Benthic Macroinvertebrates of Temperate, Sub-Antarctic Streams: The Effects of Altitudinal Zoning and Temperature on the Phenology of Aquatic Insects Associated to the Robalo River, Navarino Island (55°S), Chile Page: 86
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Determination of Cumulative Degree Days and Growing Degree Days
Average daily water temperature (C) was calculated for each site using the information
retrieved from the Hobo data loggers. Temperature information from site I (586 m.a.s.1) was
not retrieved, therefore temperature (C) data for sites II-V (486-120 m.a.s.1) is presented.
Cumulative Degree- Days (CDD) for each site were computed by summing the daily average
temperature (C) by month and for a period of 1 year, following (Snyder et al. 2001). Growing
Degree-Days (GDD) were estimated by summing the daily average temperature (C) starting at
the period at which we observed a proportionally higher number of first developmental stage
nymphs and finishing at the period at which we observed a proportionally higher number of fifth
developmental stage nymphs.
Estimation of Voltinism through the Altitudinal Gradient
Cohort lines and voltinism were estimated through the altitudinal gradient by obtaining
the CDD for each site by month. Using the results of the approximate GDD obtained from site V
(120 m.a.s.1), the number of generations (cohorts) that could be possible for each site related to
its total number of CDD during a one-year period were estimated.
Estimation of Historical Water Temperature (C) and Voltinism
As explained before, Cumulative Degree- Days (CDD) are computed by summing the
daily average temperature (C) during a determined time period (Snyder et al. 2001). Historical
CDD (2006-2011) for site V were obtained, by obtaining water and air temperature data (C)
from a permanent meteorological site (managed by Chile's Direcci6n General de Aguas (DGA))
located at this altitude. Although water and air temperature data are readily available for general
access through DGA's website, daily water temperature data for large periods of times is86
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Contador Mejías, Tamara Andrea. Benthic Macroinvertebrates of Temperate, Sub-Antarctic Streams: The Effects of Altitudinal Zoning and Temperature on the Phenology of Aquatic Insects Associated to the Robalo River, Navarino Island (55°S), Chile, dissertation, December 2011; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc103303/m1/100/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .