Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Civil and Environmental Engineering | en_US |
| dc.contributor.advisor | Jin, Ling (CEE) | en_US |
| dc.creator | Zhang, Li | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13865 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Ecological pattern of microalgal communities and associated risks in coastal ecosystems | en_US |
| dcterms.abstract | The occurrence of Harmful algal blooms (HABs) is a prominent environmental issue that pose significant threats to marine ecosystems, seafood safety, and human health. Over recent decades, the increasing frequency, intensity, and global distribution of HABs have underscored the urgency of understanding their ecological dynamics and associated risks. Beyond natural seawater, human-induced substrates such as plastics also provide a novel habitat, “the plastisphere” (a microecosystem with plastics as the matrix) for microalgal communities in the coastal ecosystem. However, the ecological dynamics and associated risks of microalgal communities in both seawater and plastisphere, as well as the associations between these two habitats, remain largely unexplored. Moreover, the absence of a specific and comprehensive sequence database for harmful and toxic microalgae has hindered the accurate identification and monitoring of these species. To address these gaps, this study developed the harmful and toxic microalgae database (HTMaDB) to reveal the ecological dynamics and microalgae-associated risks in the coastal ecosystem. | en_US |
| dcterms.abstract | We constructed the HTMaDB, a comprehensive resource that consolidates 1,346 18S full-length reference sequences from public repositories. A total of 79 harmful and toxic species were identified in the typical coastal city Hong Kong surface seawaters with the application of curated database. The results revealed that dinoflagellates and diatoms constitute most of the toxic and harmful taxa, respectively. Seasonal variations in algal community structures were observed. Specifically, temperature was found to be the primary factor shaping seasonal patterns of toxic algal communities, with increased toxic species abundance during the dry season. The dominance of causative taxa in this period was consistent with the higher prevalence of algal toxins, supporting the reliability of the database. These findings highlight the potential for escalating risks associated with toxic microalgae under a warming climate, as differential responses of specific species to temperature fluctuations contribute to the complexity of HAB occurrences. Species such as Alexandrium spp., Dinophysis spp., Prorocentrum spp., and Karenia spp. were identified as the primary toxin producers, underscoring the critical need for targeted management strategies to mitigate their ecological and health impacts. | en_US |
| dcterms.abstract | In addition to exploring the ecological patterns of algal communities in the surface seawater, this study further investigated the ecological dynamics and associated risks of microalgal communities within the plastisphere. Plastic pollution has become a global environmental challenge, with millions of tonnes of plastic waste entering the oceans annually. The plastisphere provides a durable and hydrophobic surface that facilitates the colonization and transport of microorganisms, including harmful and toxic algae. By analyzing 92 paired samples of plastic debris and ambient water collected from coastal ecosystems, this research revealed that the plastisphere selectively harbors distinct algal communities compared to the surrounding waters. The relative abundance of Chlorophyta increased significantly, while that of Dinoflagellata decreased within the plastisphere. Furthermore, the plastisphere exhibited significantly higher alpha diversity, indicating its potential to shelter unique or alien microalgal taxa transported from upstream systems. These results suggest that the plastisphere serves as a microhabitat that enables the selective assembly, enrichment, and transport of harmful and toxic algae across ecosystems. | en_US |
| dcterms.abstract | The study also found that harmful and toxic diatoms, such as Pseudo-nitzschia cuspidata, Chaetoceros socialis, and Skeletonema marinoi, thrived within the plastisphere. Some harmful algal taxa were exclusively detected on plastic debris but absent from the surrounding water, highlighting the potential of plastics to act as vectors for the transport of harmful algae. Environmental factors such as temperature and salinity were positively associated with the abundance of risk-associated microalgae, whereas pH exhibited a negative correlation. These findings demonstrate that plastic pollution not only alters the composition and diversity of microalgal communities but also amplifies the ecological risks associated with HABs by facilitating the spread and enrichment of harmful algae and their toxins. The potential for plastics to carry harmful algal species across marine ecosystems poses significant challenges for managing HAB risks in the context of increasing plastic pollution. | en_US |
| dcterms.abstract | This integrated study bridges critical knowledge gaps by systematically investigating the pelagic microalgal communities in the coastal ecosystem. By developing HTMaDB, this research provides a valuable resource for improving the accuracy and efficiency of HAB monitoring and identification. The findings highlight the role of environmental factors, particularly temperature, in driving the seasonal dynamics of toxic algal communities and emphasize the impact of climate change on HAB risks. Additionally, the investigation into the plastisphere offers novel insights into how plastic debris assembled a distinct microalgal community compared to the seawater community and increased the risks associated with harmful and toxic algae. These findings contribute to a comprehensive ecological view of pelagic microalgal communities in the coastal ecosystem. | en_US |
| dcterms.extent | 211 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.LCSH | Microalgae | en_US |
| dcterms.LCSH | Algal blooms -- Toxicology | en_US |
| dcterms.LCSH | Toxic marine algae | en_US |
| dcterms.LCSH | Plastic marine debris | en_US |
| dcterms.LCSH | Hong Kong Polytechnic University -- Dissertations | en_US |
| dcterms.accessRights | open access | en_US |
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