Kanaskie 1
Examining desert algal growth rates
and quantum yield in response to nutrient availability
Caroline Kanaskie
Environmental Studies Department
Dickinson College
Carlisle, PA 17013
Collaborator: Tinsley Galyean
Department of Environmental Studies and Sustainability
Hampshire College
Amherst, MA 10002
Advisors: Zoe Cardon and Elena Lopez Peredo
Ecosystems Center
Marine Biological Laboratory
Woods Hole, MA 02543
Semester in Environmental Science
21 December 2015
Kanaskie 2
Abstract
Desert algae are a crucial component of soil crusts in arid and semi-arid ecosystems
around the world. In the lab, I grew two species of desert algae, Scenedesmus deserticola and
Scenedesmus rotundus, in five different variations of Bold’s Basal Medium to test the effects of
micronutrient and vitamin availability on quantum yield and algal growth. I expected higher
growth and quantum yield in treatments with micronutrients, and that vitamins would assist with
growth. I found micronutrients to be important for both increasing growth and quantum yield in
S. deserticola. Treatment did not result in any significant differences in growth, quantum yield,
or non-photochemical quenching in S. rotundus. CHN analysis suggests that the presence of
vitamins and micronutrients in S. rotundus media allowed for increased nitrogen assimilation.
This information can assist in restoration of soil crusts by increasing algal growth and
photosynthetic efficiency in ex situ inoculant.
Kanaskie 3
Introduction
Desert microbiotic crusts are crucial components of arid and semi-arid ecosystems. In
arid ecosystems, microbiotic crusts can be the primary source of photosynthesis and nitrogen
fixation (Johnston, 1997; Cardon et al., 2008). Algae, bacteria, cyanobacteria, fungi, lichens, and
mosses create these crusts by binding soil particles and organic material, which enhances soil
stability and minimizes soil erosion. Crusts also can improve nutrient availability to plants, plantsoil-water relationships, seedling germination, and vascular plant growth (Johnston, 1997).
Though the importance of microbiotic crusts has long been recognized in arid
ecosystems, the growth sensitivities and requirements of individual organism types within the
communities is largely unknown. Soil properties such as pH, temperature, moisture and
conductivity influence crust presence (Johnston, 1997). Given that crust communities recover
very slowly once disturbed (Bowker, 2007), one strategy for restoring crusts is inoculating
disturbed soil with individual or mixed crust organisms (Lan et al., 2014). Knowing those
organisms’ growth requirements, and inoculating them in a healthy state, will be important for
restoration success (Johnston, 1997).
This study focused on sensitivity of green algae isolated from desert microbiotic crusts to
concentrations of macronutrients, micronutrients, and vitamins in their environment. Algae, like
any living thing, require certain nutrients in order to grow and thrive. Some nutrients are required
in large quantities (macronutrients), others in small quantities (micronutrients). Algae also need
certain organic compounds (vitamins) that they cannot synthesize themselves. Each of these
nutrients plays a different role in the many functions of the algal cell (Table 1), including
activating and composing enzymes and maintaining cellular integrity (Raven et al., 1999). For
example, key molecules like amino acids require nitrogen, while ATP relies on phosphorus.
Kanaskie 4
Autotrophs specifically require magnesium and iron to build the ring structure of chlorophyll.
Molybdenum plays a key role in nitrogen availability and in the splitting of water molecules in
photosynthesis (Ferreira et al., 2004).
Although there is much science to show that carbon and nitrogen fixation may be limited
by mineral nutrients or iron (Boyd et al., 2000), recent studies suggest that concentrations of
dissolved vitamins such as thiamin (B1), biotin (B7) and cobalamin (B12) may be limiting for
algal growth in much of the world ocean (Sanudo-Wilhelmy et al., 2014). Symbiotic bacteria can
provide algae with vitamin B12, synthesized only by bacteria, in exchange for carbon (Croft et
al., 2005; Amin et al., 2015), and anecdotal information gathered from crust organisms in Dr.
Zoe Cardon’s lab suggests that some algae can not growth well without bacteria (Cardon, pers.
comm.). Building on this information in a companion paper, Galyean examined whether the
prescence or absence of vitamins in culture affected the number of bacteria associated with
cultured cells of the desert-derived green algae Scenedesmus rotundus and Scenedesmus
deserticola. Here, I hypothesized that growth and photosynthesis of the same two algae would be
increased by the presence of vitamins and micronutrients in media.
