FATTY ACIDS AND STABLE ISOTOPES IN ANTARCTIC SPONGES

66 Pages·2005·1.23 MB·English

FATTY ACIDS AND STABLE ISOTOPES IN ANTARCTIC

SPONGES: DIET ANALYSIS OF GUTLESS ANIMALS.

A Thesis Presented to the Faculty
of
California State University, Stanislaus
through
Moss Landing Marine Laboratories

In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Marine Science

By
© Andrew Reichmann Thurber
May 2005
CERTIFICATION OF APPROVAL

FATTY ACIDS AND STABLE ISOTOPES IN ANTARCTIC

SPONGES: DIET ANALYSIS OF GUTLESS ANIMALS.

By
Andrew Thurber

__________________________________________ ______________________
Dr. Nicholas Welschmeyer Date
Professor of Biological Oceanography

__________________________________________ ______________________
Dr. Stacy Kim Date
Adjunct Professor of Benthic Ecology

__________________________________________ ______________________
Dr. Pamela Roe Date
Professor of Invertebrate Biology

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Unpublished Work copyright 2005 Andrew Reichmann Thurber
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ACKNOWLEDGMENTS
This work would not have been possible without the support of my family, my
committee, and the students, staff, and faculty of Moss Landing Marine Laboratories.
Rebecca Vega and the rest of my family were a constant source of support and joy
throughout my time here. Invaluable comments on drafts of my proposal and thesis were
made by Rob Leaf, Rhea Sanders, and Aroon Melwani. Dive buddies including Aaron
Carlisle, Dr. John Oliver, Dr. Kathy Conlan, Mike Donnellan, Jennifer Fisher, Dan
Malone, Dr. Stacy Kim, Rob Robbins, and Bob Zook helped regardless of how tired they
may have been. Aaron Carlisle was always willing to get dragged into the field at any
hour of day or night and for that I am grateful. Wade Smith, Dr. John Oliver, and Dr.
Rob Burton offered valuable advice throughout my time here at MLML and much of this
research was inspired by a class taught by and interactions with Dr. Burton. Dr. Stacy
Kim provided enthusiasm, opportunity, never ending support, and many a good time to
this research, not to mention advice along the way. Dr. Pamela Roe was amazing at
easing the life of a Moss Landing graduate student by always fixing any paperwork
problem I may have encountered or caused, not to mention being an invaluable member
of my committee. Dr. Nicholas Welschmeyer fostered the oceanographic side of my
research interests and helped me think in a more pelagic way. The MLML Benthic
Ecology lab provided a home and an endless amount of entertainment and support.
Kamille Hammerstrom provided the GIS maps and was there at the end to bounce ideas
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off of. My initial interest in benthic ecology and the Antarctic were the result of
interactions with Dr. Eric Vetter and Dr. Craig Smith. This research was supported by
funds from the Earl and Ethyl Meyers Oceanographic Research Trust, the PADI
Foundation, the Dr. John H. Martin Memorial Scholarship, and the National Science
Foundation, Office of Polar Programs grant 0126319.

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TABLE OF CONTENTS

Publication Rights.......................................................................................... iii
Acknowledgements........................................................................................ iv
List of Tables ................................................................................................ vii
List of Figures................................................................................................ viii
Abstract.......................................................................................................... x
Introduction.................................................................................................... 1
Materials and Methods................................................................................... 8
Results............................................................................................................ 14
Discussion...................................................................................................... 18
Conclusions.................................................................................................... 31
Literature cited .............................................................................................. 32
Tables............................................................................................................. 41
Figures............................................................................................................ 46
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LIST OF TABLES
TABLES PAGE

Table 1: The distribution of fatty acids, viable fecal coliform bacteria, and total
bacteria as enumerated by epifluorescence microscopy at the given distances from
the McMurdo Station outfall, Antarctica, listed from North to South. (---)
indicates bellow detectable limit................................................................................ 42

Table 2: Statistical comparison between a selection of fatty acid biomarker
concentrations in four species of sponge. Nested ANOVAs compare between
species and linear regressions indicate differences in concentration with
increasing distance from the McMurdo Station sewage outfall. Post hoc results
are indicated on Figures 2,3, and 5............................................................................ 43

Table 3: Statistical comparison between groups of fatty acid biomarker
concentrations in four species of sponge. Nested ANOVAs compare between
species and linear regressions indicate differences in concentration with
increasing distance from the McMurdo Station sewage outfall. Post hoc results are
indicated on Figures 4 and 5...................................................................................... 44

