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Monday, August 28, 2017

Diatom of the Month - August 2017: Fragilariforma virescens

vivien August 28, 2017 0

post by David Williams*

Although he never wrote it down, the late Colin Patterson, one time vertebrate palaeontologist at my home from home, the Natural History Museum, London, often said that when confronted with any particular biological specimen, three questions should come into the minds of systematists: What is it? What is it related to? Where does it live?

For me, the first is often a struggle, as wading through books of images can be a tad soul-destroying, especially if the images never quite match what’s in front of you. Start with something easy – that’s what Frank Round told me, a long while ago now. Easy? There’s a lovely book by Archie Carr, A Naturalist in Florida, A Celebration of Eden (1994). In it there’s a key to the fishes of Alachua County, Florida, first published in 1941. One instruction reads: “Not as above; fins with dangerous spines; catfish-like—in fact, a catfish”, with a footnote: “Any damned fool knows a catfish”. So, Frank suggested Fragilaria virescens1 because, well you’ve guessed already: “Any damned fool knows Fragilaria virescens.”

Fig. 1. BM 81303: Tunbridge Wells, syntype of Fragilaria virescens. a) BM 81303: Tunbridge Wells, LM. b) Tunbridge Wells, SEM: Internal valve. c) Tunbridge Wells, SEM: Girdle of whole frustule. d) Tunbridge Wells, SEM: Valves connected with spines. e) From Ralfs, J. 1843, Annals and Magazine of Natural History 12: fig. 6.

I was lucky enough to have access in the Natural History Museum, London (NHM) diatom collections to more material supposedly of this species than I could deal with in a reasonable amount of time, upwards of 500 plus slides, most from localities in the UK, but many more from Europe, some from the USA, others from Australia. At that time, I didn’t look at nearly enough specimens, but it was obvious to me after a short while that, no, “Any damned fool would not know Fragilaria virescens”.

Fig. 2. River Stort in Southeast England (17^thSept. 2011, https://en.wikipedia.org/wiki/River_Stort).

Fragilaria virescens is normally considered a common, cosmopolitan species, found often, found everywhere. But after looking at just a few specimens from outside the UK, I became aware that this name had become attached to anything that vaguely looked like its potted description. Here’s one from an online key: “Valves with linear or slightly convex margins, narrowing to rostrate or cuneate apices”. I’m responsible for another, perhaps even simpler, description. I guess it’s best to look at the pictures. But looking at the specimens (rather than pictures) in the NHM, it became clear I wasn’t dealing with one species but a quite a number, some already with names, others in need of one. I also had access to Ralf’s original specimens, which helps. So the “What is it?” question was hard to answer straight away but I came to the conclusion, not yet fully documented I should add, that Fragilaria virescensis anything but a cosmopolitan species – from the material I have had access to, it occurs only in the UK, and some parts of Europe – a different species extends upwards into Lapland, for example, and most of the specimens from Australia, along with others from further far-flung territories, were simple misidentifications. So, the answer to “Where does it live?” emerged from investigating “What is it?”.

Now we have a much better understanding of the species, with its rectangular frustules, the linear colonies it forms, the valve being lanceolate to linear with tapering, rostrate to capitate apices. We now know that it has a fairly faint central sternum, and that the mantle margin has siliceous plaques. The linear colonies are a result of spines on the valve face/mantle border, which are simple interlocking projections. There are apical pore fields at both poles and one polar rimoportula. Its girdle (cingulum) has 4 to 6 open bands, and the plastids are numerous small discs; and we also know a little about its ‘development’, from auxospore to vegetative valve. From this constellation of characters, some define the species, others the genus; the thin barely visible sternum, a character of the genus – but it is not a Fragilaria (whatever that might be). So the answer to the question “What is it related to?” is: other members of the genus Fragilariforma, having this barely visible sternum. Since Ralfs described it in 1843, Fragilaria virescenshas been sub-divided a number of times, yielding some 80+ names of varieties and forms. Resolution of these names (“What are they?”) might be achieved to a certain degree by examining the type specimens of each, should they still be available. But a comparative collection, like that in the NHM, is a far better way, assessing numerous specimens, from many geographical regions.

