The project

Consequences of singular environmental events on the cycle of metals in coastal lagoons and their influence on the incorporation of metals by primary producers.

Summary

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.

Hypothesis

The starting hypothesis is that in highly anthropised coastal areas, such as the Mar Menor Lagoon, the levels of metals in water, under certain extreme environmental conditions, exceed the values established by European directives as maximum values allowed for this type of water, putting at risk the good environmental condition of the ecosystem.

Main Objective

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:

Objective 1

Study the biogeochemical cycle of metals in the water column of the Mar Menor lagoon under stationary conditions (IP: Juan Santos)

Objective 2

Study of the influence of singular environmental events on the stationary cycle of trace metals in the water column of the Mar Menor lagoon (IP: Juan Santos).

Objective 3

Standardization of a robust methodology for the study of short-term Pb and Cu internalization by two marine microalgae (IP: Paula Sánchez).

Objective 4

Study Cu and Pb internalization by phytoplankton in the presence of DOM, competing cations and varying salinities in well defined synthetic solutions (IP: Paula Sánchez). 

Objective 5

Determine metal bioavailability in Mar Menor samples collected under different hydrographic conditions (IP: Paula Sánchez).

Objective 6

Determine the bioaccumulation factor of trace metals along the food chain of the Mar Menor (IP: Juan Santos).

Location

Murcia (Spain)

Sampling stations

Green: Water sample, organic speciation // Purple: Water sample, total metal concentration // Blue: Ports

Methodology

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

Task 1.1. Sampling strategy and campaigns. A quarterly sampling, over one year period, of 10 stations distributed throughout the lagoon will be carried out (Figure 1).

Task 1.2. Total dissolved and particulate trace metal analysis

Task 1.3. Trace metal organic speciation analysis

Task 1.4. Chlorophyll-a determination

Task 1.5. DOM analysis and characterization In collaboration with the researcher X.A. Álvarez-Salgado from the Marine Research Institute (IIM-CSIC).

Task 1.6. Correlation of metals and the rest of variables.

Task 2.1. Sampling strategy and campaigns  Extraordinarily to the quarterly sampling, 3 samplings will be carried out during the annual singular recurring environmental events in the Mar Menor, such as torrential rains at the end of summer or autumn, strong easterly winds that provoke resuspension of sediments and finally algal blooms (Figure 2).

Task 2.2. Analysis of the samples Different analysis will be carried out in the samples determining the same variables as in Tasks 1.2, 1.3, 1.4 and 1.5.

Task 3.1. Optimization of harvesting procedures with minimum impact in cell viability.

Task 3.2. Optimization of the low trace metal culture media for the two phytoplankton species.

Task 3.3. Optimization of short-term uptake experiments.

Task 4.1. Metal internalization experiments with phytoplankton in the presence of DOM.

Task 4.2. Metal internalization experiments in the presence of competing cations at varying salinities.

Task 4.3. Determination of dissolved metal concentrations and metal speciation in experimental solutions.

Task 4.4. Data interpretation and analysis

Task 5.1. Sampling and sample treatment Sampling will be performed as explained in Task 1, in sampling dates and sampling sites representing different hydrographic conditions. These will include three samples affected by the singular environmental events (wind, phytoplankton bloom and strong rain) and another three samples representing a normal situation in different sites of the lagoon.

Task 5.2. Analysis of Cu and Pb speciation, complexation capacity, and DOM characterization.

Task 5.3. Metal internalization experiments with natural samples

Task 5.4. Data intrerpretation and analysis

Task 6.1. Sampling of different organisms

Task 6.2. Analysis of trace metal contents in biota samples

Meet the team