The growth of two strains of Pseudochloris wilhelmii, Adriatic strain SAG 55.87 and Mangrove strain SAG 1.80, is compared under different salinities, nitrogen sources and concentrations by a fast 96-well screening method. Cultures were grown in BG11 medium with modifications of nitrogen source (ammonium and nitrate) and nitrogen concentrations (0.3 to 19.2 mM) across salinities ranging from 2 to 24 PSU. Growth was measured by optical density at 690 nm, and specific growth rates were analyzed using a Bayesian generalized additive mixed model to identify optimal conditions. Both strains tolerate a broad range of salinities, but cell density was generally higher with nitrate as a nitrogen source than with ammonium nitrogen. The Adriatic strain showed better growth performance when grown on nitrate, with a mean observed growth rate of 0.143 d-1 and a 1.96-fold increase in OD690. The Mangrove strain showed narrower response and lower mean growth rates on nitrate (0.104 d-1). Overall, both strains showed similar growth performance on ammonium, with comparable mean growth rates of 0.0304 for the Adriatic strain and 0.0358 for the Mangrove strain. The results show high intraspecific variation in tolerance to salinity and nitrogen for P. wilhelmii. This 96-well screening method for microalgae cultivation is a powerful and rapid tool for narrowing down optimal growth conditions, as well as to be used as a guide for a larger-scale setup.

Microalage are broadly recognized as promising agents for sustainable wastewater treatment and biomass generation. However, industrial effluents such as petroleum refinery wastewater (WW) present challenges due to toxic growth inhibiting substances. Three marine microalgae species: Pseudochloris wilhelmii, Nannochloropsis gaditana and Synechococcus sp. MK568070 were examined for cultivation potential in oil refinery WW. Their performance was evaluated in terms of growth dynamics, lipid productivity, and toxicity reduction, with a focus on their suitability for largescale industrial use. N. gaditana demonstrated the highest growth rate and lipid content (37% d.w.) as well as lipid productivity (29.45 mg/(Lday)) with the N-uptake rate of 0.698 mmol/(gday). The highest specific DIN uptake rate was observed inn P. wilhelmii (0.895 mmol/(gday) along with the highest volumetric productivity (93.9 mg/L/day) and WW toxicity removal (76.5%), while Synechococcus sp. MK568070 demonstrated lower performance metrics. A simple numerical model was applied to calculate continuous operation based on empirical results of batch experiments. Sustainability of the microalgae-based WW remediation under the conditions of optimized lipid biomass production was estimated, regarding 2019–2022–2025 cost dynamics. Parameters for optimum open raceway pond cultivation were calculated, and the biomass production accumulation was estimated, with the highest biomass production noted in P. wilhelmii (171.38 t/year). Comparison of treatment costs, production costs and revenue showed that the best candidate for WW remediation is N. gaditana.

The mechanistic approach and the potential predictive power of Dynamic Energy Budget (DEB) models are making this modelling framework increasingly popular in aquaculture management. The potential to mechanistically simulate life-history traits of a species in a changing environment has already been applied to many commercial species, including the New Zealand Greenshell™ mussel Perna canaliculus. However, the previous P. canaliculus model parameterisation, available in the Add-my-Pet (AmP) collection, has been carried out on a limited data set. We used data obtained through targeted laboratory experiments and combined it with literature data, to derive a new version of the model, which included information on additional processes – such as feeding, respiration, and reproduction – and life stages: larvae and adults. We compared the performance of the previous version of the model, termed AmP-2018 with the revised model (AmP-2024), to predict the whole life-cycle of the mussel and life-history traits of interest in the context of aquaculture. The entry completeness score (0−10), which provides an indication of data quality and variety as well as model comprehensiveness and applicability, increased dramatically from 2.5 to 5.5, suggesting P. canaliculus is now the most comprehensively DEB-parameterised bivalve, while the model increased in accuracy of the predictions. The endeavour highlights several conclusions: (i) reliable temperature response data are required to establish the thermal response curve; the presence/absence of this type of data should be taken into account when assessing the completeness of a model and its applicability to predict thermal responses of a species; (ii) species-specific parameter values are preferred over general (higher taxonomic level) specific values, e.g. for tissue organics and water content, as they increase the accuracy of predictions; (iii) data pertaining to laboratory trials and to wild populations both need to be taken into account when calibrating a mechanistic model at a species level; and (iv) calculating energy requirements of any organism, including bivalves, requires data on characteristics and products often overlooked in an experimental setting. We discuss the new version of the model in the context of the knowledge and predictive power potentially gained by adding more information and data during model calibration. The obtained results and conclusions are especially relevant in aquaculture, whether for commercial rearing of mussels, or their potential application in multitrophic aquaculture systems.