Methods
I worked with two species of algae isolated from desert crusts, both eukaryotic,
unicellular green algae of class Chlorophyceae: Scenedesmus deserticola and Scenedesmus
rotundus (Lewis and Flechtner 2004). S. deserticola originated from San Nicolas Island,
California. San Nicolas Island is used for US Naval munitions testing, and was heavily grazed by
sheep until the mid-1900s (Schoenherr et al., 2003). S. rotundus originated from the Sevilleta
LTER in New Mexico. Both S. deserticola and S. rotundus have bacteria associated with them in
culture.
Kanaskie 5
We grew S. rotundus and S. deserticola in five variants of the standard algal culture
medium Bold’s Basal Medium (Bischoff and Bold 1963): BBM, BBM supplemented with
vitamins, BBM supplemented with micronutrients, BBM supplemented with both vitamins and
supplements, and half-strength BBM (Table 2). Each flask contained 50 mL of medium and 1
mL of algal inoculum obtained from cultures being grown by Dr. Elena Peredo. Media pH varied
between 6.6 and 6.9. We inoculated 3 Erlenmeyer flasks of each media variation for each species
of algae, for a total of 30 flasks. We placed the flasks on a New Brunswick Gyrotory G2 Orbital
Shaker (New Brunswick Scientific, Edison, NJ) in a Conviron CMP4030 growth chamber
(Conviron, Winnipeg, Canada) with a light level of 30 µE and temperature of 25 °C. Light days
were 16 hours long. We randomized the flasks on the shaker and swirled and moved the flasks
every two days for two weeks.
I quantified algal growth for S. deserticola using a hemocytometer to count cell numbers
at 2 weeks. These data were used to calibrate absorption measurements for S. deserticola (S.
rotundus cells clumped together naturally during growth, making hemocytometer measurements
impossible). I measured absorbance of 100 µL of each S. deserticola and S. rotundus culture at
440 nm in a Biotek Synergy H1 96-well plate reader (BioTek Instruments, Inc., Winooski, VT). I
measured quantum yield and non-photochemical quenching (calculated as NPQ) across a range
of light intensities in 1 mL of each culture using a Walz Dual-PAM 100 fluorometer (Heinz
Walz GmbH, Effeltrich, Germany) after 2 weeks of growth (Maxwell and Johnson, 2000). Light
intensities were 0, 4, 37, 531 and 0 µE red actinic light. All algae were dark-adapted overnight
prior to measurements. I calculated quantum yield and NPQ using the equations:
𝐹𝑚! − 𝐹
𝑄𝑢𝑎𝑛𝑡𝑢𝑚 𝑦𝑖𝑒𝑙𝑑 =
𝐹𝑚′
Kanaskie 6
𝑁𝑃𝑄 =
𝐹𝑚𝑎𝑥 − 𝐹𝑚′
𝐹𝑚′
Fm’ is the fluorescence induced by any saturating pulse other than the pulse eliciting the
maximum observed fluorescence, Fmmax. F is the fluorescence level before a saturating flash.
After collecting growth and fluorescence data, I then sacrificed two flasks from each
treatment for measurements of carbon:nitrogen ratios in the biomass. I filtered 50 mL of culture
and 200 mL of distilled water onto GFF filter disks, dried them for 72 hours at 60° C in a Fisher
Scientific Isotemp Oven (Thermo Fisher Scientific, Waltham, MA) and packed the dried filters
into aluminum capsules. I determined C:N ratio using a Thermo Scientific Flash 2000 CN
Analyzer (Thermo Fisher Scientific, Waltham, MA).
For statistical analysis of the repeated measurements of quantum yield, NPQ, and qNP at
multiple light levels, I used repeated measures ANOVA to test for effects of nutrient treatment
and light level in fluorescence data. I used one-way ANOVA and Tukey’s HSD to compare
absorbance & CHN data. Also, because dark-adapted quantum yield and maximum NPQ are
commonly reported characteristics in fluorescence studies, I used one-way ANOVA and Tukey’s
HSD to analyze the effect of treatment of dark-adapted quantum yield (no repeated measures)
and to analyze the effect of treatment on strength of NPQ at the highest level.
Results
After two weeks of growth, I found significant differences in the S. deserticola culture
absorbance within the 5 treatments. Treatments with micronutrients had higher absorbance
values than those without micronutrients (p ≤ 0.001), (Fig. 1). I saw no such trends in S. rotundus
culture absorbance data; treatment had no significant effect on absorbance after two weeks of
growth (p = 0.2086), (Fig. 2).
