water

Article The Diversity of Tropical Freshwater (Rotifera: ) in Relation to Environmental Factors

Nhat-Truong Phan 1, Quang Hung Duong 1, Quynh Anh Tran-Nguyen 1,* and Mau Trinh-Dang 2,*

1 DN-EBR, The University of Da Nang—University of Science and Education, Da Nang City 550000, Vietnam; [email protected] (N.-T.P.); [email protected] (Q.H.D.) 2 Faculty of Biology and Environmental Sciences, The University of Da Nang—University of Science and Education, 459 Ton Duc Thang St., Danang City 550000, Vietnam * Correspondence: [email protected] (Q.A.T.-N.); [email protected] (M.T.-D.); Tel.: +84-948765483 (Q.A.T.-N.); +84-905436189(M.T.-D.)

Abstract: This study aims to evaluate the diversity of rotifers in various freshwater habitats in Da Nang City, Vietnam, and to investigate the relationship between community structure and environmental conditions. A total of 75 species belonging to 25 genera and 17 families were recorded, out of which seven species are new to Vietnam. Species from the families and are abundant (containing about 50% and 69.44%, respectively) in the total rotifer species in both lacustrine and riverine habitats. The number of rotifers recorded in the lakes (64 taxa) was much higher than those in rivers (36 taxa), and this is possibly due to the conditions in lakes being more favorable for the development of small zooplanktons. The significant influences of environmental

 factors (temperature, pH, turbidity, and trophic state) on the rotifer community were well-reflected  in the distribution of commonly found species in lakes (p-value < 0.05). Our study results enrich the

Citation: Phan, N.-T.; Duong, Q.H.; data on the diversity and the ecology of rotifers in Vietnam. Tran-Nguyen, Q.A.; Trinh-Dang, M. The Species Diversity of Tropical Keywords: Rotifera; rotifer community; community structure; freshwater habitats; species diversity Freshwater Rotifers (Rotifera: Monogononta) in Relation to Environmental Factors. Water 2021, 13, 1156. https://doi.org/10.3390/ 1. Introduction w13091156 Rotifers represent an important zooplankton group since they can contribute more than 50% of zooplankton productivity [1,2]. The rotifer species can be found in all kinds of Academic Editor: Artem Y. Sinev water bodies worldwide due to their high adaptability to a wide range of environmental conditions and their ability to occupy open niches quickly. In aquatic systems, rotifers play Received: 15 March 2021 a crucial role in the energy flows of that system. This group of organisms is responsible Accepted: 15 April 2021 for transferring carbon from picoplankton and nanoplankton to macro-zooplankton; they Published: 22 April 2021 act as links between microbial loops and the larger aquatic food web [3–5]. Additionally, rotifers are considered effective indicators for environmental conditions because of their Publisher’s Note: MDPI stays neutral sensitivity to the changes in that particular environment [6–9]. It was well-documented with regard to jurisdictional claims in published maps and institutional affil- that the rotifer community structure is influenced by factors such as water temperature, iations. salinity, transparency, trophic status, and predators [10,11]. The rotifer species composition, its total abundance, and its diversity indices have been widely applied in order to assess water quality [12–14]. Numerous studies have focused on seasonal or periodic changes in the rotifer commu- nity in relation to water characteristics in a single type of water body. However, very few Copyright: © 2021 by the authors. studies compared their structures in different water bodies within the same area. Liang Licensee MDPI, Basel, Switzerland. et al. (201