The submission was prepared to accompany the publication Haberle, Hackenberger et al. "Effects of climate change on gilthead seabream aquaculture in the Mediterranean" in Aquaculture (https://doi.org/10.1016/j.aquaculture.2023.740052). The simulations source code is available through GitHub repository at: https://github.com/QuantEcoLab/SparusSim_Haberle_et_al_2023 The Zanodo archive contains GeoTIFF images underlying the figures in the publication, with the corresponding description in the Readme file.

We have investigated the changes in the microbial communities on the surface of trout eggs and the skin of adult trout in relation to the presence of Saprolegnia parasitica. This pathogen causes saprolegniosis, a disease responsible for significant losses in salmonid farms and hatcheries. It is known from other disease systems that the host-associated microbiome plays a crucial role in the defence against pathogens, but if the pathogen predominates, this can lead to dysbiosis. However, analyses of the effects of S. parasitica on the diversity, composition, and function of microbial communities on fish skin and eggs are scarce. Thus, we have collected skin swabs from injured and healthy trout (N = 12), which differed in S. parasitica load, from three different fish farms in Croatia (Kostanjevac, Radovan, and Solin), while trout egg samples (N = 12) were infected with S. parasitica in the laboratory. Illumina sequencing of the V4 region of the 16S rRNA marker gene showed that infection with S. parasitica reduced the microbial diversity on the surface of the eggs, as evidenced by decreased Pielou’s evenness and Shannon’s indices. We further determined whether the bacterial genera with a relative abundance of >5.0% in the egg/skin samples were present at significantly different abundances in relation to the presence of S. parasitica. The results have shown that some genera, such as Pseudomonas and Flavobacterium, decreased significantly in the presence of the pathogen on the egg surface. On the other hand, some bacterial taxa, such as Acinetobacter and Janthinobacterium, as well as Aeromonas, were more abundant on the diseased eggs and the injured trout skin, respectively. Finally, beta diversity analyses (weighted UniFrac, unweighted UniFrac, Bray–Curtis) have shown that the sampling location (i.e., fish farm), along with S. parasitica infection status, also has a significant influence on the microbial communities’ composition on the trout skin and eggs, demonstrating the strong influence of the environment on the shaping of the host surface microbiome. Overall, we have shown that the presence of S. parasitica was associated with changes in the diversity and structure of the trout skin/egg microbiome. The results obtained could support the development of new strategies for the management of saprolegniosis in aquaculture.

Rogoznica Lake (RL; “Zmajevo oko”) is a shallow marine body of water that exhibits the physical characteristics of lakes (layer overturn and morphology), estuaries (distinct halocline), and seas (tidal regime). This study addresses the physicochemical stratification of the RL and its evolution over 27 years since the beginning of continuous RL research, in the context of regional climate variability. Stratification dynamics were evaluated from several aspects. First, reduced sulphur species accumulation was noted, which was associated with the anoxic water expansion from the bottom of the lake. Second, the connection of the lake with the sea and its attenuation was observed. These results are supported by the negative correlation between annual precipitation and water column salinity, which shows that the role of atmospheric variability in controlling the stability of the lake has increased. A change in the surface layer warming rate was noted, possibly related to unresolved quasi-decadal climate variability. At the same time, the enhancement of the chemocline is in favour of the reported stagnation of the bottom layer. All results suggest that there is a positive feedback mechanism leading to rapid ecosystem degradation.

