Spring Algae Research Articles

Cultivable Winogradskyella species are genomically distinct from the sympatric abundant candidate species

Winogradskyella is a genus within the phylum Bacteroidetes with a clear marine origin. Most members of this genus have been found associated with marine animals and algae, but also with inorganic surfaces such as sand. In this study, we analyzed genomes of eleven species recently isolated from surface seawater samples from the North Sea during a single spring algae bloom. Corresponding metagenomes yielded a single Candidatus species for this genus. All species in culture, with the exception of W. ursingii, affiliated with a Winogradskyella lineage characterized by large genomes (~4.3 ± 0.4 Mb), with high complexity in their carbohydrate and protein degradation genes. Specifically, the polysaccharide utilization loci (PULs) were diverse within each individual strain, indicating large substrate versatility. Although present in the North Sea, the abundances of these strains were at, or below, the detection limit of the metagenomes. In contrast, the single species, classified as Candidatus W. atlantica, to which all North Sea MAGs belonged, affiliated with a lineage in which the cultivated representatives showed small genomes of ~3.0–3.5 Mb, with the MAGs having ~2.3 Mb. In Ca. W. atlantica, genome streamlining has apparently resulted in the loss of biosynthesis pathways for several amino acids including arginine, methionine, leucine and valine, and the PUL loci were reduced to a single one for utilizing laminarin. This as-yet uncultivated species seems to capitalize on sporadically abundant substrates that are released by algae blooms, mainly laminarin. We also suggest that this streamlined genome might be responsible for the lack of growth on plates for this Candidatus species, in contrast to growth of the less abundant but coexisting members of the genus.

In marine Bacteroidetes the bulk of glycan degradation during algae blooms is mediated by few clades using a restricted set of genes

We investigated Bacteroidetes during spring algae blooms in the southern North Sea in 2010–2012 using a time series of 38 deeply sequenced metagenomes. Initial partitioning yielded 6455 bins, from which we extracted 3101 metagenome-assembled genomes (MAGs) including 1286 Bacteroidetes MAGs covering ~120 mostly uncultivated species. We identified 13 dominant, recurrent Bacteroidetes clades carrying a restricted set of conserved polysaccharide utilization loci (PULs) that likely mediate the bulk of bacteroidetal algal polysaccharide degradation. The majority of PULs were predicted to target the diatom storage polysaccharide laminarin, alpha-glucans, alpha-mannose-rich substrates, and sulfated xylans. Metaproteomics at 14 selected points in time revealed expression of SusC-like proteins from PULs targeting all of these substrates. Analyses of abundant key players and their PUL repertoires over time furthermore suggested that fewer and simpler polysaccharides dominated early bloom stages, and that more complex polysaccharides became available as blooms progressed.

Genomic and physiological analyses of 'Reinekea forsetii' reveal a versatile opportunistic lifestyle during spring algae blooms.

Gammaproteobacterial Reinekea spp. were detected during North Sea spring algae blooms in the years 2009-2012, with relative abundances of up to 16% in the bacterioplankton. Here, we explore the ecophysiology of 'R. forsetii' strain Hel1_31_D35 that was isolated during the 2010 spring bloom using (i) its manually annotated, high-quality closed genome, (ii) re-analysis of in situ data from the 2009-2012 blooms and (iii) physiological tests. High resolution analysis of 16S rRNA gene sequences suggested that 'R. forsetii' dominated Reinekea populations during these blooms. This was corroborated by retrieval of almost complete Hel1_31_D35 genomes from 2009 and 2010 bacterioplankton metagenomes. Strain Hel1_31_D35 can use numerous low-molecular weight substrates including diverse sugar monomers, and few but relevant algal polysaccharides such as mannan, α-glucans, and likely bacterial peptidoglycan. It oxidizes thiosulfate to sulfate, and ferments under anoxic conditions. The strain can attach to algae and thrives at low phosphate concentrations as they occur during blooms. Its genome encodes RTX toxin and secretion proteins, and in cultivation experiments Hel1_31_D35 crude cell extracts inhibited growth of a North Sea Polaribacter strain. Our data suggest that the combination of these traits make strain Hel1_31_D35 a versatile opportunist that is particularly competitive during spring phytoplankton blooms.

