Red Tide Species Research Articles

A novel algicidal properties of fermentation products from Pseudomonas sp. Ps3 strain on the toxic red tide dinoflagellate species.

The viability of both China's offshore fishing operations and the global marine fishing industry is threatened by the occurrence of red tides caused by Gymnodinium catenatum and Karenia mikimotoi. Effective control of these dinoflagellate-mediated red tides has become a pressing issue that requires immediate attention. In this study, High-efficiency marine alginolytic bacteria were isolated and underwent molecular biological identification to confirm their algicidal properties. Based on a combination of morphological, physiological, biochemical, and sequencing results, Strain Ps3 was identified as belonging to the species Pseudomonas sp. We examine the effects of algicidal bacteria on the red tide species G. catenatum and K. mikimotoi within an indoor experimental setting. Then gas chromatography- mass spectrometry (GC-MS) was used to analyze the structure of the algolytic active substances. This investigation demonstrated that with exposure to the algae-lysis experiment, the Ps3 strain has the best algae-lysis effect, with G. catenatum and K. mikimotoi reaching 83.0 and 78.3%. Our results from the sterile fermentation broth experiment showed that the inhibitory effect on the two red tide algae was positively correlated with the concentration of the treatment. At a treatment concentration of 2.0% (v/v), the 48 h lysis rates of G. catenatum and K. mikimotoi due to exposure to the Ps3 bacterial fermentation broth were 95.2 and 86.7%, respectively. The results of this study suggest that the algaecide may be a rapid and effective method to control dinoflagellate blooms, as evidenced by the observed changes in cellular morphology in all cases. In the ethyl acetate phase of Ps3 fermentation broth, the cyclic (leucine-leucine) dipeptide was the most abundant. The findings of this study contribute to our understanding of red tide prevention and control and provide a theoretical foundation for further research in this field.

Effects of typical marine environmental factors on the bioluminescence intensity of individual Noctiluca scintillans.

Red Noctiluca scintillans (RNS) is one of the major red tide species and dominant bioluminescent plankton in the global offshore. Bioluminescence offers a number of applications for ocean environment assessments such as interval waves study, fish stocks evaluation and underwater target detection making it of significant interest in forecasting bioluminescence occurrence and intensity. RNS is susceptible to changes in marine environmental factors. However, the effects of marine environmental factors on the bioluminescent intensity (BLI, photon s-1) of individual RNS cells (IRNSC) is poorly known. In this study, the effects of temperature, salinity and nutrients on the BLI were studied by field and laboratory culture experiments. In the field experiments, bulk BLI was measured by an underwater bioluminescence assessment tool at various temperature, salinity and nutrient concentrations. To exclude the contribution by other bioluminescent planktons, an identification method of IRNSC was first developed using the features of the bioluminescence flash kinetics (BFK) curve of RNS to identify and extract BLI emitted by an individual RNS cell. To decouple the effects of each environmental factor, laboratory culture experiments were conducted to examine the effects of a single factor on the BLI of IRNSC. The field experiments showed that BLI of IRNSC negatively correlated with temperature (3-27°C) and salinity (30-35‰). The logarithmic BLI can be well fitted using a linear equation with temperature or salinity with Pearson correlation coefficients of -0.95 and -0.80, respectively. The fitting function with salinity was verified by the laboratory culture experiment. On the other hand, no significant correlation was observed between BLI of IRNSC and nutrients. These relationships could be used in the RNS bioluminescence prediction model to improve the prediction accuracy of bioluminescent intensity and spatial distribution.

