Length Of Thalli Research Articles

Spatiotemporal variation in phenology of the invasive brown macroalga Sargassum muticum (Yendo) Fensholt and the environmental parameters relationships along four different sites on the Atlantic coast of Morocco

The alien brown seaweed Sargassum muticum (Yendo) Fensholt is currently observed along the coasts of Morocco. The present study aimed to evaluate the impact of physicochemical parameters on the distribution of S. muticum at four sites on the Atlantic coast of Morocco harvested between 2019 and 2020. This study showed that the highest biomass, thalli length, and fertility values were recorded in sampling sites characterized by optimal physicochemical (temperature, pH, and salinity) and nutrient H₃PO₄ during summer. The highest biomass values were recorded in August for Sidi Bouzid and Moulay Abdellah sites, conversely, in Saada and Jorf Lasfar sites the highest values were observed in February and March respectively. The thallus length was slightly larger in Moulay Abdellah site with 77.30 ± 14.09 cm compared with the three other sites during the summer/spring periods. Minimum thalli length was recorded in September for all studied sites. The thalli of S. muticum were fertile earlier in Sidi Bouzid and Saada during spring and peaked during the summer season for all studied sites showing a positive correlation with increasing temperature.Finally, the collected data shows that indeed physicochemical parameters influence bioecological parameters. Thus, contributed to a better understanding of the temporal variation of S. muticum phenology on the Moroccan Atlantic coast, these data provide the necessary information for coastal marine management and biomonitoring program as well as sustainable utilization of this renewable marine resource.

Effects of Hyphomonas Strains on the Growth of Red Algae Pyropia Species by Attaching Specifically to Their Rhizoids.

Bacteria and marine macroalgae form close associations, while various bacteria affect the morphogenesis and growth of macroalgae. Hyphomonas strains exhibit normal morphogenetic activity in protoplasts of the red alga Pyropia yezoensis (nori). However, the effects of the bacteria on the growth of Pyropia from protoplast cells to regenerated thalli remain unknown. Here, we assessed the growth of P. yezoensis and Pyropia tenera using combined cultures of three Hyphomonas strains (LNM10-16, SCM-2, and LNM-9) and three algal media (artificial seawater with vitamins, artificial seawater, and natural seawater) over 7weeks. Third week after culture, the three Hyphomonas strains showed almost similar levels of normal growth activity for both Pyropia species. However, at 7weeks, significant differences were observed among the three Hyphomonas strains in terms of length, length-to-width ratio, and normal morphology of Pyropia thalli. LNM10-16 significantly promoted the thalli length and length-to-width ratios of both Pyropia species in artificial seawater without vitamins and natural seawater, compared with the other two Hyphomonas strains. P. yezoensis cultured in artificial seawater with vitamins showed a much higher demand for LNM10-16 in development of the thalli length than P. tenera. These results may be explained by differences in the growth activities of Hyphomonas strains and the nutrient requirements of Pyropia species. Furthermore, the bacteria were more specifically attached to the rhizoid surfaces of both species. This study is the first to reveal that Hyphomonas strains affect the growth of Pyropia species by attaching to their rhizoids.

Do Protected Areas influence populations of the threatened red alga Phyllophora crispa along the southwestern coast of Crimea (the Black Sea)?

