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Article: Long-term and seasonal changes in nutrients, phytoplankton biomass, and dissolved oxygen in deep bay, Hong Kong

TitleLong-term and seasonal changes in nutrients, phytoplankton biomass, and dissolved oxygen in deep bay, Hong Kong
Authors
KeywordsDeep Bay
Dissolved oxygen
Eutrophication
Hong Kong
Nutrients
Phytoplankton biomass
Sewage
Issue Date2010
PublisherSpringer New York LLC. The Journal's web site is located at http://www.springer.com/environment/journal/12237
Citation
Estuaries And Coasts, 2010, v. 33 n. 2, p. 399-416 How to Cite?
AbstractDeep Bay is a semienclosed bay that receives sewage from Shenzhen, a fast-growing city in China. NH 4 is the main N component of the sewage (>50% of total N) in the inner bay, and a twofold increase in NH 4 and PO 4 concentrations is attributed to increased sewage loading over the 21-year period (1986-2006). During this time series, the maximum annual average NH 4 and PO 4 concentrations exceeded 500 and 39 μM, respectively. The inner bay (Stns DM1 and DM2) has a long residence time and very high nutrient loads and yet much lower phytoplankton biomass (chlorophyll (Chl) <10 μg L -1 except for Jan, July, and Aug) and few severe long-term hypoxic events (dissolved oxygen (DO) generally >2 mg L -1) than expected. Because it is shallow (̃2 m), phytoplankton growth is likely limited by light due to mixing and suspended sediments, as well as by ammonium toxicity, and biomass accumulation is reduced by grazing, which may reduce the occurrence of hypoxia. Since nutrients were not limiting in the inner bay, the significant long-term increase in Chl a (0. 52-0. 57 μg L -1 year -1) was attributed to climatic effects in which the significant increase in rainfall (11 mm year -1) decreased salinity, increased stratification, and improved water stability. The outer bay (DM3 to DM5) has a high flushing rate (0. 2 day -1), is deeper (3 to 5 m), and has summer stratification, yet there are few large algal blooms and hypoxic events since dilution by the Pearl River discharge in summer, and the invasion of coastal water in winter is likely greater than the phytoplankton growth rate. A significant long-term increase in NO 3 (0. 45-0. 94 μM year -1) occurred in the outer bay, but no increasing trend was observed for SiO 4 or PO 4, and these long-term trends in NO 3, PO 4, and SiO 4 in the outer bay agreed with those long-term trends in the Pearl River discharge. Dissolved inorganic nitrogen (DIN) has approximately doubled from 35-62 to 68-107 μM in the outer bay during the last two decades, and consequently DIN to PO 4 molar ratios have also increased over twofold since there was no change in PO 4. The rapid increase in salinity and DO and the decrease in nutrients and suspended solids from the inner to the outer bay suggest that the sewage effluent from the inner bay is rapidly diluted and appears to have a limited effect on the phytoplankton of the adjacent waters beyond Deep Bay. Therefore, physical processes play a key role in reducing the risk of algal blooms and hypoxic events in Deep Bay. © 2009 Coastal and Estuarine Research Federation.
Persistent Identifierhttp://hdl.handle.net/10722/124010
ISSN
2015 Impact Factor: 2.659
2015 SCImago Journal Rankings: 1.107
ISI Accession Number ID
Funding AgencyGrant Number
University Grants Council of Hong KongAoE/P-04/0401
Funding Information:

Financial support for this research was provided by the University Grants Council of Hong Kong AoE project (AoE/P-04/0401). We thank the Hong Kong Government EPD for permitting us to use their water quality monitoring data for this publication.

References

 

