Showing posts with label Wetlands. Show all posts
Showing posts with label Wetlands. 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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Sunday, October 30, 2016

Diatom of the month – October 2016: Brachysira brebissonii

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 20th 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
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Thursday, September 29, 2016

Diatom of the month – September 2016: Aulacoseira granulata

September 29, 2016 0
by Luca Marazzi*

Last week about 800 ecologists from 72 countries, including myself, attended and presented their research at the 10th INTECOL Wetlands conference in the beautiful city of Changshu (2 hrs west of Shanghai). Before this event that takes place every four years (in 2012 we were in Orlando for INTECOL 9), I was honored to give a long seminar on my work on the algal communities of the Okavango Delta and Everglades at the Nanjing Institute of Geography and Limnology (NIGLAS) of the Chinese Academy of Sciences. I was invited to do that by my friend Xuhui Dong (we studied together for our PhD at the UCL Environmental Change Research Center in the UK). Xuhui and his colleagues recently conducted a paleolimnology study of several floodplain lakes along the mighty Yangtze River (Dong et al., 2016), where they found large numbers of Aulacoseira granulata [(Ehrenberg) Simonsen 1979], which is therefore our September diatom (a belated post).

              
                                               

                 











           Fig. 1. Diatoms of the genus Aulacoseira are characterized by point symmetry around their center                   (http://westerndiatoms.colorado.edu/): above: filament with live cells; below (left): frustule with spine; 
                                                below (right): cell with spines. LM scalebar = 10 µm.

This is a centric, planktonic, non-motile, filament-forming species that needs medium nutrient levels (mesotrophic), and prefers turbulent conditions. In Liangzi Lake Taibai Lake, and Shitang Lake (Fig. 2), A. granulata reached relative abundances of 78% in reference communities from sediment cores dating 1800-1950. This is due to the fact that, before the 1950s, the lake was subject to strong mixing2and free exchanges of mass and energy with the Yangtze River through its connection with the lakes, which seem to have created good conditions for large populations of this diatom3.


Fig. 2. Geographical distribution of 10 diatom-based palaeolimnological sites along the Yangtze River in Eastern China (Source: Dong et al., 2016).

Given the impressive number and extent of lakes and wetlands near the conference venue (369 wetlands, totaling 32,037 hectares, paddy fields excluded, or ~ 25% of Changshu city's total area5), many types of diatoms and other algae must very happy around here! And no wonder that Changshu may well become the first Wetland City under the Ramsar Conventionon Wetlands of International Importance. Among these wetlands, I and another ~50 attendees or so visited the Shanghu Lake, Nanhu Urban Wetland Park, and Shajiabang National Wetland Park(see Fig. 3); these are human-made aquatic ecosystems, and very peaceful and nature-and-culture-rich oases in an extremely densely populated region of China. Definitely worth a visit, if you happen to be around.


Fig. 3. Boating in a beautiful spot of the Shanghu Lake site during the conference excursion.



              


“The 10th INTECOL Wetlands conference logo includes water, bird, fish and plant four wetland elements which combine into an integrity. The shapes of flying crane, green aquatic plant, and swimming fish link into a colorful ribbon, expressing the 10th INTECOL International Wetlands Conference would be a linkage of international communication, exchange and cooperation for wetlands professionals and workers over the world” (http://www.intecol-10iwc.com).


Analyzing the abundance patterns of Aulacoseira granulata and other planktonic and benthic diatoms, paleolimnologists are able to reconstruct past environmental conditions, such as nutrients, pH, salinity, plant cover, and land use so that gradual and abrupt environmental changes can be better understood and predicted. Wetlands are under severe threats (the Wetland Extent Index has declined 30% in the 1970-2008 period4), understudied, and not too clearly defined yet, therefore, if we want to deeply inform their conservation and sustainable management, international collaborations stemming from high-profile conferences such as INTECOL Wetlands are crucial. I am happy to report from Changshu that this community is very motivated and vibrant. And diatoms, beyond being stunning living organisms, are essential to better understand aquatic ecosystems, so let’s conserve them and their habitats, shall we?


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


1. Dong X., Yang X., Chen X., Liu Q., Yao M., Wang R. and Xu M. Using sedimentary diatoms to identify reference conditions and historical variability in shallow lake ecosystems in the Yangtze floodplain. Marine and Freshwater Research 67, 803–815.
2. Owen R., and Crossley R. (1992). Spatial and temporal distribution of diatoms in sediments of Lake Malawi, central Africa, and ecological implications. Journal of Paleolimnology, 7, 55–71.
3. Yang G.S., Ma R.H., Zhang L., Jiang J.H., Yao S.C., Zhang M., and Zeng H. (2010). Lake status, major problems and protection strategy in China. Journal of Lake Sciences, 22, 799–810.
4. Dixon MJR, Loh J, Davidson NC, Beltrame C, Freeman R, Walpole MJ. (2016). Tracking global change in ecosystem area: The Wetland Extent Trends Index. Biological Conservation, 193, 27–35.
5. Source: http://www.intecol-10iwc.com
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Wednesday, July 20, 2016

Diatom of the month – July 2016: Nitzschia amphibia

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 research2 to 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-1 in 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.



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