Algal toxin profiles in Nigerian coastal waters (Gulf of Guinea) using passive sampling and liquid chromatography coupled to mass spectrometry

Abstract

Algal toxins may accumulate in fish and shellfish and thus cause poisoning in consumers of seafood. Such toxins and the algae producing them are regularly surveyed in many countries, including Europe, North America, Japan and others. However, very little is known regards the occurrence of such algae and their toxins in most African countries. This paper reports on a survey of phytoplankton and algal toxins in Nigerian coastal waters. Seawater samples were obtained from four sites for phytoplankton identification, on three occasions between the middle of October 2014 and the end of February 2015 (Bar Beach and Lekki in Lagos State, Port Harcourt in Rivers State and Uyo in Akwa Ibom State). The phytoplankton community was generally dominated by diatoms and cyanobacteria; however several species of dinoflagellates were also identified: Dinophysis caudata, Lingulodinium polyedrum and two benthic species of Prorocentrum. Passive samplers (containing Diaion(®) HP-20 resin) were deployed for several 1-week periods on the same four sites to obtain profiles of algal toxins present in the seawater. Quantifiable amounts of okadaic acid (OA) and pectenotoxin 2 (PTX2), as well as traces of dinophysistoxin 1 (DTX1) were detected at several sites. Highest concentrations (60 ng OA g(-1) HP-20 resin) were found at Lekki and Bar Beach stations, which also had the highest salinities. Non-targeted analysis using full-scan high resolution mass spectrometry showed that algal metabolites differed from site to site and for different sampling occasions. Screening against a marine natural products database indicated the potential presence of cyanobacterial compounds in the water column, which was also consistent with phytoplankton analysis. During this study, the occurrence of the marine dinoflagellate toxins OA and PTX2 has been demonstrated in coastal waters of Nigeria, despite unfavourable environmental conditions, with regards to the low salinities measured. Hence shellfish samples should be monitored in future to assess the risk for public health through accumulation of such toxins in seafood.

Amnesic Shellfish Poisoning (ASP) and Paralytic Shellfish Poisoning (PSP) in Nigerian Coast, Gulf of Guinea

“…This may not be unconnected with the higher prevalence of toxin-producing species generally observed in the SW in contrast to the SS locations . Earlier study by Zendong et al (2016) recorded substantial quantities of specific marine algal biotoxins in SW Lekki and Bar beach relative to SS Rivers and Akwa Ibom. The SW coastal Nigeria is reckoned to be of more elevated salinity than the SS (Zendong et al, 2016) with greater preponderance for toxic dinoflagellates to survive (Delmas et al, 1992;Zendong et al, 2016) whereas the salinity of SS is diluted by the Niger delta inflows.…”

Solid Phase Adsorption Toxin Tracking (SPATT) Technology for the Monitoring of Aquatic Toxins: A Review

“…OA, DTX-1, PTX-2, PTX-2sa and 7-epi-PTX-2sa were detected in the Yellow Sea in China (maximum 165, 56, 107 and 50 ng/g HP20 resin for OA, DTX-1, PTX-2 and PTX2-sa + 7-epi-PTX-2sa, respectively) [ 49 , 52 ]. Finally, OA, DTX1, PTX2 and PTX2sa were detected in Nigerian coastal waters of Africa (Atlantic Ocean) (60 ng OA/g HP20 resin) [ 42 ] and in French coastal areas of the Mediterranean Sea (650, 120, 500, 100 ng/g HP20 resin, respectively) and Atlantic Ocean (130, 3, 1800, 160 ng/g HP20 resin, respectively) [ 23 ], where results also showed that toxin concentrations and profiles in SPATTs were dependent on the amount of resin used (0.3, 3, and 10 g of HP20 resin) and that SPATTs bags containing 3 g of resin appeared to be the best compromise.…”

“…To date, there is no general consensus in the literature about the optimal deployment time for SPATT devices in the field. In fact, passive samplers were generally deployed on a weekly basis [ 21 , 31 , 35 , 40 , 42 , 46 , 50 , 51 , 58 ], but sometimes, the time of deployment was reduced to few hours [ 32 , 37 , 47 , 52 , 53 ] or extended to a month [ 34 , 41 , 43 , 44 , 49 ]. So, the deployment duration varies and generally depends on the research or monitoring program design (e.g., short- or long-term monitoring, adsorbent substrate used, toxin targeted, …) together with the feasibility on the field (e.g., duration of the field mission, accessibility of the monitored area, hydrodynamism of the monitored area, …) [ 25 ].…”

“…They consist of a porous synthetic resin encased within an inert mesh, typically nylon, which is deployed in the laboratory or environment submerged in water ( Figure 1 ). Several designs have been used for the construction of SPATT devices, e.g., PVC frames ( Figure 1 ) [ 30 , 31 , 32 ], sewn bags [ 21 , 33 , 34 ], embroidery discs [ 23 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], Velcro mesh bags [ 43 , 44 ] or heat-sealed bags [ 45 , 46 , 47 ]. SPATT devices are then typically deployed in the field by attaching them to a structure or weighted line, and are often inserted in a “protection cage” ( Figure 1 ) to prevent damages, especially in energetic environments, and grazing by fish.…”

Modelling Toxin-Producing Algae in the Coastal Waters of Nigeria

“…Earlier preliminary reports by [21] [22] [23] [24] revealed the presence of potentially toxic phytoplankton in the Nigerian coastal waters. More recently, Zendong et al [25] reported the presence of algal toxin in the coastal waters of Nigeria. Although there are no records of human illness and massive aquatic animals and fish kills in Nigerian coastal waters, the presence of toxins producing species of phytoplankton implies the possibilities of its occurrence.…”