Fish Diversity and Habitat Complexity: The Role of Macrophytes and Physicochemical Parameters in Urban and Rural Tropical Lakes

Abstract

Freshwater ecosystems are increasingly impacted by urbanization, agricultural runoff, and invasive species, all of which shape aquatic biodiversity. This study provides a comparative ecological assessment of two contrasting freshwater lakes, Katpadi Lake (urban) and Saina Palayam Lake (rural) located in Vellore District, Tamil Nadu, India. In the present study, a total of 15 fish species were recorded in both the lakes, with Oreochromis niloticus being the exotic and invasive. The order Cypriniformes dominated the fish community (60%), reflecting its ecological flexibility. Diversity indices such as Shannon (H′) and Simpson (1–D) showed minimal differences between the sites. However, Katpadi Lake exhibited higher total dissolved solids and conductivity, indicating greater anthropogenic impact. A total of 10 macrophytes were identified from the study sites, representing submerged, floating-leaved, and emergent growth forms. Their distribution varied across urban, and rural areas, reflecting differences in habitat conditions and water quality. Macrophyte diversity was higher in Saina Palayam Lake, suggesting a link between macrophytes complexity and fish diversity. Submerged species like Najas marina and Myriophyllum spicatum likely contributed to improved habitat conditions for native fauna. Nutrient concentrations, especially elevated nitrate and phosphate levels in Saina Palayam Lake, hint at non-point agricultural runoff, whereas Katpadi Lake exhibited elevated hardness, chloride, and ammonia levels, reflecting a stronger urban pollution influence. Despite low dissolved oxygen levels in both sites, fish communities persisted—possibly due to habitat refuges provided by macrophytes. This study underscores the need for integrated monitoring of fish, macrophytes, and water quality to manage freshwater biodiversity in varying environmental conditions.