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At least 19 recordsLinked to original sources
PubMedDate not supplied

Feeding by the heterotrophic dinoflagellate Oxyrrhis marina on the red-tide raphidophyte Heterosigma akashiwo: a potential biological method to control red tides using mass-cultured grazers.

As part of the development of a method to control the outbreak and persistence of red tides using mass-cultured heterotrophic protist grazers, we measured the growth and ingestion rates of cultured Oxyrrhis marina (a heterotrophic dinoflagellate) on cultured Heterosigma akashiwo (a raphidophyte) in bottles in the laboratory and in mesocosms (ca. 60 liter) in nature, and those of the cultured grazer on natural populations of the red-tide organism in mesocosms set up in nature. In the bottle incubation, specific growth rates of O. marina increased rapidly with increasing concentration of cultured prey up to ca. 950 ng C ml(-1) (equivalent to 9,500 cells ml(-1)), but were saturated at higher concentrations. Maximum specific growth rate (mumax), KGR (prey concentration sustaining 0.5 mumax) and threshold prey concentration of O. marina on H. akashiwo were 1.43 d(-1), 104 ng C ml(-1), and 8.0 ng C ml(-1), respectively. Maximum ingestion and clearance rates of O. marina were 1.27 ng C grazer(-1) d(-1) and 0.3 microl grazer(-1) h(-1), respectively. Cultured O. marina grew well effectively reducing cultured and natural populations of H. akashiwo down to a very low concentration within 3 d in the mesocosms. The growth and ingestion rates of cultured O. marina on natural populations of H. akashiwo in the mesocosms were 39% and 40%, respectively, of those calculated based on the results from the bottle incubation in the laboratory, while growth and ingestion rates of cultured O. marina on cultured H. akashiwo in the mesocosms were 55% and 36%, respectively. Calculated grazing impact by O. marina on natural populations of H. akashiwo suggests that O. marina cultured on a large scale could be used for controlling red tides by H. akashiwo near aquaculture farms that are located in small ponds, lagoons, semi-enclosed bays, and large land-aqua tanks to which fresh seawater should be frequently supplied.

Animals↗
PubMed2006

T2-weighted balanced SSFP imaging (T2-TIDE) using variable flip angles.

A new technique for acquiring T2-weighted, balanced steady-state free precession (b-SSFP) images is presented. Based on the recently proposed transition into driven equilibrium (TIDE) method, T2-TIDE uses a special flip angle scheme to achieve T2-weighted signal decay during the transient phase. In combination with half-Fourier image acquisition, T2-weighted images can be obtained using T2-TIDE. Numerical simulations were performed to analyze the signal behavior of T2-TIDE in comparison with TSE and b-SSFP. The results indicate identical signal evolution of T2-TIDE and TSE during the transient phase. T2-TIDE was used in phantom experiments, and quantitative ROI analysis shows a linear relationship between TSE and T2-TIDE SNR values. T2-TIDE was also applied to abdominal and head imaging on healthy volunteers. The resulting images were analyzed quantitatively and compared with standard T2-weighted and standard b-SSFP methods. T2-TIDE images clearly revealed T2 contrast and less blurring compared to T2-HASTE images. In combination with a magnetization preparation technique, STIR-weighted images were obtained. T2-TIDE is a robust technique for acquiring T2-weighted images while exploiting the advantages of b-SSFP imaging, such as high signal-to-noise ratio (SNR) and short TRs.

Brain↗
PubMed2003

HPLC pigment analysis of marine phytoplankton during a red tide occurrence in Tolo Harbour, Hong Kong.

A red tide was detected in the inner parts of Tolo Harbour, Hong Kong, in November 2000. Water samples were collected from a fixed station at the centre of the red tide patch for microscopic analysis of phytoplankton community composition and high performance liquid chromatography (HPLC) analysis of phytoplankton pigments. At the peak of the red tide on 24 November 2000, phytoplankton was dominated by the dinoflagellate Scrippsiella trochoidea. The red tide began to decline at the end of November and, by 1 December 2000, the phytoplankton was dominated by diatoms. Chlorophylls and carotenoids in water samples were analysed using HPLC pigment separation technique. Dinoflagellates were indicated by the signature pigment peridinin. Significant correlation (r=0.999) was found between the peridinin concentration and dinoflagellate density. A decrease in peridinin and an increase in fucoxanthin, a major carotenoid in diatoms, marked the shift in phytoplankton composition at the end of the red tide. HPLC analysis also revealed the occurrence of minor phytoplankton groups that are difficult to identify by light microscopy. Red tide monitoring and study of red tide dynamics in Hong Kong have been based on cell counting and spectrophotometric or fluorometric measurement of chlorophyll a. HPLC pigment analysis provides an effective alternative for investigating phytoplankton dynamics during red tide and other algal blooms.

