Mangroves are salt tolerant coastal vegetation that inhabits tropical and sub-tropical regions and consider as one of the most productive ecosystem of the world. About 95% of Avicennia marina is distributed along the Indus delta at South west of Karachi. They provide a distinct habitat for sheltering and nourishing wide variety of fauna and flora. Among benthic fauna, largely diversified communities of marine sponges have found but taxonomically no data has recorded from Pakistan. Liosina paradoxa (family Dictyonellidae) is the dominant sponge species found on pneumatophores of A. marina. This species is systematically identified and widely distributed at Sandspit backwater mangroves, Karachi coast. Other marine sponge species, Callyspongia (Cladochalina) fibrosa and Haliclona (Soestella) hornelli belonged to order Haplosclerida has also taxonomically recognized and first recorded from Churna Island and Buleji rocky ledges, respectively. The growth rate and abundance of dominating mangrove sponge L. paradoxa was showing highest growth rate in July in TR4 and maximum abundance was observed in TR3. The sponge volume was observed maximum in July (127.53 – 313.87 cm3) and minimum in December (6.24 – 24.48 cm3) in all four transects. During study, physicochemical parameters such as temperature was ranged between 19 - 32 °C, salinity was 35 – 41 PSU, dissolved oxygen was 0.11 – 3.44 mg L-1 and pH was 7.04 to 7.69. In addition to nutrients, NO3- concentration was maximum in June (5.64 µg L-1), NO2- and NH4+ concentrations were high in February (0.28 and 7.50 µg L-1, respectively) and the concentration of PO4-3 was maximum in April (2.95 µg L-1). Growth and abundance of sponge showed positive correlation with temperature, oxygen, pH, nitrite and ammonium ions. Among the flora, diatoms (90%) were the dominant group associated with L. paradoxa. Including the fauna, Foraminifera has showed maximum diversity (42%) in TR2 during monsoon season. Nematoda (41%) were the most dominant sponge associated community followed by Crustacea (38%) and Polychaeta (20%). For the identification of secondary metabolites, sponge (L. paradoxa) sample were soaked in four different solvents (n-hexane, ethyl acetate, dichloromethane and methanol). Eleven compounds were identified through GCMS and structure elucidation from their methyl ester derivatives which mostly result as fatty acids. The data obtained from the present study provides the information regarding systematic distribution, growth, abundance and associated communities of marine sponge L. paradoxa along the coastal region of Karachi.