Taking an apparently well-known diatom (“Any damned fool knows Fragilaria virescens”) and investigating it closely tells us that we actually didn’t know what it was, what it was related to, nor where it lived? I think we have a better idea now. Let me finish with a few more wise words from Colin Patterson, and these are published: “ […] you never know enough about anything, and if for a few months or years you should ever believe that you do, you are either past it or in for a surprise…Yesterday’s secure knowledge is tomorrow’s laughing matter”.

*Diatom systematist-taxonomist at the Natural History Museum, London, UK

1. The genus Fragilariforma typified by F. virescens was described by Williams and Round (1988).

Patterson, C. (2011) Adventures in the fish trade. Zootaxa 2946: 118–136. [edited and with an introduction by D. M. Williams and A. C. Gill]

Williams, D.M. (2001) Comments on the structure of ‘post-auxospore’ valves of Fragilariforma virescens. In: Lange–Bertalot Festschrift, Studies on diatoms (Jahn, R., Kociolek, J.P., Witkowski, A. & Compe`re, P., editors), 103–117. A.R.G. Gantner, Germany.
Williams, D.M. and Round, F.E. (1988). Fragilariforma, nom. nov., a new generic name for Neofragilaria Williams & Round. Diatom Research 3: 265-267.

Tags # Algae # Diatoms # Systematics Continue Reading

Thursday, March 16, 2017

Diatom of the month: March 2017 - Mastogloia pseudosmithii

vivien March 16, 2017 0

by Sylvia Lee, FIU & Periphyton lab alumna

Did you know that March 19 is Taxonomist Appreciation Day?

Fig. 1. Cartoon on what taxonomy is. Image credit: BuzzHootRoor from https://smallpondscience.com/2014/03/19/today-is-taxonomist-appreciation-day/

Taxonomy is the study of organisms and their classification (or in more witty/punny terms in the image above, “how you phylum”). Recognizing and putting names to organisms may come easy to some natural-born naturalists, but taxonomy can be a challenging task requiring specialized knowledge. This is especially true for groups with many species, such as diatoms. Species identification may not seem like an important skill, but it can be thought of as an essential part of “ecoliteracy.” It is difficult to care about something if you do not know its name, and it can even become extinct without your knowledge.

As part of my Ph.D. research, I was able to do an in depth study of some of the diatoms in the Everglades, and described them as new species. Two of the species are in the genus Mastogloia. Mastogloia calcarea is very abundant, while a similar diatom, Mastogloia pseudosmithii, is quite rare. Rare diatoms are difficult to study, because one image of a single diatom is not enough to understand how the cell morphology of that species changes through the life cycle of its population. To adequately describe the species, a researcher would have to wait until enough specimens could be found or happen to obtain a sample with a larger population of the rare diatom. Fortunately, I was able to find enough specimens of the rare diatom because my advisor, Evelyn Gaiser, has been collecting diatoms from all over the Greater Everglades as part of a large monitoring and research program since 2005. Even in samples with a “good” population, M. pseudosmithii was only 1% or less of the total diatom abundance. I found this species in samples usually from brackish areas near the coastal marshes of the Everglades, which have higher salt and phosphorus levels than areas in the interior of the Everglades.

Fig. 2. A size diminution series of Mastogloia pseudosmithii (Source: https://westerndiatoms.colorado.edu/taxa/species/mastogloia_pseudosmithii).

You can see in the collection of specimens in Fig. 2 that, as M. pseudosmithii becomes smaller with cell division, the ends of the valve changes from rostrate (pulled out like a nose) to rounded. You can also notice that the second and last images are actually part of the same cell as the specimen to their immediate left. The structures indicated by the arrows in Fig. 2 are the partectal rings, a special girdle band that all species in the genus Mastogloia possess. The partectaare chambers inside the diatom cell that are associated with the production of mucilage, which may protect the cell from drying out.

Fig. 3. Live cell of Mastogloia calcarea with mucilage strands originating from partecta.

