Abstract

Change in the coastal zone is accelerating with external forcing by sea-level rise, nutrient loading, drought and over-harvest is impacting salt marshes. Understanding marsh resilience, including recovery from coastal storms and detection of stress, is essential for conservation and prediction of ecosystem services. The ‘chronosequence approach’ of predicting future state change by examining ecosystem structure and function in existing ecosystems of different ages is a powerful tool, but assumes that the past mimics the future, and time is the dominant driver of change. This approach was evaluated by replicating a 1995 salt marsh chronosequence study in back-barrier marshes ranging from 4 to >170 yr old on Hog Island, Virginia. Physico-chemical properties, such as porewater redox potential and sediment organic matter and nutrients, followed predictable age-related patterns. However, invertebrate abundance, plant biomass, and sediment grain size instead seemed to respond to sea level rise and stochastic die-off and sand deposition. Thus, while time drives the intrinsic evolution of some physico-chemical components, extrinsic drivers exert a strong influence on key biotic-abiotic feedbacks. Exacerbation of external forcing may push the trajectory of marsh succession away from a predictable trajectory, limiting ecosystem services. This rapid evolution of marsh state makes the ability to detect stressors prior to marsh collapse important. Hyperspectral imagery of plants was collected in marshes of varying age/stressor characteristics, including salinity, sediment redox potential and nitrogen availability, and in the greenhouse, where environmental conditions were manipulated. Models developed to stressors based on plant spectral response were useful for salinity and nitrogen within the greenhouse or within the field, but were not transferable from lab to field. This study is an important step towards development of a remote sensing tool for tracking of ecosystem development, marsh health, and future ecosystem services.

Library of Congress Subject Headings

Salt marshes--Imaging; Salt marsh ecology; Hyperspectral imaging

Publication Date

6-3-2019

Document Type

Thesis

Student Type

Graduate

Degree Name

Environmental Science (MS)

Department, Program, or Center

Thomas H. Gosnell School of Life Sciences (COS)

Advisor

Anna Christina Tyler

Advisor/Committee Member

Charles Bachmann

Advisor/Committee Member

David Osgood

Campus

RIT – Main Campus

Plan Codes

ENVS-MS

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