Bio-optical characterization of bottom ice algae in snow-covered landfast sea ice in Baffin Bay ...

99 Pages·2017·10.25 MB·English

Bio-optical characterization of bottom ice algae in snow-covered landfast sea
ice in Baffin Bay, Nunavut
by
Christine Quiring

A Thesis submitted to the Faculty of Graduate Studies of
The University of Manitoba
In partial fulfilment of the requirements of the degree of

MASTER OF SCIENCE

Department of Environment and Geography
University of Manitoba
Winnipeg

Copyright © 2017 by Christine Quiring
ABSTRACT

During late-winter/spring, ice algae often form in a layer at the bottom of Arctic sea ice. This
thesis investigates how these ice algae imbedded within a sea ice matrix absorb solar radiation,
and how the spectral distribution of the radiation transmitted through the ice can be used to infer
ice algae properties. During a case study of landfast ice in Baffin Bay, NU, Canada, it was found
that (i) ice algae were highly shade-acclimated with absorption characteristics indicating a strong
package effect, a likely result of the deep snow-cover. Furthermore, transmittance spectra (ii)
revealed that ice algae attenuated significantly more radiation, (iii) showed evidence of natural
fluorescence, and (iv) potentially indicated the presence of an un-sampled algal or cyanobacterial
population, than that expected from extracted ice sample analyses in the laboratory. These results
emphasize the important role of spectral transmittance observations in informing bio-optical and
primary productivity studies of sea ice algae.

ii
ACKNOWLEDGMENTS

Foremost I wish to thank my advisors, Drs. C.J. Mundy and Jens Ehn, for their continuous
teachings, support, encouragement and patience, as well as my committee members Dr. Mark
Hanson and Dr. Andrea Niemi for their insight, knowledge and contributions. I also wish to
thank Nicole Pogorzelec for sampling in my place during the Green Edge 2015 Campaign and
the 2015 R/V Martin Bergmann Cruise.

Financial support for the Green Edge 2015 Campaign is attributed to the Canadian Space Agency
(CSA), with additional project support from ANR, CNES, IPEV, Foundation Total, ArcticNet,
LEFE and the French Arctic Initiative. This study would not have been possible without the
financial support of the Northern Scientific Training Program (NSTP), the Arctic Science
Partnership (ASP), the Natural Sciences and Engineering Research Council of Canada (NSERC)
and the University of Manitoba Graduate Fellowship (UMGF). I am very grateful for the support
of the Hamlet of Qikiqtarjuaq and the members of the community, as well as the Inuksuit School
and its Principal Jacqueline Arsenault.

I extend a special thank you to Kristina Brown and Aurelie Delaforge for teaching me the ropes
on my very first Arctic cruise expedition. I am also very thankful for the captain and crew of the
Martin Bergmann for their expertise in the field and their tireless efforts in ensuring all
researchers working onboard achieved their sampling objectives.

To my family, friends, fiancé, yoga family and fellow graduate students, I cannot express enough
gratitude for your constant foundation of encouragement and support.
iii
TABLE OF CONTENTS
Abstract..........................................................................................................................................ii
Acknowledgements.......................................................................................................................iii
List of Figures................................................................................................................................vi
List of Tables...............................................................................................................................viii
List of Abbreviations and Notations...........................................................................................ix
List of Copyrighted Material.......................................................................................................xi
Contribution of Authors.............................................................................................................xii
1.0 Introduction.............................................................................................................................1
1.1 Research Objectives...........................................................................................................2
1.2 Thesis Outline.....................................................................................................................3
References..........................................................................................................................4
2.0 Background.............................................................................................................................6
2.1 Concepts of hydrologic optics...........................................................................................6
2.1.1 The nature of light.......................................................................................................7
2.1.2 Basic concepts of the light field..................................................................................9
2.2 Incident solar radiation....................................................................................................13
2.3 Radiative transfer in ice-covered waters..........................................................................14
2.3.1 Apparent optical properties......................................................................................14
2.3.2 Inherent optical properties.......................................................................................17
2.3.3 Radiative transfer theory..........................................................................................19
2.3.4 Light interactions with seawater, sea ice and snow.................................................20
2.3.4.1 Seawater as an optical medium...........................................................................21
2.3.4.2 Sea ice as an optical medium...............................................................................21
2.3.4.3 Snow cover as an optical medium........................................................................23
2.4 Light absorption by ice algae...........................................................................................25
2.4.1 Ice algae habitat........................................................................................................26
2.4.2 Absorption and scattering within the vertical ice matrix...........................................27
2.4.3 Ice algal attenuation properties and the package effect............................................28
2.5 Conclusions......................................................................................................................31
References........................................................................................................................33
3.0 Bio-optical characterization of snow-covered sea ice with a near-bottom ice algae layer
in Baffin Bay, near Qikiqtarjuaq, Nunavut.......................................................................39
Abstract................................................................................................................................39
3.1 Introduction...................................................................................................................40
3.2 Methods.........................................................................................................................42
3.2.1 Study location and sampling ....................................................................................42
3.2.2 Irradiance measurements..........................................................................................44
3.2.3 Particulate analyses..................................................................................................45
3.2.4 Statistical analysis ...................................................................................................47
3.3 Results...........................................................................................................................48
3.3.1 General field observations........................................................................................48
3.3.2 Particulate absorption characterization...................................................................51
3.3.3 Functional linear regression attenuation coefficients..............................................53

