simpple025: Algae

Showing posts with label Algae. Show all posts

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

Monday, July 24, 2017

Diatom of the Month - July 2017: New discoveries await!

vivien July 24, 2017 0

In the last year and a half, ten different authors have talked about 19 diatom species from 19 different genera in our “Diatom of the Month” blog series (11 biraphid, 2 araphid, 2 centric, 1 epithemioid, 1 eunotioid, 1 monoraphid, and 1 nitzschioid), and we got to know about some fantastic 2D and 3D diatom art. We reached thousands of people online via social media (see image below), thus raising awareness about these beautiful and extremely useful primary producers and environmental indicators.

We importantly relied on the wonderful “Diatoms of the United States” resource for reference and inspiration, which has so far produced taxon pages for 155 genera (25 are underway), and 851 species (202 are underway)! This was made possible over the years by more than 110 taxon contributors, an effort led by Marina Potapova, Sarah Spaulding, and Mark Edlund and kept under scrutiny by the review board members. The DOTUS Facebook page provides regular updates and features as well as news about course like the Summer Field Courses in Iowa on ecology and systematics of diatoms, ecology and systematics of algae, ecology of algal blooms, and even an introductory course for high school students!

New discoveries on the world of diatoms keep taking place. For example, the “Diatoms from remote places” project led by Loren Bahls, curator of the Montana Diatom Collectionand funded by Adventurers and Scientists for Conservation has found 67 new and rare diatom taxa (belonging to over 20 genera).Volunteer collections comprise specimens from all of western North America’s major biomes —arctic tundra, boreal forest, temperate rainforest, deserts, alpine tundra, montane forest, and steppe—and all the samples are from remote, relatively unspoiled habitats. This initiative allowed to reveal that the central Cascades in Oregon is a diatom species diversity hotspot. And surely cool new discoveries about diatoms in lakes, rivers, streams, wetlands everywhere will emerge at the upcoming North American Diatom Symposium (Sep 27 - Oct 1) at the Stone Laboratory on Gibraltar Island in Lake Eerie!

The ~20,000 diatom taxa discovered / described by humans is only the tip of the diatom biodiversity iceberg! Believe it or not there may be up to 2-10 million species of diatom on Earth, with scientists still trying to better define "what a diatom species is" (Guiry, 2012). So many new species are yet to be discovered that citizen scientists, volunteers, and aficionados are very much needed to collect, preserve and study them, in the Everglades (see periphyton mats in the image below) and anywhere else where there is a little bit of water or moisture for some diatoms (and/or other algae) to survive.

Stay tuned and do not forget that these invisible organisms ‘paved the way’ for many other species on this planet (and, who knows, maybe beyond…)!

Guiry, M.D. (2012). How many species of algae are there? Journal of phycology 48: 1057-1063.

Spaulding, S.A., Lubinski, D.J. and Potapova, M. (2010). Diatoms of the United States. http://westerndiatoms.colorado.edu. Accessed on 24 July, 2017.

Tags # Algae # Conferences # Diatoms Continue Reading

Thursday, June 22, 2017

Diatom of the Month – June 2017: Fragilaria synegrotesca

vivien June 22, 2017 0

by Nick Schulte*

I think Fragilaria synegrotesca is a cute diatom. Although long and lanky (nothing wrong with that!), F. synegrotesca has an adorable, sometimes very slight, potbelly (Fig. 1).

Fig. 1. a) Live frustules in a rosette colony (http://fcelter.fiu.edu/data/database/diatom/index.htm?species=3568)

b) Fragilaria synegrotesca in valve view (Schulte 2014).

Now, some boring diatomist (e.g., me) might describe that little bump in the middle right as “a unilaterally expanded, hyaline central margin” and that’s accurate enough. But I also like to think of it as F. synegrotesca’s belly pooch. It brings to my mind the potbellies of seahorses, pigs, puppies and toddlers, and it seems very boop-able.

But let’s move past the physical attributes of this diatom, as the allure of this species is in its “actions”. Fragilaria synegrotesca has so far only been reported from karstic wetlands of the Caribbean and is most well-known from the Florida Everglades. In the Everglades, F. synegrotesca is nearly ubiquitous (Fig. 2), and it’s one of the five most abundant species in the calcareous periphyton mats in the nutrient-poor freshwater marshes (Gaiser et al. 2006).

