Evaluation of trace elements in feathers of young kelp gull Larus dominicanus along the coast of Santa Catarina, Brazil

Highlights

• Seabirds are top chain predators and accumulate trace elements.

• Marine pollution affected by metals can be monitored through accumulation in seabirds.

• The monitoring of trace elements in coastal zone is an important tool to environmental management.

• Age and environmental conditions influence the process of bioaccumulation of trace elements in marine organisms.

Abstract

Seabirds are used as bioindicators of marine ecosystems, especially for quantifying and tracking pollution sources. The objective of this study was to evaluate the contamination in feathers of young kelp gulls by lead (Pb), chromium (Cr), mercury (Hg) and zinc (Zn) on three islands of southern Brazil. The highest values for Pb (2.1310 μg g⁻¹) and Hg (0.0010 μg g⁻¹) were observed in Lobos. Zn was common in all samples with a median around 41.7487 μg g⁻¹ and Cr values were below the quantification limit (0.0300 μg g⁻¹). The Kruskal-Wallis test indicated significant differences in Pb (H = 21.84; p < 0.05) and Zn (H = 958.80; p < 0.05), but no differences were observed in Cr (H = 3.08; p < 0.05) and Hg (H = 3.0; p < 0.05). This study was important to show the impact of trace element pollutants on the seabird communities and oceans.

Introduction

The presence of metals in marine ecosystems is related to natural processes (e.g., rock weathering and soil leaching), but urbanization and industrialization are the main anthropogenic sources of trace elements threatening the health of these environments on both a local and large scale (Furness and Monaghan, 1987; Kennish, 1996; Förstner and Wittmann, 1981). One of the main problems is contamination by polycyclic aromatic hydrocarbons (Celino and Queiroz, 2006). Elevated levels of zinc (Zn) and cadmium (Cd) of industrial origins can also be found along with magnesium (Mg) contamination from urban stormwater drainage, which can alter the natural cycles of these elements (Barcellos et al., 1991; Marins et al., 2004; Scherer et al., 2015).

In this context, chemical pollution is a growing issue for ocean ecosystems, where apex predators bioaccumulate persistent chemical pollutants such as non-essential trace elements. The trophic position is, thus, a key aspect when assessing the impacts of environmental pollution on the oceans (Moura et al., 2018a). At low concentrations, trace metals such as copper (Cu), iron (Fe), manganese (Mn) and Zn contribute to the development of organisms, but non-essential metals such as Cd, chromium (Cr), lead (Pb) and mercury (Hg) are potentially toxic, especially to seabirds (Furness and Monaghan, 1987; Burger and Gochfeld, 1992). Seabirds can be affected by Hg contamination and this element may work as an important stress factor culminating in high mortality when these birds are in a condition of poor health (Fort et al., 2015).

Organisms can be contaminated via several routes such as respiration, skin contact but mainly through feeding (Burger and Gochfeld, 2002; Burger and Gochfeld, 2004), and the level of contamination is aggravated through bioaccumulation and biomagnification. Thus, seabirds can be used as indicators of environmental quality (Furness and Monaghan, 1987; Walsh, 1990; Burger, 1993; Burger and Gochfeld, 2001; Burger and Gochfeld, 2004; Ikemoto, 2005; Barbieri, 2009; Costa et al., 2013) by reflecting ecosystem health and are known as ocean sentinels (Boersma et al., 2001). In this context, non-invasive methods of acquiring samples, such as feather collection, have been successfully used in biomonitoring studies focused on the analysis of metals (Denneman and Douben, 1993). The trace elements accumulate in these structures, where they bind to proteins during feather formation (Burger and Gochfeld, 2002). One positive aspect of using feathers is this method does not cause injury to birds and they can quickly regenerate again.

Because they are represented throughout the trophic chain, seabirds are vulnerable to environmental contamination (Burger, 1993; Metcheva et al., 2005; Siciliano et al., 2005; Ruiz, 2008; Burger et al., 2000); thus, they have been used to monitor changes at the individual (acute effects) and populational (chronic effects) levels (Arias et al., 2007). By acting as trackers of contamination, seabirds also make it possible to diagnose the temporal and geographic patterns of oil spills (Furness and Camphuysen, 1997; Wiese and Ryan, 2003; Garcia-Borboroglu et al., 2006).

Half the global population is distributed along coastal regions (Hinrichsen and Robey, 2000; Fleming et al., 2006), which affects the natural balance of these areas (Förstner and Wittmann, 1981; Hax, 2000). In this context, the Santa Catarina coast, which accounts for 39% of the total area of the state of Santa Catarina, concentrates approximately 68% of the entire population of the state, which threatens the balance of this ecosystem (Lopes and Dias, 1996). This is because it receives inputs from rivers that, together with continental drainage, carry pollutants and put the marine environment at risk (Furness and Monaghan, 1987; Schreiber and Burger, 2001; Burger and Gochfeld, 2004).

This study evaluated the trace element (Cr, Pb, Zn and Hg) contaminations in the feathers of young Larus dominicanus captured on three coastal islands of the state of Santa Catarina, Brazil. The results were important to understand this species as a bioindicator of pollution in environment.