Limnol. Rev. (2020)Fifty years 20, 4:of 219-227limnology (1969-2019) at Mahoney Lake, , Canada 219 DOI 10.2478/limre-2020-0021

Fifty years of limnology (1969-2019) at Mahoney Lake, British Columbia, Canada

Markus L. Heinrichs1,*, Ian R. Walker2, Ken J. Hall3, Jörg Overmann4, 5, Molly D. O’Beirne6

1 Department of Geography and Earth & Environmental Science, College, 1000 K.L.O. Road, , British Columbia V1Y 4X8, Canada, e-mail: [email protected] (*corresponding author) 2 Department of Biology and Department of Earth, Environmental and Geographic Sciences, University of British Columbia, Okanagan Campus, 3333 University Way, Kelowna, British Columbia V1V 1V7, Canada, e-mail: [email protected] 3 Department of Civil Engineering, Institute for Resources, Environment and Sustainability, University of British Columbia, 2329 West Mall, Vancouver, British Columbia V6T 1Z4, Canada, e-mail: [email protected] 4 Leibniz-Institut DSMZ- German Collection of Microorganisms and Cell Cultures, Inhoffenstraße 7B, 38124 Braunschweig, Germany, e-mail: [email protected] 5 Braunschweig University of Technology, Universitätsplatz 2, 38106, Braunschweig, Germany 6 Department of Geology and Environmental Science, 4107 O’Hara Street, University of Pittsburgh, Pittsburgh, PA 15260, United States of America, e-mail: [email protected]

Abstract: Mahoney Lake is a small, meromictic saline lake in south-central British Columbia noted for its unique layer of purple sulfur bacteria. First examined in 1969, this lake has undergone physical, chemical, biological, and pre-historical research to generate an understanding of how the lake and its biota function have developed through time. Advances in understanding the sulfur transformations and bacterial nutrient cycling over the last fifty years have been prolific, resulting in the description of several new taxa. Mahoney Lake is exceptional in its limnological characteristics and is an ideal site for training future limnologists. Key words: purple sulphur bacteria, meromictic, redox

Introduction is acutely sensitive to water balance. The shoreline length is estimated at less than three kilometres (BC Mahoney Lake, British Columbia, Canada is a Parks 2020). It is currently bounded by the twenty closed-basin meromictic lake with unique stratifica- nine and a half hectare Mahoney Lake Ecological tion patterns and physical chemistry that are cur- Reserve on the southern side, established by the rently reflected as euxinic (i.e., anoxic and sulfidic) province of British Columbia in 1972, and the 3764 conditions. Its biota are similarly unique and di- hectare White Lake Grasslands Protected Area, es- verse, having adapted to the extreme environ- tablished in 2001, on the northern side. The lake is ments that developed in the Holocene. As such, it located in the Ponderosa Pine biogeoclimatic zone, has received scientific attention for over fifty years. with a mean annual temperature of 10.1°C and 345 Mahoney Lake is an approximately twenty mm of precipitation (1981-2010 Canadian Climate hectare lake situated at ~470 metres above sea lev- Normals from Oliver, BC). el, ten kilometres south of , British Mahoney Lake was officially named as such Columbia, with a catchment of about 385 ha in area. in 1936, after John Mahoney who pre-empted Lot The lake has a depth of eighteen metres, however, 521 in February 1908; prior to this it was identi- the surface elevation fluctuates by several metres in fied as Alkali Lake on some 1918 land surveyor’s any decade as there are no outlet streams and in- field notes (BC Geographical Names 2020). The let streams are ephemeral. As such, Mahoney Lake Syilx peoples, the local First Nations, have for mil- lennia interacted with this and other special lakes 220 Markus L. Heinrichs, Ian R. Walker, Ken J. Hall, Jörg Overmann, Molly D. O’Beirne in the area (e.g. Spotted Lake) and likely had given portant observations and speculations that directed Mahoney Lake a name in the Nsyilxcən language subsequent research, for example, that the purple based upon the unique character of this lake. sulfur bacterial plate may move with seasonal light Here we present a three-part, comprehen- penetration, that the copepod community feeds sive summary of the research conducted over the upon the bacteria, and that warm monimolimnion last fifty years. We first describe research examin- temperatures may allow year-round reproduction ing the unique physical and chemical characteristics within the zooplankter community. Lastly, they of this lake. Second, we outline the paleolimno- stated that Mahoney Lake is probably unsuitable for logical studies that