Detection and Quantification of the Harmful Dinoflagellate Margalefidinium polykrikoides (East Asian Ribotype) in the Coastal Waters of China

The dynamics of red Noctiluca scintillans in the coastal aquaculture areas of Southeast China

Noctiluca scintillans (NS) adds an aesthetic appeal to many coastal areas because of their bioluminescence. An intense bloom of the red NS frequently occurs in the coastal aquaculture region of Pingtan Island in Southeastern China. However, when NS exceeds in abundance, it causes hypoxia which has devastating impacts on the aquaculture. This study was conducted in the Southeastern part of China with an aim to examine the relationship between the profusion of NS and its impacts on marine environment. Samples from four stations on Pingtan Island were collected for 12 months (January to December 2018) and were later analyzed in laboratory against five parameters, namely temperature, salinity, wind speed, dissolved oxygen, and chlorophyll a. Results showed that the NS blooms were particularly active during the months of May and June in the Pingtan Island area. The seawater temperatures during that time were recorded between 20 and 28.8 °C indicating the optimum survival temperature for NS. The NS bloom activity ceased above 28.8 °C. A principal component analysis (PCA) indicated that the richness of NS was positively associated with temperature and salinity, whereas there was a significant reverse correlation between NS accumulation and wind speed. NS is a heterotrophic dinoflagellate and relies on the predation of algae for reproduction; therefore, a significant correlation was observed between NS abundance and chlorophyll a concentration, and an inverse correlation was observed between NS and phytoplankton abundance. Additionally, red NS growth was observed immediately following the diatom bloom, suggesting that phytoplankton, temperature, and salinity are the essential factors in the evolution, progression, and termination of NS growth.

Harmful Algae Impacting Aquatic Organisms: Recent Field and Laboratory Observations

Algal blooms formed by some phytoplankton species can produce toxins or alter environmental conditions that can affect aquatic organisms and water quality, with impacts on the aquaculture and fisheries industries that can pose a risk to public health [...].

A fast and accurate method for specific detection and quantification of the bloom-forming microalgae Karlodinium veneficum in the marine environment

Karlodinium veneficum is a toxic benthic globally distributed dinoflagellate which has direct impacts on human health and the environment. Early and accurate detection of this harmful algal bloom-forming species could be useful for potential risks monitoring and management. In the present work, a real-time PCR targeting the internal transcribed spacer ribosomal DNA region for the specific detection and absolute quantification of K. veneficum was designed. Then, the assay conditions were adjusted and validated. The developed qPCR was highly specific for the target species and displayed no cross-reactivity with closely related dinoflagellates and/or other microalgal species commonly distributed along the Tunisian coast. Its lowest detection limit was 5 rDNA copies per reaction, which is often considered satisfying. qPCR assay enumeration accuracy was evaluated using artificially inoculated environmental samples. The comparison of the cell abundance estimates obtained by qPCR assay with the theoretical estimates showed no statistically significant difference across a range of concentrations. We suggest that the qPCR approach developed in the present study may be a valuable tool to investigate the distribution and seasonal dynamics of K. veneficum in marine environments.