Algal remains in Minnesota lake types: a comparison of modern and late-glacial distributions (original) (raw)
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Preliminary Investigation of the Algal Flora in the Sediments of Lake Erie
Journal of Great Lakes Research, 1981
The algae in a 45-cm-Iong sediment core taken in the eastern basin of Lake Erie were examined to determine the extent and applicability of that flora in reflecting the history of the lake. Asterionella formosa, Melosira islandica, M. italica, Stephanodiscus niagarae, and Tabellaria fenestrata were the most abundant diatoms encountered. Quantitative diatom profiles reported as cells/ cm 3 sediment and relative abundance profiles each provide a contrasting history of postsettlement Lake Erie. In light ofthe known history ofthe lake, the relativefrequency profiles appear to be most applicable. The C/ P index of trophic status and diatom diversity support those profiles. The occurrence of non-diatom algae in the sediments was inadequate for detailed analyses; however, occurrence did correspond to the trophic history determined by the diatoms. Botryococcus braunii, Cosmarium formosulum, Pediastrum boryanum, and Staurastrum gracile were most commonly encountered.
Freshwater Science, 2014
Lake Tovel is an oligotrophic, meromictic, mountain lake of the Dolomites that undergoes marked seasonal water-level fluctuations (WLFs). We used neo-and paleolimnological data collected since 1999 to test the utility of algal and cyanobacterial pigments and diatom and chironomid biodiversity as proxies for WLF and to highlight the contribution of benthic algae to the sediment record. We found that detailed knowledge of presentday spatiotemporal patterns of WLF is essential for a complete and correct interpretation of paleolimnological data. Scytonemin, a cyanobacteria-specific photoprotective pigment, was produced by epilithic cyanobacteria in the depth zone affected by WLF and should be considered a proxy for the extent of WLF. The phytobenthos was as important as phytoplankton as a source of sedimentary pigments. We used information gained on the detailed distribution of diatoms at different depths and on different substrata in the 2 basins to show the probable location in the lake from which taxa in sediment cores originated to aid in interpretation of the sediment archive (including identification of periods of active hydrology). We sampled present-day chironomids in springs and streams feeding the lake and along a depth transect in the main basin. The taxa found were all rheophilic, crenophilous, or typical of the littoral zone of oligotrophic lakes. We interpreted sections of the cores containing large numbers of Orthocladiinae and Diamesinae head capsules as indicative of periods of active hydrology (including sudden and marked WLF) because the littoral taxa found in the cores must have been derived from the littoral zone by sediment focusing or slumps. Thus, we identified useful proxies of WLF in mountain, carbonate lakes.
The use of sedimentary algal pigments to infer historic algal communities in Lake Apopka, Florida
Journal of Paleolimnology, 2005
The primary producer community of Lake Apopka, a large (125 km 2 ), shallow (mean depth, 1.7 m), polymictic Florida lake, shifted from macrophyte dominance to phytoplankton dominance in the 1940s. Today, frequent wind resuspension of highly organic, unconsolidated sediments supports a meroplanktonic community that is predominantly diatoms, but during calm periods the algal community is dominated by planktonic cyanobacteria. Sedimentary algal pigments (chlorophyll derivatives and carotenoids) and chemical proxies for nutrient enrichment (polyphosphate, total phosphorus and biogenic silica) in three sediment cores were used to investigate historic changes in primary producers. Sediments were separated into three stratigraphic zones using multivariate statistical techniques. Stratigraphic zonation was established in each core although sediment deposition at one site was insufficient to adequately resolve temporal changes. These results show the importance of selecting suitable sites for paleolimnological studies. The oldest zone represents macrophyte-derived sediments, and the two overlying zones represent phytoplankton-derived sediments deposited since the 1940s. Algal pigments in the most recent sediment zone show little degradation, which might be due to the presence of viable meroplankton in the sediment. After the initial primary producer shift from macrophytes to phytoplankton, the lake experienced a short period of cyanobacterial dominance followed by a period of benthic diatom abundance before being replaced by the present algal community consisting of cyanobacteria and meroplanktonic diatoms. Chlorophyll derivatives and carotenoids were highly correlated with total phosphorus. Historic trends inferred from the data include algal and cyanobacterial productivity that increased with increased phosphorus loading. The study demonstrates that valid paleolimnological proxies for historic eutrophication are available in loosely consolidated sediments of shallow, subtropical lakes.
