Archive for the 'Caribbean Sea' Category

Extensive coral bleaching is destroying reefs

According to the National Oceanic and Atmospheric Administration (NOAA) of the U.S., the longest coral bleaching ever is occurring in the tropical seas. The on-going, especially strong El Niño is prolonging the event, which started in 2014 and which is likely to lead to a wide-spread die-off of reef corals around the world. The scientists of NOAA expect the bleaching to continue in 2016 and 2017. So far, the Caribbean, Indian Ocean and Pacific Ocean have been affected.

The current bleaching is a serious environmental accident not only for all of us fascinated by the oceans, but especially for those 500 million people whose survival depends on the reefs. Fish species important for human consumption live in the coral communities. In addition to provision of food, the reefs also protect the islands and coastal areas from erosion and other damage caused by powerful waves.

Partly bleached coral colony in Saint Lucia. Copyright (c) 2016 Erkki Siirila.

Partly bleached coral colony in Saint Lucia. Copyright (c) 2016 Erkki Siirila.

Coral reefs are also key habitats for marine biodiversity and, related to that, increasingly important for underwater tourism. NOAA estimates the positive annual contribution of coral reefs to world economies to be about 30,000 million US dollars.

When corals get stressed by elevated seawater temperatures, they expel their zooxanthellae, the microscopic algae living in their tissues. As the pigment is in the algae, the corals lose their typical color. Bleaching is a serious occurrence, because without their symbiotic zooxanthellae the corals are starving as the microscopic algae are a significant food source. The bleached corals also become attacked by diseases more easily than before.

In case the average water temperature continues at levels higher than normal for several days, the corals can not recover their symbiotic algae and may die. When the colonies die, erosion starts eating reef structures away. A high percentage of the coral area may be lost for ever if a new bleaching hits the reef within a few years, i.e. when there has been too little time for recovery. As in many cases there are also other environmental stress factors (overfishing, sediment runoff, etc.) present, in today’s world, complete recovery is often impossible.

The first serious global bleaching in history occurred in 1998. The second one occurred in 2010. Like in the current third one, the El Niño / La Niña phenomenon is seen as the main underlying course (via elevated mean sea water temperatures). Global climate change is considered as a significative contributing factor behind the exceptionally strong El Niño and La Niña weather changes.

Progress in Tela reef conservation in Honduras

Text and photos (c) 2013 Erkki “Eric” Siirila, copyright & all rights reserved. 

Some years ago the city of Tela in Honduras was only known for its beaches. No one was aware that underwater additional national heritage could be found. The coral reefs of the Tela Bay are this other treasure.

The Tela Bay in Honduras has coral reefs, the conservation of which needs attention. Photographer and copyright (c) 2013 Erkki Siirila.

The Tela Bay in Honduras has coral reefs, the conservation of which needs attention. Photographer and copyright (c) 2013 Erkki Siirila.

Francois Ligeard, The Chamber of Tourism of Tela, says: “The good news is that we can offer a new site for both the national and international tourist. We have to highlight the fact that this place is very beautiful. It has high cover of live coral. We notice that always when we dive on this reef. One easily gets emotional because every time we go the local reef we find something new and more beautiful.”

Dennis Sierra, The Prolansate Conservation Foundation, Tela, sees the “newly discovered” coral reefs in the following way: “The best news is that in Tela we have many people both in the civil society, local government and the business sector who are very interested in the conservation of the coral banks of the Tela Bay. The preservation needs have an acceptance at the community level. Also at the level of the central government there is a lot of interest in declaring a marine park in the Bay of Tela.”

Only fishing was done on the local Capiro Reef in the past. Nowadays, divers come here to see the angelfish and the many species of coral. For example, black coral is found here.

The coral bank of Capiro is the best known reef area in the Tela waters. Photo and copyright (c) 2013 Erkki Siirila.

The coral bank of Capiro is the best known reef area in the Tela waters. Photo and copyright (c) 2013 Erkki Siirila.

Dennis Sierra: “Logically we look toward the future generations. We need to implement conservation actions in the Bay area, if we want to leave this ecosystem as a heritage to our children. Tela has been favored by God. We have to remember that the natural richness we have in Tela contributes in a positive way to tourism opportunities here. Tela has its future in the resources of that Bay.”

Francois Ligeard: “The biggest challenge we face is to take care of the reef both for our generation and the future generations. We need to get the fishermen and other local people involved to be able to preserve this reef. We have been working already by installing permanent mooring buoys. In this way, we need not anchor the boats and we can stop the damage that has been caused to the reef by anchors in the past.”

