BULLETIN: Suspected Harmful­ Algal Bloom around Tobago

Over the last few days, the Institute of Affairs (IMA) has received reports of fish kills at four sites along Tobago’s Atlantic coast – Delaford Bay, Roxborough, Lambeau Beach and on Flying Reef along Tobago’s south coast. Dead marine life was observed along beaches and in the water, mainly consisting of reef fish species such as parrotfish, snapper, butterflyfish, trumpetfish and other species including eels and octopuses. Simultaneously, reports of a possible “red tide” were reported in the same areas over the weekend. Divers observed large pockets of warm, reddish water extending to 50 feet along the Atlantic coast. This may be indicative of a possible harmful algal bloom (HAB).  

The IMA and the Department of Marine Resource and Fisheries are currently investigating the extent of the fish kills along the Atlantic coast. Further observations of the marine areas show that the red water may have dissipated, but fisherfolk are encouraged to report any further sightings of red water around Tobago and collect a water sample if possible. Given the small window of occurrence, it may be difficult to conclusively evaluate the cause of the fish kill.

According to Dr Rahanna Juman, Deputy Director of Research at IMA, “Ocean conditions around Tobago are exceptionally hot, and at the moment many of our coral reefs are currently bleaching. This thermal stress along with likely nutrient influx from the Orinoco can potentially drive harmful algal blooms events around the island.”

Here is some general information about Harmful Algal Blooms: 

What is a harmful algal bloom (HABs)?

According to the National Oceanographic and Atmospheric Administration (NOAA), harmful algal blooms occur when colonies of algae — simple plants that live in the sea and freshwater — grow out of control and some may produce toxins that have harmful effects on people, fish, shellfish, marine mammals and birds. 

What causes harmful algal blooms?

There are multiple causes of HABs. In some places, HABs occur naturally but human activities often intensify the blooms. Typically, marine environments that occur close to areas of high nutrient discharge (from farms, golf courses, and residential areas) are prone to experiencing HABS. However, HABs can also occur in marine environments under unusually calm conditions with less water movement and elevated temperatures, especially if there is an injection of nutrients. HABs are harmful in many ways (1) the type of algae that blooms may be toxic to small marine organisms, especially in high concentrations or (2) algae cause oxygen depletion and suffocate marine life especially in marine areas with low circulation. 

How do harmful algal blooms affect us?

This is dependent on the type of algal bloom. In scenarios where the algae are toxic, the algae may impact on fish species that we consume, and under extreme circumstances (present over a large area) may cause irritation and illness in land animals and humans. 

What is a fish kill?

A fish kill is the significant and sudden death of fish and other marine organisms in a clearly defined area. 

What precautions should be taken?

Fish washed ashore due to a fish kill are not safe to eat. Fishing and diving should be avoided in areas of HABs.

What to do if you observe a fish kill?

Do not touch or handle the dead fish. Record (i) the location of the event, (ii) the number of fish observed, (iii) fish species (if possible) and (iv) pictures of the fish. Submit your observations to imadirector@ima.gov.tt and marinepark08@gmail.com. 

Photos of fish kill along Delaford and Lambeau. Photos courtesy –Laura Marie-Ashby (Delaford) and Daniella Rodriguez (Lambeau).