Animals↗
PubMed2001

Abolition of pentagastrin-stimulated alkaline tide using the carbonic anhydrase inhibitor acetazolamide.

BACKGROUND: Alkaline tide is the transient increase in blood and urine pH following stimulation of gastric acid secretion. It is attributed to HCO3- release from parietal cells in parallel with H+ secretion. The enzyme carbonic anhydrase is thought to be responsible for HCO3- production from CO2 and OH- in the parietal cell. OBJECTIVE: To examine the effect of pretreatment with the carbonic anhydrase inhibitor, acetazolamide, on the alkaline tide phenomenon. METHODS: Ten patients with dyspepsia and demonstrable alkaline tide were tested on three separate days. The pH and base excess were determined in arterialized venous blood before and 45 minutes after an intramuscular injection of pentagastrin. The pH of the urine was measured before and 120 min after pentagastrin injection. Measurements were performed after pentagastrin alone on day 1, following pretreatment with acetazolamide 60 min before pentagastrin on day 2, and after the administration of acetazolamide alone on day 3. RESULTS: Following the administration of pentagastrin alone, the blood base excess increased by 1.61 +/- 0.2 mEq/L (mean +/- standard deviation) and the calculated alkaline tide at 45 min was 33.99 +/- 4.49 mEq. On day 2 with prior administration of acetazolamide, base excess decreased by 0.21 +/- 0.39 mEq/L, and the calculated alkaline tide was -3.28 +/- 7.57 mEq, which was significantly lower than on day 1 (P = 0.0001). On day 3, following acetazolamide alone, the base excess values decreased by 0.53 +/- 0.2 mEq/L and the alkaline tide was -10.05 +/- 3.33 mEq; there was no significant difference compared with day 2 (P = 0.44). CONCLUSION: Pretreatment with acetazolamide abolished the alkaline tide induced by pentagastrin. This finding supports the view that carbonic anhydrase has a major role in the alkaline tide phenomenon.

Acetazolamide↗
PubMed2006

Intrinsic fat suppression in TIDE balanced steady-state free precession imaging.

A novel fat-suppressed balanced steady-state free precession (b-SSFP) imaging method based on the transition into driven equilibrium (TIDE) sequence with variable flip angles is presented. The new method, called fat-saturated (FS)-TIDE, exploits the special behavior of TIDE signals from off-resonance spins during the flip angle ramp. As shown by simulations and experimental data, the TIDE signal evolution for off-resonant isochromats during the transition from turbo spin-echo (TSE)-like behavior to the true fast imaging with steady precession (TrueFISP) mode undergoes a zero crossing. The resulting signal notch for off-resonant spins is then used for fat suppression. The efficiency of FS-TIDE is demonstrated in phantoms and healthy volunteers on a 1.5T system. The resulting images are compared with standard TrueFISP data with and without fat suppression. It is demonstrated that FS-TIDE provides a fast and stable means for homogenous fat suppression in abdominal imaging while maintaining balanced SSFP-like image contrast and signal-to-noise ratio (SNR). The scan time of FS-TIDE is not increased compared to normal TrueFISP imaging without fat suppression and identical k-space trajectories. Because of the intrinsic fat suppression, no additional preparation is needed. Possible repetition times (TRs) are not firmly limited to special values and are nearly arbitrary.

Adipose Tissue↗
PubMed1975

The 1971 red tide and its impact on certain reef communities in the mid-eastern Gulf of Mexico.