The Life History and Other Ecology ofCamelobaetidius variabilis(Ephemeroptera: Baetidae) From Honey Creek, Oklahoma

A study of the life history and ecology of Camelobaetidius variabilis was conducted in Honey Creek, Oklahoma, from February 2003–April 2004. C. variabilis exhibited a multivoltine life cycle with five overlapping generations. Ninety percent of lab-reared eggs hatched at 130 degree days (DD) (23 °C) while nymphs successfully emerged at 559 DD at 20.8 ± .38 °C. Microhabitat preference of C. variabilis nymphs was statistically significant for algae during the spring. Nonmetric multidimensional scaling analysis showed 90% similarity between spring algae, winter leaf packs, fall open bedrocks, and summer divets based on average number of nymphs by developmental stage. Winter leaf packs exposed to shade and sunlight were sampled and total number of nymphs counted. Leaf packs exposed to direct sunlight contained higher numbers of nymphs compared to those in shaded areas. Further internal temperature analysis of leaf packs exposed to sunlight showed an increase in internal leaf pack temperatures compared to ambient water temperature during the winter. C. variabilis nymphs have a varied microhabitat use depending upon season. Since they are scrapers, algae and periphyton are important food resources throughout the year.

Recurring patterns in bacterioplankton dynamics during coastal spring algae blooms

A process of global importance in carbon cycling is the remineralization of algae biomass by heterotrophic bacteria, most notably during massive marine algae blooms. Such blooms can trigger secondary blooms of planktonic bacteria that consist of swift successions of distinct bacterial clades, most prominently members of the Flavobacteriia, Gammaproteobacteria and the alphaproteobacterial Roseobacter clade. We investigated such successions during spring phytoplankton blooms in the southern North Sea (German Bight) for four consecutive years. Dense sampling and high-resolution taxonomic analyses allowed the detection of recurring patterns down to the genus level. Metagenome analyses also revealed recurrent patterns at the functional level, in particular with respect to algal polysaccharide degradation genes. We, therefore, hypothesize that even though there is substantial inter-annual variation between spring phytoplankton blooms, the accompanying succession of bacterial clades is largely governed by deterministic principles such as substrate-induced forcing.

Quantifying emissions of methane derived from anaerobic organic matter respiration and natural gas extraction in Lake Erie

AbstractDespite a growing awareness of the importance of inland waters in regional and global carbon (C) cycles, particularly as sources of the greenhouse gases carbon dioxide (CO2) and methane (CH4), very little is known about C sources and fluxes in the Laurentian Great Lakes, Earth's largest surface freshwater system. Here, we present a study of CH4 dynamics in Lake Erie, which has large spring algae blooms linked to fertilizer runoff and followed by hypoxia, as well as an extensive network of natural gas wells and pipelines in Canadian waters. Lake Erie is a positive source of CH4 to the atmosphere in late summer, even in shallow regions without water column hypoxia. Stable isotopic measurements indicate that both biogenic and thermogenic CH4 contribute to emissions from Lake Erie. We estimate that Lake Erie emits 1.3 ± 0.6 × 105 kg CH4‐C d−1 in late summer, with approximately 30% of CH4 derived from natural gas infrastructure. Additional work is needed to determine the spatial and temporal dynamics of CH4 emissions from Lake Erie and to confirm estimates of source contribution. Studies of the C cycle in large lakes are not as straightforward as those in smaller lakes, as, in addition to O2 availability, subsurface currents and high winds may exert significant control over dissolved CH4 patterns. If climate warming and increasing precipitation intensity lead to increased algal biomass and/or greater extent and duration of hypoxia, this may increase emissions of CH4 from Lake Erie in a positive feedback to climate change.

Herbivory and seasonal changes in diet of a highly endemic cyprinodontid fish (Aphanius farsicus)

Trophic ecology is essential to understand ecosystem functioning and structure and assist biological conservation. Here we investigate, for the first time, the feeding ecology of Aphanius farsicus, a cyprinodontid fish endemic of a single landlocked river basin in central Iran. We sampled monthly a population of this fish species during a year and examined differences in food across seasons, sexes and sizes. Similarly to other cyprinodonts, A. farsicus showed sexual dimorphism and more abundance of females. Size structure and individual condition varied across seasons, with larger fish in spring and better condition in summer and less in winter. We found no empty guts, suggesting that these fish feed all year round due to the warm climate of its native distribution. Farsi toothcarp diet was based on detritus, algae (particularly diatoms, green algae, and cyanobacteria), and small invertebrates. Seasonal variation in diet was more important than variation due to fish size and the Farsi toothcarp consumed more green algae in spring and early summer and more diatoms and insects the rest of the year. Herbivory was considerable, similarly to a few other cyprinodonts, and increased with fish size, particularly because of higher consumption of green algae. As with species composition in diet, season was more important than size in the variation of number, biovolume, mean size, and diversity of prey captured, with higher number, richness and size of prey captured in summer. The ontogenetic diet shift was less marked in this cyprinodont than in many other Aphanius species, probably due to its reduced size and the resource availability of its habitat, but was also shown by size-dependent feeding selectivity for a few invertebrates.

