Effects of Labyrinthula Infection on the Photosynthetic Capacity of Thalassia Testudinum
Blackened, necrotic lesions on Thalassia testudinum leaves are frequently associated with seagrass die-off in Florida Bay. A previously undescribed species of the marine slime mold, genus Labyrinthula, is the primary causal agent of these lesions. When Labyrinthula infection was present, variations in lesion coverage resulted in significant differences in dry-weight based photosynthesis versus irradiance (P/I) responses of Thalassia leaf tissue, reducing photosynthetic capacity and oxygen output. Maximum photosynthetic rate, Pmax' decreased to below zero when lesions covered 25% or more of the leaf tissue. In addition, respiration rates in infected leaves were up to three times greater than in adjacent, un infected tissue. Alpha (α), the initial slope of the P/I relationship, exhibited little change with low lesion coverage but was usually reduced with higher lesion coverage. These results show that the presence of Labyrinthula lesions impair photosynthesis of Thalassia leaf tissues and might reduce oxygen available for transport to belowground tissues, possibly making Thalassia more susceptible to hypoxia and sulfide toxicity.
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Document Type: Research Article
Publication date: 1994-05-01
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