Phytoplankton of the delta of the Mekong River during the dry season
AbstractHuman activity has disturbed the functioning of river ecosystems all around the globe. The current global climatic fluctuations and local anthropogenic impact lead to rearrangement in the structure and functioning of aquatic communities. One of the most important components of aquatic ecosystems is phytoplankton as the main primary producer of the organic matter, the basis for trophic relations and indicator of changes in the environment. This article presents the first results of a study concerning the peculiarities of quantitative distribution of biomass and species composition of phytoplankton in the delta of the Mekong River at the beginning of the dry season (December of 2018). Diatoms dominated according to biomass practically in all the stations of selection of samples. The total biomass of phytoplankton on average accounted for 0.049 ± 0.007 mg/L at the abundance of 40 ± 7 103 ind./L. In practically all the studied plots, according to biomass, the dominating diatoms were first of all Aulacoseira granulata, A. islandica, Cyclotella meneghiniana, Cyclotella spp., and Oxyneis binalis. Among Chlorophyta, most often we found Chlorella sp. and Scenedesmus quadricauda, but their biomass was insignificant. We determined statistically significant correlation relationships between biomass of phytoplankton and hydrological parameters. Based on the Spearman’s rank correlation coefficient, we determined negative relations between the total biomass of phytoplankton with salinity and pH. Positive correlation was seen between the biomass of diatoms and turbidity, and also between the temperature and the biomass of chlorophytes and Dinophyta. The biomass of golden algae (Chrysophyceae) and Dinophyta positively correlated with the mineralization. Quantitative regression analysis confirmed the close relationship between the total biomass of phytoplankton, hydrophysical and hydrochemical parameters. Besides the importance of scientific data on biological diversity and ecology of plankton algae, the results we obtained are necessary for organizing biological monitoring in the delta of the Mekong River in the future.
Boltachev, A. R., Karpova, E. P., Statkevich, S. V., Nguyen, V. T., & Trinh, T. L. C. (2018). Characteristics of quantitative distribution of fish and decapod crustaceans in the Mekong Delta during the low-water season of 2018. Marine Biological Journal, 3(4), 14–28.
Bondarenko, N. A., Malnik, V. V., Vishnyakov, V. S., Rozhkova, N. A., Sinyukovich, V. N., Gorshkova, A. S., Timoshkin, O. A., & Matveyev, A. N. (2016). Modern state of the biota of the Selenga River delta (Lake Baikal basin) under conditions of unstable hydrological regime. Report 1. Microbial Community and Algae. Hydrobiological Journal, 52(1), 17–29.
Flöder, S., & Burns, C. W. (2004). Phytoplankton diversity of shallow tidal lakes: Influence of periodic salinity changes on diversity and species number of a natural assemblage. Journal of Phycology, 40, 54–61.
Gabyshev, V. A., Tsarenko, P. M., & Ivanova, A. P. (2019). Diversity and features of the spatial structure of algal communities of water bodies and watercourses in the Lena River estuary. Inland Water Biology, 12, 1–9.
Gusev, E. S. (2014a). Vidovoy sostav i struktura soobshchestv fitoplanktona vodokhranilishch provintsii Kkhan’khoa [Species composition and structure of phytoplankton communities in reservoirs of Khanh Hoa province]. In: Ecology of Internal Waters of Vietnam. KMK, Moscow. Pp. 84–96 (in Russian).
Gusev, E. S. (2014b). Produktsionnyye kharakteristiki i troficheskiy status vodokhranilishch Tsentral’nogo i Yuzhnogo V’yetnama [Production characteristics and trophic status of reservoirs in Central and South Vietnam]. In: Ecology of Internal Waters of Vietnam. KMK, Moscow. Pp. 74–83 (in Russian).
Idumah Okogwu, O., & Ugwumba, A. O. (2013). Seasonal dynamics of phytoplankton in two tropical rivers of varying size and human impact in Southeast Nigeria. Revista de Biología Tropical, 61(4), 1827–1840.
IPCC (2014). Summary for policymakers. Climate change 2014: Impacts, adaptation, and vulnerability. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge. Pp. 1–32.
Jeppesen, E., Beklioğlu, M., Özkan, K., & Akyürek, Z., (2020). Salinization increase due to climate change will have substantial negative effects on inland waters and freshwater resources: A call for multifaceted research at the local and global scale. The Innovation, 1(2), 100030.
Jeppesen, E., Brucet, S., Naselli-Flores, L., Papastergiadou, E., Stefanidis, K., Nõges, T., Nõges, P., Attayde, J. L., Zohary, T., Coppens, J., Bucak, T., Menezes, R. F., Freitas, F. R. S., Kernan, M., Søndergaard, M., & Beklioğlu, M. (2015). Ecological impacts of global warming and water abstraction on lakes and reservoirs due to changes in water level and salinity. Hydrobiologia, 570, 201–227.
Jeppesen, E., Søndergaard, M., Pedersen, A. R., Jürgens, K., Strzelczak, A., Lauridsen, T. L., & Johansson, L. S. (2007). Salinity induced regime shift in shallow brackish lagoons. Ecosystems, 10, 47–57.
Korneva, L. G., & Mineeva, N. M. (1986). Sostav i produktivnost’ fitoplanktona v vodoyemakh s vysokoy mutnost’yu [The composition and productivity of phytoplankton in water bodies with high turbidity]. In: Biology and ecology of aquatic organisms. Nauka, Leningrad (in Russian).
Le, T. V. H., Nguyen, H. N., Wolanski, E., Tran, T. C., & Haruyama, S. (2007). The combined impact on the flooding in Vietnam’s Mekong River delta of local man-made structures, sea level rise, and dams upstream in the river catchment. Estuarine, Coastal and Shelf Science, 71, 110–116.
Lind, O. T., Doyle, R., Vodopich, D. S., Trotter, B. G., Limón, J. G., & Dávalos-Lind, L. (1992). Clay turbidity: Regulation of phytoplankton production in a large, nutrient-rich tropical lake. Limnology and Oceanography, 37(3), 549–565.
Nhan, N. H., & Cao, N. B. (2019). Damming the Mekong: Impacts in Vietnam and solutions. In: Wolanski, E., Day, J., Elliott, M., & Ramesh, R. Coasts and estuaries. Elsevier, London. Pp. 321–340.
Olenina, I., Hajdu, S., Andersson, A., Edler, L., Wasmund, N., Busch, S., Göbel, J., Gromisz, S., Huseby, S., Huttunen, M., Jaanus, A., Kokkonen, P., Ledaine, I., & Niemkiewicz, E. (2006). Biovolumes and size-classes of phytoplankton in the Baltic Sea. Baltic Sea Environment Proceedings, 106, 1–144.
Silva, E. I. L. (2007). Ecology of phytoplankton in tropical waters: Introduction to the topic and ecosystem. Asian Journal of Water, Environment and Pollution, 4(1), 25–35.
Soares, M. C. S., Huszar, V., & Roland, F. (2007). Phytoplankton dynamics in two tropical rivers with different degrees of human impact (Southeast Brazil). River Research and Applications, 23, 698–714.
Triet, N. V. K., Dung, N. V., Hoang, L. P., Duy, N. L., Tran, D. D., Anh, T. T., Kummu, M., Merz, B., & Apel, H. (2020). Future projections of flood dynamics in the Vietnamese Mekong delta. Science of the Total Environment, 742, 140596.
Tuyen, N. V. (2003). Biodiversity in algae in Vietnam’s inland waters. Prospects and challenges. Agriculture Publishing House, Hanoi (in Vietnamese).
Van Manh, N., Dung, N. V., Hung, N. N., Kummu, M., Merz, B., & Apel, H. (2015). Future sediment dynamics in the Mekong delta floodplains: Impacts of hydropower development, climate change and sea level rise. Global and Planetary Change, 127, 22–33.
Webster, I., Rea, N., Padovan, A., Dostine, P., Townsend, S., & Cook, S. (2005). An analysis of primary production in the Daly River, a relatively unimpacted tropical river in Northern Australia. Marine and Freshwater Research, 56(3), 303–316.
Zoccarato, C., Minderhoud, P. S., & Teatini, P. (2018). The role of sedimentation and natural compaction in a prograding delta: insights from the mega Mekong delta, Vietnam. Scientific Reports, 8(1), 11437.