Basic limnology of Lago Bonilla, a Tropical lowland lake (original) (raw)
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One year weekly dynamics of limnological conditions and phytoplankton in Lake Bonilla, Costa Rica
The detailed response of tropical lake phytoplankton to weather variations has been little studied, but it seems that composition varies in response to rain and wind variability over the course of the year. In order to gather more evidence on this variation, the weekly variability of phytoplankton composition was studied in Lake Bonilla, a low land (380 masl) 30 m deep tropical lake, from April 2010 to May 2011. Temperature variation at several depths was recorded automatically, and measurements of dissolved oxygen, water transparency, and nutrients were performed several times during the study period. The lake showed a warm monomictic pattern, with deep mixing occurring during the hemispherical winter, especially after a heavy rain period in December 2010. Phytoplankton was dominated by a few species: a colonial Cyanobacteria (Aphanocapsa sp., functional group F) and two colonial Chlorococcaceae (Botryococcus braunii and Eutetramorus tetrasporus, both in the functional group K). Their relative dominance shifted throughout the year, following changes in water column conditions in response to weather variations. Although changes in main functional groups indicate a shift in resource availability rather than energy, it was clear that attention should also be given to particular species adaptations beyond those used for establishing functional groups. Rev. Biol. Trop. 64 (4): 1771-1781. Epub 2016 December 01.
Temporal variation of phytoplankton in a small tropical crater lake, Costa Rica
Revista de biología tropical, 2010
The temporal variation in lake's phytoplankton is important to understand its general biodiversity. For tropical lakes, it has been hypothesized that they follow a similar pattern as temperate ones, on a much accelerated pace; nevertheless, few case studies have tried to elucidate this. Most studies in Costa Rica have used a monthly sampling scheme and failed in showing the expected changes. In this study, the phytoplankton of the small Barvas's crater lake was followed for more than three years, first with monthly and later with weekly samplings, that covered almost two years. Additional information on temperature and oxygen vertical profiles was obtained on a monthly basis, and surface temperature was measured during weekly samplings around noon. Results showed that in spite of its shallow condition (max. depth: 7m) and low surface temperature (11 to 19°C), the lake stratifies at least for brief periods. The phytoplankton showed both, rapid change periods, and prolonged ones of relative stasis. The plankton composition fluctuated between three main phases, one characterized by the abundance of small sized desmids (Staurastrum paradoxum, Cosmarium asphaerosporum), a second phase dominated by equally small cryptomonads (Chryptochrysis minor, Chroomonas sp.) and a third phase dominated by the green alga Eutetramorus tetrasporus. Although data evidenced that monthly sampling could miss short term events, the temporal variation did not follow the typical dry and rainy seasons of the region, or any particular annual pattern.
Zooplankton variation in Fraijanes Lake (Costa Rica) during the course of one year
Revista de Biología Tropical
Zooplankton in small tropical lakes has been little studied and its variation during the year may respond to different factors. In this study, the zooplankton of a small neotropical lake was studied at different times during one year and compared with changes in the lake conditions and in phytoplankton composition. The lake stratifies from March until September, and mixes during the hemispherical winter, from October until February. Besides the lake show a seasonal fluctuation in water level according to the seasonality of rains. Zooplankton was composed of at least 13 species, four Cladocerans, three Copepods, four Rotifers and other groups such as an Ostracod and the larvae of Chaoborus. The most abundant were Thermocyclops sp., Daphnia sp. and Keratella tropica. Their abundance fluctuated along the year, probably in response to changes in lake level and changes in hydrological conditions, increasing during dry season when the main outlet of the lake dried up. Changes in phytoplan...
