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Research advances emerging from SEFS11: The 11th Symposium for European Freshwater Sciences

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Research advances emerging from SEFS11: The 11th
Symposium for European Freshwater Sciences
Editorial to the Special Issue in Fundamental and Applied Limnology
Isabel Pardo
1, Rachel Stubbington
2, Scott D. Tiegs
3 and Anne Robertson 4
Introduction
This Special Issue of Fundamental and Applied Lim-
nology shares research presented at the 11th Sympo-
sium for European Freshwater Sciences (SEFS11),
which was organized by the Croatian Association of
Freshwater Ecologists in Zagreb, Croatia, from 30
June to 5 July 2019. Building on a 20-year tradition,
the goal of this international conference was to bring
together freshwater scientists from across and beyond
Europe to share emerging knowledge, exchange the
newest research advances and have productive scien-
tific discussions – while also enjoying the hospitable
atmosphere. SEFS11 welcomed contributions from
both early career researchers and established scien-
tists, and provided many networking opportunities
that created new collaborations to support the next
generation of freshwater scientists. The conference at-
tracted participants from a breadth of complementary
disciplines, enabling the development of innovative,
interdisciplinary approaches that transcend boundaries
within freshwater research.
More than 450 delegates from 41 countries partici-
pated in the meeting. Most travelled from within Eu-
rope, with important representation from other coun-
tries including the USA, Australia, Canada and China,
and countries within South and Central America and
Africa (Sertić Perić et al. 2019). Four plenary lectures,
23 regular sessions, 11 special sessions, seven work-
shops and a taxonomy fair were delivered. In total
321 oral and 126 poster presentations were delivered,
and this Special Issue includes the research shared in
nine of them. The studies report a wide range of topics
within freshwater science, including hydrochemistry,
species and habitat conservation, primary and second-
ary production dynamics, structural and functional
community responses to disturbances, and biotic reg-
ulation of nutrient cycling. These papers have com-
mon strengths including the analysis of long-term data
to support conservation and management strategies
in changing European climates (Carosi et al. 2020;
Maximov et al. 2020; Vurnek et al. 2020), and use of
both traditional and genetic identification methods to
characterize biodiversity – again supporting species
conservation, in particular within the protected waters
of the SEFS11 host nation, Croatia (Buj et al. 2020;
Ivić et al. 2020; Piria et al. 2020). Other studies bring
new insight into structural and functional inverte-
brate responses to disturbance (Lencioni et al. 2020;
Šumanović et al. 2020), and Zandonà et al. (2020) are
unique in exploring the stoichiometry of nutrient ex-
cretion by consumers with contrasting diets and body
elemental composition. Below we briefly summarize
each of these papers, which collectively make a sig-
nificant contribution to freshwater science.
E
© 2020 The authors
DOI: 10.1127/fal/2020/1379 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany, www.schweizerbart.de
Authors’ addresses:
1 Department of Ecology and Animal Biology, University of Vigo, Vigo, Spain
2 School of Science and Technology, Nottingham Trent University, Nottingham, UK
3 Department of Biological Sciences, Oakland University, Rochester, MI, USA
4 Department of Life Sciences, Roehampton University, London, UK
Fundam. Appl. Limnol. 194/3 (2021), 151–154 Open Access Editorial
published online 4 December, published in print January 2021
152 I. Pardo, R. Stubbington, S. D. Tiegs and A. Robertson
Analysis of long-term data to support
species and habitat conservation
Three papers use insights from long-term datasets to
advance our understanding of freshwater ecosystems.
Vurnek et al. (2020) analyse long-term trends in water
quality of springs, streams and cascading lotic habitats
in the karstic Plitvice Lakes National Park, Croatia. At
weekly intervals for 12 years (2006–2017), the phys-
icochemical parameters that influence tufa deposition
were recorded, revealing increasing interannual trends
in dissolved oxygen, conductivity, water hardness, al-
kalinity, chemical oxygen demand and nitrites, whereas
temperature, pH and most nutrients (nitrates, ammo-
nia and orthophosphates) decreased. The long-term
analyses of spatial and temporal variability indicated
annual fluctuations in hydrochemistry, correlations
between hydrological and physicochemical variables,
and differences among habitat types – despite which,
tufa deposition processes were stable. The decreasing
temperatures represented springs and streams but not
cascading habitats and contrasted with increasing re-
gional air temperatures, indicating the need for further
research. Vurnek et al. (2020) highlight the value of
insights gained from long-term, continuous monitor-
ing data in planning of future ecosystem management
in a context of ongoing climate change.
