Using algal biomass-phosphorus (P) relationships and nutrient limitation theory to evaluate the adequacy of P water quality criteria for regulated monsoon rivers and reservoirs

ABSTRACT

Different P criteria have been set for lotic and lentic waters where the latter had stricter criteria than the former. The binary P criteria have been developed due to differences in limnological features and this helps avoid unneeded costs with stricter criteria for flowing waters that normally have lower potential of algal blooms. However, if different criteria are warranted, the responses of Chl a to TP and TN:TP ratio should vary distinctively between rivers and reservoirs. Contrary to these predictions, inconsistent and statistically indistinguishable variations have been observed between the two types of waterbody in Chl a yield per unit TP. Additionally, there was no significant difference in the strength of relationship between Chl a and TN:TP ratio between waterbody types, although the mass ratio of TN to TP was significantly higher in reservoirs than in rivers. Hence, the data suggest that there is no scientifically defensible reason that lotic and lentic waters require different TP standards and specifically that lentic waters do not necessarily require stricter P criteria. A more holistic and nuanced approach would aid in developing revised or new TP criteria in which water quality issues can be addressed scientifically as well as pragmatically.

KEYWORDS:

• Phosphorus
• nitrogen
• chlorophyll a
• monsoon
• water quality criteria

Acknowledgements

I would like to express my gratitude to Andrew Rodusky and Robert Danehy for insightful manuscript comments and thoughtful editorial assistance, and Robert Kröger for valuable advice. I also wish to acknowledge the staffs of Korea Rural Community Corporation and Korea Hydro & Nuclear Power Co., Ltd. for shared data, and National Institute of Environmental Research and Korea Water Resources Corporation for stimulating conversations. Previous research participation with support from the Korean Ministry of Environment's Water Environmental Policy Bureau helped motivate some of the ideas presented here. I am indebted to the anonymous referees for constructive reviews.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes on contributor

Hong-Suk Koh is an ecologist with sub-disciplines background in community ecology and ecosystem ecology. He is interested in advancing the knowledge and understanding of population and community dynamics, and ecosystem processes to help predict the ecological consequences of environmental change and enhance management and conservation efforts.

ORCID

Hong-Suk Koh http://orcid.org/0000-0002-1705-9194