Aquatic macro invertebrate community composition differences between the Atlantic and Pacific watersheds in Monteverde, Costa Rica Tim Curry Department of Environmental Studies, University of Colorado ABSTRACT There are large differences between slope seasonality in Monteverde, Costa Rica. The Pacific slope receives less rainfall, and has a better defined wet and dry season. This study look ed at how these differences affect aquati c benthic macro invertebrates composition. Fiv e different rivers were sampled , three on the Atlantic slope, and two on the Pacific slope . There was no significant difference between the two slopes in species richness, evenness, or number of species. There were differences in species composition between the two slopes. Thi s study exemplifie s how areas in close proximity can have differe n t species compositions. For conservation purposes, this study demonstrates how even if a large area is being protected not all species in the surrounding area are necessarily protected. RESUMEN Existen grandes diferencias entre la estacionalidad en ambas vertientes en Monteverde, Costa Rica. La vertiente PacÃfica recibe menos precipitaciÃ³n y tiene una estaciÃ³n seca y humeda mÃ¡s definida. Este estudio observa como estas diferencias afec tan lacomoposiciÃ³n de macroinvertebrados bÃ©nticos. Cinco quebradas diferentes se muestrearon, tres en el AtlÃ¡ntico y dos en el PacÃfico. No hay diferencias significativas entre las dos vertientes en cuanto a riqueza, similitud o nÃºmero de especies. Exis ten diferencias en la composiciÃ³n de especies entre las dos vertientes. Este estudio ejemplifica como Ã¡reas prÃ³ximas pueden tener una composiciÃ³n de especies diferente. Para objetivos de conservaciÃ³n este estudio demuestra como aunque un Ã¡rea larga sea pr otegida no todas las especies del Ã¡rea estÃ¡n necesariamente protegidas INTRODUCTION There is a large seasonal difference between the Atlantic and Pacific sl ope in Mo nteverde, Costa Rica (Guswa et al. 2007 ). The largest changes in seasonality are not in temperature, but in precipitation ( Janzen 1983) . These changes in precipitati on are driven by the windward leeward effect created by the wind blowing from the east to the west . The Pacific slope has a well defined wet and dry season, while the Atlantic s lope has fairly constant rainfall year round (Nadkarni & Wheelwright 2000) . The Pacific slope of Monteverde receives 77% of its rainfall during the wet season with an annual rainfall of 2700 mm (Guswa et al. 2007). The Atlantic slope on the other hand receives up to 3500 mm of rainfall annually above 1400m , while places below 1400m can receive up to 7000 mm of rainfall annually ( Nadkarni & Wheelwright 2000) . Streams in Monteverde are able to maintain flow year roun d through two processes. One is through flow, and the other is stream interception with the water table ( Nadkarni & Wheelwright 2000) . These two processes are pivotal on the Pacific slope,
especially during the dry season. Precipitation year round on th e Atlantic slope helps feed the streams, taking some pressure off of the two previous processes. Water quality can also have huge swings between the wet and dry season. Oxygen content is generally lower during the dry season (Chapman & Kramer 1991). Th ese Monteverde streams are important habitat for benthic macro invertebrates. In Costa Rica aquatic insects are one of the most diverse group of organisms (Springer 2009 ). Insects are also important because they have fast generation times, and can be early accurate representations of ecological changes (Kremen et al. 1983) . This makes macro invertebrates an im portant warning system, which should not be ignored. It is important to know what species exist where to take full advantage of their conservat ion potential. In this project the differences between the Atlantic and Pacific slope aquatic benthic macro invertebrate diversity were examined. The findings in this paper can help express the importance of not only conserving large areas, but also makin g sure that these areas include important elem ents of all the ecosystems/life zones present. METHODS S TUDY SITE In this study five different streams were sampled . All five streams were within the Monteverde area in Costa Rica. Three were on the Atlantic side of the continental divide, the Rio Negro (Fig. 1) , Quebrada CaÃ±o N egro, and Quebrada P eligro (Fig. 2) . Two on the Pacific side were the Quebrada M Ã¡quina and Queb rada Cuecha (Fig. 1) . The Rio Negro, Quebrada Ca Ã±o Negro, and Quebrada Peligro are in premontane rain forest. While the Quebrada M Ã¡quina and Queb rada Cuecha are in lower montane wet forest. These areas are a combination of secondary and primary forest s (Nadkarni & Wheelwright 2000) . Each stream w as sampled at four different locations. The site s were staggered 100m away from each other. Sa mpl es were taken between 141 0 1 574 m in elevation. A GPS was used to ensure accuracy in elevation. Sites were picked base d on how similar the substrate wa s at that location in comparison to other sampling locations. The substrates that were looked for we re leaf litter, rocks, and pools . FIGURE 1. A map of the study area. Rivers marked with arrows include: Rio Negro (ARN), Quebrada M Ã¡quina (PQM), and Quebrada Cuecha (PQC).
