Ancient Philosophy Today

Amphibious plants attract much attention due to their unique ability to live in aquatic and terrestrial environments and sustain abrupt changes of water regime in the habitat. They may colonise habitats with pronounced water level fluctuations and water /dry land interface areas. Water and air differ in many aspects, like density, buoyancy, light and thermal conditions, as well as humidity and diffusion of gases, including oxygen and carbon dioxide, that all affect plant growth and development. The evolution of amphibious plant species resulted in high phenotypic plasticity that is manifested as a variety of ecophenes performing optimally in contrasting conditions. The most important adaptations are heterophylly and/or different life forms that differ at morphological, anatomical, biochemical, and physiological levels. These adaptations comprise the wide span of traits that are found in submerged and terrestrial plant species. The plasticity of amphibious plant species offers a potential to colonise water bodies where hydrology is affected by climate changes and present a unique model system where different scientific aspects of plants may be studied in genetically identical specimens.

Natural freshwater ecosystems, especially ponds, are highly vulnerable to increasing anthropogenic activities and natural alterations owing to their small size and volume. Variations in species diversity, continuous occurrence of harmful algal blooms and changes in aquatic ecosystems are some consequences of the resulting hydrological variations. The trophic state index is one of the easiest and most widely used methods for understanding the trophic status of such disturbed aquatic ecosystems. The present study analysed the variations in different hydrographic parameters with an emphasis on major nutrient status to understand the water quality of two freshwater ponds (S1 and S2) using Carlson's trophic state index (TSI). Assessing the water quality for two years, algal biomass, as indicated by chlorophyll a was maximum during pre-monsoon seasons (S1: 82.08 mg m−3 and S2: 204.97 mg m−3). Dissolved nutrients like nitrate, phosphate and silicate varied from 0.35 mg L−1 to 6 mg L−1, 0.119 mg L−1 to 0.67 mg L−1 and 2.44 mg L−1 to 14.39 mg L−1, respectively, during the study. The TSI result indicated the eutrophic to the hypereutrophic condition in the study area (TSI 71.9 to 82.4). The TSI values reached a maximum at S1 during monsoon 2019, while at S2, the peak value was observed during pre-monsoon 2021. The continuous occurrence of harmful cyanobacterial blooms dominated by Microcystis sp. observed from both freshwater ponds indicated the polluted and deteriorating condition of the ponds.

This study reports the establishment of a population of Quistadrilus multisetosus (Smith, 1900), a new addition to the Slovak fauna, in the Danube floodplain. This finding also identifies the species as a new inhabitant of the Danube river-floodplain system. Its presence in this new area confirms its high potential for dispersal, as previously documented in other European countries. The Danube could therefore serve as the main corridor for the species' spread in this region. Although Q. multisetosus occurs only occasionally worldwide, established populations, as observed in large river surveys, can become very numerous and potentially impact indigenous species communities.

This study assessed the environmental factors underlying the leaf litter decomposition rate in streams in the equatorial rainforest of Cameroon. To reach this goal we used the litterbag method and dead leaves of Funtumia africana (Benth) Stapf (Apocynaceae)in seven natural streams. Concomitantly, we measured biological (fungi and macroinvertebrates) and environmental parameters to highlight those that control the leaf litter breakdown rates. The breakdown rates ranged from 0.035 to 0.056 with an average of 0.042 ± 0.006 in the coarse-mesh litterbags (Kc) and from 0.018 to 0.059 with an average of 0.037 ± 0.01 in the fine-mesh litterbags (Kf). No significant difference was observed between seasons or sites, except for Kf.. As in other tropical rainforests in South America and Asia, the breakdown rates are mainly resulted from microbial activity; the contribution of shredders was negligible, as confirmed by the Kc to Kf ratio and the litter fragmentation rate λF. Among environmental factors, only the distance from the source and the pH were positively correlated with the leaf litter breakdown rates.

