Effects of modified clay used for the control of harmful algal blooms on Alexandrium pacificum cysts

Harmful Algae ◽  
2018 ◽  
Vol 72 ◽  
pp. 36-45 ◽  
Author(s):  
Yue Zhang ◽  
Zhiming Yu ◽  
Xiuxian Song ◽  
Yongquan Yuan ◽  
Xihua Cao
2021 ◽  
Vol 869 (1) ◽  
pp. 012068
Author(s):  
X Qin ◽  
X Chen ◽  
F Li ◽  
H Ya ◽  
D Zhu ◽  
...  

Abstract With the increased scale of marine aquaculture in the Beibu Gulf, as well as accelerating urbanization and industrialization, frequent harmful algal blooms (HABs) have occurred in this area, especially those formed by Phaeocystis globosa in the past several years. As the P. globosa bloom has been a serious marine ecological disaster in the Beibu Gulf, research on quick and effective methods to eliminate P. globosa blooms is a hot research topic. In this study, the bacteria Streptomyces yatensis B4503 combined with modified diatomite was used to prepare algicidal modified clay, which was then used to study the removal effect on P. globosa blooms in field culture enclosures. The results showed that after 6 h of treatment with algicidal modified clay, compared with the blank control group, the cell density and chlorophyll a content of P. globosa decreased by 26.86% and 64.03%, respectively, and they decreased by 75.23% and 84.81%, respectively, after 24 h. The study indicated that algicidal modified clay can be applied to eliminate HABs caused by P. globosa in coastal water.


2021 ◽  
Vol 9 (8) ◽  
pp. 822
Author(s):  
Peipei Zhang ◽  
Xiuxian Song ◽  
Yue Zhang ◽  
Huihui Shen ◽  
Xueyi Dong ◽  
...  

An outbreak of harmful algal blooms (HABs) often leads to the death of fish and other marine organisms and causes serious losses to human economic activities. Modified clay (MC) technology is an effective way to control HABs. Although the material and preparation process are based on the premise of green and safety, the potential eco-environmental impacts of MC on non-target organisms should still have to receive attention before field applications can occur. Therefore, the effects of one commonly used modified clay, polyaluminum chloride-modified clay (PAC-MC), on the survival, growth, and oxidative stress of the marine medaka (Oryzias melastigma) were studied. The toxicity test results showed that the 96-h median lethal concentration (96-h LC50) of PAC-MC for newly hatched medaka larvae was 5.204 g/L, which was much higher than the concentration used on site (4–10 t/km2). Within the concentration range of PAC-MC used in this experiment (≤2 g/L), the morphology, heart rate, growth, and aluminum content of larvae did not change with the increase in the modified clay concentration. Low concentrations of PAC-MC (≤0.5 g/L) did not significantly affect catalase (CAT) activity, superoxide dismutase (SOD) activity, peroxidase (POD) activity, and the content of malondialdehyde (MDA), but higher concentrations of PAC-MC (such as 2 g/L) caused oxidative damage to the larvae and increased the antioxidant enzyme activity of the larvae. The present study revealed that under an effective dosage for treating harmful algal blooms on site, PAC-MC had no adverse effects on the survival, growth, oxidative stress, and aluminum content of the newly hatched marine medaka, which provides a scientific basis for the field application of modified clay.


2015 ◽  
Vol 16 (1) ◽  
pp. 180-185
Author(s):  
Yawen Huang ◽  
Yong Pang ◽  
Guoxiang Wang ◽  
Ruiming Han ◽  
Jianjian Wang ◽  
...  

Flocculation using modified clays is a technique widely applied in the management of harmful algal blooms (HABs). Polyaluminum chloride (PAC) modified clay is an efficient flocculating agent in HAB control; however its effectiveness in black bloom management is still largely unknown. In the present study, PAC-modified clay was used to flocculate a black bloom under simulated flows. The deposition and resuspension of the black matter/clay flocs and the impact of the spreading of quartz sand to the flocs were quantitatively studied. The results showed that a dosage of 1.8 g/L PAC-modified clay (0.8 g/L PAC and 1 g/L diatomite) could reduce turbidity by more than 90% in 1 h. The resuspension of flocs could be generated by a threshold bed shear stress of 0.045 N/m2. The addition of quartz sand inhibited the resuspension of flocs. We suggest that quartz sand can be used to effectively inhibit floc resuspension caused by waves and flow currents as the subsequent treatment of black bloom flocculation in Lake Taihu.


Author(s):  
Xiangzheng Ren ◽  
Zhiming Yu ◽  
Lixia Qiu ◽  
Xihua Cao ◽  
Xiuxian Song

Phaeocystis globosa is a globally distributed harmful algal blooms (HABs) species dominated by the colonial morphotype, which presents dramatic environmental hazards and poses a threat to human health. Modified clay (MC) can effectively flocculate HAB organisms and prevent their subsequent growth, but the effects of MC on colony-dominated P. globosa blooms remain uncertain. In this paper, a series of removal and incubation experiments were conducted to investigate the growth, colony formation and colony development of P. globosa cells after treatment with MC. The results show that the density of colonies was higher at MC concentrations below 0.2 g/L compared to those in the control, indicating the role of P. globosa colonies in resistance to environmental stress. Concentrations of MC greater than 0.2 g/L could reduce the density of solitary cells and colonies, and the colony diameter and extracellular polysaccharide (EPS) content were also decreased. The adsorption of MC to dissolved inorganic phosphorus (DIP) and the cell damage caused by collision may be the main mechanisms underlying this phenomenon. These results elucidate that the treatment with an appropriate concentration of MC may provide an effective mitigation strategy for P. globosa blooms by preventing their growth and colony formation.