MODIS-derived green Noctiluca blooms in the upper Gulf of Thailand: Algorithm development and seasonal variation mapping

In recent decades, red tides of non-toxic harmful algal blooms have frequently occurred in monsoon-influenced tropical areas, particularly the green form of Noctiluca scintillans (hereafter green Noctiluca). However, our understanding of the mechanism of red tide formation is hindered by spatial and temporal constraints of field data. In this study, we used moderate resolution imaging spectroradiometer (MODIS) ocean color data along with a locally developed algal-bloom classification algorithm to investigate the seasonal variability of dominant red tides across the upper Gulf of Thailand (uGoT). During our July 2018 observation, a super green Noctiluca bloom with extraordinarily high chl-a (>1,469 mg m-3) displayed a distinct spectral reflectance characteristic among red tides in blue-to-green and red-to-near infrared wavelengths. According to the distinctive in situ hyperspectral characteristics of uGoT algal blooms, we developed a classification algorithm for MODIS normalized at 488, 531, and 667 nm, which successfully discriminated green Noctiluca in three levels of blooms, namely, super (100%), strong (>80%), and weak (>40%), from other algal blooms (i.e., dinoflagellates, diatoms, cyanobacteria, and mixed red tide species) as well as non-bloom oceanic and coastal waters using MODIS data, as confirmed by uGoT red tide reports. Monthly MODIS-based discrimination composites from 2003 to 2021 revealed seasonal variability in the surface distribution and bloom frequency of green Noctiluca and other red tides according to the Asian monsoon seasons: the southwest monsoon (May–September) and the northeast monsoon (October–January of the following year). Green Noctiluca blooms occurred farther from the shore and estuaries than other red tides (dinoflagellates and cyanobacteria), and were much more frequent than other red tides between the Tha Chin and Chao Phraya River mouths during the non-monsoon period (February to April). The frequency and distribution of green Noctiluca blooms, as well as other algal blooms, varied with the monsoon season. By comparing MODIS-derived algal blooms to monsoon-induced factors (i.e., sea surface winds, precipitation, and river discharge), we present an unprecedented overview of the spatial and temporal dynamics of red tides throughout the uGoT under Asian monsoon conditions. This research contributes to our understanding of the impact of climate change on phytoplankton dynamics.

Establishment and preliminary study of electrophysiological techniques in a typical red tide species

Electrophysiology studies the electrical properties of cells and tissues including bioelectrical signals and membrane ion channel activities. As an important means to reveal ion channel related physiological functions and the underlying mechanisms, electrophysiological techniques have been widely used in studies of animals, higher plants and algae that are closely related to higher plants. However, few electrophysiological studies have been carried out in red tide organisms, especially in dinoflagellates, which is mainly due to the complex surface structure of dinoflagellate amphiesma. In this study, the surface amphiesma of Alexandrium pacificum, a typical red tide species, was removed by centrifugation, low-temperature treatment and enzymatic treatment. In all three treatments, low-temperature treatment with 4 °C for 2 h had high ecdysis rate and high fixation rate, and the treated cells were easy to puncture, so low-temperature treatment was used as a preprocessing treatment for subsequent current recording. Acquired protoplasts of A. pacificum were identified by calcofluor fluorescence and immobilized by poly-lysine. A modified “puncture” single-electrode voltage-clamp recording was first applied to dinoflagellates, and voltage-gated currents, which had the characteristics of outward K+ current and inward Cl− current, were recorded and confirmed by ion replacement, indicating the voltage-gated currents were mixed. This method can be used as a technical basis for the electrophysiological study of dinoflagellates and provides a new perspective for the study of stress tolerance, red tide succession, and the regulation of physiological function of dinoflagellates.

Antagonistic and synergistic effects of warming and microplastics on microalgae: Case study of the red tide species Prorocentrum donghaiense

Bibliometric network analysis has revealed that the widespread distribution of microplastics (MPs) has detrimental effects on marine organisms; however, the combined effects of MPs and climate change (e.g., warming) is not well understood. In this study, Prorocentrum donghaiense, a typical red tide species in the East China Sea, was exposed to different MP concentrations (0, 1, 5, and 10 mg L−1) and temperatures (16, 22, and 28 °C) for 7 days to investigate the combined effects of MPs and simulated ocean warming by measuring different physiological parameters, such as cell growth, pigment contents (chlorophyll a and carotenoid), relative electron transfer rate (rETR), reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA), and adenosine triphosphate (ATP). The results demonstrated that MPs significantly decreased cell growth, pigment contents, and rETRmax, but increased the MDA, ROS, and SOD levels for all MP treatments at low temperature (16 °C). However, high temperatures (22 and 28 °C) increased the pigment contents and rETRmax, but decreased the SOD and MDA levels. Positive and negative effects of high temperatures (22 or 28 °C) were observed at low (1 and 5 mg L−1) and high MP (10 mg L−1) concentrations, respectively, indicating the antagonistic and synergistic effects of combined warming and MP pollution. These results imply that the effects of MPs on microalgae will likely not be substantial in future warming scenarios if MP concentrations are controlled at a certain level. These findings expand the current knowledge of microalgae in response to increasing MP pollution in future warming scenarios.