Peri-alpine lakes are vulnerable to climate warming. Water temperature in these lakes has increased and will likely continue in the coming decades, questioning the fate of inhabiting aquatic populations. Understanding how coregonine fishes respond to these changes is of great importance as these are economically and ecologically valuable populations. Considering the diversity of European whitefish from the Coregonus genus in peri-alpine lakes, we can assume that their response to rising temperatures could be diverse. We conducted an experiment to explore how embryos from four European whitefish populations from three lakes − Bourget, Geneva, and Constance − responded to contrasting incubation temperatures (7.0 °C vs. 9.0 °C) in terms of incubation duration and survival. In Constance, both pelagic and littoral populations were considered separately. Survival from the eyed-egg stage to hatching at 7.0 °C in all populations was high, ranging from 89% to 98%. At 9.0 °C, increased mortality−compared to the 7.0 °C treatment−was the lowest in Bourget (33%) and the highest in the Constance littoral (62%) population. Mortality was intermediate for the Constance pelagic (44%) and Geneva (45%) populations. The impact of warmer incubation temperature on hatching dynamics also contrasted among populations, as both Constance populations hatched more precociously in the warm treatment relative to the cold treatment (–4.6 and −2.7% Accumulated Degree Days for littoral and pelagic populations, respectively), suggesting they are more stressed than populations from Geneva and Bourget (–1.2 and +1.1%, respectively). These data indicate populations may possess the ability to respond differently to warming temperatures.

Fishes in northern latitude lakes are at risk from climate-induced warming because the seasonality in water temperature is degrading, which can change ecosystem properties and the phenology of life-history events. Temperature-dependent embryo development models were developed for a group of cold, stenothermic fishes (Salmonidae Coregoninae) to assess the potential impacts of climate-induced changes in water temperature on cisco (Coregonus artedi) from two populations in Lake Superior (Apostle Islands [USA] and Thunder Bay [Canada]) and one in Lake Ontario (USA), vendace (C. albula) in Lake Southern Konnevesi (Finland), and European whitefish (C. lavaretus) in lakes Southern Konnevesi, Constance (Germany), Geneva (France), and Annecy (France). Water temperatures for each study group were simulated and changes in reproductive phenology across historic (1900–2006) and three future climatic-warming scenarios (2007–2099) were investigated. Models predicted that increases in water temperatures are likely to cause delayed spawning, shorter embryo incubation durations, and earlier larval hatching. Relative changes increased as warming scenarios increased in severity and were higher for littoral as compared to pelagic populations. Our simulations demonstrated that slower cooling in the autumn and (or) more rapid warming in spring can translate into substantial changes in the reproductive phenology of coregonines among our study groups. We expect that the changes in reproductive phenology predicted by our models, in the absence of thermal or behavioral adaptation, will have negative implications for population sustainability.

Inland fisheries play a crucial role in socio-economic activities and food production. However, these fisheries are often less intensively monitored and studied than marine fisheries. In the past two decades, important fluctuations in European whitefish (Coregonus lavaretus) landings have been observed in four peri-alpine lakes in France and Switzerland. To better gauge the impact of fishing removal, a multi-lakes Delay-Difference model was developed and adapted to these fisheries. A hierarchical state-space Bayesian framework was used to integrate stochasticity for each process and incorporate diverse data. The model gave estimates of time series for biomass, recruitment, stage-structured landings, and fishing mortality, as well as estimates of natural mortality rate, Brody growth coefficient and mean recruitment productivity. Differences in the estimates of variables predicted by the model were observed among lakes. Negative impacts of exploitation have been highlighted for Lakes Geneva, Bourget, and Annecy. Low levels of biomass under high fishing mortality rates were observed, while landings tended to increase under lower mortality rates. Lakes Geneva and Bourget outputs suggest stocks were impacted by fishing activities and that fishing effort reduction could ultimately increase yields. Lake Annecy abundance and landings trends increased after 2010, suggesting management strategies that focused on effort reduction were successful. Lake Neuchâtel stock abundance was low after 2017 and probably more fragile due to low biomass levels and recruitment. The observed changes in European whitefish biomass cannot be attributed solely to fishing, suggesting that environmental factors may also influence recruitment success alongside the impacts of fishing pressure.

In recent decades many lake fish populations have faced complex pressures particularly due to climate warming and eutrophication. In Lake Pyhäjärvi, southwest Finland, profound changes have occurred in the commercial winter fisheries targeting the coregonids vendace, Coregonus albula, and whitefish, Coregonus lavaretus. The responses of vendace have been examined earlier, and here the detailed analyses are extended to the whitefish. In the 1970s and 1980s, the coregonid fishery was sustainable, but in 1991–1998, intense exploitation led to recruitment overfishing of vendace. Despite temporarily improved growth and recruitment of whitefish during vendace decline, whitefish population biomass declined throughout the study period, while perch (Perca fluviatilis), roach (Rutilus rutilus) and ruffe (Gymnocephalus cernuus) increased and vendace and smelt (Osmerus eperlanus) maintained their abundance. As many other northern lakes, Pyhäjärvi seems to be changing from coregonid to perch dominance due to climate warming and eutrophication. Whitefish decline was associated with decreases in fecundity, winter survival of embryos, and larval density. The spawning stock was kept small by intensive fishery. The decline of the relative fecundity was likely due to food competition with vendace and especially the perch and roach populations that increased with eutrophication and more frequent hot summers. The winter survival of whitefish embryos decreased when the introduced signal crayfish (Pacifastacus leniusculus) increased. Despite decreasing fishing effort in the 2000s the larval numbers continued to decline. In the prevailing circumstances in Pyhäjärvi, whitefish will with high probability remain as a minor and still declining species of the fish assemblage.

