Influence of elevated river flow on hypoxia occurrence, nutrient concentration and microbial dynamics in a tropical estu
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Influence of elevated river flow on hypoxia occurrence, nutrient concentration and microbial dynamics in a tropical estuary Choon Weng Lee & Joon Hai Lim & Pei Li Heng & Nurul Fitrah Marican & Kumaran Narayanan & Edmund Ui Hang Sim & Chui Wei Bong
Received: 30 March 2020 / Accepted: 20 September 2020 # Springer Nature Switzerland AG 2020
Abstract We sampled the Klang estuary during the inter-monsoon and northeast monsoon period (July– Nov 2011, Oct–Nov 2012), which coincided with higher rainfall and elevated Klang River flow. The increased freshwater inflow into the estuary resulted in water column stratification that was observed during both sampling periods. Dissolved oxygen (DO) dropped below 63 μM, and hypoxia was observed. Elevated river flow also transported dissolved inorganic nutrients, chlorophyll a and bacteria to the estuary. However, Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10661-020-08625-3) contains supplementary material, which is available to authorized users.
bacterial production did not correlate with DO concentration in this study. As hypoxia was probably not due to in situ heterotrophic processes, deoxygenated waters were probably from upstream. We surmised this as DO correlated with salinity (R 2 = 0.664, df = 86, p < 0.001). DO also decreased with increasing flushing time (R2 = 0.556, df = 11, p < 0.01), suggesting that when flushing time (> 6.7 h), hypoxia could occur at the Klang estuary. Here, we presented a model that related riverine flow rate to the post-heavy rainfall hypoxia that explicated the episodic hypoxia at Klang estuary. As Klang estuary supports aquaculture and cockle culture, our results could help protect the aquaculture and cockle culture industry here.
C. W. Lee : J. H. Lim : P. L. Heng : N. F. Marican : C. W. Bong Laboratory of Microbial Ecology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
Keywords Klang estuary . Peninsular Malaysia . Hypoxia . Dissolved oxygen dynamics . Klang River flow rate
C. W. Lee (*) : J. H. Lim : C. W. Bong Institute of Ocean and Earth Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia e-mail: [email protected]
Introduction
J. H. Lim Institute for Advanced Studies, University of Malaya, 50603 Kuala Lumpur, Malaysia K. Narayanan School of Science, Monash University Malaysia, Bandar Sunway, 47500 Subang Jaya, Selangor, Malaysia E. U. H. Sim Faculty of Resource Sciences and Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia
Estuaries are among the most productive aquatic habitats but are characterized by extreme physical, chemical and biological gradients (McLusky 1993). Estuaries are also vulnerable to environmental changes especially eutrophication, urbanisation and climate change (Ashley et al. 2005; Middelburg and Levin 2009; Howarth et al. 2011). Eutrophication in the form of increasing nitrogenous input has resulted in increased occurrences of hypoxia and harmful algal blooms (Rabalais
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