In recent years, macroalgal bloom occurs frequently in coastal oceans worldwide. It might be attributed to accelerating climate change. “Green tide” events caused by proliferation of green macroalgae (Ulva spp.) not only damage the local economy, but also harm coastal environments. These nuisance events have become common across several coastal regions of continents. In Korea, green tide incidences are readily seen throughout the year along the coastlines of Jeju Island, particularly the northeastern coast, since the 2000s. Ulva species are notorious to be difficult for morphology-based species identification due to their high degrees of phenotypic plasticity. In this study, to investigate temporal variation in Ulva community structure on Jeju Island between 2015 and 2020, chloroplast barcode tuf A gene was sequenced and phylogenetically analyzed for 152 specimens from 24 sites. We found that Ulva ohnoi and Ulva pertusa known to be originated from subtropical regions were the most predominant all year round, suggesting that these two species contributed the most to local green tides in this region. While U. pertusa was relatively stable in frequency during 2015 to 2020, U. ohnoi increased 16% in frequency in 2020 (36.84%), which might be associated with rising sea surface temperature from which U. ohnoi could benefit. Two species (Ulva flexuosa, Ulva procera) of origins of Europe should be continuously monitored. The findings of this study provide valuable information and molecular genetic data of genus Ulva occurring in southern coasts of Korea, which will help mitigate negative influences of green tide events on Korea coast.

양손 동시 동작 수행에서 어느 한 손에만 시간적 구조를 변화시킬 때 피아노 전공자와 비전공자의 두 손 각각에 어떠한 상호작용적 제어 특성이 나타나는지를 규명하기 위하여 본 연구를 수행하였다. 피아노 전공자와 비전공자 각 20명씩을 대상으로 하여 실시된 실험은 시간적 구조 변화를 요구하지 않는 통제조건과 한 쪽 손의 시간 구조 변화 처치 조건하에서 피험자들에게 양손 인지를 이용하여 5회의 탭핑과제를 동시 수행하게 하여 시간적 변화를 분석하였다. 그 결과, 변화가 요구되지 않은 손의 조건(500msec)에서 피아노 전공자는 요구시간과 거의 동일한 시간으로 수행한 반면, 비전공자는 주동 손(오른손) 24.82%, 비주동 손(왼손) 27.23%가 요구시간에 비해 실제 수행시간이 더 느려짐을 보였다. 변화가 요구된 손의 조건(250msec)에서 역시 피아노 전공자는 요구시간에 거의 근접한 시간의 수행을 하였으나, 비전공자는 주동 손 34.69%, 비주동 손 31.75%가 요구시간에 비해 실제 수행시간이 증가하였다. 이러한 결과는, 두 손에 시간적 구조를 달리하여 동시에 수행할 때 피아노 비전공자는 양손 모두에 간섭이 일어나 일관되게 수행시간이 느려짐을 보여주는 것이며, 이는 어느 한 손이 다른 손의 시간적 구조에 동화되는 것과는 다르다. 또한 피아노 전공자는 각각의 손에 서로 다른 시간적 구조에도 불구하고 요구시간에 매우 일치하는 수행을 보였다. 이는 피아노 전공자들에게는 다년간의 연습을 통하여 익힌 자동운동조절프로그램이 작동하기 때문이라 할 수 있다. 하지만 피아노 학습이 되지 않은 일반인들은 이러한 프로그램이 생성, 내재되어 있지 않으므로 오류 수행과 함께 결속이 일어남으로써 독립적 협응이 이루어지지 않음을 극명하게 보여주었다.

The purpose of this study was to find the effect of the two different types of movement velocity control on timing variability and temporal structure parameters (time to peak positive acceleration, duration of positive acceleration, peak positive acceleration) of acceleration-time function. Subjects were 6 male students, and task was arm flexion movement. The results showed that when movement distance increased with movement time fixed, timing variability was constant, also time to peak positive acceleration and duration of positive acceleration were constant, but peak positive acceleration increased with statistical significance. And when movement time increased with movement distance fixed, timing variability increased, and time to peak positive acceleration, duration of positive acceleration increased, but peak positive acceleration decreased. The results suggest that each control types of movement velocity are different fundamentally, and movement velocity as a function of movement distance is achieved by the increase of peak positive acceleration with time to positive acceleration and duration of positive acceleration constant. Namely, this type of velocity is modulated by the change of force with phasing of generalized motor program, and movement velocity as a function of movement time is achieved by the extension of time to peak positive acceleration and duration of positive acceleration, Thus, this type of movement velocity is modulated by the change of phasing and relative force generalized motor program.