Hydrobiology

The Ecuadorian Tropical Andes serve as vital biodiversity hotspots, crucial for hosting and preserving unique endemic species. While numerous taxonomic groups within these hotspots have been extensively studied, microalgae remain relatively unknown. This study aimed to document the microalgal diversity of Tropical Andean lakes in Ecuador and its relationship with abiotic environmental factors. Water samples were collected from 28 lakes throughout 10 conservation areas, spanning different altitudes in the Ecuadorian Tropical Andes, along with water physical/chemical data. A total of 92 microalgal genera were identified, spanning Bacillariophyta, Chlorophyta, Glaucophyta, Ocrophyta, Cyanophyta, and Euglenophyta. Lakes such as Rodeococha, Anteojos, Chinchillas, Toreadora, Magdalena, and La Mica exhibited the highest richness of microalgal genera. A positive association between temperature and the majority of microalgal phyla, except Glaucophyta, was observed. On the other hand, negative correlations were observed between total dissolved solids and water conductivity with microalgal biodiversity. Additionally, all groups displayed negative associations with pH, except Glaucophyta. The Jaccard similarity index was low among lake communities in agreement with the uniqueness of genera found in some lakes. This study represents a fundamental baseline for future investigations into Ecuador’s microalgal diversity and its relationship with abiotic environmental factors in the delicate freshwater ecosystems of Tropical Andean lakes.

Varuna litterata is an estuarine crab species widely distributed across the Indo-Pacific region, commonly dwelling in brackish waters, mangrove forests, and tidal estuaries. In Bangladesh, while four Scylla species dominate the commercial crab market, the locally consumed V. litterata remains a biologically overlooked gem of the coastal waters. These crabs are frequently captured as a byproduct during shrimp fry collection from coastal estuaries. In this context, the current study investigates the reproductive biology, morphometric dynamics, and market potential of V. litterata collected from the Pasur River, a coastal mangrove forest-adjacent estuary of southern Bangladesh. A total of 75 individuals were collected from March to April 2023, comprising 35 males and 40 females, resulting in a sex ratio of 1:1.14 (♂:♀), with a predominance of females. A visual observation of ovary development revealed four distinct maturation stages, with Stage IV (fully mature) being the most prevalent (43%), indicating peak reproductive activity during the sampling period. Morphometric analysis revealed that the average carapace width (CW) was 31.2 ± 5.7 mm and 31.9 ± 5.8 mm and the mean carapace length (CL) was 29.3 ± 4.7 mm and 30.1 ± 4.9 mm in males and females, respectively. However, the mean body weight (BW) was 13.1 ± 4.3 g in males and 12.7 ± 3.8 g in female crabs. The dominant CW class ranges from 33 to 33.99 mm (males) and 28.99–29.99 mm (females), appear to be the most vulnerable to fishing pressure. BW-CW and CL-CW relationships demonstrated negative allometric growth, with high correlations in both sexes. Significant sexual dimorphism was observed, with males having larger cheliped dimensions, while females had broader abdomens, likely supporting reproductive functions that are essential to their conservation. The marketing of this crab remains largely informal, yet rising local demand and prices highlight its emerging commercial potential. Therefore, incorporation into aquaculture and coastal fishery development of this crab species could enhance food security, support livelihoods, and contribute to sustainable blue economy initiatives in Bangladesh.

Environmental DNA (eDNA) detection has emerged as a powerful, non-invasive tool for identifying aquatic organisms, particularly those that are rare, elusive, or invasive. Dreissena polymorpha (zebra mussel) is an invasive bivalve posing ecological and economic threats to North American freshwater systems. In April 2021, zebra mussels were discovered attached to a boat destined for Lake Sidney Lanier in North Georgia—a high-use recreational reservoir with no prior reports of infestation. To determine whether D. polymorpha had been introduced, we implemented a biomonitoring protocol leveraging eDNA collection and PCR-based detection. Sampling was conducted during summer 2022 across high-risk marina sites and potential habitats. Positive controls from the Tennessee River yielded expected results, while Lake Lanier samples showed no evidence of zebra mussel DNA. Our results validate using eDNA methodology for proactive biomonitoring and highlight the importance of molecular surveillance and community outreach to prevent the establishment of invasive species in vulnerable aquatic systems. This study demonstrates the utility of a scalable, replicable early detection framework that can be adopted by educational institutions, natural resource agencies, and community groups to mitigate the risk of biological invasions.