The role of upwelling in determining the composition, species distribution and genetic structure of intertidal communities in a time of climate change
- Lourenço, Carla Sofia Emídio Rodrigues
- Authors: Lourenço, Carla Sofia Emídio Rodrigues
- Date: 2018
- Subjects: Upwelling (Oceanography) , Intertidal organisms -- Morocco -- Atlantic Coast , Intertidal organisms -- Canary Current -- Effect of water currents on , Intertidal animals -- Canary Current -- Effect of water currents on , Intertidal animals -- Morocco -- Atlantic Coas , Mytilus galloprovincialis -- Morocco -- Atlantic Coast , Mytilus galloprovincialis -- Canary Current -- Effect of water currents on , Intertidal ecology -- Canary Current , Sea surface microlayer -- Morocco -- Atlantic Coast
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61614 , vital:28042
- Description: Upwelling is an oceanographic process that strongly influences coastal species and the communities they belong to. In upwelling areas, colder, denser, nutrient-rich subsurface waters are transported to the nearshore surface, replacing warmer superficial waters that are advected offshore. Such effects influence the composition and dynamics of coastal communities, for example by affecting species abundance, recruitment, dispersal and distribution. Upwelling areas are key model regions to study the responses of coastal species to climate change because they are characterized by cooler conditions and experience lower warming rates than adjacent regions. In particular, intertidal rocky shore species are ideal coastal sentinel organisms to study distributional changes driven by climate warming because they inhabit the interface between marine and terrestrial habitats and are exposed to extremely severe environmental conditions. In fact, sharp distributional shifts have been reported for multiple intertidal species as a response to ocean warming. Although some studies have investigated the role of upwelling in influencing abundance and distribution of intertidal species, little is known about its potential as refugia against climate warming and the degree to which upwelling shapes species genetic structure is yet not fully understood. The aim of this thesis is to understand the influence of the Canary Current upwelling system on intertidal community composition, including species distribution and the genetic structure of intertidal species under current climate change. To do this, I investigated community structure of intertidal assemblages along the Atlantic shores of Morocco and Western Sahara, performed large scale surveys on species distribution, evaluated species abundance and frequency of parasitism and examined species genetic patterns. I further coupled biological data with upwelling indices, sea surface temperatures (SST) and the rate of SST warming. I demonstrate that strong upwelling influences abundance and distribution of intertidal rocky shore species and that upwelling cells can act as refugia from climate change by ameliorating thermal conditions. Upwelling cells also conserve the genetic diversity of the marine macroalga Fucus guiryi, promoting intraspecific genetic diversity by preserving unique genetic lineages. However, no evidence was found that upwelling affects the genetic structure for either F. guiryi or the brown mussel Perna perna. Instead, the genetic patterns presented in this thesis seem to result from a combination of species’ life history traits, population size and habitat suitability. My results also suggest that upwelling intensity affects the frequency of endolithic parasitism on the Mediterranean mussel Mytilus galloprovincialis. In times of climate change, upwelling events provide suitable environmental conditions for species to counter act climatic change. As upwelling is project to intensify in the future, its influence on benthic intertidal species might be greater than previously anticipated.
- Full Text:
- Date Issued: 2018
- Authors: Lourenço, Carla Sofia Emídio Rodrigues
- Date: 2018
- Subjects: Upwelling (Oceanography) , Intertidal organisms -- Morocco -- Atlantic Coast , Intertidal organisms -- Canary Current -- Effect of water currents on , Intertidal animals -- Canary Current -- Effect of water currents on , Intertidal animals -- Morocco -- Atlantic Coas , Mytilus galloprovincialis -- Morocco -- Atlantic Coast , Mytilus galloprovincialis -- Canary Current -- Effect of water currents on , Intertidal ecology -- Canary Current , Sea surface microlayer -- Morocco -- Atlantic Coast
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61614 , vital:28042
