Concentrations of trace elements in sea urchins and macroalgae commonly present in Sargassum beds: implications for trophic transfer

Abstract

The aim of the study was to evaluate the dynamic of cadmium, lead, copper, zinc, and iron among lower trophic levels, sea urchins and macroalgae. Diets and isotopic values were used in combination to explore trophic positions and potential transference of metals from primary producers to consumers. Concentrations of trace elements were measured in two species of sea urchin (Tripneustes depressus and Eucidaris thouarsii) and nine macroalgae that are usually used as food in four Sargassum beds, one of which is close to a phosphorite mine. Specimens were collected when Sargassum fronds were at their greatest (winter) and lowest (summer) abundance. Highest concentrations of Cd, and Cu in both urchin species were recorded in winter at the site near the phosphorite mine. Concentrations of Pb in T. depressus were below the detectable limit, whereas E. thouarsii, which in addition to a high concentration of Pb, had high amounts of Cu and Zn. Gut content analysis, indicates that the diet of both sea urchins at the four sites and two collection dates is mainly macroalgae. The δ15N isotopic values in sea urchins in a typical Sargassum bed were in good agreement with a diet dominated by macroalgae, with T. depressus having herbivorous habits and E. thouarsii having omnivorous habits in this environment. We found macroalgae important in the dynamics of metals in food webs, potentially contributing to transferring Cd, Cu, and Zn to key invertebrate species, such as sea urchins, indicating connectivity of food webs and ecological structuring of marine environments.

Cadmium, Lead, Copper, Zinc, and Iron Concentration Patterns in Three Marine Fish Species from Two Different Mining Sites inside the Gulf of California, Mexico

“…The presence of cadmium in some localities of the Gulf of California has been attributed to natural land-based sources, most likely supplied by weathering and transport from phosphorite-containing rocks [ 65 ] that may also contain lead [ 13 ]. In the same sites where fish were caught in LAP, the urchins Tripneustes depressus (30.9 ± 5.5 µg g −1 ) and Eucidaris thouarsii (38.3 ± 2.3 µg g −1 ) had cadmium concentrations nearly 3-fold higher than peak levels in macroalgae [ 66 ]. Also, high lead concentrations have been reported in other species ( Table 1 ) from the same sites in LAP; these include concentrations up to 38.6 ± 4.2 µg g −1 in the sea urchin Eucidaris thouarsii attributed to the consumption of crustose coralline ( Lithophyllum ) or articulated coralline ( Amphiroa ) algae or other organisms such as mollusks, barnacles, filamentous, or turf-forming algae attached to macroalgae or rocks [ 61 , 66 ].…”

“…In the same sites where fish were caught in LAP, the urchins Tripneustes depressus (30.9 ± 5.5 µg g −1 ) and Eucidaris thouarsii (38.3 ± 2.3 µg g −1 ) had cadmium concentrations nearly 3-fold higher than peak levels in macroalgae [ 66 ]. Also, high lead concentrations have been reported in other species ( Table 1 ) from the same sites in LAP; these include concentrations up to 38.6 ± 4.2 µg g −1 in the sea urchin Eucidaris thouarsii attributed to the consumption of crustose coralline ( Lithophyllum ) or articulated coralline ( Amphiroa ) algae or other organisms such as mollusks, barnacles, filamentous, or turf-forming algae attached to macroalgae or rocks [ 61 , 66 ]. Therefore, we expected to find higher cadmium and lead levels in LAP, linked to phosphorite mining.…”

“…By displacing zinc from these proteins, cadmium becomes non-bioavailable; thus, metallothioneins also act as detoxifiers by decreasing the bioavailability of non-essential elements, thereby reducing their toxicity [ 79 ]. Accordingly, only the fraction of a trace element that is bioavailable in an organism will be biomagnified in its predators [ 66 ]. Therefore, mollusks and echinoderms may accumulate a higher amount of cadmium relative to the fish feeding on them [ 80 ].…”

Macroalgae from two coastal lagoons of the Gulf of California as indicators of heavy metal contamination by anthropogenic activities

“…Marine organisms are commonly used as bioindicators of trace metal contamination (Volterra & Conti, 2000; Hernández-Almaraz et al ., 2016). Algae and molluscs are among the organisms most used for this purpose (Rainbow, 1995).…”

Bacterial flora associated with commercial Octopus maya captured in the Yucatan Peninsula, Mexic

“…Microorganisms can have both positive and negative effects on food industry systems. Many are used as probiotic agents, quality indicators and flavor enhancers (de la Cruz-Leyva et al, 2015) or as elements in a variety of biotechnological processes (Hernández et al, 2016). Others negatively affect product quality by acting as deteriorating agents.…”