ABSTRACT

Halodule wrightii

(Aschers.) located off Mullet Key (Fort DeSoto Park), Pinellas County, Florida, were subjected to

in situ

light reductions of 43, 60, and 86% from September 1994 to early March 1995 and compared with control plots for changes in morphology and photosynthesis vs. irradiance (PE) response. Winter die-back caused a 50% reduction in biomass and shoot density in control plots between September and February/March. A further reduction in total and non-photosynthetic biomass of 50% compared to control occurred as a result of treatment effect regardless of the amount of light reduction. However, reduction in photosynthetic biomass was related to the amount of light reduction (r

= 0.89). There was an inverse relationship between light reduction and shoot number (r

= 0.98). Leaves on shoots within the 43% light reduction plots were longer than leaves on shoots in either control or other light reduction treatment plots after the second month of the experiment. This is probably a morphological response to light reduction, as reported for other species.