1 a Memorial to Frithjof Sterrenburg: the Importance of the Amateur Diatomist

1 A Memorial to Frithjof Sterrenburg: The Importance of the Amateur Diatomist

Janice L. Pappas Department of Mathematics, University of Michigan, Ann Arbor, USA

Abstract Frithjof A.S. Sterrenburg was an amateur diatomist who became an expert in taxonomy, nomenclature, microscopy, and photomicrography. He is best known for his work on Gyrosigma Hassall and Pleurosigma W. Smith but contributed in many areas of diatom research. Because of who he was and the nature of his interactions with the diatom community, he has had and will continue to have a lasting impact. His contributions to diatom research have influenced our understanding and usage of diatom taxonomy and nomenclature and how taxonomy informs ecological, biostratigraphic and other biological studies. His affable yet incisive character enabled him to be a teacher and mentor to professionals and amateurs and to be respected and appreciated internationally. Keywords: Diatoms, Gyrosigma, Pleurosigma, microscopy, amateur diatomists, photomicrography, museum collections, taxonomy, valve morphogenesis, constructal morphology

1.1 Introduction

Throughout science, amateurs have contributed to the body of knowledge in many dis- ciplines. Amateurs dedicate themselves to the pursuit of knowledge concerning their specific interests, and when it comes to diatoms, this is no exception. During the 1800s, diatom research was conducted by hobbyists who had occupations in very different fields (Bahls 2015; Gordon et al. 2009). For example, Friedrich Traugott Kützing was a pharmacist and schoolCOPYRIGHTED teacher who became a diatomist. MATERIAL He discovered that diatoms were composed of silica and had two parts to their shells, one was “primary” and the other “secondary,” and was aided in publishing his findings by C.G. Ehrenburg, the preeminent zoologist and diatomist of the time (Werner 1977). Some amateurs formed microscopical societies or clubs as enthusiasts pursuing their common interest in the microscopic world (e.g., The Quekett Microscopical Club). In the post-Victorian world, diatom research has become professionalized, and currently, individuals can find

Corresponding author: jlpappas@umich.edu

1 2 Diatoms: Fundamentals and Applications

Figure 1.1 Frithjof A. S. Sterrenburg at his microscope. (courtesy of H. van Dam) professional mentors for formalized training to become a diatom researcher as one’s occupation. Having said this, modern amateur or citizen scientists are still making contributions to diatom research. Because so few individuals are formally trained, credentialed, paid, and have a career specifically in diatom research, and because diatom research is at a stage where the enormity of necessary work involves potentially hundreds of thou- sands of species, amateurs have a vital role to play. Amateurs who engage in this role seriously soon realize that contributing requires associating oneself with professionals, especially concerning technical matters in taxonomy, nomenclature, microscopy, and photomicrography. The quintessential example of the modern amateur diatomist was Frithjof Sterrenburg (Figure 1.1). He died on March, 11, 2016 and left his mark on diatom research. He had passion and dedication to diatom research that earned him recognition and respect from professionals internationally. Frithjof’s work in diatom taxonomy and nomenclature as well as microscopy and photomicrography has benefited professional and amateur diatomists alike, and his contributions have continued to be influential in the way diatom researchers engage in and pursue their studies. No matter how one perceives what it means to be an amateur, Frithjof transcended the notion because of who he was and how he lived his life. Historically, amateur diatomists were unpaid and typically worked in various occupations (Bahls 2015; Werner 1977). A prime example was Astrid Cleve-Euler. She was the first female to be awarded a doctorate in science at Uppsala University, Sweden in the late 19th century. Yet, throughout her life, she was never employed as a scientist despite her contributions to chemistry, botany, geology, and diatom research (Swedish Sterrenburg, The Amateur Diatomist 3

Natural History Museum). Even van Leeuwenhoek (17th to 18th century) who was a tradesman and politician did not get paid to study the microscopic world (Pedrotti accessed on 2016; Sterrenburg 1982). Other dedicated amateurs engaged in diatom research. Pleurosigma angulatum, originally named Navicula angulata by John Thomas Quekett (Sterrenburg 1990a), an amateur diatomist who was a microscopist and histologist, was typified by the Reverend William Smith, an amateur turned academic who was a prominent diatom researcher in the Victorian era (Werner 1977). As a common leisure activity, diatoms were mounted in various configurations, slides were either purchased or prepared by the individual, and mounts were viewed with microscopes situated in Victorian parlors (Lynk accessed on 2016). Diatom mounters such as Johann Diedrich Möller (originator of the art of diatom mounting) (Walker 2009) and dentist William Gatrell (Stevenson 2009) were much in demand to produce intricate arrangements for viewing. The advent of the microscope and its common usage paved the way for such activities and induced the proliferation of amateur diatomists interested in the natural history of these eye-catching, exquisite microorganisms. Frithjof was a throwback, in a sense, to this ilk of diatom researcher. Yet, he developed his own style and went beyond amateurs such as surgeon and physician John Redmayne (Stevenson 2013) and teacher John Albert Long (Walker 2012). Like Quekett, Redmayne and Long plied their trade as amateur diatomists in the late 19th and early 20th century. They bought and sold diatom samples as well as made mounts and relied on popular publications such as Hardwicke’s Science Gossip for the latest information on diatoms (e.g., Taylor 1885). In Hardwicke’s volume XXI from 1885, an article on Jacques-Joseph Brun’s publication, “The Diatoms of the Alps and the Jura,” was presented in which Brun, a pharmacologist and diatomist (JStor Global Plants accessed on 2016), talked about the deposition of diatoms over time and the formation of Kieselgühr (Taylor 1885). His taxonomic work like that of his contemporaries on fossil diatoms provided the impetus for the commencement of Adolph Schmidt’s Atlas in 1874 (Schmidt et al. 1874–1959) that was continued with contributions from oth- ers until 1959—including Friedrich Hustedt, a teacher turned professional diatomist who has had a great influence on diatom research (Alfred Wegener Institute 2015). Frithjof’s trajectory into diatom research was more along the lines of Smith, Brun, and Hustedt. Like these predecessors, Frithjof progressed from amateur to expert, garner- ing respect for his expertise. Frithjof elevated his contributions to the level of scientific peer-review rather than being only presentable in popular publications, and like many of his predecessors, he has had a lasting impact on diatom research.

1.2 Background and Interests

Frithjof A. S. Sterrenburg was born in 1934. Originally, he studied medicine at Amsterdam University. His autodidactic nature conflicted with a formalized education approach, and inevitably, he would venture out on his own. He was well-read and able to learn various subjects at many levels of difficulty and did so as a life-long endeavor. For Frithjof, life and learning was an adventure. 4 Diatoms: Fundamentals and Applications

Figure 1.2 Frithjof playing the trumpet with trombonist Bill Rank from the Paul Whiteman orchestra (1968). (permission from C.J.Sterrenburg)

Figure 1.3 Frithjof in his backyard, extolling a friend to see into the night sky (circa 1980). She and her biologist husband were hosts of the Sterrenburgs in Sulawesi, Indonesia. (permission from C.J. Sterrenburg)

Frithjof showed a propensity for immersing himself in a wide range of learning experiences, and some of his emerging talents were expressed in such divergent fields as music (e.g., Sterrenburg 1967) and astronomy. In his youth, Frithjof played trumpet (Figure 1.2), saxophone, clarinet, and piano in big-band style orchestras, and he also arranged compositions for such orchestras. He was a jazz musician for many years (de Wolf, personal communication). He owned many telescopes (Figure 1.3). Some of Frithjof’s first publications in the early 1980’s described how to see the stars more clearly (Sterrenburg 1983a, b). He liked to share conversations about the stars with many people, including long-time friends Michael Stringer and Wulf Herwig, as he relished being able to see beyond our immediate world. Frithjof was a tinkerer and had a knack for all things electronic, electrical and mechanical (e.g., Sterrenburg 1979). Frithjof shared an interest in electrical devices with Sterrenburg, The Amateur Diatomist 5

