Can pesticides, copper and seasonal water temperature explain the seagrass Zostera noltei decline in the Arcachon bay?

Abstract

Dwarf eelgrasses (Zostera noltei) populations have decreased since 2005 in Arcachon Bay (southwest France). Various stressors have been pointed out, however the role of xenobiotics like pesticides or copper (Cu) and of parameters like water temperature warming have not yet been explored. To determine their impact, Z. noltei individuals were collected in a pollution-free site and transferred to the laboratory in seawater microcosms. This dwarf eelgrass was exposed to a pesticide cocktail and copper, alone or simultaneously, at temperatures (10°C, 20°C, 28°C) representative of different seasons. After a two-week contamination, leaf growth, leaf bioaccumulation of Cu, and differential expression of target genes were studied. Eelgrasses bioaccumulated Cu regardless of the temperature, with reduced efficiency in the presence of the Cu and pesticide cocktail at the two higher temperatures. High temperature also exacerbated the effect of contaminants, leading to growth inhibition and differential gene expression. Mitochondrial activity was strongly impacted and higher mortality rates occurred. Experimental results have been confirmed during field survey. This is the first report on the impacts on Z. noltei of pesticides and Cu associate to temperature.

Dynamics of the seagrass Zostera noltei in a shallow Mediterranean lagoon exposed to chemical contamination and other stressors

“…At physiology level, there are just a few studies that examine the combined effect of trace metal elements and pesticides on Zostera sp. and they are limited to the effects on photosynthesis (Macinnis- Ng and Ralph, 2004;Gamain et al, 2017). However, in the present study,…”

Easy-to-Use Sensors for Field Monitoring of Copper Contamination in Water and Pesticide-Sprayed Plants

“…A high concentration of Cu 2+ ions was shown to alter membrane permeability and cause inhibition of shoot and root growth, chlorosis, necrosis, and leaf discoloration . It was also established that Cu 2+ negatively effects photosynthesis in dwarf eelgrass . Increased levels of Cu 2+ can also significantly affect human health.…”

“…10 It was also established that Cu 2+ negatively effects photosynthesis in dwarf eelgrass. 11 Increased levels of Cu 2+ can also significantly affect human health. Excessive Cu 2+ in the body can lead to heightened oxidative stress by increasing superoxide levels 12 and inhibition of mitochondrial dehydrogenase enzymes in vitro and in vivo.…”

Environmental factors controlling biomass development of seagrass meadows of Zostera noltei after a drastic decline (Arcachon Bay, France)

“…These contaminants mainly affect seagrasses by altering photosynthesis processes (Chesworth et al, 2004;Gao et al, 2011;Nielsen & Dahllöf, 2007). Furthermore, high temperatures (28°C) enhance the effect of contaminants (herbicides + copper), leading to growth inhibition and differential gene expression (Gamain et al, 2017).…”