Trace elements in Antarctic penguins and the potential role of guano as source of recycled metals in the Southern Ocean

Penguins dominate the Antarctic avifauna. As key animals in the Antarctic ecosystem, they are monitored to evaluate the ecological status of this pristine and remote region and specifically, they have been used as effective bioindicators suitable for long-term monitoring of metals in the Antarctic environment. However, studies about the role of this emblematic organism could play in the recycling of trace metals (TMs) in the Antarctic ecosystem are very limited. In this study we evaluate, using the peer review research articles already published and our own findings, the distribution of metals (i.e., Ca, Fe, Al, Na, Zn, Mg, Cu, K, Cd, Mn, Sr, Cr, Ni, Pb, Hg, V, Ba, Co, La, Ag, Rb, Hf, Sc, Au and Cs) and metalloids (As and Sb), measured in different biotic matrices, with emphasis on guano, of the Chinstrap (Pygoscelis antarcticus), Adelie (Pygoscelis adeliae) and Gentoo (Pygoscelis papua) penguins. Regarding bioactive metals, the high concentrations (mu g g(-1) dry weight) of Cu (2.0 +/- 1.4) x 10(2), Fe (4.1 +/- 2.9) x 10(2), Mn (30 +/- 34) and Zn (210 +/- 90) reported in the guano from all the penguin species studied including our data, are of the same order of magnitude as those reported for whale feces (mu g g(-1) dry weight): Cu (2.9 +/- 2.4) x 10(2), Fe (1.5 +/- 1.4) x 10(2), Mn (28 +/- 17) and Zn (6.2 +/- 4.3) x 10(2), and one order of magnitude higher than the metal contents in krill (mu g g(-1) dry weight) of Cu (10.2 +/- 5.5), Fe (24 +/- 29) and Zn (13.5 +/- 1.7). This suggest that penguin's excretion products could be an important source of these essential elements in the surface water, with an estimated annual release on a breeding season for Cu, Fe, Mn, Zn respectively of 28, 56, 4 and 29 tons, for the Chinstrap, Adelie and Gentoo penguins. The results provide evidence on the potential influence of penguins recycling TMs in the surface layer of the water column.This research has been funded by the Spanish Government projects PIMETAN (ref. RTI2018-098048-B-I00) and PINGUFOR (ref. CTM201564720-R). E. Sparaventi is supported by the Spanish FPI grant (Ref: PRE2019-089679) and A. Rodriguez-Romero is supported by the Spanish grant, Juan de la Cierva Incorporacion (Ref: IJC2018-037545-I). We thank I. Carribero and M.C. Agullo for their support with the instrumental and methodological analyses. This research is part of POLARCSIC research initiative. Permissions to work and collect guano samples in the study area were granted by the Spanish Polar Committee. We thank the hospitality of the Spanish Antarctic Stations "Gabriel de Castilla" and "Juan Carlos I" and the transportation by the RV Hesperides. We also thank the logistic support by the Marine Technological Unit of CSIC