Wulf and long-time friend Hein de Wolf. He loved airplanes (van Dam, personal communication) and loved to restore vintage cars and motorbikes as well as military radio receivers, which he collected to round out his fascination with the military. He authored manuals on receivers (de Wolf, personal communication; Sterrenburg 1970a) and was on the editorial board of professional electronics journals (Sterrenburg et al. 2007). He was an avid motorbike rider noted Michel Poulin while on a visit to the Sterrenburg home. Hein was always surprised when Frithjof would show up at his office. Would Frithjof be attired in his motorcycle outfit or an extravagant suit (de Wolf, personal communication)? His knowledge and interest in history (Hargraves 2016) as well as documenting and saving historical collections (Hamilton, personal communication), included military history (e.g., Sterrenburg 1970b; Weaver & Sterrenburg 1968) specifically about World War II (WWII). The decoding of the German Peenemünde docu- ments contained in the Oslo Report was amassed in a perceptive compendium written by Frithjof (Sterrenburg year unknown; Stringer, personal communication). Much of Frithjof’s outlook on life was influenced by his experiences as a youth. Frithjof came of age during a time when the world was in the grip of economic depres- sion and followed by WWII, having family members that suffered during the times of Nazi Germany (Herwig, personal communication). He grew up during the 1930s and 1940s, and his personal recollections were compiled in 2009 in a web forum on WWII aircraft (Hargraves, personal communication; Sterrenburg 2009a). He knew much about that period in human history, and although he was sensitive about the effect that era had on himself (Poulin, personal communication), he was interested in how other individuals were affected as well (Sterrenburg & Toonder 1972). Over the years, Frithjof and his dear wife, José (Figure 1.4), built a good life together. They enjoyed their largest restoration project of an 1890 Victorian house in the small farming village of Sijbekarspel, North Holland. It was a labor of love where they lived for 35 very happy years. As Michel Poulin recalls, their home was “very well maintained and had a nice garden.” For over 40 years, Frithjof was self-employed in communications, advertising and public relations as a consultant to research centers and hi-tech indus- tries in the fields of communications, medical instrumentation (e.g., Sterrenburg 1983c), aviation, defense, pharmaceuticals, energy production, and environmental sciences. He enjoyed interacting with clients, and with his effusive manner, he completed each project with the close attention to detail it deserved. Frithjof and José loved to travel throughout Europe, especially in the Balkans, Greece and Portugal, the Pacific Islands (Rarotonga and Western Samoa) Indonesia, Australia, New Zealand, and the Western United States which included California (especially San Francisco), Nevada, Utah, Colorado, Arizona, and Florida. Holidays were spent in Germany and England, once on a vintage motorbike, and once along Australian's East coast on a modern motorbike. For work purposes, Frithjof travelled to the United Arab Emirates. Frithjof and José got to see many parts of the world and experience many cultures and ways of living. As a colorful individual who had a gift for storytelling (Figure 1.5), Frithjof was forthright, strong-willed, and not afraid to engage in conversations or debates on controversial subjects (e.g., science vs. religion, formally unveiled posthumously in Sterrenburg 2018). Frithjof was eloquent and forceful in his opinions, explications, and disquisitions. There was no mistake about where Frithjof stood on any given subject (e.g., Sterrenburg 1976, 1977), and he acted on his strong convictions. Although 6 Diatoms: Fundamentals and Applications

Figure 1.4 Frithjof and José relaxing amongst the trees and flowers (circa 1978). (permission from C.J. Sterrenburg)

Figure 1.5 Frithjof telling a tall tale (1985). (permission from C.J. Sterrenburg) Sterrenburg, The Amateur Diatomist 7

Frithjof and José were in the process of moving to Heiloo at the time of the 2003 North American Diatom Symposium (Gordon, personal communication), Frithjof was also reticent about traveling to the U.S. because of his opposition to the 1990 Gulf War; instead, he sent a video presentation with a “cheerful toast at the end” for viewing at the meeting (Hamilton, personal communication). Frithjof was a cosmopolitan individual, bearing witnessing to various modes of life and immersing himself in the plethora of ideas he encountered. He was of nimble mind, turning those ideas into self-taught knowledge and assembling that knowledge into a finely-honed result. This attitude served him well in his scientific pursuits involv- ing diatoms.

1.3 The Personality of an Amateur Diatomist

Whether engaging a client, friend, or diatom enthusiast, Frithjof always had time to attend to your inquiry, and he did it with his usual affability, a bit of flare, inten- sity of focus, and a dry, sharp sense of humor (e.g., Stringer, personal communication; Hargraves, personal communication). His command of and facility for languages (Hargraves 2016) was always on display with a deftness in elocution that embellished your sensibilities about the subject being discussed. When engaging in a conversation with Frithjof, sometimes you were taken on a “ride” that you had no idea was about to happen. When corresponding with Frithjof during the compilation of the special issue on diatom nanotechnology and the difficul- ties encountered in trying to get the issue published in a timely fashion, I found myself drawn into a discussion of metaphorical representations from ancient Greek history and mythology to deal with the situation. We exchanged musings on Helen of Troy, Medea and Aegeus. One of the regular editorial board members let me know that I was the impetus for restarting the process of publication, so I ended up being the protago- nist, with a transformation from Helen of Troy to Medea, as determined by Frithjof. The antagonist? Those involved with the special issue may remember the exchange of e-mails that occurred during this “tragicomedy” and may surmise who might be the antagonist. Frithjof and I determined that he was not Aegeus, and therefore was no match for Medea! When Paul Hargraves e-mailed Frithjof and told him he could not recall meeting him at a conference, Frithjof sent a picture of “himself” that Paul quickly determined was Austrian Admiral Hermann Freiherr von Spaun (Austrian Admiral Hermann Freiherr von Spaun accessed on 2016). Disappointed that the ruse was quickly dis- pelled, Frithjof received an unidentified picture of royal dignitaries from which he was asked to identify Paul. Frithjof knew the picture was of the nine sovereigns at Windsor for the funeral of King Edward VII, and he chose Albert the 1st of Belgium to be Paul (Albert the 1st of Belgium accessed on 2016). However, as Paul stated, he is unaware of any relation to Albert (Hargraves, personal communication). Frithjof’s sense of humor was always on display as a source of amusement for anyone who communicated with him. Frithjof possessed admirable knowledge of the Old Testament as he exchanged quotes in English or German with Joseph Sechback whom he called Methuselah. 8 Diatoms: Fundamentals and Applications

During a visit to Edam, Joseph and his wife were treated to a ride in Frithjof’s sports car on their way to a tour of a cheese factory (Sechback, personal communication). Richard Gordon found out from Frithjof that being an itinerant biologist who has a small number of degrees of separation from Erdös (a sort of “close encounter of the Erdös kind”), may induce metamorphosis into an Erdös-like being (Gordon 2011)! In an eloquent speech at the Dutch-Flemish Association of Diatomists in the Spring of 2016, Herman van Dam memorialized Frithjof. During the advent of the Nederlands – Vlaamse Kring van Diatomisten (NVKD), Herman met Frithjof, and they had a long and prosperous friendship. He talked about Frithjof’s love of diatoms and reiterated the nature of the eclectic mix of interests, endeavors and knowledge that character- ized Frithjof. He spoke of Frithjof’s contributions, along with Hein de Wolf, to the Diatomededelingen, for which Frithjof penned six articles. That Frithjof contributed many publications on Gyrosigma and Pleurosigma, among other taxa, was highlighted by Herman, as well as stating that Frithjof was recognized as an international expert in diatom research. Herman noted that Frithjof was a person of strong opinions and principles (van Dam, personal communication). Herman also noted that Frithof possessed the quality of magnanimity, for example, in his willingness to help and counsel individuals, including himself, on diatom taxonomic and nomenclatural matters. Paul Hargraves said, “he gave most generously of his time and expertise (on identifying a Gyrosigma), and it was included in one of his many publications on the genus, graciously including me as a co-author, as he did with our subsequent collaborations on Haslea.” Wulf Herwig found Frithjof to be extremely intelligent, wise and humor- ous and always helpful. Jackie White-Reimer remembers Frithjof as a warm, gracious person. When she and her family were house guests, Frithjof and José “went out of their way to make us comfortable and show us around. … They even rented a car big enough to accommodate all of us because theirs was too small.” The Reimers and Sterrenburgs spent time at each other’s homes, where Frithjof was a “considerate house guest.” Frithjof even made an indelible impression on the Reimer’s daughters, Laura and Emilie, ages 12 and 10 at the time. They remember him having a British accent and having an easy, friendly, nice, and happy personality. Emilie remembered that Frithjof gave them a tin of gingerbread cookies on the sly, which delighted them to no end (White-Reimer, personal communication). Some individuals were fortunate to receive holiday well-wishes with wonderful displays of Frithjof’s photographic talents (Figures 1.6–9). There were dazzling displays of diatoms and otherworldly entities. His generous nature extended to identifying diatoms and instructive comments on microscopy to professionals and amateurs directly or via the web. Often, his name appeared in the acknowledgments for his contribution toward correct identification and/or correct nomenclature of the diatom taxa consid- ered. He was especially beneficent with his time as people sought his expertise concerning Gyrosigma and Pleurosigma species. Michael Stringer was especially effusive in his sentiments about Frithjof with whom he shared many interests. As Michael appreciatively said, “he was always there to help me,” and “he transformed my study of diatoms that exists today.” Michael also said that Frithjof’s favorite sweets were English licorice, Christmas puddings, and Christmas cakes laced with whisky and brandy (Stringer, personal communication). Frithjof defi- nitely had a taste for the fruits of life! Sterrenburg, The Amateur Diatomist 9

Happy Christmas from Frithjof and a ne 2007!

Figure 1.6 Digital Christmas card sent to friends in 2006.

