REPRODUCTIVE PHENOLOGY OFLAMINARIA SACCHARINA(L.) LAMOUR. (PHAEOPHYTA) AT THE SOUTHERN LIMIT OF ITS DISTRIBUTION IN THE NOTHWESTERN ATLANTIC OCEAN^1,2

Abstract

Laminaria saccharina (L) Lamour. Sporophytes were monitored monthly from October 1982 to September 1983 to investigate reproduction phenology and relationshiops to growth paatterns aaat its southern limit of distribution in the northwest Atlantic Ocean (Long Island Soundd). Plants exhibited an annual growth pattern. Growth raate, bladelehgth, maximum width, area, stiipe lehgth an wet weight swhoed the same seasonal pattern and reached maximum values between May and June. Only blade thickness continued to increase tthrooughout the ovservation period. Blade dissintegration occurred dduring August and September. Reproductive sporophytes occurred throughout the observation period; the greatest frequency of appearance occurred in October (43.8%) and June (37.8%). The blade area covered by sori ranged from 2.4% (Janaury) to 6.1% (August). Meiospore release under laboratory conditions was maximum in May and minimum in July. No meio‐spores were released in August Sporulation was not correlated with meristematic growth of nitrogen content How ever, reproductive plants were generally larger and thicker throughout the sporulation period, and had a greater carbort content is spring than nonreproductive plants. Fecundity and reproductive success of female gametophytes were maximum in spring and minimum in winter. The growth of early sporophyte stages in the laboratory was greatest in early spring; however, juvenile macroscopic stages were hardly observed in the field during summer months due to warm water temperatures. “Over‐summering” of gamelophytes and / or microscopic sporophytes may account for the annual cycle of Laminaria at its southern limit of distribution.

Productivity and life history of Laminaria longicruris at its southern limit in the Western Atlantic Ocean

“…Seasonal patterns of tissue nitrogen (Table 2) are similar to those of Gagne et al (1982) with the lowest values in July presumably being unable to support growth. Seasonal trends in tissue nitrogen and carbon contents (Table 2) are similar to those presented for L. saccharina from LIS by Lee & Brinkhuis (1986). However, winter nitrogen content was slightly higher in L. saccharina.…”

“…Luning (1988) has shown that sorus formation in L. s a c c h a r i n a from Helgoland is indeed a short-day response. However, L. s a c c h a r i n a In LIS undergoes 2 peak periods (spring and autumn) of sorus formation (Lee & Brinkhuis 1986). Although some tagged individuals in the present study, and monitored through 1985, also behaved in a similar manner to L. s a cc h a r i n a , this was not the case for the different generations in general.…”

Aspects of the reproductive phenology ofLessonia trabeculata(Laminariales: Phaeophyceae) from three populations in northern Chile

“…The autumn blades, which had greater reproductive areas and biomass, released spores that produced gametophytes having higher fertility and reproductive success than spores released in other seasons of the year. Occurrence of seasonal variation in spore development has been recognised in L. saccharina (Lee & Brinkhuis 1986), Ecklonia maxima (Osbeck) Papenfuss (Joska & Bolton 1987), and Macrocystis pyrifera (L.) C. Agardh (Reed et al 1996). Because all the cultures during the study were kept in a stable regime known to be optimal for Lessonia (Avila et al 1985;Edding et al 1990;Orrego 1992;Fonck et al 1998), the seasonal variations observed in the development of the microscopic phase were assumed to be dependent on the intrinsic characteristics of the spores.…”

“…Germination of the spores was recorded as a percentage after 7 days in culture in contrast with the original settled density (Fonck et al 1998). The fertility of the female gametophytes was determined at 30 days of culture and expressed as the percentage of female gametophytes bearing oogonia compared with the total number of female gametophytes observed (Lee & Brinkhuis 1986). Reproductive success was expressed as the percentage of sporophytes with more than three cells, of the total individuals (female gametophytes + sporophytes) found after 40 days of culture (Lee & Brinkhuis 1986).…”

“…The fertility of the female gametophytes was determined at 30 days of culture and expressed as the percentage of female gametophytes bearing oogonia compared with the total number of female gametophytes observed (Lee & Brinkhuis 1986). Reproductive success was expressed as the percentage of sporophytes with more than three cells, of the total individuals (female gametophytes + sporophytes) found after 40 days of culture (Lee & Brinkhuis 1986). The control times for reproductive variables were chosen following data in the literature for the same species (Edding et al 1990(Edding et al , 1993Fonck et al 1998) permitting comparison among all the cultures, where different development times reflected the maturity of the spores.…”