Effects of the 1971 spring-summer red tide upon mid-eastern Gulf of Mexico patch reef communities are discussed. In situ (SCUBA) observations at widely scattered reef localities between 13-30 m off Sarasota, Florida, both before and after the red tide support the following: 1) under the appropriate environmental conditions, red tides may result in near-complete extirpations of shallow-water (less than 40 m) reef biotas from extensive areas on the inner central-West Florida Shelf), 2) recolonization by certain biotic groups is relatively rapid (e.g., benthic algae and fishes) while that of others (e.g., alcyonarian corals, scleractinian corals, and echinoderms) is slow and may require several years, and 3) seasonal progression as well as true ecological succession following certain red tides may temporarily result in floral and faunal assemblages qualitatively and quantitatively distinctive from those prior to the red tide. It is therefore suggested that certain red tides, particularly those generated beneath pronounced thermoclines, may be previously underestimated phenomena regulating the composition, abundance, and distribution of shallow-water reef biotas in the mid-eastern Gulf of Mexico. It is surmised that the periodic occurrence of these red tides may prevent the evolution of a climax or equilibrium reef community.

Animals↗
PubMed2006

Using continuous GPS and absolute gravity to separate vertical land movements and changes in sea-level at tide-gauges in the UK.

Researchers investigating climate change have used historical tide-gauge measurements from all over the world to investigate the changes in sea-level that have occurred over the last century or so. However, such estimates are a combination of any true sea-level variations and any vertical movements of the land at the specific tide-gauge. For a tide- gauge record to be used to determine the climate related component of changes in sea-level, it is therefore necessary to correct for the vertical land movement component of the observed change in sea-level.In 1990, the Institute of Engineering Surveying and Space Geodesy and Proudman Oceanographic Laboratory started developing techniques based on the Global Positioning System (GPS) for measuring vertical land movements (VLM) at tide-gauges in the UK. This paper provides brief details of these early developments and shows how they led to the establishment of continuous GPS (CGPS) stations at a number of tide-gauges. The paper then goes on to discuss the use of absolute gravity (AG), as an independent technique for measuring VLM at tide-gauges. The most recent results, from CGPS time-series dating back to 1997 and AG time-series dating back to 1995/1996, are then used to demonstrate the complementarity of these two techniques and their potential for providing site-specific estimates of VLM at tide-gauges in the UK.

Climate↗
PubMed2006

Molluscs production associated to lunar-tide cycle: a case study in Paraíba State under ethnoecology viewpoint.

Molluscs have been for a long time a very important food resource for humans. Therefore, oysters, clams, and mussels are highly required at seafood markets. Like any commercial food, it is necessary that molluscs present good quality standards, concerning some criteria such as amount of meat and appearance. In bivalves, condition index or fattening index is considered a satisfactory method for estimating the amount of meat related to the shell cavity. Molluscs gatherers of Paraíba State coast, northeastern Brazil, state that molluscan meat production increases during spring tide (designated by them as maré de lançamento) in opposition to the meat decrease which happens during neap tide (maré de quebramento) (they are designated technically in Portuguese as maré de sizígia and maré de quadratura, respectively). We performed a survey on the production of unha-de-velho or 'oldman'snail' (Tagelus plebeius) caught by molluscs gatherers in the estuary of River Paraíba do Norte, by observing locally their work, applying questionnaires, searching for a possible scientific relation of that molluscs condition to the gatherers empirical statement. Thus, we estimated the molluscs condition index through the method of solids percentage determination. We studied their work and the molluscs condition index during a full lunar-tide cycle. Determinations were carried out between 2nd September and 20th October, 1998, through 20 catches performed to obtain condition index from 400 bivalves. We observed that several biotic and abiotic ecological factors, namely reproduction cycle, biochemical components variations, animal size, and even parasitism, may affect the animal condition index. Despite this aspect, our present results confirmed a high overlapping (80%) of the condition index curve with lunar-tide cycle, in agreement with the gatherers statement. Although we recognize the need for formulating and testing other hypotheses, we consider a priori that the gatherers empirical assertion a unha tá gorda de acordocom a maré ('the "oldman's nail" is fat according to the tide', roughly translating) is justified by the observations here performed when the condition index increased during spring tide and decreased during neap tide.

Animals↗
PubMed1995

Abolition of postprandial alkaline tide in arterialized venous blood of duodenal ulcer patients with cimetidine and after vagotomy.

