ABSTRACT
The study of photosynthetic fluorescence characteristics of algae is important for the analy-sis of photosynthesis and carbon sequestration of algae. In July 2017, six common species of macroalgae found in Gouqi seaweed beds were collected, including Ulva pertusa, Cladophora stimpsonii, Grateloupia livida, Sargassum thunbergii, Polysiphonia urceolata, and Hizikia fusifarme. In the field, the maximal quantum yieids of photosystem2(Fv/Fm) and rapid curves (RLCs) were mea-sured by using pulse-amplitude modulated fluorometer (Diving-PAM). The results showed that the measured maximal quantum yields of U. pertusa, C. stimpsonii, G. livida, S. thunbergii, P. urceolata, and H. fusiforme were 0.702, 0.704, 0.457, 0.618, 0.421 and 0.567, respectively. The Fv'/Fm' of six species were in order of C. stimpsonii>U. pertusa>S. thunbergiiï¼H. fusiformeï¼G. lividaï¼P. urceolata. The difference between each species and significant difference was found in U. pertusa, C. stimpsonii, and H. fusiforme. H. fusiforme, S. thunbergii and U. pertusa had higher Pm and α than other species, indicating their higher photosynthetic capacity and better adaptation in higher light condition. However, G. livida had higher α but lower Ik, indicating G. livida had higher photosynthetic capacity in low light condition. In a word, differences of photosynthetic capacity and light intense tolerance between the three phyla of macroalgae were found and we suggested H. fusiforme, S. thunbergii and U. pertusa had stronger photosynthetic capacity and light intense tolerance. Our results could provide theoretical basis for the seaweed bed conservation and carbon sequestration of macroalgae.
Subject(s)
Seaweed , China , Chlorophyta , Fluorescence , Islands , Light , Photosynthesis , Rhodophyta , SargassumABSTRACT
Marine ranching is an effective way to protect and restore coastal fishery resources. In order to assess the impacts of marine ranching construction on the trophic niches and interspecific competition of Sebastiscus marmoratus and Larimichthys polyactis, we analyzed the relationship between the changes of intraspecies trophic niche and the interspecific competition, based on the carbon and nitrogen stable isotope data of these two species collected from 2013 to 2016. The results showed that the intraspecies trophic niches of both species increased significantly in marine ranching area from 2013 to 2016. The total area of the convex polygon (TA) niche increased from 1.89 to 12.43 for S. marmoratus, and increased from 0.34 and 8.86 for L. polyactis, with the interspecific niche overlap area of these two species increasing from 0.13 to 7.69. The standard elliptic trophic niche increased from 1.11 to 4.94 for S. marmoratus, and from 0.14 to 4.06 for L. polyactis, with the interspecific niche overlap area increasing from 0 to 0.26. Values of the δ13C and δ15N of both species showed a tendency of decreasing with time, with significant changes of δ13C, but non-signi-ficant for δ15N. Dietary overlap between those two species increased from 68.9% to 90.6%.