Effect of mangrove change on the crab assemblages at Tamsui estuary in Taiwan
Date Issued
2015
Date
2015
Author(s)
Lu, Chih-Ying
Abstract
Tamsui estuary includes Wazihwei, Chuwei (Tamsui River Mangrove) and Guandu Nature Reserves are tidal mudflat ecosystem. With so many creatures living inside of it, Tamsui estuary is one of the most valuable ecological resources of Taiwan. Crab plays an important role in mudflat ecosystem, such as facilitating the nutrient transfer in a food web. Species distribution changes may affect the assemblage structure, which could be an indicator of habitat status. Therefore the information on how the crab assemblage changes could be useful in mudflat management. Crab species distribution on the tidal mudflat is affected by many environmental factors, such as sediment parameters and mangrove coverage. In Taiwan, mangrove species, Kandelia obovate, has introduced to Tamsui more than ninety years and has become the dominant plant species in this area. Recent research shows that it is still expanding. This study repeats the method done by Kuo (2001), and assesses how the crab species distribution and density changes between 2001 and 2014 in Wazihwei, Chuwei (Tamsui River Mangrove) and Guandu Nature Reserves. The goal is to understand how the mangrove change affects crab distribution, and the difference between mangrove and open mudflat. This study also analyzes the information collected to see if there is a linear correlation between crab density and salinity. The result of nine transects survey shows that mangrove coverage expanded in four transects and reduced in the others five transects. At mangrove expanding transects, mangrove crab distribution area increases, while open mudflat crab distribution area reduces. At mangrove reducing transects, mangrove crab distribution area reduces. However, the result of open mudflat crab species are different between transects. It needs to be explained by the sediment parameter change. Mangrove expansion adjacent mudflat has lower crab diversity than mangrove reduction adjacent mudflat. There is no significant linear correlation between crab density and salinity. This research shows that mangrove expansion may have a negative effect on the open mudflat crab. It reflects in the decreases of distribution area and diversity. Open mudflat crab change at mangrove reduction area needs to be explained by the sediment parameter. It may indicate that after mangrove reduction, sediment changes are the main factor that affects crab distribution area. Recently, due to global climate change, mangrove may have the access to expand to higher latitude area. Planting mangrove is popularizing in Taiwan, but planting mangrove without appropriate consideration always lead to mangrove removal due to expansion control. This research provides an example of how the dynamics of mangrove coverage affect crab assemblages on tidal mudflats.
Subjects
Population distribution
Mangrove
Crab assemblages
Estuary mudflat
SDGs
Type
thesis
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