D ATA COLLECTION Sampling took plac e for 60 minutes, or until 100 macro invertebrates were obtained from each sample site . Samples were collected using a strainer, placed in white plastic tray , pulled out with tweezers . Then each insect was placed into a container filled with 70% ethanol , the ethanol kill ed and preserve d the samples. Samples were then brought back to the Bi ological Research Station for identification. The samples were identifie d using an aquatic insect guide and a dissecting scope . At each sampling site seve ral abiotic measurements were measured as well including; water temperature, stream depth, turbidit y, dissolved oxygen content (DOC) , carbon dioxide, pH, alkalinity, and nitrate . Water temperature was measured using a thermometer. A colorimeter was us e d to measure turbidity . DOC was measured using a dissolved oxygen content reader . A carbon d ioxide water quality kit was used to test for carbon dioxide. A water quality strip test was used to measure pH , alkalinity, and nitrate . RESULTS B IOTIC F ACTORS There was a total of 1225 insects collected. This consisted of 8 different orders and 40 different families. There were 33 families on the Atlantic slope, and 30 families on the Pacific slope. Some of the most abundant families include; Leptoceridae, Perlidae, Veliidae, Leptophebiidae, and Simuliidae (Table 1). There was no significant diff erence in diversity between the streams (ANOVA , F = 0.1075, DF = 4, p = 0.11 ; Table 1 ). Evenness between streams was not significantly different (One Way ANO VA, F=0.8273, DF = 4, p = 0.5 ). Number of species between streams was also not significant ly diff erent (One Way ANOVA, F = 2.8134, DF = 4, p = 0.0633). However it still shows an interesting trend that the streams all had similar numbers of species. FIGURE 2. A map of the study area. Rivers marked with arrows include Quebrada CaÃ±o Negro (AQCN) and Quebrada Peligro (A QP).
There was no significant difference between diversity on the two different slopes (One Way ANOVA, t te st = 1.118, DF = 18, p = 0.28). Evenness between slopes had no significant difference (One Way ANOVA, t test = 1.751, DF =18, p = 0.10). The number of species between slopes was not significant (One Way ANOVA, t test = 0.080, DF = 18, p = 0.94). However, while there was no significant difference in the number of species there were di ffe rences in composition (Fig. 3 ; Table 1). In the hierarchical clustering the greatest clustering occurred between the same slopes. Clusters with closer distances are more similar in composition, while sites that are clustered together further out are less similar in composition. The Atlantic slope had 10 unique species of which 8 were unique to a single stream. The Pacific slope had 7 unique species of which 5 were unique to a single stream. F IGURE 3 . Cluster analysis (ward method similarity) of aquatic insect families grouped by streams in Atlantic and Pacific slopes in Monteverde, Costa Rica. Streams (initials) that start with A are in the Atlantic, P in the Pacific slope.
A BIOTIC F ACTORS When abiotic factors were compared between all sites in the five rivers, very few trends were found. Water temperature ranged from 15.5 Â° C t o 17.1 Â° C , while pH ranged from 6.4 to 6.7. Turbidity was very low, and ranged from 0 to 9 Formazin Turbidity Units (FTU). Dissolved oxygen was fairly regular and ranged b etween 8.38 mg/L and 10.73 mg/L, while c arbon dioxide ranged between 10.81 parts per million (ppm) and 15 ppm. Alkalinity r anged between 20 ppm and 60 ppm, and n itrates ranged between 0 ppm and 40 ppm . Both Alkalinity and nitrates were fairly low. There was a negative correlation between carbon dioxide and elevation ( Pearson rank corre lation , r = 0. 6242, n = 20, p = 0.0033, Fig. 4 A). There was a negative correlation between dissolved oxygen and water temperature ( Pearson rank correlation, r = 0. 5073, n = 20, p = 0.0224, Fig. 4 B). There was a positive correlation between carbon dioxi de and water temperature ( Pearson rank correlation, r = 0. 4504, n = 20, p = 0.0463; Fig. 4 C). There was a positive regression between number of species and water temperature (regression = 0. 4762, n = 20, p = 0.0338; Fig. 5 ). Ther e was no significant reg ression between species diversity and elevation ( regression = 0. 4762, n = 20, p = 0.0338; Fig. 6 ). 4 6 8 10 12 14 16 18 15 15.5 16 16.5 17 17.5 S Water Temperature (C) F IGURE 4 . Correlation (r) between several abiotic factors measured in stream, Monteverde, Costa Rica. All comparisons are significantly different than 0. F IGURE 5 . Regression between number of species and an increase in water temperature ( Â° C) , Monteverde, Costa Rica (y = 2.6649x 30.435, R 2 = 0.22678). All comparisons are significantly different than 0.
