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Papers by Melanie Goral
The effect of wind on lakes has undergone many changes since the early 1900's. There are three ma... more The effect of wind on lakes has undergone many changes since the early 1900's. There are three major areas of development in wind research: theories and knowledge, methodology and the presentation of data. Wind stress exerted on the surface layers of stratified lakes have been studied and developed to incorporate the topography, size and depth of lakes. A variety of methods to study wind stress on lakes have been performed and developed to assist the growing state of knowledge regarding wind effects on lake ecosystems. The presentation of wind data is advancing much slower relative to the previous areas of development. In examination of the major areas of wind research development, further attention should be directed to the following issues: (1) increasing high-resolution technology to better monitor wind stress on lakes; provide deeper understandings of food web interactions and lake characteristics to avoid lake deterioration caused by extreme wind events (storms); and (3) improvement of wind research accuracy in order to forecast general changes in climate.
Thesis Chapters by Melanie Goral
Zooplankton ecologists have generated a large number of multi-decade, mid-lake, zooplankton datas... more Zooplankton ecologists have generated a large number of multi-decade, mid-lake, zooplankton datasets, but the long-term dynamics of zooplankton heterogeneity induced by wind-driven currents has never been explored. If wind speed or direction changes over time, then the distribution of animals may also change, and abundance assessed at a single station may have changed with the wind field. In this study, I determine if changes in the annual averages of the abundance of 4 Cladoceran, 2 Calanoid and 2 Cyclopoid species in Harp Lake, Ontario, were related to the wind field (speed and direction) between 1980 and 2004. Zooplankton data were generated from a volume-weighted composite of multiple vertical hauls taken from a single station at the deepest point of the lake. Wind speed has decreased, on average by 25%, while wind direction has shifted by 21 degrees towards the north. In order to assess if the variation in abundance was influenced by this change in the wind field, I first needed to correct for the other known long-term changes in lake's zooplankton. Hence, to consider how annual climatic differences might have influenced the community, I began by regressing zooplankton abundance against the presence/absence of Bythotrephes, the average number of days since spring ice break-up, and the average surface temperature on sampling days. I then determined if the residual variation in average zooplankton abundance from these models was correlated with the wind. Despite long-term changes in the wind field, linear-linear (speed) and linear-circular (direction) correlations of annual residual abundance of 7 of 2 the 8 species were not predictable from the wind fields using the averages of the sample day. The exception was D. mendotae, for which residual abundance was correlated with wind direction (r 2 =0.2300, p=0.005) meaning that the high residual abundance was correlated with a particular wind direction. D. mendotae is a large, fast swimming cladoceran that may be predictably responding under turbulent mixing and the resulting thermocline tilting in the hypolimnion. In summary, on an annual basis, long-term changes in zooplankton abundance were not improved by changes in the wind field.
The predictability of zooplankton abundance under wind-driven currents has been explored, but wha... more The predictability of zooplankton abundance under wind-driven currents has been explored, but what has not been explored is how the distributions change over the longterm in response to changes in wind fields. In this study, I sought relationships between the wind field and fortnightly abundances of 8 zooplankton species at a mid-lake station in Harp Lake, Ontario from 1980 to 2004. Over this time period, average wind speed has declined by 25%, which is consistent with the long-term trends over the Northern Hemisphere (Vautard et al. 2010), while direction has shifted 21 degrees towards the north. Multiple linear regressions were generated to predict seasonal and interannual changes in daily zooplankton abundance combining year, Julian day, chemistry and, finally, wind speed and direction. Wind field metrics were included in the models for 6 of the 8 species, although improvements in predictive power were modest. We suspect that the decrease in wind speed has contributed to a change in zooplankton heterogeneity in the lake, and thus a change in lake-wide abundance estimates derived from a single station. Zooplankton are patchily distributed, but most long-term monitoring programs sample only at one station. My work suggests that we may well be able to correct for some of the bias due to a changing wind field, and make small but significant improvements in the predictability of abundance of zooplankton species if we consider wind as a driver.
