The effects of silica, nitrogen, and phosphorus limitation on the biochemical composition of Cyclotella meneghiniana Kütz: an experimental analysis

The effects of silica, nitrogen, and phosphorus limitation on the amount of cellular lipid, fatty acid, glucan, protein and chlorophyll of Cyclotella meneghiniana Kutz. were investigated in batch and semi-continuous culture experiments. In batch cultures, cells were removed from nutrient-replete media and resuspended in nutrient-deficient media according to a 2(\u273) factorial design in fractional replication. Cells were analyzed 3 and 9 days after transfer to treatment media. Of the 3 nutrients, only silica had a significant effect on a biochemical variable. Silica deficiency caused a significant increase (300%) in the amount of cellular protein. Cellular protein was also significantly different between fractional replicates. In semi-continuous cultures, cells were grown in media with the nutrient under investigation at concentrations lower than necessary for maximum rates of growth. Daily dilution rates of 10, 25, and 50% produced 3 distinct rates of nutrient supply within each of the silica, nitrogen, and phosphorus-stressed experiments. Cellular lipid/glucan ratios significantly decreased (50%) with an increase in silica supply rate. The amount of cellular lipid, glucan, and protein significantly increased (300%) with an increase in nitrogen supply rate. The amounts of cellular lipid and glucan significantly increased (300 and 400%, respectively) with an increase in phosphorus supply rate;Fatty acids of lipid extracted from cells in semi-continuous cultures generally possessed carbon chain lengths of 14 to 24. However, carbon chain lengths of fatty acids from cells in silica-stressed cultures ranged from less than 14 to 18. No distinct differences in diatom fatty acid composition were observed among supply rates within silica-stressed and nitrogen-stessed cultures;The statistical significance of nutrient-limitation effects on cellular biochemical composition varied between batch and semi-continuous culture experiments. The semi-continuous cultures provided constant physiological and growth conditions while batch cultures did not. Therefore, results of semi-continuous cultures were more reliable than results of batch cultures. Discrepancies between results of this study and others were attributed to culture design, biochemical extraction techniques, the scaling factor used to express cellular biochemical composition, and the physiological characteristics of C. meneghiniana

Diatoms New to Ohio and the Laurentian Great Lakes

Author Institution: Department of Biological Sciences, Bowling Green State UniversityEpiphytic diatoms (Bacillariophyta) were collected from three marshes along the southern shoreline of Lake Erie during the summer and fall of 1977. Geographical distributions of 24 taxa new to the state of Ohio are described, and 149 and 34 taxa are reported as new for Lake Erie and the Laurentian Great Lakes, respectively. We attribute the large number of taxa new to the lake to a lack of previous littoral diatom studies, sampling technique, and habitat diversity within the littoral zone

Impacts of a Recurrent Resuspension Event and Variable Phytoplankton Community Composition On Remote Sensing Reflectance

In order to characterize the impact of turbidity plumes on optical and biological dynamics, a suite of environmental parameters were measured in southern Lake Michigan during the springtime recurrent sediment plume. In-water measurements of inherent optical properties (IOPs) were entered into the Hydrolight 4.2 radiative transfer model and the output was compared with measured apparent optical properties (AOPs) across a wide range of optical conditions. Hydrolight output and measured underwater light fields were then used to clarify the effects of the sediment plume on primary production, phytoplankton community composition, and nearshore remote sensing ocean color algorithms. Our results show that the sediment plume had a negligible effect on the spectral light environment and phytoplankton physiology. The plume did not significantly alter the spectral quality of available light and did not lead to light limited phytoplankton populations compared to non-plume conditions. Further, the suspended sediment in the plume did not seriously impact the performance of ocean color algorithms. We evaluated several currently employed chlorophyll algorithms and demonstrated that the main factor compromising the efficacy of these algorithms was the composition of phytoplankton populations. As phycobilin-containing algae became the dominant species, chlorophyll algorithms that use traditional blue/green reflectance ratios were compromised due to the high absorption of green light by phycobilin pigments. This is a notable difficulty in coastal areas, which have highly variable phytoplankton composition and are often dominated by sharp fronts of phycobilin and non-phycobilin containing algae

An improved block matching algorithm for motion estimation invideo sequences and application in robotics

Block Matching is one of the most efficient techniques for motion estimation for video sequences. Metaheuristic algorithms have been used effectively for motion estimation. In this paper, we propose two hybrid algorithms: Artificial Bee Colony with Differential Evolution and Harmony Search with Differential Evolution based motion estimation algorithms. Extensive experiments are conducted using four standard video sequences. The video sequences utilized for experimentation have all essential features such as different formats, resolutions and number of frames which are generally required in input video sequences. We compare the performance of the proposed algorithms with other algorithms considering various parameters such as Structural Similarity, Peak Signal to Noise Ratio, Average Number of Search Points etc. The comparative results demonstrate that the proposed algorithms outperformed other algorithms

How useful is the Making Every Contact Count Healthy Conversation Skills approach for supporting people with musculoskeletal conditions?

