5/21/2015  |   15:30 - 15:45   |  101B

SUBSIDIES FROM AQUATIC TO RIPARIAN CONSUMERS ALONG AN URBAN GRADIENT IN A TROPICAL WATERSHED – A STABLE ISOTOPE ANALYSIS Emerging aquatic insects represent an important food source for many riparian consumers and stable isotope analyses have been a driving force in determining the importance of the flow of subsidies between aquatic and terrestrial ecosystems. Studies have shown that streams are strongly linked to their adjacent riparian areas and impacts in either habitat can have an effect on the biota of the recipient system. Urbanization has a myriad of effects on stream ecosystems, such as increased runoff from impervious surfaces, channelization and impacts to the riparian zone. In this study we conducted stable isotope analyses for tetragnathid spiders and their potential prey along an urban watershed that passes through the heart of the greater San Juan metropolitan area of Puerto Rico. The aim of the study was to find how the importance of aquatic subsidies for riparian consumers may be altered by changes along an urban gradient. We found distinct variation in surrounding urban densities among different stream sections that resulted in changes to the riparian zone however aquatic subsidies remained an important energy source for tetragnathids.

Sean Kelly (Primary Presenter/Author), University of Puerto Rico-Rio Piedras, spkelly.84@gmail.com;


Alonso Ramírez (Co-Presenter/Co-Author), North Carolina State University, alonso.ramirez@ncsu.edu;

5/21/2015  |   15:45 - 16:00   |  101B

HOW TOLERANT ARE TROPICAL STREAM MACROINVERTEBRATES TO DROUGHT-DRIVEN ACIDIFICATION ASSOCIATED WITH CLIMATE CHANGE? The severity of drought-driven stream acidification may increase worldwide in response to increased drought frequency and intensity resulting from climate change. Some lowland Neotropical streams experience seasonal acidification and are particularly vulnerable to extreme drought-driven acidification. We conducted laboratory experiments to determine thresholds of pH effects on growth/survival of three stream macroinvertebrate taxa at La Selva Biological Station, Costa Rica: mayfly naiads (Traverella holzenthali), chironomid larvae (Chironominae), and adult shrimp (Macrobrachium olfersii). To determine possible local adaptation, we compared effects of pH on growth/survival of larval chironomids from two different streams: a typical poorly-buffered stream (pH 4.32-6.94) and a naturally well-buffered stream receiving high-bicarbonate regional groundwater (pH 5.11-6.92). Chironomid growth and survival were unaffected by pH >3.5, indicating tolerance to pH levels experienced in poorly-buffered streams. However, mayflies and shrimp showed decreased tolerance to the lowest pH levels (3.6-4.0) recorded during an extreme climatic (ENSO) event, suggesting that increasingly severe drought-driven acidification could negatively affect macroinvertebrate survival. These findings signal the need for further research on macroinvertebrate tolerance thresholds in streams worldwide where drought-driven pH declines are probable.

Carissa Ganong (Primary Presenter/Author), Missouri Western State University, carissa.ganong@gmail.com;


Minor Hidalgo Oconitrillo (Co-Presenter/Co-Author), Organization for Tropical Studies, minor.hidalgo@ots.cr;


Catherine Pringle (Co-Presenter/Co-Author), Odum School of Ecology, University of Georgia, cpringle@uga.edu;

5/21/2015  |   16:00 - 16:15   |  101B

DISTURBANCE AS A KEY FACTOR IN UNDERSTANDING MACROINVERTEBRATE ASSEMBLAGE DYNAMICS IN NEOTROPICAL STREAMS Natural and anthropogenic disturbances are common and important phenomena affecting stream ecosystems and play key roles determining benthic macroinvertebrate assemblage dynamics. Moreover, understanding macroinvertebrate responses to disturbance is the basis of biomonitoring efforts. While we still have much to learn about macroinvertebrate responses to both disturbance types, we have little information on the interaction between the two. How do natural disturbances affect our ability to evaluate the ecological condition of streams? Here we explore our understanding of the importance of disturbances in structuring macroinvertebrate assemblages in neotropical streams. We use information from our long-term monitoring studies in lowland streams in Costa Rica to highlight the importance of hydrological disturbances in shaping macroinvertebrate assemblages. Information from urban studies in Puerto Rico provide context for the importance of anthropogenic disturbances and for the interactions between these and natural disturbances. Overall, disturbances create complex dynamics in macroinvertebrate assemblages, often with changes in composition and abundance. However, the potentially complex interaction between natural and anthropogenic disturbances and their effects on macroinvertebrates remain an open field of study.

Alonso Ramírez (Primary Presenter/Author), North Carolina State University, alonso.ramirez@ncsu.edu;

5/21/2015  |   16:15 - 16:30   |  101B

DISTURBANCE AS A KEY FACTOR IN UNDERSTANDING MACROINVERTEBRATE ASSEMBLAGE DYNAMICS IN NEOTROPICAL STREAMS Natural and anthropogenic disturbances are common and important phenomena affecting stream ecosystems and play key roles determining benthic macroinvertebrate assemblage dynamics. Moreover, understanding macroinvertebrate responses to disturbance is the basis of biomonitoring efforts. While we still have much to learn about macroinvertebrate responses to both disturbance types, we have little information on the interaction between the two. How do natural disturbances affect our ability to evaluate the ecological condition of streams? Here we explore our understanding of the importance of disturbances in structuring macroinvertebrate assemblages in neotropical streams. We use information from our long-term monitoring studies in lowland streams in Costa Rica to highlight the importance of hydrological disturbances in shaping macroinvertebrate assemblages. Information from urban studies in Puerto Rico provide context for the importance of anthropogenic disturbances and for the interactions between these and natural disturbances. Overall, disturbances create complex dynamics in macroinvertebrate assemblages, often with changes in composition and abundance. However, the potentially complex interaction between natural and anthropogenic disturbances and their effects on macroinvertebrates remain an open field of study.

Alonso Ramírez (Primary Presenter/Author), North Carolina State University, alonso.ramirez@ncsu.edu;