Author: Aaron

Researcher at the Smithsonian Tropical Research Institute, Panama

Historical hypoxia

Bocas del Toro in Caribbean Panama is one of the few regions in the tropics that have been demonstrated to experience widespread hypoxia, or lack of oxygen in the water, which kills pretty much everything on the reefs except slime and jellyfish.

Andrew Altieri and colleagues documented the process. They leave us with the sobering conclusion that hypoxic events like these are almost certainly more widespread in tropical reefs around the world but are drastically under-documented because most marine scientists don’t live in the tropics and so tend to miss them because they are short lived. When scientists do find a dead reef, it’s not usually hypoxia that they blame.

One important question that is left hanging is how frequent were such events in the past? Are they increasing in frequency as eutrophication increases and the water warms, or have they been a natural process on these reefs for millennia?

We have begun a project to try and explore this question by taking reef cores and looking for tell tale signs of hypoxic events in the past.

We just returned from Bocas del Toro where we extracted 6 reef cores. We were joined by STRI post-docs Noelle Lucey, Jarrod Scoot and Blanca Figuerola, along with STRI intern Ramiro Solis. Blanca is leading the project and will be extracting material from the cores and conducting faunal analysis and stable isotope analyses with Ethan Grossman in Texas A&M.

Here the O’Dea Lab team extract a 3m-long core from a shallow Porites reef in Cayo Adriana, Bocas del Toro.

The project is funded by SENACYT

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¿A dónde se fueron las playas blancas?

Llegué a Panamá por primera vez en 1998. En esta época era un joven estudiante y me atraía y fascinaba la vida marina en ambos lados del istmo. Era mi primera vez en las Américas y toda era una aventura. Sobreviví a tres cosas: a una disentería en Bocas del Toro, al atropello por un taxista en la ciudad de Panamá y a la caída de un coco sobre mi cabeza en Isla Grande, Provincia de Colón. Salí del país prometiendo nunca volver. Pero, como dije al principio, Panamá goza de una extraordinaria vida marina que cautiva al primer contacto con ella. No hace falta decir que ahora hace ya 16 años que vivo en Panamá con mi familia panameña.

En esa primera visita a Isla Grande, en la zona llamada Costa Arriba, me encontré con una exquisita extensión o lengua de arena blanca que iba desde la esquina suroeste de la isla a más de 150 metros hacia mar adentro. En esta época, buceé con una dinastía de peces brillantes; en la noche dormí sobre las blancas y suaves arenas de la playa, que imaginaba como una gran cama de harina. Hoy día, la playa se ha ido y no hay peces. ¿Qué ocurrió?

isla grande donde se fue la playa

La erosión de la playa es un proceso natural que ha ocurrido durante miles de años, en donde la arena es arrastrada por la acción de la lluvia o las olas, y es reemplazada por arena nueva, algunas veces más, algunas veces menos, por lo que la playa cambia de forma. Entonces, ¿por qué las arenas no regresaron a Isla Grande?

La respuesta es bastante interesante y algo desconcertante. Resulta que la suave harina blanca que nos encanta en nuestros pies en realidad está hecha de pequeños pedazos de coral que fueron comidos y luego defecados por animales como los peces loro. Sí! Las playas blancas del Caribe están hechas de excremento de peces. Algunos científicos han estimado que un solo pez loro puede producir una increíble tonelada de arena en un año. ¿Cómo lo midieron?, no les pregunté!

Por consiguiente, cuando se eliminan los peces loro del arrecife por la sobrepesca, llega un momento en que la arena erosionada es mayor que la arena que se forma, y la playa desaparece rápidamente. No más peces, no más playa. Agregue a eso el impacto de la contaminación y el calentamiento global sobre los corales, y tendremos una receta perfecta para el desastre.

El resultado no solo se muestra en imágenes de satélite, sino también en los recuerdos de quienes alguna vez disfrutaron de estas playas espectaculares. Las personas en las comunidades costeras desde Bocas del Toro hasta los Cayos de Guna Yala, están viendo desaparecer sus playas de arena blanca.

