• ALGAE
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• v.22 no.4
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• pp.319-323
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• 2007

This study was conducted with using chlorophyll a fluorescence (indicated as photosynthetic activity) to examine the toxic effect of 96 h exposure of heavy metals and herbicides on the benthic diatom Nitzschia sp. which was isolated from pristine sediment in Pamquat Harbour, Nova Scotia, Canada. Samples of benthic diatom were exposed to 0, 0.01, 0.1 and 1 mg L–1 of copper, 0, 1, 10 and 100 mg L–1 of chrome (VI), 0, 2.45, 24.5 and 245 mg L–1 of paraquat dichloride, and 0, 4.37, 43.7 and 437 mg L–1 of alachlor during 96 hours. The effective quantum yield of photochemistry (ΔF/Fm’) was evaluated by subjecting light acclimated samples to saturating pulses of light using a pulse amplitude modulated (PAM) fluorometer. The impact of heavy metals on Nitzschia sp. photosynthesis was not severe in < 1 mg L–1 but in the high concentrations (> 1 mg L–1) clearly increased toxic stress during 96 h. Herbicides had a limited impact during the exposure period but clearly increased stress on the benthic diatom with increasing concentrations. Acute response of Nitzschia sp. to selected heavy metals and herbicides was characterized, and the capacity of a benthic diatom to tolerate and recover from toxic stress was assessed.

• Journal of Korean Society on Water Environment
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• v.27 no.6
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• pp.855-861
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• 2011

Short-term effects of current velocity and turbid water on the benthic diatom community and water quality were examined in artificial channel ($20{\times}200{\times}10cm$) with two different experiments. The first and second experiments were consisted of different current velocities such as 1 L/min., and 1, 3, and 6 L/min., respectively. The concentration of turbid water is prepared with loess and fixed at 10 and 20 times of the turbidity of control inflow (10 NTU, LTW), respectively. At experiment 1 (EXP-1), introduction of turbid water increased dissolved oxygen, electric conductivity, pH and turbidity, but there were no differences between low- (100 NTU, MTW) and high-turbid water (200 NTU, HTW). However, experiment 2 (EXP-2) did not change any environmental parameters except dissolved total and inorganic nitrogen like EXP-1. MTW in EXP-1 strongly stimulated the growth of benthic diatom, while both MTW (150 NTU) and HTW (300 NTU) in EXP-2 did not increase or decrease the diatom abundance. Over the study, the dominant species was four, Aulacoseira ambigua, Cyclotella stelligera, Aulacoseira granulata and Achnanthes minutissima. In EXP-1, two highest species in abundance, A. ambigua and A. granulata were highly grown in MTW, while Achnanthes minutissima high in HTW adversely. These results indicate that the introduction of turbid water can play an important role in the shift of water quality and benthic diatom community in stream ecosystem, especially inflow of soil water in low current velocity.

• ALGAE
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• v.33 no.2
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• pp.167-180
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• 2018

Benthic diatoms are ubiquitous in tidal flats and play major roles in maintaining coastal ecosystems. Spatio-temporal variations in diatom diversity have not been well-studied, mainly because of difficulties in morphological identification and the lack of appropriate genetic tools. To overcome these problems, we used the gene encoding the ribulose bisphosphate carboxylase large-subunit (rbcL) as a molecular marker, and sequenced these genes with the aid of the MiSeq platform. In this manner, we explored the genetic diversity of benthic diatoms in tidal flats of Guenso Bay on the west coast of Korea; differences in the spatial distributions of benthic diatoms were evident. The diatom communities were dominated by Nitzschia, Navicula, and Amphora; their relative distributions were affected by the sand proportion, grain size, and air exposure time. Our results suggest that meta-barcoding of the rbcL gene and next-generation sequencing can be used to explore the diversity of benthic diatoms.