highlight changes the lake has trout due to its salinity and low oxygen concentra- undergone since deglaciation in the region. Last, tions – for this we may be grateful that there was we highlight research in carbon and sulfur transfor- no artificial mixis technology installed in Mahoney mations and characterization of the sulfur bacterial Lake, setting the stage for decades of limnological community and suggest possible future avenues of research into this fascinating lake. research. Fourteen years later, Northcote and Hall (1983) compared the adjacent Green and Mahoney Mahoney Lake Lakes (separated by less than one kilometre), both of which are considered saline. They proposed that the differences in conductivity (Green Lake = 3520 A unique aquatic ecosystem μS cm–1 and Mahoney Lake = 55,000 μS cm–1) and mineral composition between lakes is due to the A Zeitgeist of the postwar period was to “im- underlying bedrock – Greenlake astride the Skaha prove” the sport fishery in British Columbia, specifi- formation that is low in alkali materials, Mahoney cally for brook and rainbow trout (Ashley and Nor- bounded by the Kitley Lake and Marama forma- din 1999). In the late 1960s, Halsey was tasked to tions (see Church 1973 for additional discussion on investigate the overwintering capacity of a variety these rock formations), both high in alkali miner- of inland lakes for game fish (Halsey 1968). An aera- als. Differences in bedrock contributions were later tion system was eventually installed at Yellow Lake confirmed (Michel et al. 2002), with a conductiv- in 1969 to facilitate the salmonid fishery (Halsey and ity value of 135,000 μS cm–1 in October, 1981 at MacDonald 1971). This mandate was likely the rea- Mahoney Lake, though values of 5800 and 8500 son for examining Mahoney Lake, as Northcote and μS cm–1 from May and September, 1983 were ob- Halsey compared four similarly sized lakes in south- served. Differences in ion concentrations were also ern British Columbia, three near the community of observed between Mahoney and Green Lakes (see (White, Yellow, and Mahoney Lakes) and Table 1). one (Lyons Lake) near Kamloops (Northcote and Although the salinity of Mahoney Lake is Halsey 1969). They provided physicochemical data comparable to that of marine environments, and for the lakes and their watersheds, noting that the the lake is not alkaline, it is rich in magnesium and thermal, dissolved oxygen, conductivity, and fauna sulfate ions which seem to be the cause of the ab- profiles indicated that strong meromixis occurred sence of fish and the low diversity of zooplankton. in Mahoney and Lyons Lakes. Furthermore, using Northcote and Hall (1983) additionally proposed an echo sounder, they discovered two layers within that meromixis is maintained in Mahoney Lake not the water column of Mahoney Lake, the lower one occurring at the chemocline which was dominated by purple sulfur bacteria at the time identified as Table 1. Ion concentrations (in mg dm–3) of Mahoney and Green Thiocapsa sp. with a jellylike consistency because of Lakes, British Columbia an extremely high biomass density, and an upper Mahoney Lake Green Lake Ion layer that may have been caused by phytoplank- (Oct. 1981) (Sept. 1983) ton, but that may have been ephemeral in nature. Na+ 4900 228 Aside from noting the presence of the distinct lay- K+ 730 37 er of bacteria (later photographed to be distinctly SO 2– 19440 701 stratified (Overmann 2001), they made several im- 4 Fifty years of limnology (1969-2019) at Mahoney Lake, British Columbia, Canada 221 due to differences in salinity, but rather local topo- by Hamilton et al. (2014) as Thiohalocapsa, thus it graphical differences, suggesting that the surround- is referred to here by the name Thiohalocapsa sp. ing hills protect Mahoney Lake from prevailing strain ML1) and lesser populations of Thiocapsa ro- winds whereas Green Lake is more exposed and seopersicina, Rhodobacter capsulatus, Chloroherpe- lies parallel the main axis of the Okanagan Valley. ton thalassium, and Prosthecochloris aestuarii. They However, one cannot help but feel they were ulti- determined that the concentration of bacteriochlo- mately more interested in examining the biological rophyll a was up to 20,900 μg dm–3, the highest implications of the unique stratification of Mahoney value observed in any natural body of water to date Lake. Four distinct oxygen zones were confirmed, (nine times higher than the next reported value), the surface high O2 zone (likely originating from with primary productivity amounting to fifteen mil- melting snow), a low O2 zone at two metres depth, ligrams of carbon