How the tailings of the Fundão Dam impacted the photosynthetic metabolism and viability of pollen grains of Canavalia rosea

The collapse of the Fundão dam in Mariana municipality, Minas Gerais state, Brazil in November 2015, released approximately 35–60 million m3 of iron ore tailings into the environment. These tailings were transported into the Doce river, and reached the southeastern coast of Brazil, an area formed by fragments of Restinga. The following were evaluated at four sampling stations with different spatial distributions along the coast to the north and south of the mouth of the Doce River in April 2019: (a) the concentration of essential chemical elements and metalloids (pseudo-total) in the soil close to plants of Canavalia rosea, (b) the concentration of essential chemical elements and heavy metals (pseudo-total) in leaf tissue from plants of C. rosea, (c) chlorophyll fluorescence transients in the leaves, and (d) the viability of pollen grains from flowers of C. rosea. The lowest viability for pollen grains in the different environments under study were found in plants from Aldeia do Coco in São Mateus municipality, Espirito Santo state. Changes in photosynthetic parameters related to photochemical performance, such as the fall in the quantum yield of photosystem I, correlated with the presence of boron and arsenic, and with the dramatic reduction in the viability of pollen grains at Aldeia do Coco and the Conceição da Barra Environmental Protection Area. Over time, this change may have a negative impact on genetic diversity in populations of C. rosea, and threatens the survival and maintenance of the species in such environments. The results from the coastal vegetation of the areas affected by the rupture of the Fundão dam clearly reinforce the need to incorporate biological diversity into monitoring programs to assess the environmental health of coastal systems, considering that the patterns of metals and contamination can vary between and within taxons.