Recent trends in accumulation rate, elemental and isotopic composition of organic matter in the Magu bay, Lake Victoria

Stable isotope composition of organic carbon (OC), 14C data, OC and nitrogen content of recently deposited sediments in Magu Bay of Speke Gulf, Lake Victoria are used to document accumulation rates, sources and distribution of organic matter in the bay. The stable isotope values of both organic carbon and nitrogen decrease towards offshore, and this trend is associated with increase in the contents of organic carbon and nitrogen. The isotope results show that the organic material deposited in the bay are generally derived from C4 type of plants and are not transported far from the river mouth. Also the results show that preservation of organic matter is high in open water probably due to high primary productivity owing to high concentration of nutrients and low in turbidity. Low isotope values in offshore sites indicate that the available stock of nutrients far exceeds the demand. Sedimentation rates in the bay are not high and range from 5 to 54 cm/ka. This could be attributed to trapping efficiency by shoreline aquatic macrophyte. Furthermore, the mean accumulation rates of organic carbon and nitrogen for the bay, range from 6.92 to 57.25 gC/m2/yr and 0.51 to 4.37 gN/m2/yr, respectively, and show that Magu Bay is currently experiencing eutrophication. Tanzania Journal of Science Vol. 31 (1) 2005: pp. 23-3

Geochemical evidence (C, N and Pb isotopes) of recent anthropogenic impact in south-central Chile from two environmentally distinct lake sediment records

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Journal of Quaternary Science 25 (2010): 1100-1112, doi:10.1002/jqs.1364.In this paper, we compare the elemental and isotopic (C, N, Pb) geochemistry of lake sediments from two contrasted environments in South-Central Chile. The first lake, Laguna Chica de San Pedro (LCSP), is situated in the urbanized area of the Biobio Region (36°S). The second lake, Lago Puyehue (40°S), is located 400 km to the southeast of LCSP and belongs to an Andean national park. Our aim is to identify environmental impacts associated with increasing industrial activities and land-degradation during the last 150 years. In LCSP, shifts in C/N atomic ratios, δ13C and δ15N from 1915–1937 to the late 80’s are attributed to successive land-degradation episodes in the lake watershed. Based on a Pb isotopic mixing model, we estimate that up to 20% of lead in LCSP sediments is supplied from urban atmospheric pollution. By contrast, human impact in the watershed of Lago Puyehue is very limited. We observe no change in organic geochemistry during the last 150 years and lead contamination remains lower than 5%, even during the last decades. Although contamination levels are much higher in LCSP than in Lago Puyehue, a peak in anthropogenic Pb is recorded during the same period (1974–1976) at both sites. This maximum contamination level is consistent with increased industrial activity in the vicinity of Concepción.This research was partly supported by the Belgian OSTC project EV/12/10B "A continuous Holocene record of ENSO variability in southern Chile", by the Scientific Co-operation Exchange Program between University of Concepción (Chile) and University of Liège (Belgium) funded by the Belgian CGRI (Commissariat Général aux relations internationales de la Communauté Française de Belgique), and by Fondecyt project Nº 1070508. S.B. is supported by a BAEF fellowship (Belgian American Educational Foundation), and by an EU Marie Curie Outgoing Fellowship under the FP6 programme

Recent climate-driven ecological changes in tropical montane lakes of Rwenzori Mountains National Park, central Africa