The vital rates related to reproduction and survival dictate the resistance and persistence of a population under perturbations. Freshwater fishes perform high levels of phenotypic plasticity thus these rates may differ widely between populations and temporally within a population. Knowledge of their ranges enables understanding the scope of population persistence and predicting the effects of environmental stressors. Time series of vendace (Coregonus albula) catch samples from 22 lakes were applied to estimate the lake-specific average length-at-age and survival in mature age groups (mS). Assuming an age-at-maturity of 2 yr and a constant length–fecundity relationship, survival from spawning to age 1 (firstS) and 2 (premS, prematurity survival) were estimated using a life table assuming a stable state. The average length at age 2 yr (L2) varied two-fold between populations, <100 – > 200 mm, and the estimated fecundity approximately eight-fold. Also, mS varied considerably, <10–70%a−1. L2 and mS were positively associated. The premS estimate varied ∼30-fold among lakes, <0.01 – > 0.2% per 2 yr, being highest in populations with low L2 and fecundity combined with low mS. The range of firstS estimate was even higher, 0.01–2%. This high between-lake variability seems to occur especially after hatching during the first summer. Its level is set by the factors external to the population, e.g., the abundance of key predators. Persistence with low early life survival is possible because of the wide scope of compensation in the size- and fecundity-at-age and mS. Early life survival is expected to decrease due to climate change while the compensation has its limits, increasing the risk of local extinctions.

Survival rate of the larval stage is an important driver of fish recruitment. To understand mechanisms regulating larval survival it is important to understand the relative importance of abiotic and biotic factors that shape larval spatial distributions. We studied larval Coregonus distributions in surface waters (surface to 1 m) by repeatedly sampling study sites in two lakes that varied greatly in trophic state and regional climate. We evaluated the importance of bathymetric depth, Julian Day, edible zooplankton densities (EZ, ind. L−1) and wind vectors on larval spatial distributions using generalized additive modeling. In both systems, larval counts declined in a negative exponential fashion with bathymetric depth, indicating shallow depths are critical nursery habitat. The north-south wind vectors and Julian Day (which was positively correlated with surface temperature) influenced larval distributions in Lake Geneva with larval counts related to both variables linearly, whereas the east-west wind vector and EZ were unimportant. Highest larval counts were during an offshore south wind and declined slightly with Julian Day. In Lake Superior, bathymetric depth and the east-west wind vector influenced larval distributions and were unrelated to EZ, Julian Day, and the north-south wind vector. Larval counts were highest when onshore southwest winds preceded sampling. Differences in how wind affected larval distribution (offshore vs. onshore) might be related to larval size with Lake Superior larvae considerably smaller (average length 12.9 mm vs. 15.9 mm); thus, more apt to be subjected to advection. Within coastal waters, Julian Day and wind vectors influence distributions, but their importance seemingly varies lake-to-lake.

Lakes provide ecosystem services such as water resources, tourism, biodiversity, and fishing, and therefore their management represents important societal challenges. Since the early 1960s, significant anthropogenic pressures (human population growth and industrial and agricultural development) have accelerated the degradation of lake ecosystems, leading to eutrophication and subsequent increased sedimentation on fish spawning grounds and decreased dissolved oxygen concentrations. This negatively affects the natural recruitment of whitefish (Coregonus lavaretus), an emblematic species of peri-alpine lakes. Over the years, such processes have resulted in a decline in the whitefish population stock, thereby leading to a drastic drop in catch and causing major economic losses. From the beginning of the 1980s, alongside the restoration of water quality, professional fishers, recreational anglers, state services, and researchers from INRA worked together to develop an applied research program called ‘Pacage Lacustre’ to improve and optimise salmonid stocking. The goal was to counterbalance the low juvenile natural recruitment and maintain whitefish populations. Here, we retrospectively retrace the key stages of this research program and its main impacts on society. Collaborative efforts played a key role in rehabilitating whitefish populations in lakes Geneva and Bourget, particularly when their abundances were the lowest. Therefore, these efforts had a substantial impact on preserving commercial and recreational fishery activities, in addition to favorable societal impacts, highlighting the importance of such collaborative work.

