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Marine Life & Conservation

The Yucatan Cenotes – A paradise under threat from tourism



An interview with Sam Meacham by Jeff Goodman

A few years ago I made a film for the BBC called ‘Secrets of the Maya Underworld’ and was about the Cenotes and forests of the Yucatan Peninsula, Mexico. Previously I had always promised myself not to ever cave dive as I had a fear of being lost or trapped far underground with no escape route. Then a few very good friends told me of the Cenotes and the incredible wildlife that was associated with them. I had to see for myself.

Yucatan-Cenotes-2It was then I met Sam Meacham, an American living near Cancun. He had been exploring the caves and passageways of the Yucatan Peninsula for the previous 18 years and now to date has discovered with other divers 252 known caves and cave systems in that region with a total of 1,103.3 km or 685.5 miles of surveyed passageway between them.  Two of the five longest caves on the planet Sistema Sac Actun and Sistema Ox Bel Ha are found close to the town of Tulum.

The Yucatán Peninsula was once a shallow coral reef and now over a few million years has become a porous limestone shelf covered with forest and wildlife. There are no visible rivers; all the fresh water rivers are underground. Being porous, caverns and caves formed where the fresh water collects – hence the Cenotes or water sinkholes.

Recently, the Cenotes have become a great dive destination and the eastern Yucatan coastline an ever developing tourist area for sun worshipers and beach goers. The seemingly uncontrolled developments are taking their toll on this unique ecosystem.

I recently got back in touch with Sam to see if things were improving.

Jeff:  Can you just tell us exactly what the Cenotes are and what is so special about them?

Sam: Cenotes are karst sinkholes that occur in Mexico’s Yucatan Peninsula.  The Cenotes are windows into the freshwater aquifer of the region and the entrances to the very complex flooded solution cave systems along the Caribbean coastline.

Yucatan-Cenotes-3Jeff:  The underground water systems give life to the forests above where wildlife is obvious to find, but is there life in the caves as well?

Sam: Most people think of the cave environment as a very sterile place.  In fact, there are over 40 life forms so far identified that live in the dark recesses of these caves.  The majority are crustaceans and they are all considered extremeophiles because of the conditions they live in.  The Cenotes themselves are also magnets for life; this includes a number of freshwater tropical fish species, crocodiles, turtles in the water and birds and mammals (including jaguars) at the surface.

Jeff: How long has man know about the Cenotes?

Sam: There is growing evidence that the caves and Cenotes were accessed by humans during the last ice age, which was 8000-10000 years ago.

Jeff: Did the Maya have any idea about the complexity of the underground waterways?

Sam:  It is hard to say if the Maya realized that some of the Cenotes were connected by the intricate and complex cave systems. Many of the underground rivers flow out to the sea in very impressive upwellings; perhaps they put two and two together when they observed this.  It was not until the 1980’s that cave divers really began to probe the depths of the Cenotes and really revealed just how complex and extensive they were.

Jeff: Are the Cenotes and reliant ecosystems in any threat now due to the commercial tourist developments?Yucatan-Cenotes-4

Sam: There is a very real and continuing threat from the development of the tourism industry along the coastline.  Karst landscapes like the Yucatan are very susceptible to contaminants that leach through the porous limestone and into the aquifer.

Jeff:  What are the main issues?

Sam: The main issues we face are contamination from solid waste (garbage) and sewage.  Once contaminants hit the aquifer there is the high potential for them to be transported through cave conduits and out to the Caribbean Sea.  High concentrations of contaminants cause algal blooms that cover the Mesoamerican Reef and kills the corals.  If we lose the reef, we lose the protection to the beaches.  If the beaches erode, where will the tourists go?  Effectively, we risk killing the goose that lays the golden egg.

Jeff:  Is anyone listening to the conservation needs of the area or is commercialism taking its full toll?Yucatan-Cenotes-5

Sam: Well, I think worldwide conservation efforts are always facing an uphill battle and this area is no exception.  But I do think there is a great deal more awareness about the existence and importance of the flooded caves.  My personal belief is that the outreach and education about the caves is the only way we can engage the public and effect change.

Jeff:  As Divers, how can we help preserve this unique ecosystem?

Sam: If you dive in the Cenotes, it is a great opportunity to perfect your skills particularly your buoyancy and trim.  Really, any time you go diving you should be perfecting your skills.  We, as divers, are privileged visitors to the underwater environment and must make every effort to protect it.

Jeff:  If readers want to learn more where can they get further information?

Sam:  Here are a few websites:

Jeff is a multiple award winning, freelance TV cameraman/film maker and author. Having made both terrestrial and marine films, it is the world's oceans and their conservation that hold his passion with over 10.000 dives in his career. Having filmed for international television companies around the world and author of two books on underwater filming, Jeff is Author/Programme Specialist for the 'Underwater Action Camera' course for the RAID training agency. Jeff has experienced the rapid advances in technology for diving as well as camera equipment and has also experienced much of our planet’s marine life, witnessing, first hand, many of the changes that have occurred to the wildlife and environment during that time. Jeff runs bespoke underwater video and editing workshops for the complete beginner up to the budding professional.