Diatoms are sensitive indicators of environmental change, but using these or other algae as indicators is difficult if they are not identified correctly. To obtain accurate signals from diatoms about environmental conditions, researchers strive to put correct names (or at least, consistent names) to diatom species. Diatoms of the United Statesis a reference on North American diatoms (including Canadian records) with the goal of improving the use of diatoms in biomonitoring programs in the US.

Learning to identify diatoms can be a fun challenge when combined with the field station experience! This summer, I am co-instructing the college/graduate level Ecology and Systematics of Diatoms, as well as the high school level College Prep Diatoms at Iowa Lakeside Lab. The courses provide an immersive setting, excellent microscope station for each student, and fun sample collection field trips to local lakes, streams, and wetlands. Spread the word!

Fig. 4a. College Prep Diatoms students sampling river diatoms.

Fig. 4b. Sharing diatom knowledge at College Prep Diatoms.

Tags # Diatoms # Taxonomy Continue Reading

Monday, November 21, 2016

Diatom of the Month: November 2016 - Medlinella amphoroidea

vivien November 21, 2016 0

by Tom Frankovich*

I would like to introduce you all to Medlinella amphoroidea, a new taxon that was observed on loggerhead sea turtles, as the November diatom-of-the month. But, before I get to discussing the morphology and ecology of this new genus and species, I will tell you all a personal story of serendipity and professional relationships. It was early 2013, and I had received an email from Dr. Brian Stacy, a marine veterinarian at the National Marine Fisheries Service, and a friend from when we worked together investigating parasites in marine gastropods. Brian told me that his wife, Dr. Nicole Stacy, also a marine veterinarian, was interested in identifying organisms that she suspected were diatoms that were on skin smear slides and contaminants in blood, urine and teat fluid samples from Florida sea turtles and manatees.

Fig. 1. Dr. Brian Stacy performing a necropsy on a loggerhead turtle, Caretta caretta (Photo courtesy Brian Stacy, unknown photographer).

I subsequently found out that pathologists were frequently misidentifying diatoms and reporting them as “parasite eggs”! Obviously, it is important to distinguish likely benign diatoms from harmful parasites, and so I told Nicole that I would gladly examine photomicrographs of her samples and that it would be no problem to identify these suspected diatoms using descriptions of the local diatom flora. After all, the sea turtle and manatees probably picked up these diatoms from the surrounding environments, right? Wrong! Nicole had immediately sent me images of various samples collected from manatees and sea turtles. The samples were uncleaned and were stained with a dye to reveal cytologicalcharacteristics of interest to a pathologist. These are not the best samples for a diatomist to examine, so most diatoms could only be identified in the broadest of terms (e.g., radial centric, raphid pennate). I asked Nicole if she had material to clean, mount, and examine using standard diatom methodologies. She told me that she only receives prepared slides from the field. End of story? Not yet. About a week had passed when an Everglades Park Ranger knocked on my office door at our Florida Bay research station and asked if I could help him move a dead manatee that was reported in the bay. I suppose most people would say no to moving a dead smelly manatee, but for me this was a gift from the heavens. I finally got my hands on an adequate sample for my planned examinations, but I was in for a rapid deflation of my presumed diatom identification abilities, and for a big surprise.

Fig. 2. A manatee captured for a health assessment (left) and a close –up of the manatee skin (right) with a film of epibionts, including diatoms (Photos by Tom Frankovich).

If you are a fellow diatomist in the blogosphere, you may agree with me that the most exciting part of our work is looking at a sample for the first time. Like a child waiting for Christmas morning, I anxiously awaited for the cleaning and rinsing of the new diatom sample to be complete. What I saw through the microscope was an assemblage unlike anything I had seen previously. First, instead of seeing a very diverse collection of tens of diatom taxa, I saw an assemblage comprised of very few taxa. 95% of the valves appeared to belong to 2 or 3 taxa. Second, I could not identify the dominant taxa, not even to a genus! Even after scouring 58 reference books, and a file cabinet of reprints of benthicdiatom taxonomy, I was still lost! Time to call for help. I emailed photomicrographs to Dr. Mike Sullivan, the former 20+ year editor of Diatom Research, and the person who first sparked my interest in diatoms. I told him of my challenges. He immediately replied back saying that he was not surprised that I was unable to identify the genus in those references. He indicated that the diatoms belonged to one of two genera – Tursiocolaor Epiphalaina. These genera were exclusively epizoic, and up until 2012, were known only from the skin of whales and therefore, we were very unlikely to find these in benthic diatom literature.