Merry christmas and a happy 2009! Josephine and Frithjof Sterrenburg

Figure 1.7 Digital Christmas card sent to friends in 2008.

Frithjof embodied a many-faceted personality (de Wolf, personal communication). He had many friends that remember those qualities that made him a unique person (Herwig, personal communication; Stringer, personal communication). Klaus Kemp and Phil Basson gave tribute to Frithjof on the diatom-l website as one “who has contributed so much to the study of Diatoms and was so supportive of the amateur fraternity with encouragement and donations of material from Sulawesi and other locations,” and that Frithjof “was a true gentleman.” (Kemp & Basson 2016) 10 Diatoms: Fundamentals and Applications

Figure 1.8 Digital Christmas card sent to friends in 2010.

Figure 1.9 Digital Christmas card sent to friends in 2011. Sterrenburg, The Amateur Diatomist 11

1.4 The Amateur Diatomist and the Importance of Collections

Frithjof was a Research Associate at the National Natural History Museum “Naturalis” in Leiden, The Netherlands. He visited and used collections at various museums and understood their value. An advocate for museums, Frithjof was vociferous on this score (Sterrenburg 1990b), both in print and on the web, extolling the virtues of collections, access to collections, documenting collections, and having someone in charge of the stew- ardship of and communications about collections. In 1990, he explicated the meaning collections have as a basis for taxonomy, morphology and ecology research, especially in diatom research (Sterrenburg 1990b, 2002a). In 1991, Hein de Wolf and Frithjof undertook the task of updating Fryxell’s 1975 paper by conducting an international survey of diatom collections to enhance access (de Wolf & Sterrenburg 2003). As Frithjof said,

Taxonomy is not stamp collecting, but (re)defining the biological individuality of the taxa (“names”) described. This can only be done reliably if you examine the original materials to define an unequivocal standard of reference (the “type”) and this shows the great value of Museum collections and the stalwarts who look after them! (Sterrenburg 2011a)

and

For such studies to make any sense at all, good taxonomy is an indispensable requirement and, despite financial constraints, diatom taxonomy has flourished in the past 25 years, just as it did in the second half of the 19th century. It is now universally accepted that taxonomy must be based on the investigation of the original materials from which species were originally described, by the process called typification, as in the course of time misidentifications have accumulated, leading to an erroneous shift in the species paradigm. Hence the crucial importance of collections of original materials. (Sterrenburg & de Wolf 2004)

Herman van Dam stated that Frithjof was dedicated to the preservation of collections (van Dam, personal communication). With Hein de Wolf, Frithjof published papers on the Kinker collection (Sterrenburg & de Wolf 1993, 2004; de Wolf & Sterrenburg 1993). Johannes Kinker was a stockbroker by profession and a Victorian-era amateur diatomist of high repute who amassed an extensive diatom collection (Sterrenburg & de Wolf 1993). He did not publish, but Henri-Ferdinand van Heurck, the industrialist and chemist as well as amateur diatomist, microscopist and botanist (Robbrecht 2007), had stated that Kinker’s collection contained “masterpieces” (Stevenson 2009). The discovery of the collection was a testament to the dedication of Frithjof and Hein to enable recognition of Kinker’s contribution to diatom research as an amateur and the importance of museum collections. They gave homage to the amateur diatomist more generally by stating that,

It has been fashionable to picture these Victorian investigators as quaint Daddy Longlegs irrelevantly chasing after obscure creatures, but that image is false. Laying the foun- dations of science is never irrelevant, and the current classification of diatoms and 12 Diatoms: Fundamentals and Applications

practical scientific applications of diatom studies were given a sound basis by the work of these earlier investigators. Kinker need not have been modest because he was “only an amateur.” So were most of his contemporaries, and the position of “amateur-savant” was a respectable and even distinguished one in his time. In fact, if modern trends in financing of Science continue, we may well see a return to that situation in our lifetime. (Sterrenburg & de Wolf 1993)

1.5 The Amateur Diatomist as Expert in the Tools of the Trade

From a very young age, Frithjof was interested in the natural world, especially wild flowers, insects, and diatoms. His inquisitive nature and fascination with electronics and physics was but a precursor for his developing interests. As chronicled in a brief webpage (Sterrenburg 2014a), when Frithjof was 12 years old, he had a Victorian drum microscope. At the time, his family lived in a house where the cellar had a foot of standing sewage water. Being a lad with a curiosity about bacteria, Frithjof sampled some of the odoriferous concoction, placed it on a coverslip, and mounted it in Canada balsam. He brought the slide to his family doctor, who had a Zeiss microscope, and upon viewing, discovered that Spirillium was present. His father had introduced him to the microscope and gave Frithjof his window into a whole new world. Frithjof was articulate, witty, erudite and incisive, self-confident, and with his eclectic knowledge immersed himself in any topic that suited his interest. With his fascination of the microscopic world, Frithjof developed his love of diatoms. His abilities with light microscopy, sample and slide preparation, and photomicrography were the result of much trial and error, and he was rewarded repeatedly for his determination and dedication while studying diatoms. Frithjof saw that there were many facets to diatom research. Field work and collecting water samples were just the beginning (Figure 1.10). Preparing those samples for viewing in the microscope was a sizable consideration, and Frithjof learned quickly about the link between handling samples and pretreatment of the materials to mini- mize damage or the loss of diatoms. Whether using water samples, mica fragments, or dry materials, Frithjof was cognizant of the various protocols for the most appropriate treatment (Sterrenburg (Year unknown) accessed on 2016). Frithjof developed detailed protocols concerning the mounting process to produce the best results. His tutelage on making and viewing morphologically-meaningful diatom slide mounts was clear. As Frithjof would remind us, “NEVER, repeat NEVER, make a preparation on the slide, always on the cover-slip. Preparation on the slide results in serious deterioration of image quality” (Sterrenburg 2002b, 2006a). Frithjof’s expertise in microscopy was second to none (Sterrenburg 1975, 2002b, 2013a), and he was cogently instructive on the concepts for basic, sound usage of the light microscope (Sterrenburg 2011b). In e-mails with Paul Hamilton, Frithjof was even concerned about the position of the arm of the microscope (i.e., facing toward or away from the user) because this had an impact on how to read slide location scales Sterrenburg, The Amateur Diatomist 13

Figure 1.10 Frithjof and a student taking samples in Florida (circa 1982). (permission from C.J. Sterrenburg)

(Hamilton, personal communication). He did image quality comparisons among objectives (Sterrenburg 2012a, b), and he was always interested in optics (Sterrenburg 2009b, 2012a, b), including weighing the thickness of a diatom’s silicification and what effect the refractive index of mounting media would have on image resolution. In response to queries on the diatom-l listserv, Frithjof summarized some “salient points” on microscope optics, including phase contrast (Sterrenburg 2009b) and differential interference contrast or Nomarski (Sterrenburg 1978):

1. check whether your microscope has “infinity corrected” objectives, or objectives corrected for a tube length of 160 mm by looking at the engraving on your objectives. It either mentions “160” or gives the infinity symbol. You cannot combine objectives that differ in this respect. 2. the usual phase contrast objectives give better contrast, but lower resolution 3. plan objectives are not relevant for diatoms, they give flat images to the edge, but diatoms usually cover only the centre of the image. Also, diatoms themselves are not flat! 4. a condenser of more than NA 1.0 MUST always be oiled to the slide with immersion oil. This is messy and inconvenient so 90% of people use their condenser “dry”. In that case, its effective NA will never be greater than 1.0 even if the specification says it has NA 1.4. 5. also, contrast will decrease with higher effective condenser NA. The best option for low-contrast diatoms is DIC but that requires special optics (objectives and condenser) and is expensive. 6. You need not aim at the highest possible resolution if you can also do SEM. That solves all problems. Many genera are not even identifiable without SEM. 14 Diatoms: Fundamentals and Applications

7. to summarize: unless your work aims at critical taxonomic separation of difficult and very finely structured taxa, I'd recommend a good modern NA 1.3 objective. If you go for the ultimate, DIC supported by SEM is the best option. (Sterrenburg 2012c)

Frithjof was very methodical in his approach to understanding microscope optics and microscopy. Illumination was an important factor in stellar microscopic technique, and Frithjof, being a keen observer, recognized annular oblique illumination as one way to obtain a phase contrast effect (Sterrenburg 1975, 1978, 2010a). Frithjof, being at the forefront of knowledge about lighting options, he tested the utility of LEDs with various microscope optics arrangements, and in another diatom-l post, referring to the case since 2004:

…since then, more suitable LEDs have appeared. I have tested some white LEDs of 1W (circa3.5V, 0.3A) and smaller, which have a luminescent area of about 3 mm. For Köhler illumination, this may be too small if the microscope condenser has a large bottomlens, with the smaller diameter lenses of Leitz condensers, including the Heine, it’s sufficient. However, one need not use Köhler, critical illumination is quite satisfactory. In that case, very low powers can be used without any problem simply by unscrewing the top lens. Objectives of the highest NA can also be used without any problem, in contrast to what the article referred to states. … Even the small LEDs, combined with a good collector, are far too bright to use at full power visually in simple brightfield! As for uneven illumination of the field of view: this is simply remedied nowadays by using image-processing software that permits background subtraction. (Sterrenburg 2009c)

