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1. Sea-level rise and settlement at Ek Way Nal: Coring the past

   Foster, Cher; McKillop, Heather; Sills, E Cory (July 2023, Research reports in Belizean archaeology)

   Excavations in the spring and summer of 2022 were carried out at the underwater ancient Maya salt work of Ek Way Nal in Punta Ycacos Lagoon, Paynes Creek National Park, Belize. Ek Way Nal provided salt to the ancient Maya during the Late and Terminal Classic periods (600-900 C.E.). In additional to excavations in buildings at the site, a 1 X 2 m unit was excavated to extract a sediment column for examining the relationship between the ancient Maya settlement at Ek Way Nal and sea-level rise. In this article, the excavations, extraction of the sediment column, and processing it for laboratory analyses are described. Field observations are discussed. Fine red mangrove root (Rhizophora mangle) and charcoal samples were extracted from the sediment column for radiocarbon dating. The results from the datum core excavation indicate that sea-level rise occurred before, during, and after the ancient Maya occupation at Ek Way Nal. 

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2. Sedimentary DNA and molecular evidence for early human occupation of the Faroe Islands

   https://doi.org/10.1038/s43247-021-00318-0  

   Curtin, Lorelei; D’Andrea, William J.; Balascio, Nicholas L.; Shirazi, Sabrina; Shapiro, Beth; de Wet, Gregory A.; Bradley, Raymond S.; Bakke, Jostein (December 2021, Communications Earth & Environment)

   Abstract The Faroe Islands, a North Atlantic archipelago between Norway and Iceland, were settled by Viking explorers in the mid-9th century CE. However, several indirect lines of evidence suggest earlier occupation of the Faroes by people from the British Isles. Here, we present sedimentary ancient DNA and molecular fecal biomarker evidence from a lake sediment core proximal to a prominent archaeological site in the Faroe Islands to establish the earliest date for the arrival of people in the watershed. Our results reveal an increase in fecal biomarker concentrations and the first appearance of sheep DNA at 500 CE (95% confidence interval 370-610 CE), pre-dating Norse settlements by 300 years. Sedimentary plant DNA indicates an increase in grasses and the disappearance of woody plants, likely due to livestock grazing. This provides unequivocal evidence for human arrival and livestock disturbance in the Faroe Islands centuries before Viking settlement in the 9th century. 

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3. Paleolimnological evidence for primary producer change linked to hydrologic connectivity and human impacts in Lake Carlton, Florida, USA

   https://doi.org/10.1007/s10933-024-00318-y  

   Clift, Troy L.; Waters, Matthew N. (April 2024, Journal of Paleolimnology)

   Guangjie Chen (Ed.)

   Abstract 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 using²¹⁰Pb 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. 

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4. Roles of Nutrient Limitation on Western Lake Erie CyanoHAB Toxin Production

   https://doi.org/10.3390/toxins13010047  

   Barnard, Malcolm A.; Chaffin, Justin D.; Plaas, Haley E.; Boyer, Gregory L.; Wei, Bofan; Wilhelm, Steven W.; Rossignol, Karen L.; Braddy, Jeremy S.; Bullerjahn, George S.; Bridgeman, Thomas B.; et al (January 2021, Toxins)

   null (Ed.)

   Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin, and a Planktothrix spp. bloom in Sandusky Bay. Recently, the USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate phosphorus and nitrogen (N) limitation of biomass and toxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystin under nutrient repletion with slight induced P limitation under 40% dilution, and the Sandusky Bay bloom produced anatoxin under N limitation in both dilution treatments. The results demonstrate the importance of nutrient limitation effects on microcystin and anatoxin production. To properly combat cyanotoxin and cyanobacterial biomass production in WLE, both N and P reduction efforts should be implemented in its watershed. 

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5. Effects of climate change and episodic heat events on cyanobacteria in a eutrophic polymictic lake.

   https://doi.org/10.1016/j.scitotenv.2019.07.220  

   Bartosiewicz, Maciej (January 2019, Science of the total environment)

   null (Ed.)

   Changes in mixing regimes and CO2 availability may promote harmful cyanobacterial blooms in polymictic lakes and ponds globally, but the underlying mechanisms still remain unclear. We integrated results from a natural experiment comprising an average-wet year (2011) and one with heat waves (2012), a long-term meteorological dataset (1960–2010), historical phosphorus concentrations and corresponding sedimentary pigment records, to determine, on different temporal scales, the mechanistic controls of cyanobacterial blooms in a eutrophic polymictic lake. Intense warming in 2012 was associated with: 1) increased stability of the water column with buoyancy frequencies exceeding 40 cph at the surface, 2) high phytoplankton biomass in spring (up to 125 mg WW L-1), 3) reduced downward transport of heat and 4) persistently depleted epilimnetic CO2 concentrations. CO2 depletion was effectively maintained by intense uptake by phytoplankton (influx up to 30 mmol m-2 d-1) in combination with reduced carbon inputs from the watershed during dry periods. Under eutrophic conditions these effects triggered massive bloom of buoyant cyanobacteria (up to 300 mg WW L-1). Complementary evidence from polynomial regression modelling using long-term datasets revealed that warming is the most important predictor of cyanobacterial abundance during the second half of the last century explaining 78% of the observed positive trend, whereas phosphorus concentration explained only 10% thereof. Together the results from the interannual comparison and the multi-decadal record indicate that hotter and drier climates increase water column stratification and decrease CO2 availability in eutrophic polymictic lakes. This combination catalyzes blooms of buoyant cyanobacteria. 

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