Development and application of a monoclonal-antibody technique for counting Aureococcus anophagefferens, an alga causing recurrent brown tides in the Mid-Atlantic United States

A review of the current and emerging detection methods of marine harmful microalgae

In recent years, the scale and frequency of outbreaks of harmful algal blooms (HABs) have increased year by year due to the intensification of seawater eutrophication and global climate change. HABs have become a global marine ecological and environmental problem, which poses a serious threat to human health, marine ecological security, and economic development. The establishment of detection technology for harmful microalgae is fundamental to the early warning and prevention of HABs. To date, several detection methods have been developed for harmful microalgae, they however lack a unified classification standard. It is difficult to use a reasonable mix of all the developed methods to improve the accuracy of detection results. Here, all of the established detection methods for harmful microalgae were reviewed, including morphological structure-based detection methods, cytochrome-based detection techniques, immunoassays, and nucleic acid-based detection methods. The principles, advantages, and weaknesses of these methods were highlighted. Their application in the detection of harmful microalgae was summarized. Overall, different detection methods are suitable for different purposes. Further development of more accurate, cost-effective, efficient, and rapid detection technology is required in the future. This review is expected to provide a reference for research related to the monitoring of marine environment, early warning of HABs, and the molecular identification of harmful microalgae.

Characteristics of eukaryotic microalgal community and its abiotic influencing factors during brown tide blooms near Qinhuangdao, China

The brown tides caused by the picoplanktonic pelagophyte Aureococcus anophagefferens in the coastal waters of Qinhuangdao, China have occurred periodically since 2009 and exerted deleterious effects on scallop cultivation in the area. In this study, clone libraries were constructed to determine the characteristics of the local eukaryotic microalgae community, and a real-time fluorescent quantitative PCR assay was performed to analyze the temporal and spatial variations in the 18S rDNA copies of A. anophagefferens samples collected in 2012. The results showed that A. anophagefferens was the dominant species in the local eukaryotic microalgae community during the brown tide in June 2012 and accounted for a large fraction of the community. A redundancy analysis (RDA) showed that the decreasing concentration of dissolved inorganic nitrogen (DIN), increasing amount of human aquaculture activities and suitability of spring/summer temperatures for the growth of A. anophagefferens may be the primary causes of the brown tide outbreaks in the Qinghuangdao scallop culture area.

A novel immunofluorescence flow cytometry technique detects the expansion of brown tides caused by Aureoumbra lagunensis to the Caribbean Sea

During the past 3 decades, brown tides caused by the pelagophytes Aureococcus anophagefferens and Aureoumbra lagunensis have caused ecological and economic damage to coastal ecosystems across the globe. While blooms of A. lagunensis had previously been confined to Texas, in 2012, an expansive brown tide occurred on Florida's East Coast, causing widespread disruption within the Indian River and Mosquito Lagoons and generating renewed interest in this organism. A major impediment to detailed investigations of A. lagunensis in an ecosystem setting has been the absence of a rapid and reliable method for cell quantification. The combination of their small size (3 to 5 μm) and nondescript extracellular features makes identification and enumeration of these cells with conventional methods a challenge. Here we report the development of an immunological-based flow cytometry method that uses a fluorescently labeled antibody developed against A. lagunensis. This method is species specific, sensitive (detection limit of 1.5 × 10(3) cells ml(-1)), precise (1% relative standard deviation of replicated samples), and accurate (108% ± 8% recovery of spiked samples) over a wide range of cell concentrations. Furthermore, this method effectively quantifies A. lagunensis in both glutaraldehyde- and formalin-preserved samples, yields a high throughput of samples (∼35 samples h(-1)), and is cost-effective, making it an ideal tool for managers and scientists. This method successfully documented the recurrence of a brown tide bloom in Florida in 2013. Bloom densities were highest in June (>2.0 × 10(6) cells ml(-1)) and spanned >60 km from the Ponce de Leon inlet in the northern Mosquito Lagoon south to Titusville in the Indian River Lagoon. Low levels of A. lagunensis cells were found >250 km south of this region. This method also quickly and accurately identified A. lagunensis as the causative agent of a 2013 brown tide bloom in Guantanamo Bay, Cuba, and thus should prove useful for both quantifying the dynamics of ongoing blooms of A. lagunensis as well as documenting new outbreaks of this harmful alga.

Rapid and label-free cell detection by metal-cluster-decorated carbon nanotube biosensors

In this paper, the use of carbon nanotube biosensors toward alga cell detection was examined. The biosensor devices were fabricated on complete 4 in. wafers by first growing carbon nanotubes (CNTs) and then depositing metal electrodes using a shadow mask. In addition, we decorated the biosensors with metal-clusters resulted in enhancing the sensitivity by 2000-folds and has enabled the detection of streptavidin down to 10 pM concentration. This sensitivity enhancement was attributed to activation of CNT channels due to formation of Schottky junctions between CNTs and metal-clusters. Real-time cell detection has been successfully carried out using the CNT biosensors for two kinds of alga related to brown tides: Aureococcus anophagefferens and BT3. Functionalization of the CNT biosensors with the monoclonal antibody for A. anophagefferens has led to detection at a concentration of 10(4) cells/ml, with sensitivity lower than 10(4) cells/ml projected based on the signal-to-noise ratio of the sensors. Further functionalization with tween 20 led to suppression of non-specific binding of BT3 and enabled label-free and selective detection of A. anophagefferens. These nanobiosensors may find potential applications for environmental monitoring and disease diagnosis.

