Seasonal variation in standing crop of the seagrassSyringodium filiforme and associated macrophytes in the Northern Indian River, Florida

Seasonal variation in the standing crop of the seagrassSyringodium filiforme and its associated macrophytes was studied in a northern basin of the Indian River, a large mesohaline lagoon in central Florida, near the northern distributional limit ofS. filiforme. The minimum standing crop occurred from February through April and the maximum in September. Two other seagrasses,Halodule wrightii andHalophila engelmannii, together with a drift algal community, occurred in the study quadrat, but were not major components of the macrophytic system. The formation of sizeable sandy patches within Indian River seagrass beds is partially due to the burrowing activities ofLimulus polyphemus. Thermal stresses associated with the northern geographicalS. filiforme range may contribute to this phenomenon by restricting annual production, hence limiting patch regrowth.