per square metre per hour with- a moderately oxygenated zone at six metres depth, in the bacterial plate. In subsequent years, record and the anoxic monimolimnion below eight me- concentrations of 27,500 μg bacteriochlorophyll-a tres depth. They also observe that productivity is per litre were detected (Overmann et al. 1994). dominated by bacterial activity, unlike Green Lake, Overmann et al. (1991) also investigated the flux where lake productivity was dominated by phyto- of sulfide within the water column, recognizing the plankton as in most other lakes. Finally, they associ- redox roles of a variety of bacteria within the layer ate two distinct zooplankton zones associated with itself, including purple non-sulfur bacteria which re- the surface and six metre oxygenated layers. cycled organic carbon. They further suggested that The unusual, four-layer stratification of Ma- the meromictic structure of the lake reduces bacte- honey Lake begged further investigation, both from rial losses to sedimentation and decay, allowing the a mixis perspective, but also with implications in higher concentrations of bacteria to persist. Over- productivity and nutrient cycling. Because of the mann also notes that the growth of Thiohalocapsa unusual lake water chemistry and temperatures, sp. strain ML1 (formerly A. purpureus) is slow, since Hall and Northcote (1986) developed a calibration only 10 percent of the cells receive sufficient light method for dissolved solid estimation to be used at energy for photosynthetic growth due to the ex- Mahoney Lake. Three publications stemmed from treme self-shading within the bacterial layer (Over- this period of investigation: a vernal (spring season) man 1997). examination of microstratification (Northcote and Subsequently, the research focus at Mahoney Hall 1990), an autumnal (fall season) examination Lake diverged along two different avenues of in- of mixing of the water layers (Ward et al. 1990), vestigation, the first following the purple sulfur bac- and an investigation into the productivity and de- teria, and the second investigating the pre-history composition processes occurring in spring and fall or development (paleolimnology) of the lake itself. (Hall and Northcote 1990). The results suggest that indeed spring melting of snow and ice was the ori- Mahoney Lake: Paleolimnology gin of the secondary (upper, ephemeral) chemo- cline in the lake and that wind is not a significant Overmann et al. (1993) examined fossil pig- contributing factor to destratification in autumn. ments from a sediment core taken from Mahoney However the most unexpected result was that the Lake in 1985, which was subsequently stored at phototrophic layer of purple sulfur bacteria was re- the University of British Columbia under the care sponsible for up to 66 percent of the total primary of Ken Hall. Pigments from aquatic algae, plants, productivity in Mahoney Lake. Phytoplankton pro- and bacteria are long recognized to be resistant to ductivity in the mixolimnion was considered simi- decomposition or alteration in sediment and thus lar to other “normal” (i.e., oligotrophic) lakes, likely are an ideal archival proxy for productivity (Leavitt limited by phosphorus. and Hodgson 2001). Using high-performance liq- Overmann et al. (1991) examined the pur- uid chromatography, Overmann et al. were able ple sulfur bacteria layer in Mahoney Lake, reclas- to match the then currently 97 percent dominating sp. strain ML1’s okenone pigment to sifying the dominant species as Amoebobacter pur- Thiohalocapsa the presence of okenone pigments dating back to pureus (later reclassified as Lamprocystis purpurea comb. nov by Imhoff (2001) and further confirmed 11,000 years before present, though peaking in the 222 Markus L. Heinrichs, Ian R. Walker, Ken J. Hall, Jörg Overmann, Molly D. O’Beirne early Holocene once sediments changed from in- er or wetter periods, the lake would favour more organic to organic material. Deposition of Mazama freshwater conditions. The proxies both indicate ash was noted as significant in this lake, with nearly fresh water conditions occurred prior to 9800 yr BP, one metre of tephra preserved in the sediments. with a subsequent shift to saline conditions (about This contrasts with only eight centimetres of Maza- thirty grams per litre) thereafter. This dramatic dif- ma tephra at nearby Lake of the Woods, British Co- ference was considered to reflect the loss of glacial lumbia (Heinrichs et al. 2004), which is more typical water input into the system (Heinrichs 1995). Re- of most Mazama tephra layers in lakes within the finements to the models used for calculating