Peer-reviewed literature and published reports were used to summarize knowledge of benthic algal assemblage composition and ecology in Lake Erie, and causes and consequences of temporal variation in algal abundance. Macroalgal assemblages in rocky littoral and so substrate habitats have been reasonably well described and studied, as has the epiphyte/ metaphyte assemblage associated with rocky littoral macroalgae. In contrast, little information exists for non-epiphytic microalgae in littoral habitat. During the period when algal records were reported (1865-2006), the rocky littoral macroalgal assemblage was o en dominated by the chlorophyte genera Cladophora and Ulothrix and the rhodophyte Bangia, whereas the charophytes Chara and Nitella were most abundant in littoral so substrate. In addition to substrate e ects, assemblage composition varied as a function of depth, temperature, light levels, and nutrient concentrations. Under certain conditions, macroalgal taxa appeared to outcompete and exclude other taxa from littoral habitat. However, these organisms have also facilitated increased algal diversity by supporting epiphytes/metaphytes. In Lake Erie, signi cant temporal change in benthic algal abundance has been associated with: 1) eutrophication (prior to 1972), 2) oligotrophication following the Great Lakes Water Quality Agreement (1972-1985), and 3) invasion by Dreissena mussels (1986-2006). Increasingly eutrophic conditions were re ected by high abundance and frequent shoreline fouling by Cladophora, declining charophyte (such as Chara, Nitella) abundance, and invasion of rocky littoral habitat by euryhaline Bangia. Subsequent indicators of oligotrophication included declining Cladophora abundance, and increased diatom abundance in deepwater habitat. E ects of lter-feeding Dreissena (such as increased water clarity, phosphorus excretion) were likely causes for Cladophora resurgence in the 1990s, and likely contributed to return of Chara and Nitella to formerly occupied habitat. Algal assemblages clearly re ect environmental conditions in aquatic ecosystems. To accurately assess present and future conditions in Lake Erie, continued study of all benthic assemblages is recommended, with greater attention directed toward microalgae in littoral habitat than has occurred in the past.
Comparison of diatoms, fossil pigments and historical records as measures of lake eutrophication
Freshwater Biology, 1997
1. Analysis of fossil diatoms and pigments was used to examine the effects of landmanagement practises on the trophic status of Williams Lake, a eutrophic lake in central British Columbia, Canada. Published weighted-average (WA) models were used to infer changes in total phosphorus concentration (TP) during the past 200 years. 2. Diatom-inferred TP (DI-TP) was compared to 20 years of direct chemical TP measurements to determine the accuracy of diatom-TP models in inferring mean summer TP in Williams Lake. Plant pigments were measured using high performance liquid chromatography (HPLC) to quantify historical changes in gross algal community composition and abundance and to evaluate further diatom-TP inferences. 3. Palaeolimnological analyses showed that Williams Lake has been productive throughout the last 200 years. Diatoms characteristic of alkaline, eutrophic conditions were continuously present c. 1765-1990 AD. Carotenoids from filamentous cyanobacteria (myxoxanthophyll, aphanizophyll) were regularly present in Williams Lake sediments, although cryptophytes (alloxanthin), diatoms (diatoxanthin), chlorophytes (luteinzeaxanthin, b-phorbins), and siliceous algae (diatoms, chrysophytes) or dinoflagellates (fucoxanthin) were also important components of past algal communities. Terrestrial disturbance (railway and road constructions, cattle ranching) increased lake production, but resulted in relatively little permanent environmental change. 4. Comparison of DI-TP with measured TP showed that inferences from simple WA models were similar to average summer TP (39.1 vs. 35.2 µg TP l -1 ). Inferences resulting from data manipulations that down-weighted eutrophic lakes (outlier elimination, bootstrapping) or diatom species (square-root transformation, tolerance-weighting) were weakly and negatively correlated with measured TP, introduced bias into inference models, or underestimated measured TP. These patterns suggest that, when using diatom-TP models developed from sparsely populated regions, accurate palaeoecological inferences for TP in eutrophic lakes should avoid data manipulations which down-weight the most productive sites and taxa. 5. Comparison of DI-TP and fossil-inferred algal abundance during the past 200 years suggested that changes in nutrient inputs accounted for relatively little variation in past algal abundance. Although past changes in total algal biomass (as β-carotene) and DI-TP © 1997 Blackwell Science Ltd 401 402 R. I. Hall et al.