Funding: PhD studentship funded by University of Bath and Health Education England. Ethical approvals were granted by the NHS Health Research Authority (REC reference: 20/HRA/2919) and University of Bath’s Research Ethics Approval Committee for Health (reference: EP 19/20 057).Peer reviewedPublisher PD

Observations on the Tube-Dwelling Diatom Navicula Tripunctata var. Schizonemoides (V.H.) Patr. Using Light and Electron Microscopy

The valve morphology of specimens from four different collections, each identified as Navicla tripunctata var. schizonemoides (V.H.) Patr., was examined by light and electron microscopy. Light microscopy revealed little variation between populations. Variability in the valve shape and striae arrangement within a population, however, was observed. Observations by electron microscopy revealed structures common to other lineolate Navicula and pennate diatoms. The continued use of electron microscopy as a supplement to light microscopy for proper interpretation of a diatom\u27s valve morphology is stressed. Notes on the ecology of this taxon are made where appropriate

Spring Phytoplankton Photosynthesis, Growth, and Primary Production and Relationships to a Recurrent Coastal Sediment Plume and River Inputs in Southeastern Lake Michigan

[1] A recurrent coastal sediment plume (RCP) is an episodic event in the southern basin of Lake Michigan that typically coincides with the spring diatom bloom. Strong winter storm activity during El Nino conditions in 1998 resulted in a large and intense RCP event. Consistently higher values of the light-saturated rate of photosynthesis, P-max(B), were observed in spring 1998 compared to 1999 and 2000. Higher values of P-max(B) in 1998 appeared to be related to increased availability of phosphorus, as evidenced by significant correlations of P-max(B) with soluble reactive phosphorus (SRP). Light-saturated growth rates were also significantly correlated with SRP concentrations. These findings were consistent the view that the RCP was a source of enrichment. However, incubation experiments involving lake water enriched with sediments showed relatively small increases in growth and photosynthetic parameters, while enrichments with river water exhibited elevated rates. This result, along with increased levels of river discharge in 1998 and high levels of dissolved phosphorus in river water, supported the view that riverine inputs rather than the RCP were responsible for the higher photosynthetic parameters and growth seen for coastal margin assemblages. Despite the higher levels of P-max(B) in 1998, model analyses revealed that reduced light availability resulting from the intense RCP event constrained phytoplankton growth rates and primary production during this season and apparently suppressed the development of a typical spring bloom. These findings indicate a potential for reduced ecosystem productivity in response to extreme storm events, the frequency of which may increase with projected long-term climate changes

Detection of Harmful Algal Blooms Using Photopigments and Absorption Signatures: A Case Study of the Florida Red Tide Dinoflagellate, Gymnodinium breve

The utility of photopigments and absorption signatures to detect and enumerate the red tide dinoflagellate, Gymnodinium breve, was evaluated in laboratory cultures and in natural assemblages. The carotenoid, gyroxanthindiester, was an adequate biomarker for G. breve biomass; water‐column concentrations corresponded with cell standing crops and chlorophyll a concentrations during bloom events in Sarasota Bay, Florida. Unlike other carotenoids, the relative abundance of gyroxanthin‐diester did not change throughout a range of physiological states in culture and the gyroxanthin‐diester: chlorophyll a ratio exhibited little variability in a natural assemblage during bloom senescence. Stepwise discriminant analysis indicated that wavelengths indicative of in vivo absorption by accessory chlorophylls and carotenoids could correctly discern spectra of the fucoxanthin‐containing G. breve from spectra of peridinin‐containing dinoflagellates, a diatom, a haptophyte, and a prasinophyte. With the use of a similarity algorithm, the increasing contribution of G. breve was discerned in absorption spectra (and corresponding fourth‐derivative plots) for hypothetical mixed assemblages. However, the absorption properties of chlorophyll c‐containing algae vary little among taxa and it is difficult to discern the contribution of accessory chlorophylls and carotenoids caused by cell packaging. Therefore, the use of absorption spectra alone may not identify the contribution of a chlorophyll c‐containing taxon to the composite spectrum of a mixed assemblage. This difficulty in distinguishing among spectra can be minimized by using the similarity algorithm in conjunction with fourth‐derivative analysis

Base excision repair apurinic/apyrimidinic endonucleases in apicomplexan parasite Toxoplasma gondii

DNA repair is essential for cell viability and proliferation. In addition to reactive oxygen produced as a byproduct of their own metabolism, intracellular parasites also have to manage oxidative stress generated as a defense mechanism by the host. The spontaneous loss of DNA bases due to hydrolysis and oxidative DNA damage in intracellular parasites is great, but little is known about the type of DNA repair machineries that exist in these early-branching eukaryotes. However, it is clear, processes similar to DNA base excision repair (BER) must exist to rectify spontaneous and host-mediated damage in Toxoplasma gondii. Here we report that T. gondii, an opportunistic protozoan pathogen, possesses two apurinic/apyrimidinic (AP) endonucleases that function in DNA BER. We characterize the enzymatic activities of Toxoplasma exonuclease III (ExoIII, or Ape1) and endonuclease IV (EndoIV, or Apn1), designated TgAPE and TgAPN, respectively. Over-expression of TgAPN in Toxoplasma conferred protection from DNA damage, and viable knockouts of TgAPN were not obtainable. We generated an inducible TgAPN knockdown mutant using a ligand-controlled destabilization domain to establish that TgAPN is critical for Toxoplasma to recover from DNA damage. The importance of TgAPN and the fact that humans lack any observable APN family activity highlights TgAPN as a promising candidate for drug development to treat toxoplasmosis