Establishment and Preliminary Study of Electrophysiological Techniques in a Typical Red Tide Species

Establishment and Preliminary Study of Electrophysiological Techniques in a Typical Red Tide Species

Long-term changes in red tide outbreaks in Xiamen Bay in China from 1986 to 2017

Data on red tide (harmful algae blooms, HABs) from 1986 to 2017 in Xiamen Bay of Fujian province in China was collected. In these 30 years, a total of 53 red tide events were recorded, which mostly happened in West sea (47.3%) and Tong'an Bay (40.5%). And, red tide areas in Xiamen Bay have expanded, with the most prone area changing from West sea to Tong'an Bay. Furthermore, red tide focused on late spring and summer, including the months of May, June and July, with the percentage of occurrence of 13.8%, 26.2% and 27.7%, respectively. By contrast, red tide seldom occurred in autumn. Skeletonema costatum, Chaetoceros curvisetus and Akashiwo sanguinea were dominant red tide species in the bay responsible for red tide events on 24, 8 and 6 occasions so far, respectively. Red tide events caused by Dinoflagellates have been increasing in these 30 years. While red tide events caused by Diatom decreased in 2010s obviously compared to those in 2000s. It was suggested that changes of eutrophication degree and nutrient ratios, climate change, and sediment property maybe important factors to the long-term changes in red tide outbreaks in Xiamen Bay.

Quantification of Margalefidinium polykrikoides Blooms along the South Coast of Korea Using Airborne Hyperspectral Imagery

The red tide bloom-forming dinoflagellate Margalefidinium polykrikoides is well known for its harmful effects on marine organisms, and for killing fish in aquaculture cages via gill clogging at a high cell abundance. To minimize the damage caused by red tide blooms, it is essential to understand their detailed spatial distribution with high accuracy. Airborne hyperspectral imagery (HSI) is useful for quantifying red tide cell abundance because it provides substantial information on optical features related to red tide species. However, because published red tide indexes were developed for multichannel ocean color sensors, there are some limitations to applying them directly to HSI. In this study, we propose a new index for quantifying M. polykrikoides blooms along the south coast of Korea and generate a M. polykrikoides cell abundance map using HSI. A new index for estimating cell abundance was proposed using the pairs of M. polykrikoides cell abundances and in situ spectra. After optimization of the published red tide indexes and band correlation analyses, the green-to-fluorescence ratio (GFR) index was proposed based on red tide spectral characteristics. The GFR index was computed from the green (524 and 583 nm) and fluorescence wavelength bands (666 and 698 nm) and converted into red tide cell abundance using a second-order polynomial regression model. The newly proposed GFR index showed the best performance, with a coefficient of determination (R2) of 0.52, root mean squared error (RMSE) of 877.98 cells mL−1, and mean bias error (MBE) of −18.42 cells mL−1, when applied to atmospherically corrected HSI. The M. polykrikoides cell abundance map generated from the GFR index provides precise spatial distribution information and allowed us to estimate a wide range of cell abundance up to 5000 cells mL−1. This study indicates the potential of the GFR index for quantifying M. polykrikoides cell abundance from HSI with a reasonably high level of accuracy.

