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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2008-5139

Development of a Monitoring Protocol to Detect Ecological Change in the Intertidal Zone of Sitka National Historical Park, Alaska

Prepared in cooperation with the
National Park Service Southeast Alaska Coastal Cluster Program and Sitka National Historical Park

By Gail V. Irvine and Erica N. Madison

Abstract

A pilot study to develop and test a probability-based intertidal monitoring protocol for Sitka National Historical Park was conducted from 1999 to 2003. In 1999, the basic design, with a focus on sampling the whole of the designated intertidal was created, and sampling was conducted for sessile species and large mobile invertebrates by point-intercept sampling of vertical transects and band surveys along transects, respectively. In 2002 and 2003, the same types of sampling were conducted, but quadrat sampling for small mobile invertebrates was added and then modified. This project has produced basic data on the presence, abundance, and spatial distribution of substrates and intertidal biota. Additionally, statistical power analyses conducted on the biological data have allowed assessment of the ability of the sampling to detect trends in the abundance of the predominant species. Current sampling has an 80 percent probability to detect +10 percent annual changes in abundance of all targeted species with an α = 0.05; the ability to detect –10 percent trends is not as uniformly high. Various options are discussed for decreasing the spatial variance of the data. The information presented provides a basis for discussion of the major questions being asked, how the sampling design might be reconfigured to be consistent in approach, and how the intertidal monitoring should interface with other potential intertidal monitoring.

Contents

Abstract
Introduction
Methods
Geomorphological, Biological, and Statistical Results
Discussion
Summary/Where Next?
Acknowledgments
References Cited
Appendix A. Statistical Review of Sampling and Analysis Methods for Intertidal Monitoring at Sitka NHP: Final Report
Appendix B. Discussion Points

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Send questions or comments about this report to the author, G.V. Irvine, (907) 786-7069.

For more information about USGS activities in Alaska, visit the USGS Alaska Science Center home page.