AEI 11:671-684 (2019)  -  DOI: https://doi.org/10.3354/aei00340

ABSTRACT: Human activities can elevate coastal levels of dissolved inorganic nitrogen (DIN). As macroalgae readily absorb and accumulate DIN, the elemental (total N and C:N ratio) composition of their tissues is less affected by temporal fluctuations compared to more direct measures of DIN concentration. Additionally, their isotopic (δ¹⁵N) composition can reflect that of the source, which could potentially be used to identify between multiple effluent sources. To investigate whether macroalgal ‘bioindicators’ could map and distinguish between multiple effluents, 2 species of macroalgae (Chondrus crispus and Palmaria palmata) were deployed in a bay containing a salmon farm and sewage treatment facility. Both species exhibited high total N and low C:N ratio near the salmon farm and sewage facility. However, the elemental composition of C. crispus was influenced over a greater distance than that of P. palmata. Differences were also observed between their isotopic composition, as C. crispus indicated that the salmon farm and sewage facility had distinct δ¹⁵N signatures, whereas values of δ¹⁵N in P. palmata had not changed after 10 d incubation in the field. Interestingly, the distinct isotopic signals observed in C. crispus were likely a result of higher DIN concentrations at the salmon farm, which likely caused macroalgae to fractionate and form biomass lighter in δ¹⁵N. Overall, this study suggests that macroalgal bioindicators can monitor and identify between multiple effluent sources, which could provide a useful tool for coastal management. However, some species of macroalgae may make more effective bioindicators than others, and the mechanisms underlying their fractionation require further investigation.

KEY WORDS: Aquaculture · δ¹⁵N · Isotope · Macroalgae · Nitrogen · Salmon · Sewage · Wastewater

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Cite this article as: Howarth LM, Filgueira R, Jiang D, Koepke H and others (2019) Using macroalgal bioindicators to map nutrient plumes from fish farms and other sources at a bay-wide scale. Aquacult Environ Interact 11:671-684. https://doi.org/10.3354/aei00340 Export citation Share:    Facebook - - linkedIn