The right kind of optics and proper illumination enabled light microscopists to develop skill to see at the limits of resolution using diatom strew mounts. Frithjof was masterful in this craft, and as he said, “… microscope users will be familiar with such mellifluous names as Pleurosigma angulatum or Frustulia rhomboides because these have been standard test objects to check the quality of their lenses - and, especially, the quality of their microscope expertise… (Sterrenburg 2002a), and “Diatoms are com- monly used to test the quality of the objectives - and even more so, the expertise of the microscopist.” (Sterrenburg 2012b) As a natural outcome of his interest and ability in microscopy, Frithjof, along with Peter Höbel (2011), elucidated the technique of using ultraviolet or blue light photomicrography to obtain a crisp, 3D effect when material is not available for scan- ning electron microscopy (SEM) determination (Höbel & Sterrenburg 2011). Another technique was developed by Frithjof along with Hamilton and Williams (2012) to locate specimens on microscope slides regardless of the brand of microscope, and this technique circumvents the need to scribe or ink rings around specimens or purchase an England Finder (Hamilton, Williams & Sterrenburg 2013; Sterrenburg, Hamilton & Williams 2012). He used his knowledge and creative thinking in concocting what- ever piece of equipment, microscope lens (Sterrenburg 2006b, Sterrenburg 2011b) or illuminator (Sterrenburg 2002c) that was necessary to view diatoms with clarity. He embraced technological improvements and applied the fine details of his amassed Sterrenburg, The Amateur Diatomist 15 knowledge to microscopic and slide preparation techniques in his quest to do exem- plary diatom taxonomic studies. Frithjof saw taxonomic puzzles as his opportunity to meet the challenge of doing scientific sleuthing with all the twists and turns one would encounter in finding solutions (e.g., Sterrenburg 2011a).

1.6 The Amateur Diatomist as Peer-Reviewed Scientific Contributor

Frithjof was resourceful in solving problems, utilizing his many talents. He was mindful of the role of past amateurs in diatom research and knowledgeable about the history that intertwined the advent of microscopy and popular interest in diatoms. Diatoms became his special interest after looking at the Reverend William Smith’s description of Gyrosigma tenuissimum in 1853 and found it to be wonting. The puzzle to be solved—the original description stated that the valves had deeply curved sides; other descriptions stated it had straight sides. Smith’s material was not accessible for decades, but when it was, with his keen eye, nimble mind and technical ability, Frithjof solved the puzzle by finding straight sided valves, contrary to Smith’s original description. The road to discovery was fraught with twists and turns, but along with Myriam de Haan and Wulf Herwig, a “lucky break” (Sterrenburg Sterrenburg, de Haan, & Herwig 2014) emerged so that the puzzle could be solved. With this, Frithjof was hooked and on his way to making a lasting presence with his love of studying diatoms. Frithjof first published on diatoms in the 1970s. He was instrumental in advanc- ing diatom taxonomy and nomenclatural studies of many taxa (e.g., Sterrenburg 1988). In one tabulation derived from AlgaeBase (Guiry & Guiry accessed on 2017), Frithjof named, either alone or with colleagues 39 species (and/or varieties): 16 Gyrosigma, 8 Pleurosigma, 8 Haslea, two Frustulia (with Horst Lange-Bertalot) (Lange-Bertalot & Sterrenburg 2004), two Anorthoneis, one Nitzschia, one Surirella, one Petrodictyon, and the holotype Talaroneis furcigerum (Grunow) Sterrenburg (Kooistra, Forlani, Sterrenburg, & Stefano 2004). Many other taxa were subjected to Frithjof’s careful assessment. As a testament to Frithjof, Gyrosigma sterrenburgii Stidolph, Pleurosigma sterrenburgii Stidolph, Neidium sterrenburgii Metzeltin and Lange-Bertalot, and Rhopalodia sterrenburgii Krammer were named after him (Guiry and Guiry accessed on 2017). Frithjof’s most notable contributions in diatom taxonomy and nomenclature are his work on Gyrosigma and Pleurosigma, with publications spanning the decades from 1989 to 2013 as sole author (e.g., Sterrenburg 1989, 1990c, 1991a, b, 1992, 1993a, b, 1994a, b, 1995a, b, 1997, 2000, 2001a, 2002d, 2003a, 2003b, 2007) or with collaborators (Jahn & Sterrenburg 2003; Jahn et al. 2005; Sterrenburg & Tiffany 2004; Sterrenburg & Underwood 1997; Sterrenburg et al. 2000, 2003a, b; Sunesen et al. 2013; Sar et al. 2012, 2013; Liu et al. 2015). As Paul Hamilton observed, “Frithjof was thorough and precise in his work. I think I can say that he was ‘part of the old school’ where attention to detail was critical and worth the extra time in getting the research right before publishing.” Frithjof was diligent and meticulous in naming and correcting taxon misidentifications and in devising new 16 Diatoms: Fundamentals and Applications morphological characters to aid in identifications in Gyrosigma and Pleurosigma (e.g., Sterrenburg 1991b, 1993b). Frithjof’s taxonomic insightfulness and “eagle-eye” was evident in his comments in a diatom-l post concerning a 2012 publication on Pleurosigma intermedium from Guam. Frithjof stated:

… (on) the recent publication on Guam diatoms: (Lobban, C.S., Schefter, M., Jordan, R.W., Arai, Y., Sasaki, A., Theriot, E.C., Ashworth, M., Ruck, E.C. & Pennesi, C. (2012). Coral-reef diatoms (Bacillariophyta) from Guam: new records and preliminary checklist, with emphasis on epiphytic species from farmer- fish territories. Micronesica 43(2): 237-479.) showed itself to be helpful when I checked some provisional identifications in my own samples from the Pacific. As an update, here are some data on Pleurosigma intermedium W. Smith, because the specimens the authors present are not that species…

In LM, P. intermedium has a broader apex and (arrow) a “calcar”, absent in the Guam specimens. This calcar corresponds to an accessory fissure in SEM. In SEM, P. intermedium has a row of internal marginal duplex areolae that contin- ues around the apex. In the Guam specimen, the apical margin is unperforated. In P. intermedium the internal central raphe nodule is surrounded by a rather wide non- areolated field, in the Guam specimen the areolae continue right up to the central nodule. Note also the difference in shape for the central internal raphe fissure endings.

These differences are morphogenetically completely independent and the differentiation is thus based on polythetic characters. The Guam specimens do not appear to match the type of P. acus Mann 1925 as this shows a different stria density ratio. (Sterrenburg 2012d)

Frithjof displayed his consternation about correct nomenclature as distinct from taxonomic issues with comments about Haslea brittanica in two diatom-l posts (2014 b, c):

Thanks for the several replies to my question re Haslea brittannica. All respondents refer to Iconographia Diatomologica, vol. 7 (2000). I have this, and that's just the problem, as follows:

there is one LM figure, which shows perpendicularly arranged striae this is NOT from the type material

Perpendicularly arranged striae are seen in Hasleas, but also in non-Hasleas, e.g. Hustedt's section of Naviculae orthostichae. Would not SEM be required to verify the presence of the generic characters (e.g. as given in Round et al.), which are invisible in LM? Does generic transfer not require verification in the type material? There might be a look-alike. Sterrenburg, The Amateur Diatomist 17

Although I agree that Haslea may be possible, I wonder if transfer is formally valid without reference to type material specimens, and SEM in this case. (Sterrenburg 2014b)

and

To summarize the many replies I got (thanks, folks!): The transfer is formally valid according to the Code (which only requires citation of the basionym and the reference). But whether it's taxonomically correct is an entirely different matter (investigation of type, SEM). (Sterrenburg 2014c)