Red tide dataset in the waters around the Korean Peninsula

Red tide blooms are increasing worldwide. Since 1995, Margalefidium polykrikoides blooms have occurred frequently in the waters around the Korean Peninsula. These blooms generally appear first on the South Sea of Korea in summer. When they occur on a large scale, they extend to the East Sea of Korea and the West Sea of Korea, causing great damage to fisheries and marine ecosystems. Harmless red tide can also adversely affect the environment of the waters by causing oxygen depletion in waters when occurring at high density. Currently, the National Institute of Fisheries Science (NIFS) is providing the daily red tide report based on M. polykrikoides red tide species. This report contains red tide species, location, and cell abundance information, but is limited to use as cell abundance data based on exact location. In addition, the waters around the Korean peninsula have different characteristics, so that the optical characteristics and seawater environment are different for each water. In the East Sea in Aug. 2013, the West Sea in Aug. 2016, the South Sea in Aug. 2018, and the South Sea in Aug. and Sep. 2019, during red tide season, dataset were obtained for red tide cell abundance, spectrum, chlorophyll concentration, and suspended particulate matter concentration. Noctiluca scintillans species were observed in the field survey conducted in 2016, and M. polykrikoides was mainly found in the other field surveys. Location-based red tide cell abundance data and seawater environment information obtained during red tide occurrence will be useful data for the construction of red tide warning system to reduce damage due to red tide blooms.

Red tide detection using deep learning and high-spatial resolution optical satellite imagery

ABSTRACT Red tide is one of the most devastating phenomena that have impacted coastal environments and fishery on a local scale in the worldwide seas. Satellite imagery can provide a synoptic view of the red tides over the wide region. Previous methods to detect the red tides have not sufficiently performed and revealed limitations in the study region. This study developed a red tide detection scheme based on the deep-learning method by using Landsat-8 OLI data during unprecedented explosive red tide events in the southern coastal region of the Korean Peninsula in 2013. To develop and validate the red tide detection of this study, we conducted cruise campaigns to obtain in-situ water sampling for red tide species and its density, chlorophyll-a concentration, suspended particulate matter (SPM), and spectrum data of red tides as a target object and other reference data using a spectroradiometer in the coastal regions from 2013 to 2015. The seawater shows different spectral shape by its components such as red tide, chlorophyll-a concentration, and SPM. Spectral characteristics of the red tides demonstrated bimodal peaks over visible wavelengths regardless of the species of the red tide. Considering such spectral characteristics, the red tide detection algorithm was constructed by the deep-learning method with Landsat-8 OLI level-2 reflectance values and in-situ red tide observations. The validation results of the algorithm as compared with the map of in-situ red tide measurements showed a high probability of detection values greater than 0.7. These works have made it possible to monitor the red tides with high-spatial resolution satellite data and provide a tool to minimize a lot of socioecological impacts from red tide.

Diatom red tide significantly drive the changes of microbiome in mariculture ecosystem

Some diatom species cause red tides under eutrophic conditions, but little is known about their impact on the ecological structure of coastal systems. In this study, the effects of diatom red tides on the bacterial and eukaryotic communities in aquaculture systems were analyzed using high-throughput sequencing. The correlation between these communities and environmental factors was also analyzed. Principal coordinate analysis (PCoA) and non-metric multidimensional scaling (NMDS) showed that there were significant differences in the microbiome in red tide ponds and normal ponds (p < .05). The dominant bacterial taxa in red tide and normal ponds were Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, Verrucomicrobia and Planctomycetes. There were significant differences in the abundance of bacteria genera, such as Planctomyces, Marivita, Synechococcus and Marinobacterium, in red tide ponds and normal ponds (p < .05). Functional predictions showed that red tides affect carbon, nitrogen, sulfur and phosphorus metabolism in ponds. There were significant differences in the dominant eukaryotic genera in red tide ponds and normal ponds (p < .05). Red tide ponds were dominated by Skeletonema, Thalassiosira, and Cyclotella, while Ostreococcus, Hemiselmis, Glycine, and Cryothecomonas were dominant in normal ponds. Canonical correlation analysis (CCA) indicated that pH, DO salinity, nitrate, nitrite, ammonium and phosphate were significantly correlated with microbiomes in red tide and normal ponds. OTU (operational taxonomic unit) network analysis results showed that the dominant OTUs of Thalassiosira and Skeletonema were negatively correlated with most of the dominant OTUs of Proteobacteria, Actinobacteria, Bacteroidetes and Cyanobacteria. The importance of biotic interactions when investigating the link between the microbiome and red tide species has also been highlighted. This study revealed the important influence of a diatom red tides on bacterial and eukaryotic communities, and provided new insights into the impact of diatom red tides on mariculture ecosystems.