Revisiting the limnology of Lake Río Cuarto, Costa Rica, thirty-five years later
Revista de Biología Tropical, 2018
Lake Río Cuarto is a meromictic lake at low elevation in the North of Costa Rica. It offers an opportunity to compare its present state with the condition it had when first studied in the late 1970's and occasional samplings since then. This comparison expects to identify changes that could be attributed to incipient effects of global climate change. We studied the limnology and conditions of its drainage area for three years (2013-2016) to compare with previous data. Vertical profiles of temperature, dissolved oxygen, conductivity, pH, chlorophyll a, dissolved H 2 S were performed several times per year, for a total of 22 samplings. Aerial photographs taken since 1950 were analyzed to describe land use changes. The lake had a shallow Secchi depth (< 5 m) at all times. It was stratified on all occasions, with a thermocline that fluctuated between 10 and 20 m. It has a monimolim-nion, with a chemocline at 14 to 22 m. Below the chemocline it was always anoxic, and during annual partial mixing events in the mixolimnion, oxygen levels decreased compared to stratified periods. There was a continuous presence of H 2 S from 20 m downwards, with annual fluctuations, being lower during partial mixing events. A peak in chlorophyll was detected on all occasions just below the thermocline. Land use around the lake hasn't changed much since 1952, when only a rim of tree cover was left around the steep margins of the lake. The lake has maintained its limnological characteristics, with the only exception that it didn't cooled down to historical levels. This limited response could be the result of the high relative depth and steep margins of the lake, which prevent the downward distribution of heat and keeps the lake in a meromictic state, preventing its mixing for long periods of time. Rev. Biol. Trop. 66(Suppl. 1): S42-S52. Epub 2018 April 01.
Phytoplankton variability in Lake Fraijanes, Costa Rica, in response to local weather variation
2014
Phytoplankton species show a variety in morphology which is the result of adaptations to pelagic life including responses to fluctuations in water column dynamics driven by weather conditions. This has been reported in the oceans and in Northern temperate lakes. In order to observe whether tropical freshwater phytoplankton responds to seasonal variation in weather, the weekly variation in temperature of the water column and phytoplankton composition was studied in Lake Fraijanes, Costa Rica, a shallow (6.2m) lake at 1 640m above sea level. A chain of data loggers for temperature was placed in the deepest point in the lake to register temperature every hour at four different depths, and phytoplankton samples were retrieved every week for a year. Additional monthly samples for nutrients were taken at two depths. Notwithstanding its shallowness, the lake developed a thermal gradient which kept the water column stratified for several months during dry season. Whole lake overturns occurred during cold spells with intense precipitation. Phytoplankton changed throughout the year mainly through a shift in dominant taxa. From September to February the lake was frequently mixed by rain storms and windy weather. At this time, phytoplankton was dominated by Chlorococcal green algae. From March to June, the lake was stratified and warmer. Phytoplankton became dominated by Cyanobateria, mainly colonial Chroococcales. The rainy season started again in May 2009. During June and July the lake started to mix intermittently during rain events and phytoplankton showed a brief increase in the contribution of Chlorococcales. These changes fitted well to a general model of phytoplankton succession based on functional groups identified according to their morphology and adaptations. Rev. Biol. Trop. 62 (2): 483-494. Epub 2014 June 01.
Revista de Biología Tropical, 2014
Phytoplankton species show a variety in morphology which is the result of adaptations to pelagic life including responses to fluctuations in water column dynamics driven by weather conditions. This has been reported in the oceans and in Northern temperate lakes. In order to observe whether tropical freshwater phytoplankton responds to seasonal variation in weather, the weekly variation in temperature of the water column and phytoplankton composition was studied in Lake Fraijanes, Costa Rica, a shallow (6.2m) lake at 1 640m above sea level. A chain of data loggers for temperature was placed in the deepest point in the lake to register temperature every hour at four different depths, and phytoplankton samples were retrieved every week for a year. Additional monthly samples for nutrients were taken at two depths. Notwithstanding its shallowness, the lake developed a thermal gradient which kept the water column stratified for several months during dry season. Whole lake overturns occurred during cold spells with intense precipitation. Phytoplankton changed throughout the year mainly through a shift in dominant taxa. From September to February the lake was frequently mixed by rain storms and windy weather. At this time, phytoplankton was dominated by Chlorococcal green algae. From March to June, the lake was stratified and warmer. Phytoplankton became dominated by Cyanobateria, mainly colonial Chroococcales. The rainy season started again in May 2009. During June and July the lake started to mix intermittently during rain events and phytoplankton showed a brief increase in the contribution of Chlorococcales. These changes fitted well to a general model of phytoplankton succession based on functional groups identified according to their morphology and adaptations. Rev. Biol. Trop. 62 (2): 483-494. Epub 2014 June 01.
