Gerardo Umaña VillalobosUniversity of Costa Rica | UCR · Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)
Gerardo Umaña Villalobos
MSc
About
49
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Introduction
Gerardo Umaña Villalobos currently works at the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), University of Costa Rica. Gerardo does research in freshwater plankton ecology. Their current project is 'Costa Rica limnology'.
Additional affiliations
January 1986 - present
January 1986 - present
Education
August 1983 - July 1985
Publications
Publications (49)
Abstract
Central America and the Caribbean, at the northern limit of the Neotropical region, is made up of a narrow strip of land and numerous islands, with a complex geological history, represents an important biogeographic connection between North and South America and contains diverse freshwater environments, including high mountain and lowland...
Prokaryotic diversity in lakes has been studied for many years mainly focusing on community structure and how the bacterial assemblages are driven by physicochemical conditions such as temperature, oxygen, and nutrients. However, little is known about how the composition and function of the prokaryotic community changes upon lake stratification. To...
In this paper we report the rediscovery of the endangered cichlid fish Amphilophus lyonsi (Gosse 1966) in the southern Pacific region of Costa Rica. Additionally, we provide new and updated information on the morphology, growth, habitat use and distribution of the species based on data and specimens recently collected as well as on museum material....
Long-term plankton studies in neotropical lakes are scarce. Here we studied plankton composition in Lake Cote, Costa Rica, twice per year from 2002 to 2018, to monitor changes after it was modified as a reservoir for hydroelectricity in 2003. Plankton variation was examined for a long-term trend and its relationship with basic limnological characte...
Seasonal variation, physicochemical and hydrological characteristics that influence aquatic macroinvertebrates, in a tropical river.
Introduction: The distribution of aquatic macroinvertebrates in rivers may be determined by the type of substrate, the shape of the river channel, the hydrological regime, and interactions with biotic and abiotic fac...
Long-term plankton studies in neotropical lakes are scarce. Here we studied plankton composition in Lake Cote, Costa Rica, twice per year from 2002 to 2018, to monitor changes after it was modified as a reservoir for hydroelectricity in 2003. Plankton
variation was examined for a long-term trend and its relationship with basic limnological characte...
Variación estacional y características fisicoquímicas e hidrológicas que influyen en los macroinvertebrados acuáticos, en un río tropical ABSTRACT. Seasonal variation, physicochemical and hydrological characteristics that influence aquatic macroinvertebrates, in a tropical river. Introduction: The distribution of aquatic macroinvertebrates in river...
The LIFE Index can be useful to determine the effect of changes in river flow on the community of aquatic macroinvertebrates and as a tool for the implementation of environmental flows. This study demonstrates how to classify aquatic macroinvertebrates into a flow category in order to adjust the LIFE Index to Costa Rica. A panel of experts was surv...
Hydropower development is accelerating in the tropics, especially construction of small dams. Small dams are often classified as those lower than 15 m in height or with reservoir capacity less than 3 × 10⁶ m³. Small dams frequently operate with water diversions from the main river channel, thereby affecting river connectivity through the creation o...
A checklist of the fishes of the Coto River basin, southern Pacific, Costa Rica, compiled from field and museum surveys is presented. A total of 61 species, representing 48 genera, 26 families and 11 orders are listed. Peripheral species were dominant (44.3%), whereas secondary and primary freshwater species represented 32.8% and 23.9% of the total...
In tropical lakes, seasonal changes in plankton dynamics are minimal and irregular, since climatic conditions are fairly stable throughout the year, in most cases only long-term studies allow observing patterns in the dynamics of the plankton. Lake Río Cuarto is a maar-type meromic lake located in the plains of Northern Costa Rica, in the past ther...
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 chang...
Fish assemblages and their ecological traits along an elevational gradient in the Río Pacuare, Costa Rica. Between May 2004 and May 2005, we sampled fish in 19 sites, grouped in four elevations, ranging from the river mouth to 650 m.a.s.l. in the Río Pacuare, Caribbean versant of Costa Rica. Changes in the distribution and composition of the fish f...
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 un...
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...