The perennial sciaphilous alga Phyllophora crispa (Phyllophoraceae, Rhodophyta) belongs to the main community-forming species of the Black Sea but due to the catastrophic degradation of its populations, it has been listed as an endangered species in the Red Data Book of the Russian Federation. Phyllophora crispa off the southwestern coast of Crimea is preserved within six Protected Areas (PAs) established between 1972 and 2017, which include the narrow 300-m-wide strips of coastal waters ranging from 0.0597 km2 to 0.208 km2 in area. Despite a long existence, the degeneration of P. crispa assemblages has been shown in some of them that may indicate inefficient measures aimed at conserving bottom communities in Marine PAs (MPAs) and the need to optimise the regional PA network. Therefore, this study addresses assessing the effectiveness of the preservation of P. crispa in MPAs along the southwestern coast of Crimea, and it aims at two main objectives: to compare the status of P. crispa populations in the study area at present and before the MPA establishment, and to assess their current state in the marine protected and unprotected areas. In 2015–2020, the density, biomass, weight and length of P. crispa thalli were determined in five MPAs ranged in age 33–48 years of protection and in 16 unprotected water areas, at depths from 0.5 m to 20 m. A comparison of the obtained and published data for the 5 m to 20 m depth range showed that from 1964–1967 until 2015–2020, the P. crispa biomass in the study area decreased on average 2.7-fold, the density 1.5-fold and the thallus weight 2.0-fold. Evaluating the decline of the populations of P. crispa along the depth range of 5–15 m showed that it was most pronounced at a 15-m depth, being statistically significant in biomass and thallus weight. At the same time, an analysis of variance showed no effect of protection on the between-year change in P. crispa population parameters. In addition, in 2015–2020, there was no statistically significant difference in the average biomass and density of this species inside and outside the MPAs. The average weight and length of thalli did not differ due to protection either, except for a depth of 10 m where values of these parameters were, respectively, 3.3 times and 1.4 times higher inside than outside MPAs. One explanation for the non-significant MPA effect on the state of populations of P. crispa could be a lack of statistical power in our study. Another one was the small area and low width of MPAs, which makes the seaweed communities vulnerable to negative impacts near the MPA borders. To improve the effectiveness of the conservation of P. crispa in the southwestern Crimea, it was recommended to increase the MPA coverage, create buffer zones around MPAs and take measures resulting in environmental improvement throughout the region.

Spatiotemporal patterns of phenology of the alien Phaeophyceae Sargassum muticum on the Atlantic coast of Morocco

The present study focused on the dynamics of the phenology and life cycle of the Phaeophyceae invader Sargassum muticum at three sites on the Atlantic coast of Morocco over a period of two years (2013 and 2014). The results showed that S. muticum has two distinct growth phases; one with slower growth in winter followed by one with faster growth in spring-early summer, when the species exhibited high elongation and branching activities with thalli length ranging from 1 to more than 5 m depending on the study site. The site S1, with a rocky substratum covered by submerged sands, promotes thalli elongation, with maximum lengths of 643.33 11.10 cm recorded in July. At the rocky sites (S2 and S3), the maximum length of the seaweed depends on the pools’ depth. Although the elongation of thalli is enhanced by the water body depth, the settlements’ density (5-48 ind. m–2) seems to be mainly related to the nature of the substrate. The maturity index progressively increases from spring to early summer, when it reaches the highest values. S. muticum seems to be more abundant and more easily acclimated in shallow rockpools (sufficiently lighted and semi-exposed to wave action at the mid and lower tidal levels) than in protected sandy bottom sites with low hydrodynamic forces.

Sea bottom culture ofChondracanthus chamissoi(Rhodophyta: Gigartinales) by vegetative propagation at Puerto Aldea, Tongoy Bay (Northern Chile)

Seaweed exploitation in Chile has increased over the last decades, resulting in a reduction of seaweeds landings and the overharvesting of natural beds. In response, ecological baselines for their sustainable exploitation and the development of seaweed aquaculture have been implemented. In recent years, the culture of commercial red seaweed Chondracanthus chamissoi has been developed experimentally by spore and vegetative reproduction. These methods are facilitated by the formation of secondary attachment discs (SADs), generated to fasten the inoculated algae to substrates. In this study, the vegetative propagation was carried over an artificial substrate installed in a sea bottom culture system. The biomass yields, total amount of epiphytes, length of new thalli and number of SADs, per season and culture times (1, 2, 3 and 4 months) are reviewed in this work. Chondracanthus chamissoi showed growth under all treatments, with a maximum accumulated biomass of 60 g m−1, recorded in summer, and with no significant differences in biomass yield reported in autumn and spring seasons. A similar pattern was observed for epiphyte biomass, while the greatest SAD number and thalli lengths were recorded in winter.