U-Net Convolutional Neural Network Model for Deep Red Tide Learning Using GOCI

Kim, S.M.; Shin, J.; Baek, S., and Ryu, J.-H., 2019. U-Net convolutional neural network model for deep red tide learning using GOCI. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Remote Sensing and Geoscience Information Systems of Coastal Environments. Journal of Coastal Research, Special Issue No. 90, pp. 302-309. Coconut Creek (Florida), ISSN 0749-0208.GOCI launched in 2010 is a geostationary satellite image sensor that monitors ocean color. It captures 8-band spectral satellite images of northeast Asian regions hourly, eight times a day. The spatial resolution of GOCI is about 500 m. GOCI is capable of monitoring a large ocean area for sensing various events such as red tide occurrences, tidal movement changes and ocean disasters. In this study, we propose a deep convolutional neural network model, U-Net, for automatic pixel-based detection of red tide occurrence from the spectral images captured by GOCI. We construct two training datasets with GOCI images and the corresponding red-tide index maps (RI maps) accumulated through 2011 to 2018. The RI maps indicate where red tides occurred and what kind of red tide species were there. U-Net consists of five U-shaped encoder and decoder layers to extract spectral features relating to red-tide species from GOCI images. We compared the performances of U-Nets trained from two datasets (i) consisting of only four spectral bands and (ii) consisting of all six spectral bands. The RI maps predicted by the trained U-Nets showed considerably matching spatial occurrence tendencies of three red tide species to the ground truths for validation images. The mean target accuracy with the four-band dataset was 13 % lower than that with the six-band dataset. The trained U-Net for pixel-wise red tide detection would be able to effectively inspect red tide occurrences in the huge area of water surrounding the Korean peninsula.

High-frequency acoustic backscattering characteristics for acoustic detection of the red tide species Akashiwo sanguinea and Alexandrium affine

Harmful algal blooms (HABs), caused by the overgrowth of certain phytoplankton species, have negative effects on marine environments and coastal fisheries. In addition to cell-counting methods using phytoplankton nets, a hydroacoustic technique based on acoustic backscattering has been proposed for the detection of phytoplankton blooms. However, little is known of the acoustic properties of HAB species. In this study, as essential data to support this technique, we measured the acoustic properties of two HAB species, Akashiwo sanguinea and Alexandrium affine, which occur in the South Sea off the coast of Korea. Due to the small size of the target, we used ultrasound for the measurements. Experiments were conducted under laboratory and field conditions. In the laboratory experiment, the acoustic signal re]from each species was directly proportional to the cell abundance. We derived a relationship between the cell abundance and acoustic signal re]for each species. The measured signals were compared to predictions of a fluid sphere scattering model. When A. sanguinea blooms appeared at an abundance greater than 3 500 cells/mL, the acoustic signals varied with cell abundance, showing a good correlation. These results confirm that acoustic measurements can be used to detect HAB species.

Fate of four phthalate esters with presence of Karenia brevis: Uptake and biodegradation

