Karenia brevis harmful algal blooms

76 Pages·2015·1.45 MB·English

UUnniivveerrssiittyy ooff SSoouutthh FFlloorriiddaa
DDiiggiittaall CCoommmmoonnss @@ UUnniivveerrssiittyy ooff
SSoouutthh FFlloorriiddaa
USF Tampa Graduate Theses and Dissertations USF Graduate Theses and Dissertations
3-26-2014
KKaarreenniiaa bbrreevviiss hhaarrmmffuull aallggaall bblloooommss:: TThheeiirr rroollee iinn ssttrruuccttuurriinngg tthhee
oorrggaanniissmmaall ccoommmmuunniittyy oonn tthhee WWeesstt FFlloorriiddaa SShheellff
Alisha Marie Gray
University of South Florida, [email protected]
Follow this and additional works at: https://digitalcommons.usf.edu/etd
Part of the Aquaculture and Fisheries Commons, and the Ecology and Evolutionary Biology Commons
SScchhoollaarr CCoommmmoonnss CCiittaattiioonn
Gray, Alisha Marie, "Karenia brevis harmful algal blooms: Their role in structuring the organismal
community on the West Florida Shelf" (2014). USF Tampa Graduate Theses and Dissertations.
https://digitalcommons.usf.edu/etd/5029
This Thesis is brought to you for free and open access by the USF Graduate Theses and Dissertations at Digital
Commons @ University of South Florida. It has been accepted for inclusion in USF Tampa Graduate Theses and
Dissertations by an authorized administrator of Digital Commons @ University of South Florida. For more
information, please contact [email protected].
Karenia brevis Harmful Algal Blooms: Their Role in Structuring the Organismal

Community on the West Florida Shelf

by

Alisha Marie Gray

A thesis submitted in partial fulfillment
of the requirements for the degree of
Master of Science
with a concentration in Marine Resource Assessment
Department of Marine Science
College of Marine Science
University of South Florida

Major Professor: Cameron H. Ainsworth, Ph.D.
John J. Walsh, Ph.D.
David D. Chagaris, Ph.D.

Date of Approval:
March 26, 2014

Keywords: Ecopath with Ecosim, fish kills, Gag grouper, brevetoxin, red tides

Copyright © 2014, Alisha Marie Gray
ACKNOWLEDGMENTS

To begin, I would like to express my utmost gratitude to my committee members,
Dave Chagaris and John Walsh for their time, patience, and expertise, and especially to
my advisor and mentor, Cameron Ainsworth. I have learned and accomplished so much
with their guidance and help. Florida Fish and Wildlife Research Institute was immensely
helpful, specifically Behzad Mahmoudi, Karen Steidinger, Theresa Cody, and Kerry
Flaherty. They provided datasets, invaluable knowledge of Karenia brevis harmful algae
blooms, and foundational models of the West Florida Shelf which all allowed me to
complete this project. National Oceanic and Atmospheric Administration also contributed
to the model not only by providing the Karenia brevis severity index, but by also putting
the model to use in the SEDAR-33 document. Funding for this research was made
available by the Von Rosenstiel fellowship, the Southern Kingfish fellowship, and the
Sanibel Captiva/Anne and Al Bridell Memorial fellowship, all available through the
University of South Florida’s College of Marine Science. Further funding for data
collection was provided by C-IMAGE. Finally, I would like to thank my friends and
family who have motivated and supported my endeavors to advance myself in the marine
sciences. Without the support of all of these people, among many of whom I could not
mention, I would not be where I am today, and I will always have them to thank.
TABLE OF CONTENTS

List of Tables ..................................................................................................................... iii
List of Figures .................................................................................................................... iv
List of Acronyms .................................................................................................................v
List of Symbols .................................................................................................................. vi
Abstract ............................................................................................................................. vii
Chapter One: Introduction ...................................................................................................1
1.1 Karenia brevis ....................................................................................................1
1.2 Karenia brevis in the food web ..........................................................................3
1.3 Impacts on humans ............................................................................................4
1.4 Objectives ..........................................................................................................5

Chapter Two: Methods ........................................................................................................9
2.1 Ecopath with Ecosim description .......................................................................9
2.2 Ecopath model construction .............................................................................11
2.3 Incorporating HABS into the model ................................................................15
2.4 Historical model ...............................................................................................17
2.5 Tuning the historical model .............................................................................20
2.6 Application of the model .................................................................................21

Chapter Three: Results .......................................................................................................25
3.1 West Florida Shelf ecosystem ..........................................................................25
3.2 Gag case study .................................................................................................32

Chapter Four: Discussion ...................................................................................................35
4.1 Karenia brevis on the West Florida Shelf ........................................................35
4.2 Gag case study .................................................................................................40
4.3 Improvements and future research ...................................................................41