Invasive or not? The case of Grateloupia turuturu (Rhodophyta, Halymeniales) in the Northern Ionian Sea (Mediterranean Sea)

It has been predicted that Grateloupia turuturu, native of the cold-temperate waters of Japan, is one of the most invasive marine species considered as a threat to global marine biodiversity. However, few studies have been carried out to assess the extent of its spread worldwide. Its seasonal dynamics in the Mar Piccolo of Taranto, a transitional water system in the Northern Ionian Sea, were observed for ten years. Systematic monthly observations were carried out from 2008 to 2018. The length of thalli and density were measured alongside the seawater temperature. Data were processed by means of non-parametric statistical analyses. No invasive behavior was detected for G. turuturu. It seems well established in the Mar Piccolo even though its population is limited to the station of first detection. However, due to its shown preference for plastic substrate, it could become a vector of another urgent threat, that is plastic pollution.

Annelid assemblages on artificial and natural hard substrata differ decades after building: A case study on a one-century old seawall

Although strong differences have been observed between the assemblages on artificial substrata and on natural hard-bottom habitats, little is known about the mechanisms that cause them. The purpose of this study was to examine the differences in Mediterranean low shore annelid assemblages dwelling on an old artificial, vertical hard substratum and a natural, horizontal one. The structure of the Ellisolandia elongata turfs covering the two habitats showed little divergence in terms of length and number of thalli, as well as in available space for epibionts. In this respect, colonization duration might explain the lack of significant dissimilarities in the phytal canopy. In spite of this, statistical analyses showed that the specific composition of the two annelid assemblages differed in a significant manner. Although they shared a set of constant species, their relative abundances were dissimilar and this was especially evident for several species belonging to families Syllidae and Enchytraeidae. Abundance and species richness were significantly higher on natural structures, as expected, but Shannon diversity and equitability indexes were lower. Apparently, the sciophilous condition of vertical surfaces, which do not occur naturally in the area, is the main driver of the differences in species composition and its capital importance remains after colonization processes have occurred.

Growth, artificial seedling raising and cultivation of Sargassum confusum (Fucales, Phaeophyceae) inhabiting the coast of Shandong Peninsula, China

The seasonal growth, seedling raising and artificial cultivation of Sargassum confusum were studied along the coast of Dong Chudao at the mouth of Sanggou Bay (37°02′12″N, 122°33′51″E). We also compared the growth of juveniles at different temperatures (15, 18, 21, and 24 °C) and irradiances (60, 95, and 130 μmol photons m−2 s−1) when seedlings were raised in a greenhouse. Sargassum confusum in Sanggou Bay began to develop receptacles in early April when the seawater temperature reached 10.8 °C. The receptacles matured in July and released the eggs when the seawater temperature reached 21 °C. The S. confusum thallus grew to maximum mean length (126.6 ± 19.8 cm) and reached the highest mean biomass yield (192.2 ± 40 g dwt thallus−1) in July and then rapidly decayed. Both temperature and irradiance significantly affected the growth of S. confusum seedlings (p < 0.05). The seedlings reached 1005 ± 47.6 μm at 21 °C and under 95 μmol photons m−2 s−1 in 2 weeks. The seedlings grew to approximately 0.5 cm in length in the seedling raising pools in approximately 5 weeks and reached 6 cm in the open sea nursery after an additional 4 months. The seedlings were then separated and inserted between the strands of vinylon ropes and cultivated in the open sea until early July when the seawater temperature reached approximately 21 °C and the maximum thalli length reached 116.4 cm on average. The dry weight of S. confusum harvested from a 4-m cultivation rope was 1.48 kg on average, and the dry weight yield was approximately 8.9 t ha−1.