Phthalate esters (PAEs), one class of the most frequently detected endocrine-disrupting chemicals (EDCs) in marine environment, have aroused wide public concerns because of their carcinogenicity, teratogenicity, and mutagenicity. However, the environmental fate of PAEs in the occurrence of harmful algal blooms remains unclear. In this research, four PAEs with different alkyl chains, i.e., dimethyl phthalate (DMP), diethyl phthalate (DEP), diallyl phthalate (DAP), and dipropyl phtalate (DPrP) were selected as models to investigate toxicity, uptake, and degradation of PAEs in seawater grown with K. brevis, one of the common harmful red tide species. The 96-h median effective concentration (96h-EC50) values followed the order of DMP (over 0.257 mmol L−1) > DEP (0.178 mmol L−1) > DAP (0.136 mmol L−1) > DPrP (0.095 mmol L−1), and the bio-concentration factors (BCFs) were positively correlated to the alkyl chain length. These results indicate that the toxicity of PAEs and their accumulation in K. brevis increased with increasing alkyl chains, due to the higher lipophicity of the longer chain PAEs. With growth of K. brevis for 96 h, the content of DMP, DEP, DAP, and DPrP decreased by 93.3%, 68.2%, 57.4% and 46.7%, respectively, mainly attributed to their biodegradation by K. brevis, accounting for 87.1%, 61%, 46%, 40% of their initial contents, respectively. It was noticed that abiotic degradation had little contribution to the total reduction of PAEs in the algal cultivation systems. Moreover, five metabolites were detected in the K. brevis when exposed to DEP including dimethyl phthalate (DMP), monoethyl phthalate (MEP), mono-methyl phthalate (MMP), phthalic acid (PA), and protocatechuic acid (PrA). While when exposed with to DPrP, one additional intermediate compound diethyl phthalate (DEP) was detected in the cells of K. brevis in addition to the five metabolites mentioned above. These results confirm that the main biodegradation pathways of DEP and DPrP by K. brevis included de-esterification, demethylation or transesterification. These findings will provide valuable evidences for predicting the environmental fate and assessing potential risk of PAEs in the occurrence of harmful algal blooms in marine environment.

Remote quantification of Cochlodinium polykrikoides blooms occurring in the East Sea using geostationary ocean color imager (GOCI)

Accurate and timely quantification of widespread harmful algal bloom (HAB) distribution is crucial to respond to the natural disaster, minimize the damage, and assess the environmental impact of the event. Although various remote sensing-based quantification approaches have been proposed for HAB since the advent of the ocean color satellite sensor, there have been no algorithms that were validated with in-situ quantitative measurements for the red tide occurring in the Korean seas. Furthermore, since the geostationary ocean color imager (GOCI) became available in June 2010, an algorithm that exploits its unprecedented observation frequency (every hour during the daytime) has been highly demanded to better track the changes in spatial distribution of red tide. This study developed a novel red tide quantification algorithm for GOCI that can estimate hourly chlorophyll-a (Chl a) concentration of Cochlodinium (Margalefidinium) polykrikoides, one of the major red tide species around Korean seas. The developed algorithm has been validated using in-situ Chl a measurements collected from a cruise campaign conducted in August 2013, when a massive C. polykrikoides bloom devastated Korean coasts. The proposed algorithm produced a high correlation (R2=0.92) with in-situ Chl a measurements with robust performance also for high Chl a concentration (300mg/m3) in East Sea areas that typically have a relatively low total suspended particle concentration (<0.5mg/m3).

Genome size of Alexandrium catenella and Gracilariopsis lemaneiformis estimated by flow cytometry

Flow cytometry (FCM) technique has been widely applied to estimating the genome size of various higher plants. However, there is few report about its application in algae. In this study, an optimized procedure of FCM was exploited to estimate the genome size of two eukaryotic algae. For analyzing Alexandrium catenella, an important red tide species, the whole cell instead of isolated nucleus was studied, and chicken erythrocytes were used as an internal reference. The genome size of A. catenella was estimated to be 56.48 ± 4.14 Gb (1C), approximately nineteen times larger than that of human genome. For analyzing Gracilariopsis lemaneiformis, an important economical red alga, the purified nucleus was employed, and Arabidopsis thaliana and Chondrus crispus were used as internal references, respectively. The genome size of Gp. lemaneiformis was 97.35 ± 2.58 Mb (1C) and 112.73 ± 14.00 Mb (1C), respectively, depending on the different internal references. The results of this research will promote the related studies on the genomics and evolution of these two species.