A comparative study of Haslea with Gyrosigma and Pleurosigma included definitive description and argument for the identification of morphological characters and separation of these diatom genera (Sterrenburg Tiffany Hinz Herwig & Hargraves 2015). Sometimes, nomenclature revisions do not make their way into the common ver- nacular of professionals and amateurs who want to identify their diatom specimens. Frithjof was always on hand to see that taxa were named correctly and make such revisions available in publications and on the web (Sterrenburg 2012b). The transfer of Surirella patrimonii Sterrenburg to Petrodictyon is a case in point that illustrated Frithjof’s ability to meld phase-contrast microscopic investigation with examination of type material for the purposes of naming the appropriate genus, and subsequent identity of the taxon in the marine littoral habitat off the coast of Sulawesi, Indonesia (Sterrenburg 2001b). Frithjof was very clear on the problems associated with unresolved issues in the appropriate naming of diatom taxa (Sterrenburg 2010b) or the status of a taxon’s name. The trials and tribulations of naming taxa are dependent on one’s microscope and optics capability, slide preparation technique, and a discerning eye in being able to see fine structural details upon examination of diatoms. Frithjof would painstakingly go through the steps to produce valid naming of a diatom taxon (Sterrenburg 2002d). His work on a project with colleagues Stuart Stidolph, Kathryn Smith, and Alexandra Kraberg culminated in the U. S. Geological Survey publication of Stidolph’s Atlas of 1000 photomicrographs of over 400 marine littoral marine diatom species (Sterrenburg 2012e; Stidolph, Sterrenburg, Smith, Kraberg, & Stuart 2012). As always, Frithjof made sure the taxonomy and nomenclature were impeccable and up to date. Frithjof saw the value in making the atlas as well as other resources available to the diatom community because he understood that there were few large compilations of information on diatoms (e.g., Sterrenburg 2013b), and the literature tends to be scattered and sometimes difficult to access. Frithjof said that the result of good taxonomic practice is “the elimination of established spurious taxa,” but the “chronic state of renovation” regarding the introduction of new genera has induced a multitude of nomenclatural changes. Documentation of taxonomic and nomenclatural changes are scattered throughout the literature, and Frithjof was an advocate of a web-based approach to amassing such information and making it readily accessible to all (Sterrenburg 2002e). At one time, Frithjof was a researcher at the Netherlands Institute of Ecology, Centre for Estuaring and Coastal Ecology. He recognized that ecological studies were 18 Diatoms: Fundamentals and Applications only as good as the soundness of the names of the taxa. He understood the multipur- posed value of taxonomic studies and was involved in studies on the epiphytic diatom flora of seagrasses from various localities (e.g., Sterrenburg et al. 1995). He published papers with his father, F. J. G. Sterrenburg, on marine littoral taxa, including Navicula orthoneoides (Sterrenburg & Sterrenburg 1991) and the naming of a new species, Nitzschia nienhuisii (Sterrenburg & Sterrenburg 1990). The diatom flora is cosmopolitan. However, determining specific epithets for the diatom flora, not previously known from intertidal seagrass habitats off the coast of Mauritania, enabled Frithjof and his father to characterize the ecology as uninfluenced by aeolian deposits (Sterrenburg & Sterrenburg 1990). Frithjof, along with Michael Stringer, was interested in studying the diatom pop- ulation dynamics of “The Car Park Lagoon,” one lagoon among a series of marine tidal lagoons on Two Tree Island, Essex, United Kingdom. Diatom populations had collapsed; however, by the winter of 2010, diatom blooms had returned. Frithjof and Michael documented the changes using slide mounts from samples, with Frithjof identifying the taxa present. Frithjof said, that finding diatoms in such cold conditions was not unheard of because “numerous diatom species rank among the principal cold- loving ‘extremophilic’ organisms ...” (Stringer & Sterrenburg 2011) Diatom environmental tolerances would be revisited to form a thought-provoking paper by Frithjof and colleagues. Larger issues were always on Frithjof’s mind concerning species designations and biodiversity studies. Environmental conditions can affect diatom morphology. Teratogenetic malformations in valves including not previously detected asymme- try, abnormal bends, distorted margins, and irregular striae patterns were observed such that Frithjof wondered what effect this has on the naming of species (Sterrenburg 1973). The effect of environment on diatom diversity, and biodiversity more generally, is a pervasive topic in scientific circles and the political sphere, and Frithjof was quite aware of the importance that impeccable diatom taxonomy would have as a lasting impact on identifying what is present and determining how threatened those taxa might become (Sterrenburg 2005a). In many ways, Frithjof’s attention to details and complexities of taxonomic determi- nations was his stock-in-trade as a diatomist; he stated that,

…there is the widespread misconception that taxonomy consists of the description of new species or varieties. The realization that taxonomy may instead have to start with the elimination of established but invalid ‘pseudospecies’ may come as a surprise to workers not specializing in the subject.

Along the same line,

Only when the identity of an organism has been unambiguously fixed does it become possible to determine its biological characteristics: its physiology, nutritional require- ments, habitat and biogeography. Only when these are known, the organism can become a source of information on the Earth’s history. This is especially the case for diatoms, whose siliceous exoskeleton is both taxonomically informative and durable, permitting conclusions over many millions of years. (Sterrenburg 2005a) Sterrenburg, The Amateur Diatomist 19

Diatom cytology (Sterrenburg 1994b) and morphogenesis were just as interest- ing to Frithjof as taxonomy, nomenclature and ecology. He conducted studies on raphe fissure deflection and handedness as morphogenetic characters in Gyrosigma (Sterrenburg 1993b). Along with Mary Ann Tiffany and María Esther Meave del Castillo, Frithjof was involved in valve morphogenesis studies of Pleurosigma (Sterrenburg, Tiffany & del Castillo 2005, Sterrenburg, Meave del Castillo & Tiffany 2003b), with an eye toward determining that the valves have nanostructure oval pillars in internal and external layers that are sandwiched together and not loculate in structure. Frithjof saw the importance of silica deposition in terms of the con- struction of the frustules and its connection to morphology and how this should be reflected in the taxonomy. Valve morphogenesis and its relation to constructal morphology was explored further by Frithjof. With his interest in the “engineering” of diatom silica opaline frustules and their morphology, Frithjof was led to idea of “crystal palaces” and their role in nanotechnology (Sterrenburg 2005b). Because of the link between diatom research and the desire to use technological advances, especially regarding SEM, diatoms could be studied in terms of their structure, function and morphogenetic steps in silica nanostructure formation in detail. Frithjof and colleagues Tiffany and Meave del Castillo continued studies of Pleurosigma valve morphogenesis to document the steps in valve formation (Sterrenburg et al. 2005). Gyrosigma valve formation was also found to have the non-loculate sandwich configuration, albeit slightly differently from Pleurosigma, and that these structures were found to be weaker than the loculate nanoconstructions of other diatoms (Sterrenburg et al. 2005). Frithjof and colleagues found that Pleurosigma and potentially Gyrosigma, have “speed bumps” constructed between adjacent pillars to compensate for the drawback of the non-loculate design (Sterrenburg et al. 2005). Studying diatom morphogenesis and pattern formation illustrated how Frithjof had the ability to go beyond what he already knew and how he continued to challenge himself. Along with Richard Gordon and Kenneth Sandhage, Frithjof was also an editor of the special volume on diatom nanotechnology in the Journal of Nanoscience and Nanotechnology published in 2005 where his nanostructure publications also appear (Gordon et al. 2005a,Sterrenburg 2005b; Gordon, Sterrenburg & Sandhage 2005b). To take the “constructal paradigm” further, Frithjof, Richard Gordon, Mary Ann Tiffany, and Stephen Nagy wrote a chapter for a volume on astrobiology (edited by Joseph Seckbach), examining diatom constructal morphology and its bearing on whether diatoms are extremophiles (Sterrenburg et al. 2007). Frithjof and colleagues described the various habitats, including hot springs, peat bogs, highly saline or polluted waters, and on mudflats in marine littoral zones and wondered whether such species also found in less extreme habitats would qualify as extremophilic. At the nanostructure level from their geometric design, diatoms can withstand the stresses of various physical and chemical environmental conditions impinging on their frustules. They exhibit rigid morphogenetic control and a constancy within a species. Frithjof knew that this “constructal paradigm” was still not sufficiently known to explain diatom morphological diversity of pattern formation, yet that diversity is a testament to diatom survival in all manner of habitats. Despite this, Frithjof and colleagues at this juncture were reluctant to call diatoms extremophiles (Sterrenburg et al. 2007). 20 Diatoms: Fundamentals and Applications

From the various subjects covered and their interrelationship, Frithjof exhibited his development and growth as an amateur scientist. He contributed to microscopy, sample and slide preparation methods, photomicrography, and by expounding the intricacies and interrelationships of a variety of biological fields and how they impinge on diatom research. Undoubtedly, he has had the most direct and long-lasting impact via his work on his favorite diatom genera, Gyrosigma and Pleurosigma. In his approach to diatom studies, he had the ability to communicate the essence of a problem, the ratio- nale for engaging in such studies, and how to go about finding the solution. Frithjof is the epitome of why amateurs are important in diatom research. His eloquent manner, engaging personality, and affable character made Frithjof Sterrenburg not only a unique contributor, but also one who transcended the title “amateur” to become a professional as teacher, mentor, author, and expert in diatom research. As Frithjof said, “diatom taxonomy is a specialism (Sterrenburg 2012b),” especially for those who become serious diatom researchers, as he did.