Suspended culture of Chondracanthus chamissoi (Rhodophyta: Gigartinales) in Caleta Hornos (northern Chile) via vegetative propagation with secondary attachment discs

Vegetative propagation of Chondracanthus chamissoi by means of secondary attachment discs (SAD) has been an effective strategy for maintaining the species biomass in natural beds. Suspended culture was used in the present study. Biomass, epiphytes, length of new thalli, and number of secondary attachment discs of C. chamissoi were measured during different seasons as well as different depths (2, 4, and 6 m), and cultivation times (1, 2, 3, and 4 months). The greatest accumulation of biomass, biofouling, and SAD formation occurred during spring cultivation, while maximum lengths were observed in winter. Maximum values of each variable were observed at 2 m depth in most cases.

Phenology of Chondracanthus tenellus (Rhodophyta) in the central Pacific coast of Honshu, Japan

This study reports variations in thallus size, density, and reproductive phenology in a natural population of underutilized seaweed, Chondracanthus tenellus, at Tateyama in the Pacific coast of Japan from August 2014 to October 2016. Growth was monitored by measuring the length and weight of thalli. In addition, a number of thalli fouled by spirobids, coralline, and/or fleshy epiphyte and/or grazing marks were also recorded from February 2015 to October 2016. Density was monitored by counting the number of clumps along a subtidal fixed line of 30 m long (3–4 m in depth). Reproductive efforts were evaluated by counting the number of cystocarps per thallus and carpospores per cystocarp. Average thallus length sharply dropped in October and gradually increased from November to record the maximum length (73.5 ± 2.7 mm) in April 2016. After the season, thalli were damaged by epiphytic algae, spirobids, and bite marks with increase in temperature. It was suggested that high temperature and low nutrition in summer probably induce weakening of thallus and promote fouling by spirobids and epiphyte which accelerate depletion of C. tenellus together with herbivorous animals. Although the population showed a large gametophytic dominance, carposporic gametophytes were found in August to September and May to July with the highest value (20.6%) in September. Maturation of gametophytes probably was induced by long day length or a transition from short to long day. Number of carpospores per cystocarp was 72 ± 15 × 103 in January. Considering the size and cleanliness of thallus, it is preferable to harvest in April.

Morphology, distribution and ecology of the freshwater red algae Paralemanea (Batrachospermaceae, Batrachospermales, Rhodophyta) in Serbia

This paper describes the morphology, distribution and ecology of 15 populations of Paralemanea collected from 2004 to 2011 in 12 rivers in Serbia. On the basis of morphological and reproductive characteristics, two species were identified: P. annulata (12 populations) and P. catenata (3 populations). Morphological (presence of a stalk, thalli length, nodal diameter (ND), internodal diameter (ID), node and internode diameter ratio (ND:ID) and reproductive (arrangement of spermatangial sori, length and diameter of carpospores, presence of Chantransia stage) features described in the literature are generally confirmed in the populations from Serbia. True branching was observed in six populations of P. annulata in the gametophyte stage. False branching (whorled branching) occurred in five populations of both species observed. In the Pcinja (P2), Ibar (IB5) and Crnovrska rivers (CR10), the number of whorled branching was 6-11 (P. annulata). For P. catenata the number of such branching was 3-5 in the Nisava River (N8) and Sokobanjska Moravica River (SM12). False branching appears at damaged thalli, somewhat repairing it. Algae belonging to the Paralemanea genus were found at altitudes from 160 to 780 m (P. annulata), and from 240 to 400 m (P. catenata), at water temperatures ranging from 11.5 to 29?C (P. annulata) and from 12.6 to 17.4?C (P. catenata), in neutral and weakly alkaline waters, with a high level of oxygen concentration, with conductivity ranging from 70 to 433 ?S/cm for P. annulata, and 260 to 440 ?S /cm for P. catenata. It was also observed that P. annulata and P. catenata often grow in oligotrophic conditions and rarely in eutrophic conditions.