Second, Carosi et al. (2020) examine the effects
of an exceptional drying event on the population of
Chirocephalus marchesonii (Anostraca: Chirocephali-
dae), a fairy shrimp endemic to a single, temporary,
high-elevation lake in the Central Apennines, Italy. By
analysing an air temperature data series spanning 67
years from 1951 to 2018, Carosi et al. (2020) iden-
tified higher temperatures as the key driver of water
loss, refuting a previous hypothesis that hydrogeologi-
cal alteration triggered by a strong earthquake caused
the lake to dry. Although C. marchesonii population
densities were lower after the drying event, Carosi et
al (2020) provide convincing evidence that the spe-
cies completed its life cycle. This knowledge is crucial
to inform extinction risk assessments and associated
management strategies that support the persistence of
this threatened endemic species, despite the vulner-
ability of its sole habitat to anthropogenic pressures
including climate change.
Finally, Maximov et al. (2020) analysed long-
term monitoring data from a small oligotrophic lake in
northwestern Russia, comprising biological (benthic
macroinvertebrate communities) and meteorological
(air temperature, precipitation) data collected between
2002 and 2017, as well as 2002–2009 chlorophyll-a
data first published by Maximov et al. (2009). Lagged
positive correlations were identified between winter
temperatures and chlorophyll-a concentrations, and
these climate-driven changes in primary production
were in turn positively correlated with benthic macro-
invertebrate biomass in littoral sediments, suggesting
winter temperatures as a key control of interannual
community dynamics. However, benthic communi-
ties inhabiting different lake depths showed contrast-
ing responses to climatic variability, leading Maximov
et al. (2009) to suggest intra- and interspecific biotic
interactions as important regulators of sublittoral and
profundal communities. In addition, abiotic controls
were locally important influences on benthic commu-
nities, with oxygen depletion linked to low biomass at
the deepest site in late winter.
Fish diversity and distribution in the
Danube River basin
Three papers explore the biodiversity, habitat prefer-
ences, distribution, and population status of fish spe-
cies in the Danube River basin in Croatia, including
both native and non-native invasive species. Buj et al.
(2020) used both morphological and genetic analyses
to determine the taxonomic identity of loaches (Cy-
priniformes: Cobitidae) in the Plitvice Lakes National
Park. Previous research has suggested Cobitis elonga-
toides as the sole loach in these waters, but Buj et al.
(2020) identified one species from each of two genera,
neither of which has previously been reported in the
Plitvice Lakes: C. bilineata and Sabanejewia larvata.
As a result of this study, both are now listed as Natura
2000 target species for the National Park, to promote
their protection (Kovačević, 2019). For both fish spe-
cies, gene sequences were sufficiently different from
Italian populations to suggest their natural coloniza-
tion (via an undetermined pathway), rather than an-
thropogenic translocation.
With insights again supported by genetic analyses,
Ivić et al. (2020) resolved taxonomic controversies re-
garding the diversity and structure of trout populations
(Salmo sp., Cypriniformes: Salmonidae) within the
Žumberak-Samoborsko Gorje Nature Park, Croatia.
Specifically, Ivić et al. (2020) analysed the distribu-
tion, taxonomic status, intrapopulation diversity and
effective population sizes of all species within the ge-
nus Salmo. Phylogenetic reconstruction revealed three
evolutionarily independent and genetically distinct
lineages, characterized by 26 haplotypes. Most sam-
ples and haplotypes belonged to the native S. labrax,
153Editorial to the 11th Symposium for European Freshwater Sciences SEFS11
contributing to the moderately high genetic diversity
of this species, which is widespread in the park. Ivić
et al. (2020) also found haplotypes of non-native S.
trutta and S. marmoratus, and native trout populations
may be threatened by these non-native species, as well
as habitat fragmentation and other anthropogenic pres-
sures. The new insights from this study will thus sup-
port the setting of conservation priorities in this pro-
tected area.