Immunofluorescence flow cytometry technique for enumeration of the brown-tide alga, Aureococcus anophagefferens

A new immunologically based flow cytometry (IFCM) technique was developed to enumerate Aureococcus anophagefferens, a small pelagophyte alga that is the cause of "brown tides" in bays and estuaries of the mid-Atlantic states along the U.S. coast. The method utilizes a monoclonal antibody conjugated to fluorescein isothiocyanate (FITC-MAb) to label the surface of A. anophagefferens cells which are then detected and enumerated by using a flow cytometer. Optimal conditions for FITC-MAb staining, including solution composition, incubation times, and FITC-MAb concentrations, were determined. The FITC-MAb method was tested for cross-reactivity with nontarget, similarly sized, photoautotrophic protists, and the method was compared to an enzyme-linked immunosorbent assay (ELISA) using the same MAb. Comparisons of the IFCM technique to traditional microscopy enumeration of cultures and spiked environmental samples showed consistent agreement over several orders of magnitude (r(2) > 0.99). Comparisons of the IFCM and ELISA techniques for enumerating cells from a predation experiment showed a substantial overestimation (up to 10 times higher) of the ELISA in the presence of consumers of A. anophagefferens, presumably due to egested cell fragments that retained antigenicity, using the ELISA method, but were not characterized as whole algal cells by the IFCM method. Application of the IFCM method to environmental "brown-tide" samples taken from the coastal bays of Maryland demonstrated its efficacy in resolving A. anophagefferens abundance levels throughout the course of a bloom and over a large range of abundance values. IFCM counts of the brown-tide alga from natural samples were consistently lower than those obtained using the ELISA method and were equivalent to those of the polyclonal immunofluorescence microscopy technique, since both methods discriminate intact cells. Overall, the IFCM approach was an accurate and relatively simple technique for the rapid enumeration of A. anophagefferens in natural samples over a wide range of abundance values (10(3) to 10(6) cells ml(-1)).

Rapid quantification of the toxic alga Prymnesium parvum in natural samples by use of a specific monoclonal antibody and solid-phase cytometry

The increasing incidence of harmful algal blooms around the world and their associated health and economic effects require the development of methods to rapidly and accurately detect and enumerate the target species. Here we describe use of a solid-phase cytometer to detect and enumerate the toxic alga Prymnesium parvum in natural samples, using a specific monoclonal antibody and indirect immunofluorescence. The immunoglobulin G antibody 16E4 exhibited narrow specificity in that it recognized several P. parvum strains and a Prymnesium nemamethecum strain but it did not cross-react with P. parvum strains from Scandinavia or any other algal strains, including species of the closely related genus Chrysochromulina. Prymnesium sp. cells labeled with 16E4 were readily detected by the solid-phase cytometer because of the large fluorescence signal and the signal/noise ratio. Immunofluorescence detection and enumeration of cultured P. parvum cells preserved with different fixatives showed that the highest cell counts were obtained when cells were fixed with either glutaraldehyde or formaldehyde plus the cell protectant Pluronic F-68, whereas the use of formaldehyde alone resulted in significantly lower counts. Immunofluorescence labeling and analysis with the solid-phase cytometer of fixed natural samples from a bloom of P. parvum occurring in Lake Colorado in Texas gave cell counts that were close to those obtained by the traditional method of counting using light microscopy. These results show that a solid-phase cytometer can be used to rapidly enumerate natural P. parvum cells and that it could be used to detect other toxic algae, with an appropriate antibody or DNA probe.

The growing contributions of molecular biology and immunology to protistan ecology: molecular signatures as ecological tools

Modern genetic and immunological techniques have become important tools for assessing protistan species diversity for both the identification and quantification of specific taxa in natural microbial communities. Although these methods are still gaining use among ecologists, the new approaches have already had a significant impact on our understanding of protistan diversity and biogeography. For example, genetic studies of environmental samples have uncovered many protistan phylotypes that do not match the DNA sequences of any cultured organisms, and whose morphological identities are unknown at the present time. Additionally, rapid and sensitive methods for detecting and enumerating taxa of special importance (e.g. bloom-forming algae, parasitic protists) have enabled much more detailed distributional and experimental studies than have been possible using traditional methods. Nevertheless, while the application of molecular approaches has advanced some aspects of aquatic protistan ecology, significant issues still thwart the widespread adoption of these approaches. These issues include the highly technical nature of some of the molecular methods, the reconciliation of morphology-based and sequence-based species identifications, and the species concept itself.

Harmful algal blooms: causes, impacts and detection

Blooms of autotrophic algae and some heterotrophic protists are increasingly frequent in coastal waters around the world and are collectively grouped as harmful algal blooms (HABs). Blooms of these organisms are attributed to two primary factors: natural processes such as circulation, upwelling relaxation, and river flow; and, anthropogenic loadings leading to eutrophication. Unfortunately, the latter is commonly assumed to be the primary cause of all blooms, which is not the case in many instances. Moreover, although it is generally acknowledged that occurrences of these phenomena are increasing throughout the world's oceans, the reasons for this apparent increase remain debated and include not only eutrophication but increased observation efforts in coastal zones of the world. There is a rapidly advancing monitoring effort resulting from the perception of increased impacts from these HABs, manifested as expanding routine coastal monitoring programs, rapid development and deployment of new detection methods for individual species, toxins, and toxicities, and expansion of coastal modeling activities towards observational forecasts of bloom landfall and eventually bloom prediction. Together, these many efforts will provide resource managers with the tools needed to develop effective strategies for the management and mitigation of HABs and their frequently devastating impacts on the coastal environment.