iv
3.4 Discussion ....................................................................................................................56
3.4.1 Bottom ice algal particulate absorption...................................................................56
3.4.2 In situ algal attenuation versus ex situ ice algal absorption....................................59
3.4.2.1 Matching FLR with particulate absorption measurements.................................60
3.4.2.2 Differences in spectral shapes.............................................................................64
Acknowledgements...............................................................................................................66
References............................................................................................................................68
4.0 Summary and conclusions....................................................................................................73
4.1 Summary of findings.....................................................................................................73
4.2 Future recommendations...............................................................................................75
References............................................................................................................................78
5.0 Appendices.............................................................................................................................80
5.1 Appendix A. Equations.................................................................................................80
5.2 Appendix B. Particulate absorption: filter preparation and analysis with an integrating
sphere.............................................................................................................................82
5.3 Appendix C. Field work images....................................................................................87

v
LIST OF FIGURES

Figure 2.1. The relationship between hydrologic optics and other branches of optics (adapted
from Preisendorfer, 1976 and Kirk, 1994)......................................................................................7
Figure 2.2. Angles defining direction within a light field, with the assumption that the xy plane is
the vertical plane of the Sun where θ is the zenith angle and 𝜙 is the azimuth angle (adapted from
Kirk, 2011......................................................................................................................................10
Figure 2.3. Two types of irradiances: (a) downwelling irradiance and (b) downwelling scalar
irradiance, from the upper hemisphere with units (W m-2 nm-1). Note: although not depicted
above, planar and scalar irradiance can be broken down into both downwelling and upwelling
components (adapted from Apel, 1987).........................................................................................12
Figure 2.4. Example absorption coefficients for phytoplankton absorption, a (green line),
ph
detrital matter, a (red line) (obtained from averaged data from this thesis), water, a (blue line)
d w
on the right y-axis (Smith and Baker 1981), and colored dissolved organic matter, a (purple
cdom
line) (Miller and Buonsassissi, 2010)............................................................................................18
Figure 2.5. Single beam of radiance and the processes that effect it as it propagates through a
distance, r in the direction θ, 𝜙, loses some photons via scattering out of the path and absorbing
by the medium along the path. Some photons are acquired by scattering of light initially traveling
in other directions, θ′, 𝜙′, into the direction of θ, 𝜙. Note: Radiative transfer models integrate all
of the different beams of light from all directions of a given point, not just a single beam from
one direction (adapted from Mobley, 2010)..................................................................................20
Figure 2.6. Vertical schematic of algal assemblages found in Arctic sea ice (Horner et al.,
1988)..............................................................................................................................................27
Figure 2.7. The effect of growth irradiance on the optical absorption cross section normalized to
chlorophyll a (top). Cells grown at high light levels have less cellular chlorophyll and thylakoid
membranes within the chloroplast (bottom right) than cells grown in low light (bottom left). The
optical consequences of these changes in chloroplast ultrastructure are increased optical
absorption cross section for cells with lower chlorophyll content (Falkowski and Raven,
2007)..............................................................................................................................................31
Figure 3.1. Map of the Green Edge Ice Camp site located near Qikiqtarjuaq, Broughton Island,
Nunavut [67°28.784N, 063°47.372W]. Bathymetric data compiled from the International
Bathymetric Chart of the Arctic Ocean (IBCAO, V3). The measurement region is marked with a
red circle.........................................................................................................................................43

Figure 3.2. Measurements at thick and thin snow cover sites for ice thickness, Z, (a), snow
I
depth, Z , (b), total chlorophyll a, [T ], (c), and under-ice downwelling irradiance over the
S chl-a
spectral range of photosynthetically active radiation (400-700 nm), E (PAR), (d)...................49
d-ui

Figure 3.3. Spectral distribution of transmitted downwelling radiation over PAR, E , beneath
d-T
landfast ice for four snow cover and [T ] conditions: 12 June- thin snow cover and low [T ],
chl-a chl-a
vi
12 May- thin snow cover and high [T ], 16 May- thick snow cover and low [T ], and 6
chl-a chl-a
June- thick snow cover and high [T ]........................................................................................51
chl-a

Figure 3.4. Total, a , (a), algal, a , (b) and de-pigmented, a , (c) particulate absorption
p ph d
coefficients at 440 nm versus total chlorophyll-a concentration, [T ]. The percent ratio of a :a
chl-a d p
at 440 nm is also plotted in (c). Power models from Bricaud et al. (2004) are plotted for
comparison with a global phytoplankton dataset...........................................................................52

