Kelley van Hees

Contaminant transfer from mother to offspring: do coastal elasmobranch reproductive strategies make a difference?

Email: kandrews@mlml.calstate.eduKelley somniosus1

My interests involve the bioaccumulation of contaminants in shark tissues, particularly mercury, and the mechanisms of contaminant transfer from mother to embryo during development.  Before attending Moss Landing, I earned my B.S. in marine biology from Western Washington University in 2010.  After graduating, I volunteered as a research assistant for the Shark Bay Ecosystem Research Project in Shark Bay, Western Australia.


Graduated – Fall 2014

Thesis Project:

Studies have shown that elasmobranchs, due to their high trophic positions, slow metabolism, lipid-rich livers, and long lifespans, accumulate relatively high levels of mercury in their tissues (Hueter et al. 1995; Davis et al. 2002; Coelho et al. 2010).  Much research has been conducted in order to establish mercury concentrations in muscle tissue of various species and evaluate the risk to human health from consumption of shark meat.  Concentrations of mercury in the muscle tissue have been found to be extremely variable across species, and it is not well understood what causes these differences (Storelli and Marcotrigiano 2002).  Additionally, very little is known about the impacts of mercury toxicity to the animals themselves.

One important aspect of mercury accumulation in shark tissues that has seen little investigation thus far is the potential effect it could have through reproduction.  Shark embryos have shown measurable levels of mercury in their tissues, demonstrating that females transfer mercury to their offspring during development (Jeffree et al. 2008; Pethybridge et al. 2011, Paiva et al. 2012).  This transfer may have negative implications for human health and the health of the species.  If juveniles begin life with elevated levels of mercury in their tissues and accumulate more as they grow, they could become unsafe for human consumption at progressively smaller sizes.  In addition, individuals could accumulate dangerous levels in their body at younger ages, potentially affecting their ability to grow and reproduce, which could have broader implications on the population at large.  Furthermore, it is unlikely that every species transfers the same amount of mercury to their offspring through development.  Sharks and rays have a variety of reproductive strategies, and each is associated with differing energetic and nutrient investment from the mothers (Pethybridge et al. 2011).  It is possible that some reproductive modes involve a greater transfer of contaminants to the embryos, indicating that those species could be more vulnerable to mercury pollution.


The goals of my study are as follows:

1) Establish mercury concentrations in females and embryos of several species of elasmobranchs that occur in two central California coastal estuaries;

2) Sample throughout the gestation period to gain a better understanding of how mercury is transferred to offspring during development; and

3) Investigate whether some species have greater transfer rates of mercury to their offspring than others to determine which species are the most vulnerable to mercury accumulation.