Discovering a glowing ocean near Cape Town

Early in February, my Facebook home page was alive with posts about a weird but natural phenomenon that was happening in the coastal waters close to False Bay along the Cape coastline. There had been a bloom of bioluminescent plankton, and at night, the water was shining turquoise blue!

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Now maybe it’s an indication of the kinds of people I am friends with on Facebook but news of this phenomenon was creating great excitement, with photos being shared around, comments flying and a few late night road trips being planned. Bevan and I were quick to jump in on the action, and planned an after-dark excursion to Kogel Bay in between Gordons Bay and Rooi-Els to try to see this glowing ocean for ourselves.

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Oceans of life

As someone who is interested in the marine environment and used to KwaZulu-Natal’s ocean, the Cape’s coastal waters are new and exciting. They are cold and nutrient rich. These nutrients support a whole new diversity of plant and animal life and drive large fisheries, including the sardine fishery on the Agulhas Bank. Forests of kelp dance along the rocky coastline, and large flocks of gulls and cormorants are common sights close to shore. The oceans in the Cape are alive!

Sometimes conditions are just right to encourage blooms of phytoplankton; a high availability of nutrients and plenty of light can stimulate growth and lead to a rapid accumulation in concentration of these plant cells. A planktonic dinoflagellate called Noctiluca scintillans feeds on phytoplankton and with such an abundance of food, its numbers also explode. During the day, the coastal waters are tinged red but at night, in areas where the water is turbulent or disturbed by breaking waves these tiny creatures emit a ghostly blue colour. In sufficient numbers, they can make entire sections of the coastline glow eerily and oh so beautifully. This glowing ocean is what the Facebook excitement was all about, and this was the reason for our late night mission!

Bioluminescent plankton glowing ocean
The bioluminescent plankton is most visible at night in areas where the water is disturbed

Searching for a glowing ocean

It’s not often that you head out for the beach at 6pm, but that is exactly what we did. The latest reports had shown that the bloom was close to Kogel Bay, just past Gordons Bay, and so we timed our departure from Cape Town to coincide with sunset at the coast. Apart from the camera gear, we were armed with a flask and some rusks – essential fuel for late night adventurers!

Night shots over Cape Town
Entertaining ourselves with night shots of Cape Town’s lights across False Bay while we waited for the first glimpse of bioluminescence

The difficult thing about natural phenomena like this plankton bloom is that they are unpredictable. Just because there had been reports of a glowing ocean a night or two before didn’t mean that the bioluminescence would still be around for us. And so, having arrived and selected our viewing spot, we waited for darkness and hopefully the first pale glow…

And we waited, and waited… And drove further along the coast… And then back up it… And then suddenly we saw it – a glimpse of a ghost wave breaking on the pebbly beach. We pulled Thomas into a parking lot that led down to a rocky point and moved as quickly as we could safely carry our camera gear over the rocks towards the shoreline.

The Kogel Bay Coastline
The first glimpse of bioluminescence on the Kogel Bay coastline

Into a ghostly world

The only way that I can describe what we saw is ethereal, magical and dreamlike. Turbulence in the water agitates the plankton and causes it to bioluminesce, and so set against a dark backdrop of calm deeper water, luminous blue waves raced down the point or crashed spectacularly into the rocky point. It was the kind of pale, ghostly sight where it felt like the harder you looked the less well you could see it, and so the best way to take it in was to enter a dreamlike state yourself.

Not surprisingly, the glowing ocean was hard to photograph. The light emitted by the plankton was very dim and only with a high ISO setting and very long exposure was it even possible to begin to capture a bit of what we were witnessing.

After a few relatively satisfactory attempts, we put the cameras aside and began to play.

We threw pebbles into the rock pools and laughed at the explosion of blue. Our fingers traced paths of fairy dust across the water’s surface, and we watched as some mythical creature swam through a rock pool, giving itself away as it stirred up a starry trail behind it. It was all too incredible to be real, and the dreamlike world around us only made us feel even more transported.

Bevan aggitating the bioluminescent plankton
Bevan creating trails of fairy dust in the water

Breaking the spell

The howling wind and light drizzle that started to fall just after midnight put a rather chilly end to our time on the beach and we retreated into the sturdy shelter of Thomas for a quick cup of coffee and a rusk to give us stamina for the drive home.

Although Noctiluca scintillans is a red tide organism, I did not hear of any reports of fish or invertebrate kills along the coastline. Perhaps the bloom wasn’t large enough to threaten the coastal marine life. In any case, a few days later and the bloom was gone. Facebook quietened down and I had to be satisfied with reliving the magical evening through the small amount of footage we had been able to capture.

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  1. Are there any bioluminescent watch groups? Would be superb as we don’t live close to yhe coast, but would be up for night time roadtrips if we know of a spotting

    1. Hi Ansuli. We got quite lucky in that we spotted the red plankton during the day time, so once we knew it was in the area it was quite easy to go back to the same place at night. I’ll ask around and see if there are any spotting groups, but off the top of my head I can’t think of any.

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