Increasing Sea Temperatures Research Articles

Haemoglobin revisited: delineating population structure with the world's first molecular genetic marker used in fisheries research.

When haemoglobin genotyping was implemented in the early 1960s to investigate population genetic structure in Atlantic cod (Gadus morhua), it became one of the first molecular genetic markers deployed in fisheries research worldwide. However, its suitability was questioned due to its potential for selection. While the issue of neutrality concerned the first population geneticists, markers under selection are now routinely used to study population genetic structure. Here, we revisited haemoglobin genotyping half a decade later to analyse >6000 mature Atlantic cod from 73 spawning locations throughout Norway's approximately 2500 km coastline. A latitudinal gradient in allele frequencies, with a decrease in the HbI-2 allele towards the south, was observed. Our observed HbI-2 frequencies were consistently slightly lower than data from the 1960s, potentially reflecting adaptive changes to increasing sea temperatures. However, despite this difference, the observed north-south pattern in allele frequencies observed here and in the historical studies overlapped, aligning with current knowledge of population genetic structure in this species. We therefore conclude that this once questioned marker, which provided the first molecular genetic insights into genetic structure in Atlantic cod, provides knowledge consistent with the isolation by distance pattern revealed through decades of research in this species in this region.

Perceptions of Small-scale Fishermen on the Impact of Climate Change in Coastal and Small Island Areas of Pangkajene and Islands Regency

This study examines the perceptions of small-scale fishers in coastal areas and small islands of Pangkep Regency towards the impacts of climate change. The impacts of climate change experienced by fishers include unpredictable changes in weather patterns, increased sea temperatures, and unpredictable fishing seasons, which overall reduce catches and increase safety risks at sea. The research was conducted for 6 months from May to October 2024. The research was conducted in Pangkep District, South Sulawesi. The research location was purposively selected to illustrate the condition of fishermen who are directly affected by climate change. Data collection techniques were conducted through in-depth interviews, direct observation, questionnaires, and literature studies. The number of samples in this study were 50 fishermen with the criteria of small fishermen who have a ship/boat capacity of 0-10 GT. This research used a qualitative approach with a descriptive method. The qualitative approach allows researchers to explore fishermen's subjective perceptions of the impacts of climate change. Most fishers reported a decrease in catches due to changes in fish migration thought to be related to rising seawater temperatures, which forced them to go further out to sea and incur greater operational costs. In addition, climate change is resulting in extreme weather that often poses accident risks for fishers, while limited access to weather information and technology hinders their adaptation. This suggests the need for adaptation policies, such as climate training and improved access to weather information for small-scale fishers, to strengthen their resilience to climate change.

Small-scale Fishermen's Adaptation to Climate Change Impacts in Coastal Areas and Small Islands in Pangkep Regency

Climate change is a global challenge that has significant impacts on the fisheries sector. This phenomenon involves increasing global temperatures, changing weather patterns, rising sea levels, and increasing the frequency and intensity of natural disasters. Climate change not only threatens marine ecosystems but also affects the livelihoods of coastal communities, especially small-scale fishers who depend on fisheries resources for their survival. This study aims to analysis the economic adaptation of small-scale fishers in facing the impacts of climate change. The research was conducted from May to October 2024 in Pangkajene Islands Regency (Pangkep). This research used a descriptive qualitative approach with data collection through interviews, questionnaires, field observations, and literature studies. Respondents in this study were 50 fishermen who were selected purposively. Data analysis used with descriptive qualitative. The results show that climate change has a significant impact on fishing patterns and catches. The increase in sea temperature, high waves, and storms cause a decrease in productivity and increase the risk of damage to fishing gear. In facing these challenges, fishers apply economic adaptation strategies such as livelihood diversification, regulation of fishing period/time, improving fishing technology, changing fishing areas, and strengthening community cooperation. This research recommends strengthening the capacity of fishermen through training, access to microfinance, and development of disaster-resistant infrastructure. The results of this study are expected to serve as a basis for the government and stakeholders in formulating community-based adaptation policies to increase the resilience of small-scale fishing communities to the impacts of climate change.

