“A quantum leap every which way? Understanding the extent and origins of microalgal species diversity and their relevance in a changing world.”
Margalef [1972: Trans. Connecticut Acad. Arts & Sci 14: 211] noted that “… the limitation of the human capacity to handle diversity probably influences any description of nature …” and so the measurement of diversity “... is a function of the beholder as well as of what is measured”. Certainly this applies to microalgae. While our perceptions of microalgal diversity were based on light microscopical observations of morphology, it seemed that there were rather few, widely distributed species, leading to the idea [cf. R.M. May 1988, Science 241: 1441] that there is a diversity ‘deficit’ that requires explanation. A series of papers by B.J. Finlay and colleagues in the early years of the new millenium suggested that low diversity and lack of endemism in microalgae and protists might be the consequence of enormous population sizes driving high dispersal rates and restricting opportunities for allopatric speciation – the ‘ubiquity hypothesis’. But is there in fact a diversity deficit among microalgae and protists? Recent evidence, which I will review, suggests that species diversity is much higher than previously thought and that, while lineages do seem to spread rather rapidly (so that there are few higher taxa that show endemism), there is ample opportunity for population divergence and speciation. Some practical questions arise: is it necessary to take this ‘extra’ diversity into account, e.g. in ecological studies or biomonitoring? And if it is necessary, how can it be done?
David Mann did his PhD in the phycology group at the University of Bristol, supervised by the microalgal ecologist and taxonomist Prof Frank Round. He moved to the University of Edinburgh in 1978 and taught in the Botany Department until 1990, when he became Deputy Director of the Royal Botanic Garden Edinburgh. After six years dominated by administration, he gained Merit Promotion to return to research. He took partial retirement in 2014 and now spends 75% of the year at IRTA, Sant Carles de La Ràpita, Catalonia. He has edited 3 international journals, is coauthor of a textbook on algae (‘Algae: an introduction to phycology’) and of the widely cited ‘The Diatoms. Biology and Morphology of the Genera’, and has written over 170 scientific papers, principally on diatom biology, speciation and systematics. He received the G.W. Prescott Award of the Phycological Society of America in 1991 and 1996 (given for the best scientific monograph on algae), and has won three national awards for photography and visual arts; he also has a fine art degree.
Global-scale experiments: an emerging tool for exploring the functioning of freshwater ecosystems
Individual ecological studies, although suitable for testing hypotheses and developing theory, provide site-specific information that is difficult to extrapolate to provide broad generalizations. Today, emerging globally relevant questions (e.g., climate change, biodiversity loss, invasive species or habitat degradation) require a reconsideration of what approaches would be best for understanding large-scale ecological patterns and processes. A technique commonly used for this purpose is meta-analysis, a quantitative approach to reviewing, integrating, and summarizing large numbers of independent studies. However, the robustness of a meta-analysis relies on the individual studies selected for inclusion, and issues of scale and methodology cannot be controlled retrospectively. An emerging, alternative approach is global-scale coordinated experiments, run in parallel by several research groups in multiple locations around the globe. These experiments have the advantage of addressing global problems and exploring general ecological theory, while offering the precision of controlled experiments. We will review the existing global-scale experiments conducted by freshwater ecologists and discuss the potential of this type of studies for developing ecological theory and advancing our understanding of freshwater ecosystem functioning.
Luz Boyero did her PhD on multi-scale patterns of variation of stream invertebrates at the Natural History Museum (MNCN-CSIC) in 2002, supervised by Antonio García-Valdecasas. She moved to Australia, where she worked first as a Postdoc and then as Senior Researcher of the School of Marine and Tropical Biology at the James Cook University (JCU). She was also a Research Associate at the Smithsonian Tropical Research Institute (STRI) for a 3-year period. In 2009 she returned to Spain with a ‘Ramón y Cajal’ contract at the Doñana Biological Station (EBD-CSIC), until she won a Research Professor position with Ikerbasque at the University of the Basque Country (UPV/EHU) in 2013. Currently she also is an Adjunct Principal Research Fellow at JCU. She has been editor for 3 and reviewer for 37 international scientific journals, and has published 61 scientific papers. She coordinates the ‘Global Stream Decomposition Network’, which involves freshwater ecologists from more than 20 countries in 5 continents who develop global-scale coordinated experiments on plant litter decomposition in streams. She currently lives in the Basque Country and is mother of 2 daughters.