OBJECTIVE: Alkaline tide is the observed alkalinization of blood and urine after stimulation of gastric acid secretion. In previous studies, we found good correlation between gastric acid output and alkaline tide in arterialized venous blood. METHODS: In the present study, the alkaline tide phenomenon was further investigated in 26 duodenal ulcer patients (seven post-vagotomy) after a test meal, before and after cimetidine pretreatment. RESULTS: Alkaline tide was demonstrated in everyone of the 19 duodenal ulcer nonvagotomized patients but in only two of the seven vagotomized patients; base excess mean rise of 1.05 +/- 0.14 mEq/L/45 min versus -.07 +/- 0.23 mEq/L/45 min (mean +/- SE, p < 0.001). Decrease in alkaline tide after cimetidine was demonstrated in the nonvagotomized group: 1.05 +/- 0.14 mEq/45 min versus -0.03 +/- 0.16 mEq/45 min, before and after cimetidine, respectively (mean +/- SE, p < 0.001). Urinary alkaline tide was demonstrated in only 4/19 and 2/19 of the first group (with and without cimetidine, respectively) and in only 1/7 of the post-vagotomy group. CONCLUSIONS: Our results suggest an association between gastric acid secretion and blood alkaline tide, because both are inhibited by cimetidine or vagotomy.

Adult↗
PubMed2006

Factors affecting outbreaks of high-density Cochlodinium polykrikoides red tides in the coastal seawaters around Yeosu and Tongyeong, Korea.

Red tides caused by the dinoflagellate Cochlodinium polykrikoides occur annually in coastal waters of Korea, causing significant damage. A distinguishing characteristic of C. polykrikoides red tides is that they develop and persist in the open sea, where the water is comparatively clean with little contamination from the shore. We examined the causes of and key nutrients involved in high-density C. polykrikoides red tide outbreaks in the coastal seawaters around Yeosu and Tongyeong, Korea. High-density C. polykrikoides red tides occur in the coastal areas of Geomo Island, where freshwater flows into the sea after heavy rainfall events. Red tides are widespread in years when rainfall is heavy. The maximum concentration of C. polykrikoides and the duration of the red tides increase with increasing rainfall. Adding nitrogen and Seomjin River water to cultures of C. polykrikoides also increases biomass production and cell density of C. polykrikoides remarkably increased after heavy rainfall events. The occurrence of high concentrations of C. polykrikoides along the shores of Yeosu and Tongyeong seems to result from rainfall-initiated inflows of high concentrations of nitrate secondarily, after a conducive physical and chemical open-water environment has been established for C. polykrikoides to spread initially.

Animals↗
PubMed2000

Sublethal effects of Texas brown tide on Streblospio benedicti (Polychaeta) larvae.

The Texas brown tide bloom is noted for a concordant decline in benthic biomass and species diversity. However, the link between harmful effects induced by Texas brown tide and benthos has not been demonstrated. It has been proposed there may be a larval bottleneck, where larvae, but not adults, suffer adverse effects. This study was performed to test the effect of brown tide alga, Aureoumbra lagunensis, on mortality, growth and behavior of Streblospio benedicti larvae. Growth rates and swimming speeds, but not mortality rates, of polychaete larvae were reduced in cultures with brown tide relative to Isochrysis galbana, which is about the same size as brown tide. Results from this research indicate that brown tide does have harmful sublethal effects for one dominant species of meroplanktonic larvae, which could help explain reduced adult population size.

Journal Article↗
PubMed2007

Aerosolized red-tide toxins (brevetoxins) and asthma.

BACKGROUND: With the increasing incidence of asthma, there is increasing concern over environmental exposures that may trigger asthma exacerbations. Blooms of the marine microalgae, Karenia brevis, cause red tides (or harmful algal blooms) annually throughout the Gulf of Mexico. K brevis produces highly potent natural polyether toxins, called brevetoxins, which are sodium channel blockers, and possibly histamine activators. In experimental animals, brevetoxins cause significant bronchoconstriction. In humans, a significant increase in self-reported respiratory symptoms has been described after recreational and occupational exposures to Florida red-tide aerosols, particularly among individuals with asthma. METHODS: Before and after 1 h spent on beaches with and without an active K brevis red-tide exposure, 97 persons >or= 12 years of age with physician-diagnosed asthma were evaluated by questionnaire and spirometry. Concomitant environmental monitoring, water and air sampling, and personal monitoring for brevetoxins were performed. RESULTS: Participants were significantly more likely to report respiratory symptoms after K brevis red-tide aerosol exposure than before exposure. Participants demonstrated small, but statistically significant, decreases in FEV(1), midexpiratory phase of forced expiratory flow, and peak expiratory flow after exposure, particularly among those participants regularly using asthma medications. No significant differences were detected when there was no Florida red tide (ie, during nonexposure periods). CONCLUSIONS: This study demonstrated objectively measurable adverse changes in lung function from exposure to aerosolized Florida red-tide toxins in asthmatic subjects, particularly among those requiring regular therapy with asthma medications. Future studies will assess these susceptible subpopulations in more depth, as well as the possible long-term effects of these toxins.