The Detroit River connects Lake Huron and Lake Erie of the Laurentian Great Lakes. The river once supported a substantial lake whitefish (Coregonus clupeaformis) fishery until the early 1900s, when habitat loss, pollution, and overfishing contributed to the collapse of the fishery and loss of spawning populations in the river. In the early 1970s, efforts were initiated to improve water and habitat quality, and in December 2005 a spawning male lake whitefish and viable eggs were collected; the first documented evidence of spawning since 1916. Researchers have tracked the spawning magnitude of the lake whitefish population in the Detroit River since 2005 by assessing the number of eggs deposited on egg mats. Genetic analysis of larval fish hatched from eggs collected in the field between 2005 and 2018 was used to determine the relative contributions of Lake Erie and Lake Huron to the resurging population. Over 80% of the hatched larvae had parents originating from Lake Erie in all the years sampled. The estimated number of full-sibling families sampled at Belle Isle was the same in 2010 and 2014 and varied between 2009 and 2016 at Fighting Island. The estimated number of lake whitefish parents at Fighting Island decreased in the most recent collections possibly due to loss of habitat on spawning reefs due to sedimentation. Our results provide additional evidence that restored spawning habitat in the Detroit River is again being used by lake whitefish and continued reproduction at these sites may improve the Great Lakes portfolio of ecological and genetic diversity.

Alpine (high mountain) ecosystems with extreme weather conditions and complex karstic geology, hosting extensive aquifers, are the two main characteristics of Taurus Mountain ranges, also affecting the distribution of living biota. Understanding these systems are important since they are potentially diverse but poorly explored habitats and are possible water source in the region, especially considering projected further aridification trends. Here, Lake Yeşilgöl (altitude 1815 m asl), a groundwater fed karstic lake at Mount Akdağ, is described in terms of its physical limnology and benthic freshwater ostracod assemblages for the first time. Three freshwater (podocopid) ostracod species were recorded: Fabaeformiscandona brisiaca (Klie, 1938), Neglecandona neglecta (Sars, 1887) Krstić, 2006 and Ilyocypris bradyi Sars, 1890 in the surface sediment. Ostracods are in high abundance. According to the population structure of those species, I. bradyi Sars, 1890 and N. neglecta (Sars, 1887) Krstić, 2006 are inhabiting this lake. Although F. brisiaca (Klie, 1938) is the most abundant ostracod species, it might be distributed/transported to the lake via groundwater. F. brisiaca (Klie, 1938) is the first record form Turkey and might be part of the meio-fauna of karstic groundwater of Taurus Mountains. Trace metals (Pb, Zn, Cd, Cu, and Ni) were measured in the surface sediment of the main lake basin and in the subsamples of the littoral short core. They are detectable low concentration. Atmospheric contamination does not yet appear to be an environmental threat at this remote alpine site in Western Taurus Mountains, in the south west Anatolia.

Lake whitefish (Coregonus clupeaformis) are ecologically, economically, and culturally significant across their range, yet little is documented about the species’ spawning behaviour. Here, we used a VEMCO Positioning System (VPS) and the local ecological knowledge of Saugeen Ojibway Nation in a Two-Eyed Seeing approach to characterize sex-specific movement patterns of lake whitefish at a spawning shoal in Georgian Bay, Lake Huron (Ontario, Canada). In fall 2020, 50 lake whitefish were tagged with acoustic transmitters and 28 of those fish were detected during the deployment of the VPS between 15 October 2021 and 18 January 2022. Occupancy of lake whitefish on the VPS followed a bell-shaped pattern, with an increase, plateau that lasted ∼1 week, and subsequent decrease in activity over a 48-day period demarcating the 2021 spawning season. Apart from 2 resident females, males appeared in the area first. Both sexes moved into shallower lake depths at night and deeper depths during the day. Females moved 18.0% faster than males during the day whereas males moved 39.5% faster than females at night. Depths occupied became shallower over time until the peak activity phase, followed by a transition back to deeper waters. Both sexes used a variety of habitats over the spawning season, including the main spawning shoal, sandy substrates, and steep slopes. These insights on the habitat usage and spawning phenology of lake whitefish provided through our Two-Eyed Seeing approach can help inform stewardship initiatives aimed at increasing recruitment of depleted populations of this important species.