Effects of Cadmium on Growth, Photosynthetic Pigments, Photosynthetic Performance, Biochemical Parameters and Structure of Chloroplasts in the Agarophyte &amp;lt;i&amp;gt;Gracilaria domingensis&amp;lt;/i&amp;gt; (Rhodophyta, Gracilariales)

Rodrigo W. dos Santos,Paulo A. Horta,Marcelo Maraschin,Zenilda L. Bouzon,Éder C. Schmidt,Roberta de P. Martins,Alexandra Latini

doi:10.4236/ajps.2012.38129

Abstract

This paper aimed to evaluate the effects of different concentrations of cadmium on growth rates, photosynthetic pigments, photosynthetic performance, biochemical parameters and structure of chloroplasts in G. domingensis. To accomplish this, apical segments of G. domingensis were cultivated with different concentrations of cadmium, ranging from 100 to 300 μM, over a period of 16 days, and were processed for transmission electron microscopy analysis. The plants exposed to cadmium showed chloroplast alteration, especially degeneration of thylakoids and a decrease in the concentration of photosynthetic pigments, such as chlorophyll a and phycobiliproteins. However, the volume of plastoglobuli increased. As a defense mechanism, the plants treated with cadmium showed an increase in glutathione reductase activity. These results agree with the decreased photosynthetic performance and relative electron transport rate observed after exposure of algae to cadmium. Taken together, these findings strongly indicate that cadmium negatively affects the ultrastructure and metabolism of the agarophyte G. domingensis, thus posing a threat to the economic vitality of this red macroalga.

Highlights

Over the last few years, increasing human population and industrial development have led to an increase of contaminants in aquatic systems [1]
This paper aimed to evaluate the effects of different concentrations of cadmium on growth rates, photosynthetic pigments, photosynthetic performance, biochemical parameters and structure of chloroplasts in G. domingensis
In view of the effects of heavy metals on other species of algae, the present study aimed to evaluate the biological effects of cadmium on the growth, photosynthetic pigments, photosynthetic performance, chloroplast structure and biochemical activities of the red macroalga G. domingensis, a species especially important to the Brazilian economy

Summary

Introduction

Over the last few years, increasing human population and industrial development have led to an increase of contaminants in aquatic systems [1]. Studies reporting the effects of heavy metals on aquatic organisms are currently attracting more attention, those focused on industrial and urban pollution. The contamination of coastal waters with trace metals through sewage and other anthropogenic sources has become a severe problem [2]. Heavy metals, such as lead, copper, cadmium, zinc, and nickel, are among the most common pollutants found in both industrial and urban effluents [3]. Some heavy metals (Cu, Zn, Ni, and Mn) are essential trace elements for photosynthetic organisms; in high concentrations, these metals cause severe toxic effects [4]. Some reports have shown changes in the ultrastructure of the red algae Audouinella savina Agardh [10], Euglena gracilis Klebs [1], and the brown algae Padina gymnospora (Kützing) Sonder [11]

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