Benthic diatoms are the periphyton component most studied in Costa Rican rivers, yet there is still much to be known about their ecology. This study aims to contribute to this knowledge. Periphyton samples from six locations along the middle reach of Sarapiquí river and some of its tributaries were taken and analyzed from 2010 to 2012. A total coun...
Primary productivity in the National Térraba-Sierpe Wetland, Costa Rica. Phytoplankton primary production (PP) was determined in a broad sector of the Térraba-Sierpe National Wetland, Costa Rica, from September to November 2008 in the rainy season and from January to March 2009 in the dry season. Six sampling stations were located at the Northern a...
Phytoplankton primary production (PP) was determined in a broad sector of the Térraba-Sierpe National Wetland, Costa Rica, from September to November 2008 in the rainy season and from January to March 2009 in the dry season. Six sampling stations were located at the Northern and Central zone of the wetland, according to the main expected flux of Rí...
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 aga...
Despite the fact that little is known about the consequences of hydropower production in tropi- cal areas, many large dams (>15m high) are currently under construction or consideration in the tropics. We researched the effects of large hydroelectric dams on aquatic macroinvertebrate assemblages in two Costa Rican rivers. We measured physicochemical...
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 phy-toplankton responds to seasonal var...
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 aga...
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 vari...
Abstract: Despite the fact that little is known about the consequences of hydropower production in tropical
areas, many large dams (>15m high) are currently under construction or consideration in the tropics. We researched the effects of large hydroelectric dams on aquatic macroinvertebrate assemblages in two Costa Rican rivers. We measured physico...
Freshwater macroinvertebrates from Cocos Island, Costa Rica: species and comparison with other islands of the Eastern Tropical Pacific. Cocos Island is an oceanic island in the Eastern Pacific, at 496km from Cabo Blanco, Costa Rica. This 24 km2 island is surrounded by a protected marine area of 9640 km2. it was declared National Park in 1978 and a...
Freshwater macroinvertebrates from Cocos Island, Costa Rica: species and comparison with other islands of the Eastern Tropical Pacific. Cocos Island is an oceanic island in the Eastern Pacific, at 496km from Cabo Blanco, Costa Rica. This 24km 2 island is surrounded by a protected marine area of 9 640km 2. It was declared National Park in 1978 and a...
Eighty-six water samples were collected in early 2009 from Costa Rican surface water and coastal locations for the analysis of 34 pharmaceutical and personal care product compounds (PPCPs). Sampling sites included areas receiving treated and untreated wastewaters, and urban and rural runoff. PPCPs were analyzed using a combination of solid phase ex...
Little information exists about the consequences of hydropower production in tropical areas, especially during the operational phase. In Latin America, hydroelectric energy is the primary method of fulfilling growing electrical demands. Most large dams (>15m in height) currently under construction or consideration are in the tropics. We investigate...
The aim of the present paper is to provide first information on the mangrove fish community of the tropical fjord-like Golfo
Dulce (GD), to study its importance for fish diversity and fisheries in the area and to give preliminary results on its spatial–temporal
variation. Eighty-two species belonging to 30 families were identified. More than half o...
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...
Fish monthly samples were made in three tributaries and in the main stream in order to study population dynamics and the influence of flow on abundance of Agonostomus monticola (Mugilidae) and Brycon behreae (Characidae) in the basin of Térraba River Basin (Costa Rica). Flow was seasonal in these rivers, with peak flow in October. Recruitment was d...
Crater lakes share some morphological characteristics such as size, shape, situation inside a crater, usually high elevation, which have a definite impact on their limnology. In Costa Rica there are several crater lakes that may serve as an example of small tropical lakes to examine some relationships between morphometry and stratification. The res...
The behavior of the water column of Arenal Reservoir, a tropical reservoir in Costa Rica, is analyzed based on temperature and dissolved oxygen data gathered on a monthly to bimonthly basis between 1986 and 1992. The depth profiles of temperature at Arenal Reservoir show the typical asymmetry of reservoirs, with a greater stratification in its deep...
Rio Grande de Terraba drains one of the largest basins in Costa Rica, with a growing human population. It has been deforested in its lower region for the development of agriculture, but has attracted little attention on its environmental challenges. The river was studied once in the dry and wet season for a period of four years (1999-2003). A total...
