Argentina features a large variety of freshwater phytoplankton habitats. They include rivers, large, deep, glacier-fed oligotrophic lakes in the Andean Cordillera (Patagonia) including those straddling the border to Chile, as well as shallow lakes and reservoirs, distributed along this territory.
The most distinctive hydrological feature of Argentina, however, is the La Plata watershed. The broad valleys of the Paraguay, Paraná and Uruguay rivers drain nearly one-quarter of the surface area of South America and carry a similar fraction of the continent’s fluvial discharge into the Atlantic Ocean.
Intensive studies have been carried out on this system of rivers from the headwaters in the Chaco and the Mato Grosso of Brasil to the delta near Buenos Aires. They also include the flood plains and shallow lakes of the Iberá and Entre Rios regions and are reflected in the subdivision of chapters in this book.

Many of the previously published observations already have a strong comparative element. The intent of this volume is to provide an overview of the research on phytoplankton assemblages in these waters. The overview is presented largely on a habitat-by-habitat basis but individual overviews also discuss generic aspects of the physiology, energy harvesting and production of phytoplankton, including mixotrophy. Some practical issues related to the supply of drinking water and the occurrence of harmful algae are also addressed; even the initiation of paleolimnology in Argentina is described. While much research still remains to be done in all areas of a territory as large as Argentina, this work is a valuable contribution to the knowledge of freshwater phytoplankton assemblages of the main aquatic ecosystems of the country. Moreover, the chapters add to and update the information available on the biodiversity of freshwater phytoplankton worldwide, chiefly because the Argentinian freshwater ecosystems studied and discussed in the chapters of this volume are so highly diverse.

Argentina is characterised by a large latitudinal extent and peculiar topography ranging from the Andes through high plains or “pampas” to lowland steppes. These geographic properties result in different climatic regions along temperature and aridity gradients. These conditions determine a wide variety of aquatic environments including large, glacier-fed oligotrophic lakes, high altitude or saline, alkaline wetlands, cool, humid peat bogs, as well as the watershed of La Plata with broad valleys of the Paraguay, Paraná and Uruguay rivers. The physical, chemical and biological characteristics of these water bodies can change both spatially and temporally.
The phycological studies in Argentina started with Ehrenberg (1854). Since then several research groups have greatly increased the taxonomic, floristical and ecological knowledge about algae of the country. One of the intensively studied regions is the Paraguay– Paraná–Uruguay river system that has been subjected to dam construction and discharge control. The great amount of papers published and the diversity of habitats and issues related to freshwater algae in Argentina led to the publication of this volume. Thirtyfour researchers from across Argentina collaborating in this work aimed at reviewing the existing information from studies on the phytoplankton in freshwater habitats of Argentina including description and analysis of both lentic and lotic communities.
The foreword was written by the great phycologist Colin S. Reynolds whose former students are among the contributors of this volume. The introduction provides a general overview of the content and the structure of the book. These parts are followed by three sections containing review papers.
The first section entitled “Phytoplankton diversity” consists of a paper in which the author, Guillermo Tell provides an overall picture of high phytoplankton diversity in Argentina. This part describes the phytoplankton taxa occurring in the various climatic regions of the country including taxa with wide or narrow distribution range, as well as possibly endemic species and infraspecific entities.
The information in the second chapter is delivered on a habitat-by-habitat basis. There are three main geomorphological regions in Argentina: the Andes Cordillera and associated mountains holding glacial and tectonic lakes, the Great Plains dominated by continental sedimentation processes with neo-tectonic activity and Patagonia with basaltic plateaus and coarse grain fans. Besides, six limno-regions can be defined that constitute the subsections of the second chapter. Puna, Chaco-Pampean Plain, Peri-Pampean Sierras, Andean Patagonia, Patagonian Plateau and Misiones Plateau have different topographical and climatic conditions, therefore containing freshwater habitats with wide range of physical, chemical and biological characteristics. Information on the phytoplankton inhabiting various freshwater ecosystems in these regions is collected in eighteen papers and the relationship of this community with physical-chemical parameters and in several cases its biological interactions are also discussed. The presented water bodies include both lentic environments ranging from high mountain wetlands and lakes of glacial origin in the Andes to shallow lakes in the Pampean Plain and Patagonia and lotic systems varying from the mainly lowland Paraná River Basin to the exo- and endorheic rivers of Cordobá system in the hilly central area. Aquatic systems exposed to substantial human impact, such as reservoirs, as well as urban and suburban polluted rivers also occur among the studied waters. Previous available information on some regions, e.g. Puna and Patagonian Plateau is scarce that increases the significance of the articles on these regions. Some papers are particularly interesting. Casco et al. use more than thirty-year data from monitoring programs on the reservoirs along three Patagonian rivers. Diaz and Beamud present the main patterns of extremophile phytoplankton populations through the 10-year study of the natural acidic Lake Caviahue in Andean Patagonia. Mataloni summarises the results of scarce phytoplankton studies of a major floristical framework carried out on the only insular province of Argentina, Tierra del Fuego that combines lowland dry steppe with the Andean ridges and extended peatland area, eutrophic coastal ponds with ultraoligotrophic glacial lakes and small peat bogs.
The last paper in this chapter slightly differs from the previous ones. Maidana and Aménabar provide an interesting overview of palaeolimnology that has recently begun to improve in Argentina. The article includes the description of conventional methodologies and the history of this discipline in the country.
In the third main chapter, relevant specific issues concerning phytoplankton are discussed involving the available data obtained in freshwater systems from Argentina. Villafañe et al. investigate the question what kind of factors can influence the measured values of phytoplankton primary production. Izaguirre et al. describe photosynthetic picoplankton including pro- and eukaryotes that are as important in the carbon flow of many aquatic systems as tiny they are (with cell-size in the range 0.2 to 2 μm). The distribution of the main types of these organisms depends on light intensity.
Light is approached also in two other papers from two sides. Pérez investigate it as the energy source of phytoplankton of which availability can be affected by several factors. He presents an optical characterisation of various clear and turbid vegetated Argentinean lakes using bio-optical properties and optically active substances including chlorophyll-a. Meanwhile, Helbling and Villafañe review the negative impact of ultraviolet radiation on phytoplankton, particularly on the photosystem and DNA molecule. They discuss different acclimation strategies as well.
Beside photosynthesis, some taxa can switch to heterotrophic nutrition mode. This life strategy called mixotrophy is proved to be very useful at both ends of light and nutrient gradients as it can be read in Modenutti’s paper.
Harmful algal bloom in Argentina was observed first in 1944. Since then the phenomenon occurred several times mostly associated to toxigenic cyanobacteria. Eschenique et al. present four case studies related with the presence of toxigenic cyanobacteria in drinking water.
Overall, this volume contains valuable information on various aquatic habitats characteristic to Argentina. It can be useful to everyone who are interested either in these types of waters or generally the features of phytoplankton.

M. Duleba

Acta Botanica Hungarica 57 (2015)