Effects of Wastewater Effluent on the Sex Composition of Winter Flounder in Massachusetts Bay

Wastewater treatment plant effluent enters marine and freshwater ecosystems, introducing pharmaceuticals into bays, estuaries, and rivers. It is important to understand how pharmaceuticals may be of concern when they settle into these sensitive systems. When the Massachusetts Water Resources Authority (MWRA) first began talks in the early 1990s about moving the wastewater outfall site from Boston Harbor to its present location in Massachusetts Bay, there were concerns raised about negative effects to fish and other marine species. This is true especially since the outfall is surrounded by many eco-diverse regions like Stellwagen Bank National Marine Sanctuary, Cape Cod Bay Ocean Sanctuary and North and South Essex Ocean Sanctuaries. MWRA yearly monitoring results reveal an increasingly greater proportion of female winter flounder in Massachusetts Bay. One of their sampling locations furthest from the outfall is yielding some of the highest rates of female winter flounder, suggesting that the outfall may not be the cause. Are pharmaceuticals and personal care products (PPCPs) in effluent, or more specifically active pharmaceutical ingredients (APIs), causing the declining sex ratio? Or are other more natural factors, such as changes in water temperature, contributing to the problem? APIs enter wastewater systems through several means, but most commonly through urine and feces from individuals taking medications. Other sources are also responsible for contributing to the problem, such as from hospitals, improper disposal of medication into toilets and sinks, as well as agricultural runoff (i.e. antibiotics from farm animals). APIs are currently not tested at sampling locations by any of these agencies. In order to understand possible population effects from APIs in effluent, it is important to examine the geographic locations of individual fish (from the sampling data) in relation to their sex and distance from the outfall. This research asked the question: how is winter flounder sex ratio composition tied to proximity to the Deer Island Wastewater Treatment Plant (DIWWTP) outfall site in Massachusetts Bay? The research tested the hypothesis that distance from the effluent outfall predicts sex ratio variation. Sampling data on the Gulf of Maine (GOM) winter flounder (Pseudopleuronectes americanus) is available through the National Marine Fisheries Service/ Northeast Fisheries Science Center (NMFS NEFSC), Massachusetts Division of Marine Fisheries (DMF), and MWRA. Data from these agencies provide thousands of GPS coordinates on the species and their corresponding biological data. Sex and maturity are captured during NEFSC and DMF sampling and provide important details on the health and future outlook for the GOM winter flounder stock. Results revealed that sample points <10 miles and 10-20 miles from the outfall have experienced a significant increase in the proportion of female flounder. NEFSC and DMF winter flounder in size groups 29 cm and 30 cm show a 13% increase in females from the baseline (1980-2000) to the post-diversion periods (2001-2017). In order to control possible risk factors in the future, state and federal policies should include requirements on testing pharmaceutical compounds in drinking water and wastewater. Currently, the EPA does not regulate concentrations of pharmaceuticals in drinking or waste water. Policies should be enacted and enforced before irreversible damage is caused to marine and freshwater ecosystems.