Revista de Biología Tropical, 2014
It is located 650m above sea level along the boundary between the North Caribbean and Pacific slopes, near the Southern end of the volcanic Guanacaste mountain range. In the early 1980s the lake's main outlet was dammed and the outflow was diverted into Arenal Reservoir. Lake Cote was first studied in 1990-1991, and later in 2001, before it was again modified by raising its dam by one meter to use its outflow for hydroelectricity. From 2002 to 2010 it has been monitored twice a year for changes in its limnology. Here I present a summary of its basic characteristics and an analysis of their changes through time. The lake is discontinuous polymictic, and sometimes develops a thermocline at 6m depth that may last for several days as evidenced by the occasional development of an anoxic layer close to the bottom. Since its modification for hydropower production, the surface water temperature has attained higher values than before. Oxygen levels in the lake show periods of hypoxia to anoxia in the hypolimnion, that have become more frequent since modification. Despite its turbid water, the lake has low levels of nutrient concentrations and of chlorophyll a. The trend in these parameters in recent times is a reduction in chlorophyll a and an increase in water transparency, implying a reduction in primary productivity. These changes are discussed in relationship with anthropogenic factors such as the modification of the lake and its management, changes in landscape around the lake and global climate change.
Limnology of Botos Lake, a tropical crater lake in Costa Rica
Revista de biología tropical, 2001
Botos Lake, located at the Poas Volcano complex (Costa Rica) was sampled eight times from 1994 to 1996 for physicochemical conditions of the water column and phytoplanktonic community composition. Depth was measured at fixed intervals in several transects across the lake to determine its main morphometric characteristics. The lake has an outlet to the north. It is located 2580 m above sea level and is shallow, with a mean depth of 1.8 m and a relative depth of 2.42 (surface area 10.33 ha, estimated volume 47.3 hm3). The lake showed an isothermal water column in all occasions, but it heats and cools completely according to weather fluctuations. Water transparency reached the bottom on most occasions (> 9 m). The results support the idea that the lake is polymictic and oligotrophic. The lake has at least 23 species of planktonic algae, but it was always dominated by dinoflagellates, especially Peridinium inconspicuum. The shore line is populated by a sparse population of Isoetes sp...
Phytoplankton species diversity of 27 lakes and ponds of Costa Rica (Central America)
1985
The literature on species diversity of phytoplankton of tropical lakes is scarce, and for the main part comes from studies of the big lakes in Africa, or deep lakes in South America, leaving a gap in the information about small shallow tropical lakes. In the present work the phytoplankton species composition and diversity of 27 shallow lakes and ponds in Costa Rica (Central America) was studied. The species composition was found to agree with other studies of tropical lakes, with a dominance of Chlorophyta, Cyanophyta, or in some cases Bacillariophyta or Euglenophyta; and a general paucity of Chrysophyta and Cryptophyta.
Basic limnology of fifty-one lakes in Costa Rica
International Journal of Tropical Biology and Conservation, 2003
We visited 51 lakes in Costa Rica as part of a broad-based survey to document their physical and chemical characteristics and how these relate to the mode of formation and geographical distribution of the lakes. The four oxbow lakes were low in elevation and tended to be turbid, high in conductivity and CO 2 , but low in dissolved O 2 ; one of these, L. Gandoca, had a hypolimnion essentially composed of sea water. These were similar to the four wetland lakes, but the latter instead had low conductivities and pH, and turbidity was often due to tannins rather than suspended sediments. The thirteen artificial lakes formed a very heterogenous group, whose features varied depending on local factors. The thirteen lakes dammed by landslides, lava flows, or lahars occurred in areas with steep slopes, and were more likely to be stratified than most other types of lakes. The eight lakes that occupy volcanic craters tended to be deep, stratified, clear, and cool; two of these, L. Hule and L. Río Cuarto, appeared to be oligomictic (tending toward meromictic). The nine glacial lakes, all located above 3440 m elevation near Cerro Chirripó, were clear, cold, dilute, and are probably polymictic. Cluster analysis resulted in three significant groups of lakes. Cluster 1 included four calcium-rich lakes (average 48 mg l -1 ), Cluster 2 included fourteen lakes with more Si than Ca +2 and higher Clthan the other clusters, and Cluster 3 included the remaining thirty-three lakes that were generally less concentrated. Each cluster included lakes of various origins located in different geographical regions; these data indicate that, apart from the high-altitude glacial lakes and lakes in the Miravalles area, similarity in lake chemistry is independent of lake distribution.