The small number of species within these genera and the relatively recent descriptions with SEM images of these taxa made it relatively easy to compare our specimens against the described species and determine if they were new to science. Subsequent SEM analyses revealed that there were 3 new species of Tursiocola in our sample(check out last year’s blog on T. ziemanii). This discovery of a new diatom world on the skin of a dead manatee, and opportunistically working with marine veterinarians, have opened up a whole bunch of new opportunities and investigations and brings our blog conversation to the present diatom-of-the-month Medlinella amphoroidea. This diatom was described from sea turtles captured in Florida Bay. After seeing the new diatoms on the manatee, we wanted to know if the same or similar diatoms occurred on sea turtles as we suspected from some of Nicole’s cytologic specimens. We found a similar low diversity species assemblage with some of the same genera; the species composition was different, but we also described another new Tursiocola species (T. denysii) along with M. amphoroidea.

So here is the profile of Medlinella amphoroidea. This species is very abundant on the neck of loggerhead sea turtles, accounting for up to 50% of diatom valves observed in skin samples. It is a very small diatom, only 7-13 microns (µm) in length. Using light microscopy, its valves are likely to be misidentified as a Catenula or small Amphora species because of its shape and eccentric raphe-sternum, but careful focusing through valves with attached valvocopulae¹ or through intact frustules will reveal septa² present on the girdle bands, differentiating Medlinellafrom these other genera. M. amphoroideais most similar to species in the epizoic genera Tripterion, Chelonicola, and Poulinea and other “marine gomphonemoid (Gomphonema-like) diatoms”. The amphoroid shape of the valves and the unique volate pore occlusions³of the areolae distinguish Medlinellafrom these genera. The genus name honors Dr. Linda Medlin in recognition of her work describing marine gomphonemoid diatoms.

Fig. 3. Microscope images of Medlinella amphoroidea; a) girdle view; b), c), d) valve / face view (Photos: a), c), d) Matt Ashworth; b) Frankovich et al., 2016; scale bar = 2 μm).

I hope my story will encourage some of you out there to share your passion for diatoms with other scientists and to pursue any opportunities that may present themselves. The seeds of future exciting discoveries start with a conversation. Thanks again Luca and readers, for our continuing conversations on the diatom-of-the-month blog.

* Research Faculty at the Southeast Environmental Research Center, Florida International University.

1. Valvocopulae: the first girdle bands that attach to the valve

2. Septa: inward projections of silica that partially separate areas within the cell.

3. Volate pore occlusions: flap-like outgrowths from the sides of the pores with narrow points of attachment and irregular branching, as opposed to cribrate or rotate occlusions.

Tags # Algae # Diatoms # Manatees Continue Reading

Sunday, October 30, 2016

Diatom of the month – October 2016: Brachysira brebissonii

vivien October 30, 2016 0

by Charlotte Briddon*

Brachysira brebissonii (formerly known as Anomoeoneis brachysira) is a freshwater, benthic diatom. It is widespread in lakes and rivers from the Arctic to tropical and temperate regions. In 1981 the Anomoeoneis and Brachysira genera were separated, as two sets of longitudinal ribswere observed in Brachysira specimens, one surrounding the valve (marginally at the junction of valve face and mantle), and another composed of two straight ribs, discontinuous in the central area that border the raphe, which the genus Anomoeoneis lacks.

Brachysira brebissonii (photo taken by Paul Hamilton at Egg Harbour Lakes, New Jersey, United States; see Hamilton, 2010).

