Matching salinity metrics to easturine seagrasses for freshwater inflow management
Estevez, E.D. (2000). Matching salinity metrics to easturine seagrasses for freshwater inflow management, in: Bortone, S.A. (Ed.) Seagrasses: monitoring, ecology, physiology, and management. pp. 295-307
In: Bortone, S.A. (Ed.) (2000). Seagrasses: monitoring, ecology, physiology, and management. CRC Marine Science Series, 16. CRC Press: Boca Raton. ISBN 0-8493-2045-3. 318 pp., more
In: Kennish, M.J.; Lutz, P.L. (Ed.) CRC Marine Science Series., more
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| Abstract |
Changes in the amount, timing, or location of freshwater inflow are recognized as primary stressors to estuarine and marine seagrass species and communities. Progress has been made assessing impacts of too little or too much freshwater inflow, by using salinity as a first-order stressor per se, and as an indicator of associated, second-order stressors. Seagrass species can be associated with typical mean values of salinity and also with extreme values of salinity where species persist or perish. But a growing body of anecdotal, observational, and experimental data suggests that patterns of salinity variation also have significant effects on seagrass presence, persistence, and condition. To set the stage for a discussion on whether metrics of salinity variation can be identified that are meaningful in terms of seagrass biology, exarnples of salinity impacts to seagrasses are reviewed. Next, a simple theoretical model is proposed for mean salinity and salinity variation across an estuarine gradient, and implications are illustrated for interpreting seagrass data and selecting salinity metrics. Existing published data on the salinity range of wigeongrass (Ruppia maritima) are investigated to illustrate how tolerable salinity ranges can be interpreted in the context of the model ( and misinterpreted by water managers). Types of salinity data are evaluated. Principal among these are historic data, records of continuous, in situ instruments, and outputs available from hydrodynamic and salinity models. A coefficient of salinity variation is proposed for seagrass studies based on the use of tidal datum planes (mean high water, mean lower low water, etc.) to describe continuous changes of water level in estuaries. |
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