Tropical Ecology and Conservation [Monteverde Institute]

Creator

Julia Goldstein

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Publication Date

June 2006

Abstract

The construction of dams to satiate human year-round water needs has been so extensive in the past 50 years that small streams are some of the world’s only water flows to still run unregulated (Allan, 1995; Vitousek et al., 1997). That said, plenty of small stream water regimes are regulated, and the effects of this on biodiversity are under-investigated, especially in the tropics (Allan, 1995). In this study the effects of a small dam on the physical environment and macroinvertebrate communities of a tropical montane stream, the Quebrada Máquina, in Monteverde, Costa Rica, were analyzed. Substrate composition, temperature and macroinvertebrate diversity were measured between April 8 and May 4, 2006. I collected1592 macroinvertebrates and identified them to family and morphospecies level, over two-thirds of these individuals coming from the order Diptera. On a biological level, the numbers of orders and morphospecies decreased significantly as distance to the dam decreased. Physically, temperature increased significantly between 50 m upstream of the dam and 50 m downstream. Relative percentage of sand as substrate (RPSS) decreased significantly as distance from the dam decreased, and sediment as a substrate increased significantly at sites closer to the dam. While some of this study’s conclusions are unique to the Quebrada Máquina, many of its findings are universal to stream-dam situations. Taking what can be generalized from this experiment, I propose conservation strategies relevant to all dammed aquatic ecosystems. La construcción de represas durante los últimos 50 años ha sido tan extensa que las quebradas pequeñas son de las únicas fuentes de agua que corren sin regulación alguna (Allan, 1995; Vitousek et al., 1997). Sin embargo, muchas quebradas pequeñas son reguladas, y los efectos de esta actividad en la biodiversidad no han recibido mucha atención científica, especialmente en los trópicos (Allan, 1995). En esta investigación se analizaron los efectos de una represa pequeña en el ambiente físico y en las comunidades de macroinvertebrados de una quebrada tropical y montañosa, la quebrada Máquina, en Monteverde, Costa Rica. Se midió la composición del sustrato, la temperatura y la diversidad de macroinvertebrados entre el 8 de abril y el 4 de mayo del 2006. Se colectaron1592 macroinvertebrados y se identificaron a los niveles de familia y especie morfológica; más de las dos terceras partes de la muestra pertenecieron al orden Diptera. Biológicamente, los números de órdenes y especies morfológicas disminuyeron significativamente en sitios cercanos a la represa. Físicamente, la temperatura aumentó significativamente entre los 50 m arriba de la represa y los 50 m debajo de la represa. El porcentaje relativo de arena como sustrato (PRAS) disminuyó significativamente en sitios cercanos a la represa y el sedimento como sustrato subió significativamente en estos mismos sitios. Aunque algunas de las conclusiones solamente pueden ser aplicadas a la quebrada Máquina, muchas otras son comunes a sistemas de quebradas con represas. Se proponen estrategias de conservación aplicables a todos los ecosistemas acuáticos con represas basadas en generalizaciones inferidas de los resultados obtenidos.

Description

Student affiliation : Department of Neuroscience, Pomona College Born Digital

Genre

Reports

Holding Location

Monteverde Institute IMVI

Identifier

M39-00287

Streambed substrate composition and macroinvertebrate communities in the presence of a dam

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