- Description: Upwelling is an oceanographic process that strongly influences coastal species and the communities they belong to. In upwelling areas, colder, denser, nutrient-rich subsurface waters are transported to the nearshore surface, replacing warmer superficial waters that are advected offshore. Such effects influence the composition and dynamics of coastal communities, for example by affecting species abundance, recruitment, dispersal and distribution. Upwelling areas are key model regions to study the responses of coastal species to climate change because they are characterized by cooler conditions and experience lower warming rates than adjacent regions. In particular, intertidal rocky shore species are ideal coastal sentinel organisms to study distributional changes driven by climate warming because they inhabit the interface between marine and terrestrial habitats and are exposed to extremely severe environmental conditions. In fact, sharp distributional shifts have been reported for multiple intertidal species as a response to ocean warming. Although some studies have investigated the role of upwelling in influencing abundance and distribution of intertidal species, little is known about its potential as refugia against climate warming and the degree to which upwelling shapes species genetic structure is yet not fully understood. The aim of this thesis is to understand the influence of the Canary Current upwelling system on intertidal community composition, including species distribution and the genetic structure of intertidal species under current climate change. To do this, I investigated community structure of intertidal assemblages along the Atlantic shores of Morocco and Western Sahara, performed large scale surveys on species distribution, evaluated species abundance and frequency of parasitism and examined species genetic patterns. I further coupled biological data with upwelling indices, sea surface temperatures (SST) and the rate of SST warming. I demonstrate that strong upwelling influences abundance and distribution of intertidal rocky shore species and that upwelling cells can act as refugia from climate change by ameliorating thermal conditions. Upwelling cells also conserve the genetic diversity of the marine macroalga Fucus guiryi, promoting intraspecific genetic diversity by preserving unique genetic lineages. However, no evidence was found that upwelling affects the genetic structure for either F. guiryi or the brown mussel Perna perna. Instead, the genetic patterns presented in this thesis seem to result from a combination of species’ life history traits, population size and habitat suitability. My results also suggest that upwelling intensity affects the frequency of endolithic parasitism on the Mediterranean mussel Mytilus galloprovincialis. In times of climate change, upwelling events provide suitable environmental conditions for species to counter act climatic change. As upwelling is project to intensify in the future, its influence on benthic intertidal species might be greater than previously anticipated.
- Full Text:
- Date Issued: 2018
Uphando-nzulu lweempendulo ezibhaliweyo zabafundi bamabakala aphezulu emfundo kuncwadi lwesiXhosa
- Authors: Mavela, Xolani Sikhomo
- Date: 2018
- Subjects: Discourse analysis , Anthropological linguistics , Academic writing Study and teaching , Academic writing Evaluation , Linguistics Research
- Language: Xhosa
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63176 , vital:28370
- Description: Kwiziphumo zakutsha nje ezivezwe kwiigridi zocazululo zohlolo loncwadi kwinqanaba lemfundo ephakamileyo (FET), kufumaniseke ukuba abafundi beli nqanaba abaqhubi kakuhle tu kwaphela xa becelwa ukuba babhale iimpendulo zabo kwanezo zimandundu nezikhwencayo kwiitekisi zoncwadi. Ngenxa yesi sizathu, eyona njongo iphambili yolu phando kukuzama ukuyila nokuvelisa isixhobo esinokusetyenziswa ekwaziseni nasekuxhobiseni abafundi besiXhosa abakwinqanaba leFET, ngezakhono zokubhala eziphuhlileyo nezikumgangatho wobhalo lwamaziko emfundo enomsila. Kule meko, ingcali yophando kwezobhalo lolwimi uMartin (2009) uhlomla ngelithi ubhalo olujolise ekunikeni iimpendulo, lubonwa njengohlobo lokubhala oluneengcambu ezimiliselwe ekufundisweni nasekungeneleleni ngokugqibeleleyo ngezakhono zokubhala, bhalo olu lunokuthi emva kwethuba elithile, luphelele kwincochoyi yokushicilelwa, lube ngamaxwebhu ahlelwe ngokusesikweni. Iindlela okanye izixhobo zokubhala eziyilwe ngeenjongo zokunikeza iimpendulo, nezithathwe kuphando lukaFeez noJoyce (1998), zizo eziza kusetyenziswa njengenxalenye yoqeqesho nakumaphulo ongenelelo oluza kuxhasa abafundi besiXhosa benqanaba leFET, nanjengoko ezi zixhobo zibonakala zinegalelo elincomekayo kwindlela ekubhalwa ngayo iimpendulo zeetekisi zoncwadi, ngokuthi zigxile kwezi njongo zilandelayo: (i) Ukunika abafundi ulwazi lokuzuza ulwazi olunzulu nolugqibeleleyo ngokuphathelele kwiinjongo zetekisi. (ii) Ukunika inkcazelo ecacileyo ngokubaluleka kwesakhiwo setekisi kwanokubunjwa kwayo. (iii) Ukuxhobisa abafundi ukuze bakwazi ukuchonga ulwimi oluxabisayo, iimpawu zobume bamagama negrama, kuquka nemiba ephambili yamasiko kwiitekisi zoncwadi. Ngenxa yezi njongo, kufikelelwa kuqikelelo oluthi, kuya kuthi ngokusetyenziswa kwesixhobo sikaFeez noJoyce seZakhono zokuBhala, sixhobo eso sayame kwiinqobo zeNgcingane yokuXabisa okufundwayo nedandalaziswa nguMartin noWhite (2006; 2005 no-2003) nayo le ngcingane eluncedo ekufundisweni kokubhala, abafundi abaninzi boncwadi lwesiXhosa kukholeleka ukuba bakukwazi ukuphuhlisa izakhono zokubhala iitekisi ezinika iimpendulo ezihlahlela imiba ephambili yoncwadi abalufundisiweyo. Olu phando lukwahlabela mgama lubonisa nokuba nezinye izixhobo zoyilo lweetekisi zikaGrabe noKaplan (1996), zinakho ukusetyenziswa ngaxesha linye neenqobo zeNgcingane yokuXabisa okufundwayo, kuquka nemiba yeZakhono zokuBhala, ukuze kwandiswe oku kuphuhliswa kwezakhono zokubhala kubafundi besiXhosa, kungaphelelanga kumabanga aphezulu, koko kufikelelwe nakumabanga asezantsi, nanjengoko kuveziwe kwiziphumo, kwizishwankathelo nakwisiphelo solu phando.
