figure a

Henri Dumont at a large Branchiopod meeting in Vijajawada (India), September 2007. Source

Henri Jean François Dumont was born in 1942 in Denderleeuw, Belgium. He studied biology and zoology at the State University of Ghent (now: Ghent University) under the guidance of Prof. L. De Coninck, successor to Prof P. van Oye, who was the founding editor of Hydrobiologia. Henri obtained his PhD in 1968 with a thesis on “Limnology of Lake Donk in Eastern Flanders”. Since then, Henri was Head of the Limnology section at the Zoology Department of the Ghent University, until he became full professor of Ecology in 1986 at the same university.

Henri has been active in many fields of freshwater biology, but one of his main research subjects for more than a decade was the “Limnology of the Sahara”. The title itself sounds paradoxical, and in one of his many talks on this subject he jokingly compared it to a topic like “The orchids of Antarctica”. But this parallel of course fails, as the Sahara is indeed littered with streams and rivers, mostly intermittent, and with small lakes, mostly referred to as “gueltas”. For many years, Henri crossed the Sahara by Landrover during several extended expeditions and published dozens of papers on zooplankton groups, dragonflies and even crocodiles. After his tenure at the Ghent University ended, and he was forced to retire by law, he started a second career as professor at the university of Guangzhou in China, where he taught limnology and guided many students to a quality level that allowed publications in high level scientific journals. This new life, which he greatly enjoyed, was interrupted by the COVID pandemic and, as it turned out later, sadly even put an end to it.

In 1980, Henri became editor in chief of Hydrobiologia, after the untimely death of the previous EiC, Karel Vaas (Anonymous, 1980). He resigned from this position in 2003 (after 23 years!) and in the special volume of Hydrobiologia dedicated to Henri, Martens (2003) outlined the main interests and achievements of Henri’s career at that stage.

Here, in this preface to this “Homage” volume twenty years later, I would like to return to the first editorial that Henri wrote upon his inauguration as successor to Dr Vaas (Dumont, 1981). He started by describing how he met Paul van Oye, the founding editor of Hydrobiologia, in the summer of 1958 when he himself was still a high school pupil. He (Henri) was catching dragonflies at the edge of a bog, where he met the emeritus professor (van Oye), while van Oye was doing some pH measurements, a strange operation that the high school pupil could not identify at that stage. The parallel with my own first encounter with Henri is not completely identical, but still of remarkable coincidence. I did not meet Henri in the field but attended a public lecture on dragonflies by him in the splendid auditorium of the Antwerp Zoo when I was 16 years young. I was fascinated by both the topic as well as by the man. I was already dabbling with the ecology of dragonflies (please do NOT look up the references!) and decided there and then that I would not enter the University of Antwerp for my studies in Biology (although the campus was only 10 min cycling from my parental house), but would go to the University of Ghent, 60 km west of where I lived, and where Henri was a professor. Henri claimed afterwards that he had no recollection of that lecture and blamed that on the consumption of too many Trappist beers, both before and after the event!

However, the outline of his vision as the new editor in chief of Hydrobiologia in that 1981 editorial makes for a very interesting reading, as it shows clearly how Henri already realized then what an international journal like Hydrobiologia required. Firstly, he installed an active and dedicated editorial board, charged with bringing all papers without exception through a thorough (but invariably with positive intend) review process. In his words: “While the editors thus form the backbone of Hydrobiologia, referees are its muscle.” (1981, p. 178). He succeeded in attracting many high-level aquatic ecologists to the editorial board of Hydrobiologia and there is no doubt that the scientific standing and international appearance of this board formed a large part of the success of Hydrobiologia in the two subsequent decades. Incidentally, one small item of his ideas on what the editorial board should look like was not fulfilled: “The average age of the board of editors should not exceed 45 years”! It became clear that an editorial board should have the right balance between young enthusiasm on the one hand and experience on the other, and I am ever so grateful that two members of Henri’s editorial board, Prof Judit Padisák and Prof John Melack, are still part of the present board!

