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Article: Real time observations of coastal algal blooms by an early warning system

TitleReal time observations of coastal algal blooms by an early warning system
Authors
KeywordsDiatoms
Dinoflagellates
Dissolved oxygen
Early warning system
Field observation
Harmful algal blooms
Red tide
Species selection
Issue Date2005
PublisherAcademic Press. The Journal's web site is located at http://www.elsevier.com/locate/ecss
Citation
Estuarine, Coastal And Shelf Science, 2005, v. 65 n. 1-2, p. 172-190 How to Cite?
AbstractIn eutrophic sub-tropical coastal waters around Hong Kong, phytoplankton or unicellular microalgae can grow rapidly to very high concentrations under favourable environmental conditions. These harmful algal blooms (HABs) have led to massive fish kills, hypoxia, and beach closures. However, to date the causality and mechanism of coastal algal blooms are still poorly understood. A remotely controlled autonomous real time field monitoring system has been developed to continuously track the changes in chlorophyll fluorescence, dissolved oxygen and other hydro-meteorological variables at two representative mariculture zones. The system can give an alarm when a bloom is detected, so that timely manual water quality sampling can be carried out to supplement the telemetric data. During 2000-2003, the system has successfully tracked 19 algal blooms. In the shallow weakly flushed coastal water (depth 7-10 m, tidal current 5-19 cm s-1), the bloom is short-lived, typically lasting a few days to over a week, with chlorophyll and DO concentrations in the range of 20-40 mg m-3 and 2-15 g m-3, respectively. It is found that: (1) the chlorophyll concentration is strongly correlated with its past values in the previous week, suggesting an auto-regressive type of algal dynamics; (2) the dissolved oxygen can reach highly super-saturated levels (12 g m-3) during a diatom bloom, and decreases to below 4 g m-3 at the tail of the growth phase; (3) in contrast, a dinoflagellate bloom is characterized by a much more pronounced vertical structure. Diel vertical migration and aggregation to dense layers are clearly observed. Significant dissolved oxygen consumption is associated with the migration, resulting in DO drops by as much as 6 g m -3 during the bloom; (4) the predominance of diatoms and dinoflagellates at the two sites can be explained in terms of the different hydrographic and nutrient conditions (the N:P ratio). Net algal growth rate, sinking and swimming velocities are derived from the in situ bloom data. The 4-year high frequency data set provides a basis for development of models for forecast of harmful algal blooms. © 2005 Elsevier Ltd. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/71499
ISSN
2015 Impact Factor: 2.335
2015 SCImago Journal Rankings: 1.094
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorLee, JHWen_HK
dc.contributor.authorHodgkiss, IJen_HK
dc.contributor.authorWong, KTMen_HK
dc.contributor.authorLam, IHYen_HK
dc.date.accessioned2010-09-06T06:32:33Z-
dc.date.available2010-09-06T06:32:33Z-
dc.date.issued2005en_HK
dc.identifier.citationEstuarine, Coastal And Shelf Science, 2005, v. 65 n. 1-2, p. 172-190en_HK
dc.identifier.issn0272-7714en_HK
dc.identifier.urihttp://hdl.handle.net/10722/71499-
dc.description.abstractIn eutrophic sub-tropical coastal waters around Hong Kong, phytoplankton or unicellular microalgae can grow rapidly to very high concentrations under favourable environmental conditions. These harmful algal blooms (HABs) have led to massive fish kills, hypoxia, and beach closures. However, to date the causality and mechanism of coastal algal blooms are still poorly understood. A remotely controlled autonomous real time field monitoring system has been developed to continuously track the changes in chlorophyll fluorescence, dissolved oxygen and other hydro-meteorological variables at two representative mariculture zones. The system can give an alarm when a bloom is detected, so that timely manual water quality sampling can be carried out to supplement the telemetric data. During 2000-2003, the system has successfully tracked 19 algal blooms. In the shallow weakly flushed coastal water (depth 7-10 m, tidal current 5-19 cm s-1), the bloom is short-lived, typically lasting a few days to over a week, with chlorophyll and DO concentrations in the range of 20-40 mg m-3 and 2-15 g m-3, respectively. It is found that: (1) the chlorophyll concentration is strongly correlated with its past values in the previous week, suggesting an auto-regressive type of algal dynamics; (2) the dissolved oxygen can reach highly super-saturated levels (12 g m-3) during a diatom bloom, and decreases to below 4 g m-3 at the tail of the growth phase; (3) in contrast, a dinoflagellate bloom is characterized by a much more pronounced vertical structure. Diel vertical migration and aggregation to dense layers are clearly observed. Significant dissolved oxygen consumption is associated with the migration, resulting in DO drops by as much as 6 g m -3 during the bloom; (4) the predominance of diatoms and dinoflagellates at the two sites can be explained in terms of the different hydrographic and nutrient conditions (the N:P ratio). Net algal growth rate, sinking and swimming velocities are derived from the in situ bloom data. The 4-year high frequency data set provides a basis for development of models for forecast of harmful algal blooms. © 2005 Elsevier Ltd. All rights reserved.en_HK
dc.languageengen_HK
dc.publisherAcademic Press. The Journal's web site is located at http://www.elsevier.com/locate/ecssen_HK
dc.relation.ispartofEstuarine, Coastal and Shelf Scienceen_HK
dc.subjectDiatomsen_HK
dc.subjectDinoflagellatesen_HK
dc.subjectDissolved oxygenen_HK
dc.subjectEarly warning systemen_HK
dc.subjectField observationen_HK
dc.subjectHarmful algal bloomsen_HK
dc.subjectRed tideen_HK
dc.subjectSpecies selectionen_HK
dc.titleReal time observations of coastal algal blooms by an early warning systemen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0272-7714&volume=65&spage=172&epage=190&date=2005&atitle=Real+time+observations+of+coastal+algal+blooms+by+an+early+warning+systemen_HK
dc.identifier.emailLee, JHW: hreclhw@hku.hken_HK
dc.identifier.emailWong, KTM: ken0wong@hku.hken_HK
dc.identifier.authorityLee, JHW=rp00061en_HK
dc.identifier.authorityWong, KTM=rp00073en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.ecss.2005.06.005en_HK
dc.identifier.scopuseid_2-s2.0-25144515838en_HK
dc.identifier.hkuros118041en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-25144515838&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume65en_HK
dc.identifier.issue1-2en_HK
dc.identifier.spage172en_HK
dc.identifier.epage190en_HK
dc.identifier.isiWOS:000232643700016-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridLee, JHW=36078318900en_HK
dc.identifier.scopusauthoridHodgkiss, IJ=7006614647en_HK
dc.identifier.scopusauthoridWong, KTM=24315177100en_HK
dc.identifier.scopusauthoridLam, IHY=6603726924en_HK
dc.identifier.citeulike4252582-

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