TRACE METAL UPTAKE AND ACCUMULATION PATHWAYS IN KEMP'S RIDLEY SEA TURTLES

275 Pages·2005·1.28 MB·English

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TRACE METAL UPTAKE AND ACCUMULATION PATHWAYS

IN KEMP’S RIDLEY SEA TURTLES (LEPIDOCHELYS KEMPII)

A Dissertation

by

HUI-CHEN WANG

Submitted to the Office of Graduate Studies of
Texas A&M University
in partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

May 2005

Major Subject: Wildlife and Fisheries Sciences
TRACE METAL UPTAKE AND ACCUMULATION PATHWAYS
IN KEMP’S RIDLEY SEA TURTLES (LEPIDOCHELYS KEMPII)

A Dissertation
by
HUI-CHEN WANG

Submitted to Texas A&M University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Approved as to style and content by:

__________________________ _________________________
Andre Landry Gary Gill
(Chair of Committee) (Member)

__________________________ _________________________
Lee Fitzgerald William Neill
(Member) (Member)

__________________________ _________________________
Duncan MacKenzie Robert Brown
(Member) (Head of Department)

May 2005

Major Subject: Wildlife and Fisheries Sciences
iii
ABSTRACT

Trace Metal Uptake and Accumulation Pathways in Kemp’s Ridley
Sea Turtles (Lepidochelys kempii). (May 2005)
Hui-Chen Wang, B.S., Taipei Medical University;
M.S., National Taiwan Ocean University
Chair of Advisory Committee: Dr. André M. Landry, Jr.

Little is known of trace metal concentrations and their possible role in the
mortality of critically endangered Kemp’s ridley sea turtles (Lepidochelys kempii).
Research described herein characterized concentrations of seven trace metals –
Ag, Cd, Cr, Cu, Hg, Pb and Zn – in the blood and carapace tissue of captive
Kemp’s ridleys for use in assessing levels of these metals in wild counterparts.
Concentrations of same trace metals were characterized in post-pelagic through
adult life stages of 127 wild Kemp’s ridleys captured from the Gulf of Mexico and
southeast Atlantic during 2000 to 2002. Blood, carapace, liver, kidney, and
muscle tissues from live and/or stranded Kemp’s ridleys were analyzed for the
aforementioned trace metals via graphite furnace atomic absorption
spectrophotometer and cold vapor atomic fluorescence techniques conducted
under class-100 clean laboratory conditions. Similar trace metal assessments
were conducted on blue crab (Callinectes sapidus) prey to determine the role of
food as a possible uptake pathway in Kemp’s ridleys.
iv
Overall, trace metal levels in live, captive as well as wild ridleys were higher
in carapace tissue than in blood. Carapace concentrations of Ag, Cr and Hg in
Kemp’s ridleys across all post-pelagic life stages increased with increasing
straight carapace length (SCL). Carapace tissue of wild ridleys exhibited higher
Cr, Hg, and Pb levels than their blue crab prey, regardless of study area;
whereas, crabs yielded higher Ag and Cu concentrations. Dead stranded ridleys
yielded higher Ag, Cr, Hg, Pb, Zn levels in carapace tissue, whereas, their liver
exhibited higher Cd and Cu levels. This finding suggests carapace tissue could
serve as a suitable surrogate sample source for internal organs/tissues when
monitoring exposure of live Kemp’s ridleys to certain metals. The fact that larger,
stranded ridleys exhibited higher Ag, Cd, Hg, Pb and Zn levels than did their
smaller, live analogs from Texas and Louisiana implies that these older ridleys
had increased opportunities to accumulate higher metal concentrations in their
carapace tissue than did their younger conspecifics. This trend suggests that
carapace tissue has the potential to accumulate trace metals while blood-borne
concentrations reflect only recent exposure to trace metals.
v
DEDICATION

The dissertation is dedicated to my father for his advice and my loving
husband George for his continuous support and understanding.
vi
ACKNOWLEDGMENTS