In the same visionary editorial, Henri also outlined the need for a single vehicular language (English) to facilitate communication in the scientific community, as well as the importance of publishing review papers. Henri advocated the publication of specialized symposia in the journal, and it is no exaggeration to say that the standardized publication of the special issues resulting from the symposia on Copepoda, Cladocera, Rotifera and others for many years contributed significantly to the success of Hydrobiologia in the landscape of aquatic ecology publishing. Sadly, the tradition of publishing the papers presented at such symposia in a single proceedings volume has dwindled since then, so that at present, only the Rotifera proceedings still have their traditional place in Hydrobiologia’s portfolio. This, and many other alterations, are the result of the ever (and ever more rapidly) changing landscape of scientific publishing. But let it be known that many of the editorial changes announced by the young editor in chief Henri Dumont, more than 40 years ago, have withstood the test of time.

The present issue contains 13 contributions from Henri’s previous students, past and present colleagues and/or long-time friends and admirers, all in all close to 65 authors. Many others had expressed interest in joining the present honorary issue but could not make it for a variety of reasons. But Henri knows them and appreciates them all. The present papers deal with a plethora of subjects in the many fields of interest of Henri Dumont.

As usual, this Hydrobiologia issue starts with “opinion” and “review” papers. The first (opinion) paper by De Meester et al. holds a plea for a more inclusive approach to zooplankton ecology, and these authors invite freshwater ecologists to look “beyond Daphnia”. Next follow two review papers on novel aspects of zooplankton ecology. The increasing use of molecular techniques has resulted in the discovery of discrete genetic lineages which are morphologically indistinguishable. Kordbachew et al. provide an overview of potential mechanisms of reproductive isolation among such cryptic species in rotifers. Together with the growing application of molecular tools, zooplankton ecology has also seen an increased use of functional traits analyses of aquatic communities, parallel to the more traditional phylogenetic approaches. Wyss Castelo Branco et al. review the application of such functional approaches in the analyses of freshwater zooplankton.

Next follow three further papers on zooplankton ecology. Jeppesen et al. present a fascinating climate-change story on potential succession trajectories in food web structure and composition from older to younger lakes in West Greenland driven by glacier retreat. Xing Rao, together with several students and colleagues from the universities of Guangzhou and Nanjing, where Henri worked after his retirement from Ghent University, investigate if submerged macrophytes facilitate the presence of large crustacean zooplankton in shallow lakes in the tropics. Taranu et al. study the distribution of zooplankton in the St Lawrence River in Québec, Canada.

Two papers on copepods follow. Victor Alekseev performs a classical analysis on the extent to which the modern distribution of two Eucyclops Claus, 1893 species was affected by the evolution of the Tethys Sea. Marrone et al. analyse the role of both spatial and environmental factors as drivers of the distributional patterns of the Diaptomidae in Tunisia.

Returning to Daphnia, Dawidowicz et al. experimentally test the hypothesis that changes in thermal stratification in temperate zone lakes as a result of global warming will cause an increase in fitness cost in species of Daphnia. This is the second paper in this issue, after the one by Jeppesen et al. (see above), demonstrating that freshwater ecology can greatly contribute to the study of the consequences, and possible mitigation, of global climate change.

The next papers deal with aquatic invertebrate groups in which Henri Dumont instigated a great deal of subsequent research through his students or his students’ students. Kafula et al. study the effects of land-use types on community structure of large branchiopods in temporary ponds in Tanzania, while Namiotko et al. investigate environmental correlates of non-marine ostracod assemblages of the Eastern Cape in South Africa. Haltiner et al. deal with feeding responses of zebra and quagga mussels at different temperatures.

It seems fitting to close this special issue of Hydrobiologia, the “Homage to Henri J. F. Dumont”, with an article on dragonflies, the group of aquatic insects that has fascinated Henri from a very early age until the present and which has gone through his life as a scientist as a file rouge! Samraoui et al. report on the endemic species Onychogomphus costae Selys, 1885 in the Ibero-Maghrebian region across an altitudinal gradient.

The colleagues, students, students of students and friends of Henri Dumont, as well as the publishers of Springer-Nature, offer this collection of papers to Henri, at the occasion of his 80th birthday. Many thanks, Henri, for all that you have offered to the world of aquatic sciences!

Note: Full references of the papers in this issue can be found in its table of contents. We no longer cite these papers in the preface in order to limit the journal’s self-citations.