RENEWABLE

ACUTE TOXICITY AND INHIBITORY RESPONSE OF MARINE MICROALGAE (Skeletonema costatum Cleve 1873) EXPOSED TO WATER-SOLUBLE FRACTIONS OF CRUDE OIL, DIESEL, SPENT ENGINE OIL AND THEIR COMPOSITE MIXTURE

B. O. Bello — 2024-03-25

Petroleum oils and their derivatives continue to devastate marine and coastal water ecosystems despite significant technological advancements in extraction and transportation systems. This is particularly true given their toxicity to sentinel organisms including Skeletonema costatum. This study assessed the potential of water-soluble fractions (WSFs) of crude oil, diesel, spent engine oil, and their composite mixture, to inhibit the growth of marine microalgae, Skeletonema costatum. At 72 hours after exposure, the sensitivity of test organisms to the WSF of various petroleum hydrocarbons were assessed using potential inhibition of cellular growth. The inhibition concentrations (IC₅₀) were determined as diesel 1.08% (10.8 g/l) > spent engine oil 2.27% (22.7 g/l) > crude oil 4.57% (45.7 g/l) > composite mixture 5.54% (55.4 g/l). The control population revealed an initial cell density of 2x10⁴ cells/ml to an average of 33.92x10⁴ cells/ml. The WSF of crude oil and its derivative hydrocarbons caused increasing inhibition of cellular growth as exposure concentrations increased. It was observed that trace levels of the hydrocarbons caused underlying cellular response which later manifested in growth inhibition of S. costatum. Petroleum hydrocarbons, even in trace levels, may contaminate marine water systems and exert toxicity on microalgae, leading to disruptions in the aquatic food chain.

PHENOTYPIC VARIABILITY REVEALED DIFFERENTIALLY HETEROGENEOUS TRAITS IN LONGNECK CROAKER, Pseudotolithus typus (Bleeker, 1863), ACROSS EPE AND LAGOS LAGOONS, NIGERIA

O. O. Oyebola — 2024-03-27

The adaptive phenotypic flexibility, descriptive and discreteness characteristics of Pseudotolithus typus obtained from Epe and Lagos lagoons in southwestern Nigeria were investigated to ensure precise identification, management and conservation of the species. Six meristic counts and 15 morphometric measurements were collected from mature Pseudotolithus typus obtained from Epe and Lagos Lagoons. Data on phenotypic and heterogeneous attributes were analysed using descriptive statistics, linear regression, and Discriminant Factor Analysis (DFA). Meristic values ranged from 2.00±0.00 (Eye) - 30.80±1.16 (Dorsal-Fin-Rays) and 2.00±0.00 (Eye) - 31.03±0.76 (Dorsal-Fin-Rays) in Epe and Lagos lagoons, respectively. Dorsal Spine Count had a higher variation at Epe (Coefficient of Variation, CV=5.58%) than Lagos lagoon (CV=4.65%). Morphometric values ranged from 4.25±0.51 (Orbital Length) - 28.77±1.54 (Head Length) in Epe Lagoon; and 3.52±0.22 (Pectoral Fin Width) - 28.35±1.75 (Body Depth) in Lagos Lagoon. Caudal Peduncle Length (CV=34.02%) and Mouth Height (CV= 12.44%) had the highest variation in Epe and Lagos Lagoons; respectively. Generally, 56.25% and 37.50% of the attributes had CV>10% in Epe and Lagos Lagoons. Cross-validation of group membership revealed 95.0% (entire), 93.3% (Epe) and 96.7% (Lagos) correctness of the apriori groupings. Pseudotolithus typus population demonstrated taxonomic sanctity, but differentially flexible phenotypes across Epe and Lagos lagoons. This indicates the adaptive potential and survivability of the species in multiple lagoon environments.

INFLUENCE OF TEMPERATURE ON EARLY GROWTH OF Pterocarpus santalinoides L’Hérit. ex DC.

C. Fredrick — 2024-05-13

This study evaluated the effect of temperature on the early growth of Pterocarpus santalinoides seedlings. In a completely randomized experiment, 80 randomly selected seedlings were subjected to four temperature regimes namely: 20/27±3°C, 22/30±3°C, 25/33±3°C and 27/35±3°C. Initial measurements of seedling growth variables were done, four months after sowing and bi-monthly thereafter for twelve months. Variables such as seedling height, stem collar diameter, number of leaves, root length, shoot and root fresh and dry weights, moisture content, total weight and root to shoot ratio were monitored. Data were analysed using Analysis of Variance and Duncan Multiple Range Test was used to separate significantly different means. There were significant differences in the height, collar diameter, number of leaves, root length and biomass of Pterocarpus santalinoides seedlings grown at different temperatures. After four months, the highest height (35.05 cm) was observed for 22/30±3°C treatment, while lowest (28.11) was for 27/35±3°C. From 6 to 12 months, the highest heights: 31.37 cm, 38.04 cm, 45.15 cm and 50.51 cm, respectively, were observed for 25/33±3°C treatment, while the lowest (31.37 cm, 38.04 cm, 45.15 cm and 50.51 cm) were for 20/27±3°C treatment. Highest collar diameters (5.34 mm, 6.88 mm, 8.65 mm, 9.83 mm and 10.48 mm) were observed at 27/35°C±3°C and lowest 3.82 mm, 4.42 mm, 5.86 mm, 6.61 mm and 8.61 mm) at 20/27^oC±3°C, from 4 to 12 months. The longest (44.88 mm) and least (30.58 mm) root lengths were observed at 25/33°C±3°C and 20/27^oC±3°C, respectively. Pterocarpus santalinoides seedlings grew at all tested temperature regimes, with better growth observed at 25/33^oC and 27/35^oC.

EFFECTS OF SALT STRESS ON VEGETATIVE PROPAGATION OF Pterocarpus santalinoides L’Hérit. ex DC.

C. Fredrick — 2024-06-19

The influence of salt stress on sprout length, collar diameter, leaf and branch production, and survival rate of Pterocarpus santalinoides stem cuttings was assessed. In a completely randomized design with five treatments: (0, 5, 10, 15 and 20 grams of salt), 20 cuttings were exposed to each of the five salt solutions. Data were analyzed using descriptive and inferential statistics. There were significant differences in the growth variables across treatments. However, sprout length at six weeks, did not significantly differ. Growth variables decreased with increase in salt stress, with control and 20 g displaying the highest and lowest growth attributes, respectively. Seedlings in control treatments had the highest sprout length (20.65 mm, 28.30 mm, 32.15 mm and 40.35 mm) at 6, 8, 10 and 12 weeks, respectively, while 20 g treatment had the least (15.95 mm, 17.78 mm, 19.80 mm and 25.80 mm). Number of leaves (13.25, 18.75, 22.13 and 36.13), branches (3.50, 4.88, 7.50 and 9.25) and collar diameter (3.50 mm, 4.88 mm, 7.50 mm and 9.25 mm) were highest for control over the 6, 8, 10 and 12 weeks. Stem cuttings of Pterocarpus santalinoides may not thrive well in saline soils, because of the negative effects of salt on seedlings.