Fig. 2. Relative abundance (%) of F. synegrotesca across the Everglades (data from the Comprehensive Everglades Restoration Plan Monitoring and Assessment Plan).

A major issue in Everglades restoration is getting the amounts of water and nutrients that enter this wetland right. Every winter/spring (the “dry season”), sloughs and inundated prairies often dry down. This happens more often and more severely now than in the “natural” pre-drainage state in many sites. But water managers (e.g., the South Florida Water Management District) can’t just send water through the marshes unless it’s “clean” (e.g., low in phosphorus), so as not to harm organisms that are adapted to this wetland’s low nutrient waters. So, Everglades restoration is between a bit of a rock and a hard place: we need to deliver more water to help the organisms that need high water (and can’t handle severe dry-down – e.g., many fish), but not at the expense of the organisms that can’t handle high nutrients in the water (e.g., some grasses and sedges).

Fragilaria synegrotesca is one of those organisms that doesn’t like to be dried out (Gottlieb et al. 2005, Lee et al. 2013), and its preference for being wet makes it a potentially “reliable indicator of the absence of periodic drying” in the ‘Glades (Gaiser et al. 2011). We can therefore use the abundance of this species (alongside other indicators) to measure the effects on biodiversity that potential reduced water flow might have upon different locations. This information can then inform decisions on how much water should be sent where and when – all key questions in Everglades restoration.

Unlike its freshwater-loving, high nutrient-hating buddies Brachysira microcephala, Encyonema evergladianum, and Mastogloia calcarea (let’s call them the “Fresh Diatoms of Belle Glades,” or “Freshies” for short), F. synegrotesca can also live comfortably in moderate phosphorus (P) concentrations and slightly salty water (“oligohaline”).

So, we can think of F. synegrotesca as that close friend that is too cool for us sometimes and likes to hang out with hipper, more indulgent folks.

And if this diatom is found in relatively high abundance in the absence of the Freshies, we know that area might be getting a little too phosphorus-y and/or salty than is normal. Now, there are some regions of the Everglades where finding F. synegrotescain enriched or salty places is normal, but by now we know which places are “normally” enriched/salty and which are not. So, if we see this species hanging out with the Salty Boys or the +P Posse in the good side of town (i.e., a normally freshwater, low nutrient place), we know something’s about to go down. In this way, I guess F. synegrotesca is also like that sweet suburban kid who gets caught up in the wrong crowd, and we’d rather see it back at home with the Freshies.

But here is some science to back up these potentially confusing analogies. In the Everglades, the total phosphorus (TP) optimum of F. synegrotesca is 270±202 µg P g^-1periphtyon (Gaiser et al. 2006), and this species has been designated as an indicator of high TP (La Hée and Gaiser 2012). Compare that to oligotrophic, freshwater indicators (B. microcephala, E. evergladianum, and M. calcarea) that have a mean TP optimum of 159 µg g^-1 (Gaiser et al. 2006). Our diatom of the month also has a salinity optimum and tolerance of 5±7.3 ppt (parts per thousand) – slightly higher than the Freshies (mean optimum across those 3 taxa = 2.9 ppt) (Wachnicka et al. 2010). Importantly, though, F. synegrotesca is generally not an indicator of a nutrient or salinity impacted site. Rather, its presence might indicate that a place is in limbo: it’s not too far gone, but it’s worse than we would expect if everything was OK. And F. synegrotesca alone doesn’t tell us much: rather, we have to look at the entire community of diatoms (and other algae and cyanobacteria) in order to make sense of the ecological impacts of modified nutrient levels and hydrology. So we use an “indicator community” analysis approach rather than “indicator species.”

As an example, in the Comprehensive Everglades Restoration Plan (CERP) Monitoring and Assessment Program (MAP) scientists from the Gaiser and Trexler labs report on how ~150 sites across the Everglades (and their animals, plants, and algae in periphyton mats) are affected by nutrient enrichment. To do this, one of the best measurements of site alteration is a combined periphyton TP-diatom community composition metric (RECOVER 2014, see pages 6-33 – 6-39). They use a “stoplight” reporting technique: green means baseline (“success”) conditions (TP < 200 µg / g), yellow means “caution” (TP = 200-250 µg / g), and red means “altered” (TP > 250 µg / g) (Fig. 3). Fragilaria synegrotesca is one of the diatoms that can contribute to a “caution” designation if it’s found away from the Freshies.

