INVESTIGADORES
Carina Beatriz Lange
Investigadora Asociada Línea 2
Silvio Pantoja Gutiérrez
Director COPAS Sur-AustralInvestigador Titular Línea 5
We study fish scales as a proxy of fish abundance and preservation biases together with phosphorusfrom fish remains (Pfish) in a sediment core
retrieved off Callao, Peru (12 110S,771420 W; waterdepth¼179m; core length ¼ 52cm). We interpret our results as a function of changing redoxconditions based on ratios of redox sensitive trace elements (Cu/Al, Mo/Al, Ni/Al, Zn/Al, V/Al),terrigenous indicators (Fe in clays, Ti, Al), and biogenic proxies (CaCO3, biogenic opal, total nitrogen,organic carbon, barite Ba). The core covers roughly 700 years of deposition, based on 210Pb activitiesextrapolated downcore and 14C dating at selected intervals. Our fish-scale record is dominated byanchovy (Engraulis ringens) scales followed by hake (Merluccius gayii) scales.The core presented an abrupt lithological change at 17cm (corresponding to the early 19th century).Above that depth, it was laminated and was more organic-rich (10–15% organic carbon) than below,where the core was partly laminated and less organic-rich (o10%). The lithological shift coincides withabrupt changes in dry bulk density and in the contents of terrigenous and redox-sensitive traceelements, biogenic proxies, and fish scales. The remarkable increase in redox-sensitive trace elements inthe upper 17cm of the core suggests more reducing conditions when compared with deeper and olderhorizons, and is interpreted as an intensification of the oxygen minimum zone off Peru beginning in theearly 19th century. Higher fish-scale contents and higher Pfish/Ptotal ratios were also observed within theupper 17cm of the core. The behavior of biogenic proxies and redox-sensitive trace elements wassimilar; more reduced conditions corresponded to higher contents of CaCO3, Corg, total nitrogen and fishscales, suggesting that these proxies might convey an important preservation signal
