• ALGAE
• /
• v.36 no.2
• /
• pp.147-154
• /
• 2021

Kelp life history pathways alternate between macroscopic sporophytes that produce spores and microscopic gametophytes that produce gametes. Occasionally, an alternative pathway is seen. This study examined the circumstances by which the high latitude estuarine bull kelp, Nereocystis luetkeana, foregoes the "free-living microscopic stages by releasing embryonic sporophytes directly from sori. Sori were collected from adult N. luetkeana sporophytes from eight locations within Kachemak Bay, Alaska in 2018 and 2020 to examine spatial and temporal development of embryonic sporophytes on sori. Distinctions were made between sori collected from first-generation and overwintered adults to assess the influence of parental age on embryonic sporophyte release. Further distinctions were made between sori collected from attached and drifting individuals to assess the influence of the status of parental attachment to substrate on embryonic sporophyte release. Inspection of propagules released from sori after 48-h incubations indicated that embryonic sporophytes were occasionally released alongside viable spores. Though embryonic sporophytes were released from sori as early as spring, it was not evident that they were bound by seasonal or spatial limits. The percent of propagules that were embryonic sporophytes ranged from 0% to 100% but were not significantly different between first-generation and overwintered adults, nor were they different between attached and drifting individuals. Nevertheless, the characteristic of directly releasing embryonic sporophytes from adult sporophytes might have ecological advantages for N. luetkeana.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.49 no.5
• /
• pp.689-693
• /
• 2016

Sargassum golden tides occurred in Shinan-gun and Jeju Island, Korea, between January and May 2015. In Shinangun, 5,180 tons of Sargassum were removed from 3,339 ha of coastline, while 20,000 tons were removed from Jeju Island. The huge floating masses of seaweed caused damage to fisheries in Shinan-gun including abalone sea cage, Pyropia and Saccharina farms off the southwest coast of Korea. Drifting Sargassum also washed ashore on Jeju Island. The species of Sargassum in these golden tides was identified as S. horneri (Turner) C. Agardh, based on morphology and molecular data, and it appears to have originated from the East China Sea. This is the first report on Sargassum golden tides causing damage to fisheries in Korea.

• Journal of Marine Life Science
• /
• v.9 no.1
• /
• pp.47-52
• /
• 2024

Light is a major external environmental factor that influences the circadian rhythm of photosynthetic organisms and various physiological phenomena, such as growth, maturation, and behavior. The number of light-reaching organisms changes depending on the season and atmospheric conditions, and the intensity and wavelength of light differ depending on the organisms inhabiting the environment. Altered light changes the circadian rhythm of fish, which is controlled by clock genes, such as period 2 (Per2), cryptochrome 1 (Cry1), and melatonin. In this study, we set the zeitgeber time (ZT; 14 light-10 dark, LD) based on the actual sunrise and sunset times and examined Per2 and Cry1 activities, levels of aralkylamine N-acetyltransferase (AANAT), and melatonin in Pholis nebulosa, a drifting seaweed species exposed to irregular light. Per2 and Cry1 levels increased during the daytime and decreased after sunset. The AANAT levels decreased during the daytime and increased during the night. Melatonin concentration was highest around midnight (ZT21, 23:30), but exhibited similar concentrations during the daytime. While the activity of Per2, Cry1, and AANAT levels exhibited a typical circadian rhythm observed in most vertebrates, melatonin concentrations did not show a significant difference between the daytime and nighttime. These findings provide insights into the circadian rhythm patterns of organisms exposed to irregular light environments, such as P. nebulosa, which differ from those of typical fish species.

• ALGAE
• /
• v.34 no.4
• /
• pp.315-326
• /
• 2019

Northeastward drifts of massive Sargassum patches were observed in the East China Sea (ECS) and Yellow Sea (YS) by the Geostationary Ocean Color Imager (GOCI) in May 2017. Coverage of the brown macroalgae patches was the largest ever recorded in the ECS and YS. Three-dimensional circulation modeling and Lagrangian particle tracking simulations were conducted to reproduce drifting trajectories of the macroalgae patches. The trajectories of the macroalgae patches were controlled by winds as well as surface currents. A windage (leeway) factor of 1% was chosen based on sensitivity simulations. Southerly winds in May 2017 contributed to farther northward intrusion of the brown macroalgae into the YS. Although satellite observation and numerical modeling have their own limitations and associated uncertainties, the two methods can be combined to find the best estimate of Sargassum patch trajectories. When satellites were unable to capture all patches because of clouds and sea fog in the ECS and YS, the Lagrangian particle tracking model helped to track and restore the missing patches in satellite images. This study suggests that satellite monitoring and numerical modeling are complementary to ensure accurate tracking of macroalgae patches in the ECS and YS.

• ALGAE
• /
• v.22 no.1
• /
• pp.17-21
• /
• 2007

Sargassum filicinum Harvey, a brown alga (Phaeophyceae) native to Northeastern Asia, has been recently reported from the coast of Southern California (USA). Here we report the occurrence and range extension of this introduced species, as we found the alga at La Jolla and Rancho Packard in Todos Santos Bay, Baja California, Mexico. The first collections of S. filicinum correspond to several immature plants, found on September 8, 2005, drifting in the intertidal zone at La Jolla. Later on November 9, 2006, we found a well-established population in Rancho Packard in the middle intertidal zone to 2 m depth. Since S. filicinum is an annual monoecious species with air bladders, the risk there is a high risk of spreading rapidly along the Pacific, as in the case for S. muticum. The population in Rancho Packard extends 500 m along the coast, consisting mainly of young plants with an average length of 30 cm and a density of 5 thallus/m2. This is the first record of this invasive species for the Mexican Pacific coast, and it represents the southern limit along the Pacific coast of North America. This finding suggests that this invasive species has successfully colonized the Pacific coast of North America and its distributional range is still expanding.

• Korean Journal of Ichthyology
• /
• v.19 no.4
• /
• pp.360-364
• /
• 2007

A single female specimen (73.6 mm SL) of ghost pipefish, Solenostomus cyanopterus Bleeker, belonging to the family Solenostomidae (new Korean name: Yu-ryeong-sil-go-gi-gwa), was observed and collected in the water off Yeongdeck, East Sea of Korea. Unlike to syngnathids, solenostomids are characterized by having the brood pouch formed by pelvic fins in female and dorsal fin spines present. This species is characterized by having the deep snout, and short, deep caudal peduncle, but no cirri and striped markings. In the water, the species swims slowly head downward in pairs and looks like a drifting pieces of algae or fallen leaf. We describe this species as new to Korean fish fauna and propose its new Korean name, "Yu-ryeong-sil-go-gi".