Universiteit Leiden

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Biophysical feedbacks between seagrasses and hydrodynamics in relation to grazing, water quality and spatial heterogeneity

Consequences for sediment stability and seston trapping

A. Adhitya
07 december 2016
Thesis in Leiden Repository

My study focused on 1) fragmented seagrass interaction with hydrodynamics and 2) fragmented seagrass interaction with nutrients. My main research questions are: i) How do heterogeneous patches in the seagrass bed interact with the hydrodynamic force? ii) How do the different seagrass properties (density, leaf length) and gap sizes influence flow development inside the gap? iii) How is the advective porewater exchange influenced by the presence of seagrass? and iv) How do the different hydrodynamic factors (diffusion, flow, wave and flow induced by wave) influence porewater exchange from sediment to water column? The results of these studies show that in controlled environments which exclude the effects of factors other than the hydrodynamic conditions, seagrass meadows have the ability to restore and re-homogenize themselves. A wide range of other factors may also play a role in determining whether heterogeneous patches become more or less homogeneous, such as nutrient cycling from sediment into the water column or vice versa, deposition of organic matter, erosion by waves or tidal currents, or animal grazing. This PhD thesis presents findings that elucidate the fundamental processes of seagrass–hydrodynamics interactions, which impact ecological processes such as patch and gap dynamics and advective porewater exchange.