Seasonal variation and distribution characteristics of heavy metals in phytoplankton of different parts of Lake Taihu

In recent years,the content of heavy metals in waste water which is discharged into Lake Taihu has been increasing continuously. In order to study the contamination status of heavy metals in phytoplankton of Lake Taihu,investigations were carried out in different parts of the lake in spring( April),summer( July) and winter( December),2009. During the research,hierarchical cluster analysis( HCA) and Pearson correlation analysis were used to discuss the seasonal variation of heavy metals in phytoplankton in different parts of the lake. Canonical correspondence analysis( CCA) with dominant algae was applied to make a preliminary study of the relationship between heavy metals in phytoplankton and each alga. The results indicated that the sequence of heavy metals content in phytoplankton was Zn Mn Pb Cu Ni Cr As Cd Hg. Besides,the seasonal variation of Zn,Cu,Mn,Pb and Ni was obvious and there's strong dependency between Cu,Pb,Ni,Cr and Zn,which reveals their homology dramatically.By comparing different parts of Lake Taihu,the content of heavy metals in phytoplankton was discovered the highest in the North Bay and the content in east and center of the lake was lower than that in lakeshore district. Based on the CCA results,generally there's a positive correlation between heavy metals and dominant algae in spring,while a negative correlation in summer and winter on the contrary. What's more,it shows that heavy metals have the highest correlation with Cyanophyta and Chlorophyta and the lowest correlation with Cryptophyta. Among Cyanophyta,heavy metals have a higher correlation with Microcystis aeruginosa than those with Microcystis flos-aquae.

Importance of ice algal production for top predators: new insights using sea-ice biomarkers

Antarctic seals and seabirds are strongly dependent on sea-ice cover to complete their life history. In polar ecosystems, sea ice provides a habitat for ice-associated diatoms that ensures a substantial production of organic matter. Recent studies have presented the potential of highly branched isoprenoids (HBIs) for tracing carbon flows from ice algae to higher-trophic-level organisms. However, to our knowledge, this new method has never been applied to sub-Antarctic species and Antarctic seals. Moreover, seasonal variations in HBI levels have never been investigated in Antarctic predators, despite a likely shift in food source from ice-derived to pelagic organic matter after sea-ice retreat. In the present study, we described HBI levels in a community of seabirds and seals breeding in Adelie Land, Antarctica. We then validated that sub-Antarctic seabirds had lower levels of diene, a HBI of sea-ice diatom origin, and higher levels of triene, a HBI of phytoplanktonic origin, compared with Antarctic seabirds. Finally, we explored temporal changes in HBI levels after the ice break up in summer. The level of diene relative to triene in Adelie penguin chicks increased and then declined during the breeding season, which was consistent with the short and intense proliferation of sea-ice algae in spring, followed by the pelagic phytoplankton bloom in summer. HBI biomarkers in Antarctic seabirds and seals thus indicate a shift from ice-algal derived organic matter to a pelagic carbon source during the summer breeding season.