Evaluating Climate Change Impacts to Qatar’s Marine Life: A Risk Assessment for SDG 14 (Life Below Water)

Marine life is integral to Qatar and the broader Arab region, serving as a cornerstone for biodiversity, economic activity, and cultural heritage. Despite the ambitious targets set by Sustainable Development Goal (SDG) 14, climate change is placing mounting pressure on conservation efforts. Recognizing that climate change cannot be entirely stopped, the focus should be on mitigating its effects through sustainable strategies. This study identifies twelve climate-related risks that impede Qatar's progress towards achieving SDG 14 - Life Below Water. To understand the region-specific climate risks, this study engaged in a focus group discussion with representatives from the government, NGOs, private sector, and academia. The Climate Change Risk Assessment (CCRA) identified the most severe risks as flooding associated with rising sea levels, modified species biogeography, and compromised coral reef health. While other risks were rated low, such as risks to seagrass meadows driven by increasing sea temperatures. Other significant findings include the need for increased awareness of climate change impacts on both the local and global administrative platforms. This risk assessment provides insights into the vulnerable facets of Qatar's marine environment, intending to guide forthcoming strategies for achieving SDG-14.

Impacts of Environmental Change and Microplastic Pollution on Zooplankton

Zooplankton are an important part of the ecosystem, carrying out the function of energy transfer in the food web, linking the lower to the higher trophic levels of species. They are often under the combined influence of the surrounding environment and other aquatic life. This research aims to study the effects of environmental changes, such as changes in the several properties of seawater, microplastic pollution on zooplankton populations and the interactions between other aquatic organisms and zooplankton. The results show that with environmental changes, the increase in sea temperature, pH value, eutrophication of seawater and the increase of microplastic pollution will harm the zooplankton population. At the same time, the size of zooplankton populations can affect the number of fish that feed on them, and the predation of fish can also affect their biomass and population structure. These studies can help humans better understand the mechanisms of ecosystem interactions in nature, assess and predict broader environmental change, maintain healthy ecosystems, and ensure future resource sustainability.

Changes in prey-predator interactions in an Arctic food web under climate change

Global warming affects marine ecosystems by changing environmental conditions, ecosystem structure, and ecosystem functioning. In parts of the Arctic, increased sea temperature and decreased sea ice have led to a poleward expansion of boreal species and increased their interactions with native Arctic species. To investigate and quantify the changing interactions in an Arctic marine food web under new environmental conditions, we studied the interactions between key prey fish species in the seasonally ice-covered parts of the Barents Sea: adult polar cod (Boreogadus saida) and capelin (Mallotus villosus) and one of the major predators in the system: Atlantic cod (Gadus morhua). For this, we compared the predictive performance of threshold models predicting the abundance of adult polar cod as a function of Atlantic cod. Each model was associated with a hypothesis describing prey-predator interactions in different environmental conditions defined by threshold values of summer sea-ice or capelin stock biomass. The best predictive model showed that the predation effect of Atlantic cod on polar cod was strongest in years of low summer sea ice cover and low capelin stock biomass. Our results exemplified that Arctic species such as polar cod may experience increased predation pressure under climate change from boreal species such as Atlantic cod. These effects depend, however, not only on changes in abiotic drivers of species distributions, but also on food-web interactions involving mid-trophic level species such as capelin.

Influence of Sea Surface Temperature Changes on the Development of Sprat (Sprattus sprattus phalericus) (Pisces: Clupeidae) Living on the South-Western Shelf of Crimea

A study of changes in sea surface temperature (SST) on the South-Western shelf of the Crimea in 2000–2020 was conducted. The equations of trends in the change of SST are found. It is shown that according to the nature of changes in the average annual sea temperature, three periods can be divided: 2000–2007, 2008–2013 and 2014–2020. The influence of changes in the average annual SST on the development of pelagic fish of the cold-waters complex (on the example of the Black Sea sprat) is considered. Changes in the main parameters of populations and their relationship with the change in the average annual SST were found. It was found that the observed increase in sea temperature negatively affected the development of the sprat population, the average age of the population decreased by 1.3 times, in general, the population was rejuvenated, the average size and weight of individuals decreased.

