Interactions of trace metals, DOM, and particles in the Amazon estuary and associated plume as key processes for trace metal and DOM fluxes into the Atlantic, Cruise No. M147, April 19 - May 21, 2018, Las Palmas (Gran Canaria) - Belém (Brazil) (English)

METEOR Cruise M147 (Amazon - GEOTRACES) was set to assess in detail the role of the Amazon River towards the input of trace metals and dissolved organic matter (DOM) into the Atlantic Ocean as well as the isotopic characterization of water masses and mixing processes. The cruise is an official process study for the internationally coordinated GEOTRACES program (www.geotraces.org). The main research topic is to determine the distribution and speciation of trace elements along the salinity gradients in the mixing zone of the Amazon River estuary and its freshwater plume in order to quantify their biogeochemical cycling, the riverine contribution to open the ocean metal budgets, and its interaction with DOM and particulate matter. The trace metal flux to the ocean will likely be enhanced by complexation with DOM, which competes with colloidal coagulation and sedimentation. Within this frame, important factor to be considered are trace metal associations with physically different size fractions of matter (truly dissolved, organic and inorganic colloids, particles) along the salinity gradient between the river and the ocean. Therefore, a variety of filters including ultrafiltration were used to separate the different fractions. The cruise followed the Pará, as well as the Amazon south and north outflow, along the salinity transect to the open Atlantic Ocean. Furthermore, sampling continued northwards of the Amazon plume, along the coast line of Brazil and French Guiana. In total, 74 standard stainless-steel CTD-rosette profiles, 15 trace-metal clean CTD profiles, 10 single GoFlo-bottles, 60 pumps for radium samples, 107 surface samples with the towed fish and 22 multicorer stations were conducted. With this, the river water and seawater endmembers as well as the entire mixing zone within the exclusive economic zones of Brazil and French Guiana between 6°N and 1°S were covered by sampling.