Finally, Piria et al. (2020) used monitoring data
collected across 108 sites on the Croatian Danube and
its tributaries between 2014 and 2018 to determine
the current distribution of the invasive Ponto-Caspian
racer goby, Babka gymnotrachelus (Cypriniformes:
Gobiidae). Piria et al. (2020) found 72 gobies includ-
ing 61 juveniles, indicating the establishment of a self-
sustaining population in the Croatian Danube main-
stem and one of its tributaries, the Baranjska Karašica
River. However, no individuals were recorded in the
Drava and Sava Rivers, which are considered to be
key invasion routes for Ponto-Caspian gobies. Piria et
al. (2020) thus call for future surveys to focus on po-
tentially suitable habitats in the region, to confirm the
species’ current distribution and to better understand
the factors influencing its invasion success.
Structural and functional responses to
disturbance
Two papers examine the functional responses of
stream macroinvertebrates to contrasting environ-
mental disturbances: shrinking alpine glaciers and
hydromorphological degradation. First, Lencioni et
al. (2020) used a combined structural and functional
approach to investigate macroinvertebrate communi-
ties in Italian Alpine streams fed by shrinking glaciers
and comparable non-glacial tributaries. Nine stream
sites (five kryal, two glacio-rhithral and two krenal)
and one proglacial pond were sampled in 2018, and
eight sites had also previously been sampled between
1996 and 2014. Community composition was charac-
terized in relation to environmental variables indica-
tive of glacial influence, including water temperature
and substrate stability. Both taxonomic diversity (as
the Shannon index) and functional diversity (based on
functional feeding groups) increased with decreasing
glacial influence. Temporal changes in taxa distribu-
tion and community structure between 2018 and ear-
lier years were also explained by environmental varia-
bles indicative of glacial influence. Notable changes in
community composition over the 22-year study period
reflected the loss of strict kryal species such as the chi-
ronomid Diamesa steinboecki (Diptera: Chironomi-
dae) and upstream migration of generalist insects, with
consequent changes in food web structure. Lencioni et
al. (2020) thus suggest D. steinboecki as a ‘flagship’
species of kryal Alpine streams: a species that may be
lost as sites pass ‘tipping points’ in response to rapid
global warming.
Secondly, Šumanović et al. (2020) studied macro-
invertebrate communities in 40 streams across a gradi-
ent of hydromorphological degradation in the Medi-
terranean part of Croatia. Reproductive strategies,
functional feeding groups and substrate preferences
were used to characterize functional community re-
sponses. Of two feeding groups, shredders were more
affected by hydromorphological alteration than filter
feeders, indicating the latter’s higher tolerance of an-
thropogenic impacts. Smaller taxa with faster repro-
ductive cycles were also relatively tolerant of hydro-
morphological degradation. Third, reduced substrate
heterogeneity in degraded habitats decreased the oc-
currence of taxa favouring uncommon substrate types.
These results allow Šumanović et al. (2020) to suggest
that functional responses could complement current
taxonomic approaches to macroinvertebrate-based
bioassessment, and could also improve understanding
of the mechanisms driving taxonomic responses.
Faunal contributions to nutrient bio-
availability
Zandonà et al. (2020) make a unique contribution to
this Special Issue by investigating how different fresh-
water faunas influence the bioavailability of inorganic
nutrients. Studying a tropical stream in Brazil, Zan-
donà et al. (2020) are also our only Special Issue con-
tribution from beyond the European continent. Here,
excretion rates of nitrogen (N) and phosphorus (P)
were determined for decapod shrimps and ray-finned
fish, which have contrasting diets and body elemen-
tal composition. Zandonà et al. (2020) predicted that
fish would excrete less P and have higher N:P ratios,
due to the role of P in bone growth and maintenance.
In contrast, shrimps and fish had comparable P ex-
cretion rates, and the N:P excretion ratio was high-
est for the herbivorous shrimp, Potimirim brasiliana
(Decapoda : Atyidae). These results also indicate that
diet was a poor predictor of nutrient excretion rates,
which should be lower for organisms with nutrient-
poorer diets, i.e. for herbivores compared to omni-
vores. Based on these differences between predicted
154 I. Pardo, R. Stubbington, S. D. Tiegs and A. Robertson
and observed patterns, Zandonà et al. (2020) suggest
that factors other than bone tissue investment and diet
affect consumer excretion rates, with consumption
rates, assimilation efficiency, metabolic requirements
and taxon-specific physiological mechanisms identi-
fied as potential controls.
Summary
Contributions to this Special Issue highlight the vi-
brancy of research activity within freshwater sciences
across and beyond Europe. Much of the research pre-
sented focuses on freshwaters of conservation interest,
from those within protected national parks (Buj et al.