Interaction between three key species in the sea ice-reduced Arctic Barents Sea system.

Population dynamics depend on trophic interactions that are affected by climate change. The rise in sea temperature is associated with the disappearance of sea ice in the Arctic. In the Arctic part of the Barents Sea, Atlantic cod, capelin and polar cod are three fish populations that interact and are confronted with climate-induced sea ice reductions. The first is a major predator in the system, while the last two are key species in Arctic and sub-Arctic ecosystems, respectively. There are still many unknowns regarding how predicted environmental change may influence the joint dynamics of these populations. Using time series from a 32 year long survey, we developed a state-space model that jointly modelled the dynamics of cod, capelin and polar cod. Using a hindcast scenario approach, we projected the effect of reduced sea ice on these populations. We show that the impact of sea ice reduction and concomitant sea temperature increase may lead to a decrease of polar cod abundance at the benefit of capelin but not of cod which may decrease, resulting in strong changes in the food web. Our analyses show that climate change in the Arcto-boreal system can generate different species assemblages and new trophic interactions, which is the knowledge needed for effective management measures.

Mass Mortality of the Invasive Sea Urchin Diadema setosum in Türkiye, Eastern Mediterranean Possibly Reveals Vibrio Bacteria Infection

ABSTRACTThe invasive Diadema setosum (Leske, 1778) long‐spined sea urchin has been in the Mediterranean Sea since 2006, and then, it has been known that its population density has reached high values on the southern Aegean coasts of Türkiye. This study aimed to report the mass mortality event of D. setosum with the determined agent on the Aegean coast of Türkiye. In addition, it was targeted to provide information on the current status of its density based on seasonal SCUBA diving observations for the period between January 2023 and November 2023. The results showed that the mass mortality of D. setosum was determined in Muğla, Aegean Sea, in August 2023. Spine loss, the mucoid layer at the bottom of the appendages, and the outer body surface were observed as the clinical symptoms of the diseased samples. Bacterial growth was detected on Vibrio‐selected TCBS agar plates, while no other parasitic agents were determined in the coelomic fluid of sea urchins. The results of the biochemical (API 20E) and molecular tests confirmed the isolated bacteria as Vibrio spp. The density of D. setosum showed statistically significant temporal changes, and the highest and lowest mean density values were recorded in autumn and spring, respectively. Environmental stressors, such as increasing sea temperature levels, affect the marine ecosystem and lead to opportunistic pathogens. Long‐term monitoring of disease outbreaks is necessary to understand the interactions between species and the ecosystem.

Modeling of the habitat suitability of European sprat (Sprattus sprattus, L.) in the Adriatic Sea under several climate change scenarios

The Mediterranean Sea represents the lower latitudinal limit of the European sprat range, where it is considered a sentinel species favoring temperate–cold temperatures. Sprattus sprattus is a plankton feeder that plays an important ecological role in contributing to the transfer of energy from lower to higher trophic levels, but climate-driven increases in sea temperatures may reduce the suitability of the pelagic habitat and threaten the tropho-dynamic role of sprat in areas such as the Adriatic Sea. The latter is an enclosed basin characterized by shallow waters and high annual temperature variations. Here, to investigate present and future habitat suitability areas for sprat, we applied four species distribution models (SDMs) using fishery-independent data collected from 2004 to 2021, along with remotely sensed and modeled environmental variables. A set of nine environmental predictors was tested, and the resulting best model was averaged in an ensemble model approach. The best ensemble models revealed good to high accuracy (sensitivity and specificity ≥ 0.8). The sea surface temperature and chlorophyll concentration emerged as the main explanatory variables in predicting the potential habitat of sprats, followed by bathymetry. The resulting probability of occurrence maps revealed that the species is bounded in the northern Adriatic Sea, where a longitudinal shift of high-suitability habitats from inshore to deeper and colder waters was detected between early and late summer. Future projections under IPCC representative concentration pathway (RCP) scenarios 4.5 (intermediate emission) and 8.5 (high emission-warm) underline small changes along with a gain of new areas in late summer in the short-term period up to 2050. Conversely, the temperature increase projected for the end of the century is predicted to cause a loss of suitable habitat area for sprats of up to 88% under a high emission-warm scenario relative to current habitat occupancy throughout the basin.