Host-associated microbial communities are an important determinant of individual fitness and have recently been highlighted as one of the factors influencing the success of invasive species. Invasive hosts introduce their microbes into the new environment, and then both the host and its associated microbes enter into a series of interactions with the native macroscopic and microscopic biota. As these processes are largely unexplored, we aimed to compare the exoskeletal microbial communities of co-occurring and phylogenetically related crayfish: the native narrow-clawed crayfish Pontastacus leptodactylus and the invasive signal crayfish Pacifastacus leniusculus from the recently invaded Korana River, Croatia. The results of high-throughput 16S rRNA sequencing showed that the exoskeletal microbiome of both species is very diverse, significantly influenced by the local environment and dominated by low abundance bacterial families from the phylum Proteobacteria. Furthermore, the exoskeletal microbiomes of the crayfish species differed significantly in the composition and abundance of Amplicon Sequence Variants (ASVs), suggesting that they are to some extent shaped by species-specific intrinsic factors, despite sharing a common habitat. However, over 95% of the bacterial genera associated with the exoskeleton were detected in the exoskeleton samples of both native and invasive crayfish. We paid particular attention to two known crayfish pathogens, Aphanomyces astaci and Saprolegnia parasitica, and find that both species carry low amounts of both pathogens. On the side, we find that a non-standard ddPCR protocol outperforms standard qPCR test for A. astaci under low concentration conditions. Taken together, our results indicate the possibility of bidirectional mixing and homogenisation of exoskeleton microbiome. As such, they can serve as a baseline in future detangling of the processes that act together to shape the microbiomes of co-occuring native and invasive congeners during biological invasions.

Due to high anthropogenic pressures, science-based coastal management required to ensure the sustainable use of coastal areas highly depends on environmental indicators used for decision-making. In this paper, we argue for the inclusion of Vibrio spp. abundance as a supplemental indicator of water quality for science-based coastal management by examining the environmental and bacterial indicators at a fish farm and a control site in Mali Ston Bay in the Adriatic Sea. Unexpectedly, heterotrophic bacteria, enterococci and Vibrio spp. were more abundant in the cold season, while E. coli and total coliforms, following a more traditional pattern, were more abundant in the warm season. Each of the currently used indicators has a specific purpose: heterotrophic bacteria indicate the presence of both nonpathogenic and pathogenic bacteria, while enterococci are pathogenic bacteria indicating fecal pollution. Vibrio spp. abundance additionally represents a non-fecal bacteria that can cause vibriosis in humans and aquatic organisms. Since vibriosis is the leading cause of disease-related fish mortality in aquaculture, pathogenic Vibrio spp. have large health and economic implications. These implications, as well as the added interpretative value when compared to other bacterial indicators, make Vibrio spp. abundance a good candidate as a water quality indicator. Significant dependence of the abundance on depth further differentiates Vibrio spp. from other indicators, thus bolstering the candidacy - especially in aquaculture areas. Before inclusion of any Vibrio spp. indicators into legislature, further research is needed particularly into (i) abundance thresholds characterizing water quality, and (ii) identification of species whose abundance should be monitored for best estimate of the disease risks.

Two main parameters that structure the marine ecosystem by affecting species distribution, abundance, community structure, timing of major life cycle events, and trophic state of the ecosystem are temperature and nutrient availability. Faced with climate change, eukaryotic plankton cope at multiple levels through physiological accommodation, adaptive evolution, shift in time and/or space of habitat, and/or community responses. Thirty‐two years of our phytoplankton research indicate that Chaetoceros curvisetus / pseudocurvisetus adjust to climate change more successfully than the majority of the accompanying phytoplankton taxa in the mesotrophic part of the NW Adriatic Sea, the Mediterranean. While the abundance of the entire accompanying phytoplankton community has decreased significantly since 2003 (the period of the northern Adriatic warming and oligotrophication) compared to the previous period (1986–2003), the abundance of C. curvisetus / pseudocurvisetus remained unchanged, while its contribution to the community increased significantly. Accommodation strategies include a change in the timing of high abundance and blooms in the surface layer and successful blooming in the deeper layers during warm months. Apart from the observed in situ accommodation, physiological acclimation to warming may involve changes in photosynthesis, respiration, growth, and cell biochemistry. Here, we conducted laboratory experiments with C. pseudocurvisetus to investigate how warming affects its biochemical response through the fatty acid remodeling of phospholipid classes. Long‐term field observations and short‐term laboratory experiments suggest that marine diatoms C. curvisetus / pseudocurvisetus are potential global winners with the ability to acclimate/adapt to climate change.