Seasonal growth and reproductive status of Grateloupia subpectinata (Rhodophyta) on the east coast of Korea

Reproductive phenological pattern on tetrasporophytes and carposporophytes of Grateloupia subpectinata thalli were observed at Yangyang, on the middle east coast of Korea from January to December 2013. DNA sequences of cox1 gene from 48 selected samples were compared to assure that sample collection is single species, and they were all identical G. subpectinata. Density, length and width of thalli were significantly changed monthly. The maximum of density, length and fresh weight occurred in September, and continuous growth was observed during the autumn and winter. Tetrasporophytes were grown dominantly in October and November, whereas carposporophytes were dominated in September and March. Upright thalli disappeared in June and July and then juveniles were abundant in August. There was a significant difference in length between tetrasporophytes and carposporophytes. These reproductive pattern and seasonality together with phenological data of G. subpectinata would provide valuable information about successful seedling supply for aquaculture of the species in the future.

Phenological study of Sargassum thunbergii (Fucales, Phaeophyta) in Lidao Bay, Rongcheng, China

We conducted a phenological evaluation of Sargassum thunbergii, a common algal species, along the coast of Lidao Bay, Rongcheng, China. The local S. thunbergii population entered a maturation period from early June to mid-August, when seawater temperature was 14.4 to 25.1°C. Our results suggest an increase in temperature and day length during this period initiated thalli maturation. Inhabitants of the low tidal zone had higher thalli length and biomass compared with those from the mid-and high tidal zones. We observed a switch in the length frequency distribution and contribution of length classes to biomass between the small (<20 cm) and long (20–79.9 cm) length classes at the time of thallus maturity. This suggests there is a trade-offbetween sexual reproduction and vegetative regeneration.

Spatio-temporal variations and recruitment of Sargassum flavifolium Kützing in sublittoral cobble bottoms: relationships with environmental variables

Dynamics of Sargassum flavifolium Kutzing were studied in sublittoral cobble bottoms. The analyses showed that some morphological attributes (thallus length and number of branches, blades, stipes and receptacles) were related to selected environmental variables (depth, cobble size, temperature, wave exposure and day length), and spatio-temporal differences in selected variables (thallus length, reproductive capability, recruitment and number of thalli per cobble) were found. S. flavifolium showed an annual life cycle with marked variations in habit along the year and between locations. The longest thalli were found in May–July coinciding with annual increases in seawater temperature and day length, and the decrease in wave exposure. However, depth and cobble size were also variables that interacted with this seasonal pattern, and as a result, differences in Sargassum development could be observed within a site or at the same depth. The longest thalli were found at the deepest bottoms and on larger cobbles. The highest number of receptacles occurred on the largest individuals, and the greatest percentage of fertile thalli was observed in the deeper samples. Reproduction and recruitment were coupled, and recruits were conspicuous and more numerous in shallow cobbles. Significant differences in number of thalli per cobble were observed between months, although changes related to recruitment were only observed in small cobbles.

Storage, Cutting and Culture Conditions of Filamentous Roots of Hiziki Sargassum fusiforme

To develop an artificial seedling production method of Hiziki, Sargassum fusiforme, the effect of storage, cutting and culture conditions on the formation of erect stem from filamentous roots separated from holdfasts were examined. After the Hiziki harvest in end of April 2007, holdfasts remaining on cultivation ropes were collected, loosened to separate the filamentous roots and washed with the culture medium. Optimum storage irradiance of the filamentous roots, temperature and irradiance for erect stem formation and growth, and the width of cut filamentous roots were examined. Optimum temperature and irradiance to store filamentous roots were 12degC and 25micromol/square m/s at 12L:12D cycle. A temperature of 23degC and irradiances ranging 120-230micromol/square m/s at 12L:12D cycle were more suitable for erect stem formation and growth. Forty culture days after cutting, 85% of the filamentous roots formed erect stems and the mean total length of young thalli reached about 5mm. Filamentous roots cut finely to less than 2.5 mm width resulted in 3 times more erect stems than those cut to larger than 5mm. Above results suggest the possibility of artificial seedling production from cut filamentous roots.

