Ecology of aquatic insects in monsoonal temperate glacier streams of Southeast Tibet: A departure from the conceptual model
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| Language: | English |
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The Ohio State University / OhioLINK
2017
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=osu1512032478760477 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu1512032478760477 |
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English |
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Environmental Science glacial meltwater glacier streams climate change aquatic ecology metakryal Plecoptera osmoregulation Southeast Tibet temperate monsoonal hydraulic microhabitats salinity conductivity lc50 chloride cells |
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Environmental Science glacial meltwater glacier streams climate change aquatic ecology metakryal Plecoptera osmoregulation Southeast Tibet temperate monsoonal hydraulic microhabitats salinity conductivity lc50 chloride cells Fair, Heather Lynne Ecology of aquatic insects in monsoonal temperate glacier streams of Southeast Tibet: A departure from the conceptual model |
| author |
Fair, Heather Lynne |
| author_facet |
Fair, Heather Lynne |
| author_sort |
Fair, Heather Lynne |
| title |
Ecology of aquatic insects in monsoonal temperate glacier streams of Southeast Tibet: A departure from the conceptual model |
| title_short |
Ecology of aquatic insects in monsoonal temperate glacier streams of Southeast Tibet: A departure from the conceptual model |
| title_full |
Ecology of aquatic insects in monsoonal temperate glacier streams of Southeast Tibet: A departure from the conceptual model |
| title_fullStr |
Ecology of aquatic insects in monsoonal temperate glacier streams of Southeast Tibet: A departure from the conceptual model |
| title_full_unstemmed |
Ecology of aquatic insects in monsoonal temperate glacier streams of Southeast Tibet: A departure from the conceptual model |
| title_sort |
ecology of aquatic insects in monsoonal temperate glacier streams of southeast tibet: a departure from the conceptual model |
| publisher |
The Ohio State University / OhioLINK |
| publishDate |
2017 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=osu1512032478760477 |
| work_keys_str_mv |
AT fairheatherlynne ecologyofaquaticinsectsinmonsoonaltemperateglacierstreamsofsoutheasttibetadeparturefromtheconceptualmodel |
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1719453154609725440 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu15120324787604772021-08-03T07:04:56Z Ecology of aquatic insects in monsoonal temperate glacier streams of Southeast Tibet: A departure from the conceptual model Fair, Heather Lynne Environmental Science glacial meltwater glacier streams climate change aquatic ecology metakryal Plecoptera osmoregulation Southeast Tibet temperate monsoonal hydraulic microhabitats salinity conductivity lc50 chloride cells <p> The cryosphere is shrinking as a result of climate change. Mountain glaciers, a key component of the cryosphere, serve as headwaters to glacier meltwater streams which support communities of stenothermic organisms. The Tibetan plateau is known as "the Third Pole" for its high number of glaciers, yet very few scientific papers have been published on aquatic invertebrate ecology of glacier-fed streams in the region. On the edges of the Tibetan Plateau in Southeast Tibet's Hengduan mountains, monsoonal temperate glaciers extend well below the treeline as valley glaciers, and are perhaps the most endangered cryosphere-dominated streams in the world due to their low latitudes and altitudes, which makes them sensitive to atmospheric temperature changes. The glaciated headwaters of the Mekong and Yangtze Rivers comprise a small fraction of the annual river discharge, yet at a local scale provide glacial meltwater that supports endemic and potentially rare species.</p> <p>Water temperature and channel stability differ between seasons due to the torrential flow from glacial meltwater during the summer melt season. The Milner & Petts (M&P) model of macroinvertebrate presence in glacier streams was based on the environmental factors of water temperature and channel stability during the summer melt season. In low temperature water close to the glacier, the macroinvertebrate communities are generally limited to Diamesinae chironomids, and further downstream more taxa are found where water temperature and channel stability increase. Therefore, temperature and channel stability are examined as potential limiting factors on the distribution of invertebrate communities, with the goal to compare the insect communities in Southeastern Tibet's glacier-fed streams with the widely-accepted M&P model of invertebrate community structure.</p> <p>Since discharge and hydrology may influence invertebrate distribution in glacier streams, hydraulic characteristics and invertebrate communities in six microhabitats (pool, riffle, run, step-run, rapid, and step-rapid) were examined over three seasons in the Mingyong Glacier stream. This is the first known study to examine hydraulics at the microhabitat level in glacier streams, and to compare microhabitats by season. Certain hydrologic characteristics have been found to trap and retain leaf litter at different rates, with backwater areas having the greatest trapping efficiency even in high discharge. Moreover, microhabitats with turbulent water entrain oxygen from the atmosphere which can lead to greater biomass growth. Microhabitats with larger substrate create hydrologic refugia for insects, and higher velocity microhabitats tend to have larger boulder substrate. Therefore it was hypothesized that in the Mingyong Glacier mainstem rapids and step-rapids with greater water velocities and velocity ranges would support greater aquatic insect species richness and abundance.