The dynamics of the plankton community on Lake Siombak, a tropical tidal lake in North Sumatra, Indonesia

Abstract

Abstract. Muhtadi A, Pulungan A, Nurmaiyah, Fadlhin A, Melati P, Sinaga RZ, Uliya R, Rizki M, Rohim N, Ifanda D, Leidonald R, Wahyuningsih H, Hasani Q. 2020. The dynamics of the plankton community on Lake Siombak, a tropical tidal lake in North Sumatra, Indonesia. Biodiversitas 21: 3707-3719. The tidal lake is a very dynamic estuary ecosystem and very vulnerable to environmental stresses and disturbances. Plankton is an aquatic organism that is very easily affected by environmental pressures and disturbances. This study aimed to reveal the phenomenon of plankton dynamics in tropical tidal lakes in Indonesia. The study was conducted at Siombak Lake from September 2018 to August 2019. Data were collected at high and low tides every month during the full month. The data analysis included plankton abundance, diversity index, and the relationship between water quality and plankton with PCA and succession analysis. The results showed that in Siombak Lake was found 66 genera which consisted of 54 phytoplankton genera and 12 zooplankton genera. Plankton abundance is higher in parts of the lake (stations 1-8) than in the river (stations 9-11) at both high and low tide. Temporally it shows that plankton abundance is higher in the rainy season (Feb-Aug, outside May) than in the rainy season (Sep-Jan, and May). Spatially, plankton in Siombak Lake at high tide is more influenced by TSS, phosphate, and salinity, while at low tide, it is influenced by TSS, Water transparency, BOD, silicate, salinity, and dissolved oxygen. Temporally, plankton in Siombak Lake at high tide is more influenced by salinity, conductivity, Debit, TSS, and salinity, while at low tide, it is influenced by salinity, conductivity, turbidity, TSS, TDS, DO, BOD, and COD. Based on the plankton Frontier succession graph, it shows that Siombak Lake is included in stage 1 and stage 2. Stage 1 occurs before the rainy season (August-September) and the peak of the dry season (March-April).

The relationship between water quality and aquatic organisms in tidal lakes, Medan-Indonesia

“…Data collection on water quality and aquatic biology is carried out every full moon at high and low tide. Water quality data refers to water biology and is further processed from previous research by [2,4,5,6,7,8,10].…”

“…Other notable species in Siombak Lake include herring fish (M. cyprinoides), eel fish (A. bicolor), and jellyfish (A. aurita). Siombak Lake's biological community includes fresh, brackish, and marine biota, as well as newcomers and settlers [3,4,5,67,8,12].…”

“…Similarly, fish are spatially and temporally closely related to their food sources, namely, zooplankton, crustaceans, and mollusks. The waters of Siombak Lake are a food search area for fish organisms, both fresh and marine fish that alternately enter the lake according to salinity conditions [5,8]. Based on correlation and regression and the descriptive analysis between salinity and aquatic organisms in Siombak Lake, it can be said that salinity influences the distribution and number of plankton., larvae, crustaceans, and fish species and populations.…”

“…Some mangroves develop around the lake's perimeter [3,4]. The aquatic biota of Siombak Lake consists of groups of freshwater fish, brackish, and marine creatures [5][6][7][8]. Siombak Lake serves as catchment area for water, a flood control zone, a fishing area for fish, shellfish, and crabs, and a tourist attraction.…”

“…Various studies of Siombak Lake have been conducted, including on morphology and hydrodynamics as well as the status and profile of lake water quality [1,2,10,11]. Studies on aquatic biodiversity such as fish, crustaceans, mollusks, and plankton have also been conducted [3][4][5][6][7][8]. In addition, studies on mangroves and bird and mammal biodiversity have been reported in 2020 and 2021 [3,12].…”