The life of a Great White Shark



Great White Shark

The great white shark, known scientifically as Carcharodon carcharias, embodies the apex predator of the ocean. This majestic creature’s life is a testament to survival, adaptability, and the intricate balance of the marine ecosystem.

Born in the waters off coastal regions, a great white shark begins its life as a pup within the safety of nurseries, typically found in warm, shallow waters. The pups, measuring around 5 feet in length at birth, are immediately equipped with an innate instinct for survival.

Great White Shark

As they grow, great whites embark on a journey, venturing into deeper and cooler waters, often covering vast distances across the ocean. These apex predators are perfectly adapted hunters, relying on their impressive senses to detect prey. Their acute sense of smell, aided by specialized sensory organs known as ampullae of Lorenzini, helps detect the faintest traces of blood in the water from several miles away.

Feeding primarily on seals, sea lions, and other marine mammals, great whites are known for their powerful jaws lined with rows of razor-sharp teeth. Their hunting techniques often involve stealth, utilizing their streamlined bodies to approach prey from below and striking with incredible speed and force.

Great White Shark

Despite their fearsome reputation, great whites play a crucial role in maintaining the health of marine ecosystems. As top predators, they help regulate the population of prey species, preventing overpopulation that could disrupt the balance of the food chain.

Reproduction among great white sharks is a slow and careful process. Females reach sexual maturity between 12 and 18 years of age, while males mature earlier, around 9 to 10 years old. Mating occurs through complex courtship rituals, with females giving birth to a small number of live pups after a gestation period of about 12 to 18 months.

Great White Shark

However, the life of a great white shark is not without challenges. Human activities, including overfishing, pollution, and habitat destruction, pose significant threats to their population. Additionally, despite their formidable presence, great whites are vulnerable and face dangers from entanglement in fishing gear and accidental bycatch.

Despite these challenges, great white sharks continue to inspire awe and fascination among scientists and nature enthusiasts. Their presence in the ocean serves as a reminder of the delicate balance and interconnectedness of marine life, emphasizing the need for conservation efforts to protect these magnificent creatures for future generations to admire and study.

Want to learn more about sharks? Visit The Shark Trust website:


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Marine Life & Conservation

Book Review: Sea Mammals



Sea Mammals: The Past and Present Lives of Our Oceans’ Cornerstone Species by Annalisa Berta

This is a book packed with information about some of the most iconic and charismatic marine species. I have a particular soft spot for the pinnipeds, seals and sea lions, due to some incredible diving encounters over the years. So these were the pages I first turned to.

Once picked up this book is hard to put down. Polar Bears, Narwhal, Sea Otters, manatees, whales and dolphins adorn the pages with beautiful photographs and illustrations. Each turn of the page lures you in to discover more about a species you love, one you want to learn more about, some you have never heard of and even includes the details of fascinating animals that are sadly now extinct.

I think what I love most about this book is how it is organised. Rather than simply lump the animals into taxonomic groupings, they are put into chapters that tell you a story about them. Whether it is the story of their evolution, how they were discovered, their biology, behaviour or need for conservation. Once you have decided on an animal to delve deeper into, each species has its own story, as well as key information about size, diet, distribution, habitat and conservation status.

There is plenty to enjoy in this delightful book. Plenty to learn too. As the cold dark nights draw in, I can see myself delving into this book time and time again. This is a perfect gift for anyone that loves the ocean and its inhabitants. Or just treat yourself.

What the publisher says:

From the gregarious sea otter and playful dolphins to the sociable narwhal and iconic polar bear, sea mammals are a large, diverse, and increasingly precious group. In this book, Annalisa Berta, a leading expert on sea mammals and their evolution, presents an engaging and richly illustrated introduction to past and present species of these remarkable creatures, from the blue whale and the northern fur seal to the extinct giant sperm whale, aquatic sloth, and walking sea cow.

The book features more than 50 individual species profiles, themed chapters, stunning photographs, and specially commissioned paleo-illustrations of extinct species. It presents detailed accounts of these mammals’ evolutionary path, anatomy, behavior, habitats, and conservation. And because these are key species that complete many food chains and have the widest influence of all sea life, the book also offers insights into a broad variety of marine worlds today and in the future.

About the Author:

Annalisa Berta is professor emerita of biology at San Diego State University. A specialist in the anatomy and evolutionary biology of marine mammals, especially baleen whales, she formally described a skeleton of the early pinniped Enaliarctos. She is the author of Return to the Sea: The Life and Evolutionary Times of Marine Mammals and the editor of the award-winning Whales, Dolphins, and Porpoises: A Natural History and Species Guide.

Book Details

Publisher: Princeton University Press


Price: £25

ISBN: 9780691236643

Published: 26th September, 2023

Pages: 224

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