Phytoplankton trends in the Great Lakes, 2001–2011

We describe recent trends in phytoplankton composition and abundance in the Laurentian Great Lakes using synoptic spring (April) and summer (August) sampling events from 2001 through 2011, a period of rapid shifts in pelagic food webs and water quality. Data analysis identified qualitative and quantitative changes in algal densities, biovolume, and taxonomic composition of assemblages. Since 2001, Lake Superior has changed subtly with an increase in small-celled blue-green algae in spring and a recent decline in summer centric diatoms, possibly a result of lake warming and changes in water quality. Spring phytoplankton declines mainly attributed to diatoms occurred in Lakes Huron and Michigan, a probable result of invasions by non-native dreissenids that have reduced pelagic nutrients and selectively consumed certain taxa. The decline in Lake Huron's spring phytoplankton biovolume was earlier and more severe than that in Lake Michigan, despite a faster and more abundant dreissenid invasion in Lake Michigan. Lake Erie's central basin had a notable increase in spring centric diatoms (largely Aulacoseira), while the whole of Lake Erie shows a summer increase in cyanobacteria, complementing that found in coastal regions. The composition of Lake Ontario's species assemblage shifted, but little overall change in algal abundance was observed with the exception of higher summer densities of cyanophytes. Additional mechanisms for shifts in the pelagic primary producers are described or hypothesized in the context of concurrent shifts in water quality and invertebrate populations. Tracking these trends and explaining driving factors will be critical to the management of lake conditions.

The absorption spectral decomposition of water in Lake Taihu, China (Ⅱ):the decomposition of absorption due to phytoplankton pigments

蓝藻水华暴发前,浮游植物群类结构的变化可通过其指示型色素的浓度变化来反映.为了同时反演叶绿素a、叶绿素b(绿藻门指示型色素)、叶绿素c(硅藻门指示型色素)和藻蓝素(蓝藻门的指示型色素)的浓度,利用偏最小二乘回归构建线性模型,通过2011年太湖实测吸收数据,较为准确地反演了叶绿素a和藻蓝素的浓度;针对无明显优势藻的春季数据集较为准确地反演了叶绿素b和叶绿素c的浓度.相对于经典最小二乘算法,偏最小二乘法在多色素混合的吸收光谱分析上更为有效.通过反演指示性色素浓度来反映藻类的分布,为富营养化湖泊主要藻类时空分布变化的遥感监测提供了一定的理论与技术支持.;Concentrations of pigments could reflect the dominant phyla of algae. Investigations of algae in eutrophic lakes revealed that Chl. b, Chl. c and phycobilin (PC) are the critical pigments of chlorophyta, bacilliariphyta and cyanophyta, respectively. In this study, partial least square (PLS) regress was used on the retrieval of Chl. a, Chl. b, Chl. c and PC through absorption spectral of phytoplankton. Retrieve of Chl. a was based on the data collected in situ during 2011. Retrieve of Chl. b and Chl. c was based on the data collected in situ in March, since there is no significant dominant phyla of algae in spring. Result shows that PLS is a more effective method than the original least square regress and could be of help for remote sensing of multi-pigments and the distribution of main algae in eutrophic lakes.

Correlation of Asian dust with chlorophyll and primary productivity in the coastal seas of China during the period from 1998 to 2008

[1] Satellite chlorophyll a (Chl a) concentrations and estimated primary production in the coastal seas of China were correlated with Asian dust events during 1998–2008. Dust events were identified using two approaches, i.e., historical record and satellite aerosol index (AI). Severe and very severe dust events correlated well and positively with Chl a concentrations and primary production in the south Yellow Sea and East China Sea, but it was not statistically significant in the Bohai Sea and the north Yellow Sea. In the south Yellow Sea, Chl a concentration and primary production increased and eventually bloomed 1–21 days after the occurrence of the 16 out of 22 dust storms. Granger causality test showed that AI, photosynthetically available radiation (PAR) and sea surface temperature (SST) did Granger cause primary production in the Yellow Sea, suggesting that past values of the above three variables contain statistically meaningful information about current values of primary production. A stepwise multiple linear regression was used to examine the relative importance of the three factors. PAR and SST accounted for most of the variability of primary production in the north Yellow Sea, while AI was not quite as useful. In the south Yellow Sea, PAR and AI accounted for most of the variability of primary production for all storms; in addition, spring algae blooms were due to dust particles transported in the 5 km) dusts, originated mainly from the Taklimakan Desert, Mongolia, and/or west of Inner Mongolia, had no impact.

