Tropical Coastal Ecosystems: the effects of long- and short-term changes in groundwater flow on seagrass distributions in Florida and Kenya
Dahdouh-Guebas, F. (1996). Tropical Coastal Ecosystems: the effects of long- and short-term changes in groundwater flow on seagrass distributions in Florida and Kenya. MSc Thesis. VUB: Brussel. 86 pp.
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Document type: Dissertation
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| Keywords |
Angiosperms > Monocotyledons > Hydrocharitales > Hydrocharitaceae > Halophila > Halophila ovalis
Mangroves
Remote sensing
Satellite imagery
Seagrass
Halodule uninervis (Forsskål) Ascherson, 1882 [WoRMS]; Halodule wrightii Ascherson, 1868 [WoRMS]; Halophila minor (Zollinger) Hartog, 1957 [WoRMS]; Halophila ovata Gaudichaud, 1827 [WoRMS]; Halophila stipulacea (Forsskål) Ascherson, 1867 [WoRMS]; Syringodium isoetifolium (Ascherson) Dandy, 1939 [WoRMS]; Thalassia hemprichii (Ehrenberg) Ascherson, 1871 [WoRMS]
ISW, Kenya, Coast, Diani; ISW, Kenya, Gazi Bay [Marine Regions]
Marine/Coastal; Brackish water |
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| Abstract |
In many tropical and subtropical regions coastal areas consist of mangroves, seagrasses and coral reefs. The presence and development of mangroves have been found to be dependent on freshwater and if no clear overland supply is present mangroves rely on groundwater outflow. Therefore extensive groundwater pumping adversely affects mangrove forests. Florida and Kenya have been the subject of many studies related to this problem. Also seagrass distributions have been investigeted a lot in Florida but hardly any studies have been performed on them in Kenya. The objective of this study was firstly to investigate how seagrasses are distributed in Kenya, and secondly to examine in Kenya and in Florida if the trend of seagrass distributions with respect to coastal groundwater outflow is the same as for mangrove forests. The main bulk of this thesis consists of the visualisation of seagrass distributions through remote sensing. A TM satellite image covering the Kenyan coast from Mombasa down to Funzi Bay was manipulated in order to map the seagrasses. In a second phase groundwater outflow vectors were fit into the distribution maps of both Floridan and Kenyan seagrasses. The results of a comparison between groundwater outflow and seagrass distributions show that in Florida seagrass die-off occurred on the places where groundwater outflow has drastically decreased ever since the beginning of this century. However, the results for Kenya suggest that no real trend exists in the seagrass distributions. Apparently they do not show the same distribution trend as mangroves in terms of groundwater outflow. Possibly the two regions investigated are not comparable because of the different hydrological history. |
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