2020; Ivić et al. 2020; Vurnek et al. 2020) to those
in vulnerable areas of the Alpine region (Carosi et al.
2020; Lencioni et al. 2020). As European freshwaters
continue to respond to climate change and other an-
thropogenic pressures, such research will underpin
effective monitoring and management strategies that
support biodiversity within functional ecosystems
(Markovic et al. 2017). Conferences such as SEFS11
are vital opportunities to share such research, and to
embark on new collaborations that seek to safeguard
European freshwaters. As the editors of this exciting
volume of Fundamental and Applied Limnology, we
therefore thank SEFS11 organizers including Mirela
Sertić Perić and Marko Miliša, as well as Andreas
Naegele for his considerable editorial support dur-
ing preparation of this Special Issue. We hope that the
papers herein will guide and inspire future research
activity spanning multiple scientific disciplines, as
well as informing effective management of European
freshwater ecosystems.
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Manuscript received: 20 November 2020
Revisions requested:
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Manuscript accepted: 20 November 2020
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Article
Full-text available
Aquatic animals provide nutrients, mostly nitrogen (N) and phosphorus (P), to the ecosystem through excretion of metabolic waste. Excretion rates of N and P are determined by physiological requirements and diet intake and can be affected by several factors, such as body size, resource acquisition, and body elemental composition. Here, we investigated if diet and body elemental composition affect excretion rates in two taxa, shrimp and fish, which differ greatly in their elemental content. Shrimp and fish are often very abundant and can be major mineralizers in oligotrophic tropical streams. We measured per capita and mass-specific excretion rates of ammonium (NH4 +-N) and soluble reactive phosphorus (SRP) of two fish (Bryconamericus microcephalus and Characidium japuhybense) and two shrimp species (Macrobrachium olfersii and Potimirim brasiliana) from a Brazilian stream. We hypothesized that fish, due to their higher P demand (because of their bony structure), excrete less P and higher N:P ratios compared with shrimp. Contrary to our expectations, fish and shrimp did not differ in their mass-specific SRP excretion rates even if fish had higher body %P. The N:P excretion ratio did not follow ecological stoichiometry predictions either, as the species with the highest N:P excretion ratio was the herbivorous shrimp P. brasiliana and the other three species did not differ between each other. Diet was not a good predictor either, as excretion rates of both N and P did not reflect the species trophic position (e.g. the herbivorous shrimp had higher per capita N excretion rates than the omnivorous shrimp). Our results suggest that factors other than bone tissue investment and diet are affecting consumer excretion rates. Consumption rates, assimilation efficiency, metabolic requirements and taxa-specific physiological mechanisms could be having a major role in controlling excretion rates of our studied species. More field studies on diverse taxa and controlled laboratory experiments are necessary to understand the relative roles of different factors in regulating excretion rates.
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During recent intensive research, monitoring and inventory programmes in the large, inland waters of Croatia, 72 specimens of the racer goby Babka gymnotrachelus were collected at eight locations in 2016 and 2018, and of these, 61 were juveniles. This confirms the establishment of a self-sustaining population in the main channel of the Danube in Croatia, and a small tributary, the Baranjska Karašica River. However, no progress of this species in the main tributaries, i.e. the Drava and Sava Rivers, has been observed to date. Future research should be focused on tributaries, channels and backwaters to confirm their localization only to the Danube River and its northwestern tributaries in Croatia.
