The aerial filamentous microalga, Trentepohlia arborum (Chlorophyta), was cultured in three habitats - an aerial, a subaerial and an aquatic one - using different types of bioreactors. The growth, carotenoid productivity, and morphologic differences of T. arborum in different habitats were investigated. The maximum specific growth rate (mu) of the alga obtained in the logarithmic phase in the subaerial habitat was 0.034 h(-1). HPLC analysis also demonstrated that T. arborum accumulated a high content of carotenoids. Zeaxanthin was the primary carotenoid in subaerial culture, while beta,beta-carotene was dominant in aerial culture. The maximum carotenoid productivity, 67.7 mg m(-2) day(-1), was reached when T. arborum was cultured in the subaerial habitat under nitrogen depletion using a novel attached cultivation bioreactor. Overall, it was demonstrated that T. arborum exhibited a relatively high growth rate and carotenoid productivity under attached cultivation.