Long-term exposure to environmentally relevant concentrations of
pesticides has deleterious effects on shellfish

Date:
December 8, 2021
Source:
Portland State University
Summary:
Exposure to chronic, environmentally relevant concentrations of
pesticides registered for use in forest management had adverse
effects on the soft-shell clam, Mya arenaria.



FULL STORY ========================================================================== According to a study recently published in the journal Science of
the Total Environment, exposure to chronic, environmentally relevant concentrations of pesticides registered for use in forest management
had adverse effects on the soft-shell clam, Mya arenaria.


==========================================================================
The article, co-authored by researchers at Portland State University and
the U.S. Geological Survey, monitored the clams in laboratory conditions
over 90 days. During that time, they exposed clams to pesticides at concentrations that may occur in their natural estuarine ecosystems due
to runoff from upstream applications.

The researchers monitored the effects of the pesticides atrazine,
hexazinone, indaziflam, and bifenthrin, individually and in combination,
on the soft-shell clams' shell growth, condition, feeding rates,
mortality, and contaminant uptake with collection periods occurring every thirty days of the study. The data indicate exposure to some chemicals
caused a high mortality rate, both individually and in combination,
"which was surprising due to the low concentrations we used in the study"
said lead author Allie Tissot.

Additionally, the research team found accumulation of the compounds in
the tissue of the shellfish and reduced clam condition and feeding.

According to the study's authors, the findings underscore the need for
a more comprehensive understanding of how pesticides used upstream of
estuarine and marine ecosystems impact aquatic species and ecosystem
health. Forest managers commonly use three of the pesticides examined
in the study to control the expansion of unwanted species that threaten
forest lands; some of these compounds are also used in farming Christmas
trees and managing vegetation in public right-of-ways. Runoff and spray
drift then transports the pesticides into waterways that carry them
downstream, where it enters coastal transition zones.

The study is novel in examining the effects of pesticide exposure over a
long period and at environmentally relevant concentrations. According to Tissot, "studying the long-term effects of these compounds in combination
and at levels that our lab has detected in coastal transition zone
ecosystems is critical to our understanding of how forestry management practices may impact these culturally and economically important
ecosystems. This is an important data gap to fill as research on these compounds' toxicity typically focuses on individual compound effects at
high concentrations to determine lethality, which while necessary for understanding compound toxicity, can miss sub-lethal effects that can have
long term impacts on these systems. " Alexandra Tissot a graduate student
at Portland State University, co-authored the article, with Portland
State faculty members Elise Granek, Ann Thompson, and former PhD student
Kaegan Scully-Engelmeyer. Michelle Hladik and Patrick Moran of the U.S Geological Survey also contributed. Oregon Sea Grant funded the research.

========================================================================== Story Source: Materials provided by Portland_State_University. Original
written by Shaun McGillis. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Alexandra G. Tissot, Elise F. Granek, Anne W. Thompson, Michelle L.

Hladik, Patrick W. Moran, Kaegan Scully-Engelmeyer. The silence of
the clams: Forestry registered pesticides as multiple stressors
on soft-shell clams. Science of The Total Environment, 2021;
152053 DOI: 10.1016/ j.scitotenv.2021.152053 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211208161130.htm

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