paleo- region (Buckland et al. 2020). Okenone pigments salinities support the large shift from freshwater to decreased significantly during tephra deposition in saline conditions early in the Holocene (Heinrichs Mahoney Lake, but reached their highest concen- et al. 2001), and weakly support the idea of cooling trations during the last few thousand years. Surpris- during the last few millennia (Heinrichs and Walker ingly, no carotenoid pigments from purple non-sul- 2006). The impacts of regional climate fluctuations fur bacteria nor any from green sulfur bacteria were have generally been observed in other local lakes found in the fossil record, suggesting the dominant using a variety of proxies (Walker and Pellatt 2008). purple sulfur bacteria community was an early and In a ground-breaking, environmental DNA long-standing community at Mahoney Lake. study (Coolen and Overmann 1998), genetic ma- Lowe et al. (1997) used the same sediment terial from purple sulfur bacteria was sequenced core to examine whether or not the lake has always for the first time from lake sediment (Parducci et been meromictic, applying the rationale that low al. 2017), specifically, from the same sediment core lake levels would allow mixis by wind, whereas used in the preceding studies. Coolen and Over- high lake levels would maintain a separate, non- mann (1998) used the 16S rRNA gene fragments mixing layer. By examining the core for the pres- from Thiohalocapsa sp. strain ML1 (formerly A. pur- ence of varves, they determined that meromictic pureus) from the chemocline and compared them conditions were established by about 9000 yr BP, against samples from the sediment as far back as shortly after the sediment changed from inorganic 9100 years old, confirming that they were 99.2 mud to organic gyttja at 10,000 yr BP. Meromixis percent identical. Thus they confirm that it was this was intermittent throughout the Holocene, inter- bacteria species that was present from early on in rupted by periods of water evaporation and ensuing the lake’s history, persisting through both mero- deposition of marl, such that they were able to in- mictic and holomictic stages. fer a record of “effective precipitation” for Mahoney The last study to use this sediment core was Lake and compare that record with other regional that by Hall and Northcote (2000), tracking geo- paleoclimate records. Curiously, the “effective pre- chemical changes. The total phosphorus curve cipitation” (precipitation over and above what is showed a decrease following deglaciation, sug- lost by evaporation) record does not accurately fol- gesting that availability of this nutrient was greater low either the glacial retreat/advance patterns or from pulverized glacial flour, as no new sources forest development patterns from other paleoenvi- were available thereafter. The calcium and mag- ronmental studies. Lowe et al. (1997) note a nearly nesium curves were suggested to be correlated four metre decrease in lake level between 1982 and with evaporative conditions, such that peaks in the 1995, together suggesting that this lake is much early- (approximately 10,000-7000 yr BP) and mid- more sensitive to climatic changes than perhaps (6000-4000 yr BP) Holocene were relatively dry pe- other lakes, and that the dominating Pacific weather riods. This generally supports the pattern identified system (wet vs dry winter) has a greater influence by Lowe et al. (1997) with lake levels. Maximum on lake level than general climatic trends. productivity in the lake occurred after 5000 yr BP, Heinrichs et al. (1997) also used the same with peaks in total nitrogen and organic matter in sediment core to reconstruct paleosalinity examin- the sediment. A relatively recent decline in produc- ing sub-fossil chironomid and diatom remains. Us- tivity (i.e. during the last 1000 years) may be due to ing the rationale that during periods of low effective unfavourable conditions for the sulfur bacteria. moisture, the water balance of this closed-basin lake It has to be kept in mind, however, that pho- would favour high salinity, whereas during cool- tosynthetic production of anoxygenic phototrophic Fifty years of limnology (1969-2019) at Mahoney Lake, British Columbia, Canada 223 purple sulfur bacteria depends on the presence of umn samples and a composite ca. four metre long sulfide, which in Mahoney Lake is formed by sul- sediment core were recently acquired. Bulk meas- fur- and sulfate-reducing bacteria as in other non- urements of inorganic sulfur, organic sulfur, carbon geothermal lakes. Ultimately, anoxygenic photo- and nitrogen abundance and isotope