Shore & Beach ◽  
2020 ◽  
pp. 34-43
Author(s):  
Nicole Elko ◽  
Tiffany Roberts Briggs

In partnership with the U.S. Geological Survey Coastal and Marine Hazards and Resources Program (USGS CMHRP) and the U.S. Coastal Research Program (USCRP), the American Shore and Beach Preservation Association (ASBPA) has identified coastal stakeholders’ top coastal management challenges. Informed by two annual surveys, a multiple-choice online poll was conducted in 2019 to evaluate stakeholders’ most pressing problems and needs, including those they felt most ill-equipped to deal with in their day-to-day duties and which tools they most need to address these challenges. The survey also explored where users find technical information and what is missing. From these results, USGS CMHRP, USCRP, ASBPA, and other partners aim to identify research needs that will inform appropriate investments in useful science, tools, and resources to address today’s most pressing coastal challenges. The 15-question survey yielded 134 complete responses with an 80% completion rate from coastal stakeholders such as local community representatives and their industry consultants, state and federal agency representatives, and academics. Respondents from the East, Gulf, West, and Great Lakes coasts, as well as Alaska and Hawaii, were represented. Overall, the prioritized coastal management challenges identified by the survey were: Deteriorating ecosystems leading to reduced (environmental, recreational, economic, storm buffer) functionality, Increasing storminess due to climate change (i.e. more frequent and intense impacts), Coastal flooding, both Sea level rise and associated flooding (e.g. nuisance flooding, king tides), and Combined effects of rainfall and surge on urban flooding (i.e. episodic, short-term), Chronic beach erosion (i.e. high/increasing long-term erosion rates), and Coastal water quality, including harmful algal blooms (e.g. red tide, sargassum). A careful, systematic, and interdisciplinary approach should direct efforts to identify specific research needed to tackle these challenges. A notable shift in priorities from erosion to water-related challenges was recorded from respondents with organizations initially formed for beachfront management. In addition, affiliation-specific and regional responses varied, such as Floridians concern more with harmful algal blooms than any other human and ecosystem health related challenge. The most common need for additional coastal management tools and strategies related to adaptive coastal management to maintain community resilience and continuous storm barriers (dunes, structures), as the top long-term and extreme event needs, respectively. In response to questions about missing information that agencies can provide, respondents frequently mentioned up-to-date data on coastal systems and solutions to challenges as more important than additional tools.


Harmful Algae ◽  
2021 ◽  
pp. 101975
Author(s):  
Donald M. Anderson ◽  
Elizabeth Fensin ◽  
Christopher J. Gobler ◽  
Alicia E. Hoeglund ◽  
Katherine A. Hubbard ◽  
...  

Author(s):  
Shannon J Sibbald ◽  
Maggie Lawton ◽  
John M Archibald

Abstract The Pelagophyceae are marine stramenopile algae that include Aureoumbra lagunensis and Aureococcus anophagefferens, two microbial species notorious for causing harmful algal blooms. Despite their ecological significance, relatively few genomic studies of pelagophytes have been carried out. To improve understanding of the biology and evolution of pelagophyte algae, we sequenced complete mitochondrial genomes for A. lagunensis (CCMP1510), Pelagomonas calceolata (CCMP1756) and five strains of A. anophagefferens (CCMP1707, CCMP1708, CCMP1850, CCMP1984 and CCMP3368) using Nanopore long-read sequencing. All pelagophyte mitochondrial genomes assembled into single, circular mapping contigs between 39,376 base-pairs (bp) (P. calceolata) and 55,968 bp (A. lagunensis) in size. Mitochondrial genomes for the five A. anophagefferens strains varied slightly in length (42,401 bp—42,621 bp) and were 99.4%-100.0% identical. Gene content and order was highly conserved between the A. anophagefferens and P. calceolata genomes, with the only major difference being a unique region in A. anophagefferens containing DNA adenine and cytosine methyltransferase (dam/dcm) genes that appear to be the product of lateral gene transfer from a prokaryotic or viral donor. While the A. lagunensis mitochondrial genome shares seven distinct syntenic blocks with the other pelagophyte genomes, it has a tandem repeat expansion comprising ∼40% of its length, and lacks identifiable rps19 and glycine tRNA genes. Laterally acquired self-splicing introns were also found in the 23S rRNA (rnl) gene of P. calceolata and the coxI gene of the five A. anophagefferens genomes. Overall, these data provide baseline knowledge about the genetic diversity of bloom-forming pelagophytes relative to non-bloom-forming species.


Water ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1409
Author(s):  
Hamdhani Hamdhani ◽  
Drew E. Eppehimer ◽  
David Walker ◽  
Michael T. Bogan

Chlorophyll-a measurements are an important factor in the water quality monitoring of surface waters, especially for determining the trophic status and ecosystem management. However, a collection of field samples for extractive analysis in a laboratory may not fully represent the field conditions. Handheld fluorometers that can measure chlorophyll-a in situ are available, but their performance in waters with a variety of potential light-interfering substances has not yet been tested. We tested a handheld fluorometer for sensitivity to ambient light and turbidity and compared these findings with EPA Method 445.0 using water samples obtained from two urban lakes in Tucson, Arizona, USA. Our results suggested that the probe was not sensitive to ambient light and performed well at low chlorophyll-a concentrations (<25 µg/L) across a range of turbidity levels (50–70 NTU). However, the performance was lower when the chlorophyll-a concentrations were >25 µg/L and turbidity levels were <50 NTU. To account for this discrepancy, we developed a calibration equation to use for this handheld fluorometer when field monitoring for potential harmful algal blooms in water bodies.


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