Characterization of ascorbate-glutathione cycle response in Zostera marina seedlings under short-term temperature surge

The ascorbate-glutathione (AsA-GSH) cycle plays a critical role in scavenging hydrogen peroxide in plants and contributes significantly to plant stress tolerance. This study examines the cycle’s response in Zostera marina seedlings to warming, specifically under conditions of abnormal sea temperature increase. Three temperature gradients were established: 18°C (control group), 23°C (high-temperature group), and 28°C (abnormally high-temperature group). Results after 7 days of exposure to mild high temperature (23°C) showed decreased MDA content in the HT group, increased AsA/DHA ratio, and enhanced activity of enzymes related to the AsA-GSH cycle. However, exposure to extreme high temperatures resulted in increased oxidative damage and redox imbalance in the AHT group. Initially, enzymes associated with the AsA-GSH cycle, such as APX, MDHAR, GPX, and γ-ECS, increased but significantly decreased later under stress. In contrast, DHAR and GaILDH levels significantly rose on the seventh day. Transcriptome analysis revealed upregulation of APX, MDHAR, DHAR, GR, and γ-ECS genes in the HT group, with a decline in other enzyme gene expressions by the seventh day, except for APX. Under extreme high temperatures, APX expression was downregulated early in the stress period, while DHAR was upregulated, indicating Z. marina seedlings can mitigate oxidative damage under short-term high temperatures by activating the AsA-GSH cycle. Conversely, extreme high temperatures may inhibit this cycle, disrupt redox balance, and adversely affect Z. marina seedling establishment, potentially leading to their demise.

Temperature-driven dynamics: unraveling the impact of climate change on cryptic species interactions within the Litoditis marina complex.

Anthropogenic climate change and the associated increase in sea temperatures are projected to greatly impact marine ecosystems. Temperature variation can influence the interactions between species, leading to cascading effects on the abundance, diversity and composition of communities. Such changes in community structure can have consequences on ecosystem stability, processes and the services it provides. Therefore, it is important to better understand the role of species interactions in the development of communities and how they are influenced by environmental factors like temperature. The coexistence of closely related cryptic species, with significant biological and ecological differences, makes this even more complex. This study investigated the effect of temperature on species growth and both intra- and interspecific interactions of three species within the free-living nematode Litoditis marina complex. To achieve this, closed microcosm experiments were conducted on the L. marina species Pm I, Pm III and Pm IV in monoculture and combined cultures at two temperature treatments of 15 °C and 20 °C. A population model was constructed to elucidate and quantify the effects of intra- and interspecific interactions on nematode populations. The relative competitive abilities of the investigated species were quantified using the Modern Coexistence Theory (MCT) framework. Temperature had strong and disparate effects on the population growth of the distinct L. marina species. This indicates temperature could play an important role in the distribution of these cryptic species. Both competitive and facilitative interactions were observed in the experiments. Temperature affected both the type and the strength of the species interactions, suggesting a change in temperature could impact the coexistence of these closely related species, alter community dynamics and consequently affect ecosystem processes and services.