DISCUSSION There were no differences a t both slope level and stream level in relation to species diversity, evenness, and number of species . However there were chan ges in the composition of species present. In the Atlantic there were nine unique famil ies, while the Pacific had seven unique families. In the hierarchical clustering all of the Atlantic sites were clumped closer together, with the except ion of one stream. The one stream that was clumped closer with the Pacific sites , ARN4, was missing several common families in the Atlantic such as Psephenidae and Naucoridae. It also had several families that were more common on the Pacific slope, Cordulegastridae and Ptilodactylidae. The Pacific sites had two outliers PQM1 and PQM2. PQM 1 is missing several common families in the Pacific such as Baetidae, Leptoceridae, Leptophebidae, Naucoridae, and Perlidae. PQM1 also had two families unique to that site, Curcolionidae and Culicidae. PQM2 was missing three common families, Simuliidae , Veliidae, and Leptohyphidae. It is possible that t he mountain range is a physi cal barrier for these species, and that these species occupy similar niches in their respective ranges. These species might also be checkerboard species . Because there was no significant difference in species diversity, evenness, or number of species , all of the streams probably have similar community carrying capacities. When compared with previous studies this study had similar or more families of aquatic macro invertebrates. For example, in a similar study done in fall 2008 only 26 different families were found, 19 different families on the Atlantic slope, and 17 on the Pacific (Gor don 2008). In another study conducted in fall 2009, 21 different families were found in two Atlantic slope streams (Burnett, 2009). In this study 40 different families were found, with 33 families found on the Atlantic, and 30 families found on the Pacif ic slope. A third study conducted in 2009 along the Quebrada M Ã¡ quina identified 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 1400 1450 1500 1550 1600 H' Elevation (m) F IGURE 6 . Regression between species diversity and elevation (m), Monteverde, Costa Rica (y = 0.0012x + 0.205, R 2 = 0.12536). All comparisons are significantly different than 0.
24 families, in this study 25 different families were identified (Skaff 2009). However, some of the differences associated with the different number of macro invertebrates o n the Atlantic slope might have to do with seasonality. This is because all three previous studies took place during the fall , which is during the wet season. There was a significant correlation between carbon dioxide and elevation. This correlation cou ld be explained by aerobic respiration. This would explain why at lower elevations there is a higher level of carbon dioxide, there has been more time for the carbon dioxide to accumulate. There was also a negative correlation between water temperature a nd dissolved oxygen. This is consistent with the common knowledge that warmer water cannot hold as much dissolved oxygen. There was a positive correlation between water temperature and carbon dioxide. Carbon dioxide and dissolved oxygen are inversely pr oportional, and thus would explain why there is a positive correlation while water temperature and dissolved oxygen had a negative correlation (Ruttner 1975). There was a positive correlation between number of species and water temperature. Water temper ature increases may fall into an optimal growth range for more species. While there was not a significant correlation there was still a relationship between species diversity and elevation. As elevation increases the difference between the mean maximum a nd minimum gets smaller (Janzen 1983). This creates a more stable temperature. This stability allows for higher spec ies diversity (Death & Winterbourn 1995 ) . ACKNOWLEDGEMENTS I would like to thank Pablo Allen for being my advisor , helpi ng with all of the steps and processes, and putting up with all of my shenanigans. I would also like to Anjali Kumar for helping me find the streams I wanted to use. Alan Masters for his general awesomeness. Al so thank you to Moncho CalderÃ³n and Ana Gis ella FernÃ¡ndez Estrada for answering all of questions , and helping with a variety of other task . Jacob Cravens for helping me sample at La Reserva de Santa Elena. I would like to thank Emily Ellison for helping take pictures of my project. Finally I wo uld like to thank Katie Johnson for peer reviewing my paper. LITERATURE CITED B URNETT , A. S.. 2009. The Effects of Land Use on Stream Water Quality in San Luis and Ca Ã± itas. Tropical Ecology and Conservation Council on International Education Exchange Fall 2009: 250 260. C HAPMAN , L. J . , and D. L . K RAMER . 1991. Limnological observations of an intermittent tropical dry forest stream. Hydrobiologia 226: 153 166. D EATH R. G., and M. J. W INTERBOURN . 1995. Diversity Patterns in Stream Benthic Invertebrate Communities: The Influence of Habitat Stablity. Ecology 76: 1446 1460.
