A hurricane alters the relationship between mangrove cover and marine subsidies in Texas, USA: 2014-2019

We experimentally manipulated black mangrove (Avicennia germinans)
cover in ten large plots and over five years (2014-2019) quantified
the effects of mangrove cover on subsidies of floating organic
material (wrack) into coastal wetlands. We hypothesized that the
change from salt marsh to mangrove vegetation would alter the
permeability of the intertidal habitat, and thus alter the nature of
subsidies from marine to intertidal habitats. Data from field
surveys of wrack distribution showed that as mangrove cover
increased from zero to 100%, wrack cover and thickness decreased by
~60%, the distance that wrack penetrated into the plots decreased by
~70%, and the percentage of the wrack trapped in the first six m of
the plot tripled. Data from wrack samples indicated that wrack
samples collected from the fringe were ~3 times heavier than those
from the interior of plots. Animals were ~40% more abundant in
samples from the interior than from the fringe of plots, but this
trend was not statistically significant due to low replication of
interior samples. Data from a wrack experiment revealed that animal
abundance and species composition varied between the fringe and
interior of the plots, and between microhabitats dominated by salt
marsh versus mangrove vegetation. Increasing mangrove cover
decreased the relative importance of marine subsidies into the
intertidal at the plot level, but concentrated subsidies at the
front edge of the mangrove stand. Storms, however, may temporarily
override mangrove attenuation of wrack inputs.