Kanaskie 7
I also saw differences in quantum yield across light levels (p ≤ 0.001) and treatments (p
= 0.002) in S. deserticola cultures. Treatments with micronutrients had higher quantum yield
than treatments without micronutrients (Fig. 3). Dark-adapted quantum yield was highest in
treatments with micronutrients, with values above 0.4 (Fig. 4). Yield declined at high light.
While quantum yield of S. rotundus overall seems elevated in comparison to S.
deserticola, I did not see significant differences between the treatments (p = 0.622). Quantum
yield differed between light levels, with the lowest yield at high light (p ≤ 0.001) (Fig. 5). I
measured dark-adapted quantum yield to be around 0.6 for all treatments (Fig. 6).
The presence of micronutrients also had an effect on non-photochemical quenching
(NPQ) in S. deserticola (Fig. 7). I saw differences between treatments (p ≤ 0.001) and between
light levels (p ≤ 0.001). At high light (531µE) (Fig. 8) and after exposure to high light, I found
NPQ to be highest in the ½ BBM treatment and lowest in the two micronutrient treatments. I saw
no significant differences in NPQ among treatments in S. rotundus (p = 0.762), but saw
differences between light levels (p ≤ 0.001) (Fig. 9). I saw no significant differences in NPQ at
high light (Fig. 10).
CHN analysis showed significant differences in carbon:nitrogen ratios between
treatments in S. deserticola (p = 0.007872), with the highest ratio in ½ BBM, and lowest in
BBM+Mn+Mo+vits (Fig. 11). I also saw significant differences in C:N ratios between treatments
in S. rotundus (p = 0.001371) (Fig .12).
Discussion
S. deserticola data supported my hypothesis that the presence of micronutrients in media
was associated with increased growth. The addition of vitamins did not have any anticipated
Kanaskie 8
growth effects. However, treatment had no effect on growth in S. rotundus cultures. This can be
attributed to the way S. rotundus grows in clumps, which caused variance in the data overall.
While S. rotundus quantum yield was higher than that of S. deserticola overall, I saw
significant trends in S. deserticola only. A clear divide emerged between treatments with and
without micronutrients, while vitamins had no effect on quantum yield. However, S. rotundus
grown in media without micronutrients had higher quantum yield than S. deserticola grown in
media with micronutrients. Thus, my results show that S. rotundus was more photosynthetically
efficient in this experiment than S. deserticola, but micronutrients increased the photosynthetic
efficiency of S. deserticola.
Interestingly, I found that S. rotundus also had higher non-photochemical quenching than
S. deserticola. NPQ can be thought of as a measurement of the algal perception of the amount of
excess light that must be dissipated to avoid damage of the cell. Non-photochemical quenching is
induced when the amount of light available outstrips the capacity of photosynthesis to use it all
to fix CO2. NPQ can be an indicator of algal stress. While S. rotundus had a higher quantum
yield than S. deserticola, S. rotundus NPQ was one order of magnitude higher than that of S.
deserticola at high light (531 µE) (Figs. 13, 14). I did not see any significant differences in NPQ
between treatments in S. rotundus cultures. NPQ decreased in S. deserticola culture as nutrient
availability increased at high light and in the dark after exposure to high light (Figs. 5, 6).
CHN analysis allowed me to assess the carbon:nitrogen ratio of each sacrifice culture. S.
deserticola data showed ½ BBM having the highest C:N ratio (24.6), while BBM+Mn+Mo+vits
had the lowest ratio (7.2). Other treatments were statistically similar. S. rotundus C:N ratios
showed significant differences between treatments without micronutrients or vitamins (~10) and
treatments with vitamins, micronutrients, or both (~6). These results suggest that S. rotundus
Kanaskie 9
was able to better assimilate nitrogen than S. deserticola, especially with the addition of vitamins
or micronutrients to media. However, vitamins and micronutrients together had no significant
effect on C:N ratio, and therefore, nitrogen assimilation.
In addition to testing my hypotheses, data such as these can be used in the realm of
restoration. Biological soil crusts are important parts of early successional stages of many
ecosystems and are especially important in arid and semi arid ecosystems. Although these crusts
are long lived and show high dessication tolerance, they can be delicate (Johnston, 1997). Cattle
grazing, tourist activity and military disturbances can compress and destroy crust communities.
Once disturbed, it can take anywhere from a decade to millennia to reestablish desert crust
communities (Cardon et al, 2008).