Quaternary Research, 1988
A postglacial core was taken from Lily Lake, a soft-water lake, located on carbonate-poor till in eastern Minnesota. Pollen analysis allowed the reconstruction of watershed vegetation change. Diatom assemblages from the core were compared with 255 surface sediment assemblages from Minnesota, Maine, Labrador, and the Canadian arctic. Late-glacial assemblages were similar to Canadian arctic lakes. During the mid-postglacial period of warmer and drier climate, fossil diatom assemblages at Lily Lake were similar to those in the surface sediment of modem eutrophic hardwater lakes in Central Minnesota. The shift to hardwater diatom assemblages coincided with a shift to ptairie species in fossil pollen assemblages at about 8000 yr B.P. At about 3400 year B.P. the fossil diatom assemblage that characterized presettlement times was established. 6 1988 university of Washington.
PeerJ
Meromictic Crawford Lake, located in SW Ontario, Canada is characterized by varved sediments, making it suitable for high-resolution paleoecological studies. Freeze cores, the only coring method available that reliably preserves the fragile laminations representative of seasonal deposition in the lake, were used to document siliceous diatom and chrysophyte community structure at an annual resolution from 1930–1990CE. Stratigraphically constrained cluster analysis identified major assemblage changes that are believed to have been caused by local, regional and possibly global anthropogenic impacts. The assemblage changes within the siliceous algae are attributed to regional weather and increased industrial emissions and related effects of acid deposition on the lake’s catchment associated with the Great Acceleration –the massive economic, industrial, and demographic expansion beginning in the mid-20th century. Observed increases in spheroidal carbonaceous particles (SCPs) in varved la...
Sediment cores were collected from Upper Klamath Lake in October, 1998 and analyzed for 210 Pb, 14 C, 15 N, N, P, C, Ti, Al, diatoms, Pediastrum, and cyanobacterial akinetes. These results were used to reconstruct changes in water quality in Upper Klamath Lake over the last 150 years. The results showed that there was substantial mixing of the upper 10 cm of sediment, representing the previous 20 to 30 years. However, below that, 210 Pb activity declined monotonically, allowing reasonable dating for the period from about 1850 to 1970. The sediment accumulation rates (SAR) showed a substantial increase in the 20th century. The increase in SAR corresponded with increases in erosional input from the watershed as represented by the increases in sediment concentrations of Ti and Al. The upper 20 cm of sediment, representing the last 150 years, also showed increases in C, N, P, and 15 N. The increases in nutrient concentrations may be affected to various degrees by diagenetic reactions within the sediments, although the changes in concentrations also were marked by changes in the N:P ratio and in a qualitative change in the source of N as reflected in increasing δ 15 N. The diatoms showed modest changes in the 20th century, with increases in Asterionella formosa, Stephanodiscus hantzschii, and S. parvus. Pediastrum, a green alga, was well-preserved in the sediments and exhibited a sharp decline in relative abundance in the upper sediments. Total cyanobacteria, as represented by preserved akinetes, exhibited only minor changes in the last 1000 years. However, Aphanizomenon flos-aquae, a taxon which was formerly not present in the lake 150 years ago, but that now dominates the summer phytoplankton, has shown major increases over the past 100 years. The changes in sediment composition are consistent with activities including timber harvest, drainage of wetlands, and agricultural activities associated with livestock grazing, irrigated cropland, and hydrologic modifications.
