Seasonal and interannual variation of sterols in macrophytes from the Pacific coast of Baja California Peninsula (Mexico)

The seasonal and interannual proximate and sterol composition were assessed in two red (Gelidium robustum, Gelidiaceae andGracilariopsis sjoestedtii, Gracilariaceae), two brown (Ecklonia arborea, Lessoniaceae andMacrocystis pyrifera, Laminariaceae), and two green (Ulva lactucaandUlva clathrata, Ulvaceae) macroalgae species and the seagrassPhyllospadix torreyi(Zosteraceae) sampled over 3 years in a subtropical climate in Baja California Sur, Mexico. Each macroalga had a particular sterol composition that was typical of their taxonomic group. The red algae had cholesterol as the major sterol; 92% on average inG. robustumand 90% inG. sjoestedtii, followed byt-dehydrosterol and brassicasterol. In the brown algae the major sterol was fucosterol, which accounted for approx. 90% and 92% of total sterols forM. pyriferaandE. arborea, respectively, followed by campesterol (7% and 5%) and isofucosterol (1.5% and 1.3%). The green algae had isofucosterol as the major sterol, with 92% on average forU. lactucaand 87% forU. clathrata, followed by cholesterol, fucosterol, and brassicasterol or norcholesterol. The seagrassP. torreyihad beta-sitosterol as the major sterol (39 to 89%, depending on the season), followed by campesterol (4 to 7%), stigmasterol (3 to 6%), and isofucosterol (1.7 to 3.5%). Four (cholesterol, campesterol, fucosterol, and isofucosterol) of the 14 sterols identified in macroalgae and the seagrass could be used to differentiate between classes (Florideophyceae - red, Phaeophyceae - brown, Ulvophyceae - green, and Monocots - seagrass) both seasonally and interannually. The seasonal and interannual sterol composition of macroalgae and seagrass was quite stable, with the exception of redG. sjoestedtiisampled in August and green macroalgaU. lactucaand seagrassP. torreyiboth sampled in May 2002. Seasonal and interannual variations of proximate and sterol composition are discussed in relation to their reproductive state and environmental parameters.

Automated summary

The study assessed the proximate and sterol composition of different macroalgae species and seagrass over 3 years in a subtropical climate. Each macroalgae species had a distinct sterol composition typical of their taxonomic group. The seasonal and interannual variations in sterol composition were relatively stable, except for a few exceptions likeG. sjoestedtiisampled in August andU. lactucaandP. torreyiboth sampled in May 2002.