Chemical contaminants (metals and PAHs) in the Caroni Swamp, Trinidad
The Caroni Swamp, the largest mangrove swamp in Trinidad and Tobago, is recognized as wetland of international importance (RAMSAR site). Photo credit: La Daana K. Kanhai.
Mangrove swamps are important ecosystems that straddle the marine and terrestrial environment. Due to their unique location, they are susceptible to contaminants originating from both environments. The Caroni Swamp is the largest mangrove swamp in Trinidad and Tobago and it is the second largest wetland in the country. This unique ecosystem is a key contributor of numerous provisioning, regulating, supporting and cultural ecosystem services.
During my MPhil, I had the opportunity to work within this spectacular RAMSAR site. My research was focused on assessing the presence of chemical contaminants in the sediments, oysters (Crassostrea rhizophorae) and catfish (Cathorops spixii). I was particularly interested in determining whether contaminants such as metals and polycyclic aromatic hydrocarbons (PAHs) were present in the various environmental compartments of the Caroni Swamp and whether they posed a threat to human health and ecosystem well-being.
Seasonal Sampling
In order to account for seasonality, sampling in the Caroni Swamp occurred in both the dry season (January to May) and the wet season (June to December). Photo credit: La Daana K. Kanhai.
Mangrove oysters (Crassostrea rhizophorae)
These estuarine organisms filter large volumes of water in order to be able to obtain their food. Due to the fact that humans consume oysters from certain areas of the Caroni Swamp, the tissues of these estuarine organisms were analysed for metals and PAHs in order to determine the threats posed to human health. Photo credit: La Daana K. Kanhai.
Madamango sea catfish (Cathorops spixii)
This species of fish is regarded as being benthophagic and has an intrinsic association with the sediment environmental compartment. PAH levels were assessed in the tissues of these estuarine organisms in order to determine the threat that such contaminants could pose to human health. Photo credit: La Daana K. Kanhai.
Sediment sampling
Depending on the depth of the water, either Ekman or Petite Ponar Grabs were used to sample sediments at various locations in the Caroni Swamp. Sediments were analysed for both metal and PAHs. The threats posed by these chemical contaminants to sediment-dwelling organisms were assessed. Photo credit: La Daana K. Kanhai.
Nariva Swamp
In addition to sampling in the Caroni Swamp, there was one reference site located in the Nariva Swamp (Trinidad and Tobago’s largest wetland). Although this wetland contains some mangrove, it is a completely different ecosystem that is located along the east coast of Trinidad. Photo credit: La Daana K. Kanhai.
Analytical techniques
While sampling was undoubtedly one of the most enjoyable parts of my MPhil, once a sample was collected, it had to be processed and analysed using relevant analytical techniques. For my MPhil, I used a Flame Atomic Absorption Spectrometer (FAAS) to analyse samples for metals and a GC-FID (Gas Chromatograph with a Flame Ionization Detector) and GC-MS (Gas Chromatograph with a Mass Spectrometer) to analyse samples for PAHs. Photo credit: La Daana K. Kanhai.
A view of the Caroni Swamp in 2009. Photo credit: La Daana K. Kanhai.