</p> <p>In addition to hydraulics and environmental variables, the salinity tolerance of glacier stoneflies was examined to partially study the research question, "will metakryal zone insects from glacier streams adapt to groundwater stream salinity levels once the glaciers are gone"? Moreover, the morphological changes of their chloride cells following exposure to waters of differing salinity were quantified by using scanning electron microscopy images. The survivorship of stoneflies from upstream glacial meltwater sites was compared with stoneflies from downstream glacial meltwater sites to salinity treatments.</p> <p>The ecological result of this research is a clear departure from the accepted M&P glacier stream model where temperature and channel stability are suggested to determine aquatic invertebrate presence in glacier streams. Temperature and channel stability did not exhibit a relationship with species presence, richness, or abundance in Southeast Tibet’s temperate glacier streams during the summer melt season. There were fourteen taxa in addition to Diamesinae in the metakryal zones where the T<sub>max</sub> temperature remains <2<sup>o</sup>C all year. This is contrary to almost all other studies of glacier streams. The results suggest that other factors such as the mass elevation effect (MEE) of the mountain range, glacier and stream size, winter water temperatures, elevational position of the glacier, ice/snow coverage, and position of the glacier tongue beneath the treeline could be as important in these systems as water temperature and channel stability. In addition, the fact that water is perennially flowing from beneath the glaciers could be a result of the position of the snout beneath the mountain range’s atmospheric zero degree isotherm which results in the monsoonal temperate glaciers falling in the categories of warm-based/wet-based glaciers. The fact that the stream does not freeze could be a major reason for the departure from the model, as many of the streams that were in agreement with the model were located at higher latitudes and in alpine zones (above the treeline) therefore more likely to be above the respective mountain range atmospheric zero degree isotherm where the glacier beds and streams are more likely to freeze during the winter. However, very little is published regarding the conditions of glacier metakryal zones during the winter season.</p> <p>The results of the study on hydraulic characteristics suggest that rapids, as microhabitats with the highest water velocities and water velocity ranges, trap and retain more organic carbon than pools and riffles, with runs also containing significantly greater organic carbon than riffles. Overall taxa abundance was greatest in runs, which were significantly greater than riffles and pools. This suggests that in glacier-fed streams, the higher velocity microhabitats may be important habitats to examine invertebrate ecology in order to attain representative abundance of taxa in streams.</p> <p>Chloroperlidae were located furthest from the glacier source, and survived for the longest time in the higher salinity experimental treatments (0.95% and 1.2% NaCl). However, the lethal toxicity of salinity (LC<sub>50</sub>) to Taeniopterygidae, Nemouridae, and Chloroperlidae were not different, suggesting that naturally-occurring salinities in these mountain stream waters may be in a range tolerable to metakryal stoneflies. Changes in morphology of chloride and caviform cells on Chloroperlidae and caviform cells on Taeniopterygidae occurred as predicted in an inverse manner with salinity. This is the first study that has observed a morphological response from caviform cells, connecting them with an osmoregulatory function.</p> <p>The results of this research indicate a major departure from the established M&P model of glacier macroinvertebrate community structure. The results suggest that a modified model may be appropriate for glacier-fed streams in the monsoonal temperate region where glacier tongues extend far beneath the extremely high treeline in v-shaped valleys at relatively low altitudes. One reason for the departure may be the perennial nature of the streams under temperate wet-based glaciers which have water present throughout the ice mass. Therefore it would be appropriate to examine winter metakryal conditions in glacier-fed streams in agreement with the M&P model to understand if the streams are intermittent, impacted by surface ice, or freeze solid. Hydraulic and substrate characteristics in this study have an influence on the presence of carbon and invertebrate abundance. Habitats with higher water velocity and potential hidden backwaters support a greater abundance of certain taxa. Hydraulic characteristics and ice presence during the winter could be the two of the major reasons for the difference between the M&P model and this study, so it is suggested that year round hydraulic characteristics be examined in other glacier streams.</p> 2017 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1512032478760477 http://rave.ohiolink.edu/etdc/view?acc_num=osu1512032478760477 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |