Where are Barbados' West Coast Sea Urchins?

"Be careful fuh dem cobblers!", my uncles would warn me as a child walking on the sea rocks. Cobblers or black sea urchins, relatives of starfish, are identified by their long, intimidating spines. They are extremely painful to step on, so I am extra aware of looking out for them— childhood memories of trying to get spines out of my feet. 

So while watching video footage of samples from a reef system on the west coast of Barbados, which span eleven months, it was odd to see no signs of sea urchin. Neither do we recall having to avoid them during deployment from shoreline rocks.

Our A.I. Scylla processes video footage. It determines reef metrics that give insights into the reef health and distribution of crucial reef species parrotfish, grunts, tangs, trumpetfish, to name a few. Human eyes hardly view video footage unless there is an anomaly in the data or we want to use the footage for R.E.E.F., our episodic underwater shorts. 

In our four sample surveys of the Vauxhall, Holetown area, we have no observations of sea urchin. We took surveys during:

• October 2020, post covid lockdown and reduced activity, from 0 to 4.5 m.

• April 2021, post volcanic ashfall and covid lockdown, from 0 to 3.5m.

• May 2021, post relaxed covid protocols, from 0 to 4.5m. 

• August 2021, post increased tourist activity, from 0 to 4.5m.

The area covered in each survey was approximate 20,000 square metres observed between 10:00 - 11:00 and 16:00 - 17:00 Atlantic Standard Time. The average water temperature of the surveys ranged from 28 to 30 Celsius, and the representative image dataset consists of approximately 25,000 images. We have no direct data on salinity or pH. 

Sea urchins help to clear algal growth to make space for new coral to attach. They are an essential part of the reef ecosystem, especially given the decreased populations of herbivorous fish. 

We should mention that sea urchins are present in the video data of the Carlisle Bay survey taken in October 2020. That survey is still under analysis.

"Be careful fuh dem cobblers!"

A Barbadian beach explorer warning.