DC FieldValueLanguage
dc.contributor.authorXu, Jen_HK
dc.contributor.authorYin, Ken_HK
dc.contributor.authorLee, JHWen_HK
dc.contributor.authorLiu, Hen_HK
dc.contributor.authorHo, AYTen_HK
dc.contributor.authorYuan, Xen_HK
dc.contributor.authorHarrison, PJen_HK
dc.date.accessioned2010-10-19T04:32:51Z-
dc.date.available2010-10-19T04:32:51Z-
dc.date.issued2010en_HK
dc.identifier.citationEstuaries And Coasts, 2010, v. 33 n. 2, p. 399-416en_HK
dc.identifier.issn1559-2723en_HK
dc.identifier.urihttp://hdl.handle.net/10722/124010-
dc.description.abstractDeep Bay is a semienclosed bay that receives sewage from Shenzhen, a fast-growing city in China. NH 4 is the main N component of the sewage (>50% of total N) in the inner bay, and a twofold increase in NH 4 and PO 4 concentrations is attributed to increased sewage loading over the 21-year period (1986-2006). During this time series, the maximum annual average NH 4 and PO 4 concentrations exceeded 500 and 39 μM, respectively. The inner bay (Stns DM1 and DM2) has a long residence time and very high nutrient loads and yet much lower phytoplankton biomass (chlorophyll (Chl) <10 μg L -1 except for Jan, July, and Aug) and few severe long-term hypoxic events (dissolved oxygen (DO) generally >2 mg L -1) than expected. Because it is shallow (̃2 m), phytoplankton growth is likely limited by light due to mixing and suspended sediments, as well as by ammonium toxicity, and biomass accumulation is reduced by grazing, which may reduce the occurrence of hypoxia. Since nutrients were not limiting in the inner bay, the significant long-term increase in Chl a (0. 52-0. 57 μg L -1 year -1) was attributed to climatic effects in which the significant increase in rainfall (11 mm year -1) decreased salinity, increased stratification, and improved water stability. The outer bay (DM3 to DM5) has a high flushing rate (0. 2 day -1), is deeper (3 to 5 m), and has summer stratification, yet there are few large algal blooms and hypoxic events since dilution by the Pearl River discharge in summer, and the invasion of coastal water in winter is likely greater than the phytoplankton growth rate. A significant long-term increase in NO 3 (0. 45-0. 94 μM year -1) occurred in the outer bay, but no increasing trend was observed for SiO 4 or PO 4, and these long-term trends in NO 3, PO 4, and SiO 4 in the outer bay agreed with those long-term trends in the Pearl River discharge. Dissolved inorganic nitrogen (DIN) has approximately doubled from 35-62 to 68-107 μM in the outer bay during the last two decades, and consequently DIN to PO 4 molar ratios have also increased over twofold since there was no change in PO 4. The rapid increase in salinity and DO and the decrease in nutrients and suspended solids from the inner to the outer bay suggest that the sewage effluent from the inner bay is rapidly diluted and appears to have a limited effect on the phytoplankton of the adjacent waters beyond Deep Bay. Therefore, physical processes play a key role in reducing the risk of algal blooms and hypoxic events in Deep Bay. © 2009 Coastal and Estuarine Research Federation.en_HK
dc.languageengen_HK
dc.publisherSpringer New York LLC. The Journal's web site is located at http://www.springer.com/environment/journal/12237en_HK
dc.relation.ispartofEstuaries and Coastsen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.rightsCoastal and Estuarine Research Federationen_HK
dc.subjectDeep Bayen_HK
dc.subjectDissolved oxygenen_HK
dc.subjectEutrophicationen_HK
dc.subjectHong Kongen_HK
dc.subjectNutrientsen_HK
dc.subjectPhytoplankton biomassen_HK
dc.subjectSewageen_HK
dc.titleLong-term and seasonal changes in nutrients, phytoplankton biomass, and dissolved oxygen in deep bay, Hong Kongen_HK
dc.typeArticleen_HK
dc.identifier.emailLee, JHW: hreclhw@hku.hken_HK
dc.identifier.authorityLee, JHW=rp00061en_HK
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1007/s12237-009-9213-5en_HK
dc.identifier.scopuseid_2-s2.0-77952242901en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-77952242901&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume33en_HK
dc.identifier.issue2en_HK
dc.identifier.spage399en_HK
dc.identifier.epage416en_HK
dc.identifier.eissn1559-2731en_HK
dc.identifier.isiWOS:000275424300014-
dc.publisher.placeUnited Statesen_HK
dc.description.otherSpringer Open Choice, 01 Dec 2010-
dc.identifier.scopusauthoridXu, J=7407002498en_HK
dc.identifier.scopusauthoridYin, K=7101985944en_HK
dc.identifier.scopusauthoridLee, JHW=36078318900en_HK
dc.identifier.scopusauthoridLiu, H=8726071200en_HK
dc.identifier.scopusauthoridHo, AYT=23667369600en_HK
dc.identifier.scopusauthoridYuan, X=23669442900en_HK
dc.identifier.scopusauthoridHarrison, PJ=9533159800en_HK
dc.identifier.citeulike5872096-

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