Case study of Tasik Chini
I have chosen this diatom because it has played a meaningful role in aiding our understanding of past and current environmental conditions/water quality at Tasik Chini, (a flood pulse wetland in Malaysia). Tasik Chini, a natural freshwater flood pulse wetland, consists of a series of 12 interconnected basins in central Pahang and is hugely important from a conservation viewpoint in that it is has been awarded protected status by UNESCO's Man and Biosphere Programme. This program’s goals are to establish a scientific basis for the improvement of relations between people and their environments. It uses a combination of sciences to improve human livelihoods and to safeguard natural and managed ecosystems. Understanding how this lake has been impacted by an array of anthropogenic activities such as deforestation, mining and agriculture over the last 100 years or so is crucial in formulating conservation efforts to retain ecological integrity at this site.

Oil Palm Plantation from the Tasik Chini lake catchment (photo: C. Briddon).

Brachysira brebissonii is acidophilous, it has an affinity for environments with pH < 7, with an optima of ~ 5.9 (Stevenson et al. 1991). Changes in abundance of this diatom in a sediment core can, therefore indicate pH variations in the lake over time. An abundance increase of this diatom over time may be due the onset of lake acidification from either natural (e.g. catchment geology or vegetation) and/or anthropogenic influences (such as atmospheric deposition of sulphates) (Wolfe and Kling, 2000).

Nucifera Nelumbo, the famous water louts from Tasik Chini (photo: C. Briddon).

Analyzing a 90 cm sediment core taken from Basin 12 at Tasik Chini, we found this diatom to be most abundant in younger sediments deposited when anthropogenic impacts were largest at this site. The increasing relative abundance of Brachysira brebissonii provides important evidence of acidification and eutrophication of Tasik Chini over the latter half of the 20^th century, most likely caused by increases in human activities such as mining, agriculture (palm oil and rubber plantations), hydrological manipulation and deforestation.

In addition, Brachysira brebissonii was found to be the most abundant diatom (~36 % maximum) in contemporary diatom habitats sampled in April 2016. It was observed in high numbers on leaves and stem of the iconic water lotus (Nelumbo nucifera), a key species for eco-tourism at Tasik Chini). Thus, this diatom may also be an indicator species for the presence of this floating-leaved plant.

*Charlotte is a first year Ph.D. student at the University of Nottingham, under Suzanne McGowan's supervision. She conducted her work on Brachysira brebissonii during her MRes studies at Keele University during a placement at the University of Nottingham Malaysia Campus.

References

Hamilton, P. (2010). Brachysira brebissonii. In Diatoms of the United States. Retrieved October 18, 2016, from http://westerndiatoms.colorado.edu/taxa/species/brachysira_brebissonii

Stevenson, R. J., Peterson, C.G., Kirschtel, D.B., King, C.C., Tuchman, N.C. (1991) Density-dependent growth, ecological strategies, and effects of nutrients and shading on benthic diatom succession in streams. Journal of Phycology 27, 59–69

Wolfe, A.P., Kling, H.J. (2001). A consideration of some North American soft-water Brachysira Taxa and description of Barctoborealis sp. nov. Lange-Bertalot –Festschrift

Tags # Algae # Diatoms # Taxonomy Continue Reading

Wednesday, July 20, 2016

Diatom of the month – July 2016: Nitzschia amphibia

vivien July 20, 2016 0

by Luca Marazzi*

Nitzschia amphibia belongs to the nitzschioid group: its valves are symmetrical to both apical and transapical axes, and taper to bluntly rounded apices; the raphe is well developed near the valve margin, and enclosed within a canal¹. The original description was made by Albert Grunow in 1852, when the US President was Millard Fillmore, the last one not to be affiliated with either the Democratic or Republican party. This is how ‘old’ are some of the species names of algae and other organisms that persist to this day, while new species are continuously described at an increasing rate. Grunow was one of the eight most ‘profilic’ algal taxonomists who described more than 1,000 species during their career, the others being Kützing, Gottfried, Hustedt, Agardh, Harvey, who worked in the 1800s, and Lange-Bertalot (the only one still alive and active) and Skvortsov in the 1900s².

Fig. 1. a) Nitzschia amphibia in valve view and girdle view (scalebar = 10 µm) (photos by Pat Kociolek); b) Florida Coastal Everglades LTER program diatom image database.