Adolescent↗
PubMed2004

[Removal efficiency of red tide organisms by modified clay and its impacts on cultured organisms].

Removal efficiencies of Prorocentrum donghaiense (Prorocentrum dentatum) by Hexadecyltrimethylammonium (HDTMA) bromide and organo-clay modified by HDTMA were identified. Moreover the toxicity of the unbound HDTMA and HDTMA plus clay to aquacultural organisms, Penaeus japonicus, was also tested. The results suggested that (1) The unbound HDTMA had an excellent ability to remove the red tide organisms. However, its strong toxicity to Penaeus japonicus would restrict its practical use in red tide control. (2) The toxicity of HDTMA could be remarkably decreased by addition of clay and the organo-clay complex had a good ability to removal red tide organisms. At the same time the availability of organo-clay to remove the red tide of P. donghaiense and Heterosigma akashiwo in the lab-imitated cultures were studied. The results indicated that the organo-clay complex could remove 100% P. donghaiense at the dosage of 0.03 g/L and effectively control H. akashiwo at 0.09 g/L while the survival rate of Penaeus japonicus larvae, which were cultured in the red tide seawater, is kept 100%. According to the results in laboratory, the mesocosm tests (CEPEX) in East China Sea were conducted in April and May of 2003. The removal efficiencies of original clay, organic clay and inorganic clay were compared during the CEPEX tests. The results revealed that both inorganic clay and organic clay could remove red tide organisms more effectively than the original clay.

Aluminum Silicates↗
PubMedDate not supplied

[Presence of red tides along the eastern coast of the Gulf of California].

Records of the occurrence of red tides during the last 24 years in Guaymas and for the last 16 years in Mazatlán, on the coast of the Gulf of California, Mexico are presented here. The results indicate the presence of 4 dominant species in 34 red tides in Guaymas and 9 dominant species in 60 red tides in Mazatlán. The most common species is Mesodinium rubrum, while the toxic one is Gymnodinium catenatum. Noctiluca scintillans and Gonyaulax sp. were also present in Guaymas. In Mazatlán Scrippsiella trocoidea, Prorocentrum dentatum, Ceratium tripos var. ponticum, C. furca, Gymnodinium splendens and Gonyaulax triacantha were also present. Red tides occur frequently during winter in Guaymas and during the late winter and early spring in Mazatlán. Both periods coincide with the upwelling season in the region. The absence of the red tides is related to the "El Niño" phenomenon, which is significant in the Mazatlán area. Ciliates decrease 11.4%, while dinoflagellates increase from 1.6 to 3.8%. The duration period of red tides increase (5.6%) from 3 to 6 days, as compared with the records between 1979 and 1990.

Animals↗
PubMed2002

Effects of a red-tide toxin on fish hearing.

Red tides are formed from blooms of marine algae. Among them, the dinoflagellate ( Karenia brevis) that is responsible for Florida red tides can release many types of natural toxins, which cause massive kills of marine animals, including endangered species, and threaten human health. This study was to investigate whether or not a neurotoxin, brevetoxin-3, purified from Florida red tides affects hearing sensitivity of a teleost fish, the goldfish ( Carassius auratus). LD(50) of the goldfish that were intraperitoneally injected with brevetoxin-3 was 0.068 microg g(-1). Evoked auditory brainstem responses were recorded, and hearing threshold was determined using a correlation method. By comparing thresholds of fish before and after a sublethal-dose injection (0.064 microg g(-1)) of the toxin, we found that brevetoxin-3 significantly reduces auditory sensitivity up to 9 dB at low frequencies (100 Hz and 500 Hz), but not at a high frequency (2,000 Hz). Reduction of hearing sensitivity was recovered within 24 h. To our knowledge, this is the first study showing a natural red-tide toxin causes minor hearing loss in vertebrates. Results of the study indicate that brevetoxin-3 could affect hearing capabilities of marine animals that survived exposure to red tides. Mechanisms of the toxin-induced reduction of hearing sensitivity are discussed.

Acoustic Stimulation↗