Botanica Marina 49 (2006): 72–78  2006 by Walter de Gruyter • Berlin • New York. DOI 10.1515/BOT.2006.009 Article in press - uncorrected proof 2006/57 Carrageenan of Eucheuma isiforme (Solieriaceae, Rhodophyta) from Yucata ´ n, Mexico. II. Seasonal variations in carrageenan and biochemical characteristics Yolanda Freile-Pelegrı´n* and Daniel Robledo Department of Marine Resources, CINVESTAV, Km 6 Carretera Antigua a Progreso, Cordemex, 97310, A.P. 73, Me ´ rida, Yucata ´ n, Mexico, e-mail: freile@mda.cinvestav.mx * Corresponding author Abstract Seasonal variation in the biochemical composition and carrageenan content were studied in Eucheuma isiforme from Yucata ´ n, Mexico. Dry weight and carrageenan yield were lowest during the late cold-early dry seasons and highest during the late rain-early cold seasons. Total car- bohydrates varied seasonally and were similar to varia- tions in carrageenan yield. The factors responsible for the seasonal variation of biochemical and carrageenan char- acteristics of E. isiforme from Yucata ´ n are interrelated, and their effects are difficult to separate. Thus our results suggest that biochemical composition can be related to seawater temperature and hence to growth, while inci- dent light and nutrients can influence the carrageenan quantity. Although no direct growth estimation has been made, changes in E. isiforme dry weight suggest that active growth starts from the late cold season throughout the dry season when seawater temperature is optimal. The above coincided with an increase in protein content and a decrease in total carbohydrates linked to reduced carrageenan synthesis. Carrageenan content is higher during the early cold season, coinciding with high nutri- ent concentrations and reduced light. Carrageenan yield and viscosities in E. isiforme were near levels required for Eucheuma species in industrial applications, suggesting potential commercial/industrial use of this species. These results should be taken into consideration for the man- agement of natural populations as well as for mariculture of this species on the Yucata ´ n coast. Keywords: biochemical composition; carrageenan; Eucheuma isiforme; Yucata ´ n. Introduction Increasing worldwide demand and development of new applications for carrageenan have added urgency to the search for new or additional raw material sources. Eucheuma isiforme (C. Agardh) J. Agardh is a promising carrageenan source that grows in the Gulf of Mexico and Caribbean Sea. Its ecological, reproductive and bio- chemical aspects are well documented for populations on the US Gulf coast (Dawes et al. 1974a,b, Dawes 1977), and indicate seasonal variations in carrageenan content and quality. Environmental factors are known to influence phycocolloid yield and quality (Chopin et al. 1990, Ekman and Pederse ´ n 1990, Brown 1995), and dif- ferent physiological and environmental tolerances may influence variation in carrageenan content between indi- viduals of the same species. Recent reports have shown that oceanographic and environmental conditions differ substantially between the tropical Yucata ´ n Peninsula and the subtropical Florida Peninsula, with consequent dif- ferences in the physiological responses of seaweeds. Thus, differences in photosynthetic capacity and bio- chemical constituents have been reported for the aga- rophyte Gracilaria cornea J. Agardh from the Florida Keys (Dawes et al. 1998) and those from the Yucata ´ n coast (Ordun ˜ a-Rojas et al. 2002). Higher agar yields and gel strength have been also reported for G. cornea from the Gulf of Mexico coast of the Yucata ´ n Peninsula (Freile- Pelegrı´n and Robledo 1997) in comparison with thesame species from the Caribbean coast (Espinoza-Avalos et al. 2003). A topographic upwelling on the Yucata ´ n shelf has been described as one of the most important upwelling regions on the western oceanic margin (Merino 1997). These conditions may influence the physiology and bio- chemical composition of Eucheuma isiforme found in Yucata ´ n in ways different from those described for Flo- ridian populations. The scarcity of available data for E. isiforme from Yucata ´ n prevents any assessment of its potential use for carrageenan extraction. We reported previously on the effect of extraction conditions on E. isiforme carrageenan content and properties (Freile- Pelegrı´n et al. 2006). Determining biochemical composi- tion and phycocolloid characteristics may help in understanding the physiological status of the alga, pro- viding data for its use as raw material for industry. In an effort to develop this species for industrial use, we stud- ied the effect of several environmental factors on its dry weight, total carbohydrates, protein, ash, C:N ratio, car- rageenan content and carrageenan properties. Materials and methods Site location, material collection and preparation The Yucata ´ n coast is a limestone platform characterized by marked seasonal differences in environmental condi- tions: a dry season (March–June) characterized by sunny days and calm waters, a rainy season (July–October) with abundant rainfall and high air temperatures and a