compositions, synthesis is therefore fueled indirectly by organic as well as redox trace metal measurements on sam- carbon that has been produced by oxygenic pho- ples from the sediment core have been completed. tosynthesis within or outside the ecosystem (Over- Sulfur isotopes of individual organic sulfur com- mann et al. 1993). In the case of Mahoney Lake, pounds were also measured. Similar bulk analyses the high ratio of primary production of purple sul- were also performed on water column samples of fur bacteria to that of phytoplankton most likely is dissolved and particulate organic matter. Data from due to a substantial input of allochthonous organic these analyses have yet to be published, but have matter. The input of purple sulfur bacterial biomark- revealed insights into the complex interplay of the ers into bottom sediments is therefore determined coupled biogeochemical cycles of carbon, sulfur, by a complex interplay of light availability, alloch- and iron, with important implications for interpre- thonous organic carbon concentrations, and sulfide tation of the geologic record and reconstruction of availability/production in the chemocline, as well as (paleo)environmental conditions. the death and sedimentation rates of the purple sul- In addition to their sulfur work, the UP and fur bacterial cells. IUPUI researchers also analyzed molecular bio- Paleolimnological research was renewed by marker proxies in water column particulate organic researchers from the University of Pittsburgh (UP) matter as well as in the surface sediments. Specifi- and Indiana University – Purdue University of Indi- cally, they catalogued the structural diversity and anapolis (IUPUI), who returned to Mahoney Lake abundance of bacteriohopanepolyols (BHPs) – a in 2015 in order to study its sulfur cycle, paying promising class of hopanoid biomarkers used for particular attention to organic sulfur (i.e., sulfur in- tracing microbial activity and reconstructing (paleo) corporated into organic matter during diagenesis environmental conditions. They found distinct dif- – aka sulfurization). The relative abundances of inor- ferences among the BHP compositions and oxic, ganic, organic, and elemental sulfur can be used to suboxic, and euxinic water column conditions. The reconstruct (paleo)environmental redox conditions. BHP compositions within the water column were Relative to the long-standing proxies and interpre- also found to be distinctly different from those with- tive framework developed for pyrite formation and in the surface sediments. The results mentioned are deposition, studies focused on the organic sulfur currently in preparation for publication and have record are limited. The major obstacles associated great potential to provide new and complementary with the interpretation of the organic sulfur record information related to environmental and microbial are related to unknowns surrounding the timing and dynamics throughout Earth’s evolution and espe- pathway(s) of formation of individual organic sulfur cially during times of extreme environmental transi- compounds and the extent to which organic sulfur tions (e.g., oceanic anoxic events). isotope compositions, both bulk and molecular, re- cord primary depositional conditions or are diage- Purple sulfur bacteria and more netically overprinted. The coupled cycling of sulfide oxidation and sulfate reduction were explored from With the recognition that the sulfur bacteria of the water column and a sediment core obtained in Mahoney Lake were not only highly abundant but also the key drivers of most geochemical process- 2006, demonstrating that pyrite (FeS2) deposited in the lake was generated in the water column (Gil- es, additional characterization of the sulfur transfor- hooly et al. 2016). Gilhooly III et al. (2016) con- mations and bacterial communities commenced. firmed that this sulfur derives from minerals of the What may have begun as just an anomalous odd- Kitley formation. ity worth a quick second look, the sulfur bacteria Because Mahoney Lake represents an end- story has gone on to capture the imagination of member of extreme, environmental euxinia, it pro- astrobiologists. Upon returning to Mahoney Lake, vides an excellent location for detailed studies of Overmann et al. found two new strains (06511 and organic matter sulfurization. Therefore, water col- SSP1) of a sulfur bacteria from the littoral sediments, 224 Markus L. Heinrichs, Ian R. Walker, Ken J. Hall, Jörg Overmann, Molly D. O’Beirne newly described as Thiorhodovibria winogradskyi teria in the layer or plate at the chemocline. Yurkova gen. nov. and sp. nov (Overman