Table 4: Statistical comparison between the stable isotopic concentrations of four
species of sponge. Nested ANOVAs compare between species and linear
regressions indicate differences in concentration with increasing distance from the
McMurdo Station sewage outfall. ............................................................................ 45

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LIST OF FIGURE
FIGURES PAGE
Figure 1: Locations of sponge and water collections at McMurdo Station,
Antarctica. Current speed (cm s-1)and direction during the time of water
collection is shown in the vector diagram as recorded by an S4 current meter......... 47

Figure 2: Percent composition of the FA 18:2(n-6) (top) and 18:1(n-9) (bottom) in
four species of sponge at varying distances from the McMurdo Station outfall.
Locations are listed from north to south and error bars are standard error.
Location 166 for I. setifera had no replication and the lack of error bars reflects
this. Differences in species are indicated by different letters over the group and a
significant change with distance is indicated by an asterisk. Statistical results are
presented in Table 2................................................................................................... 48

Figure 3: Percent composition of the FA 22:6(n-3) (top) and 16:1(n-7) (bottom) in
four species of sponge at varying distances from the McMurdo Station outfall.
Locations are listed from north to south and error bars are standard error.
Location 166 for I. setifera had no replication and the lack of error bars reflects
this. Differences in species are indicated by different letters over the group and a
significant change with distance is indicated by an asterisk. Statistical results are
presented in Table 2................................................................................................... 49

Figure 4: Percent composition of the polyunsaturated fatty acids (top) and
bacterial fatty acids (15:0, 17:0, iso- and antiso-FA) (bottom) in four species of
sponge at varying distances from the McMurdo Station outfall. Locations are
listed from north to south and error bars are standard error. Location 166 for I.
setifera had no replication and the lack of error bars reflects this. Differences in
species are indicated by different letters over the group and a significant change
with distance is indicated by an asterisk. Statistical results are presented in Table
3.................................................................................................................................. 50

Figure 5: The ratio of bacterial fatty acids to polyunsaturated fatty acids (top) and
the abundance of 20:5(n-3) (bottom) in four species of sponge at varying
distances from the McMurdo Station outfall. Locations are listed from north to
south and error bars are standard error. Location 166 for I. setifera had no
replication and the lack of error bars reflects this. Differences in species are
indicated by different letters over the group and a significant change with distance
is indicated by an asterisk. Statistical results are presented in Tables 2 and 3......... 51

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FIGURES PAGE

Figure 6: Principal Component Analysis (PCA) plot of the fatty acid constituents
of four species of sponge at varying distances from the McMurdo Station sewage
outfall......................................................................................................................... 52

Figure 7a: Bi-plot of the eigenvectors that accounted for more than 10% of the
variability in principal components one and two....................................................... 53

Figure 7b: Bi-plot of the eigenvectors that accounted for more than 10% of the
variability in principal components two and three..................................................... 54

Figure 8: Stable isotopic concentration of four species of sponge at indicated
distances from the McMurdo Station sewage outfall, Antarctica. Error bars
indicate standard error. I. setifera data are expanded in the inset............................. 55

Figure 9: Percent decrease of total bacterial abundance over time in a closed
system containing the indicated species of sponge or a control of nothing. n=5 and
error bars are standard error....................................................................................... 56
.

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ABSTRACT
The Antarctic has a diverse and conspicuous sponge community, but the diets of
Antarctic sponges have not been quantified or described. This study used three
techniques, fatty acid analysis, stable isotope concentrations, and a laboratory based
feeding study, to address the diet of four species of Antarctic sponge: Homaxinella
balfourensis, Isodictya setifera, Kirkpatrickia variolosa, and Sphaerotylus antarcticus.
Sponges were sampled at distances between 115 and 840 m from the McMurdo station
sewage outfall to provide potential diet variability. The sewage effluent acted as a tracer
for particulates larger than bacteria. Sponge diet ranged from mostly bacteria, in the case
of I. setifera, to mostly flagellates, for H. balfourensis. The diet of K. variolosa was
intermediate between these two. The diet of S. antarcticus was not completely resolved
by this study; fatty acid analysis supported its similarity to K. variolosa yet the isotopic
analysis and feeding study separated it from the other sponges studied, suggesting that
symbionts were abundant enough in this species to confound the results. This study is the
first application of fatty acid analysis to determine diet composition of sponges, the first
stable isotopic analysis of Antarctic sponges identified to species, and the first indication
of differential utilization of microbial loop components by co-occurring sponges. The
role of sponges as a conduit for microbial resources to the benthic metazoan food web is
discussed.
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