Anthropogenic stressors affect carbon stocks and fluxes in wetlands at a variety of scales and regions.
Wetland ecosystems are one of the largest global carbon sinks holding approximately 30% of the estimated 1,500 Pg of global soil carbon, despite occupying only 5-8% of its land surface. Globally, more than half of the historical wetland area has been lost due to anthropogenic activities resulting in a net transfer of carbon from the soil to the atmosphere. There have been few comprehensive studies to quantify wetland soil carbon stocks over large geographic regions, nor how human disturbance affect these stocks through processes such as altered rates of soil carbon accretion and methane emissions. Here I report on studies conducted in three regions to investigate patterns in soil carbon stocks and fluxes. The Ebro Delta (Catalonia, Spain) is an ecologically important region where wetlands are under threat from sea level rise, subsidence and reduction of fluvial sediment inputs. Here rates of C sequestration ranged from 20 to 500 gC m-1 yr-1, with highest rates seen in areas where hydrologic and sediment subsidies were greatest. Methane emissions were low in salt and brackish sites, making them net carbon sinks. In the U.S., soil carbon data were collected in the National Wetland Condition Assessment, a probabilistic, spatially representative national survey, to provide unbiased estimates of soil carbon at the national scale. Carbon stocks varied as a function of location and wetland type, which are intrinsically linked, and regional carbon densities reflect a high degree of variability. Carbon stocks decreased significantly as anthropogenic stressors increased and the deepest soil layers sampled (90-120 cm) showed the greatest differences in carbon content. These results are compared to mechanistic studies conduced in the Eastern US to identify the factors that affect carbon sequestration along a gradient of human disturbance. Here, as in the Ebro Delta, we found a strong link between land use, hydrologic patterns, and carbon accretion and storage. These C accretion rates were related to changes in land use that that generate and deliver water sediment to down gradient wetland sites. Overall these studies provide a mechanistic explanation of how human activities decrease soil carbon at regional scales. Efforts to protect climate should address the role of wetlands as climate regulators and include measures for the conservation and sustainable management of their carbon stocks.
Siobhan Fennessy is the Jordan professor of Biology and Environmental Science at Kenyon College where she studies wetland ecology, biological assessment methods, watershed-based assessments, restoration ecology, and the role wetlands in the global carbon cycle. She received her Ph.D. in Environmental Biology from the Ohio State University in 1991. She previously served on the faculty of the Geography Department of University College London and held a joint appointment at the Station Biologique du la Tour du Valat investigating human impacts to Mediterranean wetlands.
She has been lead on numerous grant-funded projects designed to develop and test biological assessment methods to evaluate wetland ecological condition on a national scale. She was awarded a Fulbright Fellowship in 2013 to study carbon fluxes in wetlands in the Ebro Delta.
Siobhan was recently appointed as a Lead Author to the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) for the global assessment of land degradation and restoration, and the Ramsar Convention’s Scientific and Technical and Review Panel. She also serves on the U.S. Water Science and Technology Board, a governing board of the National Academy of Sciences.
Biogeography of stream-dwelling decomposer fungi: current knowledge and future perspectives
Until the recognition of the crucial role that fungi play in plant-litter decomposition in streams, limnologists largely ignored these organisms. In particular, Ingoldian fungi or aquatic hyphomycetes, abound in well-aerated waters and are regarded as the dominant fungal decomposers of decaying leaves in streams. The predominance of aquatic hyphomycetes on submerged decaying leaves over other fungal groups is mainly attributed to physiological adaptations to fast flowing waters. These include: i) the high production rates of characteristically shaped conidia; tetraradiate or sigmoid types of spores that act as miniature anchors, arresting on a suitable substratum in rapid flowing waters, and ii) the ability to produce a variety of extracellular enzymes able to break the major plant polysaccharides, which increase litter quality to invertebrate detritivores. Since Ingold’s (1942) initial description that mycologists have been interested in deciphering global distribution patterns of aquatic hyphomycetes. Much of this knowledge emerged from species classification based on their characteristic conidial shapes (morphospecies). Based on data from 352 publications, documenting 335 morphospecies, I will present distribution patterns of aquatic hyphomycetes from studies throughout the world in an attempt to better understand the magnitude of global species richness, patterns of biodiversity and the extent of cosmopolitanism versus endemism, as well as the relative influence of contemporary environmental factors versus the legacies of historical events on present-day distribution patterns.