¿Cómo lo detenemos? En papel es sencillo: mejorar la salud de los corales y aumentar el número de peces loro; y las playas volverán. En la práctica, podemos buscar historias de éxito en otros lugares del caribe. En Punta Cana, República Dominicana, conocen el valor económico de sus playas de arenas blancas. Estimaron que con cada metro de playa perdida, el país pierde más de 300,000 dólares en ingresos del turismo cada año (Wielgus et al. 2010). En Punta Cana establecieron zonas dónde estaba prohibido pescar que permitieron la recuperación del pez loro y en consecuencia de los arrecifes. También, emprendieron una fuerte campaña para cultivar nuevos corales donde anteriormente existían. Es un modelo que tiene sentido desde el punto de vista comercial y podría aplicarse en cualquier parte del mundo si cuenta con una iniciativa correcta y regulada. Las playas de Panamá son un tesoro nacional que vale muchos millones de dólares en turismo. Son una protección frente al aumento del nivel del mar y a las tormentas como el infrecuente, pero mortal, huracán Otto. Brindan refugio a la vida marina y alimentan a las comunidades locales. Pero más que esto, se suman inexorablemente a la calidad de vida a todos.

Al saber cómo se forman estas playas podemos entender mejor porque se están perdiendo. Eso nos ayuda a tomar decisiones más efectivas que traerán de vuelta las hermosas playas del Caribe, para así apoyar la economía futura de las comunidades locales y el disfrute de todos.

 

Published here: https://www.prensa.com/_128d89d70

 

Get your optimism from the past

When we think about a “pristine” untouched ecosystem we often have a single, preconceived image in mind. It could be a grassland with thousands of bison, a thick tropical forest, or a coral reef teeming with fish and sharks. These places certainly existed, and in many cases are now lost or replaced by alternatives, but there has always been variation and that variation must have contributed to the rich mosaic of life.

It is this variation that we propose can help conservation, but first we need to describe it. If we can describe it we can do a better job of placing modern ecosystems into context. In this paper, published in Conservation Biology, BaselineCaribbean members discuss our ideas of how the fossil record can be used to redefine what should be considered “pristine” and the positive benefits of doing so for conservation.

Open Access available

O’Dea, A., M. Dillon, E., H. Altieri, A. and L. Lepore, M. (2017), Look to the past for an optimistic future. Conservation Biology. doi:10.1111/cobi.12997

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New expedition: Curaçao February 20th

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The Baseline Caribbean team is gearing up for another expedition, this time to the sparkling, cerulean seas of the Netherlands Antilles in the Southern Caribbean.

Reefs on these Dutch Islands are in relatively good shape when compared to the rest of the Caribbean. But what were they like in the past?

Anecdotal evidence suggests that sharks were once abundant around these islands, yet empirical data are desperately needed to guide management. Reef fish communities are overfished today, but by how much? When did coral communities begin to deteriorate, and did it depend on their proximity to historical settlements?

To get at these questions and more, we plan to collect nearly a ton of sediment from modern and fossil reefs along the southwest coast of Curaçao. We also hope to get the chance to explore Klein Curaçao — a 1.7-square-kilometer uninhabited island just southeast of its big sister and namesake.

Instead of reading about the results in a stale journal in two years’ time, experience science in action. Beginning February the 20th, join us with daily posts, photos, and short videos from the field on the Baseline Caribbean science blog.

This expedition builds on our previous exploits in Panama, Belize and the Dominican Republic. We see familiar faces return: Erin Dillon (who recently hightailed it to the McCauley Lab), faithful malacologist Felix Rodriguez and ring-leader Aaron O’Dea. We are also joined by some fresh blood in the form of fish ecologist and evolutionary biologist Michele Pierotti and STRI videographer extraordinaire  Ana Endara.

A huge Thank You to our supporters who will make it possible: The Caribbean Research and Management of Biodiversity field station (CARMABI) who kindly gave us a Research Prize, the Smithsonian Tropical Research Institute (STRI), and YOU! – the generous donors who contributed to our crowd-funding campaign. Stay tuned…!

 

 

 

 

When parrotfish abound the reef grows faster

 

Several years ago Katie Cramer, Dick Norris and I hatched a plan. We knew that the sediments on coral reefs preserved the robust teeth of fish and we guessed that the branching corals of the reef would hold it all in place. We just needed a way to extract the layers of reef sediments to reconstruct the history of fish communities on the reef.

