Abstract
Lake Rio Cuarto is a meromictic maar lake located in the low plains of northern Costa Rica. Its plankton composition has been studied several times since the decade of 1970. Yet most studies made short term surveys, and at least one study lasted for one year. Here we present data on phytoplankton and zooplankton composition from a four year study of the lake, from 2013 to 2017. Phytoplankton was studied from subsurface samples, preserved in Lugol’s solution and zooplankton from 20 m vertical hawls of a 64 um mesh net, and preserved with formaline and later transferred to 95% etanol. Phytoplankton composition included 54 taxa, most of them from the were Chlorophyta, followed by Cyanobacteria and Bacillariophyta. The most abundant were Synechococcus spp., Aphanocapsa sp. Coenochloris fotii, Chlorella sp. and Discostella stelligera. Total phytoplankton decreased from 2013 to 2017, mainly due to a decrease in Cyanobacteria. Zooplankton comprised 14 taxa, 5 cladocerans, 4 copepods, 1 diptera and 4 rotifers. The most abundant were Keratella cochlearis, Brachionus falcatus, Eubosmina tubicen and Arctodiaptomus dorsalis. There was a substitution of dominant species through time, at first (2013-2014) K. cochlearis and E. tubicen alternated in dominance, and later (2015-2016), A. dorsalis, Diaphanosoma sp. and Ceridaphnia sp. became dominant, with a return of K. cochlearis by 2017. The relationship between both components of the plankton is a complex result of the responses of individual species of both microalgae and zooplankton. However, most zooplankton taxa should be regarded as omnivores, so those relationships are not direct causal effects. The changes that occurred during the time of the study seem to be related to changes in the conditions of the lake, since its thermocline deepened with time and became more transparent. Those changes were not cyclical on an annual basis, but seemed to occur more on a long-term basis, as has been recognized earlier in the literature about tropical lakes.
Highlights
The plankton is a one of the main components of a lake ecosystem
It has been observed that the seasonality of the plankton follows a fairly predictable path of change along the year, which repeats almost unaltered from year to year (Reynolds, 1984b). This situation has allowed the establishment of models that describe the path of change in species composition of phytoplankton according to lake conditions, such as the one proposed by Reynolds (1984a), or the model of seasonal changes produced by the Plankton Ecology Group in Europe (Sommer, Gliwicz, Lampert, & Duncan, 1986; Sommer et al, 2012)
Weather data were taken from a near station that belongs to the Instituto Meteorológico Nacional (IMN)
Summary
The plankton is a one of the main components of a lake ecosystem. It includes a great variety of forms, from small photosynthetic Cyanobacteria and pico eucariotic microalgae, to large complex organisms such as dinoflagelates and metazoan groups such as Rotifers, Cladocerans and Copepods, among other organisms. Umaña-Villalobos (1985) reported the composition of the phytoplankton at this lake in the previous year (1983-1984) and found a total of 16 species of microalgae, but in his case, Mougeotia was present, the most abundant species were from the Cyanobacteria, mainly three forms of Anabaena sp., which were more abundant at in October-November, 1984. Haberyan et al (1995) sampled 30 lakes in Costa Rica for phytoplankton and 17 for zooplankton, among them Río Cuarto, during July and August 1991 They only give data on the presence of zooplankton species, which included: Bosmina hagmanni, Ceriodaphnia cornuta, Diaphanosoma cornuta and insect larvae. We aim to give a description of the planktic structure in Lake Rio Cuarto at present, during a four-year study, and to offer some hints of possible explanations of changes in planktic composition and the relationships among both components of the planktic assemblage
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
