Aquatic Life Sciences

Vaishali Bhatt, Prasant Arya, Jaspal Singh Chauhan

Microplastic (MP) contamination in freshwater ecosystems is an emerging environmental concern, yet interactions between MPs and riparian macrophytes remain poorly understood, particularly in Himalayan river systems. This study provides a baseline assessment of MP surface entanglement across riparian macrophyte species, along with associated surface water and sediment, from River Alaknanda, Srinagar, Uttarakhand, India, sampled in June 2023. A total of 30 macrophyte, surface water, and sediment samples were collected and processed using extraction protocols integrating washing, oxidative digestion, density separation, stereomicroscopic analysis, and polymer characterization through ATR-FTIR spectroscopy. MPs were extensively detected on macrophyte surfaces, with species-specific normalized burdens ranging from 16.47 ± 2.59 to 273.86 ± 26.21 MPs/g dry weight. Kruskal-Wallis analysis revealed significant interspecific variation in normalized MP abundance (H = 25.73, p = 0.0023), with Chenopodium ambrosioides exhibiting significantly higher MP burdens than Conyza sp. and Equisetum sp. No MPs within the analytical detection range of 100 µm-5 mm were detected in digested plant tissues. Fibres were the dominant MP type in macrophytes and water, whereas fragments predominated in sediments, with white particles being most abundant across all matrices. Polymer analysis identified polyester, polyethylene, polypropylene, polyterephthalate, and polyethylene-vinyl acetate as dominant polymers. Strong compositional correlations among macrophytes, water, and sediment indicated similarities in MP characteristics across environmental matrices. These findings suggest riparian macrophytes as complementary matrices for freshwater MP monitoring. Despite methodological and spatial limitations, this study establishes a preliminary framework for incorporating riparian vegetation into freshwater MP monitoring and highlights the need for further investigations.

Aquatic Life Sciences

Françoise D. MESSU MANDENG, Charles F. BILONG BILONG, Jean-François AGNESE

Understanding the trophic ecology of fish species is essential for developing effective management and conservation strategies. This study examined the role of diet in the assemblage structure of non-annual nothobranchiid fish species inhabiting permanent rainforest streams in southern Cameroon. In total, 1010 nothobranchiid individuals, assigned to 12 species belonging to two subgenera (mainly Aphyosemion), were harvested. The non-empty guts of 488 individuals were analysed, both qualitatively and quantitatively. All species examined were generalists. Their diet primarily consisted of terrestrial insects falling from the tree canopy, representing the bulk of their foraged food (%N = 76.8%), with an index of relative importance (IRI) of 94.3%. Hymenopterans were predominant in the environment (62%) and constituted the preferred prey type (IRI = 96.7%); the other items were accidental. Aquatic dipterans (Chironomidae) and Ephemeroptera followed. The diet of these fish species did not vary with parameters like site altitude, season, sex/ontogenetic groups, or fish size. They all fed on the same prey categories in equal proportions. The dietary overlap between the nothobranchiid fish species at sympatric occurrence sites was generally high, with a high reduction in their prey type uptake compared to a greater variety of prey intake in allopatric situations. Results suggest that there is low competition for food resources among these phylogenetically related species; they coexist by making immediate adjustments. In Cameroon rainforest streams, diet is not a factor structuring Nothobranchiid fish assemblages, providing valuable information for the ecological preservation of their biotope characteristics, which they rely on the most for survival.

