Showing posts with label Ecology. Show all posts
Showing posts with label Ecology. Show all posts

Thursday, February 16, 2017

Researching Algae, the Unsung Heroes of Aquatic Food Webs

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 10th 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.

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Wednesday, April 20, 2016

Diatom of the month – April 2016: Cocconeis placentula

April 20, 2016 0
by Luca Marazzi*

‘Who’ is it and where does it live?

This diatom is monoraphid, that is to say it has a raphe only on one valve, as shown in the figures. Monoraphid species are one of 9 major morphological types of diatoms - the other ones are: centric (like Cyclotella meneghiniana), araphid (e.g. Asterionella formosa, which forms star-shaped colonies!), eunotioid (e.g. the beautifully ornamented Eunotia diadema), symmetrical biraphid (e.g. the slender Navicula lanceolata), asymmetrical biraphid (e.g. Gomphonema parvulum), epithemioid (e.g. Rhopalodia gibba, which hosts nitrogen-fixing bacteria as symbionts), nitzschioid (e.g. the organic pollution-loving Nitzschia palea), and surirelloid (the big Surirella ovalis)1. Like in many other cases, the taxonomy is far from settled though; following recent research, numerous specimens usually named C. placentula should be more accurately named Cocconeis lineata and C. euglypta2.

                                          
 Cocconeis placentula / C. lineata from a 2003 Everglades sample (Dr. Evelyn Gaiser Lab photo archive). 

 
                              
        

 Valve with (left) and without (right) raphe (http://westerndiatoms.colorado.edu/; scalebar: 10 µm). Recent taxonomic work suggests that this be named C. euglypta (pers. comm. Tom Frankovich)2.

Like many other diatoms that are adapted to specific environmental conditions, Cocconeis placentula, is a freshwater epiphytic species that tolerates high salinity levels in the water. Why? A 2013 study on the Coroong wetlands (Australia) suggests that this diatom (and C. pinnata) is capable of regulating the size of its pore holes which control nutrient flows between the cells and the environment3. With higher concentrations of salt, this diatom basically spits out the ions in excess from aptly enlarged pores.

Why are we studying it?

Algae such as our diatoms of the month are extremely useful indicators or sentinels of the environmental changes occurring in freshwater ecosystems, including (as by now you know, if you read previous posts) the Florida Everglades. A recent study on sediment cores collected in this wetland’s marshes identified several species best adapted to shallow habitats with short hydroperiod (the number of days during which a site is flooded / wet), e.g. Nitzschia serpentiraphe, Achnanthidium minutissimum, and C. placentula, that were most abundant in shallow water / short hydroperiod habitats (<38 cm; <300 days), as opposed to deeper water / long hydroperiod habitats (>46 cm; >400 days), which were preferred by other taxa such as Eunotia flexuosa and Encyonema evergladianum4. So data on these microalgae, together with key hydrological and water quality information, can improve our understanding of the effects of water flow changes in the Everglades. The impacts of large-scale canalizations and water retention schemes - to respectively irrigate crops and protect cities from either floods or droughts – on the ecosystem – and that of restoration projects to enhance water flow to natural areas have been monitored for many years. Measuring and estimating past and present environmental conditions is crucial to provide South Florida water managers and state and federal agency policy makers with realistic scenarios of what the marshes and prairies will look like in the years to come, subject to different natural conditions and human choices. These models are then used by organizations such as the South Florida Water Management District, and the US Army Corps of Engineers, for example to increase the important flows of freshwater to Everglades National Park (“The largest subtropical wilderness in the United States”).


 Faculty and staff members of FIU, South Florida Water Management District, and US Army Corps of Engineers near a large tree island during an official visit to Water Conservation Area 3A (November 2015).


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

1. Source: http://westerndiatoms.colorado.edu/taxa
2. Romero O.E., Jahn R. (2013) Typification of Cocconeis lineata and Cocconeis euglypta. Diatom Research,
    28, 175–184. 
3. Leterme S.C., Prime E., Mitchell J., Brown M.H., Ellis A.V. Diatom adaptability to environmental change: a case study   of two Cocconeis species from high-salinity areas. Diatom Research, 28, 29–35.
4. Sanchez C., Gaiser E.E., Saunders C.J., Wachnicka A.H., Oehm N., Craft C. (2013) Challenges in using siliceous subfossils as a tool for inferring past water level and hydroperiod in Everglades marshes. Journal of Paleolimnology, 49, 45–66.