• Journal of Ecology and Environment
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• v.36 no.4
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• pp.371-390
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• 2013

Remarkable diversity of diatom taxa occurs in intertidal sand-flats of the Nakdong River estuary, one of the most dynamic and productive ecosystem in Korea. Benthic diatoms were collected from the sandy sediments to clarify the taxonomic accounts and distribution of the old genus Navicula, i.e., the naviculoid flora. Total 92 taxa belonging to Navicula sensu stricto and 22 genera separated from Navicula sensu lato are reported with brief descriptions and micrographs, and many species remain unidentified. The genera are ranked by the number of diatom species: Navicula of 33 species and varieties, Fallacia of 17 species, Placoneis of five species, Fogedia and Parlibellus of four species, Austariella, Hippodonta and Petroneis of three species, Cosmioneis, Diadesmis, Luticola, Moreneis and Sellaphora of two species and variety, Berkeleya, Chamaepinnularia, Cocconeiopsis, Diademoides, Dickieia, Eolimna, Geissleria, Haslea, Lyrella and Mayamaea of one species. Through 32 samplings of the 12 areas, the important species were identified Navicula perminuta, N. gregaria, N. torneensis, Fallacia cunoniae, F. litoricola, F. subforcipata, F. tenera. The naviculoid diatoms constitute an average of 27% (range: minimum to maximum, 5-75%), of the benthic diatom assemblages. The diatom assemblages are characterized by the colonizing of a few dominant or frequent species and many occasional or rare species. The dominant species were observed to fluctuate with sampling site and time. Among the reported naviculoid diatoms, 46 taxa are newly reported in Korea.

• The Korean Journal of Malacology
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• v.29 no.3
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• pp.197-205
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• 2013

Even though seedling production of Haliotis discus hannai has fully developed, the culture of benthic diatom as a live food for larvae is still a barrier to solve in commercial hatchery. The farmer depends on mixed microalgae which are non-selectively attached on the plate by flowing of natural seawater. The adequate diatom on the plate for the larvae in terms of quality and quantity is always significant bottleneck in the hatchery. In this study, two benthic diatom species, Caloneis schroederi and Rhaphoneis sp. were separately cultured in mass and inoculated to four tons' settlement tank of the larvae. And the larvae and the spats were cultured for nineteen and nine weeks, respectively. The result on seedling production of H. discus hannai with this method was compared to that of the farmer's traditional method as a control. With regard to variation of species composition of benthic diatom on the plate, C. schroederi and Rhaphoneis sp. were dominant for first three weeks after inoculation. But the diverse diatoms mainly, Navicula, Amphora, Cylindrotheca, Licmophora, Pleurosigma began to attache on the plate from the 4th week. The larvae attached 2.5 times more in C. schroederi tank than in the control tank. The final total biomass of the seeds in Rhaphoneis sp. tank was 3.2 times more than that of the control tank. The retared-spats in the seedling production also showed significantly higher growth and survival in the spat fed Rhaphoneis sp. or C. schroederi than those in the control group. We suggest that C. schroederi is proper for settlement of the larvae and Rhaphoneis sp. is appropriate for the growth of the larvae and spats in the commercial hatchery of H. discus hannai.

• Journal of Plant Biology
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• v.30 no.2
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• pp.117-133
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• 1987

The diatoms were investigated at three lowland swamps in Haman county form July, 1983 to July, 1984 on monthly interval. Seasonal changes of standing crops, the variation of dominant species and species composition were studied. The maximum of standing crops showed bimodal pattern at Chilnalpol and Yujnnup. Dominant species were Navicula crytocephala, Cocconeis placentula, Achnanthes minutissima, Achnanthes lanceolata, Synedra ulna, Eunotia lunaris. Dominant species changed seasonally. Total 166species of diatom were identified. Three lowland swamps supported a rich diatom flora composed of many species typically associated with benthic diatom.

• ALGAE
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• v.35 no.4
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• pp.361-373
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• 2020

The community dynamics of benthic diatoms in the hypersaline environment are investigated to advance our understanding how salinity impacts marine life. Diatoms were sampled in the two salterns encompassing salt Ponds, ditches, and seawater reservoirs (n = 11), along the salinity gradient (max = 324 psu), and nearby tidal flats (n = 2). The floral assemblages and distributions across sites and stations showed great variations, with a total of 169 identified taxa. First, not surprisingly, higher diversity of benthic diatoms was found at natural tidal flats than salterns. The saltern diatoms generally showed salinity dependent distributions with distinct spatial changes in species composition and dominant taxa. Biota-environment and principal component analysis confirmed that salinity, mud content, and total nitrogen were key factors influencing the overall benthic community structure. Some dominant species, e.g., Nitzschia scalpelliformis and Achnanthes sp. 1, showed salinity tolerance / preference. The number of diatom species at salinity of >100 psu reduced over half and no diatoms were found at maximum salinity of 324 psu. The highest salinity for the observed live diatoms was 205 psu, however, a simple regression indicated a theoretical salinity threshold of ~300 psu on the survival. Finally, the indicator species were identified along the salinity gradient in salterns as well as natural tidal flats. Overall, high species numbers, varying taxa, and euryhaline distributions of saltern diatoms collectively reflected a dynamic saltern ecosystem. The present study would provide backgrounds for biodiversity monitoring of ecologically important microalgal producers in some unique hypersaline environment, and elsewhere.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.879-885
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• 2009

