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.
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.
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 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!
We are back with our spotlight on coral. Pocillopra damicornis is the third principal hard coral that we work with in Costa Rica. Our coral intern Sebastian has created this great article all about it.
Here are some cool coral facts about Pocillopora damicornis!
What is Pocillopora damicornis?
Pocillopora damicornis is a species of branching stony coral, commonly known as Cauliflower coral. The species is distinguished from other species by having thinner branches and less regular verrucae. While small, regular verrucae exist, most of the protuberances are irregular and are often not true verrucae at all but are more like incipient branches. As a result, Pocillopora damicornis exhibits greater branching than does P. verrucosa. Colonies are usually less than 30 cm tall. Reported growth rates of Pocillopora damicornis vary substantially between locations in the Eastern Tropical Pacific, from 1.27 cm per year in Colombia to 3.96 cm per year in Panama.
Pocillopora damicornis occurs at all depths between the surface and 40 m deep or more, and is particularly abundant between 5 to 20 m. It is equally abundant in lagoonal areas and clear water reef slopes. Commonly forms monospecific, densely packed stands many tens of metres across in water 5 -10 m deep.
Restoration Success with Pocillopora damicornis
We started our coral restoration project with Pocillopora damicornis and Pavona gigantea. Pocillopora is a great candidate for reef restoration, as a branching coral it is easy to harvest from wild coral colonies and it is also relatively easy to micro fragment. Pocillopora has responded well in our coral nurseries with good growth rates in both table nurseries and line nurseries. This coral species has a faster growth rate than the two massive coral species, which means shorter time in the nurseries, and therefore less maintenance and costs.
Geographic Range of Pocillopora damicornis
Pocillopora damicornis has a broad range which extends from the pacific coast of the americas america all the way to East Africa and the Red Sea. in the tropical pacific and through to oceania and southeast asia. The range of this coral in panama is it even considered as one of the major reef building species.
Feeding methods of Pocillopora damicornis
Cauliflower corals are a filter feeding species that catch plankton and other small organisms from the water column using their hair-like tentacles.
Sexual Reproduction of Pocillopora damicornis
Pocillopora damicornis is a broadcast spawner with the capacity to function as a simultaneous hermaphrodite. Pocillopora damicornis, like other Pocilloporid species in the eastern Pacific, has low rates of recruitment.
Histological evidence indicates that spawning is likely to occur during a few days around the new moon. The reproductive activity in the eastern Pacific is related to local thermal regimes. This then results in a generally higher incidence of coral recruits at sites with stable, warm water conditions. Also during warming periods in areas that experience significant seasonal variation. Pocillopora damicornis is also able to spread asexual due to natural fragmentation, making this coral a good candidate for restoration efforts.
Specific Living Conditions for Pocillopora damicornis
temperature: 20 °C -30 °C (optimal is 26 °C )
salinity: 34- 38 ‰
Depth: 0-40 meter
Ph: 8,1- 8,4
DKH: 8-12
Habitat: occurs in all shallow water habitats from exposed reef fronts to mangrove swamps and wharf piles
sedimentation, Pocillopora is relatively tolerant as long as there is adequate water motion
We hope you enjoyed the article, thank you to our intern Sebastian Moesbergen for writing it.
If you are interested in joining our team at Marine Conservation Costa Rica you can contact us. We run internships, volunteer programs and research opportunities, please contact us here.
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!
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
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
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
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 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!
The life of a marine conservation intern is a busy one. With current times our interns are safely back home and helping us from afar. As part of this one of our interns, Sebastian Moesbergen has been researching our coral species here in Costa Rica. Our first one here is Porites lobata.It is one of our 3 types of hard coral that we, at Marine Conservation Costa Rica, are fragmenting in our coral restoration project on the Pacific coast of Costa Rica. We thought you would be interested in a more in depth look at this interesting coral…so here goes for some cool coral facts!
What is Porites lobata?
Porites Lobata is a common reef-building coral that can grow into very large colonies, building large coral reefs throughout its range. This species forms large hemispherical or helmet-shaped structures that can reach several meters across. For this reason, Porites lobata is also known as “Lobe Coral”. Though they appear to be very large, only the outer few millimeters represent living tissue, while the rest is a calcium carbonate skeleton. Porites Lobata structures only grow a few centimeters each year and may be hundreds of years old. Each structure is actually a colony of several genetically identical animals living together. In some areas, several colonies grow together to form a nearly continuous stretch of Porites Lobatas that may be tens of meters (or more) long.
Restoration Success with Porites Lobata
We were initially uncertain about using Porites lobata in our restoration project, as it is a notoriously slow growing coral. However, after success with 2 other species of hard coral, we decided that Porites was the obvious choice to expand our project. It is one of the dominant massive corals in our region, along with Pavona gigantea. We initially tested fragmenting Porites lobata on a small scale. Only micro fragmenting 40 new fragments that went into 2 nurseries as 2 different locations. Initially, there was little growth in either nursery, but after 2 months we had significant growth. After 3 months most fragments were at least doubled if not tripled in size. In the last 6 months we have expanded our Porites lobata nurseries and look forward to outplanting Porties lobata back onto our reefs in Costa Rica.
Geographic Range of Porites lobata
Porites lobata has a huge geographic range throughout tropical and subtropical regions. Porites Lobata can be found from East Africa, the Red Sea and the Gulf of Aden. They can be found all the way through Indonesia and Australian waters to the Pacific coasts of California and Central America.
Feeding methods of Porites lobata
Many corals can function as carnivores, using their tentacles to capture small planktonic animals drifting over the reef. Special stinging cells that line the surfaces of the polyps’ tentacles entangle and paralyze their prey. Other corals are suspension feeders. They use hair-like structures called cilia to collect particles of organic matter that drift down from above. The polyps of Porites lobata are so small that researchers question if they are actually capable of capturing prey.
Luckily, corals also act as primary producers. Single-celled algae called zooxanthellae live within the tissues of reef-building corals in a symbiotic relationship. Using sunlight and nutrients from the water and their coral hosts, zooxanthellae generate energy-rich compounds through photosynthesis. These carbon-rich products may be particularly important in the energy budget of Porites lobata.
Sexual Reproduction of Porites lobata.
Unlike many species of corals, Porites lobata colonies are gonochoristic. This means they are either male or female, not both. They reproduce via broadcast spawning. This is where several individuals release their eggs or sperm into the water column at the same time. This method increases the likelihood that eggs become fertilized and reduces the danger from egg predators near the reef surface. Within a few days after the eggs hatch, larvae settle onto the reef surface and begin to form new colonies.
Specific Living Conditions for Porite lobata some scientific data for you…
Temperature range that the corals like is between 18 °C and 30 °C , for example, if the water temperature is higher than 30°C the coral starts bleaching). The Salinity ideal is between: 34 and 38 % and depth range between 0 and 30 meters. Ideal Ph is between 8,4 -7,7. They have an oxygen demand of 0,21 (μmol L−1 h−1) and a bacterial cell yield of 0,06 – 0,10( cells × 105 mL−1 h−1).
Want to become part of our team?
Want to join our team at Marine Conservation Costa Rica in the future to do a coral internship? Please contact us at info@marineconservationcostarica.org
Written by Sebastian Moesbergen
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!
