Contaminant-related thyroid disruption in wild fish in Southern and Northern California: cause and effect evaluations

Kevin Kelley, California State University, Long Beach
Jeff Armstrong, Orange County Sanitation District
Jesus Amador Reyes, Pacific Coast Environmental Conservancy

In all vertebrate animals including humans, thyroid hormones are critical for normal development and growth, and they have multiple other effects essential to a healthy physiology and survival generally.  Disruption of this endocrine system poses a significant concern for wildlife such as fish.  The objective of this study is to evaluate selected urban ocean and estuarine environments of California for the degree to which thyroid endocrine disruption is occurring in wild fish species (since preliminary studies have indicated this) and to understand the underlying mechanisms and causes.

Results from this study are expected to shed light on the affected targets of contaminants in the thyroid endocrine system, which is important for determining the mechanism(s) of action of the operative environmental agents as well as to identify possible specific bioassays (biomarkers) that can be used in screening in subsequent environmental monitoring efforts. Additionally, the findings will establish the extent to which the observed environmental disruption of thyroid function may be translated into impaired physiological performance indices in the fish.

Preliminary research by the PIs uncovered significant thyroid system disruption in wild fish in association with contaminated locations in northern and Southern California. This study will directly study this important water quality problem and is aimed at providing critical information relevant to management of marine resources, including characterizing the nature of the effect in the fish, identification of related environmental contaminants, and providing key data on the larger ecologically relevant impacts on physiological performance. This project brings together an academic research laboratory with expertise in fish endocrinology and toxicology, an important regional agency (Orange County Sanitation District), and a minority-owned non-for-profit environmental organization, the Pacific Coast Environmental Conservancy (PCEC). These partners are providing important non-federal match for this project‘s successful outcome.

The objectives of the proposed work are directly relevant to State and regional environmental managers, as they work toward effective ecological-based management, which has traditionally developed water quality objectives based on concentrations of contaminants alone. There is a critical need for scientifically based understanding of impacts of water quality on wildlife in the urban ocean habitats of coastal California, and the proposed project directly addresses this need.

2015 Research Update:

This collaborative project—between a university, a regional sanitation district, and a local non-profit— has correlated specific anthropogenic contaminants with specific impacts to endocrine tissue and function along coastal California, particularly in areas of impaired water quality with low tidal flow.

This project has demonstrated significant correlation of certain classes of persistent organic contaminants (PCBs and PAHs) in the disruption of thyroid hormone levels in fish (albeit through different mechanisms), and PAHs are linked to disruption of the adrenal endocrine system in some fish. Histological analyses in shiner perch indicates that thyroid-disrupted fish exhibit abnormal thyroid glandular and cellular anatomy. Data also show that thyroid hormone levels in shiner perch and staghorn sculpin appear to be reduced in fish from the most impaired internal locations (harbors), while they improve with sampling closer to the tidal zone. In addition to many publications and presentations, this project has collaborated with the local Cabrillo Marine Aquarium in San Pedro, California, to create a permanent public exhibit teaching visitors about pollution in the seas and its effects on fish.