Abiotic factors affecting the development of Ulva sp. (Ulvophyceae; Chlorophyta) in freshwater ecosystems

The influence of physicochemical factors on the development of Ulva species with distromatic tubular morphology was studied in three streams located in Poznan, Poland. The study evaluated key environmental factors that may influence the colonisation and growth of Ulva populations in freshwater systems. In total, nine environmental parameters were included: temperature, water depth, pH, oxygen (O2), ammonium (NH4 +), nitrate (NO3 −), phosphate (PO4 3−), sodium chloride (NaCl) and total iron (Fe). Morphometric features of thalli (length and width, percentage of furcated and young thalli) and surface area of free-floating mats formed by the freshwater populations of Ulva were compared at all sites. Principal components analysis indicated the most important factors influencing Ulva development were sodium chloride concentrations and water depth. Two other key chemical factors affecting the freshwater form of Ulva were phosphate and nitrite concentrations. High concentrations of sodium chloride inhibited the development of Ulva, leading to a lower number of thalli in the Ulva mats. At the sites with stable and deeper water, the surface area of the mats was larger. Both phosphate and nitrite concentrations were positively correlated with an increase in the number of thalli in the mats and the thalli length.

The role of buoyancy in mitigating reduced light in macroalgal aggregations

Many organisms live in aggregations. For marine organisms attached to the substratum, the presence of neighbors may reduce both the water flow and light encountered by an individual within a group. We used the marine macroalga Turbinaria ornata to investigate how water velocity and photon flux density were affected by aggregations under natural flow and light conditions in the field, and to explore how the ability to stand upright due to buoyancy impacted light interception by individuals in aggregations. We found that the flow experienced by thalli in the middle of a group in a backreef habitat was only about half the speed of the water flow they encountered after their neighbors were removed. This suggests that aggregated algae are subjected to lower hydrodynamic forces than are solitary thalli, but may also experience reduced rates of transport of dissolved nutrients and gases. Light sensors placed along the length of thalli positioned within and outside of clumps of T. ornata showed that the tops of buoyant upright thalli experienced similar light levels to solitary thalli, but that neighbors shaded the lower portions of thalli in aggregations. Individuals that were rendered non-buoyant (by filling their airbladders with water) could not support their own weight and those in aggregations experienced lower light at all points along their lengths than did upright buoyant individuals. Using in situ determinations of the rate of photosynthesis of T. ornata as a function of irradiance, we converted our field measurements of light interception to mg carbon fixed over the course of a day for whole fronds. Such estimates indicated that carbon fixation was higher for solitary buoyant and non-buoyant T. ornata than for buoyant individuals in aggregations, all of which were greater than for non-buoyant thalli in those clumps. Our results indicate that living in aggregations reduces the productivity of T. ornata, but this effect is mitigated by the buoyancy of thalli.

The effects of methionine and cobalt ions on sex expression and development of Anemia phyllitidis gametophytes

One of the prime precursor for ethylene synthesis — L-methionine and the inhibitor of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) — Co2+-were tested for their effects on sex expression and development of Anemia phyllitidis fern gametophytes. Five concentrations of both chemicals (0, 10, 25, 50, 100 µM) were analysed with reference to antheridia and archegonia formation, number and size of cells as well as thalli length using the three-zone model of gametophyte structure. Both substances, however at different concentrations, enhanced the number of GA3-induced antheridia and similarly stimulated the cell number and inhibited thalli length. Both of them at 100 µM concentrations without GA3 induced meristematic area formation while methionine also induced archegonia in the apical parts of gametophytes. These findings correspond with the previous observations concerning the important role of ethylene synthesis precursor (ACC) in controlling gibberellic acid-induced male sex expression in ferns and broaden the knowledge about the mechanisms of fern gametophyte development.