Ecophysiological responses of Ostreopsis towards temperature: A case study of benthic HAB facing ocean warming

Reports of the benthic dinoflagellate Ostreopsis spp. have been increasing in the last decades, especially in temperate areas. In a context of global warming, evidences of the effects of increasing sea temperatures on its physiology and its distribution are still lacking and need to be investigated. In this study, the influence of temperature on growth, ecophysiology and toxicity was assessed for several strains of O. cf. siamensis from the Bay of Biscay (NE Atlantic) and O. cf. ovata from NW Mediterranean Sea. Cultures were acclimated to temperatures ranging from 14.5 °C to 32 °C in order to study the whole range of each strain-specific thermal niche. Acclimation was successful for temperatures ranging from 14.5 °C to 25 °C for O. cf. siamensis and from 19 °C to 32 °C for O. cf. ovata, with the highest growth rates measured at 22 °C (0.54–1.06 d−1) and 28 °C (0.52–0.75 d−1), respectively. The analysis of cellular content of pigments and lipids revealed some aspects of thermal acclimation processes in Ostreopsis cells. Specific capacities of O. cf. siamensis to cope with stress of cold temperatures were linked with the activation of a xanthophyll cycle based on diadinoxanthin. Lipids (neutral reserve lipids and polar ones) also revealed species-specific variations, with increases in cellular content noted under extreme temperature conditions. Variations in toxicity were assessed through the Artemia franciscana bioassay. For both species, a decrease in toxicity was observed when temperature dropped under the optimal temperature for growth. No PLTX-like compounds were detected in O. cf. siamensis strains. Thus, the main part of the lethal effect observed on A. franciscana was dependent on currently unknown compounds. From a multiclonal approach, this work allowed for defining specificities in the thermal niche and acclimation strategies of O. cf. siamensis and O. cf. ovata towards temperature. Potential impacts of climate change on the toxic risk associated with Ostreopsis blooms in both NW Mediterranean Sea and NE Atlantic coast is further discussed, taking into account variations in the geographic distribution, growth abilities and toxicity of each species.

SUPERVISED IMAGE CLASSIFICATION MODEL FOR CORAL BLEACHING DETECTION USING A BI-TEMPORAL SENTINEL-2 IMAGE STACK

Abstract. Coral reefs are among the most vulnerable ecosystems to coastal and land-based anthropogenic factors. Aside from sudden increase in sea temperatures, external factors such as local and regional disturbances are found to influence coral reef environments which often lead to bleaching events. According to the Status of Coral Reefs of the World: 2020 report, from 2009 to 2018, there has been a progressive loss of live corals at the global level which may be attributed to the increasing anthropogenic activities (Souter et al., 2021). Due to coral’s sensitivity to environmental stressors, it is significantly considered as an indicator for global climate conditions. In this regard, this study developed a remote sensing change detection technique to segment coral bleaching from satellite images. Using a bi-temporal image stack composed of Sentinel-2 images showing pre and post bleaching, a machine learning classification model was developed to capture typologies of changes visible between the two images which included bleaching. Random Forest (RF) algorithm was employed to classify changes. This model obtained overall accuracies and kappa statistics of 0.97 and 0.94 respectively with minimum consumer and producer accuracy of 0.91. Moreover, the identified changes showed 78% agreement with the in-situ data composed of 31 monitoring stations distributed around Sekisei Lagoon, Okinawa, Japan. This study demonstrated a promising potential of machine learning for change detection for coral bleaching monitoring.

