Convolution Neural Network for the Prediction of <i>Cochlodinium polykrikoides</i> Bloom in the South Sea of Korea

In this study, the occurrence of Cochlodinium polykrikoides bloom was predicted based on spatial information. The South Sea of Korea (SSK), where C. polykrikoides bloom occurs every year, was divided into three concentrated areas. For each domain, the optimal model configuration was determined by designing a verification experiment with 1–3 convolutional neural network (CNN) layers and 50–300 training times. Finally, we predicted the occurrence of C. polykrikoides bloom based on 3 CNN layers and 300 training times that showed the best results. The experimental results for the three areas showed that the average pixel accuracy was 96.22%, mean accuracy was 91.55%, mean IU was 81.5%, and frequency weighted IU was 84.57%, all of which showed above 80% prediction accuracy, indicating the achievement of appropriate performance. Our results show that the occurrence of C. polykrikoides bloom can be derived from atmosphere and ocean forecast information

Convolution Neural Network for the Prediction of Cochlodinium polykrikoides Bloom in the South Sea of Korea

In this study, the occurrence of Cochlodinium polykrikoides bloom was predicted based on spatial information. The South Sea of Korea (SSK), where C. polykrikoides bloom occurs every year, was divided into three concentrated areas. For each domain, the optimal model configuration was determined by designing a verification experiment with 1&ndash;3 convolutional neural network (CNN) layers and 50&ndash;300 training times. Finally, we predicted the occurrence of C. polykrikoides bloom based on 3 CNN layers and 300 training times that showed the best results. The experimental results for the three areas showed that the average pixel accuracy was 96.22%, mean accuracy was 91.55%, mean IU was 81.5%, and frequency weighted IU was 84.57%, all of which showed above 80% prediction accuracy, indicating the achievement of appropriate performance. Our results show that the occurrence of C. polykrikoides bloom can be derived from atmosphere and ocean forecast information

Comparison of Distribution and Density of Nemopilema nomurai by Water Columns Using Echo Counting and Echo Integration Methods

In this study, the distribution of Nemopilema nomurai in the waters of Mijo-myeon, Namhae and Gijang-gun, Busan was analyzed; furthermore, echo counting and echo integration methods were used to compare the distribution density. The acoustic system used in the study was a split beam scientific echosounder operating at 38 and 120 kHz (EK-60, Simrad, Norway). Echo counting and echo integration methods were used to determine the density of N. nomurai distributed in the survey areas. The distribution of N. nomurai by water columns, estimated using an echo counting method, was concentrated at approximately 10 m deep in the waters of Mijo, Namhae and 10&ndash;50 m deep in the waters of Gijang, Busan; moreover, the distributed depth varied by the surveyed date and time. It was shown that analyzing the acoustic scattering strength of jellyfish obtained from the echo counting method would be more effective for distributional survey of N. nomurai with two frequency system

Economic impact, management and mitigation of red tides in Korea

Over the past three decades, a total of USD $121 million in economic losses (fish/shellfish kills) has occurred in the Korean aquaculture industry due to harmful algal blooms (HABs). Paralytic shellfish poisoning (PSP) has also been noted almost every year, closing shellfish farms, and 46 people were poisoned including five people killed by consuming wild mussels. Since 1980, PSP has been officially monitored and managed, and the nationwide control of fish/shellfish kills by HAB species began in 1995. Management and control strategies include both precautionary and emergency measures. Precautionary management includes establishing an observation network and prediction system, an early warning system, and mitigating damage to aquafarms. Along with regular HAB monitoring including species, chlorophyll a, and associated water quality and meteorological parameters, automatic HAB alarm systems equipped with chlorophyll a and turbidity sensors are used in aquafarms as early HAB warnings. Emergency management is essential after a HAB outbreak to prevent fisheries damage. This method includes supplying oxygen to fish, stopping feeding, transferring fish to a safe area, and clay dispersal. Clay dispersion is the prime mitigation technique for HABs in Korea, because clay is natural, nontoxic, inexpensive, and easy to use in field operations. Clay is dispersed over the sea surface using a clay dispensing device to efficiently remove HABs. A third generation (3G) clay dispenser has been developed recently, combining an electrolytic water generator and a clay dispenser, significantly reducing the amount of clay used, resulting in high removal efficiencies. Since using this device, the economic losses from HAB fish kills have dropped &gt;80% in Korea, although the frequency of HABs has increased since 1980. Clay is a natural component, but using too much clay may cause negative impacts on marine organisms and environments. In addition, clay dispersal is not an effective method to control poisoning of fish/shellfish from algal toxins that accumulate in fish and shellfish at low density toxic blooms. Future studies of HAB control should include control of HABs using minimum amounts of clay and practical use of biological control agents. (C) 2013 Elsevier B.V. All rights reserved.N

A Study on the Possibility of Early Warning for <i>Cochlodinium polykrikoides</i> Blooms, Using Molecular Methods