Aquaculture provides more than 50% of all seafood for human consumption. This important industrial sector is already under pressure from climate-change-induced shifts in water column temperature, nutrient loads, precipitation patterns, microbial community composition, and ocean acidification, all affecting fish welfare. Disease-related risks are also shifting with important implications for risk from vibriosis, a disease that can lead to massive economic losses. Adaptation to these pressures pose numerous challenges for aquaculture producers, policy makers, and researchers. The dataset AqADAPT aims to help the development of management and adaptation tools by providing (i) measurements of physicochemical (temperature, salinity, total dissolved solids, pH, dissolved oxygen, conductivity, transparency, total nitrogen, ammonia, nitrate, nitrite, total phosphorus, total particulate matter, particulate organic matter, and particulate inorganic matter) and microbiological (heterotrophic (total) bacteria, fecal indicators, and Vibrio abundance) parameters of seawater and (ii) biochemical determination of culturable bacteria in two locations near floating cage fish farms in the Adriatic Sea. Water sampling was conducted seasonally in two fish farms (Cres and Vrgada) and corresponding reference (control) sites between 2019 and 2021 of four vertical layers for a total of 108 observations: the surface, 6 m, 12 m, and the bottom.

The microalgae of the genus Pseudochloris/Picochlorum are characterized by fast growth, and wide nutrient (type and concentration) and salinity tolerance, all contributing towards exploration of their use in high-density biomass production and wastewater bioremediation. In this study, removal of nitrogen and phosphorus nutrients from oil refinery wastewater was monitored during growth of the marine eukaryotic microalgae Pseudochloris wilhelmii, with emphasis on biochemical analyses of its biomass quality to evaluate suitability for biodiesel production. A series of growth experiments under various nutrient and light regimes were performed in a temperature range of 20-30°C to evaluate nutrient removal and biomass growth dependence on temperature. The highest removal rate of dissolved inorganic nitrogen reached under the given experimental conditions was 0.823 mmol/(gday) accompanied by the corresponding biomass productivity of 115.2 mg/(Lday). Depending on light and temperature, the final lipid concentration ranged 181.5 – 319.8 mg/L. Furthermore, increase in nutrient load decreased the maximum specific growth rate by 25%, and the maximum specific removal rate of the dissolved inorganic nitrogen by 19%, whereas the duration of bioremediation process was nearly doubled. In contrast, constant light exposure expedited the nitrogen removal, i.e. bioremediation process, by almost 40%, while supporting over three times higher biomass productivity and the highest maximum specific growth rate of 0.528 g/(gday). The conditions favoring the highest nitrogen removal and highest toxicity reduction in oil refinery wastewater are met at 24°C and 130 µmol phot/(m2s). The highest proportion of carbon-binding to the P. wilhelmii biomass was noticed under the same conditions, thus indicating them as the most favorable conditions for hydrocarbon removal as well as for CO2 sequestration. Pseudochloris wilhelmii therefore represents a promising candidate for oil refinery wastewater remediation and valuable biomass cogeneration on a large-scale.

Recent decades have seen a rise in the use of physics methods to study different societal phenomena. This development has been due to physicists venturing outside of their traditional domains of interest, but also due to scientists from other disciplines taking from physics the methods that have proven so successful throughout the 19th and the 20th century. Here we dub this field 'social physics' and pay our respect to intellectual mavericks who nurtured it to maturity. We do so by reviewing the current state of the art. Starting with a set of topics that are at the heart of modern human societies, we review research dedicated to urban development and traffic, the functioning of financial markets, cooperation as the basis for our evolutionary success, the structure of social networks, and the integration of intelligent machines into these networks. We then shift our attention to a set of topics that explore potential threats to society. These include criminal behaviour, large-scale migrations, epidemics, environmental challenges, and climate change. We end the coverage of each topic with promising directions for future research. Based on this, we conclude that the future for social physics is bright. Physicists studying societal phenomena are no longer a curiosity, but rather a force to be reckoned with. Notwithstanding, it remains of the utmost importance that we continue to foster constructive dialogue and mutual respect at the interfaces of different scientific disciplines.