The mangroves of the Bay may not be forgotten as reef conservation is promoted. The mangroves produce nutrition for marine life. In addition, among the roots, many species of coral reef fish live during their juvenile stage. The mangroves also protect the coast from the waves of the sea.

The seagrass beds in the Tela waters have functions similar to those of the mangroves. In addition, many reef fish migrate to the seagrass areas in order to eat.

When forests are preserved, there is only little erosion on land and less mud enters the sea via the rivers. This is crucial in reef conservation as the corals need clean and clear water. Related to the above, it is also necessary to develop the treatment of sewage and waste waters.

In the Tela Bay there are very healthy coral colonies. It is important to take care of the reefs, because climate change threatens them, through the elevated sea-water temperatures and through the acidification of the sea.

Coral reefs will be more resistant to global environmental changes, when at the local level there is no overfishing and when the other pressures are kept at the minimum level. In this way, the coral reefs of Tela will produce economic and environmental benefits to us also in the future.

The following Youtube video was shot and produced by the Coastal Challenges’ Editor. It tells the above story of the Tela coral reefs in Spanish. The original is in high definition; this lower-resolution Youtube version can be best seen be adjusting the image resolution under the Youtube window to 480 p.

Coral conservation in Honduras: building on local roots is important

“We have got one of the best coral reefs in the Caribbean”, says Nelbin Bustamante from the Prolansate Foundation and Amatela reef conservation group of the Town of Tela, Honduras.  More in detail, Mr. Bustamante summarises the good news of a recent underwater study on the Tela reefs in the following words: “The live coral cover on our reefs is nearly 70 per cent per square metre”. This high number was registered on the Capiro Reef just seven kilometres from the city centre.


An offshore reef near Tela, Honduras. Photographer and copyright (c) 2012 Erkki Siirila.

Nevertheless, all the evaluation results were not positive. Mr. Bustamante says: “It could also be observed that the number of herbivorous and commercial fishes had reduced. Their biomass had gone down.”

As regards the threats, two main threats were identified in the study. One was the loss of forest cover. The other one was the lack of wastewater treatment. The Tela wastewaters flow directly into the sea and coral reefs. In addition to soil, the runoff contains many chemicals including fertilizers. The nutrients in the runoff may facilitate algal growth on the reefs as, at the same time, the levels of herbivorous fishes consuming the algae are lower than normal. Overfishing is an additional threat which needs to be controlled in Tela.

In any case Tela is a good and encouraging example in a world where the coral reefs are threatened by high fishing pressure, global climate change and other side effects of the growth of human societies. Off Tela, fairly healthy coral reefs can still be found and new awareness is creating motivation to protect the reefs.

Mr. Marcello Dicunta Servellón, who operates a dive centre in Tela, is satisfied: “Healthy coral reefs represents incredible opportunities. One of the most obvious ones is recreational diving. A well-managed dive industry on healthy reefs can result in high economic growth for the community.”

A Spanish-speaking documentary (Corales para amar – Tela protege sus arrecifes) with the above-mentioned content can be watched on Youtube:

Days of Eastern Caribbean reefs are numbered

The West Indies’ coral reefs will disappear in a few decades. This is the shocking result of a new scientific study. Individual coral colonies will survive in the region even in the future, but the coral reef ecosystem as we currently know it will disappear. All this will lead to significant economic losses, particularly for island and coastal people whose livelihoods are closely linked to coral reefs and the ecosystem services they provide.

Global climate change is the main reason for the dramatic changes. The powerful adverse effects were shown in the Eastern Caribbean already in 2005, when the health of the region’s reefs weakened and live cover dropped during an extensive coral bleaching.

The study by Buddemeier et al. tells that it is already too late to stop the reef death. The big changes in the coral reef environment will take place even if substantial emission cuts of greenhouse gases are implemented in the coming years.

Coral reefs of the Caribbean are facing difficult times: efficient conservation measures are needed urgently. In addition to global emission cuts of greenhouse gases, innovative local conservation actions would be important. Photo copyright (c) 2011 Erkki Siirila.

The study published in the journal Climate Change in 2011 focuses on Eastern Caribbean reef health and especially the Virgin Islands’ area. The COMBO (COral Mortality and Bleaching Output) model was used for the predictions. Three realistic emission scenarios for greenhouse gases were the basis for the simulation.

The results indicate that future bleaching episodes will be followed by the reduction of live coral cover on the reefs. (Most of the damage will be caused by the warming of sea waters and related bleaching. The decline in reef condition will take place even if the adverse effect of ocean acidification is calculated as minor.)