While the number of algal taxa discovered per taxonomist is increasing, the number of taxonomists is going down (Fig. 2), not a good sign on the already difficult road to a deeper understanding of thousands of species of algae and their ecology. New molecular and genetic techniques imply that doubtful / uncertain species (from a traditional taxonomy viewpoint) are increasingly called ‘clade’ (a grouping that includes a common ancestor and all the descendants, living and extinct, of that ancestor), ‘specimens’ (a single example of a collected alga) or ‘strains’ (a genetic variant or subtype). This creates the further challenge of integrating historical collections into such modern laboratory research²to provide continuity, whilst improving the accuracy of such discoveries.

Fig. 2. The number of algal species described by each taxonomist keeps increasing while the number of specialized taxonomists is decreasing (source: Clerk et al., 2013).

So the algal taxonomy road, and this blog post, do lead somewhere²…here let’s zoom back on this month’s diatom. Nitzschia amphibia is a glass-encased moderately motile alga that likes muddy aquatic habitats, and is an indicator of phosphorus enrichment (>800 µg g^-1in Everglades periphyton), alongside other diatoms such as Gomphonema parvulum, Eunotia incisa, Rhopalodia gibba, and the green alga Mougeotia(which has a carbohydrate cell wall, not a silica one like diatoms)³. In general, Nitzschia species not only glide horizontally in epipelic habitats (mud), but also vertically through the substrates, and, together with stalk-forming diatoms like G. parvulum support the formation of complex three dimensional biofilms. Such 3D communities abound in the Everglades (Fig. 2), and other freshwater ecosystems, for example in Lake Sakadaš, in theCroatian part of the Danubian floodplain⁴, and along the River Team in Northern England, where Martyn Kelly studies, but also draws (and tells stories about) how various species attach to plants and other algae (Fig. 3). His work is another example of the successful and important marriage between science and art that we are experiencing!

Fig. 3. A periphyton sampling site in Shark River Slough (SRS-1d) where Nitzschia amphibia can be found (photo: Franco Tobias, April 2008).

Fig. 4. Three dimensional biofilms from the River Team (Northern England) as depicted by British diatom scholar and artist Martyn Kelly; river bed with the filamentous green alga Cladophora and numerous attached diatoms such as Craticula, Navicula, and Nitzschia (circled in red). Source: Kelly (2011) “Of microscopes and monsters - Journeys through the hidden world of Britain’s freshwaters” - http://www.martynkelly.co.uk/).

* Postdoctoral Associate in Dr. Evelyn Gaiser's lab at Florida International University.

1. Source: http://westerndiatoms.colorado.edu/taxa/morphology/nitzschioid

2. De Clerck O.D., Guiry M.D., Leliaert F., Samyn Y., Verbruggen H. (2013) Algal taxonomy: a road to nowhere?

Journal of Phycology, 49: 215–225.

3. Gaiser E.E., McCormick P.V., Hagerthey S.E. & Gottlieb A.D. (2011) Landscape Patterns of Periphyton in the

Florida Everglades, Critical Reviews in Environmental Science and Technology, 41(S1), 92–120.

4. Žuna Pfeiffer T., Mihaljević M., Špoljarić D., Stević F. & Plenković-Moraj A. (2013) The disturbance-driven

changes of periphytic algal communities in a Danubian floodplain lake. Knowledge and Management of

Aquatic Ecosystems (2015) 416, 02.