Vibrio spp. have an important role in biogeochemical cycles; some species are disease agents for aquatic animals and/or humans. Predicting population dynamics of Vibrio spp. in natural environments is crucial to predicting how the future conditions will affect the dynamics of these bacteria. The majority of existing Vibrio spp. population growth models were developed in controlled environments, and their applicability to natural environments is unknown. We collected all available functional models from the literature, and distilled them into 28 variants using unified nomenclature. Next, we assessed their ability to predict Vibrio spp. abundance using two new and five already published longitudinal datasets on Vibrio abundance in four different habitat types. Results demonstrate that, while the models were able to predict Vibrio spp. abundance to an extent, the predictions were not reliable. Models often underperformed, especially in environments under significant anthropogenic influence such as aquaculture and urban coastal habitats. We discuss implications and limitations of our analysis, and suggest research priorities; in particular, we advocate for measuring and modeling organic matter.

Lake Rogoznica (also known as "Dragon's Eye") is a karstic, marine lake on the Gradina peninsula located at the Adriatic coast at 43° 32' N and 15° 58' E. Most of the time the lake is stratified, with an upper oxic layer, an anoxic bottom layer, and a chemocline in between. Every few years the stratification suddenly breaks down and the entire water column becomes mixed, anoxic, and euxinic, with HS- presence throughout the water column. This leads to mass mortality of aerobic populations in the lake, which require long periods of time without mixing to recover. Rogoznica residents confirmed that the sudden overturning of layers had been occurring even before continuous research began in 1992, but also that it used to happen less frequently. In the last 30 years, five such events of complete anoxia have been recorded: in September 1997, October 2011, October 2016, October 2020, and October 2021. As the sudden mixing now occurs year after year, the lake's ecosystem does not have nearly enough time to recover. Previous work has indicated that the main trigger for the abrupt mixing is a sudden drop in surface temperature caused by an overpassing low-pressure system. Nevertheless, the process of overturning and sudden release of bottom-layer sulfides is a very delicate one, and determining other biological, physical, and chemical triggers is an important question that remains to be answered. Another key question is whether the increase in the overturn frequency is solely a part of the natural life cycle of the lake, a result of the changing climate with more extreme weather events, or a more direct consequence of human activities in the area.Comparison of the most recent water level measurements from June 2021 with those from 2013 indicate that the tidal signal in the lake requires a somewhat different analytical approach than the standard ocean tidal analysis procedure. Moreover, measurements at the boundaries of the lake show that the water entering the lake from the karst at high tide is not only colder but also has a lower salinity. Additionally, in this work we present new insights into the physicochemical properties of the lake's water column (σT-stratification, dissolved oxygen concentration) and the direct influence of atmospheric wet deposition on the lake's surface layer.

Invasive alien crayfish threaten the diversity of freshwater ecosystems and native crayfish fauna. In Europe, this is largely due to transmission of the crayfish plague to susceptible native crayfish. Many invasive spe-cies tolerate crayfish plague, but the infection still has the potential to reduce the fitness of a tolerant host due to energy trade-offs between immune response maintenance and life-history traits, such as growth and reproduction. In combination with other unfavourable conditions, such a response could alter fur-ther invasion success of an otherwise successful crayfish invader. We examined whether repeated infection with one of the most virulent haplogroups of crayfish plague agent (Aphanomyces astaci) affects growth or survival of the juvenile marbled crayfish (Procambarus virginalis). Juveniles were exposed to i) two levels of pathogen concentrations, and ii) two different feeding regimes under the higher pathogen concentra-tion. In all performed trials, repeated infection reduced growth rates, while the combination of recurring infection and food limitation significantly increased mortality. The average energy cost of the immune response was estimated at 12.07 J/day for individuals weighing 0.3 grams. Since infections were frequent and pathogen concentrations high, results suggest that marbled crayfish is resistant to A. astaci pathogen and its survival is only affected by adding the stress of food limitation. The survival of almost half of the individuals exposed to high pathogen loads and extreme food limitation indicates that chronic infection by crayfish plague is unlikely to be an important factor impeding invasion success of the marbled crayfish, even under harsh conditions. Our results add to the growing body of evidence that marbled crayfish has potential to become one of the most successful freshwater invaders.