If there is no adaptation by the corals to the elevated mean water temperatures, the live coral cover on the West Indies’ reefs will decrease to less than 5% already by the year 2035. In a scenario where corals develop an additional 1–1.5 degrees Celcius of heat tolerance (through a shift in the symbiotic algae that live in the coral tissues) coral cover above 5% could last until 2065.

The researchers did not include reefs which are located more than 30m underwater. Live coral cover between 5 and 10% was considered a limit where the reef would not be able to regenerate itself and could not be called a real coral reef any more. For several of these modeling scenarios, the researchers used starting levels of coral cover of 7%, 15%, and/or 30%. These values are realistic values in the Eastern Caribbean.

Buddemeier et al. summarise their study by saying that “coral reef communities are likely to be essentially gone from substantial parts of the Southeast Caribbean by the year 2035, given the current low cover values following the 2005 event” and that “the conversion of coral reefs to fundamentally different systems will have large implications for the provision of ecosystem services”. The authors add: “Given the modeling results presented here, urgent efforts are needed to identify and protect what appear to be the most resilient coral reefs in the Caribbean.”

The whole study (R. W. Buddemeier, Diana R. Lane and J. A. Martinich, Modeling regional coral reef responses to global warming and changes in ocean chemistry: Caribbean case study, Climatic Change, 2011, DOI: 10.1007/s10584-011-0022-z) can be found here: Study by Buddemeier et al.

Human wastewaters infect elkhorn coral

A human pathogen has been shown to contribute to the degradation of elkhorn coral (Acropora palmata) colonies in the Caribbean Sea. The pathogen Serratia marcescens is known to be present in human wastewaters, which enter the coastal marine areas untreated in many parts of the Caribbean. In the recent study by K.R. Sutherland et al., strain PDR60 of the pathogen was shown to cause disease signs in A. palmata colonies in as little as four or five days, when the surrounding waters were polluted with S. marcescens.

In the Caribbean the lack of wastewater treatment is a common problem. This colony of elkhorn coral looks healthy in spite of the fact that raw sewage enters the sea 100m from the reef. Photo taken in Utila, Honduras, copyright (c) 2011 Erkki Siirila.

In 2003 there was an outbreak of this coral disease called acroporid serratiosis (APS). During the episode, the corallivorous snail Coralliophila abbreviata and stony coral Sideastrea siderea were noticed to be play a role in the development of the disease. Now, in aquaria experiments, wastewater has been demonstrated to be a definitive, direct source of the disease, while C. abbreviata and S. siderea are known to act as vectors and reservoirs, which may also to contribute to the infection of A. palmata.

The research results by K.R.Sutherland et al. published in 2011 demonstrate for the first time that a human pathogen can be passed from us humans to marine invertebrates and infect them. The authors of the study “Human Pathogen Shown to Cause Disease in the Threatened Eklhorn Coral Acropora palmata” say that “these findings underscore the interaction between public health practices and environmental health indices such as coral reef survival”.

A direct link to the article is here:  Elkhorn and sewage

Sediment control strategies for the coastal zone

Guidelines for Sediment Control Practices In The Insular Caribbean is one of the most practical and useful coastal management handbooks ever written. The report was published by CEP (the Caribbean Environment Programme) of UNEP in 1995. Fifteen year have passed and the publication is as useful as ever.
On land, the loss of fertile soil during rains is a big problem in agricultural areas of developing countries: farmers would need a steady income to survive and the growing population would need more and more food. Survival is difficult also in forest areas where logging or other human activities have destroyed the rain forests: the thin layer of fertile soil is quickly lost during the rainy season and this hampers reforestation. The globally important Amazon rainforests in Brazil are an example.
Don Anderson, the author of the CEP report, summarises the background to the guidelines in the following words: “Among the impacts of greatest concern in the insular Caribbean today are accelerated soil erosion and the delivery of eroded material to sites where it is not wanted.”

Erosion control on land supports the conservation of underwater ecosystems. Good ecosystem health will benefit these young fishermen in the Eastern Caribbean. Photo (c) 2010 Erkki Siirila.

