Marine Heat Waves Hazard 3D Maps and the Risk for Low Motility Organisms in a Warming Mediterranean Sea

Frequency and severity of heat waves is expected to increase as a consequence of climate change with important impacts on human and ecosystems health. However, while many studies explored the projected occurrence of hot extremes on terrestrial systems, few studies dealt with marine systems, so that both the expected change in marine heat waves occurrence and the effects on marine organisms and ecosystems remain less understood and surprisingly poorly quantified. Here we: (i) assess how much more frequent, severe, and depth-penetrating marine heat waves will be in the Mediterranean area in the next decades by post-processing the output of an ocean general circulation model; and (ii) show that heat waves increase will impact on many species that live in shallow waters and have reduced motility, and related economic activities. This information is made available also as a dataset of temperature threshold exceedance indexes that can be used in combination with biological information to produce risk assessment maps for target species or biomes across the whole Mediterranean Sea. As case studies we compared projected heat waves occurrence with thermotolerance thresholds of low motility organisms. Results suggest a deepening of the survival horizon for red coral (Corallium rubrum, a commercially exploited benthic species already subjected to heat-related mass mortality events) and coralligenous reefs as well as a reduction of suitable farming sites for the mussel Mythilus galloprovincialis. In recent years Mediterranean circalittoral ecosystems (coralligenous) have been severely and repeatedly impacted by marine heat waves. Our results support that equally deleterious events are expected in the near future also for other ecologically important habitats (e.g., seagrass meadows) and aquaculture activities (bivalvae), and point at the need for mitigation strategies

ATP Supply May Contribute to Light-Enhanced Calcification in Corals More Than Abiotic Mechanisms

Zooxanthellate corals are known to increase calcification rates when exposed to light, a phenomenon called light-enhanced calcification that is believed to be mediated by symbionts' photosynthetic activity. There is controversy over the mechanism behind this phenomenon, with hypotheses coarsely divided between abiotic and biologically-mediated mechanisms. At the same time, accumulating evidence shows that calcification in corals relies on active ion transport to deliver the skeleton building blocks into the calcifying medium, making it is an energetically costly activity. Here we build on generally accepted conceptual models of the coral calcification machinery and conceptual models of the energetics of coral-zooxanthellae symbiosis to develop a model that can be used to isolate the biologically-mediated and abiotic effects of photosynthesis, respiration, temperature, and seawater chemistry on coral calcification rates and related metabolic costs. We tested this model on data from the Mediterranean scleractinian Cladocora caespitosa, an acidification resistant species. We concluded that most of the variation in calcification rates due to photosynthesis, respiration and temperature can be attributed to biologically-mediated mechanisms, in particular to the ATP supplied to the active ion transports. Abiotic effects are also present but are of smaller magnitude. Instead, the decrease in calcification rates caused by acidification, albeit small, is sustained by both abiotic and biologically-mediated mechanisms. However, there is a substantial extra cost of calcification under acidified conditions. Based on these findings and on a literature review we suggest that the energy aspect of coral calcification might have been so far underappreciated

Recent Trends Towards Oligotrophication of the Northern Adriatic: Evidence from Chlorophyll a Time Series

Abstract The results of the updated and quality-checked data base of field observations on chlorophyll a (Chl a) collected in the period 1970-2007 in the Northern Adriatic Sea are presented. From the last decade, SeaWiFS satellite information was also considered. Results demonstrate a global tendency towards Chl a reduction in the period of investigation, which is more marked in the eutrophic area under the influence of the Po River. In the rest of the basin, which presents meso- or oligotrophic characteristics, long-term changes are more difficult to detect. The long-term field dataset can be divided into two periods: the last decade characterized by the strong decrease observed in the whole northern Adriatic and the earlier period with no or slight increase. The recent substantial reduction of Chl a concentrations is confirmed all over the basin (−0.11 mg m−3 year−1) from satellite-derived information. Results are consistent with recently evidenced decrease in concentrations of phosphate and ammonia and point to the existence of oligotrophication in the Northern Adriatic. Results indicate forcefully that the still common perception of the Adriatic Sea as a very eutrophic basin is no longer appropriate, at least for its northern part and in recent years

direct and indirect impacts of marine acidification on the ecosystem services provided by coralligenous reefs and seagrass systems

Increasing emissions of CO2 and the resultant ocean acidification (OA) will have large implications for the marine ecosystems sustained by habitat-forming species and their related ecosystem services (ES), with potentially significant impacts on human well-being. Here, we provide an assessment of the direct and indirect impacts of OA on ES. The changes in the functioning of coralligenous reefs and Posidonia oceanica meadows promoted by OA were investigated by i) synthesizing current knowledge into conceptual models. The models were then used to, ii) assessing the impacts of exposure of the selected taxa at the acidification level associated with two CO2 emission scenarios and iii) using the conceptual model outputs to project the cascading impacts from individuals to functions to ES.The results highlight that the combination of the direct and indirect effects of acidification will alter many functions of both coralligenous and P.oceanica systems, triggering habitat modifications and the loss of highly valuable ES.While the exact timing of the expected changes will depend on the severity of the emission scenarios, significant and hardly reversible changes can be expected as quickly as a few decades under the business-as-usual scenario, and many ecosystem services are at risk even under much more conservative scenarios. Keywords: Ocean acidification, Posidonia oceanica, Coralligenous, Ecosystem services, Mediterranean sea, Conceptual model

Plankton Communities Behave Chaotically Under Seasonal or Stochastic Temperature Forcings