The recent invasion of Rutilus rutilus (L.) (Pisces: Cyprinidae) in a large South- Alpine lake: Lago Maggiore

Very recently, a common cyprinid fish species at northern latitude, the roach (Rutilus rutilus L.) has been observed in the large south-alpine Lago Maggiore for the first time. The colonization of the lake has the characteristics of an invasion. In order to investigate this new fish population, benthic multi-mesh and commercial gill nets were used to sample fish in a wide gulf in the central part of the lake (Golfo Borromeo) from February to October 2006. In total 779 roach (TL: 5.5 – 38.8 cm) were caught, aged, sexed and stomach analyzed. Fecundity was assessed by counting the eggs in ripe gonads of females of age 3 and 4. The roach have become clearly the dominant species in the catches, constituting over 70% of the biomass and 70% of the numbers caught. None of the roach exceeded 8 years in age. They grow very fast (Φ' = 2.55) and have high fecundity (Fabs = 13740 ±4700 S.D. at age 3 and Fabs = 14768 ±5642 S.D. at age 4). The diet spectrum is wide and characterized by a strong seasonality. In early spring algae (benthic and planktonic algae), benthos and detritus prevail, whereas in summer zooplankton is the most frequent food item. In autumn roach switch back to benthos and detritus. Algae occur more frequently in young specimens while zooplankton, benthos and detritus in adults. The roach population is practically unimpacted by fishing. The minimum legal mesh size (25 mm) of gillnets, used by commercial fishermen, selects roach at the mean LT of 21.2 cm, which is over its length at maturity. The results suggest that roach established a viable population in Lago Maggiore less than a decade ago and rapidly became one of the dominant (if not the dominant) fish species. The possible consequence for the fish fauna in general and for the ecological status of the whole lake is briefly discussed.

Occurrence and transport of polycyclic aromatic hydrocarbons in the water bodies of the Baltic Sea

Between 1992 and 1998, 313 seawater samples were collected in the surface microlayer , the surface water and the deep water of the Baltic Sea. Fifteen individual parent polycyclic aromatic hydrocarbons (PAHs) were analyzed at 41 different coastal and offshore stations. The study has provided the most comprehensive information available to date about PAHs in different water bodies of the Baltic Sea. In general, the levels of the PAHs in Baltic Sea water were below 20,000 pg/l for the sum of 15 PAHs. Higher concentrations were found in estuarine samples. One local source in the southern Baltic Sea is the River Oder. Hot spots were observed mainly in the western Baltic Sea. In particular, high concentrations of the two- and three-ring PAHs were detected. Phenanthrene , fluoranthene and pyrene were the major components in surface water of the Baltic Sea. PAH composition profiles were compared to establish whether different water bodies of the Baltic have characteristic PAH patterns originating from characteristic inputs. Cluster analysis was used as pattern recognition technique. Four characteristic water bodies can be identified in the surface water in February (Mecklenburg Bight (MB), Pomeranian Bight (PB), the eastern (EZOS) and western central Baltic Sea (WZOS)). After the spring algae bloom, these patterns disappeared. This may be due to the cleaning of the water column after the bloom by large quantities of settling particulate matter that takes the PAHs with it to the sediment. A seasonal variation of the PAH concentrations was observed with the largest amounts in February followed by November, reflecting the increase of PAH sources during winter.

Carbon budget of sea‐ice algae in spring: Evidence of a significant transfer to zooplankton grazers

The fate of ice‐bottom algae, before and after release from the first‐year sea ice into the water column, was assessed during the period of ice‐algal growth and decline in Resolute Passage (Canadian Arctic). During spring 1992 (from April to June), algae in the bottom ice layer and those suspended and sinking in the upper water column (top 15 m) were sampled approximately every 4 days. Ice‐bottom chlorophyll a reached a maximum concentration of 160 mg m−2 in mid‐May, after which it decreased to lower values. In the water column, chlorophyll a concentrations were low until the period of ice‐algal decline (∼0.1 mg m−3), with most biomass in the <5‐μm fraction. In both the suspended and sinking material, large increases of algal biomass occurred at the beginning of June, following the release of ice‐algae into the water column. The input of ice‐algal derived carbon to the upper water column and the proportions exported through sinking or remaining in suspension were assessed using a carbon budget for the two periods of ice‐algal growth and decline. For each period the output terms closely balanced the input. The carbon budget showed that most of the biomass introduced into the upper water column remained suspended (>65% of total export) and that ice‐algae were ingested by under‐ice grazers after release from the ice. These results stress the importance of ice algae for pelagic consumers during the early stages of ice melt and show that the transfer of ice algae to higher trophic levels extends beyond the period of maximum algal production in the ice bottom.