1.7 Concluding Remarks

Frithjof was the consummate amateur who became a professional, in the very best sense of the word, whether he knew you as a colleague, instructor, friend, or acquaint- ance concerning the study of diatoms. His legacy is many-fold in that he understood the intricacies of excellent microscopy practice along with slide preparation and photomicrography. More expansively, Frithjof understood and espoused the con- ceptual basis of the importance of taxonomy and resolving nomenclatural issues and how these studies provided legitimacy for diatom ecological and biostratigraphic studies as well as resulting from using cytological evidence. He was always working on diatom research, having manuscripts and involvement in projects that have yet to be published (Sterrenburg unpublished manuscripts 1996, 2002f, 2004, 2013c, d). Specifically, Frithjof is known as the authoritative source on the diatom genera Gyrosigma and Pleurosigma. For the benefit of all of those who study diatoms, his collections have been donated to and are housed in Bremerhaven, Germany at the Alfred Wegener Institute at the Friedrich Hustedt Center for Diatom Research. For 60 years, he was a very dear, loving, always cheerful and optimistic husband, as José said. In accordance with Frithjof’s wishes, as José told me, “his ashes now rest among his tiny friends, the diatoms, on the ocean floor.” Frithjof always said that his epitaph should read “Never a dull moment,” and as José absolutely agreed, his wishes were granted. As Hein de Wolf said in a diatom-l post (de Wolf 2016) with a message from José:

Never a dull moment. This is how Frithjof Sterrenburg would like to be remembered. A malignant tumour attacked his brilliant brain. It put an end to his happy and valuable life on the eleventh day of March. But most importantly: he died with a satisfied mind (his own words). José Sterrenburg Sterrenburg, The Amateur Diatomist 21

We can say unequivocally, that we are all richer persons for having known Frithjof A. S. Sterrenburg. We miss you and are thankful that your work lives on.

Acknowledgments

All of Frithjof Sterrenburg’s publications are in the References section of this chapter. I would like to thank Dick Gordon and Joe Seckbach for the opportunity to write this memorial chapter and for all their help and advice along the way. I would also like to express my sincere gratitude to Herman van Dam, Wulf Herwig, Paul Hargraves, Paul Hamilton, Jackie White-Reimer (including Emilie and Laura), Hein de Wolf, and last, but not least, Michael Stringer for their heartfelt musings and wonderful stories that helped me to imbue the right kind of flavor into the memorial chapter that it deserved. While communicating with Michael Stringer in November, 2017, he let me know how grateful he was for this tribute to his dear friends, Frithjof and José, as he “‘topped up’ my Christmas pudding with brandy, they are 10 years old! One will be served with brandy custard and clotted cream.” He said his discovery of Haslea pallidum in 2006, identified for him by Frithjof, will go on the U.K. diatom register in 2018. He was rightly proud of this accomplishment and was grateful for his camaraderie with Frithjof. He died on February 23, 2018. I would like to express my extra special gratitude to José Sterrenburg for her excep- tional help and contribution of most of the personal information and personal snap- shots. We communicated often during the autumn of 2016, and without her generosity, this work would not have come to full fruition. Unfortunately, José Sterrenburg died on December 1, 2016. Although she did not get to see the completed work, I think she would have been very happy with this memorialization of Frithjof, and so, I dedicate this memorial chapter to José as well.

References

Albert the 1st of Belgium, https://en.wikipedia.org/wiki/Funeral_of_Edward_VII#/media/File: The_Nine_Sovereigns_at_Windsor_for_the_funeral_of_King_Edward_VII.jpg, accessed on 19 December 2016. Alfred Wegener Institute. (2015). FriedrichHustedt, http://www.awi.de/en/science/biosciences/ polar-biological-oceanography/main-research-focus/hustedt-diatom-study-centre/friedrich-hustedt.html. Austrian Admiral Hermann Freiherr von Spaun, https://en.wikipedia.org/wiki/Hermann_von_ Spaun#/media/File:Admiral_Hermann_Freiherr_von_Spaun_(Sport_und_Salon_1905). png, accessed on 19 December 2016. Bahls, L.L. (2015). The role of amateurs in modern diatom research, Diatom Research, 30(2), 209–210. de Wolf, H. (2016). Frithjof Sterrenburg, https://list.indiana.edu/sympa/arc/diatom-l. de Wolf, H., Sterrenburg, F.A.S. (1993). The legacy of the Dutch diatomist J. Kinker (1823–1900), Quekett Journal of Microscopy 37. de Wolf, H., Sterrenburg, F.A.S. (2003). International Survey of Diatom Collections, http:// home.planet.nl/~wolf0334/. 22 Diatoms: Fundamentals and Applications

Gordon, R., Kling, H.J., Sterrenburg, F.A.S. (2005a). A guide to the diatom literature for diatom nanotechnologists, J. Nanosci. Nanotechnol., 5(1). Gordon, R. (2011). Cosmic Embryo #1: My Erdös Number Is 2i, http://www.science20. com/ cosmic_embryo/cosmic_embryo_1_my_erd%C3March6s_number_2i. Gordon, R., Losic, D., Tiffany, M.A., Nagy, S.S., Sterrenburg, F.A. (2009). The Glass Menagerie: diatoms for novel applications in nanotechnology, Trends Biotechnol., 27(2). Gordon, R., Sterrenburg, F.A.S., Sandhage, K.H. (2005b). A Special Issue on Diatom Nanotechnology, J. Nanosci. Nanotech., 5(1). Guiry, M.D., Guiry, G.M. (2017) AlgaeBase. World-wide electronic publication, National University of Ireland, Galway, http://www.algaebase.org. Hamilton, P.B., Williams, D.M., Sterrenburg, F.A.S. (2013). Some notes on locating specimens in the microscope, Diatom Research, 28(4). Hargraves, P.E. (2016). Frithjof Sterrenburg, https://list.indiana.edu/sympa/arc/diatom-l. Höbel, P., Sterrenburg, F.A.S. (2011). UV photomicrography of diatoms, Diatom Research, 26(1–2). Jahn, R., Sterrenburg, F.A.S. (2003). Gyrosigma sinense (Ehrenberg) desikachary: typification and emended species description, Diatom Research, 18(1). Jahn, R., Sterrenburg, F.A.S., Kusber, W.-H. (2005). Typification and taxonomy of Gyrosigma fasciola (Ehrenberg) J W. Griffith et Henfrey, Diatom Research, 20(2). JStorGlobal Plants, Jacques-Joseph Brun. (1826–1908). http://plants.jstor.org/stable/10.5555/al. ap.person.bm000392757, accessed on 2 December 2016. Kemp, K., Basson, P. (2016). Never a dull moment, https://list.indiana.edu/sympa/arc/diatom-l. Kooistra, W.H.C.F., Forlani, G., Sterrenburg, F.A.S., Stefano, M.D. (2004). Molecular phy- logeny and morphology of the marine diatom Talaroneis posidoniae gen. et sp. nov. (Bacillariophyta) advocate the return of the Plagiogrammaceae to the pennate diatoms, Phycologia, 43(1). Lange-Bertalot, H., Sterrenburg, F.A.S. (2004). New Frustulia species (Bacillariophyceae) from fossil freshwater deposits in Florida, U.S.A, Nova Hedw., 78(3–4). Liu, B., Sterrenburg, F.A.S., Huang, B. (2015). Gyrosigma xiamenense sp. nov. (Bacillariophyta) from the middle intertidal zone, Xiamen Bay, southern China, Phytotaxa, 222(4). Lynk, H. (2016). A Cabinet of Curiosities: A Selection of Antique Microscope Slides from the Victorian Era c. 1830s ~ 1900, http://www.victorianmicroscopeslides.com/history.htm, accessed on 28 November 2016. Pedrotti, P.W. (2016). Thonis Philipszoon, “Antonj van Leeuwenhoek” 1632-1723 A.D, http:// www.vanleeuwenhoek.com/, accessed on 2 December 2016. Robbrecht, E. (2007). Botanic Garden Meise History, Henri Van Heurck (Antwerp 1839-1909), http://www.plantentuinmeise.be/PUBLIC/GENERAL/HISTORY/vanheurck.php. Sar, E.A., Hinz, F., Sterrenburg, F.A.S., Lavigne, A.S., Lofeudo, S., Sunesen, I. (2012). Species of Pleurosigma (Pleurosigmataceae) with lanceolate or slightly sigmoid valve outlines: analysis of type material, Diatom Research, 27(4). Sar, E.A., Sterrenburg, F.A.S., Lavigne, A.S., Sunesen, I. (2013). Diatoms from marine coastal environments of Argentina. Species of the genus Pleurosigma (Pleurosigmataceae, Boletin De La Sociedad Argentina De Botanica 48(1). Schmidt, A., Schmidt, M., Fricke, F., Heiden, H., Müller, O., Hustedt, F. (1874–1959). Atlas der Diatomaceenkunde. Aschersleben, Leipzig. Sterrenburg, F.A.S. (Year unknown). The Oslo Report 1939—Nazi Secret Weapons Forfeited, http://www.v2rocket.com/start/chapters/peene/oslo_report.html. Sterrenburg, F.A.S. (1967). Fifty Years of Jazz Records (in Dutch). Stichting IVIO, Amsterdam. Sterrenburg, The Amateur Diatomist 23