- Full Text:
- Date Issued: 2018
- Authors: Mavela, Xolani Sikhomo
- Date: 2018
- Subjects: Discourse analysis , Anthropological linguistics , Academic writing Study and teaching , Academic writing Evaluation , Linguistics Research
- Language: Xhosa
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63176 , vital:28370
- Description: Kwiziphumo zakutsha nje ezivezwe kwiigridi zocazululo zohlolo loncwadi kwinqanaba lemfundo ephakamileyo (FET), kufumaniseke ukuba abafundi beli nqanaba abaqhubi kakuhle tu kwaphela xa becelwa ukuba babhale iimpendulo zabo kwanezo zimandundu nezikhwencayo kwiitekisi zoncwadi. Ngenxa yesi sizathu, eyona njongo iphambili yolu phando kukuzama ukuyila nokuvelisa isixhobo esinokusetyenziswa ekwaziseni nasekuxhobiseni abafundi besiXhosa abakwinqanaba leFET, ngezakhono zokubhala eziphuhlileyo nezikumgangatho wobhalo lwamaziko emfundo enomsila. Kule meko, ingcali yophando kwezobhalo lolwimi uMartin (2009) uhlomla ngelithi ubhalo olujolise ekunikeni iimpendulo, lubonwa njengohlobo lokubhala oluneengcambu ezimiliselwe ekufundisweni nasekungeneleleni ngokugqibeleleyo ngezakhono zokubhala, bhalo olu lunokuthi emva kwethuba elithile, luphelele kwincochoyi yokushicilelwa, lube ngamaxwebhu ahlelwe ngokusesikweni. Iindlela okanye izixhobo zokubhala eziyilwe ngeenjongo zokunikeza iimpendulo, nezithathwe kuphando lukaFeez noJoyce (1998), zizo eziza kusetyenziswa njengenxalenye yoqeqesho nakumaphulo ongenelelo oluza kuxhasa abafundi besiXhosa benqanaba leFET, nanjengoko ezi zixhobo zibonakala zinegalelo elincomekayo kwindlela ekubhalwa ngayo iimpendulo zeetekisi zoncwadi, ngokuthi zigxile kwezi njongo zilandelayo: (i) Ukunika abafundi ulwazi lokuzuza ulwazi olunzulu nolugqibeleleyo ngokuphathelele kwiinjongo zetekisi. (ii) Ukunika inkcazelo ecacileyo ngokubaluleka kwesakhiwo setekisi kwanokubunjwa kwayo. (iii) Ukuxhobisa abafundi ukuze bakwazi ukuchonga ulwimi oluxabisayo, iimpawu zobume bamagama negrama, kuquka nemiba ephambili yamasiko kwiitekisi zoncwadi. Ngenxa yezi njongo, kufikelelwa kuqikelelo oluthi, kuya kuthi ngokusetyenziswa kwesixhobo sikaFeez noJoyce seZakhono zokuBhala, sixhobo eso sayame kwiinqobo zeNgcingane yokuXabisa okufundwayo nedandalaziswa nguMartin noWhite (2006; 2005 no-2003) nayo le ngcingane eluncedo ekufundisweni kokubhala, abafundi abaninzi boncwadi lwesiXhosa kukholeleka ukuba bakukwazi ukuphuhlisa izakhono zokubhala iitekisi ezinika iimpendulo ezihlahlela imiba ephambili yoncwadi abalufundisiweyo. Olu phando lukwahlabela mgama lubonisa nokuba nezinye izixhobo zoyilo lweetekisi zikaGrabe noKaplan (1996), zinakho ukusetyenziswa ngaxesha linye neenqobo zeNgcingane yokuXabisa okufundwayo, kuquka nemiba yeZakhono zokuBhala, ukuze kwandiswe oku kuphuhliswa kwezakhono zokubhala kubafundi besiXhosa, kungaphelelanga kumabanga aphezulu, koko kufikelelwe nakumabanga asezantsi, nanjengoko kuveziwe kwiziphumo, kwizishwankathelo nakwisiphelo solu phando.