Warming changes the life history composition of marine fish communities at high latitudes

Across marine ecosystems, species are redistributing as a response to increased sea temperatures. In the Arctic, rapid warming causes poleward shifts of boreal species. Which species are redistributing and the drivers of their movements can be related to their life history traits. Here, we aimed to characterize and analyze the spatio-temporal changes in the life history strategy (LHS) composition of fish communities in the Barents Sea (2004-2017). We performed an archetype analysis to characterize species’ LHS based on their life history traits and related it to the equilibrium-periodic-opportunistic framework. Fish species in temperate ecosystems were documented to be largely distributed along the opportunistic-periodic continuum, whereas many fish species in the Barents Sea are distributed along the opportunistic-equilibrium continuum, illustrating the specificity of Arctic fish LHS. During the study period, boreal periodic species showed an increase in the central Barents Sea, a zoogeographic transition area. Simultaneously, Arctic opportunistic species retracted to cold waters, and the abundance of equilibrium strategists increased in the eastern Barents Sea. The expansion of periodic species may be explained by the configuration of their traits. This includes a high reproductive potential, broader diet, and migratory behavior. These traits might increase their tolerance and adaptive capacity to a changing environment. Fish LHS play a crucial role in fisheries management, particularly in promoting better fishing practices for vulnerable populations. By understanding the various LHS adopted by different fish species and their environmental preferences, fisheries managers can develop informed fishing strategies on a broader scale.

Global Warming Threats to Coral Bleaching Events and Their Impacts on Coastal Ecosystem Sustainability

The phenomenon of massive coral bleaching around the world is a black storm in coastal ecosystems this century. The annual increase in sea temperature by more than 1⁰C is a terrible fact that occurs due to global warming. There are many concerns raised especially on the cumulative impact of stress that corals experience when sea water temperature rise occurs. For this reason, this article is an intervention to reveal the high- level threat caused by global warming and the connection to coral bleaching events that disrupt coastal ecosystems. The literature study method in this article is useful to review and critically evaluate a number of articles that are closely related to support the fact of the urgency of coral bleaching in various countries. The great biological concern of coral bleaching that damages coastal ecosystems requires immediate mitigation and conservation, if it continues to degrade the number of coral populations significantly affects the decline in fish populations and biodiversity which affects the catch of fishermen and communities that have a major impact on coastal ecosystems. A good conservation strategy is expected to minimize the risk of damage so that it does not backfire on the chaos of coastal ecosystems in the future.

The optimal realized niches of the diatom Paralia sulcata in the Yellow Sea and its environmental implication

The observational and paleo-ecological records on some shelves (e.g., North Sea, Yellow Sea) have indicated that the proportion of Paralia sulcata in the diatom community has been increasing since the 1980s. Because of its heavily-silicified frustules, this species is considered as an important siliceous organism, which can impact the recycling efficiency of biogenic silicon in the ocean. However, the specific environmental factors driving the increase of P. sulcata remain unclear. In this study, based on seasonal in-situ observations and historical literature in the Yellow Sea, we statistically assessed the importance of different environmental factors in determining P. sulcata abundance. Further, we quantified its optimal realized niches, using the maximum entropy and generalized additive models to predict the fate of this species. P. sulcata indicates a preference for environments with cold temperatures and high nutrient levels. The contribution of sea temperature on cell abundance reaches up to 37.2 %, which is higher than that of the nutrient concentrations (∼ 20.5 %) and salinity (∼ 17.1 %). The optimal realized niches are defined as sea temperature at 6.25 ± 3.50 °C, salinity at 32.8 ± 0.52, the concentrations of dissolved inorganic nitrogen, phosphorus, and silicate at 8.38 ± 5.42 μM, 0.42 ± 0.29 μM, and 5.87 ± 3.53 μM, respectively, and ammonium/nitrate ratio at 1.32 ± 0.19. Based on the multivariate statistical methods, the optimal realized niches indicate that the increased sea temperatures in winter and spring, combined with nitrogen enrichment, especially ammonium enrichment, are key environmental drivers for P. sulcata proliferation in the Yellow Sea.

Scaling of fast-start performance and its thermal dependence in mummichog Fundulus heteroclitus.