Sterrenburg, F.A.S. (1970a) Receivers. Instructions for the Advanced Amateur on the Art of Receivers, Amplifiers, Antennas, Measuring and the Like, 1st edition (in Dutch), De Muiderkring, Bussum, (2nd through 5th editions (in Dutch) published after 1970 until 1980). Sterrenburg, F.A.S. (1970b). Electronica en de Battle of Britain, Radio Bulletin, Aug, 1970, 321. Sterrenburg, F.A.S. (1973). Extreme malformation and the notion of species, Microscopy, 32. Sterrenburg, F.A.S. (1975). Guidance on Microscopy (in Dutch). Kluwer, Deventer. Sterrenburg, F.A.S. (1976). Silence around a Nobel investigation (in Dutch), Organorama, 13(1). Sterrenburg, F.A.S. (1977). Harvest the Past (in German), Organorama, 14(3), 11. Sterrenburg, F.A.S. (1978). Enhancing the visibility of diatoms, Microscopy, 33(6), 384. Sterrenburg, F.A.S. (1979). Report on medical electronics (in Dutch). Kluwer, Deventer. Sterrenburg, F.A.S. (1982). Anton van Leeuwenhoek: Pioneer or Loner (in Dutch, Organorama, 19(2). Sterrenburg, F.A.S. (1983a) IRAS - Mission Invisible, Astronomy, 11, 66. Sterrenburg, F.A.S. (1983b). A Phased Approach to Astronomy, Astronomy, 11(6), 24. Sterrenburg, F.A.S. (1983c). Computers in medicine, Organorama, 20. Sterrenburg, F.A.S. (1988). Observations on the genus Anorthoneis Grunow, Nova Hedwigia, 47(3–4), 363. Sterrenburg, F.A.S. (1989). Studies on tube-dwelling Gyrosigma populations, Diatom Research, 4(1). Sterrenburg, F.A.S. (1990a). The quest for Quekett – in search of Navicula angulata Quekett 1848, Microscopy, 468. Sterrenburg, F.A.S. (1990b). Diatom collections—legacy or legend? Diatom Research, 5(2). Sterrenburg, F.A.S. (1990c). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). A new phenomenon: co-existence of dissimilar raphe structures in populations of several species. In: Ouvrage dedié la Mémoire du Professeur Henry Germain, M. Ricard (ed.). Koeltz Scientific Books, Königstein, Germany. Sterrenburg, F.A.S. (1991a). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). The typus generis of Pleurosigma, some presumed varieties and imitative species, Botanica Marina, 34(6), 561. Sterrenburg, F.A.S. (1991b). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Light-microscopical criteria for taxonomy, Diatom Research 6(2), 367. Sterrenburg, F.A.S. (1992). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). The type of the genus Gyrosigma and other Attenuati sensu Peragallo, Diatom Research, 7(1), 137. Sterrenburg, F.A.S., de Wolf, H. (1993). The Kinker collection: preliminary investigation, Quekett Journal of Microscopy, 37, 35. Sterrenburg, F.A.S. (1993a). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). The identity of Pleurosigma obscurum, W Smith. Diatom Research, 8(2). Sterrenburg, F.A.S. (1993b). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Rules controlling raphe fissure morphogenesis in Gyrosigma, Diatom Research, 8(2). Sterrenburg, F.A.S. (1994a). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). The species of Sullivant & Wormley 1859, synonymy and differentiation from other Gyrosigma taxa, Proceedings of the Academy of Natural Sciences of Philadelphia, 145, 217. Sterrenburg, F.A.S. (1994b). Terpsinoe musica Ehrenberg (Bacillariophyceae, Centrales), with emphasis on protoplast and cell division, Netherlands Journal of Aquatic Ecology, 28(1). Sterrenburg, F.A.S. (1995a). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Gyrosigma acuminatum (Kützing) Rabenhorst, G. spenceri (Quekett) Griffith et Henfrey and G. rautenbachiae Cholnoky, Proceedings of the Academy of Natural Sciences of Philadelphia, 146, 467. 24 Diatoms: Fundamentals and Applications

Sterrenburg, F.A.S. (1995b). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Gyrosigma balticum (Ehrenberg) Rabenhorst, G. pensacolae sp. n. and simulacrum species, Botanica Marina, 38(1–6), 401. Sterrenburg, F.A.S. (1996). Cytoplasmic inheritance in diatoms, unpublished manuscript. Sterrenburg, F.A.S. (1997). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Gyrosigma kutzingii (Grunow) Cleve and G. peisonis (Grunow) Hustedt, Proceedings of the Academy of Natural Sciences of Philadelphia, 148, 157. Sterrenburg, F.A.S. (2000). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Gyrosigma reversum (Gregory) Hendey and G. naja (Meister) Sterrenburg, nov. comb, Proceedings of the Academy of Natural Sciences of Philadelphia, 150, 301. Sterrenburg, F.A.S. (2001a). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). The types of Shadbolt and related taxa, Proceedings Academy of Natural Sciences of Philadelphia, 151, 121. Sterrenburg, F.A.S. (2001b). Transfer of Surirella patrimonii Sterrenburg to the genus Petrodictyon, Diatom Research, 16(1). Sterrenburg, F.A.S. (2002a). A second look at some well-known test diatoms, http://www.mi - croscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artjul02/ fsdiatom.html. Sterrenburg, F.A.S. (2002b). Microscopy primer, http://www.microscopy-uk.org.uk/index.html? http://www.microscopy-uk.org.uk/primer/. Sterrenburg, F.A.S. (2002c). A heavy caliber microscope lamp, http://www.microscopy-uk.org. uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artoct02/fslamp.html. Sterrenburg, F.A.S. (2002d). Nulla vestigia retrorsum. The case of Pleurosigma aequatoriale Cleve, Constancea, 83(1), 14. Sterrenburg, F.A.S. (2002e). Taxonomy and the web? Diatom Research, 17(2). Sterrenburg, F.A.S. (2002f). Taxonomy – ecology – microscopy. A true triad, unpublished manuscript.. Sterrenburg, F.A.S. (2003a). Studies on the diatom genera Gyrosigma and Pleurosigma (Bacillariophyceae). Pleurosigma strigosum W. Smith and some presumptive relatives. Celebrating Norman I. Hendey’s Centennial, Micropaleontology, 49(2). Sterrenburg, F.A.S. (2003b). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Pleurosigma obscurum W. Smith revisited, Diatom Research, 18(2), 323. Sterrenburg, F.A.S. (2004). Habitat specificity of diatoms, unpublished manuscript. Sterrenburg, F.A.S. (2005a). Taxonomy and ecology – an inseparable pair, Proceedings of the California Academy of Sciences, 56, 156. Sterrenburg, F.A.S. (2005b). Crystal palaces - diatoms for engineers, J. Nanosci. Nanotechnol., 5(1). Sterrenburg, F.A.S. (2006a). Cleaning diatom samples, http://www.microscopy-uk.org.uk/mag/ indexmag.html?http://www.microscopy-uk.org.uk/mag/artaug06/fs-diatoms.html. Sterrenburg, F.A.S. (2006b). A compilation of LOMO microscope resources on Micscape. Supplemental page to Micscape article (4: Optics, correction collar maintenance), http:// www.microscopy-uk.org.uk/mag/artoct06/iw-JenaObjsup.html. Sterrenburg, F.A.S. (2007). Basionym of Gyrosigma scalprum, Diatom Research, 22(2), 495. Sterrenburg, F.A.S. (2009a). Personal recollections of WW2, https://ww2aircraft.net/forum/ search/133066/. Sterrenburg, F.A.S. (2009b). Zernike’s colour phase-contrast, http://www.microscopy-uk.org. uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artjul09/fs-phase.html. Sterrenburg, F.A.S. (2009c). LED lighting, https://list.indiana.edu/sympa/arc/diatom-l. Sterrenburg, The Amateur Diatomist 25