et al. 1992)). Of et al. (2002) documented thirty-one strains of obli- particular interest is the fact that these bacteria are gate aerobic phototrophic bacteria, along with two exposed to and thus naturally tolerant of sunlight new purple non-sulfur bacteria, from the mixolim- and oxygen, as well as highly saline conditions dur- nion using classical microbial methodology. From ing periods of evaporation. these same samples, Rathgeber et al. (2005) were The dominant sulfur bacteria in the water col- able to isolate eight strains of Gram-negative pink- umn, Thiohalocapsa sp. strain ML1 (formerly A. pur- purple bacteria within the Alphaproteobacteria. pureus), was documented to form aggregates that They proposed a new genus of bacteria with a spe- remain buoyant due to cell surface hydrophobicity cies classified as Roseicyclus mahoneyensis gen. nov., when sulfide was depleted. With normal concentra- sp. nov. Beneath the chemocline, in the deep, dark, tions of sulfide, gas vesicles allow the bacteria to re- saline hypolimnion, a diverse community of bacte- main buoyant. These paired mechanisms were pro- ria also occurs (Klepac-Ceraj et al. 2012). In sulfate- posed to maintain the specific depth of the bacterial rich ecosystems such as Mahoney Lake, sulfur com- community layer (Overmann and Pfennig 1992). pounds are the main inorganic compounds used by With fluctuating amounts of sulfide in the water the anaerobic heterotrophic bacteria degrading or- column during the year, the populations of Thio- ganic carbon in anoxic layers. Sulfate-reducing and halocapsa sp. strain ML1 were observed to adapt sulfur-reducing bacteria were indeed detected and accordingly (Overmann et al. 1994). Minimum late highly active within the chemocline population of summer sulfide concentrations trigger the die-off in Thiohalocapsa sp. strain ML1 (formerly A. purpureus) Thiohalocapsa sp. strain ML1 (Overmann, Beatty, and below (Overmann, Beatty, Krouse et al. 1996). Krouse et al. 1996). Excess bacterial cells then en- Variation in abundance between the Epsilonproteo- ter the mixolimnion during autumn. Wind-driven bacteria and Deltaproteobacteria at seven and eight erosion of the surface of the chemocline population metres depth, respectively, is likely due to different eventually deposits visible, bright purple masses metabolic processing of sulfur between the bacteri- on the littoral sediment (Overmann, Beatty and Hall al types, with sulfate and sulfur reduction occurring 1996). In yet another bizarre twist, the excess Thio- at lower depths by the Deltaproteobacteria. These halocapsa sp. strain ML1 cells that were not able bacteria are similar to those residing near methane to survive and ended up in the oxygen-containing seeps in deep ocean environments or hypersaline mixolimnion acted as a significant phosphorus sediments. source for aerobic, heterotrophic bacteria which are otherwise limited by this nutrient throughout the New directions rest of the year. Bacteria are not the only (interesting) biologi- There has been progress in technologies/ cal resident in the water column. With this abundant methodologies that has meant Mahoney Lake is primary producing bacterioplankton community, it once again a site for novel research. Bovee (2014) makes ecological sense that there would be a sec- and Bovee and Pearson (2014) examined individual ondary trophic network. Heterotrophic flagellates, lipid biomarkers and carbon isotopes of the basinal sediment, comparing it to both water column and ciliates, rotifers, and calanoid copepods (e.g. Di- littoral sediments. They found that the littoral and aptomus connexus) have been observed (Overmann, Hall, Northcote, Ebenhöh et al. 1999). Because basinal sediments were similar, but that the materi- of the salinity of the water itself, fish are not able als were not generated from the bacterial commu- to survive, which would otherwise feed upon the nity within the water column. Instead, it was the copepod community. Whereas most lakes would shoreline microbial community and allochthonous have copepods feeding upon a ‘lower’ trophic her- materials that generated the deep basin sediments, bivore, here they also feed directly upon the purple moving laterally, downslope through the density sulfur bacteria (Overman, Hall, Northcote and Be- gradient prior to deposition. The bacterial commu- atty 1999). nity within the water column appears to be recycled The bacterial community of Mahoney Lake is within the water column itself as predicted by earli- not limited to only a few species of purple sulfur bac- er modelling of the carbon cycle (Overmann 1997). Fifty years of limnology (1969-2019) at Mahoney Lake, British Columbia, Canada 225