Chaos is observed in natural systems, especially in ecosystems with populations characterized by a short reproductive time scale, such as plankton. We examined if external forcings can be the origin of chaos in a state-of-the-art marine biogeochemical model. Both a seasonal temperature cycle and noise added to this cycle were studied as external forcings, and their interaction with the dynamics resulting from biological interactions, such as competition. Our findings indicate that deterministic periodic forcing can induce chaos in the ecosystem only when biological interactions have already established periodic oscillations within the system. We conclude that random temperature fluctuations can be a driver of chaos in plankton populations, due also to the stochastic nature of the marine environment. The stochastic mechanism for the occurrence of chaos could find wide application in natural systems as it requires no preconditions

A model for the trophic food web of the Gulf of Trieste

The Gulf of Trieste is located in the northernmost part of the Adriatic Sea. It exhibits high variable hydrodynamical and trophic conditions, due to the interactions among the wind regime, characterised by impulsive strong wind events (Bora), the fresh water –nutrient rich- run off, especially from Isonzo river, the interaction with the general circulation of North Adriatic Sea, the seasonal heating and cooling of water and alternation of mixing and stratification of water column. Gulf is also characterised by occurrence of anomaly events as mucilagine. Despite the high inter-annual biological variability, it is possible to recognise the seasonal succession of two trophic structures: the classical food chain which starts with the spring diatom bloom and the microbial food web during summer stratification. As a first step in the formulation of a comprehensive model for the Gulf of Trieste, able to reproduce the fundamental functioning of the ecosystem and to investigate the occurrence of anomalies, we have developed a food web model describing the fluxes of carbon and of phosphorous, the later being thought as the limiting nutrient in the Gulf. The model considers two groups of phytoplankton: diatom and nano-pico phytoplankton; two groups of zooplankton: the first represented by mixed filter feeders, and the second consisted by microzooplankton and by fine filter feeder, mainly represented by summer cladocera Penilia avirostris. Heterotrophic bacteria are explicitly included in the model, in order to describe their role in P cycle either as remineralization agents or as nanophytoplankton competitors, and their role in DOC degradation. The content of P and C in POM and DOM compartments are also included to better reproduce the uncoupling of the P and C cycles in seawater system. The model, forced by nutrient availability and climatological factors, reproduces the seasonal succession between classical food chain and microbial food web. Sensitivity analysis (Morris’s method) applied to the model permits to highlight the most important factor in controlling the evolution of the system

Sensitivity Analysis of VELFEEM –Venice Lagoon Finite Element Ecological Model- to the Macro-Nutrient Input Regime

A sensitivity analysis of VELFEEM, the Finite Element Ecological Model for the lagoon of Venice, has been performed in order to test the responses of the model to changes in external input regimes. The model is obtained by internally coupling a hydrodynamic model, an energetic model, and an ecological model. The hydrodynamics are simulated using SHYFEM, a barotropic bi-dimensional model based on a finite element discretization of the spatial domain, which allows for a very good spatial resolution of the lagoon morphology while keeping at a low level the computational demand. Using a standard heat fluxes formulation, the energetic module computes the water temperature of each element starting from meteorological daily measurement. The ecological processes are simulated by the evolution of nine state variables, namely by phytoplankton, zooplankton, nutrients (ammonia, nitrate and phosphate) organic detritus (organic nitrogen organic phosphorous and CBOD) and dissolved oxygen. In a previous work, the role played by physical forcings in the definition of the water quality level has already been investigated, and the conclusion was that a proper parameterisation of these processes would increase the accuracy of our model prediction. Here we aim to see whether the same consideration could be extended at the macronutrient input regime. Assuming that the total amount of macronutrients and of freshwater entering the basin is the same in our scenarios, we vary the river input regime comparing an idealised scenario with a realistic scenario. The sensitivity to the variation in input regime and variations in the macro nutrient exchange with the sea has been investigated, by comparing model predictions of spatial and temporal evolution of major state variables and of an aggregate index of water quality (TRIX). In the idealised scenario the water discharge is represented by an idealised function and the concentration in macronutrient is constant during the whole year, and it is the same for each river, during the one-year simulation. In the real scenario we use monthly data field of river flow and the concentration values sampled at each river

Assessing, quantifying and valuing the ecosystem services of coastal lagoons

The natural conservation of coastal lagoons is important not only for their ecological importance, but also because of the valuable ecosystem services they provide for human welfare and wellbeing. Coastal lagoons are shallow semi-enclosed systems that support important habitats such as wetlands, mangroves, salt-marshes and seagrass meadows, as well as a rich biodiversity. Coastal lagoons are also complex social-ecological systems with ecosystem services that provide livelihoods, wellbeing and welfare to humans. This study assessed, quantified and valued the ecosystem services of 32 coastal lagoons. The main findings of the study are: (i) the definitions of ecosystem services are still not generally accepted; (ii) the quantification of ecosystem services is made in many different ways, using different units; (iii) the evaluation in monetary terms of some ecosystem service is problematic, often relying on non-monetary evaluation methods; (iv) when ecosystem services are valued in monetary terms, this may represent very different human benefits; and, (v) different aspects of climate change, including increasing temperature, sea-level rise and changes in rainfall patterns threaten the valuable ecosystem services of coastal lagoons.DEVOTES project, from the European Union's Seventh Framework Programme for research, technological development and demonstration [308392]; networks and communities of Eurolag; Future Earth Coasts; SCOR; Fundacao para a Ciencia e a Tecnologia (FCT) Investigador Programme [IF/00331/2013]; Fundacao para a Ciencia e a Tecnologia [UID/MAR/04292/2013]; CESAM by FCT/MEC national funds (PIDDAC) [UID/AMB/50017/2013 - POCI-01-0145-FEDER-007638]; FEDER; European Commission, under the 7th Framework Programme through the collaborative research project LAGOONS [283157]; FCT [SFRH/BPD/107823/2015, SFRH/BPD/91494/2012