Sterrenburg, F.A.S. (2010a). Extreme annular illumination, http://www.microscopy-uk.org. uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artapr10/fs-pseudo-phase. html. Sterrenburg, F.A.S. (2010b). Nitzschia singalensis vs N. firthii. What’s in a diatom name? http:// www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/ artapr10/fs-nitzschia.html. Sterrenburg, F.A.S. (2011a). Pandora’s box. The diatoms of Sullivant & Wormley 1859, http:// www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/ artsep11/fs-pandora.html. Sterrenburg, F.A.S. (2011b). Advanced Techniques for visualization of diatom structures? Micros. Today 19. Sterrenburg, F.A.S. (2012a). What price optics? Micscape Magazine, 198, http://www.microscopy-uk.org.uk/mag/artapr12/fs-optics.html Sterrenburg, F.A.S. (2012b). Diatoms and microscope optics – some thoughts, http://www.mi - croscopy-uk.org.uk/mag/artjan13/fs-diatom-micro.html. Sterrenburg, F.A.S. (2012c). Objectives, https://list.indiana.edu/sympa/arc/diatom-l. Sterrenburg, F.A.S. (2012d). Guam diatoms, https://list.indiana.edu/sympa/arc/diatom-l. Sterrenburg, F.A.S. (2012e). Stidolph Diatom Atlas, https://list.indiana.edu/sympa/arc/diatom-l. Sterrenburg, F.A.S. (2013a). An imaging conundrum in diatoms, http://www.microscopy- uk. org.uk/mag/artfeb13/fs-diatom-conundrum.html. Sterrenburg, F.A.S. (2013b). Book review: An introduction to the microscopical study of diatoms. Robert B. McLaughlin. Edited by John Gustav Delly & Steve Gill, http://www.micros - copy-uk.org.uk/mag/artfeb13/fs-review.html. Sterrenburg, F.A.S. (2013c). The search of fine detail: the history of diatom imaging. In: Diatoms are Forever: Growing your Nanotechnology, R Gordon, F.A.S Sterrenburg, M.A Tiffany, S.S.Nagy & I.C Gebeshuber (eds.), unpublished manuscript. Sterrenburg, F.A.S. (2013d). The naming of the beasts: making an inventory of the realm of diatoms. In Diatoms are Forever: Growing your Nanotechnology R. Gordon, F.A.S. Sterrenburg, M.A. Tiffany, S.S. Nagy and I.C. Gebeshuber (eds.), unpublished manuscript. Sterrenburg, F.A.S. (2014a). My favourite slide, http://www.microscopy-uk.org.uk/mag/art- feb14/fs-favourite.html. Sterrenburg, F.A.S. (2014b). Haslea brittanica, https://list.indiana.edu/sympa/arc/diatom-l. Sterrenburg, F.A.S. (2014c). Haslea brittanica (follow-up message), https://list. indiana.edu/sympa/arc/diatom-l. Sterrenburg, F.A.S. (Year unknown). How to prepare diatom samples, https://www.scribd.com/ document/155323338/Clean-Diatoms, accessed on 16 December 2016. Sterrenburg, F.A.S. (2018). Science vs religion - the fallacious conflict. In: Theology and Science: Discussions about Faith and Facts, pp. 181–195. J. Seckbach & R. Gordon. World Scientific Publishing. Sterrenburg, F.A.S., de Haan, M., Herwig, W.E. (2014). A lucky break. How past vandalism favoured modern diatom research, www.microscopy-uk.org.uk/mag/artjul14/fs-lucky-break.docx. Sterrenburg, F.A.S., De Souza-Mosimann, R.M., Fernandes, L.F. (2002). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Rediscovery of a "lost" species: Gyrosigma spectabile (Grunow ex Peragallo) Cleve, Cryptogam. Algol., 23(2), 179. Sterrenburg, F.A.S., de Wolf, H. (2004). The Kinker diatom collection: discovery – exploration – exploitation. In: VII International Symposium ‘Cultural Heritage in Geosciences, Mining and Metallurgy: Libraries – Archives – Museums’: “Museums and their collections”, C.F. Winkler Prins & S.K. Donovan (eds.), pp. 253–260. 19–23 May 2003, Scripta Geologica Special Issue, Leiden, The Netherlands. 26 Diatoms: Fundamentals and Applications

Sterrenburg, F.A.S., Erftemeijer, P.L.A., Nienhuis, P.H. (1995). Diatoms as epiphytes on seagrasses in South Sulawesi (Indonesia). Comparison with growth on inert substrata, Botanica Marina, 38(1). Sterrenburg, F.A.S., Gordon, R., Tiffany, M.A., Nagy, S.S. (2007). Diatoms: living in a constructal environment. In Algae and Cyanobacteria in Extreme Environments. Series: Cellular Origin, Life in Extreme Habitats and Astrobiology. Vol. 11, J. Seckbach (ed). Dordrecht, The Netherlands: Springer. Sterrenburg, F.A.S., Hamilton, P., Williams, D. (2012). Universal coordinate method for locating light-microscope specimens, Diatom Research, 27(2). Sterrenburg, F.A.S., Meave del Castillo, M.E., Tiffany, M.A. (2003a). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Pleurosigma species in the plankton from the Pacific coast of Mexico, with the description of P. gracilitatis sp nov, Cryptogam. Algol., 24(4), 291. Sterrenburg, F.A.S., Meave del Castillo, M.E., Tiffany, M.A. (2003b). Valve morphogenesis in the diatom genus Pleurosigma W. Smith (Bacillariophyceae): an engineering paradigm. In NADS2003. E Gaiser (ed). North American Diatom Society (abstract). Sterrenburg, F.A.S., Sterrenburg, F.J.G. (1990). An outline of the marine littoral diatom bio- coenosis of the Banc-d'Arguin, Mauritania, West Africa, Botanica Marina, 33(5), 459. Sterrenburg, F.A.S., Sterrenburg, F.J.G. (1991). Studies on a widely distributed marine littoral diatom - Navicula orthoneoides Hust (Bacillariophyceae, Nova Hedwigia, 52(3–4), 411. Sterrenburg, F.A.S., Tiffany, M.A. (2004). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Two new species from the Red Sea: Gyrosigma schmidianum nov sp and Gyrosigma tubicolum nov sp, Diatom Research, 19(2). Sterrenburg, F.A.S., Tiffany, M.A., Lange, C.B. (2000). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). Species from the Salton Sea, California, USA, including Pleurosigma ambrosianum, nov sp, Proceedings of the Academy of Natural Sciences of Philadelphia, 150, 305. Sterrenburg, F.A., Tiffany, M.A., del Castillo, M.E. (2005). Valve morphogenesis in the diatom genus Pleurosigma W. Smith (Bacillariophyceae): Nature’s alternative sandwich, J. Nanosci. Nanotechnol., 5(1). Sterrenburg, F.A.S., Tiffany, M.A., Hinz, F., Herwig, W.E., Hargraves, P.E. (2015). Seven new species expand the morphological spectrum of Haslea. A comparison with Gyrosigma and Pleurosigma (Bacillariophyta), Phytotaxa, 207(2), 143. Sterrenburg, F.A.S., Toonder, M. (1972). Letters. F.A.S. Sterrenburg to Marten Toonder (1912–2005). Sterrenburg, F.A.S., Underwood, G.J.C. (1997). Studies on the genera Gyrosigma and Pleurosigma (Bacillariophyceae). The marine "Gyrosigma spenceri" records: Gyrosigma limosum Sterrenburg et Underwood nov. sp, Proceedings Academy of Natural Sciences of Philadelphia, 148, 165. Stevenson, B. (2009). William Gatrell (1864–1902), Victorian Era Microscope Specimen Mounter, http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy- uk.org.uk/mag/artjan09/bs-gatrell.html. Stevenson, B. (2013). John thomas redmayne, 1846–1880, http://microscopist.net/RedmayneJT. html. Stidolph, S.R., Sterrenburg, F.A.S., Smith, K.E.L., Kraberg, A., Stuart, R. (2012). Stidolph diatom atlas, U.S. Geological Survey Open-File Report 2012–1163, http://pubs.usgs.gov/of/2012/ 1163/. Sterrenburg, The Amateur Diatomist 27

Stringer, M.J., Sterrenburg, F.A.S. (2011). Phoenix rising: eclipse and resurrection of a diatom sanctuary, http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy- uk.org.uk/mag/artjan11/ms-fs-phoenix.html. Sunesen, I., Sterrenburg, F.A.S., Sar, E.A. (2013). Pleurosigma guarreranum, sp. nov. (Pleurosigmataceae, Bacillariophyta), from the Gulf of San Matías, Argentina, and comparison with the allied species Pleurosigma exemptum and P. obesum, European Journal of Phycology, 48(4). Swedish natural history museum, astrid cleve von euler, http://www.nrm.se/forskningochsaml ingar/vaxter/kryptogambotanik/virtuellautstallningar/astridclevevoneuler.1601.html [30 November 2016]. Taylor, J.E. (ed.) (1885). Hardwicke’s science-gossip; an illustrated medium of interchange and gossip for students and lovers of nature, Vol. XXI. Chatto and Windus, Piccadilly, London. The Quekett Microscopical Club (2016), http://www.quekett.org/, accessed on 30 November 2016. Walker, D. (2009). Enjoying a Möller 80 form diatom type-slide with a microphotograph setting, http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/ mag/artjan09/dw-moller.html. Walker, D. (2012). The diatomist John Albert Long (1863–1945*): Notes on aspects of his life and work with examples of his prepared slides, http://www.microscopy- uk.org.uk/mag/art- dec11/dw-long.html. Weaver, W., Sterrenburg, F.A.S. (1968). Science and imagination: a selection from the work of Warren Weaver (in Dutch). Wetenschappelijke Uitgeverij, Amsterdam. Werner, D. (ed.) (1977). The Biology of Diatoms, Botanical Monographs, Vol. 13. University of California Press, Berkeley and New York.