Climate change and rising sea levels are endangering coastal
wetlands, which are well known to be essential to prevent coastline
erosion and as nutrient buffers for benthic environments. As sea levels
rise and salt marsh plants experience longer periods of inundation
certain physiological mechanisms are necessary for plants to adapt to
changing conditions. One such mechanism is the formation of aerenchyma,
air spaces in the stems, roots, and rhizomes of wetland plants which
allow for aerobic respiration during periods of inundation. Estuarine
plants are experiencing increasingly high nutrient loads from riverine
washout, particularly from nitrates due to fertilizer pollution. While
the negative impact of nitrates on offshore benthic environments has
been well documented, the impact of poor water quality on salt marshes
has been inconclusive. Low nutrient availability has been shown to
encourage the formation of aerenchyma in food plants such as rice and
corn. If this is also the case for coastal marsh plants, poor water
quality may prevent an important physiological process that can help
these plants adapt to a changing climate. This study aims to
examine the potential negative impact of high nutrient loads on the
physiology of coastal marsh plants. Specifically, we focused on the
formation of aerenchyma in the high marsh cordgrass species Spartina
patens and its relationship to nutrient availability. We investigated
this process using a controlled factorial experiment, in which we grew
Spartina patens in a mesocosm to simulate tides, and subjected one group
of plants to low nutrient conditions and one group to high nutrient
conditions. We then compared the formation of aerenchyma in the roots of
both groups using scanning electron microscopy. If aerenchyma formation
is correlated to nutrient availability, this could clarify one variable
leading to inconsistent results in previous studies on the effect of
nutrient availability on salt marshes.