Sofia Duarte received her PhD degree in Sciences, at the University of Minho, Portugal, in 2008, with the project “Biodiversity and activity of microbial decomposers in streams under anthropogenic stress”, which was conducted in collaboration with University of Aveiro, in Portugal, and University Paul Sabatier, in France.
In subsequent post-doctoral studies at University of Minho, she worked in the optimization of molecular tools for assessing fungal diversity and activity in freshwaters, in collaboration with Mount Allison University, in Canada. This post-doc project contributed to: i) increase the number of fungal species with connected DNA barcodes on genetic databases; ii) investigate inter- and intra-specific relationships and phylogeographic patterns among aquatic fungi, by using DNA barcodes and, iii) assess total and active fungal diversity in environmental samples, using next generation sequencing approaches targeting both rDNA and rRNA, respectively.
Currently she shifted from freshwater to estuarine ecosystems, where she is optimizing metabarcoding approaches for monitoring benthic communities, in collaboration with the University of Guelph, in Canada.
Environmental impacts caused by the invasion of exotic plants in riverbanks
Floodplains have environmental filters which are little intense for the establishment of vegetal life. In one side, soil resources are abundant, both water and nutrients. On the other side, competence is not too intense, thanks to perturbations that periodic floods cause, clearing vegetation and delivering resources for pioneer species. If we add anthropic perturbations (such as riparian forest cutting for agriculture, flood regulation, riverbank alterations, etc) and the fact that rivers are efficient dispersers of all kind of propagules, it is easy to understand that these are one of the most propitious environments for the establishment and propagation of exotic plants. The invasion of exotic plants is recognized as a very important factor of global change, together with the climate change and land use change. In this work we analyze the environmental impacts on rivers and riverbanks caused by exotic tree invasions. We focus on the consequences on water and soil matter cycles caused by the entry of exotic trees leaf trash, and how these changes may influence on the taxonomic composition of invertebrates processing this organic matter.
Pilar Castro did her doctoral dissertation in the Pyrenean Institute of Ecology (CSIC) on the item of adaptation and acclimation of vegetation to Mediterranean Climate. In 1997 she started working as an associate teacher in the University of Alcalá, becoming after assistant professor (1999-2003) and then contracted lecturer (2003-2007). She obtained the full professor position after the National Habilitation in 2007. Professor Pilar Castro has participated in 15 investigation projects, most in the national area, being the main investigator in four of them. She has directed/co-directed 6 doctoral dissertations. Along this period she has collaborated with investigators in different countries (Great Britain, Estonia, Argentina, the Netherlands and Chile). Her investigation activity has turned into 58 articles in SCI Journals, and also being and invited editor in Ecosistemas Magazine. Since 2014 she is a member of the Managing Committee of an Action Cost of the European Union. Her investigation activity is combined with and intense teaching activity in Environmental Sciences and Biology Schools of the University of Alcalá, with the direction of Degree and Master final Works and with the performance of Vice Dean position of Environmental Science School (2004-2010). Since 2007 her investigation activity is focused on trying to explain the causes of the success of exotic invasive species, and evaluating their impact on ecosystems.
The role of wetlands in mitigating pollutants in our landscape and planet
Eminent Scholar and Director, Everglades Wetland Research Park Sproul Chair for Southwest Florida Habitat Restoration and Management Florida Gulf Coast University, Naples Florida, USA Editor-in-Chief, Ecological Engineering
The world is faced with unprecedented threats to our aquatic ecosystems from excessive nutrients, caused by agricultural and urban runoff and discharges. Fully 750 aquatic ecosystems suffer from degraded ecosystem services with impairments described as hypoxia, dead zones, and harmful algal blooms, most due to pollution caused by excessive nitrogen and phosphorus. Also, we have increased the atmospheric pool of carbon by 40% since industrial times leading to several impacts related to climate change. In the meantime, it has been estimated that, on a global scale, we have lost half of our original wetlands to our current extent of 8 to 12 million km2, most of that loss in the 20th century. I am proposing here a sizeable increase in our wetland resources around the world, solving the diminishing wetland problem, with the strategic purpose of minimizing the excess phosphorus, nitrogen, and carbon in our rural landscapes in a sustainable fashion. Examples include attempts to minimize phosphorus inflows to the Florida Everglades with wetlands to quite low concentrations and a proposal to restore the Black Swamp in NW Ohio to minimize eutrophication of Lake Erie in the Laurentian Great Lakes. Nitrogen retention by wetlands and riparian forests in Midwestern USA has been proposed for 15 years as a solution to the seasonal hypoxia in the northern portion of the Gulf of Mexico. Finally the case of wetlands being carbon sinks through carbon sequestration will be presented in the context of mitigating human-caused increases of CO2 in the atmosphere, with the full understanding that greenhouse gas CH4 emissions typical of most wetland ecosystems need to be taken into account.