In many western American national parks, signage tells tourists “Don’t bust the crust!” in
attempts to reduce crust compaction and keep direct human activity to the trails. Currently,
USGS facilities such as the Canyonlands Research Station (CRS) are investigating improved
management practices to help protect the soil crusts. Understanding how to facilitate rapid
growth and sustained algal health can increase the success of restoration efforts of soil crusts in
deserts, on dunes, and in dry environments around the world. Paired with testing nutrient
availability of proposed restoration areas, this type of research will allow for more informed
decision-making, and can help combat desertification in arid and semi-arid environments around
the world. Increased soil stability and water retention due to healthy soil crusts can facilitate
vascular plant growth—which has the potential to increase the global food supply, and sequester
more carbon. These ecosystem services may become more important as climate change
continues to impact arid ecosystems.
Kanaskie 10
Thus, restoring soil crusts can assist in remediating many of today’s environmental
issues. We need to continue to investigate soil crusts and their many components, not only
because of their important role in arid and semi-arid ecosystems, but also for their potential to
address environmental issues globally
Acknowledgements
A very sincere thank you to Zoe Cardon for introducing me to the world of soil crusts, & to both
Zoe and Elena Lopez Peredo for their guidance and support from project creation to completion.
Many thanks to Tinsley Galyean, my collaborator. To the entire SES family, thank you for
sharing my excitement for learning and for teaching me new things every day.
Kanaskie 11
Literature Cited
Amin, S.A., L.R. Hmelo, H.M. van Tol, B.P. Durham, L.T. Carlson, K.R. Heal, R.L. Morales,
C.T. Berthiaume, M.S. Parker, B. Djunaedi, A.E. Ingalls, M.R. Parsek, M.A. Moran, and
E.V. Armbrust. 2015. Interaction and signaling between a cosmopolitan phytoplankton
and associated bacteria. Nature. 522:98-101.
Bischoff, H.W. and H.C. Bold. 1963. Some soil algae from enchanted rock and related algal
species. Phycological Studies IV., Univ. No. 6318, Texas, p.95
Bowker, M.A. 2007. Biological soil crust rehabilitation in theory and in practice: An unexplored
opportunity. Restoration Ecology 15:13-23.
Boyd, P.W., A.J. Watson, C.S. Law, E.R. Abraham, T. Trull, R. Murdoch, D.C.E. Bakker, A.R.
Bowie, K.O. Buesseler, H. Change, M. Charette, P. Croot, K. Downing, R. Frew, M.
Gall, M. Hadfield, J. Hall, M. Harvey, G. Jameson, J. LaRoche, M. Liddicoat, R. Ling,
M.T. Maldonado, R.M. McKay, S. Nodder, S. Pickmere, R. Pridmore, S. Rintoul, K.
Safi, P. Sutton, R. Strzepek, K. Tanneberger, S. Turner, A. Waite, and J. Zeldis. 2000. A
mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron
fertilization. Nature 407: 695-702.
Canyonlands Research Station (CRS). <www.soilcrust.org/ccers>
Cardon, Z. G., D.W. Gray, and L.A. Lewis. 2008. The Green Algal Underground: Evolutionary
Secrets of Desert Cells. Bioscience 58(2):114-122.
Cole, J.J., R.W. Howarth, S.S. Nolan, and R. Marino. 1986. Sulfate inhibition of molybdate
assimilation by planktonic algae and bacteria: some implications for the aquatic nitrogen
cycle. Biogeochemistry. 2:179-196.
Kanaskie 12
Croft, M.T., A.D. Lawrence, E. Raux-Deery, M.J. Warren, and A.G. Smith. 2005. Algae acquire
vitamin B12 through a symbiotic relationship with bacteria. Nature. 438: 90-93.
El-Sheekh, M.M., A.H. El-Naggar, M.E.H. Osman, and E. El-Mazaly. 2003. Effect of cobalt on
growth, pigments, and the photosynthetic electron transport in Monoraphidium minutum
and Nitzchia perminuta. Journal of Plant Physiology. 15(3):159-166.
Ferreira, K.N., T.M. Iverson, K. Maghlaoui, J. Barber, and S. Iwata. 2004. Architecture of the
Photosynthetic Oxygen-Evolving Center. Science 303: 1831-1838.
Johnston, R. 1997. Introduction to Microbiotic Crusts. USDA.
Lan, S., Q. Zhang, L. Wu, Y. Liu, D. Zhang, and C. Hu. 2014. Artificially Accelerating the
Reversal of Desertification: Cyanobacterial Inoculation Facilitates the Succession of
Vegetation Communities. Environ. Sci. Technol. 48: 307-315.