Epilithic diatom assemblages from neotropical streams draining into Golfo Dulce (Costa Rica) were studied to determine how diatoms were related to measured environmental conditions. Twenty-three sites, affected by different land use practices, were selected and monitored for 21 months. Water chemistry was characterized by moderate specific conducti...
Environmental variation in the Grande de Térraba river and some of its tributaries, south Pacific coast of Costa Rica. Río Grande de Térraba drains one of the largest basins in Costa Rica, with a grow- ing human population. It has been deforested in its lower region for the development of agriculture, but has attracted little attention on its envir...
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 CO2, but low in dissolved O2; one of these, L...
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...
Basic physico-chemical parameters and benthic invertebrate diversity were measured from several streams that drain into the Golfo Dulce (southern Pacific coast of Costa Rica) during 1996-1997. A total of 15 sites were visited in the Osa Peninsula, and the Esquinas and Coto-Colorado river basins, all under 100 m in altitude. Dissolved oxygen and sus...
Lago Bonilla, located 370 m above sea level on the Eastern slopes of Volcan Turrialba, Costa Rica, was visited four times during 1990-1991. Basic limonological data were recorded in each visit. It is oligomictic, mixing during the coldest and windiest months sometime between Nov. and Feb. and eutrophic, with low Secchi transparencies, Cyanobacteria...
The vertical distribution of Bomina, Daphnia, Ceriodaphnia, Diaptomus and cyclopoids was studied for a 48 hours period in Arenal Reservoir, Costa Rica. In general the zooplankton decreased during day time across the water column. Daphnia, Diaptomus and the cyclopoids had a constant depth distribution with time, whereas Bosmina, and Ceriodaphnia sho...
We sampled 30 lakes in Costa Rica in the wet season (July–August) of 1991 for phytoplankton (with integrated and whole water samples), and 17 for zooplankton (with net tows). Taxa of plankton and community richness were poorly related to geography, morphology, chemistry, and other biota. Neither the zooplankton nor the phytoplankton appeared to inf...
This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right.
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 po...
Questions
Questions (7)
I have found this Staurastrum species in a reservoir in Costa Rica. The variation goes from cells with three arms on both hemicells, four single arms, and four double arms in either both or one of the hemicells. I wonder whether this variation could be the result of some kind of water pollution. I appreciate any thoughts about this case.
We find different Rotifers in reservoirs and lakes in Costa Rica. Species composition in some reservoirs seem to change a lot with time, perhaps as a result of the dynamic nature of reservoirs, as they are used for water storage and use. We found these Rotifers, which we think are, a Monostyla species and a Brachionus species, but we are not so sure... Would any one help with these identification?
We found these Rotifer abundant in a lake from Costa Rica, but we are having trouble identifying it. We think it belong to the genus Ploesoma, but we're not so sure...
We found this rotifer in Arenal Reservoir, Costa Rica. We've been trying to identify it, but the rear end does not seem to conform with usual pictures or drawings of the two most likle genera: Ascomorpha or Asplanchna. We just want a confirmation of our most likely bet: Ascomorpha. We appreciate any sugestions. Thanks!
This Bosmina was found in Arenal Reservoir, Costa Rica. It is apparentl infected by a fungi, and we are interested to know if there is any experience about this condition, and if ti means something about the environmental condition of the lake.
This small crustaceaen appeared in a zooplankton sample from a small reservoir in Costa Rica. Unfortunately we were not able to find it again to take a better picture. We would appreciate any hints about its identity.
The zooplankton net probably touched the bottom or the littoral zone before the hawling because the sample contained some organic debris, whcih could be observed to the left of the organim.
Other individuals were observed more stretched, so we think it is a Bdelloid Rotifer.
It was caught in a net haul in a shallow, small eutrophic reservoir in Costa Rica.
Note that the scale bar should be 50 microns, instead of 10!
Projects
Projects (2)
Ajustar el índice LIFE para Costa Rica, asociando a los macroinvertebrados acuáticos a una categoría de flujo