A hierarchy of conceptual models of red-tide generation: Nutrition, behavior, and biological interactions

Red tides – discolorations of the sea surface due to dense plankton blooms – occur regularly in coastal and offshore waters along much of the world's coastline. Red tides often cause large-scale mortalities of fish and shellfish and significant losses to the aquaculture and tourist industries of many countries. Therefore, understanding and predicting the mechanisms controlling the outbreak, persistence, spread, and decline of red tides are important concerns to scientists, officials, industry, and the public. With increasing knowledge of red-tide species and red-tide events, new mechanisms have been discovered. Based on the nutrition and behaviors of red-tide organisms and biological interactions among them, red-tide outbreaks can be categorized into a hierarchy of four generation mechanisms (GM1–GM4). In the simplest, GM1, all phototrophic red-tide species were treated as exclusively autotrophic organisms without the ability to swim. However, this GM cannot explain red-tide outbreaks in oligotrophic surface waters offshore. Vertical migration (considered in GM2) and mixotrophy (GM3) enable red-tide flagellates to acquire growth factors from nutrient-rich deep waters or co-occurring prey, respectively. In natural environments, all red tides occur by those species outgrowing co-occurring organisms; red-tide species dominate communities by eliminating other species or reducing their abundances. Thus, GM4 contains the direct biological interactions (i.e., inhibition by physical contact or chemical effects) and indirect biological interactions (i.e., acquiring resources faster than others) that can affect the dominance of red-tide species under given conditions. Correctly choosing one of these four GMs for red tides dominated by one causative species is important because the accuracy of predictions may be outweighed by the costs and time required to acquire the relevant information. In this study, mechanisms describing the outbreak, persistence, and decline of red tides were reviewed, the advantages and limitations of each mechanism were evaluated, and insights about the evolution of the mechanisms were developed.

Bioremediation efficiency of the largest scale artificial Porphyra yezoensis cultivation in the open sea in China

The bioremediation efficiency of China’s largest scale Porphyra yezoensis cultivation for removing dissolved nutrients and controlling harmful algae was studied in the radial sandbanks waters of Jiangsu Province in the year 2012–2013. Mean nutrient concentration values in the P. yezoensis cultivation area were significantly lower than those in the non-cultivation area, especially during the cultivation season (p<0.05). Tissue nitrogen and phosphorus contents of seaweeds were 5.99–0.80% (dry weight (DW)) and 0.16–0.19% (DW), respectively. Production of P. yezoensis was 58950.87tons DW. Based on these values, 3688.15tons of tissue nitrogen and 105.61tons of tissue phosphorus were removed by harvesting P. yezoensis. The richness index of the red tide species Skeleton emacostatum declined from 0.32 to 0.05 during the P. yezoensis cultivation season. These results indicate that large-scale cultivation of P. yezoensis can be used to efficiently alleviate eutrophication and control harmful algae blooms in open sea.

An Algorithm for Red Tides Species’ Identification Based on Spectral Characteristics and Wavelet Analysis

Hyperspectral remote sensing technology provides a new way to identify red tides types, but many existing methods can’t take full advantage of the spectral reflectance characteristics and often yield false recognitions. So, on the premise of perfect spectral curves library of red tides to be referred, this paper proposes an algorithm based on spectral reflectance characteristics and wavelet decomposition for red tides recognition. The algorithm identify the red tide species by applying wavelet analysis to a certain wavelength range limited by the spectral features. To compare and prove the effect of this algorithm, do simulate experiments with both the proposed method and the traditional SAM method. The results show that, compared with SAM method, the algorithm put forward in this paper can better indentify the species of red tides.