The diet of two species of Isoperla (Plecoptera: Perlodidae) in relation to season, site, and sympatry

The seasonal change in gut contents of nymphs of Isoperla grammatica and I. difformis from six streams in southern Sweden was analysed. Both species had ingested a variety of benthic prey and vegetable matter, predominantly diatoms. Some seasonality was evident with high percentages of diatoms in spring in I. grammatica, and in autumn in I. difformis. The scope of food was larger in the latter species which contained about equal proportions of vegetable matter, chironomids, mayfly, stonefly, and black fly larvae. In I. grammatica plant matter and chironomids dominated strongly, comprising > 50% of the gut contents on an annual basis, > 90 % in spring. While small nymphs of I. difformis contained a low proportion of animal matter, only gradually increasing with size, the nymphs of I. grammatica were carnivorous from very early instars. Both species switched to a temporarily strong utilization of algae in spring. This differed among sites, and appeared to reflect differences in insolation and thus the availability of algae. There was a significant negative relationship between the mean densities of Isoperla nymphs and the proportion of animal material found in the guts of I. grammatica (R 2 = 0.86). Considering the density of I. grammatica alone, the relationship was weaker (R 2 = 0.56). A positive correlation between predator and prey size was observed. With chironomid prey the size range increased with predator size. With simuliid prey, however, prey size increased with predator size in such a way that it suggests selection rather than just an expanding prey size range. Correlations were stronger and regression coefficients significantly higher for I. grammatica than for I. difformis. We suggest that I. grammatica, which ingests a much wider size range of prey might choose prey of optimal sizes more readily than the more synchronously developing I. difformis. Although the life cycles of the two species are staggered, overlap in size distribution indicates that competition for food could be important in spring. However, observed differences in diet should facilitate coexistence. Gut content differences might in turn be accomplished through microhabitat segregation.

The biogeography of hot spring algae through enrichment cultures

(1978). The biogeography of hot spring algae through enrichment cultures. SIL Communications, 1953-1996: Vol. 21, No. 1, pp. 296-315.

PHYTOPLANKTON DISTRIBUTION AND WATER QUALITY INDICES FOR LAKE MEAD (COLORADO RIVER)1

SUMMARYPhytoplankton samples were collected in Lake Mead 6 times from September 1970 to June 1971 for 8 stations at depths of 0, 3, 5, 10, 20, and 30 m. These samples were processed through a Millipore filter apparatus and 79 planktonic algae were identified. Algal divisions represented were Bacillariophyta, 42 species; Chlorophyta, 18; Cyanophyta, 9; Chrysophyta, 3; Cryptophyta, 3; Pyrrophyta, 2; and Euglenophyta, 2. Blue‐green algae were dominant in late summer and fall; green algae, diatoms, and cryptomonads in winter; and green algae in spring. The early summer flora was best represented by the Chlorophyta, Cryptophyta, and Chrysophyta. Palmer's pollution‐tolerant algae indices and Nygaard's indices were calculated from, phytoplankton data. These indices suggest eutrophic conditions in Lake Mead, especially for Boulder Basin.

EFFECT OF LIGHT INTENSITY ON PHOTOSYNTHESIS BY THERMAL ALGAE ADAPTED TO NATURAL AND REDUCED SUNLIGHT1

Thermal algae in alkaline hot springs of Yellowstone National Park (Wyoming) grow as compact mats in which self‐shading is extensive, as shown by measurement by autoradiography of photosynthetic activity of cells at different levels in the mat. The effect of light intensity on photosynthesis of the algal mats was studied using neutral density filters during incubation with 14CO2. Despite the intense sunlight at the altitude of Yellowstone, light inhibition by full sunlight was observed only occasionally; the rate of photosynthesis fell progressively with decreasing light, although the most efficient use was at 7–14% of full sunlight. Later, the light intensity over portions of the algal mats was reduced to 18% of full sunlight by installing neutral density glass plates, and changes of chlorophyll content, cell number, and response of photosynthesis to light intensity were determined over the next year. Although the chlorophyll content of the algae at the surface of the mat rose quickly, the chlorophyll content of the mat as a whole rose slowly or not at all; the photosynthetic response of the algal mats to full and reduced sunlight also changed slowly or not at all. Although individual algal cells can adapt rapidly to changes in light, the entire population, because of its existence in compact mats, adapts slowly. At the latitude of Yellowstone there is sufficient light throughout the year to enable algal growth to occur even at temperatures near the upper limit at which blue‐green algae can grow; in Iceland, hot spring algae cannot grow during several winter months. Natural ultraviolet radiation neither inhibited nor stimulated photosynthesis.