- Full Text:
- Date Issued: 2018
Identifying growth criteria and sediment movement mechanisms of needle ice using high-frequency environmental and visual monitoring
- Authors: Borg, Carl-Johan
- Date: 2017
- Subjects: Frazil ice , Sediment transport , Ice mechanics , Photography -- Digital techniques , Environmental monitoring
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/17656 , vital:22268
- Description: Environmental growth conditions and mechanisms involved in sediment transport by needle ice have historically been difficult to assess and are poorly documented. The spatial and temporal dynamics that relate to the environment, growth and decay of needle ice are not fully understood. This study monitored needle ice growth, melt and visually identified sediment displacement mechanisms by needle ice, with the aim of revealing environmental growth criteria, timing of growth/melt, ground-surface-air energy balance and sediment displacement mechanisms. Furthermore, the impact of needle ice displacement on vegetation and patterned ground formation was analysed. High-frequency visual monitoring, using three cameras, supplemented by high-frequency measurements of air temperature, soil moisture and wind speed was used to investigate needle ice growth and decay dynamics. Results from visual and environmental monitoring of needle ice growth, showed that the needle ice growing environment was more dynamic, especially in terms of surface temperature, than previously argued. Needle ice growth was observed to occur during surface temperatures from -2.0°C to 2.2°C, soil moisture levels from 0.4% to 37.4% and in winds speeds of 0 m/s to 12.6 m/s. Needle ice initiation was documented a few minutes to hours before or after the onset of surface temperature dropping to below 0°C. Imagery displayed that the depth of ice nucleation was variable within the soil column, possibly relating to the energy balance of radiative cooling, convective heat loss, ground conductivity and latent heat release at the air-surface-ground boundary. Heaving and resettling, toppling and rolling were identified as slope displacement mechanisms when needle ice decayed. Animal trampling and hail were additionally documented as substantial surface altering processes. Furthermore, no impact of needle ice reducing vegetation stability was identified, although a tendency to hinder vegetation expansion was noted. Also, no creation of patterned ground was observed as a result of needle ice decay.
- Full Text:
- Date Issued: 2017
- Authors: Borg, Carl-Johan
- Date: 2017
- Subjects: Frazil ice , Sediment transport , Ice mechanics , Photography -- Digital techniques , Environmental monitoring
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/17656 , vital:22268
- Description: Environmental growth conditions and mechanisms involved in sediment transport by needle ice have historically been difficult to assess and are poorly documented. The spatial and temporal dynamics that relate to the environment, growth and decay of needle ice are not fully understood. This study monitored needle ice growth, melt and visually identified sediment displacement mechanisms by needle ice, with the aim of revealing environmental growth criteria, timing of growth/melt, ground-surface-air energy balance and sediment displacement mechanisms. Furthermore, the impact of needle ice displacement on vegetation and patterned ground formation was analysed. High-frequency visual monitoring, using three cameras, supplemented by high-frequency measurements of air temperature, soil moisture and wind speed was used to investigate needle ice growth and decay dynamics. Results from visual and environmental monitoring of needle ice growth, showed that the needle ice growing environment was more dynamic, especially in terms of surface temperature, than previously argued. Needle ice growth was observed to occur during surface temperatures from -2.0°C to 2.2°C, soil moisture levels from 0.4% to 37.4% and in winds speeds of 0 m/s to 12.6 m/s. Needle ice initiation was documented a few minutes to hours before or after the onset of surface temperature dropping to below 0°C. Imagery displayed that the depth of ice nucleation was variable within the soil column, possibly relating to the energy balance of radiative cooling, convective heat loss, ground conductivity and latent heat release at the air-surface-ground boundary. Heaving and resettling, toppling and rolling were identified as slope displacement mechanisms when needle ice decayed. Animal trampling and hail were additionally documented as substantial surface altering processes. Furthermore, no impact of needle ice reducing vegetation stability was identified, although a tendency to hinder vegetation expansion was noted. Also, no creation of patterned ground was observed as a result of needle ice decay.
- Full Text:
- Date Issued: 2017
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