Patchy and Pink: Dynamics of a Chlainomonas sp. (Chlamydomonadales, chlorophyta) algal bloom on Bagley Lake, North Cascades, WA

Abstract

Snow algal blooms frequently occur throughout alpine and polar environments during spring and summer months; however, our understanding of bloom dynamics is limited. We tracked a recurrent bloom of Chlainomonas sp. on Upper Bagley Lake in the North Cascade Mountains, USA, to assess the spatiotemporal dynamics in bloom color intensity, community photophysiology, and community composition over eight weeks. We found that the algae biomass had a dynamic patchy distribution over space and time, which was decoupled from changes in community composition and life-cycle progress averaged across the bloom. The proportional representation of Chlainomonas sp. remained consistent throughout the study while the overall community composition shows a progression through the bloom. We found that community photophysiology, measured by the maximum quantum yield of PSII (Fv/Fm), decreased on average throughout the bloom. These findings suggest that the Chlainomonas sp. community on Bagley Lake is not simply an algal bloom with rapid increase in biomass followed by a population crash, as is often seen in aquatic systems, though there is a physiological trajectory and sensitivity to environmental stress. These results contribute to our understanding of the biology of Chlainomonas sp. and its response to environmental stress, specifically an extreme warming event.

Keywords: Chlainomonas sp; blooms; dynamics; photophysiology; snow algae.

Figure 1.

A map showing sampling locations A-H situated on Lower Bagley Lake in the Cascade Range, Washington USA. This map was created in ArcGIS. Inset map shows the broader geographic context for the location of this study.

Figure 2.

Environmental Data (temperature and light) measured across Bagley Lake in 2021. Snow surface temperature and light recorded by 3 Hobo loggers placed across the study site (1310 m) elevation and averaged. Ambient air temperature recorded by Northwest Avalanche Center telemetry station at Heather Meadows (1280 m elevation) located approx. 1 km from center of Upper Bagley Lake. A) Daily average (n = 3, means +/− SE) surface snow temperatures (minimum (blue) ambient maximum ambient air temperature (red)) for the area. B) Maximum daily light intensity (μmol m⁻² s⁻¹) (n = 3, means +/− SE). Vertical blue lines show the location of the atmospheric heat dome that occurred during week 6.

Figure 3.

Representative Chlainomonas sp. cell morphologies found throughout the 2021 bloom, all of which have been observed as part of the life cycle (Matsumoto et al in review). All scale bars are 60 μm. A) Large Chlaionomonas sp. cell with thin cell wall and visible central nucleus 05/20/21 (Week 0) first visible patches of the bloom; B) Common non-motile vegetative Chlaionomonas sp. cell with thick cell wall 05/20/21 (Week 0) first visible patches of the bloom; C) Small Chlaionomonas sp. cell morphology with condensed cell contents 05/25/21 (Week 1) from site C; D) Image of 3 Chlaionomonas sp. cells with morphology and size variation co-exiting along with a cell undergoing the unique cell division from a single patch collected on 07/06/21 (Week 7) from site E; E) Three common Chlaionomonas sp. morphologies co-existing in a patch collected on 06/16/21 (Week 4) from site G; F) Rafted Chlaionomonas sp. spore morphologies co-existing with the common vegetative cell morphology in a single patch collected on 06/22/21 (Week 5) from site D; G) The rare Chlaionomonas sp. morphology with dense cell contents and think orange layer around cytoplasm collected on 07/06/21 (Week 7) from site E; H) A single Chlaionomonas sp. spore morphology showing thickened cell wall collected on 07/13/21 (Week 8) from site C.

Figure 4.

Morphology of fungi/chytrid infections during bloom. A) Chionaster sp. collected on 052521 (Week 1) from site D.; B) Small infected Chlainomonas sp. cell with round fruiting body collected on 05/25/21 (Week 1) from site A; C) Larger infected Chlainomonas sp. with parietal green spots collected on 06/16/21 (Week 4) from Site H. Small round fruiting bodies penetrating cell wall; D) Severely infected Chlaionomonas sp. cell with multiple triangular fruiting bodies collected on 06/08/21 (Week 3) from Site D (left) and lysing cell (right)​; E) Infected Chlaionomonas sp. cell showing triangular fruiting bodies penetrating cell wall, collected on 06/16/21 (Week 4) from Site F; F) Infected Chlaionomonas sp. cell showing hyphae and fruiting body collected on 06/08/21 (Week 2) from site A; G) Infected Chlaionomonas sp. cell showing small round fruiting bodies on 06/29/21 (Week 6) from Site C ; H) Infected Chlaionomonas sp. undergoing unique cell division with parent cell showing small round fruiting bodies collected on 06/29/21 (Week 6) from Site G; I) Infected Chlaionomonas sp. showing multiple round fruiting bodies penetrating cell wall collected on 07/06/21 (Week 7) from site C.

Figure 5.

18S V9 amplicon data from each sample, by week. ASVs assigned to the same taxonomic group are binned and the n is of ASV summed in that group. If no n is listed, only a single ASV contributed group. Vertical blue lines show the location of the atmospheric heat dome that occurred during week 6.

Figure 6.

A) Maximal photochemical efficiency of PSII (Fv/Fm). Measurements taken each week of 8 weeks. B) Cell counts of snow used to measure chlorophyll fluorescence (cells/ml). Measurements taken weeks 2–6. C) log-transformed integrated density of color of pink patches on surface snow. Measurements taken weeks 1–2, and 4–7. Week 3 was omitted due to recent snow fall that obscured surface patches. Letters represent significant differences among weeks in each panel determined with an ANOVA and Tukey post-hoc analysis (P < 0.05). Vertical black lines show the location of the atmospheric heat dome that occurred during week 6.

Figure 7.

Heat map showing bloom intensity across Bagley Lake, Washington State in the spring and summer of 2021. Numbers in the upper-left corner of each panel correspond to sampling weeks. We omitted week 3 from the survey due to snowfall the day before that obscured the bloom. Bloom intensities ranged from 0 to 4. Blacked out areas were omitted from the survey due to either obstructions or lack of snow in later weeks. No survey was done during week eight because the bloom had degraded and could not be traversed.