Dr. William J. “Bill” Mitsch has been Eminent Scholar and Director, Everglades Wetland Research Park, and Juliet C. Sproul Chair for Southwest Florida Habitat Restoration and Management at Florida Gulf Coast University’s Kapnick Center field station in Naples Florida since Fall 2012. Before that he was Distinguished Professor of Environmental Science at The Ohio State University where he taught for 26 years; he is Founding Director of the 50-acre Olentangy River Wetland Research Park in Columbus. He also holds courtesy faculty appointments at University of Florida, University of Notre Dame, and University of South Florida.
His research and teaching have focused on wetland ecology and biogeochemistry, wetland creation and restoration, ecological engineering and ecosystem restoration, and ecosystem modeling. His over 600 publications, reports, abstracts and books, include the 5th edition of the popular textbook Wetlands completed in April 2015. He is editor-in-chief of the international journal Ecological Engineering, which he founded in 1992. He was awarded the 2004 Stockholm Water Prize by King Carl XVI Gustaf of Sweden. He has also been awarded the Ramsar Award for Merit from the Ramsar Convention in Switzerland (2015), the Lifetime Achievement Award from the Society of Wetland Scientists (2007), and the Theodore M. Sperry Award from the Society for Ecological Restoration International (2005). He received a Doctorate honoris causa from the University of Tartu, Estonia and an Einstein Professorship from the Chinese Academy of Sciences, both in 2010.
Dr. Mitsch has advised to completion with thesis or dissertation 75 graduate students (including 24 Ph.D. students) and 13 post-docs. Seventeen of his former graduate students and post-docs are currently teaching in colleges and universities around the USA and world. He is currently advising 6 graduate students in Florida.
THE INFLUENCE OF MEDITERRANEAN RIPARIAN ZONES ON STREAM NITROGEN DYNAMICS
A CATCHMENT APPROACH
During last decade, anthropogenic activities have doubled the available nitrogen (N) in catchments, leading to several environmental problems. Within catchments, riparian areas are recognized to be natural filters of N because they can substantially diminish the delivery of this essential nutrient from terrestrial to aquatic ecosystems. However, understanding the influence of riparian zones on regulating N export from catchments still remains a challenge, mainly because stream water chemistry integrates biogeochemical processes co-occurring within upland, riparian, and fluvial ecosystems. In this talk, I will summarize the results of different empirical and modelling approaches in order to examine in detail some of the processes and mechanisms by which Mediterranean riparian zones can regulate both stream hydrology and catchment N exports. In addition, I will show how the combination of different catchment pools (soils, groundwater and stream water) and temporal scales (ranging from daily to annual) enables the analysis of the riparian systems within a unique upland-riparian-stream context. Overall, findings gathered in my thesis question the well-established idea that riparian zones are efficient N buffers, at least for Mediterranean regions, and stress that an integrated view of upland, riparian, and stream ecosystems is essential for advancing our understanding of catchment hydrology and biogeochemistry.
Anna Lupon received both B.S (2009) and M.S (2010) degrees from the Universitat de Barcelona (Barcelona, Spain). She joined the Fluvial Biogeochemistry research group in 2009, where Anna is pursuing her PhD in The riparian forest: Effects on hydrological resources and nitrogen dynamics in Mediterranean catchments advised by Susana Bernal and Francesc Sabater. She visited the University of Florida in Spring 2012 and the University of Reading in Spring 2013. Anna teaches Evolutionary ecology at the Biology Faculty (UB). Her current research interests involve catchment ecology and biogeochemistry, with special focus on catchment hydrology, stream nutrient dynamics, soil biogeochemistry and global change.