Monitoring Benthic Algal Communities: A Comparison of Targeted and Coefficient Sampling Methods

doi:2009.24.2.111

Algae > Volume 24(2); 2009 > Article

Algae 2009;24(2): 111-120. doi: https://doi.org/10.4490/algae.2009.24.2.111

Matthew S. Edwards¹^* and Martin T. Tinker²

¹Department of Biology, San Diego State University, San Diego, CA 92182, USA
²Department of Ecology and Evolutionary Biology, Long Marine Lab, University of California, Santa Cruz, California 95060, USA

*Corresponding Author

Email: edwards@sciences.sdsu.edu

ABSTRACT

Choosing an appropriate sample unit is a fundamental decision in the design of ecological studies. While numerous methods have been developed to estimate organism abundance, they differ in cost, accuracy and precision. Using both field data and computer simulation modeling, we evaluated the costs and benefits associated with two methods commonly used to sample benthic organisms in temperate kelp forests. One of these methods, the Targeted Sampling method, relies on different sample units, each “targeted” for a specific species or group of species while the other method relies on coefficients that represent ranges of bottom cover obtained from visual estimates within standardized sample units. Both the field data and the computer simulations suggest that both methods yield remarkably similar estimates of organism abundance and among-site variability, although the Coefficient method slightly underestimates variability among sample units when abundances are low. In contrast, the two methods differ considerably in the effort needed to sample these communities; the Targeted Sampling requires more time and twice the personnel to complete. We conclude that the Coefficient Sampling method may be better for environmental monitoring programs where changes in mean abundance are of central concern and resources are limiting, but that the Targeted sampling methods may be better for ecological studies where quantitative relationships among species and small-scale variability in abundance are of central concern.

Key words: benthic organisms, environmental monitoring, kelp forest, point contacts, sampling design