인천항 내, 외에서 식물플랑크톤 위해종의 분포특성

인천항에서 선박평형수 배출수에 기인한 외래종을 고려한 항만환경 관리수준 설정을 위해 식물플랑크톤의 잠재적 위해종 출현 특성과 관련된 환경영향 요인을 2007년 2월부터 2009년 11월까지 인천항 내측 및 외측에서 계절조사를 수행하였다. 조사결과, 한국 주변해역에서 출현한 바 있는 식물플랑크톤 62종이 관찰되었고, 그 중에 적조원인종 13종과 독소생산종 7종의 잠재적 위해종이 관찰되었다. 잠재적 위해종은 여름철과 겨울철에 인천항 외측에서 더 다양하게 출현하였다. 봄과 겨울철에는 적조원인종인 Skeletonema spp., Thalassiosira nordenskioldii, Paralia sulcata가 항만 내측 (평균 72.4%) 및 외측(평균 77.6%)에서 모두 우점 하였고, 수소이온과 부유물질의 농도와 양의 상관관계를 나타냈다(p<0.05). 여름철에는 인천항 내측에서 적조원인종(Skeletonema spp.) 및 독소생산종(Alexandrium catanella, A. tamarense, Dinophysis acuminata, Pseudo-nitzschia spp.)이 혼합 우점 (평균 74.2%) 하였으나, 외측에서는 Skeletonema spp.와 P. sulcata가 우점 (평균 67.2%)하였다. 연구기간 동안 출현한 독소생산종 들은 용존 무기질산염, 규산염, 인산염 및 화학적 산소요구량과 양의 상관관계를 나타냈다(p<0.05). 식물플랑크톤 엽록소-a 농도는 봄과 여름 및 가을철에 인천항 외측에서 각각 평균 <TEX>$3.05{\mu}g/L$</TEX>, <TEX>$1.49{\mu}g/L$</TEX>, <TEX>$5.46{\mu}g/L$</TEX>로 내측보다 3-5배 높은 농도가 높았고, 겨울철에는 내측 (평균 <TEX>$0.94{\mu}g/L$</TEX>) 및 외측 (평균 <TEX>$0.95{\mu}g/L$</TEX>) 간 농도 차이가 없었다. 요약하면, 인천항 외측은 다양한 적조원인종이 우점하며 엽록소-a 농도가 높았으나, 항만 내측은 여름철 독소생산종의 출현 종수가 높게 나타났고, 외측에 비해 엽록소-a 농도가 낮았다. 각 위해종들의 대 발생 가능성은 영양염, 화학적 산소요구량 및 부유물질의 농도와 비례한 것으로 나타나, 항만 내, 외측의 환경특성을 고려한 잠재적 위해종 관리가 요구된다. This study examined the occurring pattern of potential risky species and the related abiotic factors for port-specific environmental management considering the control of ballast water-induced foreign species at Incheon seaport. From a total of 62 species observed during the study, 13 red-tide and 7 toxic phytoplankton, normally occurring species in Korean waters, occurred from the seasonal investigation at the inner and outer sites of the Incheon seaport from 2007 to 2009. The number of potential risky phytoplankton was relatively high at the outer site of the port during summer and winter. Red-tide species, such as Skeletonema spp., Thalassiosira nordenskioldii, and Paralia sulcata, dominated the total standing crops at the inner site (avg. 72.4%) and outer site (avg. 77.6%) in spring and summer, being positively correlated with the concentrations of total suspended solids (TSS) and pH (p<0.05). In summer, the red-tide species (Skeletonema spp.) and toxic species (Alexandrium catenella, A. tamarense, Dinophysis acuminata and Pseudo-nitzschia spp.) co-dominated (avg. 74.2%) at the inner site, while Skeletonema spp. and P. sulcata predominated (avg. 67.2%) at the outer site. During the study periods, the toxic species were significantly and positively correlated with the chemical oxygen demand (COD), dissolved inorganic nitrogen, silicate and phosphate (p < 0.05). The chlorophyll-a (chl-a) concentration of phytoplankton at the outer site ranged from 1.49 to <TEX>$5.46{\mu}g/L$</TEX> on average, which was 3-5 times higher than that at the inner site in spring, summer and autumn, whereas there was no difference in the concentration between inner (avg. <TEX>$0.94{\mu}g/L$</TEX>) and outer (avg. <TEX>$0.95{\mu}g/L$</TEX>) sites in winter. In summary, diverse red-tide species dominated and a relatively high chl-a concentration existed at the outer site, whereas a relatively high number of toxic species and low chl-a concentration was observed at the inner site in summer. The potential risky species can outbreak in association with the concentration of nutrients, COD and TSS, suggesting that distinctive management of potential risky species is needed considering the environmental characteristics of Incheon seaport.