The structuring role of three types of macrophytes on the … · 2019-11-13 · Freshwater Algae:...
Transcript of The structuring role of three types of macrophytes on the … · 2019-11-13 · Freshwater Algae:...
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The structuring role of three types of macrophytes on the planktonic
communities of lake San Pablo, a tropical freshwater Andean system in
Northern Ecuador
Francisco Caicedo, Iris Stiers, Ludwig Triest
Photo source: the author
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Figure 1: Upper part: modified from (Casallas, 2005)Lower photo: author´s photo
Human threats
• Intensive agriculture
• Exotic fish
• “Totora” harvesting
• No environmental awareness
Current state
• Eutrophic lake
• Almost dead bellow 15 meters of depth
• Practically anoxic bottom
Lake San Pablo: an Andean-monomictic system
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Lake San Pablo: its littoral zone
Figure 2: Schematic profile of macrophyte distribution in Lake San Pablo during 1996. Modified from Gunkel (2000).
Distance from shore (m)
Dep
th (
m)
- Ceratophyllum demersum
- Potamogeton striatus
- Myriophyllum quitense
- Potamogeton illinoensis
Emergent type: Schoenoplectus californicus
Floating type: Eichhornia crassipes
Submerged type:
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Figure 3: Schematic representation of a shallow lake. Modified from Scheffer (2004). 4
The role of macrophytes (specially the submerged type)
Vegetation-dominated clear state
Phytoplankton-dominated turbid state
Lake San Pablo, July 2017
Lake Yahuarcocha, July 2019
Figure 4: author´s photos.
Nutrients
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To investigate the role of emergent, submerged and floatingmacrophytes, their coverage and associated environmental variableson the phytoplankton and zooplankton community structures
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Objective:
Methodology:
Open waters (n = 8)Submerged (n = 6)Emergent (n = 5)Floating (n = 1)
• Environmental parameters
• Phytoplankton biovolume
• Zooplankton density
• Non-parametric statistics
• Species richness and diversity (Shannon-Wiener
• Principal Component Analysis (PCA)
• Variation partitioning
Figure 5: Sampling sites in lake San Pablo
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Figure 7: Boxplots of phytoplankton richness, diversity and biovolume alongthe open water-vegetation gradient.
ab
b
a
b
b
a
ab
b
a
Spe
cies
Ric
hn
ess
Shan
no
n d
ive
rsit
yin
dex
(H´)
Bio
volu
me
(mm
3/L
)
Open Submerged Emergent Floating
Open Submerged Emergent Floating
Open Submerged Emergent Floating
KW: x2= 6.61; p = 0.037
KW: x2= 8.4; p = 0.014
KW: x2= 13.24; p = 0.001
Results: Phytoplankton biovolume
Figure 6: Upper plot: boxplots of the most important RFGs.Lower photos: taken from Canter-Lund, H. Lund, J.(1995).
Benthic diatoms only
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Phytoplankton ZooplanktonFactors Variation explained
(%)p-
valueVariation explained
(%)p-value
[ENV + VECO] 48.5 0.001 66 0.001[ENV] 25.3 0.007 15.7 0.003[VECO] 14.1 0.010 40 0.001[ENV│VECO] 33.4 0.004 26 0.019
[VECO│ENV] 23.2 0.011 50.3 0.001[ENV ∩ VECO] 9.1 N/T 10.3 N/T1 − [ENV +VECO] 51.5 N/T 34 N/T
Table 1: Variation partitioning and associated p-values of phytoplanktonbiovolume and zooplankton densities into the different factors
Den
sity
(in
d/L
)
Figure 8 Grouped barplot of the zooplankton density alongthe open water-vegetated gradient.
Open Submerged Emergent
Group
DO (mg) Turbidity (NTU)
Open Water 2.74 (0.08)a 1.45 (0.15)a
Submerged 3.18 (0.18)a 2.65 (0.46)b
Emergent 2.03 (0.17)b 2.532 (0.5)b
p-value 0.0023 0.024
Table 2: Limnological parameters displaying significant differences among sampling zones
Results: Zooplankton densityand environmental parameters
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Conclusions: effects of macrophytes on the phytoplankton community
• Enhanced diversity and species richness
• Benthic algae (adapted to turbulence)
• Negligible cyanobacteria (July 2017)
• Cyanobacteria periodicity (2017, 2018, 2019)
• Nutrient uptake (resilience mechanism)
Figure 9: phytoplankton from lake San Pablo (author´s photos)
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Conclusions: effects of macrophytes on the zooplankton community
Figure 10: zooplankton from lake San Pablo (author´s photos)
• Higher diversity and density
• Cladocerans find shelter and food
• Oxygen attracts other aquatic organisms
• Horizontal replaced vertical migration
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Research is needed!
Figure 11: Author´s photo
• The impacts of global warming
• Fish baseline and their feeding behavior
• Environmental awareness and law enforcement
• To expand this investigation in a temporal scale
• Potential of constructed wetlands for water treatment
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Management of lake San Pablo
good agricultural practices
healthy aquatic ecosystems
efficient water treatment
involvement of local authoritiesand population
Coupling of different approaches and inter-institutional cooperation are required to achieve a wise management of an aquatic system (Hampel et al., 2015).
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• Canter-Lund, H., Lund, J. (1995). Freshwater Algae: Their Microscopic World Explored.Biopress Limited
• Casallas, J. (2005). Limnological investigations in Lake San Pablo, a high mountain lake in Ecuador. Technischen Universität Berlin.
• Gunkel, G. (2000). Limnology of an Equatorial High Mountain Lake in Ecuador, Lago San Pablo. Limnologica, 30(2), 113–120. https://doi.org/10.1016/S0075-9511(00)80005-5
• Hampel, H., Cocha, J., & Vimos, D. (2015). Incorporation of aquatic ecology to the hydrological investigation of ecosystems in the high Andes. Maskana, 1(1), 91–100.
• Scheffer, M. (2004). Ecology of Shallow Lakes. https://doi.org/10.1007/978-1-4020-3154-0
• http://www.mining.com/ecuador-mining-industry-to-grown-eightfold-by-2021-report/
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References
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Thank you for your attention!