Figure 3.5. Estimated coefficient functions (thick black lines) for: attenuation coefficient of
snow, K (λ), (a), attenuation coefficient of ice, K (λ), (b), total chlorophyll a specific diffuse
d,S d,I
attenuation coefficient, K *(λ), (c), and intercept, β (λ), (d), with associated 95% confidence
d 0
intervals (thin grey lines) from the functional linear regression model (Eq. 3.3)..........................54

Figure 3.6. The functional linear regression coefficient, R2, for our model, as a function of
wavelength (nm)............................................................................................................................56

Figure 3.7. Bottom view of a sea ice core (photo credit: Jens Ehn)..............................................62

Figure 3.8. Comparison of: (a) average spectral chlorophyll-specific absorption coefficient,
𝑎 (λ) (grey dotted line), concentrated and scatter inclusive average spectral chlorophyll-specific
!
absorption coefficient, K (λ) = {(𝑎 (λ) x 4.7) + 7.5} (grey solid line), and modeled average
d,w !
algal biomass attenuation coefficient, K (λ) (solid black line) (from this study), and
d,FLR
comparison of (b) spectral difference between K (λ) and K (λ) (solid blank line), and
d,FLR d,w
relative absorption of fucoxanthin (brown solid line) (from Bricaud et al 2004), R-PE (blue solid
line), C-PE (blue dashed line), R-PC (green dashed line), and Allophycocyanin (red solid line)
(from Zhao et al., 2011).................................................................................................................63

vii
LIST OF TABLES

Table 2.1. The electromagnetic radiation spectrum divided into wavelength subregions. The
spectrum shows decreasing frequency, increasing wavelength, and lower energy, as you go from
top to bottom. Due to the absorbing properties of water, oceanographic optics is limited to the
electromagnetic spectrum region of 300–1000 nm (adapted from Lillesand and Kiefer, 1994).....9
viii
LIST OF ABBREVIATIONS, NOTATIONS AND UNITS

(List only includes those used regularly in this thesis)

Notation Description Values/ Units
Waveband

CDOM Coloured dissolved organic matter

PAR Photosynthetically active radiation 400-700 nm µmol m-2 s-1

λ Wavelength nm
c Speed of light 3.00 x 108 m s-1
v Frequency Hz

h Planck’s constant 6.63 x 10-34 J s
k Boltzmann’s constant 1.38 x 10-23 J K-1
𝑁 Avogadro’s number 6.022 x1023 Photons (1 mole)
!

R Reflectance dimensionless
n Refraction dimensionless
z Depth m

AOP Apparent optical property

α (λ) Surface spectral albedo dimensionless

E(λ) Spectral irradiance W m-2 nm-1

E (λ) Downwelling spectral irradiance W m-2 nm-1
d
E (λ) Upwelling spectral irradiance W m-2 nm-1
u
𝐸(λ) Net downward spectral irradiance W m-2 nm-1

E (λ) Scalar spectral irradiance W m-2 nm-1
0
E (λ) Downwelling scalar spectral irradiance W m-2 nm-1
0d

E (λ) Surface incident spectral irradiance W m-2 nm-1
d-sfc
E (λ) Under-ice downwelling spectral irradiance W m-2 nm-1
d-ui
Ed-ui (PAR) Under-ice downwelling PAR irradiance µmol m-2 s-1
E (λ) Spectral transmittance dimensionless
d-T

K(λ) Diffuse vertical attenuation coefficient m-1

𝜇 (λ) Downwelling average cosine dimensionless
!

IOP Inherent optical property
ix
a Absorption coefficient m-1
b Scattering coefficient m-1

a *(λ) Chlorophyll-specific absorption m2 mg-1
p
coefficient
a *(PAR) Chlorophyll-specific algal absorption over m2 mg-1
ph
PAR
𝑎 (λ) Study averaged a *(λ) multiplied by the m-1
! p
average [T ]
chl-a
Q * Package effect coefficient dimensionless
a

𝜃 Zenith angle sr
𝜙 Azimuth angle sr

Φ Radiant flux W or J s-1
L(𝜃, 𝜙, 𝜆) Radiance W m-2 s-1 nm-1
A Unit area m-2
w Solid angle sr

FLR Functional linear regression

Z Snow depth m
S
Z Ice thickness m
I
[T ] Total chlorophyll a concentration mg m-3 or
chl-a
mg m-2

τ (λ) Spectral optical thickness dimensionless
K (λ) FLR model snow downwelling attenuation m-1
d,S
coefficient
K (λ) FLR model ice downwelling attenuation m-1
d,I
coefficient
K * (λ) FLR model chlorophyll-specific bottom- m2 mg-1
d
ice algae downwelling attenuation
coefficient
β (λ) FLR model intercept dimensionless
0
ε (λ) Functional standard error dimensionless
R2 Coefficient of variation dimensionless

a Particulate absorption coefficient m-1
p
a De-pigmented absorption coefficient m-1
d
a Algae absorption coefficient m-1
ph

β Pathlength amplification factor dimensionless

a a Percent ratio of de-pigmented to total dimensionless
d: p
particulate absorption
x