Tags # Algae # Diatoms # Taxonomy Continue Reading

Wednesday, June 15, 2016

Diatom of the month – June 2016: Eunotia cisalpina

vivien June 15, 2016 0

by Luca Marazzi*

This month’s diatom comes from quite far, some 5,000 miles or 8,100 km North-East of Florida: Northern Italy. Its name is Eunotia cisalpina (on this side of the Alps, the southern side), and it was described a few years ago¹by Marco Cantonati, the Science Museum of Trento’s (MUSE) Head Limnologist and Phycologist whom I am visiting this week. We are at the foot of the famous and wonderful Dolomites mountains, one of over 50 UNESCO World Heritage sites in Italy, comprising some of the highest limestone walls in the world. North-west from here, small mountain lakes, springs, and mire pools dot the landscape of the Adamello and Cevedale mountain ranges; their waters have lower mineral content than the calcareous Dolomites due to the prevalence of siliceous rocks, such as granites. These oligotrophic, acidic, low conductivity habitats are perfect for E. cisalpina (and for E. fallacoides and E. insubrica, other new taxa to science described in the same 2011 paper¹). The authors of the discovery can now say that, some 10 years earlier, they had ‘confused’ Eunotia cisalpinawith E. islandica¹. This is common in taxonomy, as observing more specimens and features or using new methods, allows investigators to identify and thus name new taxa in a time consuming yet exciting scientific process.

Left)Mountain lake in the Adamello, where rocks are mostly siliceous, and waters have very low alkalinity. This lake, as several others on the eastern slopes of the Presanella subgroup of the Adamello mountain range, beautifully faces the Brenta Mountain group (Western Dolomites); in this image, the contrast between different lithological substrata is shown, a characteristic of the Adamello-Brenta Nature Park. Right) further east, the Dolomites are made of dolomite (CaMg(CO₃)₂or calcium magnesium carbonate) and extend over 1,000 km² in the Lombardia, Veneto, Trentino Alto Adige, and Friuli Venezia-Giulia regions. Source: http://whc.unesco.org/.

Diatoms of the genus Eunotia are symmetrical to the transapical axis, but asymmetrical to the apical axis, and have a short raphe allowing them a limited movement (http://westerndiatoms.colorado.edu/). An estimated 600 Eunotia species exist globally, many of which are / can be used to monitor freshwater acidification caused by industrialization, due to their preference for low pH waters³. A number of diatoms living in these pristine mountain habitats are included in the Red List², as these environments are sensitive to airborne acid deposition, and other pollution by metals. In particular Al, Ba, and Mn react with acid compounds, and seem to cause teratological mutations in diatom cells (congenital abnormalities)⁴, thus threatening important primary producers in remote lakes and wetlands.

Some of the shapes and sizes of Eunotia cisalpina. Source: Cantonati et al.(2011)¹. Scale bar: 10 µm.

Another very interesting ecological characteristic of some Eunotiaspecies is their apparent ability to resist desiccation by forming vegetative cells that survive heating¹. This brings us back to the global warming challenge and its associated risks of more frequent and/or more intense droughts in a variety of freshwater ecosystems, from the 3,000 m alpine lakes in Europe to the Florida Everglades and other large wetlands in every continent. Diatoms and other algae, are indeed helping us to figure out how anthropogenic, including climatic changes, are profoundly modifying natural habitats. However, the scientific community needs much increased and sustained funding provision from public and private institutions to better and faster improve our ecological knowledge of such dangerous environmental changes. This is especially true for the detailed taxonomic and molecular work required to discover new species, know their biology and ecology, and use them as indicators of environmental conditions to advise decision makers on what to do, and not to do, to preserve and sustainably ‘manage’ ecosystems.

* Postdoctoral Associate in Dr. Evelyn Gaiser's lab at Florida International University.

1. Cantonati M. & Lange-Bertalot, H. (2011). Diatom monitors of close-to-pristine, very low alkalinity habitats: three new Eunotiaspecies from springs in Nature Parks of the south-eastern Alps. Journal of Limnology, 70, 209-221.

2. Lange-Bertalot H. & D. Metzeltin (1996). Indicators of Oligotrophy. In: H. Lange-Bertalot (Ed.), Iconographia Diatomologica. Koeltz, Koenigstein, 1-390.

3. Lange-Bertalot H., Witkowski A. & Bąk M. (2011). Eunotia and some related genera. In: H. Lange-Bertalot (Ed.), Diatoms of Europe. A.R.G. Gantner Verlag, K.G., Ruggell, 6: 1-747.

4. Furey P.C., Lowe R.L. & Johansen J.R. (2009). Teratology in Eunotia taxa in the Great Smoky Mountains National Park and description of Eunotia macroglossa sp. nov. Diatom Research, 24, 273-290.

Tags # Algae # Diatoms # Mountain Lakes Continue Reading