Inductively Coupled Plasma Optical Emission Spectroscopy Analysis of Heavy Metal Concentrations in Gulf Menhaden (Brevoortia patronus) Populations in the Northern Gulf of Mexico from 2011 to 2012

• Main Author: Rockett, Hannah Paula
• Other Authors: Wilson, Vincent Lee
• Format: Others
• Language: en
• Published: LSU 2013
• Subjects: Environmental Sciences
• Online Access: http://etd.lsu.edu/docs/available/etd-07012013-113825/

In 2010, the Deepwater Horizon (DWH) oil spill, released 4.9 million barrels of oil into the Gulf of Mexico, creating the largest marine oil spill in the history of the U.S. petroleum industry. Trace metals, including those from crude oil, were dispersed in the water column and bound to suspended particulates. As obligate filter-feeding omnivores and a predominate fishery in the Gulf of Mexico, Gulf menhaden (Brevoortia patronus) are susceptible to trace metal accumulation. Samples of menhaden were collected at two locations in coastal Louisiana, Grand Isle (GI) and Vermillion Bay (VB), with VB serving as the non-impacted DWH oil spill site and GI as the impacted DWH oil spill site. The analysis of trace metals was performed using inductively coupled plasma-optic emission spectroscopy (ICP-OES) methods. Eleven metals (As, Ba, Cd, Co, Cr, Cu, Fe, Ni, Pb, Zn, V) were chosen and observed by four variables: place (VB or GI), size (small or large), month (July, August or September), and year (2011 or 2012) and the interactions between the variables. Metal concentrations in the current study followed the sequence: Fe > Zn > Ba > As > V > Cr > Cu > Ni > Pb > Co > Cd. Results showed that in 2011, VB had statistically higher concentrations than GI for 9 of the 11 metals. Elevated discharge rates during the Mississippi River Flood of 2011 produced a dilution effect, decreasing the concentration of trace metals in the water column at GI. Size was also significant, with small fish having statistically higher concentrations for 8 of the 11 metals. In fish, younger/smaller fish have higher metabolic activities than older/larger fish, which leads to a higher metal accumulation in smaller fish. Arsenic was the only metal that had higher concentrations in 2011 and in large fish. Differences in arsenic trends may be attributed to the DWH oil spill, which may have caused reduced adsorption of arsenic by the mineral goethite and increased concentrations of arsenic in the water. Iron and zinc in the current study exceeded the FAO/WHO maximum permissible limit.