Aquatic Life Sciences

Ibrahim Muhammad Usman, Odulate Dominic Olaniyi, Aisha Habibu Kusada

Water quality parameters play a critical role in determining the health and resilience of aquatic ecosystems, influencing the distribution, behavior and survival of aquatic organisms. The Physico-chemical water quality parameters of Zobe Lake, Katsina State, Nigeria were studied from March 2024 to February, 2025. The study area was divided into four strata (Sites 1, 2, 3 and 4) along the lake for easy assessment. Purposive sampling was used to select one landing site from each stratum based on the level of fishing activities. Air and water temperature, transparency, electrical conductivity and total dissolved solids were determined in-situ. pH, Dissolved oxygen, alkalinity, phosphate and nitrate were determined with standard analytical methods. The mean monthly values of physico-chemical parameters of Zobe Lake obtained are as follows: Dissolved oxygen, (7.59 ± 0.08 mg/l), air temperature; (36.62 ± 0.48˚C), water temperature (27.08 ± 0.24˚C), transparency (1.04 ± 0.03 m), nitrate (0.34 ± 0.03 mg/l), pH (7.36 ± 0.09), phosphate (2.18 ± 0.02mg/l), electrical conductivity (106.28 µS/m) and alkalinity (6.82 mg/l). There are significant differences (p < 0.05) in all the parameters tested across the month except alkalinity. The result of this study revealed relatively minimal differences among the four sampling sites, indicating that the lake is fairly homogeneous in water quality characteristics. However, continuous monitoring of nutrient parameters, particularly phosphate, is recommended to prevent future eutrophication and maintain the ecological health of the lake.

Aquatic Life Sciences

Vianney Ngabo Mulema, Gabriel Balagizi Baguma, Davina Namasale Ntabira, Gabriel Mukabo Okito

Wetlands are globally recognized as biodiversity hotspots, yet they remain among the threatened ecosystems. In the Democratic Republic of Congo, Ichthyological studies in wetlands are scarce, particularly in South Kivu, where anthropogenic pressures are accelerating habitat degradation. This study provides the first detailed morphological and ecological assessment of Lacustricola centralis (Seegers, 1996), formerly classified as Aplocheilichthys centralis, in the Cigongo Marsh, a wetland located in the southwestern watershed of Lake Kivu. A total of 249 individuals were sampled across four sites, and morphometric parameters (length and weight) and meristic traits (lateral line scales, fin rays) were analysed alongside physicochemical parameters. Size-class distribution was determined using Sturges’ rule, while Fulton’s condition factor (K) was applied to evaluate physiological status. Results revealed total length ranging from 16.8 to 50.8 mm and weight from 0.1 to 2.3 g. Lateralis line scales varied between 11 and 27. The sex ratio was female-biased (0.37 male: 1 female) with females dominating across size classes. Fulton’s K values indicate good body condition, with no significant differences between sexes or sites. Growth patterns were negative allometric, favouring elongation over mass increase. Physicochemical conditions were generally suitable for fish growth, though dissolved oxygen showed localized variability. The restricted distribution of this species, absent from Lake Kivu’s ichthyofaunal lists, highlights its potential as a bio-indicator of wetland health. These findings provide baseline data for ichthyofaunal inventories and support regional wetland conservation strategies.

Aquatic Life Sciences

Demtew Etisa Welbara

As global aquaculture rapidly expands, ensuring ecological and economic sustainability requires a transition toward circular economy solutions. Microalgae have emerged as highly adaptable primary producers capable of addressing both aquaculture nutritional deficits and environmental waste. This systematic review synthesizes 71 peer-reviewed papers published between 2000 to 2025 indexed in PubMed and Google Scholar to evaluate the integration of microalgal biomass across modern aquaculture systems. Quantitatively, microalgae, yield substantial dry cell weight concentrations containing 12–65% proteins, 2–23% lipids, and 5–26% carbohydrates, serving as highly nutritious direct feeds or live prey enrichers that enhance larval growth, survival, and coloration. Currently, their high photosynthetic efficiency drives ecological remediation; 1kg of microalgal biomass sequesters approximately 1.83 kg of CO₂, while their mixotrophic and autotrophic pathways achieve up to 99% removal of hazardous wastewater nutrients like inorganic nitrogen and phosphorus. By evaluating these functional benefits alongside key techno-economic bottlenecks such as species selection methods and harvesting costs this review establishes an integrated frame work for leveraging microalgae to achieve sustainable, eco-friendly global aquaculture.

Aquatic Life Sciences