Limnology and Oceanography, 1999
Fossil pigment analyses and 19 year-long historical records were used to quantify whole-lake algal response to changes in optical and chemical properties following experimental acidification of Lake 302 with H 2 SO 4 (south basin, 302S; 1981-1989) or HNO 3 (north basin, 302N; 1982-1986) and HCl (1987-1989). Undisturbed sediments were collected by freeze-coring, sectioned in approximately annual intervals, and analyzed for fossil carotenoids, chlorophylls, and derivatives by high performance liquid chromatography. Concentrations of fucoxanthin (diatoms, chrysophytes, some dinoflagellates) were correlated with algal standing crop (r 2 ϭ 0.67, P Ͻ 0.05; 1978-1989) and increased 6-fold following acidification of Lake 302S with H 2 SO 4 from pH 6.6 to 5.0, consistent with observed reductions in dissolved organic carbon (DOC) from 7 to 4.5 mg liter Ϫ1 , improved water clarity, and increased biomass of deep-water chrysophytes. However, fucoxanthin concentrations declined to baseline values in sediments from 1988 to 1990, concomitant with severe acidification to pH 4.5, continued DOC loss (Ͻ1.5 mg liter Ϫ1) and an estimated 8-fold increase in the penetration of UVb radiation (UVR-b). Increased penetration of ultraviolet radiation (UVR) was recorded also by increased relative abundance of pigments characteristic of UVR-transparent environments. In contrast, pigments from green algae (Chl b, pheophytin b, lutein-zeaxanthin) doubled during acidification with H 2 SO 4 , while those from cryptophytes (alloxanthin) were unaffected and diatoxanthin from diatoms declined. Patterns of ubiquitous -carotene, Chl a, and pheophytin a suggested that total algal biomass increased ϳ200-400% by the mid-1980s, but declined to near-baseline under severe acidification. Variance partitioning using redundancy analysis captured 80-83% of variation in fossil chlorophylls and carotenoids and suggested that the direct effects of pH were greater (ϳ50% of total variance) than those of irradiance (ϳ12%), but that ϳ20% of variance was attributable to factor interactions. Fossil concentrations of pigments from green algae and diatoms increased ϳ100% following acidification of Lake 302N to pH 6.1, but there were few signals of deep-water blooms, possibly because DOC remained 3.5-5.0 mg liter Ϫ1. Such complex interactions between pH, DOC, and light may help explain the high variability of algal biomass response to lake acidification.
2002
A fossil diatom record covering the past 3000 cal. years BP was analyzed from a small lake in northwesterń Quebec near the northern limit of present-day tree-line. Fragilaria virescens var. exigua Grunow in Van Heurck was the dominant species throughout the core with abundances ranging between 13-35% of the total valve count. There was a replacement of alkaliphilous taxa by acidophilous taxa beginning ca. 1300 cal. yr ago, probably reflecting long-term, natural acidification processes. A diatom-based transfer function was used to provide quantitative estimates of variations in lakewater dissolved organic carbon (DOC). These inferred values showed 21 that DOC concentrations have remained stable over the past 3000 years (mean 6 S.D. 5 5 6 0.43 mg C l ), suggesting relatively constant allochthonous carbon inputs and underwater light conditions during the late Holocene. The reconstructed DOC data were compared to the palynological record from the same lake. Our study indicates that, in contrast to paleolimnological records from lakes in central and western Canada, climatic variations and associated vegetational shifts have been too subtle to cause pronounced variations in DOC in thiś northern Quebec site.