Sea grass responses to long-term light reduction by brown tide in Upper Laguna Madre, Texas: Distribution and biomass patterns

This report documents the effects of reduced light conditions due to decreased water clarity on sea grass populations. Decreased water clarity in upper Laguna Madre, Texas occurred abruptly due to a large-scale brown tide. This phytoplankton bloom first occurred in June, 1990 and has persisted. Since a multidisciplinary study was in progress prior to the first bloom, the decrease in sea grass biomass was able to be directly linked to this decrease in water clarity. The decrease in biomass, in the form of diminishing new shoots, was more pronounced in the south where light attenuation was greatest. The effect is cumulative, eventually leading to a change in distribution.