Sensitive areas receiving sediment runoff from land include coral reefs, mangrove swamps, seagrass beds and fishing areas.  Receiving areas may also include recreational beaches, water reservoirs, navigable harbours and other zones crucial to maintenance of tourism and other economic activities.
Coral reefs are especially vulnerable to excessive sediment inputs. Sediment runoff from land was considered as the number one reef killer in the world before global climate change and coral bleaching got that position a few years ago. Coral polyps need to use extra energy to get rid of the sediment particles, the polyps get stressed and may finally die.  Sediments in the water also result in turbidity which reduces the amount of light in the depths. As a result, photosynthesis of the symbiotic algae in the coral tissues may stop and the coral starve. The lack of light is another cause of reef bleaching – the elevated mean water temperatures are not the only cause. Finally, in areas where excessive sediments have lead to loss of suitable substrata, juvenile corals have a poor survival rate.

Coral colonies were buried under mud in Saint Lucia, when heavy rains led to unprecedented runoff from land. A few days later a high percentage of the coral surface was bleached resulting in partial mortality of these Caribbean reefs. Underwater image (c) 2010 Erkki Siirila.

The CEP guidelines summarise the  Caribbean coastal erosion in the following manner: “Where land has been disturbed by human activity, the rate of erosion usually increases.  This accelerated erosion is typically many times the natural rate”.
Direct raindrop impacts result in splash erosion. Sheet erosion takes place when water flows over the soil surface. Rill erosion occurs when surface runoff leads to small eroding channels. Enlarging and joining rills lead to gully erosion. The most rapid erosion is caused by mass wasting processes, which are induced by gravity alone.
The CEP guidelines stress the need for sediment reduction programmes.  The report divides the technical work in three action areas:
  • watershed planning and management
  • stream corridor management, and
  • site-specific erosion and sediment control practices
As regards the institional considerations, the guidelines tell us that the most important challenges are these:
  • identify a lead agency
  • identify the responsibilities and limits of jurisdiction of each agency, and
  • ensure that key responsibilities are not overlooked and that there is no duplication of work
In addition, the educational and training efforts are considered critical for success. The public in general needs to understand key erosion-related issues while those in charge of the technical work need special training.

Well-functioning sediment control practices are needed on the Caribbean island of Roatan in Honduras. Coral reefs surround the island. Reef degradation due to soil runoff is visible underwater in the area where the picture was taken. Photo (c) 2010 Erkki Siirila.

The best management practices suggested in the CEP guidelines cover the following issues. This list helps us understand the wide scope of sediment control needs in coastal areas:
  • development practices: clearing only essential areas, minimising road disturbances
  • surface stabilisation: seeding, mulching and matting
  • runoff diversion: perimetre dikes and swales
  • runoff conveyance: lined channels, temporary slope drains, check dams
  • outlet protection
  • sediment traps and barriers: sediment fences, brush barriers, sediment basins, sediment traps
  • stream protection: buffer strips
The CEP Technical Report No. 32 can be downloaded from the following web address (due to server issues, downloading is not always possible):

Coral restoration helps damaged reefs

Threatened staghorn and elkhorn coral colonies are getting important help from a dedicated conservationist in the Florida Keys. Ken Nedimyer, the driving force behind the Coral Restoration Foundation, has developed his own reef restoration techniques since the year 2000. Nedimyer grows corals on his shallow-water underwater farm off Key Largo. From the farm the corals are taken to  surrounding reefs, where they are transplanted in areas which suffer from loss of live cover.
Professional conservation institutions and organisations like NOAA, The Nature Conservancy, Mote Marine Laboratory, Nova Southeastern University and The Rosenstiel School of Marine and Atmospheric Science of the University of Miami have been so impressed that they have joined the work.
The current design is based on Nedimyer’s learning through trial and error. The cooperation with the partners has resulted in seven other nurseries following that method. Two of the new farms are located outside the Florida Keys, i.e. in St.Croix and St.Thomas.
One Florida reef which got crucial help from Nedimeyer had been damaged by a freight ship grounding.  Farm-grown corals were used to replenish the suffering underwater communities. In a couple of years the new corals had become spawning colonies which were able to colonise the sea bottom in the natural manner.
Coral replanting is a promising way to help our threatened reefs.  Studies and experiments have been carried out not only in Florida but also in other parts of the world.  A lot of work still needs to be carried out in order to know the species best suited for farming and transplanting.
Nedimyer, who is a trained marine biologist, says he wants to improve his knowledge as to which corals grow faster than others and which ones are the most resilient to diseases and changes in water temperature.  Other conservationists remind us that climate change, ocean acidification, overfishing and sediment runoff from land remain as significant threats to coral communities around the world.  These pressures result in bleaching and other serious problems on the reefs, which need to become a global hot spot for conservation efforts.
More information on the Florida Keys coral restoration methods can be found here:

Coral Restoration Foundation

This Vimeo video highlights the Nedimyer reef restoration work: