Journal of Paleolimnology最新文献

I was thrilled to receive a Lifetime Achievement Medal at the 15th International Paleolimnology Symposium (IPS) in Bariloche, Argentina (2022). I will use this opportunity to tell the story of how I stumbled into the field of paleolimnology, a discipline I had not heard of until I entered graduate school. In retrospect, I feel extremely lucky to have been able to spend the last five decades addressing interesting paleoclimate/paleoenvironment questions. Furthermore, my research and teaching have taken me to many biologically fascinating and culturally intriguing places around the world. I will also use this forum to express my gratitude to the many mentors, colleagues, students, friends, and acquaintances with whom I have collaborated throughout my career. Whatever success I have enjoyed, I attribute to my good fortune in having been able to work with numerous talented and hard-working fellow scientists.

Hypereutrophic conditions in lake ecosystems are generally associated with nutrient inputs from surrounding terrestrial landscapes. However, some systems can receive primary nutrient inputs through hydrologic connections such as rivers or canals. Lake Carlton, Florida, USA is a small, shallow, polymictic lake that ends a hydrologically connected string of lacustrine systems with hypereutrophic lakes Beauclair and Apopka. Lake Beauclair and Lake Apopka were connected hydrologically when a system of canals was constructed beginning in 1893 CE. These lakes have maintained hypereutrophic conditions despite extensive management to reduce nutrient inputs. Here, we collected a sediment core from Lake Carlton to accomplish two primary research objectives: 1) reconstruct the nutrient input for Lake Carlton throughout the last ~ 150 years to conduct source assessment, and 2) link primary producer changes with management actions between lakes Apopka, Beauclair, and Carlton. Paleolimnological tools were applied to a 165-cm sediment core and analyzed for bulk density, organic matter content, nutrients (C, N, P), photosynthetic pigments, and total microcystins. Sediments were dated using ²¹⁰Pb and results indicate that the core represents over 150 years of sediment accumulation. Sedimentary nutrient concentrations show that the primary driver of nutrient inputs resulted from canal construction, beginning in 1893 CE, which corresponded to increased nutrient deposition. Photosynthetic pigment data indicate dramatic increases in most primary producer groups coinciding with the hydrologic modification. However, around ~ 1970 CE, primary producer communities shifted from diatom dominance to cyanobacterial dominance, which appeared to be linked to internal nutrient dynamics and competition among phytoplankters within the lake ecosystem. Cyanotoxin production records show a significant lag between cyanobacterial dominance and peak cyanotoxin production with toxins increasing in the last 30 years. These data demonstrate that local nutrient inputs do not govern all phytoplankton dynamics in shallow lake systems but must be interpreted considering hydrologic alterations and management practices.

Abstract

Lakes are particularly vulnerable to environmental changes and thus considered sentinels and integrators of processes that occur in the atmosphere and terrestrial environments. Individual up to ecosystemic metabolic pathways and nutrient cycling in lakes respond to both natural and human disturbances. Disentangling the effect of such different forces is a particular challenge for lake ecological studies. Here we present a conference paper based on previous studies carried out in Andean-Patagonian lakes under two important events: the Puyehue–Cordón Caulle eruption in 2011 and the glacial recession with a glacial lake outburst flood (GLOF) in 2009. We discuss how biological variables responded to these two natural events that produced the input of minerogenic inorganic particles into the lakes. We present the combination of observational and experimental research, including new molecular methods, that contributed to understanding the effects of these inorganic particles on aquatic ecosystems. Both events involved changes in the transparency of the lakes that affected phytoplankton parameters (biomass vertical distribution), bacteria composition and community structuring process. Finally, both events had very contrasting effects on zooplankton, in the same range of particle concentrations. Particles from glacial melting are beneficial for daphnids reducing the impact of ultraviolet radiation and increasing the quality of the food. In contrast, volcanic ashes are abrasive materials that have a deleterious effect for filtering zooplankton.

Pistia stratiotes L. (water lettuce) is a floating tropical macrophyte long identified and managed as a non-native species within the State of Florida and other areas of the southern United States. Macrofossil seeds from Lake Annie, Florida, however, indicate abundant presence of P. stratiotes intermixed with other locally native macrophytes from ~13,500 to ~12,000 calibrated years before present (cal yr BP). This was soon after the lake depression first began filling with water as the piezometric groundwater surface of the Florida peninsula rose in response to rising seas during the transition (~18,000 to ~11,000 cal yr BP) from the Last Glacial Maximum (LGM) to the Holocene interglacial. These macrofossil records join several other lines of evidence supporting native status of P. stratiotes in the Florida peninsula. While recent cryptic invasion of non-native Pistia genotypes into some of Florida’s freshwater ecosystems also appears likely, confirmed paleo-presence and contemporary persistence of native P. stratiotes subpopulations may have especially important management and conservation implications for Florida’s spring-fed streams. Palaeobotanical evidence of this type may be useful in further resolving the global biogeography of P. stratiotes and other cryptic aquatic plant species.

In California, severe precipitation events (SPEs) are often associated with winter season atmospheric rivers. These SPEs can generate hurricane-scale precipitation, creating a variety of natural hazards such as floods and landslides. For California, the most complete SPE-flood record yet generated is a 9000-year paleoflood reconstruction from the Santa Barbara Basin (Du et al. in Mar Geol 397:29–42, 2018). Finding terrestrial counterparts to compare to the Santa Barbara Basin is a challenge in Southern California where lake basins are rare and the terrestrial spatiotemporal signature of SPE floods remains largely unconstrained. Here, we present five 1–2 m sediment cores from a sag pond along the San Andreas Fault in the southern Carrizo Plain. The most complete record (core CLPC21-4) was selected for a variety of chronological, sedimentological, and biological analyses. Principal Component Analysis on these data reveals two end member sediment unit types: event versus ambient sedimentation. We focus on the two thickest sediment units likely generated by SPEs. These two units (EU 1 and EU 2) are especially distinct within CLPC21-4, characterized by erosive bases, above average sand content, normal grading, low magnetic susceptibility, and low total organic matter. Moreover, they are visually apparent across all five cores within the sag pond and thin from source to sink. Age control for the two units is constrained by AMS ¹⁴C dates on discrete organic materials and supported by the identification of Erodium’s first appearance ca. 1750–1765 CE in the Santa Barbara region. Using these age constraints, we infer the maximum limiting age range for Event Unit 1 from 1470 to 1640 CE and Event Unit 2 from 1740 to 1800 CE. Within the limits of dating, site-specific proxy sensitivities, and inherent meteorological heterogeneity, we propose a probable correlation to Santa Barbara Basin flood events at 1525 CE and 1760 CE. Our results suggest that sag ponds may represent a viable and untapped paleoclimatic archive for California. Future work will focus on a latitudinal series of sag ponds to determine the spatiotemporal sequence and correlativity of SPEs in the sediment record.

Reports have shown that even remote lakes have been negatively affected by anthropogenic activities. This study used metal concentrations and enrichment factors to comprehensively determine key metal sources and identify potential impacts of recent anthropogenic activity in remote Central Highland Tasmanian (Australia) lakes. Metal concentrations (Al, As, Cd, Cu, Fe, Pb, and Zn) in these lakes remain below Australian interim sediment quality guidelines but have been slowly increasing since the start of the twentieth century. This increase is likely related to increasing organic matter content, rather than any direct, increased input of metals. The largest anthropogenic impact to these systems was damming, which typically led to an increase in organic matter content either directly, by the trapping of particles and nutrients, or indirectly, by stimulating primary production in the lake. This increased organic matter content, in turn, increased the retention of metals, manifesting as an increase to measured metal concentrations. Minor impacts are the historical use of lead shot, leaded petrol, and industrial processes, which may have contributed to the higher Pb enrichment, compared to the other studied metals, in these lakes. Despite recent concerns of metal contamination in the Tasmanian Wilderness World Heritage Area from distant mining activities, there is no strong evidence in this study indicating that lakes in the Central Highlands (a similar distance away) have been impacted by long-distance atmospheric deposition. This is likely related to the decreased rainfall, and thus decreased rates of wet deposition of aerosols in the east of Tasmania, compared to that of the west and in the Tasmanian Wilderness World Heritage Area.

The story I offer provides an intimate look at my passion and dedication to diatoms and Paleolimnology, narrating my journey from the first discoveries to my growth as a researcher in this field.

The article discusses the challenges and opportunities facing interdisciplinary attempts to produce knowledge about water and lake-related processes. It examines key aspects of the long-standing debates on this topic and discusses the state of the art providing empirical examples. The article argues that, notwithstanding the significant progress achieved in disciplines and fields of knowledge relevant to water-related research, the development of interdisciplinary coordination, particularly between the physical–natural and the social sciences remains underdeveloped. However, the fact that the extreme global crisis affecting water and life in the planet, more generally, has a primarily anthropogenic nature suggests that there are urgent reasons to promote greater collaboration between different forms of knowledge relevant to these processes. The main objective is contributing to raise awareness about obstacles and opportunities for enhanced interdisciplinary coordination in these areas, to tackle the urgent problems facing the socio-hydrosphere.

Sedimentological and palynostratigraphy studies were used to evaluate sediment-stacking patterns in a depth range between 400 and 50 m in the Kemar-1 well section, Bornu (Chad) Basin, Nigeria. The greyish-sandy claystone, rich micaceous, lithified, and unlithified greyish claystone, dark well sorted micaceous sandstone, and poorly sorted and heterolithic clayey sandstones are the major facies components recognised in the well sections. The lithofacies characteristics were used to delineate and assign depositional environments ranging from lacustrine to fluvial settings. Paleoecological results revealed that the dominant palynofloral associations are angiosperm pollen and pteridophytic spores and they were tentatively grouped under three ecological groups which include freshwater, mangrove/brackish and savannah depositional environments in wet to dry climatic conditions during sediment formation. The presence of Echitricolporites spinosus was used to define the Echitricolporites spinosus palynological zone. The basal section at 390–385 m interval in the well shows the dominance of Psilatricolporites crassus, Verrucastosporites usmensis, and Monoporites annulatus, which marked the Eocene boundary from the overlying Miocene marker bed species of Echitricolporites spinosus, Grimsdalea magnaclavata, Anthocerus sp., Nymphaea lotus, and Retistephanocolpites gracilis. The palynomorph data and lithological characteristics from the studied well section have been used to establish that the Chad Formation is of late Eocene to early Miocene age, and that it unconformably overlies the Kerri–Kerri Formation that was deposited in varying lacustrine, fluvial and prograding shoreface and deltaic settings. This study has resolved the controversy surrounding the age of the Chad Formation, the challenge in depositional environment reconstruction. Finally, the stratigraphic framework of the Chad Formation in the study area is presented.