Artificial marine structures facilitate the spread of a non‐indigenous green alga, Codium fragile ssp. tomentosoides, in the north Adriatic Sea

Summary Artificial structures have become ubiquitous features of coastal landscapes. Although they provide novel habitats for the colonization of marine organisms, their role in facilitating biological invasions has been largely unexplored. We investigated the distribution and dynamics of the introduced green alga, Codium fragile ssp. tomentosoides, at a variety of spatial scales on breakwaters in the north Adriatic Sea, and analysed experimentally the mechanisms underlying its establishment. We assessed the provision of sheltered habitats by breakwaters, the role of disturbance (e.g. from recreational harvesting and storms) acting at different times of the year, and the interactions between Codium and the dominant native space‐occupier, the mussel Mytilus galloprovincialis. Codium fragile ssp. tomentosoides has established viable populations on artificial structures along the shores investigated. The density, cover and size (length, branching and weight) of annual erect thalli of Codium was enhanced in sheltered conditions, resulting in the monopolization of landward low‐shore habitats of breakwaters. On the landward sides of breakwaters, disturbance enhanced recruitment of Codium. The time when bare space was provided within mussels beds was crucial. Removal of mussels in April or January did not affect the recruitment of Codium, whereas harvest in August, shortly before Codium gamete release, doubled its success. On the seaward sides of breakwaters, the effects of disturbance were more complex because mussels both inhibited recruitment of Codium and provided shelter from wave action to adult thalli. Synthesis and applications. Artificial structures can provide suitable habitats for non‐indigenous marine species and function as corridors for their expansion. Physical (wave exposure) and biotic (resident assemblages) features of artificial habitats can be important determinants of their susceptibility to biological invasions. Alternative options in the design of artificial structures and effective management of native assemblages could minimize their role in biological invasions. In particular, increased water motion and retention of space by mussels in spring–summer would be effective in reducing the ability of C. fragile ssp. tomentosoides to persist on the breakwaters investigated in this study.

모자반(Sargassum fulvellum)의 생장, 성숙과 발생

Sargassum fulvellum (Turner) C. Agardh, an edible brown alga is farmed commercially by sexual reproduction and vegetative regeneration. Investigations were made on the phenology, abundance and maturity of reproductive structures in mature fronds, egg release and young germling development under different light conditions (20, 50, 80 and <TEX>$100{\mu}mol/m^2/s$</TEX>) and temperatures (5, 10, 15, 20 and <TEX>$25^{\circ}C$</TEX>). Monthly sampling was carried out by SCUBA diving at Chungsando on the southwestern coast of Korea from September 2002 to August 2003. The Maximum length of thalli was <TEX>$104.6{\pm}20.7{\cal}cm$</TEX> in March 2003 when the water temperature was <TEX>$9.0^{\circ}C$</TEX> and minimum was <TEX>$0.8{\pm}0.5{\cal}cm$</TEX> in June when the water temperature was <TEX>$19.5^{\circ}C$</TEX>. Receptacle formation was observed from February to April. The peak period of egg release for this alga was in April when the water temperature was about <TEX>$10^{\circ}C$</TEX> in nature. In the culture regimes of temperature and irradiance, the egg release of the excised female receptacle was highly affected by temperature. The maximum rate of egg release was <TEX>$96.7{\pm}5.8{\%}$</TEX> under <TEX>$20^{\circ}C$</TEX> and <TEX>$80{\mu}mol/m^2/s$</TEX>. The maximum length of young germlings was <TEX>$3.9{\pm}0.2{\cal}mm$</TEX> after 35 days culture under <TEX>$15^{\circ}C$</TEX> and <TEX>$80{\mu}mol/m^2/s$</TEX>.