Diatom-inferred aquatic impacts of the mid-Holocene eruption of Mount Mazama, Oregon, USA

Abstract

High-resolution diatom stratigraphies from mid-Holocene sediments taken from fringe and central locations in Moss Lake, a small lake in the foothills of the Cascade Range, Washington, have been analyzed to investigate the impacts (and duration) of tephra deposition on the aquatic ecosystem. Up to 50 mm of tephra was deposited from the climactic eruption of Mount Mazama 7958–7795 cal yr BP, with coincident changes in the aquatic ecosystem. The diatom response from both cores indicates a change in habitat type following blanket tephra deposition, with a decline in tychoplanktonic Fragilaria brevistriata and Staurosira venter and epiphytic diatom taxa indicating a reduction in aquatic macrophyte abundance. Additionally, the central core shows an increase in tychoplanktonic Aulacoseira taxa, interpreted as a response to increased silica availability following tephra deposition. Partial redundancy analysis, however, provides only limited evidence of direct effects from the tephra deposition, and only from the central core, but significant effects from underlying environmental changes associated with climatic and lake development processes. The analyses highlight the importance of duplicate analyses (fringe and central cores) and vigorous statistical analyses for the robust evaluation of aquatic ecosystem change.

Diatom responses to long‐term climate and sea‐level rise at a low‐elevation lake in coastal British Columbia, Canada

“…, Egan et al. ), and/or nutrient enrichment (Fritz and Anderson , Neil and Gajewski ), which were likely consequences of the Mazama tephra deposition. Michelutti et al.…”

“…3). These particular taxa have been shown to respond to tephra deposition, high Si:P ratios (Saros et al 2005, Egan et al 2019, and/or nutrient enrichment Anderson 2013, Neil andGajewski 2017), which were likely consequences of the Mazama tephra deposition. Michelutti et al (2016) suggest that tephra deposition also reduces the availability of benthic or epiphytic habitats in lakes through decreased light penetration and the destruction of aquatic macrophytes.…”

Diatom-inferred ecological responses of an oceanic lake system to volcanism and anthropogenic perturbations since 1290 CE

“…Besides noteworthy differences in the size and morphometric characteristics of both basins which make Lake Empadadas more sensitive to any subtle precipitation regime change, the effects of the P17 eruption were irrelevant in this lake compared to Lake Azul. Contrary to the effects of the deposition of thin tephra layers which do not override the long-term changes due to climate change (e. g., Lotter et al, 1995;Telford et al, 2004;Egan et al, 2019), any climatic signature on productivity in Lake Azul has been largely obscured by the massive tephra deposition of 1290 CE. Any paleoclimatic reconstruction based on the study of the diatom and bulk organic matter records in Lake Azul would therefore be largely biased by the overprinting of the volcanic signature after the cataclysmic eruptive episode of 1290 CE, so using alternative proxy data should consequently be preferred instead.…”

A palaeoecological study investigating the impacts of multiple tephra depositions on a lacustrine ecosystem in Northeast China, using diatoms as environmental indicators

“…Tephra particles in lakes can increase water turbidity (Mayr et al 2019), reducing light penetration and autochthonous photosynthesis (Burwell 2003). The formation of a water-sediment interface barrier in the bottom of lakes can occur (Eastwood et al 2002), as tephra tends to cement and form an impermeable layer when reacting with water (Egan et al 2018). This disturbs nutrient exchange between the sediment and the water, particularly reducing the possibility for nutrients to diffuse into the water column from the bottom sediment (Harper et al 1985;Lotter et al 1995;Hutchinson et al 2019).…”

“…1). The more widely documented changes include increase in water turbidity (Mayr et al 2019), benthic habitat smothering (Hickman and Reasoner 1994), increased in lake SiO 2 from tephra particle dissolutions (Barker et al 2000), as well as occurrence of a water-sediment interface barrier which restricts P-loading (Eastwood et al 2002;Egan et al 2018;Harper et al 1985;Lotter et al 1995;Hutchinson et al 2019). Chrysophytes, another widespread group of algae that produce siliceous resting cysts which are also well preserved in sediments (Adam and Mahood 1981;Sandgren 1991;Pla et al 2003), although less extensively used than diatoms, can also be employed as indicators of a lake's condition, in complement to diatoms.…”