Fast-start predator-escape performance and its sensitivity to temperature (24, 30, and 36°C) were evaluated in mummichog Fundulus heteroclitus across a range of body sizes spanning YOY to adult (35-68 mm standard length). Mummichogs exhibit isometry of body dimensions and areas of the dorsal and anal fins but negative allometry of the caudal fin area. These scaling relationships are consistent with observed decreases in fast-start angular velocities with increasing body size. Linear velocity, on the contrary, does not vary with size, and both large and small mummichogs are capable of traversing similar distances in a given amount of time. In addition, temperature influences fast-start performance in similar ways over the size range, though the magnitude of the effect varies with size for some performance measures. In general, fast-start performance increases with test temperature, but mummichogs acclimated to warmer temperatures exhibit lower performance at each test temperature. Altogether, our results suggest that mummichogs across the adult size range may suffer decreases in their predator-escape performance as increasing sea temperatures combine with short-term temperature fluctuations in the estuaries these fish occupy.

The reproductive phenology of Asparagopsis armata in New Zealand – Potential shifts 35 years later

The reproductive phenology (the timing of key reproductive events) of seaweeds is largely controlled by environmental factors related to seasonal change, particularly temperature. Therefore, it can be expected that climate change-induced increases in sea temperature can cause shifts in the reproductive phenology of seaweeds, although this has been difficult to detect due to the lack of baseline data for reproduction. We investigated the seasonal occurrence and reproductive phenology of the emerging aquaculture-target species Asparagopsis armata on the North Island of New Zealand from 2021 to 2022, which was previously assessed 35 years ago (1987) when temperatures were on average 1.5 °C cooler. Seasonality in reproduction was assessed via the presence of tetrasporangia, tetraspore release and germination rate, presence of cystocarps, cystocarp density and cystocarp opening. Tetrasporophytes occurred year-round with tetrasporangia present from March – September (austral autumn – spring), with populations most fertile from May – July (austral autumn – winter). Tetraspore release peaked in June 2021 and September 2022, but was otherwise low during our sampling. Gametophytes were present from August – November (austral winter –spring) with cystocarps present from September (austral spring), which was delayed in comparison to the 1987 assessment. Viable carpospores were also only released under controlled conditions during September, as opposed to during all reproductive months in the 1987 assessment. Discolouration was a common occurrence in natural populations during 2022 that translated into poor reproductive output and high mortality under controlled conditions, which could be explained by prolonged heat stress throughout 2022. This study presents the first temporally longitudinal analysis of potential climate driven shifts in reproductive phenology of a seaweed and provides a quantitative baseline for detecting changes in reproductive phenology in the future.

The pelagic food web of the Western Adriatic Sea: a focus on the role of small pelagics

The Adriatic Sea is one of the largest areas of occurrence of shared small pelagic stocks and the most fished area of the Mediterranean Sea, which is in turn one of the most exploited basins of the world. The variations in the stable isotope contents (δ15N and δ13C) were determined for three small pelagic fishes (i.e., Engraulis encrasicolus, Sardina pilchardus, and Sprattus sprattus, respectively known as anchovies, sardines and sprats) collected across the western side of the basin. Our data allowed to determine the width and features of their trophic niches, to assess potential overlap or resource partitioning among them, and likely anticipate species adaptation to future climate change scenarios. Moreover, variations in stable isotope contents were correlated to both resource availability (i.e., mesozooplankton) and environmental variables. The high productivity and in turn the high resource availability of the basin, especially in the northern part, resulted in favor of the resource partitioning that occurs in each sub-area of the Adriatic Sea among the three species. Medium-sized specimens of the three species mostly fed on small zooplankton, while adult sprats relied on large copepods and those of sardines and anchovies also consumed large portion of phytoplankton, confirming the high trophic plasticity of these two dominants small pelagic species. However, considering that anchovies have the greatest degree of trophic diversity compared with the other two species, they could be the most adapted to changing feeding conditions. The increase in sea temperatures that are reducing primary production and in turn zooplankton abundances, coupled with even more frequent extreme meteorologic events could exacerbate the competition for trophic resources among pelagic mesopredators, and could lead to more notable stocks’ fluctuations and unpredictable wasp-waist effects.