The present study was carried out to develop biological criteria for water quality assessment using benthic diatoms. Selecting of the indicator diatoms, three parameters were considered: broad distribution (180 taxa occurred over 3% at upper level), species abundance (158 taxa occurred over $1.5{\times}10^5cells/cm^2$), and sensitivity (184 taxa occurred more than once as 1st and 2nd dominant species). Overall, total 208 taxa were selected, including 38 varieties, 170 species, 34 genera, 9 families, 3 orders, and 1 phylum. The most dominant taxonomic group (family) was Naviculaceae (52%), followed by Diatomaceae (15%), Nitzschiaceae (12%) and Achnantaceae (11%). COD and TP were proposed as new water quality standards (draft) to improve the existing BOD standard and to manage and control efficiently non-biodegradable organic pollutants. With this regard, we used TP standard (draft) in developing biological water quality criteria for diatoms. TP standards (draft) proposed as Ia = 0.02 mg/L or less, Ib = 0.05 mg/L or less, II = 0.1 mg/L or less, III = 0.2 mg/L or less, IV = 0.4 mg/L or less, V = 0.6 mg/L or less and VI = above 0.6 mg/L. Biological assessment system (4 class system) was developed and proposed for diatom using modified Tropic Diatom Index (TDI). Biological assessment of TDI appear B grade (Good).

• Korean Journal of Ecology and Environment
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• v.45 no.1
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• pp.110-122
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• 2012

This study examined the benthic diatom community distribution, land cover/use and water quality in relation to stream shape complexity (SSC) in the Seom River watershed. SSC showed a significant relation to the riparian land cover/use pattern and also water quality variables of the studied streams. Streams with high stream shape complexity (HSC) appeared to have a high proportion of forest and farmland, while streams having a low stream shape complexity (LSC) appeared to have high proportion of city. Streams with lower SSC showed higher nutrients concentration in the stream waters. Benthic diatom species composition and dominant species appeared to be similar regardless of SSC differences among the studied streams, while the variation of diatom density was manifested with SSC. The relative abundance of dominant benthic diatoms varied with SSC. Saprophilic diatoms were dominant in the streams of LSC, while saproxenic diatoms were dominant in the streams of HSC. During the evaluation of biological water quality using the benthic diatom indices, Trophic Diatom Index (TDI) and Diatom Assemblage Index to organic water pollution (DAIpo), the streams of LSC generally showed poorer water quality than those of MSC (Middle stream shape complexity) and HSC. In particular, BOD, TP, and $PO_4$-P showed significant relationships with DAIpo. In conclusion, shape complexity of streams in the Seom River watershed showed a close relation with benthic diatom distribution. This relation seemed to primarily be resulted from the effect of proximate factors, such as water quality, which might be affected by the land use types determining the degree of SSC.

• Journal of Species Research
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• v.9 no.3
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• pp.191-197
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• 2020

Species belonging to the genus Tryblionella are important members of the diatom assemblages of benthic environments such as tidal flats. Their proper identification is thus of great importance in terms of taxonomy, ecology, as well as environmental sciences. However, many species of the genus have been neglected and/or misidentified during diatom studies of Korean tidal flats possibly due to the small size of the species. Lack of proper references for the identification of the species is also noted. To better understand the diversity of Tryblionella species, sediment samples were taken from various tidal flats of the Yellow Sea. Light microscope (LM) and scanning electron microscope (SEM) observations have shown the presence of Tryblionella adducta and T. hyalina, which have not been previously reported from Korean tidal flats. The former was found mostly from sand flats and the latter from mudflats. It is expected that the present study would contribute to a better understanding of the diversity and ecology of benthic diatoms of the Korean tidal flats.