G ORDON , E.. 2008. A comparison of macro invertebrate diversity and composition on the Pacific and Atlantic slopes of Costa Rica. Tropical Ecology and Conservation C ouncil on International Education Exchange Fall 2008: 67 75. G USWA, A. J., A. L . R HODES , and S. E. N EWELL . 2007 . Importance of orographic precipitation to the water resources of Monteverde, Costa Rica. Advances in Water Resources 30: 2098 2112. J ANZEN , D. H.. 1983. Costa Rican Natural History. pp 37 45. The University of Chicago Press, Chicago, United States. K REMEN , C., R. K. C OLWELL, T. L. E RWIN , D. D., M URPHY, R. F. N OSS , and M. A . S ANJAYAN . 1983. Terrestrial Arthropod Assemblages: Their Use in Conservation Planning. Conservation Biology 7: 796 808. N ADKARNI , N. M., and N. T. W HEELWRIGHT . 2000. The Physical Environment. Monteverde: Ecology and Conservation of a Tropical Cloud Forest. pp. 41 42 , 90 Oxford University Press, New York, United States. R UTTNER , F.. 1975. Fundamentals of Limnology. pp. 74 University of Toronto Press, Toronto, Canada . S KAFF , N.. 2009. The Applicability of the River Continium Concept to the Upper Reaches of a Neo tropical Lower Montane Stream. Tropical Ecology and Conservation Council on International Education Exchange Fall 2009: 107 117. S PRINGER, M ., 2009. Aquatic insect diversity of Costa Rica: state of knowledge. Revista de Biolog Ãa Tropical 56: 273 295 .
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Diferencias en la composicin de la comunidad de Macroinvertebrados acuticos entre las cuencas hidrogrficas del Atlntico y el Pacfico, en Monteverde, Costa Rica
Aquatic macro-invertebrate community composition differences between the Atlantic and Pacific watersheds in Monteverde, Costa Rica
There are large differences between slope seasonality in Monteverde, Costa Rica. The Pacific slope receives less rainfall, and has a better-defined wet and dry season. This study looked at how these differences affect aquatic benthic macro-invertebrates composition. Five different rivers were sampled, three on the Atlantic slope, and two on the Pacific slope. There was no significant difference between the two slopes in species richness, evenness, or number of species. There were differences in species composition between the two slopes. This study exemplifies how areas in close proximity can have different species compositions. For conservation purposes, this study demonstrates how even if a large area is being protected not all species in the surrounding area are necessarily protected.
Existen grandes diferencias entre la estacionalidad en ambas vertientes en Monteverde, Costa Rica. La vertiente Pacfica recibe menos precipitacin y tiene una estacin seca y hmeda ms definida. Este estudio observa como estas diferencias afectan la composicin de los macroinvertebrados bnticos. Se muestrearon cinco quebradas diferentes, tres en el Atlntico y dos en el Pacfico. No hay diferencias significativas entre las dos vertientes en cuanto a riqueza, similitud o nmero de especies. Existen diferencias en la composicin de especies entre las dos vertientes. Este estudio ejemplifica como las reas prximas pueden tener una composicin de especies diferentes. Para objetivos de conservacin este estudio demuestra que aunque hay un rea larga que est siendo protegido no todas las especies del rea estn siendo necesariamente protegidas.
Text in English.
Costa Rica--Puntarenas--Monteverde Zone
Costa Rica--Puntarenas--Zona de Monteverde
Tropical Ecology Spring 2011
Watershed health indicators
Ecologa Tropical Primavera 2011
Indicadores de salud de cuenca
t Monteverde Institute : Tropical Ecology