Lewis, L.A. and V.R. Flechtner. 2004. Cryptic species of Scenedesmus (Chlorophyta) from
desert soil communities of Western North America. Journal of Phycology. 40:1127-1137.
Maxwell, K.M. and G.N. Johnson. 2000. Chlorophyll fluorescence—a practical guide. Journal of
Experimental Botany 345:659-668.
Raven, P.H., R.F. Evert, and S.E. Eichnorn. 1999. Plant Nutrition and Soils, p. 727-731 in
Biology of Plants, Sixth Edition. W.H. Freeman and Company.
Sanudo-Wilhelmy, S.A., L. Gómez-Consarnau, C. Suffridge, and E.A. Webb. 2014. The Role of
B Vitamins in Marine Biogeochemistry. Annual Review of Marine Science. 6:339-67.
Schoenherr, A.A., C.R. Feldmeth, and M.J. Emerson. 2003. Natural History of the Islands of
California. University of California Press, Berkeley.
Smith, S.M., R.M.M. Abed, and F. Garcia-Pichel. 2004. Biological Soil Crusts of Sand Dunes in
Cape Cod National Seashore, Massachusetts, USA. Microbial Ecology. 16 June 2004.
Kanaskie 13
Song, A., P. Li, F. Fan, Z. Li, and Y. Liang. 2014. The effect of silicon on photosynthesis and
expression of its relevant genes in rice (Oryza sativa L.) under high-zinc stress. PLOS
ONE.
Kanaskie 14
Tables and Figures
Table 1. Nutrient roles in algae.
Table 2. Bold’s Basal Medium composition and various treatments.
Figure 1. S. deserticola culture absorbance at 440 nm after two weeks of growth.
Figure 2. S. rotundus culture absorbance at 440 nm after two weeks of growth.
Figure 3. S. deserticola quantum yield.
Figure 4. Dark adapted S. deserticola quantum yield at 0 µE. p = 0.6071
Figure 5. S. rotundus quantum yield
Figure 6. Dark adapted S. rotundus quantum yield at 0 µE. p = 0.6071
Figure 7. S. deserticola NPQ
Figure 8. S. deserticola NPQ at 531 µE (p<0.001)
Figure 9. S. rotundus NPQ
Figure 10. S. rotundus NPQ at 531 µE (p=0.7833)
Figure 11. S. deserticola carbon to nitrogen ratio.
Figure 12. S. rotundus carbon to nitrogen ratio p = 0.001371
Kanaskie 15
Table 1: Nutrient roles in algae. Adapted from Raven et al, 1999; Cole et al, 1986; Croft et al,
2005; El-Sheekh et al, 2003; Ferreira et al, 2004; Sanudo-Wilhelmy et al, 2014; Song et
al. 2004. Macronutrients are highlighted in blue, micronutrients in red, and vitamins in
green.
Nutrient
Role
Na
Nitrogen fixation, pH regulation
N
Component of amino acids, proteins, nucleotides, nucleic acid, enzymes
Ca
Component of cell walls, allows for membrane permeability, PSII water
oxidation, enzyme regulator
Cl
Involved in osmosis and ionic balance
Mg
Basis for chlorophyll molecule, enzyme activator
S
Amino acid, protein, and enzyme component
K
Involved in osmosis and ionic balance, enzyme activator
P
Component of ATP, ADP, nucleic acids, enzymes, phospholipids
Zn
Enzyme component and activator
Si
Alleviates photosynthetic stress caused by Zn, NaCl
B
Allows for Ca utilization, nucleic acid synthesis, membrane integrity
Cu
Redox enzyme component and activator
Co
Increases rate of photosynthesis
Mn
Enzyme activator, chloroplast integrity, oxygen release
Fe
Component of chlorophyll, cytochromes, nitrogenase
Mo
N fixation, nitrate reduction, PSII water oxidation
B1
Aids in metabolic reactions
B7
Enzyme component
B12
Enzyme component
Kanaskie 16
Table 2: Bold’s Basal Medium and treatment variations. Macronutrients are highlighted in blue,
micronutrients in red, and vitamins in green. Nutrients measured in mg/L.