Preprint
The status of glaciers is alarming globally with still unknown effects on freshwater ecosystems. The general aim of this study was to investigate the structural and functional changes in the macroinvertebrate community in stream networks fed by shrinking glaciers in relation to environmental variables. Feeding glaciers had different surface areas and retreating rates. We selected 10 study sites in the Italian Alps, spanning five kryal, two glacio-rhithral, two krenal and one proglacial pond, sampled twice in summer 2018. Eight of these sites were sampled previously between 1996 and 2014. In all, in 2018, > 15,000 individuals (73 taxa) were collected, of which 82 % were chironomids (Diptera Chironomidae) (33 taxa). Diamesa zernyi gr. (Chironomidae Diamesinae) was the most frequent and abundant taxon, followed by Oligochaeta and Chironomidae Orthocladiinae. Taxonomical (Shannon index) and functional (based on functional feeding groups) diversity both increased with decreasing glacial influence (estimated as glacial index, GI, based on distance from the glacier snout of each site and glacier area), from kryal to glacio-rhithral and krenal habitats. Taxa distribution was explained mainly by GI, maximum water temperature, substrate stability, silica, epilithic chlorophyll-a, and benthic particulate organic matter. The same variables explained temporal differences in the community structure for the eight sites re-sampled in the last two decades. Among the taxa best associated with high GI was the chironomid Diamesa steinboecki, that in 2018 was exclusive of the kryal sites with GCC (% glacier cover in the catchment, expressed in a range from 0 %–100 %) > 50 % and maximum temperature < 5 °C. This species was absent only in the kryal site C0 (GCC = 33 %), where it was dominant in 1996 –1997. This site was still fed by ice melt in 2018, but resembled a glacio-rhithral site in habitat features (e.g. maximum temperature > 6 °C) and biota (e.g. % Diamesa spp. < 30 %). In C0, it was evident that in the last 22 years, the macroinvertebrate community changed remarkably. This change was due to upstream migration of generalist insect species to sites once exclusive for kryal species with consequent changes in food web structure and loss of strictly kryal species, first D. steinboecki that we propose as the “flagship” species of the kryal in the Alps. The site C0 represents a “tipping point”, showing us the effects of climate change on alpine biodiversity in a relatively short period; unfortunately, there are many such sites in the Italian Alps.
Article
Plitvice Lakes National Park, the most famous national park in Croatia, is located in the karstic region ofCroatia, but belongs to the Black Sea watershed. Its ichthyofauna is mostly comprised of Danubian elements and itwas not considered to comprise any endemic species. Although representatives of the family Cobitidae (loaches) werereported for Plitvice Lakes in some older reports, they were usually identified as Cobitis elongatoides. Here, we reporta more detailed analysis (on morphological, as well as molecular genetic level) of loaches from the Plitvice Lakes. Surprisingly,all analyses conducted confirmed that they actually belong to two species in two different genera that werepreviously never reported outside the Adriatic watershed: C. bilineata and Sabanejewia larvata. Both species have restricteddistribution ranges: S. larvata was thought to be distributed only in Italy, while the proposed distribution rangeof C. bilineata comprised Italy, Slovenia, Croatia, Switzerland and France. Since this is the first record of S. larvatain Croatia and the second for C. bilineata (previously it was known only from the Zrmanja River in Dalmatia), bothspecies are now listed as Natura 2000 target species for Plitvice Lakes National Park in order to ensure their adequateprotection. Interestingly, although sequences of both species are similar to Italian C. bilineata and S. larvata, they arenot the same (with the exception of one S. larvata haplotype), opposing the hypothesis of anthropogenic translocation.
Article
Climate change is expected to exacerbate the current threats to freshwater ecosystems, yet multifaceted studies on the potential impacts of climate change on freshwater biodiversity at scales that inform management planning are lacking. The aim of this study is to fill this void through the development of a novel framework for assessing climate change vulnerability tailored to freshwater ecosystems. The three dimensions of climate change vulnerability are: 1) exposure to climate change; 2) sensitivity to altered environmental conditions; and 3) resilience potential. Our vulnerability framework includes 1,685 freshwater species of plants, fishes, molluscs, odonates, amphibians, crayfish and turtles alongside key features within and between catchments, such as topography and connectivity. Several methodologies were used to combine these dimensions across a variety of future climate change models and scenarios. The resulting indices were overlaid to assess the vulnerability of European freshwater ecosystems at the catchment scale (18,783 catchments). The Balkan Lakes Ohrid and Prespa and Mediterranean islands emerge as most vulnerable to climate change. For the 2030s, we showed a consensus among the applied methods whereby up to 573 lake and river catchments are highly vulnerable to climate change. The anthropogenic disruption of hydrologic habitat connectivity by dams is the major factor reducing climate change resilience. A gap analysis demonstrated that the current European protected area network covers less than 25% of the most vulnerable catchments. Practical steps need to be taken to ensure the persistence of freshwater biodiversity under climate change. Priority should be placed on enhancing stakeholder cooperation at the major basin scale towards preventing further degradation of freshwater ecosystems and maintaining connectivity among catchments. The catchments identified as most vulnerable to climate change provide preliminary targets for development of climate change conservation management and mitigation strategies. This article is protected by copyright. All rights reserved.