Ecological Growth Strategies in the Seaweeds Gracilaria foliifera (Rhodophyceae) and Ulva sp. (Chlorophyceae): Photosynthesis and Antenna Composition

Abstract

Observations have been made on photosynthesis (oxygen evolution) and seasonal fluctuations in antenna pigments in 2 seaweeds which CO-occur in the vicinity of Beaufort, North Carolina, USA. Gracilaria foljifera (Rhodophyceae) and Ulva sp. (Chlorophyceae) were grown in outdoor continuous-flow cultures a t ambient incident light (I,) and .13I,. Pigment contents and accessory pigment: chlorophyll a ratios were higher at ,131, than at I,. Total pigment levels were correlated with soluble N in seaweed tissue. During the spring/summer growing season, pigment levels were low and peaks i n pigment content followed nutrient pulses in the ambient seawater. Pigment contents in both Species were higher in winter In G. foliifera, the R-phycoerythrin: chl a ratio was highest in fall-winter and lowest in summer. The higher growth rates achieved by Ulva sp. reflected the higher rates of photosynthesis measured in this species. Photosynthesis-light curves showed that Ulva sp. had a higher photosynthetic capacity (P,, = 430 ymol O2 evolved g dry wt-' h-') and initial slope (in shadeacclimated plants) than G. folijfera (P,, = 160 pm01 0, evolved g dry wt-' h-'). Increased pigment contents in shade plants of both species resulted in enhanced photosynthetic performance at subsaturating light intensities. It appears that the effect of transient pigment increases in the summer was to increase P, , , temporarily while, in winter, the effect was to limit the decrease in integrated net photosynthesis in the face of decreased light and temperature.

Seasonal changes in the pigment composition of natural population of Gracilaria domingensis (Gracilariales, Rhodophyta)

“…The highest concentrations were recorded in the months with lowest sunlight (July, August, May and June) and the lowest in the months with elevated sunlight levels (December, January and February). These variations are similar to those described by other authors, who reported an increase in total soluble proteins and phycobiliproteins in winter and a drop in summer (Kosovel & Talarico, 1979;Rosenberg & Ramus, 1982;Campbell et al, 1999;Aguilera et al, 2002;Orduña-Rojas et al, 2002). In this study, the association between high protein and pigment concentrations, lower solar irradiance and high nitrogen concentrations was clear.…”

Computer‐automated flow respirometry: Metabolism measurements on a Caribbean reef flat and in a microcosm1

“…Harris 1978; Rosenberg and Ramus 1982;Porter 1980;Porter et al 1984). We suggest two ways that light saturation parameters for a whole community can increase.…”

Short-term effects of CO2, nutrients and temperature on three marine macroalgae under solar radiation

“…phycoerythrin and phycocyanin) contents of E. elongata were not influenced by carbon and nitrogen treatment, contrary to previous studies: in Gracilaria spp. phycoerythrin increased with seawater N concentration and internal N content (Rosenberg & Ramus 1982, Figueroa et al 2010). On the other hand, Gao & Zheng (2010) observed a decrease in the phycoerythrin content of Corallina sessilis when exposed to high CO 2 (1000 ppmv) for 30 d. The short experimental duration of the present study may explain the lack of change in phycobiliprotein levels.…”