Relationships between critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum

Abstract

SUMMARY: This study was designed to determine the critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum. Sampling and measurement of natural light conditions were carried out in the S. macrocarpum population at a depth of 8 m off Kiwado in Fukawa Bay, Yamaguchi Prefecture, Japan, from April to June 1998. Photosynthesis and respiration of the juvenile thalli, and diurnal changes in solar irradiance were measured for the same period. The critical photon irradiance for growth of the juvenile thalli observed on the population floor was 1.0–1.5% on the sea surface. The photosynthetic rate of leaf of juvenile thalli increased linearly with increasing photon irradiance when light levels were lower than 50 μM/m2 per s. The respiratory rate and light compensation point of the juvenile thalli were 2.49 μL O2/cm2 per h and 4.98 μM/m2 per s, respectively. The daily compensation point was estimated with a mathematical model based on photosynthesis–light equations and diurnal changes in solar irradiance. For a day of average solar irradiance over the period of the present study, the estimated daily compensation point of the juvenile thalli was 1.3% on the sea surface. This value agreed well with the observed critical photon irradiance for growth of juvenile S. macrocarpum on the population floor. The results of the study confirm that the mathematical model is effective for estimating the daily compensation point.

High water-temperature tolerance in photosynthetic activity ofZostera marinaseedlings from Ise Bay, Mie Prefecture, central Japan

“…However, respiration of Z. marina seedlings was in the range from −1.1 to −4.5 μL O 2 /cm 2 per h, mostly identical to the values of macroalgae, −1.82 to −5.0 μL O 2 /cm 2 per h 23,32,33 . The initial slopes for Z. marina seedlings ( P maxg / I k , 0.04–0.21, data not shown) are low compared with these of macroalgae (0.41–1.38), 23,33 because Z. marina have non‐photosynthetic organs such as rhizomes and roots. Therefore, it is thought that seedlings require high light levels because they can not absorb lower irradiance efficiently.…”

Assessment of optimal depth and photon irradiance for cultivation of the brown alga, Sargassum fulvellum (Turner) C. Agardh

“…As noted by Murase et al (2000), the daily compensation point of macroalgae, such as Sargassaceae and Laminariaceae, provides useful information for fisheries, particularly with respect to marine forestation and to aquaculture. To decide a suitable place or depth for an artificial reef or culture facility, it is necessary to select a site where the available light routinely exceeds the daily compensation point.…”

Estimation of light requirement for growth of Zostera japonica cultured seedlings based on photosynthetic properties

“…where I max indicates the maximum I 0 during daytime and D is the day length from sunrise to sunset [29]. In the present study, we used the values of I max and D in each season.…”

“…Water temperatures were controlled by using an improved type of temperature-gradient culture [19,20,[34][35][36][37]. For the photosynthesis and respiration experiments, six to nine samples of whole Z. japonica seedlings were used, and the photosynthetic and respiratory activities were measured with an improved type of differential gas volumeter [27,29,31,[38][39][40][41][42][43][44] on the 6th day in culture. Photosynthesis and respiration were measured at eight different PPFDs (0, 12.5, 25, 50, 100, 200, 400, and 800 lmol photons m -2 s -1 ) generated using a projector lamp (Master HI-LUX 1000 W; RikagakuSeiki, Tokyo, Japan).…”

“…Light condition is one of the most important factors in the growth of marine plants including seagrasses [25][26][27][28][29][30][31]. Thus far, many studies have been carried out on the light requirements of Zostera marina [22,25,26,28,[30][31][32]; however, there are no studies on Zostera japonica in this regard.…”