Fig. 3. Condition status of sampling sites from 2011 using a periphtyon TP-diatom community metric (from RECOVER 2014; Fig. 6-17).

So, while F. synegrotesca may seem a bit pudgy, it is a mover and shaker of the diatom scene in the Everglades. In the Everglades, there is the potential for more widespread dry-downs, human-caused phosphorus enrichment in the Everglades interior (particularly in the northern Everglades and near canals), and for sea-level rise in the southern Everglades (pushing saltier, nutrient-enriched water into the freshwater inland regions). Fragilaria synegrotesca and its associated community are great tools to understand how such disturbances are affecting the nature of this wonderful and important wetland. The ongoing diligent scientific monitoring and analysis (e.g., by CERP MAP and the Florida Coastal Everglades Long Term Ecological Research program) allow us to understand things like a potbellied diatom that inform sustainable management and conservation of the entire ecosystem.

*Ph.D. student at the Institute of Arctic and Alpine Research, University of Colorado Boulder and FIU Algae Research Lab alumnus

Gaiser, E. E., Childers, D. L., Jones, R. D., Richards, J. H., Scinto, L. J., & Trexler, J. C. (2006). Periphyton responses to eutrophication in the Florida Everglades: Cross‐system patterns of structural and compositional change. Limnology and Oceanography, 51(1part2), 617-630.

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.

Gottlieb, A., Richards, J., & Gaiser, E. (2005). Effects of desiccation duration on the community structure and nutrient retention of short and long-hydroperiod Everglades periphyton mats. Aquatic Botany, 82(2), 99-112.

Lee, S. S., Gaiser, E. E., & Trexler, J. C. (2013). Diatom-based models for inferring hydrology and periphyton abundance in a subtropical karstic wetland: Implications for ecosystem-scale bioassessment. Wetlands, 33(1), 157-173.

RECOVER (2014). System Status Report. Comprehensive Everglades Restoration Plan, Restoration Coordination and Verification (RECOVER). U.S. Army Corps of Engineers Jacksonville District, Jacksonville, Florida, and South Florida Water Management District, West Palm Beach, Florida, USA. http://141.232.10.32/pm/ssr_2014/cerp_ssr_2014.aspx

Schulte, N. (2014). Fragilaria synegrotesca. In Diatoms of the United States. Retrieved June 16, 2017, from http://westerndiatoms.colorado.edu/taxa/species/fragilaria_synegrotesca

Wachnicka, A., Gaiser, E., Collins, L., Frankovich, T., & Boyer, J. (2010). Distribution of diatoms and development of diatom-based models for inferring salinity and nutrient concentrations in Florida Bay and adjacent coastal wetlands of south Florida (USA). Estuaries and Coasts, 33(5), 1080-1098.

Tags # Algae # Diatoms # Everglades Continue Reading

Thursday, February 16, 2017

Researching Algae, the Unsung Heroes of Aquatic Food Webs

vivien February 16, 2017 0

by Luca Marazzi^*

Why is it important to study algae?To start with, algae produce ~ 50% of the oxygen on planet Earth, they are food for small and large animals that in turn are eaten by people, but they also recycle nutrients and absorb CO₂ from the air; by existing and doing their own thing, these microorganisms provide these so called ecosystem services to human beings (Fig. 1). Moreover, as algae reproduce fast and are often adapted to specific environmental conditions, understanding how many species of algae, and which ones, live where and why give us cues as to the health of aquatic ecosystems, such as rivers, lakes, and wetlands.

Fig. 1. Simplified scheme of the role of algae in food webs (from my Ph.D. Thesis).

* Dr. Luca Marazzi is a freshwater ecologist working in Dr. Evelyn Gaiser’s research group in the School of Environment, Arts and Society at Florida International University. His main interest is how biodiversity, ecology, and distribution of algae in subtropical wetlands change with hydrology, nutrient concentrations and habitat. He curates the “Diatom of the month” blog series aimed to raise awareness on these algae, key primary producers and indicators of environmental change.

How did I get to do research on algae? For my Environmental Science MSc dissertation project, I worked in the northern Italy’s Alps studying Passerine bird migration, then my career path took me to office-based research on air quality and climate change. Wanting to go back to field research, I got a Ph.D. opportunity at University College London to study the biodiversity and biomass of microscopic algae in the Okavango Delta, a subject and a place I didn’t know much about, apart from biology courses and natural science readings. Between 2009 and 2010, I spent ~3 months in Maun (NW Botswana), to carry out the necessary sampling in this incredible, remote, and near pristine wetland in the middle of the Kalahari; another ~ 70 months were needed to master and apply taxonomy and microscope skills, conduct statistical analyses, read, think, and write my Thesis, as well as working to support my graduate studies.

