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| Species Trend Graphs Information and Disclaimer |
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Please read before viewing the MARINe Trend Graphs
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MARINe Trend Graphs The following graphs contain data from MARINe monitoring over the past 22 years. They are grouped by county and by island. These graphs are based on the “abundance” of the species over time. Abundance is determined by surveying the 12 targeted plants or animals each fall and spring at locations where the species are well represented. This can be done by: (1) counting individual animals in fixed plots
(such as abalone, above) or by (2) taking photographs in the same location within a site and determining the “percent cover” of the targeted animal or plant. Percent cover is determined by identifying the animal or plant species under 100 points in the photo. Percent cover is used to determine abundance of colonial animals (such as anemones) and marine algae when it is not possible to count individuals. A full description of the way these counts are done for individual species is contained in the webpage under the section “Sampling Methods”. Because there is so much natural variation in a given species between sites, the most important factor to consider in looking at these graphs is the trend itself. For example, has the number of sea stars been increasing at sites in Orange County or decreasing? The actual number of an individual species at one site compared to another is not as important as whether the numbers are decreasing or increasing at sites consistently along the coast. Trend graphs are tools that, in combination with other data, can help scientists detect locations along the coast where a specific natural or man-made problem is causing an unusual change in the population. They also provide information about seasonal fluctuations and about the long-term health of the population.
How to Understand the Graphs Abundance is shown as mean percent cover for species scored by point-contacts within plots or along transects and as mean number of individuals for species counted within plots. The vertical scale for all percent cover graphs is 0-100%. The vertical scale for count graphs can be 0-50, 0-100, or 0-150 individuals, depending on the species. The horizontal time scale is different for each graph, ranging from earliest to most recent sampling dates. Sampling periods are abbreviated as the first two letters of the season and the last two numbers of the year (e.g., SP96 = Spring 1996 and FA02 = Fall 2002).
A Cautionary Note These species dynamics graphs are provided for preliminary comparisons of temporal changes among target species for representative regional sites. The data may raise interesting ecological questions and management issues; however, they should not be used in any formal manner (e.g., resource management, presentations, publications) without contacting the appropriate Principal Investigators (see “Monitoring Groups”) for interpretation and permission. For example, most percent cover scoring is based on the top-most visual layer. Sand or ephemeral algae may cover a target species during some surveys but not others, so additional information is necessary for proper interpretation of abundance patterns. Also, the data represent trends within specific fixed plots; therefore, they cannot be used to characterize entire sites without incorporating other MARINe data. Finally, the graphs may contain inadvertent errors. Any such errors will be corrected in subsequent postings. |
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Updated: 2/28/2005 |