Chapter Five: Conclusions .................................................................................................44

Literature Cited ..................................................................................................................46

Appendices .........................................................................................................................55
i
Appendix A: Model data tables .............................................................................55
Appendix B: Pre-balance tests ...............................................................................62
Appendix C: Fit to times series graphs ..................................................................64

ii
LIST OF TABLES

Table 1. List of single species groups added to West Florida Shelf model (Okey
and Mahmoudi 2002) for this study ....................................................................13

Table 2. Discard values in tonnes/km2 applied to the historical HAB fleet to
represent mortality associated with Karenia brevis blooms ...............................19

Table 3. Δ SS with Karenia brevis bloom mortality in functional groups directly
affected by the bloom mortality ..........................................................................26

Table 4. Results of all statistical analyses performed to compare the effects of
Karenia brevis bloom mortality to no bloom mortality on the model ................28

Table 5. Natural mortality as a result of harmful algal blooms (M ) on Gag
HAB
grouper ................................................................................................................28

Table A.1. List of species that make up each aggregated functional group (Okey
and Mahmoudi 2002) ......................................................................................55

Table A.2. Origins of data to build the time series used for the model ............................57

Table A.3. All basic parameter inputs used in the final historical model .........................60

iii
LIST OF FIGURES

Figure 1. Comparison of Gag grouper biomass in the presence and absence of
Karenia brevis blooms ......................................................................................29

Figure 2. Percent change in biomass across the food web in the presence and
absence of Karenia brevis bloomsmortality .....................................................29

Figure 3. Comparison of Gag grouper productivity in the presence and absence of
of Karenia brevis blooms..................................................................................30

Figure 4. Comparison of Shannon biodiversity indices for pelagic functional
groups in the presence and absence of Karenia brevis blooms ........................30

Figure 5. Comparison of Shannon biodiversity indices for benthic functional
groups in the presence and absence of Karenia brevis blooms ........................31

Figure 6. Karenia brevis bloom mortality with and without the presence of fisheries ..............31

Figure 7. Karenia brevis bloom mortality on adult Gag grouper ........................................32

Figure 8. Adult Gag mortality ...........................................................................................34

Figure 9. Comparison of Gag consumption in the presence and absence of
Karenia brevis blooms ................................................................................................ 34

Figure B.1. Total biomasses organized by trophic level for year 1980 ............................62

Figure B.2. Functional group productivity (production over biomass) organized
by trophic level ..............................................................................................62

Figure B.3. Functional groups organized by trophic level, high to low ...........................63

Figure C.1. Model biomass simulations against time series .............................................64

Figure C.2. Model landings simulations against time series ............................................64

iv
LIST OF ACRONYMS

EwE Ecopath with Ecosim
FWRI Fish and Wildlife Research Institute
GAM generalized additive model
HABs harmful algal blooms
NPZ nutrient-phytoplankton-zooplankton
NOAA National Oceanic and Atmospheric Association
SS sum of squares
VB Von Bertalanffy

v
LIST OF VARIABLES

a and b Length-weight parameters
F fishing mortality
K Von Bertalanffy growth parameter
L and L length at time and Von Bertelanffy length
t inf
at infinity
M natural mortality
P/B production over biomass
Q/B consumption over biomass
W /W weight of maturity over weight at infinity
mat inf
Z total mortality

vi
ABSTRACT

Karenia brevis dinoflagellate blooms off the west coast of Florida can create
devastating effects on marine communities when they release a neurotoxin known as a
brevetoxin. These blooms, informally referred to as red tides, can cause massive fish
kills, necessitate closures of shellfish fisheries, and can even leave lingering toxins that
impact shelf communities long after the bloom has dissipated. As a result, much effort
has been put into studying K. brevis bloom initiation and dynamics. However, how K.
brevis blooms impact Florida’s fisheries is not fully understood because the relationship
between K. brevis cell counts and fish mortality is poorly described. To study this
relationship and the ecosystem response to K. brevis blooms, Ecopath with Ecosim
(EwE) modeling is used to force K. brevis bloom mortality on the shelf ecosystems by
using a recently developed time series that indexes K. brevis bloom severity. This index
dynamically drives K. brevis bloom mortality in EwE in a historical reconstruction
scenario from 1980 to 2009. Three hypotheses on ecosystem response are explored using
Gag grouper as a case study. We postulate a) that K. brevis blooms impose bottom-up
and top-down effects on the food web, b) that episodic perturbations by these blooms
shape the community structure and c) that fishing pressure exacerbates those effects.
Results support the hypothesis that K. brevis blooms pose top-down food web pressures,
which is seen by evidence of trophic cascading. Changes in community structure with
bloom mortality are also evidenced by changes seen in biodiversity and richness. An
vii