BBM +
micronutrients +
vitamins
BBM
1/2 BBM
BBM +
vitamins
BBM +
micronutrients
Na
77.5
38.7
77.5
77.5
77.5
NO3
41.2
20.6
41.2
41.2
41.2
Ca
6.80
3.40
6.80
6.80
6.80
Cl
27.2
13.6
27.2
27.2
27.2
Mg
7.40
3.70
7.40
7.40
7.40
SO4
9.76
4.88
9.78
9.78
9.76
K
83.9
42.0
83.9
83.9
83.9
PO4
53.2
26.6
53.2
53.2
53.2
Zn
0.01365
0.01365
Si
0.00863
0.00863
B
0.00761
0.00761
Cu
0.000331
0.000331
Co
0.00136
0.00136
Mn
0.0203
0.0203
Fe
0.0688
0.0688
Mo
0.00238
0.00238
B1
0.100
0.100
B7
0.000500
0.000500
B12
0.000500
0.000500
Kanaskie 17
0.6
S.deserticola
b
b
Absorbance at 440 nm
0.5
0.4
0.3
a
a
a
BBM
BBM+vits
0.2
0.1
0
1/2 BBM
Treatment
Figure 1.
BBM+Mn+Mo BBM+Mn+Mo+vits
Kanaskie 18
0.6
S.rotundus
Absorbance at 440 nm
0.5
0.4
a
a
a
a
0.3
a
0.2
0.1
0
1/2 BBM
BBM
BBM+vits
Treatment
Figure 2.
BBM+Mn+Mo BBM+Mn+Mo+vits
Kanaskie 19
0.8
S.deserticola
0.7
Quantum Yield
0.6
0.5
1/2BBM
0.4
BBM
BBM+vits
0.3
BBM+Mn+Mo
0.2
BBM+Mn+Mo+vits
0.1
0
0
4
37
Light (uE)
Figure 3.
531
0
Kanaskie 20
0.8
S.deserticola
Dark-adapted Quantum Yield
0.7
0.6
bc
0.5
0.4
a
b
acd
a
d
0.3
0.2
0.1
0
1/2BBM
BBM
BBM+Vits
Treatment
Figure 4.
BBM+Mn+Mo
BBM+Vits+Mn+Mo
Kanaskie 21
0.8
S.rotundus
0.7
Quantum Yield
0.6
0.5
1/2BBM
0.4
BBM
BBM+vits
0.3
BBM+Mn+Mo
0.2
BBM+Mn+Mo+vits
0.1
0
0
4
37
Light (uE)
Figure 5.
531
0
Dark-adapted Quantum Yield
Kanaskie 22
0.8
S.rotundus
0.7
a
a
a
a
a
0.6
0.5
0.4
0.3
0.2
0.1
0
1/2BBM
BBM
BBM+Vits
Treatment
Figure 6.
BBM+Mn+Mo
BBM+Vits+Mn+Mo
Kanaskie 23
0.5
S.deserticola
0.45
0.4
0.35
1/2BBM
NPQ
0.3
BBM
0.25
BBM+Vits
0.2
BBM+Mn+Mo
0.15
BBM+Vits+Mn+Mo
0.1
0.05
0
0
4
37
Light (uE)
Figure 7.
531
0
Kanaskie 24
0.5
NPQ at 531 µmol photons m-2 s-1
0.45
S.deserticola
a
0.4
0.35
b
0.3
bd
0.25
cd
0.2
c
0.15
0.1
0.05
0
1/2BBM
BBM
BBM+Vits
Treatment
Figure 8.
BBM+Mn+Mo
BBM+Vits+Mn+Mo
Kanaskie 25
2
S.rotundus
1.8
1.6
1.4
1/2BBM
NPQ
1.2
BBM
1
0.8
BBM+Vits
0.6
BBM+Mn+Mo
0.4
BBM+Vits+Mn+Mo
0.2
0
0
4
37
Light (uE)
Figure 9.
531
0
Kanaskie 26
NPQ at 531 µmol photons m-2 s-1
2.5
2
S.rotundus
a
a
a
a
1.5
a
1
0.5
0
1/2BBM
BBM
BBM+Vits
Treatments
Figure 10.
BBM+Mn+Mo
BBM+Vits+Mn+Mo
Kanaskie 27
30
S.deserticola
c
abc
25
C:N ratio
20
ab
15
ab
a
10
5
0
BBM
1/2 BBM
BBM+vits
Treatment
Figure 11.
BBM+Mn+Mo BBM+Mn+Mo+vits
Kanaskie 28
14
S.rotundus
a
12
C:N ratio
10
a
8
b
b
b
6
4
2
0
1/2 BBM
BBM+vits
BBM
BBM+Mn+Mo
Treatment
Figure 12.
BBM+Mn+Mo
+vits