The errors associated with using daily data
Teaching Documents by Melanie Goral
Talks by Melanie Goral
The effect of wind on lakes has undergone many changes since the early 1900's. There are three ma... more The effect of wind on lakes has undergone many changes since the early 1900's. There are three major areas of development in wind research: theories and knowledge, methodology and the presentation of data. Wind stress exerted on the surface layers of stratified lakes have been studied and developed to incorporate the topography, size and depth of lakes. A variety of methods to study wind stress on lakes have been performed and developed to assist the growing state of knowledge regarding wind effects on lake ecosystems. The presentation of wind data is advancing much slower relative to the previous areas of development. In examination of the major areas of wind research development, further attention should be directed to the following issues: (1) increasing high-resolution technology to better monitor wind stress on lakes; provide deeper understandings of food web interactions and lake characteristics to avoid lake deterioration caused by extreme wind events (storms); and (3) improvement of wind research accuracy in order to forecast general changes in climate.
Zooplankton ecologists have generated a large number of multi-decade, mid-lake, zooplankton datas... more Zooplankton ecologists have generated a large number of multi-decade, mid-lake, zooplankton datasets, but the long-term dynamics of zooplankton heterogeneity induced by wind-driven currents has never been explored. If wind speed or direction changes over time, then the distribution of animals may also change, and abundance assessed at a single station may have changed with the wind field. In this study, I determine if changes in the annual averages of the abundance of 4 Cladoceran, 2 Calanoid and 2 Cyclopoid species in Harp Lake, Ontario, were related to the wind field (speed and direction) between 1980 and 2004. Zooplankton data were generated from a volume-weighted composite of multiple vertical hauls taken from a single station at the deepest point of the lake. Wind speed has decreased, on average by 25%, while wind direction has shifted by 21 degrees towards the north. In order to assess if the variation in abundance was influenced by this change in the wind field, I first needed to correct for the other known long-term changes in lake's zooplankton. Hence, to consider how annual climatic differences might have influenced the community, I began by regressing zooplankton abundance against the presence/absence of Bythotrephes, the average number of days since spring ice break-up, and the average surface temperature on sampling days. I then determined if the residual variation in average zooplankton abundance from these models was correlated with the wind. Despite long-term changes in the wind field, linear-linear (speed) and linear-circular (direction) correlations of annual residual abundance of 7 of 2 the 8 species were not predictable from the wind fields using the averages of the sample day. The exception was D. mendotae, for which residual abundance was correlated with wind direction (r 2 =0.2300, p=0.005) meaning that the high residual abundance was correlated with a particular wind direction. D. mendotae is a large, fast swimming cladoceran that may be predictably responding under turbulent mixing and the resulting thermocline tilting in the hypolimnion. In summary, on an annual basis, long-term changes in zooplankton abundance were not improved by changes in the wind field.
The predictability of zooplankton abundance under wind-driven currents has been explored, but wha... more The predictability of zooplankton abundance under wind-driven currents has been explored, but what has not been explored is how the distributions change over the longterm in response to changes in wind fields. In this study, I sought relationships between the wind field and fortnightly abundances of 8 zooplankton species at a mid-lake station in Harp Lake, Ontario from 1980 to 2004. Over this time period, average wind speed has declined by 25%, which is consistent with the long-term trends over the Northern Hemisphere (Vautard et al. 2010), while direction has shifted 21 degrees towards the north. Multiple linear regressions were generated to predict seasonal and interannual changes in daily zooplankton abundance combining year, Julian day, chemistry and, finally, wind speed and direction. Wind field metrics were included in the models for 6 of the 8 species, although improvements in predictive power were modest. We suspect that the decrease in wind speed has contributed to a change in zooplankton heterogeneity in the lake, and thus a change in lake-wide abundance estimates derived from a single station. Zooplankton are patchily distributed, but most long-term monitoring programs sample only at one station. My work suggests that we may well be able to correct for some of the bias due to a changing wind field, and make small but significant improvements in the predictability of abundance of zooplankton species if we consider wind as a driver.
The errors associated with using daily data