The project

Coastal areas are valuable and sensitive environments that are subjected to great anthropogenic pressure due to the high population and industry placed on them. Among these pressures, metal pollution is of priority concern given that these persistent pollutants can reach concentrations in the water column that exceed the levels established to protect sensitive organisms in the ecosystem.

In coastal lagoons, shallow systems that have a reduced exchange with the open sea, metal concentrations can be one or two orders of magnitude higher than in open waters. In addition, these dynamic systems are subjected to physicochemical variations that can alter the biogeochemical cycling of the metals. In particular, singular environmental events such as strong winds cause metal resuspension, torrential rain events provoke the massive entrance of solutes and pollutants, and phytoplankton blooms dramatically increase the concentration of organic matter in the water. These events provoke alterations in the concentration of metals in the water column, as well as in the partition of metals within the particulate and dissolved phase and changes in their speciation. This will have a direct impact in the organisms living in the area, since metal toxicity and bioavailability depends on the chemical speciation of the metals. In particular, dissolved organic matter (DOM) is the most important variable influencing metal speciation and bioavailability in seawater.

However, the effects of DOM on metal bioavailability have not been yet completely unraveled and contrasting results have been reported depending on the metal and organism tested, some showing that DOM protects against metal toxicity and other studies showing the opposite results. The present study was designed to study how the biogeochemical cycling of trace metals in the water column in coastal lagoons is influenced by the cited singular environmental events and how this affects the incorporation of metals by the primary producers, in this case, microalgae, with particular focus on the effect of dissolved organic matter on metal biouptake. Mar Menor lagoon was chosen as a study area since it is a system of great ecological value affected by an important anthropogenic pressure. It receives acid waters from the old mining area specially during raining events, and resuspension of metal-enriched sediments by strong winds and eutrophication events are frequent.

The proposed work combines an intensive field sampling and analytical work (i.e. monthly sampling o water in 10 sites with the objective of establish the biogeochemical cycle of metals under stationary conditions and their alteration by singular environmental events, as well as the bioaccumulation of metals along the food chain) with hypothesis-driven laboratory experiments with phytoplankton (in order to advance our knowledge on the bioavailability of metals in the presence of dissolved organic matter, using both well defined synthetic solutions and natural Mar Menor water samples). This project will substantially contribute to widen our knowledge about the behaviour of metals in coastal areas and to determine how the presence of DOM affects their toxicity, and therefore, the metal concentrations that can be tolerated without posing an excessive risk for the environment. The results obtained will be extrapolated to the other Mediterranean or world coastal lagoon systems with the same characteristics and singularities as the Mar Menor lagoon.

This project is being carried out with the collaboration of the DMMEM project of the IEO-CSIC for monitoring the eutrophication of the Mar Menor.

The general objective of the project is to study how the biogeochemical cycling of trace metals in water is influenced by singular environmental events such as torrential rains, sediment resuspension after high winds or algal blooms and eutrophication events and how this affects the incorporation of metals by the primary producers, in this case, microalgae, with particular focus on the effect of dissolved organic matter on metal biouptake.

This main objective will be reached through several partial objectives:

The methodology proposed to accomplish this project is described following the proposal tasks.