Limnology and Freshwater Biology

Diatom ecological guilds as environmental indicators for biomonitoring in a tropical river basin of Southeast Asia

Hallazgo, Carl Ian John — 2026-04-24

Functional traits are widely used in ecological studies to better understand diatom assemblages. This study examined the relationship between diatom ecological guilds (low-profile, high-profile, motile, and planktonic) and environmental parameters across 28 rivers and streams in the Tagoloan River Basin, Northern Mindanao, Philippines. The aim was to assess whether these guilds serve as effective indicators for biomonitoring. Canonical correspondence analysis (CCA) revealed a significant relationship (p=0.015), indicating that phosphate (PO₄³⁻), nitrate (NO₃⁻), nitrite (NO₂⁻), ammonium (NH₄⁺), turbidity, pH, temperature, total dissolved solids (TDS), total suspended solids (TSS), conductivity, dissolved oxygen (DO), and flow influence diatom ecological guilds. The CCA explained 98.27% of the variance in two axes, demonstrating that diatom ecological guilds respond to environmental variables and may serve as useful indicators for river basin biomonitoring, which is useful for tropical countries like the Philippines where physicochemical analyses can be costly.

Identification and comprehensive characterization of a new soil strain of carotenogenic microalgae Chlorosarcinopsis sp. VKM Al-296 (Chlorophyta)

Chubchikova, Irina — 2026-04-24

We conducted a complex study of the new green microalgae strain VKM Al-296, isolated from arable soil and identified as Chlorosarcinopsis sp. (Chlamydomonadales, Chlorophyta), using molecular phylogenetic analysis (18S rDNA and ITS2 sequences) and light and scanning electron microscopy. The strain’s morphology, growth, and carotenogenesis during two-stage batch cultivation were studied. In a liquid medium, the cells occurred singly or in packages surrounded by extracellular mucilage, with cell sizes of 3-6 µm. By the end of the “green” stage (vegetative growth) lutein was the predominant pigment, accounting for >60% of the total carotenoids. Other primary carotenoids were also present: beta-carotene (14.6%), neoxanthin (11.1%), and antheraxanthin (7.1%). At the end of the “red” (secondary carotenogenesis) stage, the culture’s dry biomass content was 1.92±0.04 g/L, with carotenoids accounting for 0.3% of the dry biomass. The pigment profile was dominated by ketocarotenoids: astaxanthin (mono- and diesters), canthaxanthin, and adonixanthin monoesters (35%, 21% and 20% of the total carotenoid content, respectively). Over the entire cultivation period (17 days), the average biomass productivity and total carotenoid productivity were 0.10 g/L/day and 0.2 mg/L/day, respectively. Chlorosarcinopsis sp. VKM Al-296 may be a perspective object of further research aimed at optimizing cultivation conditions as a source of lutein at the “green” stage, as well as canthaxanthin and esters of astaxanthin and adonixanthin at the “red” stage.

Morphological and genetic features of crustaceans Artemia parthenogenetica and A. tibetiana (Crustacea, Anostraca) in different-type hypersaline lakes in the south of Western Siberia

Bezmaternykh, Dmitry — 2026-04-24

We studied modern morphological features of parthenogenetic and bisexual Artemia populations from 10 different-type hypersaline lakes in the south of Western Siberia (Altai Krai). DNA barcoding of these populations revealed two Artemia species: Artemia parthenogenetica Barigozzi, 1974 and A. tibetiana (Abatzopoulos et al., 1998). The studies were conducted monthly from July to September 2025. Principal component analysis indicated differences in the hydrochemical composition of brine (water) of lakes inhabited by parthenogenetic and bisexual Artemia populations. Comparative analysis of morphological features suggested that females of A. parthenogenetica and A. tibetiana significantly differed in mean values (14 of 16 traits). Cluster analysis of 12 plastic and 4 meristic characters of A. parthenogenetica females demonstrated splitting of its population into three groups with different structural features of the furca: length (fl), number (sf), and length of setae (sl). The Spearman correlation index establishes significant statistical correlations between the morphological features of A. parthenogenetica and A. tibetiana and main environmental factors, i.e. salinity and water temperature.

Seasonal dynamics of rotifer community in relation to water quality at Pravara-Godavari river confluence (Ahmednagar, MS, India)

Zaware, Rajashi — 2026-04-24

This study reports the diversity, abundance, and seasonal dynamics of the rotifer community in the Pravara-Godavari river confluence, Ahmednagar, throughout a year, from November 2024 to October 2025. Seasonal sampling was conducted to assess rotifer species composition and density, and to measure key physicochemical water parameters, including temperature, pH, dissolved oxygen, turbidity, alkalinity, hardness, and chloride. A total of 19 rotifer species, representing 4 genera and 3 families, were recorded in the study area. Strong temporal variation in population structure was indicated by the rotifer community’s noticeable seasonal variations in both species richness and density. The summer period recorded the highest rotifer diversity and abundance. At the same time, the monsoon season had the lowest values, perhaps due to a dilution effect, increased water turbulence, and altered habitat stability. Furthermore, correlation analysis showed that important physicochemical parameters such as pH, water temperature, turbidity, alkalinity, total hardness, chloride concentration, and dissolved oxygen had a significant impact on rotifer species richness. These results demonstrate that even small changes in water quality can significantly impact the composition of rotifer communities. Overall, the study highlights rotifers’ sensitivity to environmental factors and underscores their value as reliable bioindicators for evaluating freshwater ecosystems.