Phytoplankton Assemblage in a Tropical Harbour: Microscopy versus Chemotaxonomy

2024-05-17T18:00:13+00:00

Investigations into phytoplankton community structures in Nigerian waters have always been carried out using conventional microscopy. Microscopic methods are not sufficient because very small-sized phytoplankton species are easily missed out from sample processing and examinations. At present, there is a dearth of literature on pigment-derived phytoplankton assemblage in Nigerian waters. Phytoplankton diversity was investigated for twelve months from May 2015 to April 2016 using both microscopic and chemotaxonomic methods. Scanning electron microscopic (SEM) images of phytoplankton species were taken with a JEOL JSM 5310 using between 12 and 15 kV accelerating voltage. Chemotaxonomic assessment of phytoplankton was done using a C8 reverse-phase High-Performance Liquid Chromatography (HPLC) pigment-labeling technique. A total of 96 phytoplankton species belonging to five classes were recorded from microscopic observations. Bacillariophyceae (diatoms) comprised 72 species, Chlorophyceae (green algae) had 2 species, Cyanophyceae (blue-green algae) was represented by 11 species, Dictyochophyceae (silicoflagellates) had 1 species and Dinophyceae (dinoflagellates) comprised 10 species. The results from the HPLC pigment-labeling technique validated microscopic observations for diatoms, dinoflagellates, blue-green and green algae. However, there were pigment-detections of coccolithophores and cryptophytes by HPLC which were not seen under the microscopes. From this study, Achnanthes eureka, Hyalosynedra laevigata, Mastogloia cuneata, Mastogloia emarginata, Navicula formenterae, and Palmerina hardmaniana are new records of diatoms in Nigerian waters. This study documented a pioneering effort at chemotaxonomic assessment in Nigeria, leading to the identification and quantification of nineteen phytopigments.

Acute Toxicity, Haematology, Plasma Electrolyte Responses and Hepatosomatic Index in Mud Catfish, Clarias gariepinus (Burchell 1822) Exposed to Two Household Surfactants

2024-05-27T10:46:48+00:00

The acute toxicity and sub-lethal effects of the surfactants JIKB and MFLS on Clarias gariepinus were assessed in laboratory bioassays. Acute toxicity was evaluated over a 96-hour period, while sub-lethal effects on plasma electrolytes (potassium K+, sodium Na+, chloride Cl-), haematological parameters (white blood cells WBC, red blood cells RBC, haemoglobin HGB, and haematocrit HCT), and the hepatosomatic index were investigated over 21 days. Results indicated that MFLS (96h LC₅₀ = 0.086 ml/L) was 3.28 times more toxic than JIKB (96h LC₅₀ = 0.282 ml/L). Haematological analysis showed reductions in WBC, RBC, HCT, and HGB values. Plasma electrolyte levels in C. gariepinus exposed to JIKB and MFLS ranged from 146.7 mEq/L to 220.0 mEq/L for sodium, 5.13 mEq/L to 20.7 mEq/L for potassium, and 111.3 mEq/L to 217.3 mEq/L for chloride, with marked dose- and time-dependent increases. Hepatosomatic index values showed significant differences (p < 0.05) at days 7 and 21, but not at day 14 (p > 0.05). Control values for test organisms exposed to JIKB and MFLS at 7, 14, and 21 days were 3.51 ± 0.82, 2.41 ± 1.11, and 2.95 ± 0.22, respectively. Short-term exposure of Clarias gariepinus to low concentrations of JIKB and MFLS significantly disrupted physiological processes, as evidenced by altered haematological parameters, increased plasma electrolyte levels, and variations in hepatosomatic index. MFLS was significantly more toxic than JIKB. These findings highlight the potential environmental risks posed by these surfactants to aquatic life, underscoring the need for careful management and regulation.

West African Journal of Fisheries and Aquatic Sciences

Phytoplankton Assemblage in a Tropical Harbour: Microscopy versus Chemotaxonomy

Acute Toxicity, Haematology, Plasma Electrolyte Responses and Hepatosomatic Index in Mud Catfish, Clarias gariepinus (Burchell 1822) Exposed to Two Household Surfactants