Pier Shading Effects

Introduction

As a result of on-going shoreline development and recreational use along Mississippi’s coastal wetlands, valuable marshland is being impacted as attempts are made to access open water from land. Numerous man-made piers that extend across tidal marshes from small residential properties, although designed for minimum stress on marsh habitats, may still have a considerable cumulative effect on overall salt marsh productivity by blocking light from reaching marsh grass beneath them. Shading caused by physical aspects of piers, including width, height above the grass, degree of separation between boards, and orientation with respect to angle of the sun, may contribute to diminishing the productivity of affected marsh grass. The purpose of this project will be to evaluate and quantify these aspects of pier construction on marsh productivity by (1) evaluating the effects and extent of existing pier constructions, and (2) conducting demonstrative field studies using pre-existing pier constructions to evaluate effects on salt marsh plant biomass. This project will document shading effects caused by man-made piers that overlie salt marshes in coastal wetlands, one of Mississippi’s most valuable resources. Data generated from this study will aid in management decisions on the implementation of waterfront construction that impacts marine wetland areas or go toward the improvement of waterfront construction design.

The objective of this Tidelands grant (FY2005-M206-3) was to provide DMR Coastal Ecology branch with data on the effects of piers on salt marsh vegetation. We evaluated and quantified aspects of pier design that may negatively affect marsh plant productivity.

1. Review literature on the effects of man-made structures (i.e. piers) on coastal marshes.

2. Establish experimental pier structures to characterize shading impacts (Fig 1)

3. Develop experimental design for productivity measurements of Spartina and Juncus along a shading gradient (Fig 2)

4. Conduct productivity measurements using control and affected areas involving one or more of the following parameters: (1) light intensity, (2) stem height, (3) plant density, (4) plant above-ground biomass

5. Assess impacts comparing shading by piers in marshes with experiment pier units (Fig 3)

6. Produce a written report on project activities and conclusions

A research project of the Center for Plant Restoration and Coastal Plant Research - https://sites.google.com/site/coastalplantrestoration/

Prior relevant literature includes:

Kelty, R.A. and S. Bliven. 2003. Environmental and Aesthetic Impacts of Small Docks and Piers, Workshop Report: Developing a Science-Based Decision Support Tool for Small Dock Management, Phase 1: Status of the Science. NOAA Coastal Ocean Program Decision Analysis Series No. 22. National Centers for Coastal Ocean Science, Silver Spring, MD. 69 pp.

Shafer, D. J., 1999. Design and Construction of Docks to Minimize Seagrass Impacts. WRAP Technical Notes Collection. WRP Technical Note VN-RS-3.1. Vicksburg, MS: U.S. Army Engineer Research and Development Center.