Hamilton et al. (2014) used metagenomic and taphonomy, as well as the next generation of sequencing of the bacterial plate to elucidate the research scientists. From a rather humble start in various bacterial participants in the sulfur cycle measuring oxygen, conductivity and temperature (oxidation and reduction). The main purple sulfur values, the emerging story of this lake reflects not bacteria Thiohalocapsa sp. strain ML1 (formerly A. only our limited understanding of aquatic process- purpureaus, later L. purpurea) was the dominant pri- es, it allows us to trip over our lack of imagination mary producer, however, a host of oxidizing and in recognizing how unique one lake can be. Further, reducing organisms were identified from genomic it emphasizes the value in intense, in-depth studies markers. Again, using genetic analyses, Hamilton of single sites vs. a one-and-done analysis of mul- et al. (2016) found little evidence for organisms tiple sites. capable of oxidation below the chemocline, rather they found numerous populations that were re- Acknowledgements ducers of sulfur. They identified a new taxonomic lineage in the Fibrobacteres+Chlorobi+Bacteroidet The authors would like to recognize the pio- es superphylum from samples below the bacterial neering investigation of Mahoney Lake by Dr. Tom plate / chemocline, proposing the name Candidatus Northcote, a frequent visitor to that special place. Aegiribacteria MLS_C, after Aegir, the Norse God He was responsible for inspiring much of the work of the Sea. summarized here and his insights into the aquatic Mahoney Lake represents a unique ecosys- world will be greatly missed. The authors would tem that is sufficiently simple to serve as a model also like to thank BC Parks for archiving 50 years of system for elucidating the processes that occurred field notes. in a stratified oxic-anoxic system of the geologi- cal past. Being distinct, it has gained the interest References of a number of special interest groups. NASA has identified the lake important from an astrobiological Ashley K., Nordin R., 1999, Lake aeration in British Co- perspective (Gronstahl 2016). The unusually harsh lumbia: Applications and experiences, [in:]. Murphy conditions here may be an analogue for environ- T., Munawar M. (eds), Aquatic restoration in Canada, ments on exoplanets. Backhuys Publishers, Leiden: 87–108. [BC Geographical Names], British Columbia Geographical Future studies of Mahoney Lake will improve Names, 2020, Mahoney Lake [Electronic resource]. our understanding and the interpretation of sedi- Retrieved from http://apps.gov.bc.ca/pub/bcgnws/ mentary deposits of the geological record even fur- names/3956.html ther. It has also been proposed that Mahoney Lake [BC Parks] British Columbia Parks, 2020, Mahoney Lake be considered an ideal teaching site for future lim- Ecological Reserve. Detailed Ecological Reserve De- nologists due to its unique characteristics and long scription. Mahoney Lake ER #130: 1–3 [Electronic re- history of research (Northcote and Hall 2008). Many source]. Retrieved from http://bcparks.ca/eco_rese- rve/mahoney_er/Mahoney%20Lake%20ER%20130. interesting research questions from Mahoney Lake pdf?v=1598526357413 can yet be asked, e.g.: is the sulfur trophic web con- Buckland H.M., Cashman K.V., Engwell S.L., Rust A.C., sistent through the lake’s history? Have geological 2020, Sources of uncertainty in the Mazama isopachs strata similar to the Kiteley Lake formation led to and the implications for interpreting distal tephra de- similar sulfur bacterial communities elsewhere? posits from large magnitude eruptions, Bull. Volca- How will future climate and environmental changes nol. 82, #23: 1–17. affect Mahoney Lake? As an Ecological Reserve, it Bovee R., 2014, Lipidomic and genomic investigation of should be noted that a permit to conduct future re- Mahoney Lake, B.C. [Dissertation], Harvard Universi- ty, Cambridge, 135 pp. search answering these and other questions is re- Bovee R.J., Pearson A., 2014, Strong influence of the lit- quired from BC Parks. toral zone on sedimentary lipid biomarkers in a mero- mictic lake, Geobiology 12(6): 529–541. Conclusion Church B.N., 1973, Geology of the White Lake basin, B.C. Dept. of Mines and Petroleum Resources Bull. Mahoney Lake continues to inspire new lines 61: 1–120. of inquiry into, for example biology, limnology, Coolen M.J.L., Overmann J., 1998, Analysis of subfossil 226 Markus L. Heinrichs, Ian R. Walker, Ken J. Hall, Jörg Overmann, Molly D. O’Beirne

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