Rwenzori Mountains National Park, which straddles the border between the Democratic Republic of Congo and Uganda, has experienced rapid glacier loss since the beginning of the twentieth century, yet there has been little investigation of aquatic biodiversity change in the park. This study presents a paleolimnological analysis from Lake Mahoma (2990 m asl), which is situated in the bamboo-forest transition zone. Diatom and organic geochemistry data from a 39-cm-long sediment core with a basal age of c. 1715 CE were compared with new analyses of previously published data from Lakes Bujuku (3891 m asl) and Lower Kitandara (3989 m asl), in the alpine zone. Comparisons were made to determine if aquatic ecosystem changes exhibited similar inter-lake patterns over the past ~ 150 years of climate warming and glacial recession, or if only local change was apparent. The diatom flora of Lake Mahoma is acidophilous, dominated by Aulacoseira ikapoënsis since at least the mid eighteenth century. In recent decades, the obligate nitrogen-heterotroph Nitzschia palea increased in importance, concurrent with declining δ15Norg values. We suggest that these late twentieth century changes were linked to regional warming and increased thermal stratification of Lake Mahoma. Regional comparisons of the Rwenzori lakes were done using existing organic geochemistry records (total organic carbon, C/N and δ13Corg) and through diatom compositional turnover analyses, and categorisation of species into one of four diatom growth morphology traits, or guilds: tychoplanktonic, high-profile, low-profile and motile. Over the past 150 years, all three lakes showed unidirectional, compositional diatom turnover, indicating that deterministic processes had affected diatom communities. Declining turnover at each site is broadly mirrored by an increase in tychoplanktonic taxa, along with concomitant declines in high-profile diatoms at Lake Mahoma, and low-profile diatoms at Lake Bujuku, and at least for the past 60 years, at Lower Kitandara. The interplay between diatom guilds at all sites is mainly a consequence of competition for available resources. Sediment organic carbon at all sites comes from both autochthonous and allochthonous sources, the relative abundances of which are influenced by the time elapsed since lakes had glaciers in their catchment

Paleolimnological Assessment of Six Lakes on the Kissimmee Chain, with Implications for Restoration of the Kissimmee-Okeechobee-Everglades system, Florida, USA

Whitmore TJ, Riedinger-Whitmore MA, Reed ZE, Curtis JH, Yang H, Evans DE, Cropper NR, Alvarado KS, Lauterman FM, Scott A, Leonard CR, Franklin DL. 2020. Paleolimnological assessment of six lakes on the Kissimmee Chain, with implications for restoration of the Kissimmee–Okeechobee–Everglades system, Florida, USA. Lake Reserv Manage. 36:218–242. The Kissimmee Basin in south central Florida contains a large, freshwater network that includes the Kissimmee River and nearly 2 dozen lakes that are headwaters of the Florida Everglades. Management of these lakes is an important part of Everglades restoration. We report a paleolimnological investigation of 6 lakes in the Upper Kissimmee Basin. Engineering activities connected the lakes and permanently altered hydrology in the 19th and 20th centuries. The lakes were naturally meso-eutrophic, but changes in lake levels and nutrient loading contributed to different degrees of eutrophication. Cyanobacteria were present historically at low levels in Lakes East Tohopekaliga, Cypress, and Tohopekaliga, but increased during the 20th century. Lake Jackson lacked cyanobacteria until recently, but Lakes Kissimmee and Marian have had high levels of cyanobacteria since predisturbance times. Profound changes in the lakes occurred after engineering activities eliminated natural large fluctuations in water levels that periodically dried large portions of the basins. Salt-tolerant biological indicators previously alternated with freshwater organisms. Large water-level fluctuations moderated aquatic-plant standing crops and reduced organic matter accumulation. Lakes Kissimmee and Marian showed greatest evidence of former associated wetlands, but lacked large variations in water levels. We recommend disconnecting these lakes from each other and from the Kissimmee River to reestablish large, natural fluctuations in water levels that were part of healthy ecosystem function. Former wetlands should be restored to slow the downstream cascade of nutrients to Lake Okeechobee and the Everglades. This study demonstrates that paleolimnology is useful for assessing hydrological changes that potentially affect lake restoration efforts

Recent paleoenvironmental changes recorded in three non-anadromous lakes in Southwest Alaska: effects of climatic and vegetation dynamics on lake productivity

Thesis (M.S.) University of Alaska Fairbanks, 2009"Paleolimnological investigations, landscape analyses, and repeat photographs were used to provide a long-term view (~150 yrs. BP to present) of nutrient dynamics and lake ecosystem change in southwest Alaska. Recent major changes in lake ecology and landscape are generally attributed to climate warming since the end of the Little Ice Age and to the recent warm phase of the Pacific Decadal Oscillation. Disturbances driven by climate, glacial retreat, and volcanism also contribute to changes in aquatic-driven processes. Sediment cores reveal a complex yet progressive set of changes that are expressed in the study lakes. Changes in the biogeochemical proxies began in the mid-19th to early-20th century, but major inflections occurred significantly later, most pronounced after 1950. Among these changes are increases in biogenic opal, and indicators of enhanced C and N cycling. These systems act as integrators of climatic, terrestrial, and aquatic processes without additions of marine-derived nutrient subsidies from spawning salmon and thus allow us to isolate and identify factors (e.g. productivity, spawning and rearing success of salmonids, or terrestrial nutrient inputs) important for interpreting sediment records in anadromous systems"--Leaf iiiNational Park Service SWAN Inventory and Monitoring Program (NPS Project / Task Agreement No.: J9W88030009)1.1. General Introduction -- 1.2. Previous research/background -- 1.3. Paleoenvironmental reconstruction -- 1.4. General introduction summary -- 1.5. References -- 2.1. Introduction -- 2.2. Study area -- 2.3. Methods -- 2.4. Paleolimnology and paleoproductivity -- 2.5. Results -- 2.6. Discussion -- 2.7. Conclusion -- 2.8. References -- 3.1. General conclusion -- 3.2. References

Increased dependence on nearshore benthic resources in the Lake Simcoe ecosystem after dreissenid invasion

Changes in the lower trophic level of Lake Simcoe, Canada, coincident with the invasion of dreissenids have been well documented, but little is known regarding the effects of these changes on the pathways of energy flow to higher trophic levels. To evaluate pathways of energy flow, we analyzed stable isotopes of zooplankton, benthic invertebrates, and fish over a 26-year period. Using stable isotopes of carbon (C) and nitrogen (N), we found evidence for a dramatic increase in the importance of benthic-derived nearshore primary production in Lake Simcoe after the invasion of dreissenids; δ13C of benthos collected at 5 and 10 m depth increased by 4–5‰ on average, and benthic warmwater fishes demonstrated a similar increase. In contrast, δ13C of profundal (≥20 m) benthos and pelagic zooplankton were not significantly different during this time period, while offshore pelagic and profundal fishes changed more subtly in magnitude but in the same direction as nearshore benthos and warmwater fishes. The range of δ13C values observed across the fish community increased from 3 to 10‰, primarily due to a positive temporal shift among warmwater fishes. Our study highlights the increase in functional heterogeneity in Lake Simcoe after dreissenid invasion, likely due to an increase in nearshore benthic production. Accounting for increased contributions of benthic-derived C with time is critical in accurately modelling C and energy transfer in the lake, and for better understanding the degree of nearshore–offshore coupling in the lake

Lake Sedimentary Environments and Roles of Accumulating Organic Matter in Biogeochemical Cycling Processes and Contaminants Loading Are Invasions of Water Hyacinth in Lake Victoria from 1989 a Concern?

Sediments accumulated in lake basins consist of various organic and inorganic materials, mostly utilized as proxies for climatic changes and as historical records of the lake connectivity to terrestrial ecosystems and anthropogenic activities. In-lake production, aerial wet and dry deposition and transported materials in running water are the main sources of lake deposits, which may be permanently deposited as bottom sediments or remobilized through erosive forces and turbulence, resuspension, tunneling by organisms, and porewater exchanges with the overlying water mass. Examination of the sediment biodiversity, quality, composition, and stratigraphy is part of the approaches in understanding ecological and climatic changes and other anthropogenic impacts in lakes. There are no detailed studies on the spatial distribution of sediment characteristics within the Nyanza Gulf, especially after the establishment of water hyacinth. The first observations on the nature of the bottom of Lake Victoria were made during 1927–1928 survey, with subsequent detailed geochemical core studies concentrated in the main lake. Roles of sediment organic matter are explained, and data from surficial sediments collected, from about 32 sampling sites between 1994 and 2012, are used to characterize the sediments. Lastly, the potential influences from increased urbanization, eutrophication, presence of water hyacinth (Eichhornia crassipes), and associated floating macrophytes since 1989 and current cage aquaculture in L. Victoria are explored