Despite the extensive and rapidly growing literature on microplastics in oceans and coastal seas, little information exists on microplastic distribution through the salinity gradient. This study is the first one to evaluate microplastic distribution through the salinity gradient of a highly stratified estuary. A total of 910 microplastic particles were collected from 12 different sampling events in the Krka River estuary, Croatia. The number of detected particles ranged from 389 in the surface layer to 63 in the deepest marine layer. The highest plastic abundance was found in the surface layer (3.68 particles/m(3)) and the lowest in the marine layer (0.13 particles/m(3)). The measured values of the cross-sectional area indicated an ellipsoidal cross-sectional shape of the particles. It was also found that the majority of microplastic particles belonged to the small microplastic class (<1 mm). The Nile Red (NR) staining method was used to visualize fluorescent microplastic particles, while quantification was performed using ImageJ/Fiji software. The strong salinity stratification in the studied estuary did not alter the usual distribution of microplastic particles in the water column, and there was no significant accumulation on the halocline.

Collective risks permeate society, triggering social dilemmas in which working toward a common goal is impeded by selfish interests. One such dilemma is mitigating runaway climate change. To study the social aspects of climate-change mitigation, we organized an experimental game and asked volunteer groups of three different sizes to invest toward a common mitigation goal. If investments reached a preset target, volunteers would avoid all consequences and convert their remaining capital into monetary payouts. In the opposite case, however, volunteers would lose all their capital with 50% probability. The dilemma was, therefore, whether to invest one's own capital or wait for others to step in. We find that communicating sentiment and outlook helps to resolve the dilemma by a fundamental shift in investment patterns. Groups in which communication is allowed invest persistently and hardly ever give up, even when their current investment deficits are substantial. The improved investment patterns are robust to group size, although larger groups are harder to coordinate, as evidenced by their overall lower success frequencies. A clustering algorithm reveals three behavioral types and shows that communication reduces the abundance of the free-riding type. Climate-change mitigation, however, is achieved mainly by cooperator and altruist types stepping up and increasing contributions as the failure looms. Meanwhile, contributions from free riders remain flat throughout the game. This reveals that the mechanisms behind avoiding collective risks depend on an interaction between behavioral type, communication, and timing.

The noble pen shell Pinna nobilis L. is the largest, endemic, critically endangered, and protected bivalve of the Mediterranean Sea. Effective conservation and management strategies for this species highly depend on understanding how environmental change and anthropogenic pressures impact its physiology and thereby ecological function, population persistence, and survival. Dynamic Energy Budget (DEB) theory offers a valuable mechanistic modelling framework for capturing how an organism acquires and utilizes available energy for growth, maturation, development and reproduction throughout its life cycle, while accounting for environmental conditions. In this study we parameterized and compared two types of DEB models using limited literature data: a standard model that accounts for morphological metamorphosis only, and a model that through metabolic acceleration between birth and metamorphosis captures physiological changes occurring in the larval life stage. The model with metabolic acceleration performed better, successfully simulating life history traits, growth, and reproduction of P. nobilis. We used the model to predict how food availability implemented through functional response affects growth, maturation, and reproduction of the species throughout its lifespan. We found that (i) abundant food had little effect on the size at maturation, (ii) maximum fecundity at ultimate age doubled compared to typically lower food availability in the wild, (iii) puberty could not be reached below the food availability corresponding to functional response value of 0.164, and (iv) energy allocated to reproduction was positively correlated with both bivalve size and food availability. Accounting for allometric growth observed in P. nobilis did not affect the findings, prompting us to recommend that isometric growth be assumed when modelling the bivalve using DEB. The model presented here is the first full-life cycle bioenergetic model made for P. nobilis. It can be used standalone for predicting energy budget of individuals at specific environmental conditions, or as a building block for modeling populations and ecosystems under various environmental scenarios. The model can readily incorporate other environmental factors relevant to changes in physiology and energy allocation, such as oxygen and pH.