Effects of Umba River Sedimentation on the Distribution and Root Morphology of Mangroves of Vanga, Kenya
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Date
2022
Authors
Cherono, Kuloba Shawlet
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
The study examined the influence of Umba River, a trans-boundary resource draining
approximately 16 million m3 of freshwater into the Indian Ocean, on the distribution
and root morphology of mangrove of Vanga. Mangroves of Vanga, situated a few
kilometers from the border that transverse the Kenya-Tanzania border, south coast of
Kenya, harbor countless marine and coastal biodiversity and contributes to the
socioeconomics wellbeing of the adjacent communities. This ecological survey aimed
at understanding the influence of the river on sediment surface elevation change,
physicochemical parameters, and the resultant effect on mangrove distribution and root
morphology. Sixty-three plots were sampled along twenty-two belt transects laid
perpendicular to the river within three forest blocks (A, B and C) representing landward,
midstream and seaward sites respectively. Highest mangrove stem density (3268±325
stem/ha) was recorded seaward at relatively lower burial levels (2.69±0.49 cm) and
relatively high salinity (30.09±13.85). Nutrient concentration was relatively low across
all study blocks but mainly dominated by ammonia (70%), signifying hypoxia in
sediment. Among the three blocks, Avicennia marina recorded the largest number
(242±45/m2) and longest (>15 cm) pneumatophores in the landward block. The
difference in the height of Rhizophora mucronata prop roots was however not
significant within the blocks. These findings suggest that sediment elevation change
had the most influence on mangrove. Increase in sediment deposition influenced
mangrove distribution, species zonation and root morphology, with high stem density
being recorded at lower burial levels and species demonstrating a specific range of
tolerance to related environmental variables. In addition, mangrove complex root
system, depending on species, may adjust to cope with the increasing sedimentation. It
is therefore important to use these findings to inform the development and management
of the proposed Kenya-Tanzania Transboundary Conservation Area (TBCA).
Description
A Thesis Submitted in Partial Fulfilment of the Requirements for the Award of the Degree of Master of Science (Aquatic Ecology) in the School of Pure and Applied Sciences of Kenyatta University, June, 2022
Keywords
Effects, Umba River Sedimentation, Distribution, Root Morphology, Mangroves, Vanga, Kenya