Masculinization of Eastern Mosquitofish (Gambusia) and Exposure to Pulp and Paper Discharge: Diminished Responses Following Mill Process Modifications

Abstract

Abstract The abnormal induction of anal fin elongation (masculinization) in female Gambusia was first reported in the 1980s for Florida streams receiving pulp and paper effluents. Although these early reports indicated masculinization responses that were similar to the complete development of a gonopodium (male secondary sex structure), additional evaluations throughout the 1990s demonstrated significant reductions in this response. These historic data suggested that mill process modifications may have been responsible for the reduced masculinization responses. The objective of the current study was to utilize Georgia Pacifics Palatka Mill to monitor a series of mill process modifications and their effects on masculinization responses in Mosquitofish (Gambusia). Gambusia were collected from upstream, discharge, and downstream sites in the Palatka Mill receiving stream (Rice Creek) and masculinization was evaluated. Collections were conducted annually during 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2008, and 2009, before and after a series of modifications which included: conversion to elemental chlorine free bleaching, conversion of secondary treatment to aerobic degradation, reduction of in-mill black liquor losses, addition of condensate stripping, reduction in water usage from 136 to 83 million litres per day (36 to 22 million gallons per day), installation of new brown stock washers, and oxygen delignification. Masculinization responses were evaluated using the anal fin index (ratio or anal fin rays 4 and 6). Reductions in this masculinization response were observed gradually across 1999 through 2009, with an absence of response in female Gambusia during 2004, 2006, and 2008 to 2009. These data indicate that pulp and paper mill upgrades and process modifications have resulted in the elimination of this biological response in Gambusia.