Katie led the project with support from MarineGEO and Dick built a pushcore/vibracore hybrid, with which we managed to extract a good number of 3-4 metre long cores from coral reefs in Bocas del Toro, Panama.

Back at Scripps Katie led the troops to split the cores, take samples along them and extract the teeth from the matrix by acid digestion of the carbonate sediments. Sounds easy?

Then she had to identify what all these teeth were. Along with the team in Norris’ lab, and help from our lab in Panama, she built a reference collection of coral reef fish teeth, which turn out to be variable in shape, but on the whole extremely well-preserved over millennia.

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We needed to date the cores, that’s where Jian-xin Zhao at University of Queensland came in. There we were able to date small pieces of coral using the U-Th dating technique which gave really high-resolution dates, and more importantly showed that the chronology of the cores were intact – i.e. there had been no mixing up and down which would have ruined any attempt to explore changes through time.

Our cores from Bocas stretched back 3000 years or so, and one of the most abundant teeth that Katie found was the various teeth produced by parrotfish.

Using the dates of the samples to calculate reef accretion rates we discovered that as the reef was growing it did so at a faster rate when there were more parrotfishes. This results shows that the benefit of parrotfishes for the health of the reef is always high, not only in the degraded habitats of today but also on “near-pristine” reefs which were much less fished.

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The fossil record is a powerful tool to reveal ecological processes that have direct implications for conservation. And parrotfish conservation must be made a priority for the recovery and persistence of coral reefs.

 

Coring Caribbean reefs

Alongside our work examining the relative abundances of coral and mollusc skeletons, shark dermal denticles, sponge spicules and fish otoliths in large tracts of exposed mid-Holocene reefs, we have also been collaborating with Drs. Katie Cramer and Richard Norris (Scripps) to explore sequential changes in Caribbean reef ecosystems by extracting reef matrix cores in Belize and Bocas del Toro, Panama. We collected more than twenty 6m long aluminium cores from several lagoonal fringing reefs that capture reef ecosystem conditions going back the last couple of thousand years.

See more about the approach in this little video

The reefs at Samana – a modern comparison

We reached Samana, in the very northeast of the island of Hispañola. This natural bay was a 17th century pirate hangout. We are here because the site is very similar in geography to how the Enriquillo bay would have looked 7,000 years ago — open to the ocean to the east, very sheltered, flanked on either side by mountains, with high run-off and sedimentation. It is critical we make our fossil and modern samples as comparable as possible in order to measure changes over time. We are therefore sampling the sediments in the reef crests and the fore-reef of fringing reefs around the Bay — just as we did in the Enriquillo basin. We were very surprised to see healthy-looking staghorn coral (Acropora cervicornis) in this region. Four years ago it did not look like this.

A guide to collecting a bulk sample

A bulk sample simply means that there is as little bias as possible during collection. Instead of picking the most beautiful or well-preserved fossils from an outcrop, we take whole lumps of the sediment, which are then transported whole back to the lab in Panama for washing, picking and identification of the fossils. Only then will the bounty they yield be revealed.

This means we have to collect massive amounts of rock and sediment, but it’s the only way to provide a measure of the abundance of the many different organisms in an ecological way. This ecological approach to paleontology is critical for we want to know what the structure of the whole ecosystem was like.

Sped up from 15 minutes to a minute and a half, the video shows Erin and Aaron collecting a 10kg bulk sample of 7000 year old reef sediments in the Enriquillo basin. All the coral, mollusks, fish otoliths, sponge spicules and shark dermal denticles will be picked from these to help reconstruct the ecosystems of the past.

Beautiful forms and incredible functions

Dermal denticles are small scales that line the skin of sharks. Denticles have a similar composition to teeth, forming a strong and streamlined suit of armour. If you were to pet a shark, its skin would feel smooth in one direction and rough like sandpaper in the other direction. This is due to the serrated peaks of the layer of overlapping denticles that cover the shark’s body.