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Tuesday, November 18, 2014

The Wonderful World of Diatoms

November 18, 2014 0


I admit that I ended that last post a bit unclear. But diatoms, it should be said, aren’t (or, rather, shouldn't be said since I shouldn't use double negatives. Ah, well.).


http://tmagazine.blogs.nytimes.com/2014/09/16/diatomist-film-matthew-killip-premiere/?_php=true&_type=blogs&smid=nytcore-ipad-share&smprod=nytcore-ipad&_r=0
Not physically, that is; you see, diatom cell walls are made of silica (glass), and that feature is actually incredibly important (not to mention gives rise to beautiful 'micromanipulations' like this one by Klaus Kemp - different colors in part because of different thicknesses of their glass). Diatoms arose between 180 and 225 million years ago – youngsters in the algal world (compare that to the geezer cyanobacteria of 3+ billion – way vintage) – and in so doing utilized an under-used, widely available resource that set them apart. The genealogy (or “systematics”) of diatoms has since expanded to include anywhere from 20,000 to over 1 million species that span almost every aquatic or semi-aquatic habitat imaginable – oceans, lakes, rivers, moss, soil. In those habitats they can be suspended in the water column, anchored onto plants or rocks, and moving through the soil. And the species diversity of diatoms is mirrored by their physical diversity: some are round (‘centric’ – shaped like a barrel), others needle-like (‘pennate’), others bent or otherwise contorted (‘yogis’ – don’t quote me on that, though! Those are really just rebellious pennates), all of them in a variety of shapes and sizes. They are unicellular (just like, say, a red blood cell. Only they can be just as small as a red blood cell [~7 micrometers] or over 20 times as large!). Their glass cell walls are adorned with tiny holes in very distinct patterns, glass thickness varies, spines might protrude, a slit used to move may vary in shape and placement. And what’s cool is that you can use all these miniscule features to differentiate species based on appearance alone – quickly and relatively inexpensively (with the right training and tools – mostly a good microscope and a literal library of reference material. I hope you know German, though [the language of some of the best reference texts]!). So the take-home is that diatoms can be identified based on species’ unique cell wall ornamentation (a Who’s Who Among Diatoms in American Rivers and Lakes, if you will. Now that's a taxonomy textbook title!), and that allows us to figure out who’s where and why.
Tom-ay-to, tom-ah-to.

And understanding who’s where lets us use diatoms as very dependable indicators for ecosystem changes. Diatoms are sensitive and like what they like (what's that on the Myers-Briggs Type Indicator? ISFP?). They often fill very specific roles in their communities, and if something happens to the environment – changing temperatures, physical disturbance, nutrient enrichment – then the diatoms, and other algae, are among the first to respond. So you can catch the effects of, say, agricultural runoff into a lake early on if you look at how the algae changes. And arguably the best algae for noting that change is the diatoms because of their diversity, ID-ability, and preservability. Because glass tends to linger in most conditions we can even take a soil core of that 'polluted' lake and examine the diatoms from years past to then model and understand what past conditions were like! Their cell wall ornamentation is preserved, allowing us to still identify their dead ‘shells’ (properly, “frustules”) – a natural preservation that we replicate in the lab by killing modern diatoms so we can look at just their glass frustules to make identification easier. Talk about bio-indicators (and cruelty to diatoms). And that diversity within and among habitats allows us to use diatoms to answer some very fundamental ecological questions involving metacommunity diversity and microbial dispersal and biogeography (I know, I know: those will be discussed in entirely separate posts to come).

And I’m just getting started (“Oh, no,” you’re thinking.). I’ll be quick. Going back to the uninformative reasons of why they’re awesome, some clarification. Diatoms alone produce around anywhere from 25 to 40% of Earth’s oxygen and are large carbon sinks (translation: they gobble up that pesky carbon dioxide and give us oxygen, free of charge. So generous!). They produce oil droplets that are delicacies for primary consumers (as well as nutritious – think Flintstones gummies good) – and they have potential to be used for biofuels (they’re trying to squeeze the oil out of them. Literally.). When they died off en masse thousands of years ago (diatom genocide! Where was the UN?!) their graveyards eventually became reserves of  


(or diatomaceous earth), which is great if you like clean teeth (as an abrasive) and beer (as filters) and don’t like ants in your house (natural pesticide). But even when they’re alive some species secrete vast amounts of 'mucus' around them that invite all sorts of other creatures (mainly bacteria, fungi, and/or other algae) to party and form a biofilm, which have even more ecosystem benefits (outside of making you fall on your face in a lake)! Imagine coating yourself in your own snot and letting stay anything that wants to use, eat, or add onto that snot (not quite a perfect example of the intricacies, but what a vivid picture for the general idea! That makes the "affectionate" term of "rock snot" for biofilms of the diatom Didymosphenia geminata even apter, eh?).

Didymosphenia geminata biofilm
I realize that all of this may be a little too general to be overly informative, but my hope is that it piques your interest in learning a bit more about diatoms – whether scientist or enthusiast. In the Everglades we’re using diatoms to look at ecosystem-scale effects of sea level rise on the Everglades. Diatom indicator species of nutrient enrichment are used in assessing the efficacy of Everglades restoration and conservation. We see poignant applications of diatom science right here in South Florida that are visible all the way up to reports to Congress! (Mastogloia smithii Goes To Washington, anyone? Though Sylvia Lee may have something to say about that nomenclature!)