The occurrence of HABs is known to be affected by multiple environmental factors such as temperature, salinity, nutrients, light, water chemistry, and biological activity. This study aimed to study the possibility of early warning for Cochlodinium polykrikoides blooms in southern Korean waters using qPCR and metabarcoding analysis. We were able to detect C. polykrikoides via a sensitive technique, and confirmed the early warning potential of C. polykrikoides by quantitative PCR. To identify the microbial organisms related to the bloom caused by C. polykrikoides, metabarcoding analysis was conducted using 18 water samples collected from bloom sites in southern Korean waters between 2018 and 2019. Although there was no single group that could explain the successive blooms of C. polykrikoides, four taxa, including Gamma proteobacteria (0.588, p p p C. polykrikoides blooms. When the HABs that occurred were caused by C. polykrikoides, although there were sites where the cells of C. polykrikoides were not detected, similar functions of the microbial communities operated in all southern Korean coastal waters. We identified that the phytoplankton community structure was divided into three or four, using metabarcoding analysis by sampling years

Prorocentrum shikokuense Hada and P. donghaiense Lu are junior synonyms of P. obtusidens Schiller, but not of P. dentatum Stein (Prorocentrales, Dinophyceae)

In Japanese, Chinese and Korean coastal waters, recurrent blooms of a small, elongate Prorocentrum species have been observed in recent years. In previous studies, this species has been respectively identified as P. shikokuense, P. donghaiense and P. dentatum, despite morphological similarity and identical rDNA sequences. To resolve the confusion, morphological features, including the architectural details of the periflagellar area, were examined and ribosomal DNA (rDNA) sequences were obtained from specimens collected from the East China Sea and Korean coast, and a strain established in the waters off the Canary Islands of Spain. In addition, the descriptions of the three species and allied species were reviewed. Morphological observations and a phylogeny based on the SSU, ITS region and LSU rDNA sequences revealed that the previously confused species and our studied strains are conspecific and that the morphology of strains identified as P. dentatum in the phylogenetic trees does not coincide with P. dentatum sensu stricto. The confusion can be traced back to Dodge (1975, p. 116), who considered P. veloi, P. monacense and P. obtusidens as junior heterotypic synonyms of P. dentatum. However, Dodge’s P. dentatum are closer to P. obtusidens sensu stricto, rather than P. dentatum sensu stricto. P. obtusidens sensu stricto can be distinguished from P. dentatum sensu stricto by its relatively small size, parallel sides towards the anterior and a blunt anterior extension on one side. This indicates that P. obtusidens should not be considered a synonym of P. dentatum sensu stricto. In addition, a comparison of the original descriptions of P. obtusidens and allied species allowed to conclude that small, elongate Prorocentrum from Japanese, Chinese and Korean coastal waters previously identified as P. shikokuense, P. donghaiense, P. dentatum sensu Yoo and Lee (1986) and the specimens studied herein, which share identical rDNA sequences, morphologically coincide with P. obtusidens. Therefore, it is proposed that P. shikokuense and P. donghaiense should be regarded as junior synonyms of P. obtusidens

Anthropogenic nitrogen is changing the East China and Yellow seas from being N deficient to being P deficient

Addition of the increased anthropogenic nitrogen (NOx and NHy) emitted from northeast Asian countries to the Yellow and East China seas and coastal waters around Korea has resulted in an unparalleled increase in the nitrate (N) concentration relative to the phosphate (P) and silicate (Si) concentrations in the upper ocean. We found that for the Yellow Sea the increase in N over P was largely explained by increased atmospheric nitrogen deposition, whereas for the northern East China Sea, downstream of the Changjiang River plume, the trend in N increase relative to P was more associated with a change in the combined input of nutrients from atmospheric deposition and riverine discharges. In contrast, the dynamics of the N to P relationship in the southern East China Sea was largely controlled by a change in the intrusion intensity of the Kuroshio Current, which has a low N : P ratio. The disproportionate and persistent input of nutrients to the marine waters of this region over the past four decades has transformed extensive areas from being N deficient to being P deficient, and has concurrently decreased the concentration of Si relative to N. In coastal waters around Korea in particular, these shifts in the nutrient regime have been accompanied by a change from diatom-dominated to dinoflagellate-dominated blooms. Given the complexity of coastal ecosystems, the associations between changes in nutrient regimes and biological changes need to be investigated in other coastal areas receiving increasing loads of anthropogenic nitrogen. © 2020 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.11Nsciescopu

Anthropogenic nitrogen is changing the East China and Yellow seas from being N deficient to being P deficient

Addition of the increased anthropogenic nitrogen (NOx and NHy) emitted from northeast Asian countries to the Yellow and East China seas and coastal waters around Korea has resulted in an unparalleled increase in the nitrate (N) concentration relative to the phosphate (P) and silicate (Si) concentrations in the upper ocean. We found that for the Yellow Sea the increase in N over P was largely explained by increased atmospheric nitrogen deposition, whereas for the northern East China Sea, downstream of the Changjiang River plume, the trend in N increase relative to P was more associated with a change in the combined input of nutrients from atmospheric deposition and riverine discharges. In contrast, the dynamics of the N to P relationship in the southern East China Sea was largely controlled by a change in the intrusion intensity of the Kuroshio Current, which has a low N : P ratio. The disproportionate and persistent input of nutrients to the marine waters of this region over the past four decades has transformed extensive areas from being N deficient to being P deficient, and has concurrently decreased the concentration of Si relative to N. In coastal waters around Korea in particular, these shifts in the nutrient regime have been accompanied by a change from diatom-dominated to dinoflagellate-dominated blooms. Given the complexity of coastal ecosystems, the associations between changes in nutrient regimes and biological changes need to be investigated in other coastal areas receiving increasing loads of anthropogenic nitrogen. © 2020 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.11Nsciescopu