A 2200-year record of Andean Condor diet and nest site usage reflects natural and anthropogenic stressors

Understanding how animals respond to large-scale environmental changes is difficult to achieve because monitoring data are rarely available for more than the past few decades, if at all. Here, we demonstrate how a variety of palaeoecological proxies (e.g. isotopes, geochemistry and DNA) from an Andean Condor (Vultur gryphus) guano deposit from Argentina can be used to explore breeding site fidelity and the impacts of environmental changes on avian behaviour. We found that condors used the nesting site since at least approximately 2200 years ago, with an approximately 1000-year nesting frequency slowdown from ca 1650 to 650 years before the present (yr BP). We provide evidence that the nesting slowdown coincided with a period of increased volcanic activity in the nearby Southern Volcanic Zone, which resulted in decreased availability of carrion and deterred scavenging birds. After returning to the nest site ca 650 yr BP, condor diet shifted from the carrion of native species and beached marine animals to the carrion of livestock (e.g. sheep and cattle) and exotic herbivores (e.g. red deer and European hare) introduced by European settlers. Currently, Andean Condors have elevated lead concentrations in their guano compared to the past, which is associated with human persecution linked to the shift in diet.Fil: Duda, Matthew P.. Queen's University; CanadáFil: Grooms, Christopher. Queen's University; CanadáFil: Sympson, Lorenzo. Sociedad Naturalista Andino Patagonica; ArgentinaFil: Blais, Jules M.. University of Ottawa; CanadáFil: Dagodzo, Daniel. University of Ottawa; CanadáFil: Feng, Wenxi. Queen's University; CanadáFil: Hayward, Kristen M.. Queen's University; CanadáFil: Julius, Matthew L.. St. Cloud State University; Estados UnidosFil: Kimpe, Linda E.. University of Ottawa; CanadáFil: Lambertucci, Sergio Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Layton Matthews, Daniel. Queen's University; CanadáFil: Lougheed, Stephen. Queen's University; CanadáFil: Massaferro, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Michelutti, Neal. Queen's University; CanadáFil: Pufahl, Peir K.. Queen's University; CanadáFil: Vuletich, April. Queen's University; CanadáFil: Smol, John P.. Queen's University; Canad

Long-term perspectives on terrestrial and aquatic carbon cycling from palaeolimnology

Lakes are active processors and collectors of carbon (C) and thus recognized as quantitatively important within the terrestrial C cycle. Better integration of palaeolimnology (lake sediment core analyses) with limnological C budgeting approaches has the potential to enhance understanding of lacustrine C processing and sequestration. Palaeolimnology simultaneously assimilates materials from across lake habitats, terrestrial watersheds, and airsheds to provide a uniquely broad overview of the terrestrial-atmospheric-aquatic linkages across different spatial scales. The examination of past changes over decadal–millennial timescales via palaeolimnology can inform understanding and prediction of future changes in C cycling. With a particular, but not exclusive, focus on northern latitudes we examine the methodological approaches of palaeolimnology, focusing on how relatively standard and well-tested techniques might be applied to address questions of relevance to the C cycle. We consider how palaeolimnology, limnology, and sedimentation studies might be linked to provide more quantitative and holistic estimates of lake C cycling and budgets. Finally, we use palaeolimnological examples to consider how changes such as terrestrial vegetation shifts, permafrost thaw, the formation of new lakes and reservoirs, hydrological modification of inorganic C processing, land use change, soil erosion and disruption to global nitrogen and phosphorus cycles might influence lake C cycling