But in all this excitement about diatoms it’s important to recognize algae as a whole. Cf. T. jeffersonii (invalid, illegitimate, and insane taxonomy?) doesn’t agree with discrimination, remember. So to rectify this miscarriage of algal civil rights, stay tuned for the next installment of the Wonderful World of Algae! (Will there be death? Will there be destruction [of tasteful writing, yes! Of algae…?]? Will there be adorable pictures of sea otters on an Everglades research page? Find out next week!)

This blog post was written by Nick Schulte, a Master's student in Evelyn Gaiser's lab at FIU.
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Thursday, September 11, 2014

Okeechobee or Okoboji? An Everglades Student’s Corny Tale

September 11, 2014 0

This post was written by Nick Schulte, a Master's student in Evelyn Gaiser's lab at Florida International University. 

So where would you go to study how Everglades algae respond to increased nutrients from sea level rise? The Florida Everglades, right? That’s what I thought. But I went to Iowa.


Iowa Lakeside Laboratory, more specifically, on the shores of Lake Okoboji (yes, I still confuse it with that big lake in the northern ‘Glades). A bit clearer but still unhelpful? This summer I attended two courses at Lakeside: Ecology and Systematics of Diatoms and Ecology and Systematics of Freshwater Algae. In that order – specific to general, that’s how it’s normally done, right? Start looking at the fineries of a specific group of algae (“the algae that live in glass houses”, or diatoms) and then see how they fit into the bigger picture of general phycology (“phykos” for “seaweed”). It actually makes a lot sense, especially when my research pays particular attention to the changes among the diatoms within algae communities in the Everglades (now I’m finally getting to the point). And it just so happens that the place to learn about diatoms is 1,800 miles from South Florida (or a 26-hour car drive, but who counted?). So while many of my peers were up to their knees in peat or swarmed by mosquitoes in the mangroves of the Everglades this summer field season, I was swarmed by mosquitoes by the lake, up to my knees in what many would call “lake scum”, and up to my eyes in diatoms in Iowa. And it was excellent.

Life at a biological field station is an experience completely its own, and as such it’ll get its own blog post! But suffice it to say, here, that it facilitates connections that are hard-pressed to forge elsewhere – connections to the research, to faculty, to peers, to the community, to nature. And it is my good fortune that Gene Stoermer established a “Diatom Clinic” at Lakeside in 1963 and that this course has persisted for 52 years, taught by Gene, Charlie Reimer, Gene again, and now Mark Edlund and Sarah Spaulding – all rock stars in diatom science committed to grooming new generations of diatomists. And the intrigue and utility of diatoms (boy, what a boring book title – we’ll have to think of something better) is such that students from all over the world – literally – come to this Great Lakes region of Iowa each summer to gain a proper education and exposure to the wonderful world of diatoms (getting there. But, really, “Great Lakes region of Iowa”?! Whoever heard of such a thing? Sounded like science fiction to me.). The class is capped at ten students per summer (one four-week session), and this year we came from Miami, Delaware, Colorado, Utah, MinnesOta, Montana, Ontario, and Colombia – with some old class T.A.s who can’t get enough from Arkansas and Macedonia. In short, students and professionals come from all over for a very focused class on a very focused group of algae that many people probably don’t know exist.

But, why? Why diatoms? If you can’t even see these microalgae, why even care? Why not care more about the cursed algae causing that green scum layer on my mom’s supposed-to-be-blue pool? Or those algae being used to solve our fossil fuel dependency? Well, we do care about those – I think cf. Thomas jeffersonii is keyed out as having “all algae are created equal” in its striae pattern (who wants to erect that genus?!) – but some pay particular attention to diatoms for a variety of reasons. And you can see diatoms – but few with the unaided eye. But when a bunch of 10 µm cells (1/1000thof a millimeter) hold a party they can be seen collectively (but only if you want to be seen as a party crasher). If you’ve ever fallen ungracefully into a lake because you slipped on those muddy rocks, don’t curse the mud but the diatoms and the mucilage they produce. Actually, I wouldn’t curse them – maybe reprimand them for their slippery inconvenience – but get to know them (especially now that you’re intimately acquainted, having fallen face first into a nice community [biofilm] of them). When you get to know them you realize that diatoms. are. awesome.

              E Pleurosira Unum? Creepy.

Diatoms are generically and specifically diverse (see what I did there?), widespread, productive, and tasty; they throw great house parties (just don’t throw rocks – their cell walls are glass after all); and they keep on giving after they’ve stopped living. They’re the algae you want to get to know at a party, the ones that always have your back and will give you good guidance in times of trouble (just like Mother Mary). They’re your best friends in the algae world.

Want to know why? Why choose diatoms over beautiful kelp forests or tasty nori (Porphyra, a red alga ‘seaweed’) or nutritious Spirulina (cyanobacteria)? Will Nick be held accountable for such a preposterous claim (after all, who 
doesn’t love sea otters?!)? Will we ever get to the “wonder” in the Wonderful World of Diatoms? Tune in next week for even more humorless asides and frustrating skirting around the facts (we are in a bit of a political lull, though!). Tune in next week for these answers and more!

(In all seriousness, thanks for reading this far, and I really do hope you’ll continue with this series!)




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