Acid Test: The Global Challenge of Ocean Acidification

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Sacha at the entrance to Bel Torente

With large volumes of fresh cold water and spewing out of the caves, we may not be able to swim up any of the known cave passages, but these conditions offer a rare opportunity. There are stretches of the coast that to date have no known cave passages, but where Rick and Toddy both believe there must be. So the plan is…  we go out over the next few days and do rapid surveys of the coast – on breathhold/snorkelling initially, and bringing diving gear and scooters for deeper and more detailed searches where it looks like there might be a passage.  We will try to cover a significant stretch of the coast from in the water (see the attached photo), looking for signs of large, potentially diveable passages.  The coastal cliffs that can be hundreds of metres high continue below water as drop-offs into the blue. Thousands of species of marine life cling to the honey-combed rock so it’ll be a beautiful snorkel whether or not we find anything.

The tell-tale signs of possible diveable cave systems to look out for are:

-          A sudden drop in the temperature of the water. The ocean around here is about 24 C at the moment, but the freshwater in the caves about 16-17 degrees.

-          The hazy heatwave effect caused where the 2 waters of different density (the cold freshwater and the warmer seawater) mix. This is obvious as the oceans around here have stunning visibility so any disturbance should not be hard to spot.

-          Any sign of murky water

-          The formations visible in the rock both under and above the water. Caves are often found where there is a large fault which may be visible in the cliff faces above the water.

All seem very confident that we will be able to find new systems. A word of warning: with so many amazing caves and caverns and areas that are relatively unexplored, if you have any interest in visiting the world below – whether as a tourist or as a more intrepid tech diving junkie - don’t come to Sardinia or you may just get hooked.

Bruno, Beardy, Rick Stanton

The entrance is an unassuming small hole in the wall about 5

Photo by Jim Rozzy of aragonite formations

metres below the surface. I have sworn to give away no details of the name or where it is, but today we visited what is, according to ‘Beardy’, the most stunningly decorated cave of the 2000 cave he has visited or explored to date.

 We grabbed a tank each and followed Bruno in, laying a line as he went. We were to be very thankful for that line on the way out.

We followed the line in through the hole and along a few metres to a more open chamber. Looking up from there we could see the passage leads to an air space. Ascending we emerged into a small pool with smooth, metre-high walls and a large stalactite protruding down into it. We removed tanks and BCs and left them here. Some rocks at one end offered a way out and into a passage completely lined with very smooth, pale brown clay…mud. Grovelling single file we followed Bruno on hands, knees and then writhing on our fronts further down the passage, getting completely smothered in mud in the process. Holding my big wide-beam filming torch light in the hand became impossible so I gripped the strap in my teeth, mud now between my teeth also! My first sight of a formation was the one my head almost collided with. From then on thankfully I had both Rick and Beardy keeping half an eye on my every move as we squeezed ourselves through into a couple of further chambers decorated in every direction with stunning formations of aragonite. There was white fairy floss, flowers, spirals, tubes, filaments growing and twisting an various directions, and all of white aragonite growing slowly over hundreds of years. You can’t help feel seriously out of place sitting, filthy with mud surrounded by these stunning white formations.

Rick Stanton and Beardy (background) checking water clarity

If you can manage to look past the formations, the fossils of beings buried millions of years ago pattern the rock walls they grow from.

After marvelling for a while we wriggle back out and to the pool we entered from. As we jump in, one by one, our muddied bodies turn the water brown. Now with zero visibility we can no longer see the way out and must head down with one hand forming a tight circle with fingers and thumb around that guideline laid on the way in. By the bottom of that chimney the water clears again and you can see the bright blue of the exit back into open ocean…

This was just one of the places we visited on a day spent looking at the entrances to some of the caves and exploring a few dry caves. We also stopped to look at the entrance to Bel Torente, the system Rick and Toddy are keen to push further and where the suspected remipede was spotted. Bad news – the outflow of fresh water is still strong. Good news – it is only slightly discoloured. Fingers remain crossed. See the video and photos.

When we caught up with Toddy that evening he had just returned from a reconnaissance trip down the coast in his RIB, checking out any change in the conditions in the caves. He smiled, welcomed us, brought out a round of beers and suggested we all sit down for pasta … big plates of warm, fresh, bouncy and comforting carbonara… were we about to get some bad news?

Thorsten 'Toddy' Walde

Then one of Toddy’s students let us have it “There were big brown mushrooms coming out of the ocean by the entrance to the caves… this is impossible!”   Ouch.

That immense volume of fresh water from all the storms is really churning up the silt and bringing in further run-off. The ‘big brown mushrooms’ are caused where the pressure of the water in the system is so great it is forcing the water out at the coast through a hole that is below sea level, forming a fountain. Toddy has never seen conditions like this. To his immense credit, he had geared up, dropped overboard and tried to swim into one of the caves with lower flow…just to make sure.  

It is certain is that the caves can’t be dived. For now. With no precedent we don’t know how long they will take to clear and predictions from locals have ranged from days to a couple of months. Fingers crossed.

Sacha

Around dawn the large boulders and steep, bare, limestone of the coastal cliffs and distant jagged peaks appears out of the mist. This rock is what draws cavers and climbers to Sardinia. Where it isn’t bare, the land is covered in a very dense green scrub that would be impenetrable without machinery. This dense scrub may be one of the reasons that many underground areas remain completely unexplored.

At the port, signs of a once healthy but now struggling fish and seafood industry are pushed to one side to accommodate a busy industrial port and the bulk of the enormous vessel we are arriving on.

As we begin the drive South to Cala Gonone, the extreme nature of the recent storms becomes clear: collapsed roads, road tunnels with debris caught around the roof and mud drying on the walls, where they have clearly been temporary rivers no more than a couple of days ago and are undergoing urgent repairs. Normally a dry place the local services are completely unprepared for dealing with this kind of incident but are hard at it. Wide paths of flattened trees wind their way across the countryside where rivers have broken their banks with force. The reality of the potential impact that this volume of water, falling right across the island and flowing underground, could have on the conditions in the caves and on this entire expedition are becoming brutally apparent. Local ontact and tech diving instructor Toddy has gone quiet in recent days which is worrying…no doubt he will have more news for us this evening…