Phytotaxa 127 (1): 49–57 (2013) www.mapress.com / phytotaxa / Copyright © 2013 Magnolia Press
Article
ISSN 1179-3155 (print edition)
PHYTOTAXA
ISSN 1179-3163 (online edition)
http://dx.doi.org/10.11646/phytotaxa.127.1.8
Three new Psammothidium species from lakes of Olympic and Cascade Mountains in Washington State, USA MIHAELA D. ENACHE1, MARINA POTAPOVA1, RICH SHEIBLEY2 & PATRICK MORAN2 1
Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA, 19103 Email:
[email protected] (corresponding author) 2 U.S. Geological Survey, Washington Water Science Center, 934 Broadway, Suite 300, Tacoma, WA 98402
Abstract Populations of several Psammothidium species were found in core sediments from nine remote, high elevation, ultraoligotrophic and oligotrophic, Olympic and Cascade Mountain lakes. Three of these species, P. lacustre, P. alpinum, and P. nivale, are described here as new. The morphology of the silica frustules of these species was documented using light and scanning electron microscopy. We discuss the similarities and differences with previously described Psammothidium species. Key words: diatom, lake sediments, alpine lakes, LM, SEM
Introduction Diatom assemblages were analyzed in core sediments from nine Washington Cascade Mountains lakes. These lakes were selected by the U.S. Geological Survey (USGS) for a paleolimnological investigation of the impact of inorganic nitrogen atmospheric deposition on lake biogeochemistry. However, these lakes are still generally considered oligotrophic systems. Species of Psammothidium Bukhtiyarova & Round (1996: 3) are very abundant (up to 28% relative abundance) and diverse in study lakes and they were investigated with both light (LM) and scanning electron microscopy (SEM). Psammothidium was separated from Achnanthidium Kützing (1844: 75) by Bukhtiyarova & Round (1996) to designate adnate taxa commonly attached to sand grains by the raphe valve face, as opposed to Achnanthidium species, which are more common on stable surfaces such as rocks and plants and found attached via short mucilaginous stalks. Bukhtiyarova & Round (1996) pointed out that the major morphological differences between Psammothidium and Achnanthidium are (1) the shape of the valve, oval-elliptic as opposed to linear/linear-capitate; (2) the convex flexure of the raphe valve as opposed to concave in Achnanthidium; (3) striae reaching the sternum as opposed to marginal in Achnanthidium; and (4) raphe fissures located in a central channel (or near the valve center) as opposed to non-channeled with pin-hole central endings in Achnanthidium (Bukhtiyarova & Round 1996).
Among Psammothidium species occurring in the study lakes, based on silica frustule morphological characteristics, three species are new to science. Here we describe those new species using light (LM) and scanning electron microscopy (SEM) observations.
Material and Methods Sediment cores were collected by USGS crews in the summer of 2009 from nine lakes in Olympic, North Cascades, and Mt. Rainier national parks, located at a minimum elevation of 1335 m. A summary of lake physical characteristics is given in Table 1. Cores were collected by boat from the deepest portion of each lake using a Uwitec gravity corer (http://www.uwitec.at/). Accepted by M.B. Edlund: 21 Mar. 2011; edited version received at publisher: 4 Jun. 2013; published: 29 August 2013. Licensed under a Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0
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TABLE 1: Physical properties of study lakes. OLYM—Olympic National Park, NOCA—North Cascades National Park, MORA—Mt. Rainier National Park. Study Lake Eunice Lake Snow Lake Copper Lake Hidden Lake Stiletto Lake Thornton Lake Heather Lake Hoh Lake Milk Lake
Park MORA MORA NOCA NOCA NOCA NOCA OLYM OLYM OLYM
Elevation (m) 1640 1438 1600 1835 2066 1384 1589 1335 1435
Area (ha) 5.32 2.39 5.14 24.98 0.03 22.65 0.40 7.40 1.10
Max. Depth (m) 10.05 9.75 21.03 61.56 25.9 31.69 7.01 14.93 11.88
Diatom slides were prepared using strong acid digestions in a microwave (CEM model MDS-21 00) with enclosed vessels, and temperature and pressure monitoring and control systems. Diatom-coated coverslips were mounted on glass slides using Naphrax R mounting medium (http://diatom.ansp.org/nawqa/ protocols.asp). Diatom species were investigated in core top (0–0.5-cm depth) and bottom sediments, and in an additional interval from Snow Lake (2–2.5 cm). A Zeiss Axio Imager microscope equipped with AxioCam MRm digital camera was used for LM. For SEM, cleaned material was dried on aluminum stubs, which were sputter-coated with Pt-Pd and observed with a Zeiss Supra 50 VP FE SEM (Carl Zeiss, Jena, Germany) at an accelerating voltage of 10 kV. Terminology used to describe valve structure follows Anonymous (1975), Bukhtiyarova & Round (1996) and Round et al. (1990). Water samples for nutrient analysis were collected and processed according to methods outlined in the USGS National Field Manual (US Geological Survey, 2006; Wilde et al., 2004). Water chemistry measurements indicated that the study lakes are ultraoligotrophic or oligotrophic (Table 2). TABLE 2: Water chemistry of study lakes from surface water collections, 2009. *Sample date also represents sediment core collection date. LAKE NAME Snow Lake Eunice Lake Hoh Lake Heather Lake Milk Lake Stiletto Lake Copper Lake Lower Thornton Lake Hidden Lake NOCA
Sample Date* 10/7/2009 11/4/2009 9/8/2009 9/10/2009 9/11/2009 8/26/2009 9/22/2009 9/23/2009 9/24/2009
Total-N (mgL-1)
