers, the coral reacts to heat by expelling the zooxanthellae. The disruption of the zoox and coral relationship causes the coral to starve. This is due to the lack of nutrients obtained through photosynthesis. They then turn the color white we so famously see, giving it the name “bleaching”. Although most believe that a coral is dead once it has turned this holy white, it is actually still alive. It has the potential to recover. It is only once the tissue is extracted and rotting from the coral that it is officially too late. 

Other factors like overfishing, pollution, and sunscreen, work as a team to cause coral bleaching on our coral reefs. If we continue to go down this wasteful and harmful path, we will only increase the severity of coral bleaching. A species that has survived for centuries is now depleting in only a few years due to the intensity of our ways. It can take decades for a reef to recover and less than a decade to destroy it. If we continue our mass burning of fossil fuels and increase our carbon pollution in the atmosphere, these severe bleaching events will continue annually. Coral is vital to life on Earth and the mass bleaching events are a cry for help. It is now up to us to ensure that the coral reefs are not gone for good.

So what can you do?

A few ways to help save our reefs and our planet:

Transportation (biking, walking, bus)

Reef Safe Sunscreen

Reduce, Reuse, Recycle

Speak Up

Reduce Runoff in our oceans

Eat sustainably

Keep feet/fins off of the reef 

Coral Diaries – November begins

Coral Diaries – November begins

November to me, always brings a sense of anticipation. You can feel the summer coming to Costa Rica. In October, businesses take their annual vacation and boats get their bottoms painted November though is the start of the new season. 
Here at Marine Conservation Costa Rica we are also really excited to get back in the water!

Marine Biologist John Reinbott

Starting this season, we welcome John Reinbott to our crew. John is a marine biologist and is fresh from a year long internship at the Coral Restoration FoundationTM in Florida. John and I are going to be working closely together on our coral restoration project. This last week we have been looking at the nurseries. We have also been brainstorming lots of ways we can improve on our current methods…and it’s been fun!

coral conservation intern
Welcome Coral intern – Anna

We also welcome Anna, our new coral intern from Ecuador. She will be helping us with data collection, maintenance and cleaning. Also building new structures and community education.
Looks like it’s going to be an amazing season! 

If you are interested about what we get up to, you  can see on our daily goings on on our Instagram stories @marineconservationcostarica