Denticles are continually shed by sharks and accumulate in marine sediments, where we can find them beautifully preserved – in both on modern and fossil reefs.

shark denticle family diagram (blog body)

Denticles display a diversity of forms and play a variety of functions. For example, fast predatory sharks – such as hammerhead and requiem sharks – are covered almost entirely by thin, highly ridged denticles that reduce drag and make the shark more hydrodynamic. This type of denticle served as inspiration for the controversial Speedo swimsuits in the 2008 Beijing Olympics.

In contrast, demersal (bottom-dwelling) sharks are have thicker, smooth denticles that resemble pebbles. These protect against abrasion, given that their owners live along rocky, sandy, or coralline substrates.

Other demersal or schooling sharks possess spiny, defensive denticles that are thought to discourage the settlement of parasites and epibionts on the skin.

To make sense of the different types of denticle we had to first build a reference collection of modern denticles from museum collections of sharks. That way, when we find a denticle in a fossil reef we have some idea of which type of shark it could have come from and the way the shark lived.

One big problem is that denticles are rare and that is why we have been collecting so many hundreds of kilograms of fossil and modern reef sediments. Once back in the lab, we will dissolve the calcium carbonate that forms much of the sediment in our bulk sample bags using a process pioneered in Richard Norris’ lab. Picking them is arduous for they are usually less than half a millimetre in size. We hope to find enough to be able to rigorously compare the assemblages of denticles across our sites.

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Erin and Félix carry off heavy bags of samples for analysis.

If we get lucky, the denticles from modern Caribbean reefs could tell us about the presence of sharks in areas where fish surveys have failed to report them because of their rarity, yet dive shops and fishermen confirm their presence.

Even more exciting is the possibility that we will uncover enough denticles from the fossil reefs to be able to reconstruct shark populations 7000 years ago, before major human impact.

It’s hard work but we hope that these massive bulk bags of reef sediment will uncover enough tiny denticles to help paint a picture of shark communities past and present.

DILLONE_320_Fig 1 (body)_Great hammerhead_body_275x, Erin Dillon & Jorge Ceballos

 

 

Off to dig at Punta Cana

STRI pre-doctoral fellow Erin Dillon talks about the start of the sampling day at Punta Cana and how she hopes to discover shark dermal denticles in the reef sediments.

This region is massively developed tourist destination with its own private airport. Few sharks are officially reported on the reefs here but fisherman claim to catch hammerheads. If there are many hammerheads that are avoiding surveys the sediments in the reef should preserve their denticles…

Photos to follow soon

The fall and rise of Lake Enriquillo

One of the problems of trying to work out what coral reefs were like before human impact is that the reefs of the past are underneath the reefs of today.

One way to get to these reefs is by coring through the reef and producing a timeline of the coral reef as it grew. This is great for small and common fossils, such as molluscs and fish teeth, but the core itself is only 10cm in diameter and so very large animals (such as large coral heads) and very rare fossils (such as shark dermal denticles) are not captured. This means the complexity of the coral reefs is often missed.

One way to get to the whole reefs of the past, and capture the full variation and natural complexity of the reefs, is wait for an excavation to dig out and drain the modern reef, exposing the fossil reef underneath. In Bocas del Toro we had the good fortune to be able to explore one such massive excavation – see the video here.

The Enriquillo Lake in the Dominican Republic was originally a marine embayment, flanked by hills on either side and open to the ocean to the east. The coral reefs fringing these hills are those we are studying. Around 4,000 years the River Yaqui del Sur deposited a large delta right in front of the entrance to the bay, sealing it off from the open sea. Bbecause the area sits in a rain shadow, evaporation exceeds precipitation and the lake began to dry out. Eventually the lake level dropped to below 40m below sea level and became hypersaline. With the reefs exposed above the lake level, storm channels started to cut through the ancient reefs and it is in these small canyons that we get to see the incredible full sections of coral reefs that grew between 6,000 and 9,000 years ago.

Recently, the lake level has started to rise again and nobody is sure why. Many theories have been proposed from climate change to natural variability. Whatever the cause, the impact on the local communities around the lake is devastating as it eats up the little arable land they have, and drowning the roads that encircle the lake. The government seems to be taking steps forwards helping and have started building a new road 20m or so above the lake level.

The problem for us is that if the lake continues to rise at the steep rate of recent years, within a decade these spectacular fossil reefs could once again be under water, and unavailable for study.

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