Fast-forward 8+ years, here I am in sunny Miami, some 8,000 km away from the cold and misty mountain pass where I did my MSc research and 12,200 km from the Okavango, to work on another amazing wetland, the Everglades, as part of a Postdoctoral Associate contract in Dr. Evelyn’s Gaiser laboratory at Florida International University (FIU). After a few months at FIU putting together a database for the Comprehensive Everglades Research Plan Monitoring and Assessment Plan (CERP-MAP) and planning my publications, I decided, with my postdoc and Ph.D. advisors, to undertake an ambitious comparative study of patterns and drivers of species richness and life-history strategies in the Okavango and Everglades. We estimated that, the Okavango hosts, on average, ~80 species of algae in each sampling site, the Everglades have ‘only’ ~ 20 (Fig. 2). This is likely due to phosphorus scarcity, habitat fragmentation due to water diversion schemes, and nutrient pollution in the Everglades whereas the Okavango is still a near pristine wetland. Moreover, Florida is a long peninsula, while the Zambezi ecoregion in Africa has been historically well connected so that organisms may be able to better disperse to and from this wetland than in the Everglades. For more information, our paper “Algal richness and life-history strategies are influenced by hydrology and phosphorus in two major subtropical wetlands” is published in this month's issue of Freshwater Biology.

Fig. 2. Map of estimated algal richness and photos from the air: Okavango (above) and Everglades (below). Okavango (site averages); UPH= Upper Panhandle; LPH=Lower Panhandle; XAK=Xakanaxa; BOR=Boro; SAN=Santantadibe.Everglades; LKO=Lake Okeechobee; LOX=Loxahatchee; Out_ENP=Outside of Everglades National Park (including the Water Conservation Areas, WCA 2 and 3); ENP=Everglades National Park.

Although, in the Okavango, the flooding cycles have a stronger influence on species richness, as compared to phosphorus in the Everglades, maintaining and restoring the natural hydrology in these wetlands is critical for the preservation of algal communities, and thus for the health of food webs. Due to their outstanding geographic features and biodiversity, both these wetlands are protected as World Heritage sites, and are included in the Ramsar Convention on Wetlands of International Importance, and so it is critical to keep monitoring these ecosystems.

What’s next?

I am currently researching how algal dominance changes with nutrients and hydrology in the Everglades, which is relevant for freshwater flow and water quality restoration scenarios. I am also trying to create opportunities for comparative research in other subtropical wetlands. Last September, I visited the Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences and, with other 800 experts, attended the excellent 10^th INTECOL Wetlands conference in Changshu. I presented my comparative work and co-organized a workshop on future directions in wetlands studies, strengthened previous connections and made new ones with various colleagues working in Asia, South America and Australia. In June, other FIU scholars and I are planning to present our work at the next Society of Wetland Scientists’ meeting in Puerto Rico (“Celebrating Wetland Diversity Across the Landscape: Mountains to Mangroves”), where we aim to foster new collaborations with ecologists conducting research on wetland ecosystems and food webs in Central and South America, and beyond. Moreover, Dr. Gaiser, Dr. Barry H. Rosen (USGS) and I co-organized a special session on how algae / periphyton mats may respond to different nutrient and hydrology scenarios in the Everglades for the Greater Everglades Ecosystem Restoration (GEER 2017) conference. As wetlands are facing unprecedented anthropogenic impacts due to, for example, land use change, water diversion, and global warming, such collaborations among scientists, and between us and policy makers, are crucial to foster and inform sustainable management practices and strong conservation and restoration activities.

Fig. 3. (from top to bottom) In front of the conference venue with Drs. Wolfgang Junk (Federal University of Mato Grosso, Brazil), Max Finlayson (Charles Sturt University, Australia) and Xuhui Dong (Aarhus Institute of Advanced Studies, Denmark and Chinese Academy of Sciences); our International Network for Next Generation Ecologists workshop; two pictures from one of the conference fieldtrips to Shanghu Lake.

Tags # Algae # Conferences # Ecology 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