I would like to thank my committee members, Drs. André Landry, Jr., Gary
Gill, Lee Fitzgerald, William Neill and Duncan MacKenzie for their advice and
assistance throughout the course of my graduate study. Special thanks go to my
principal advisor, Dr. André Landry, Jr., who accepted me as graduate student,
gave me the opportunity to study Kemp’s ridley sea turtles, believed in me and
guided me in accomplishing this research.
I am grateful for the financial support provided by the Texas Sea Grant
College Program, the National Marine Fisheries Service and the Texas Parks
and Wildlife Department. I would like to acknowledge the Marine Biology
Department at Texas A&M University at Galveston for providing graduate
teaching and research assistantships enabling the completion of this degree.
Travel funds were provided by the Sea Turtle Symposium, Texas A&M Graduate
Program Enhancement Fund, Erma Lee and Luke Mooney Travel Grant, and
Galveston Graduate Student Association.
This research would not have been possible without the collaboration and
assistance of individuals in the Laboratory for Oceanographic Environmental
Research (LOER) and Sea Turtle and Fisheries Ecology Research Laboratory
(STFERL). Dr. Gary Gill and research associate, Ronald Lehman, provided
access to as well as guidance and instructions on the operations of various
instrumentation used to conduct my research. Special thanks go to STFERL sea
vii
turtle crew: David Costa, Leonard and Lisa Kenyon, Tasha Metz, Stacie Arms
and others who provided assistance.
I would like to thank Tim Fontaine, Benjamin Higgins and Cain Bustinza
from the National Marine Fisheries Services, Galveston Laboratory, who
provided access to captive Kemp’s ridleys. Many thanks to Dr. Donna
Shaver-Miller and biologist, Cynthia Rubio, at the Padre Island Research Center
for collecting stranded sea turtle samples. Dr. Pat Fair, NOAA/NOS, provided the
opportunity and financial support to collect samples from nesting Kemp’s ridleys
on the Rancho Nuevo, Mexico beach. Tammie Halcumb and Janet Maxwell as
well as David Wentling, Tammy Holliday and Donald Harper provided assistance
and support throughout the difficult time of dealing with my international student
status.
Special thanks to my parents, sisters and brother, and new family by
marriage, for their moral support and encouragement throughout my education
overseas. Finally, I am grateful to my loving husband George Stavros, for his
endurance and love during preparation of this manuscript.
viii
TABLE OF CONTENTS
Page
ABSTRACT……………………………………………………………………….. iii
DEDICATION……………………………………………………………………... v
ACKNOWLEDGMENTS…………………………………………………………. vi
TABLE OF CONTENTS…………………………………………………………. viii
LIST OF TABLES………………………………………………………………… xiii
LIST OF FIGURES………………………………………………………………. xv
CHAPTER
I INTRODUCTION………………………………………….................. 1
Life History of Kemp’s Ridley…………………………………… 3
Role of Contaminants in Kemp’s Ridley’s Mortality…………… 3
Obstacles to Studying Trace Metals in Sea Turtles………….. 6
Trace Metal Studies Involving Sea Turtles……………………. 8
Trace Metals and Biological Activities…………………………. 10
Chromium (Cr)……………………………………………… 11
Copper (Cu)………………………………………………… 11
Zinc (Zn)…………………………………………………….. 12
Silver (Ag)…………………………………………………… 12
Cadmium (Cd)……………………………………………… 12
Mercury (Hg)……………………………………………….. 13
Lead (Pb)…………………………………………………… 14
Research Objectives and Hypotheses…………………........... 14

II RESEARCH APPROACH……………………………………………. 16
ix
TABLE OF CONTENTS (cont.)

CHAPTER Page
III TRACE METAL CONCENTRATIONS IN CAPTIVE-REARED
KEMP’S RIDLEY SEA TURTLES……………………………………. 19

Materials and Methods ………………………………………..... 21
Captive-Rearing Protocol………………………………….. 21
Sample Collection………………………………………….. 22
Sample Digestion…………………………………………… 23
Metal Analysis………………………………………………. 24
Quality Controls…………………………………………….. 25
Statistical Analysis…………………………………………. 28
Results ……………………………………………………........... 28
Discussion………………………………………………………... 35
Silver………………………………………………………… 38
Cadmium……………………………………………………. 38
Chromium…………………………………………………… 39
Copper………………………………………………………. 40
Mercury……………………………………………………… 41
Lead…………………………………………………………. 42
Zinc………………………………………………………….. 42
Summary…………………………………………………………. 43

IV AN ASSESSMENT OF TRACE METAL CONCENTRATIONS
IN KEMP’S RIDLEY SEA TURTLES AND THEIR BLUE CRAB
PREY…………………………………………………………………… 45

Materials and Methods …………………………………………. 48
Sea Turtle Capture and Study Area………………………. 48
Sample Collection and Digestion…………………………. 51
Metal Analysis………………………………………………. 54
x
TABLE OF CONTENTS (cont.)

CHAPTER Page
Statistical Analysis………………………………………….. 54
Results…………………………………………………………..... 55
Texas Study Sites…………………………………………… 59
Louisiana Study Site……………………………………….. 66
Southeast Atlantic Study Site……………………………… 72
Wild vs. Captive Kemp’s Ridleys: Trace Metal
Concentrations……………………………………………… 77
Discussion……………………………………………………....... 78
Silver…………………………………………………………. 79
Cadmium……………………………………………………. 83
Chromium…………………………………………………… 86
Copper………………………………………………………. 88
Mercury……………………………………………………… 90
Lead…………………………………………………………. 92
Zinc………………………………………………………….. 94
Summary…………………………………………………………. 96

V TRACE METAL CONCENTRATIONS IN NESTING KEMP’S
RIDLEY SEA TURTLES AND THEIR BLUE CRAB PREY…………….. 99

Materials and Methods…………………………………………. 101
Study Site…………………………………………………… 101
Sample Collection and Digestion………………………… 101
Metal Analysis……………………………………………… 102
Statistical Analysis…………………………………............ 102
Results……………………………………………………………. 103
Nesting Ridley Females: Trace Metal Concentrations…. 104
Blue Crabs: Trace Metal Concentrations………………… 111
Discussion………………………………………………………... 113