Meeting Abstract
2.6 Saturday, Jan. 4 09:15 Unknown but common: The ecophysiology of the green alga Microdictyon setchellianum YAMASE, N. *; SMITH, C.; Chaminade University of Honolulu; University of Honolulu at Manoa nicole.yamase@student.chaminade.edu
Understanding how physical factors affect the photosynthesis and growth of macroalgae are crucial to estimating their ecological success and the health of the reef community. The macroalga Microdictyon setchellianum is a common plant in many reefs as a component in the understory or as a principal element of reef cover, as in the Northwestern Hawaiian Islands. Despite its abundance, rates of growth and photosynthesis for this alga were unstudied. We began initial characterizations, using three approaches: manipulation of irradiance from ambient to 350 µmol photons m-2 s-1 in mesocosm setup; a controlled nutrient experiment again using mesocosms; and determination of light response curves for the base, center, and outer edge sections of the alga, for freshly collected materials. There was no significant difference in growth rates between the shaded and unshaded samples; plants attained significant growth in a two week period (p<0.005). There was no difference in growth between the control and nutrient treatments. Photosynthetic parameters ETRmax and Ek remained unchanged throughout the experiment. Growth rate decreased significantly in the experimental group (P<0.001) when nutrient amounts were doubled. Finally, photosynthetic performance parameters documented differences between the base of blades and center of the plant (P<0.011), suggesting self-shading is a common occurrence in situ. M. setchellianum appears to be a shade-tolerant alga, which allows it to grow in both low and moderately high irradiance regimes. Finally, in oligotrophic conditions, this plant can sustain growth comparable to other well-known native species.
