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Patterns of shading tolerance determined from experimental light reduction studies of seagrasses
Citation:
Nelson, Walt. Patterns of shading tolerance determined from experimental light reduction studies of seagrasses. AQUATIC BOTANY. Elsevier Science Ltd, New York, NY, 141:39-46, (2017).
Impact/Purpose:
A meta-analysis of data on experimental shading of seagrasses determined that there were consistent response patterns that may assist in management decisions by helping define the scope of expected responses of seagrasses in general to the range of factors that may reduce light availability to seagrasses. The extensive review evaluated the relationship between experimental light reductions, duration of experiment and the meadow-scale seagrass response metrics of biomass and shoot density. While levels of unexplained variation were high due to the multiple factors influencing results, there were highly significant linear relationships of both percent biomass and percent shoot density reduction versus percent light reduction. Duration of exposure affected extent of response for both metrics, but was more clearly a factor in biomass response. Multivariate regressions that included both percent light reduction and duration of reduction as dependent variables increased the percentage of variation explained in almost every case. Biomass tended to show less variation in response to light reduction than shoot density, and may be the preferred indicator of the two. This paper contributes to SSWR 4.02.
Description:
An extensive review of the experimental literature on seagrass shading evaluated the relationship between experimental light reductions, duration of experiment and seagrass response metrics to determine whether there were consistent statistical patterns. There were highly significant linear relationships of both percent biomass and percent shoot density reduction versus percent light reduction (versus controls), although unexplained variation in the data were high. Duration of exposure affected extent of response for both metrics, but was more clearly a factor in biomass response. Both biomass and shoot density showed linear responses to duration of light reduction for treatments 60%. Unexplained variation was again high, and greater for shoot density than biomass. With few exceptions, regressions of both biomass and shoot density on light reduction for individual species and for genera were statistically significant, but also tended to show high degrees of variability in data. Multivariate regressions that included both percent light reduction and duration of reduction as dependent variables increased the percentage of variation explained in almost every case. Analysis of response data by seagrass life history category (Colonizing, Opportunistic, Persistent) did not yield clearly separate response relationships in most cases. Biomass tended to show somewhat less variation in response to light reduction than shoot density, and of the two, may be the preferred explanatory variable. The patterns observed may inform management decisions by helping define the scope of expected responses of seagrasses in general to the range of factors that may reduce light availability to seagrasses.
