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Marine Ecology Progress Series

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MEPS 478:71-86 (2013)  -  DOI: https://doi.org/10.3354/meps10170

Pond aquaculture effluents traced along back-reef waters by standard water quality parameters, δ15N in suspended matter and phytoplankton bioassays

Lucia S. Herbeck1,*, Daniela Unger1,2

1Leibniz Center for Tropical Marine Ecology, 28359 Bremen, Germany
2Present address: DESY Deutsches Elektronen-Synchrotron, Forschungszentrum der Helmholtz-Gemeinschaft,
22607 Hamburg, Germany

ABSTRACT: Despite the enormous growth in aquaculture in recent years, little is known of the impact of effluents from large-scale pond agglomerations on tropical coastal ecosystems. The aim of the present study was to evaluate the dispersal and ecological impact of effluents from fish and shrimp ponds along 3 seagrass-covered back-reef areas on Hainan Island, tropical China, with pond areas in their hinterland differing in extent (Yelin: 0.04 km2; Qingge: 2.4 km2; Changqi: 8.7 km2). Concentrations of dissolved and particulate nitrogen, chlorophyll a (chl a) and stable nitrogen isotopes of ammonium (δ15N-NH4+), nitrate (δ15N-NO3-) and suspended matter (δ15N-TSM) were used to trace pond effluents along transects perpendicular to the shore. Additionally, δ15N-TSM and chl a samples were taken from a phytoplankton bioassay experiment, during which offshore surface water was incubated in dialysis bags at stations along these transects. High nutrient concentrations, particularly ammonium, in combination with high chl a (~10 µg l-1) and elevated chl a levels in the bioassays after incubation indicate eutrophication of the effluent-exposed back-reef areas Qingge and Changqi, with decreasing intensity in the offshore direction. We report the first δ15N-NH4+ of pond effluents which were as high as 17‰. Consequently, elevated δ15N values in TSM (5 to 12‰) and a δ15N increase from <7 up to 14‰ over time in the phytoplankton bioassays specified pond effluents as the predominant nutrient source. The effluents affect the entire back-reef areas over a distance of at least 2.5 km from shore. Our results show that analysis of δ15N in phytoplankton bioassays is a powerful bioindicator for tracing pond-derived nutrient dispersal and eutrophication effects.


KEY WORDS: Aquaculture · Shrimp- and fish-pond effluents · Nitrogen stable isotopes · δ15N · Phytoplankton bioassay · Back-reef area · Eutrophication · China


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Cite this article as: Herbeck LS, Unger D (2013) Pond aquaculture effluents traced along back-reef waters by standard water quality parameters, δ15N in suspended matter and phytoplankton bioassays. Mar Ecol Prog Ser 478:71-86. https://doi.org/10.3354/meps10170

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