Estat de conservació de les praderies de Posidonia oceanica (Linnaeus) Delile, 1813 dins la Badia de Portocolom (Mallorca)

[cat] Posidonia oceanica (Linnaeus), Delile, 1813 és una fanerògama marina endèmica del Mediterrani que proporciona gran quantitat de serveis ecosistèmics i és clau per a la conservació de la biodiversitat. Com la majoria de la vegetació marina està en greu recessió. Una de les principals amenaces que afecten aquesta planta, juntament amb l’eutrofització i l’escalfament global, és el fondeig incontrolat. En aquest estudi fem una avaluació de l’estat de conservació de la praderia de P. oceanica situada davant la platja de s’Arenal a la badia de Portocolom afectada per fondeig incontrolat. La mitjana del percentatge de cobertura entre una fondària de 2 i 4.8 metres va ser de 44.2 ± 13.6 %, cobertures inferiors a les reportades anteriorment per aquesta zona. Les densitats van variar entre 392 i 576 feixos/m2, amb una mitjana de 508 ± 31 feixos/m2. Aquesta praderia té molt baixa densitat, o densitat anormal, indicant que està sotmesa a pressions que posen en perill el seu estat de conservació. Vam poder estimar el nombre de feixos arrabassats per una àncora d’un vaixell d’uns 15 metres d’eslora, que va ser de 165 ± 31 feixos. Aquesta praderia necessitaria 5 anys en condicions òptimes per poder recolonitzar l’àrea arrabassada per aquesta àncora. Una estima del carboni alliberat per l’efecte del fondeig d’aquesta àncora revelaria que 915 g de carboni quedaria disponible i podria ser alliberat a l’atmosfera.[eng] Posidonia oceanica (Linnaeus), Delile, 1813 is an endemic Mediterranean seagrass that provides multiple ecosystem services and is a key species for biodiversity conservation. Like most submerged vegetation, this key habitat is regressing alarmingly. One of the main threats affecting this seagrass, together with eutrophication and global warming, is uncontrolled anchoring. Here, we evaluate the conservation status of the P. oceanica meadow in front of s’Arenal beach in Portocolom Bay that is affected by uncontrolled anchoring. The mean cover percentage at depths between 2 and 4.8 meters was 44.2 ± 13.6 %, lower than previously reported for this area. Densities varied between 392 and 576 shoots/m2, with an average of 508 ± 31 shoots/m2. This is a very low, or even an abnormal, density, indicating that this meadow is subject to pressures that are threatening its conservation. We could estimate the number of shoots that were torn off by the action of anchoring of a 15 m long boat: 165 ± 31 shoots. This meadow would require 5 years of optimal conditions to be able to recolonize the area removed by the action of this anchoring. An estimate of the carbon released by the action of this anchoring was 915 g of carbon that could become available and could be released to the atmosphere

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Warming effect on nitrogen fixation in Mediterranean macrophyte sediments

The Mediterranean Sea is warming faster than the global ocean, with important consequences for organisms and biogeochemical cycles. Warming is a major stressor for key marine benthic macrophytes. However, the effect of warming on marine N2 fixation remains unknown, despite the fact that the high productivity of macrophytes in oligotrophic waters is partially sustained by the input of new nitrogen (N) into the system by N2 fixation. Here, we assess the impact of warming on the N2 fixation rates of three key marine macrophytes: Posidonia oceanica, Cymodocea nodosa, and Caulerpa prolifera. We experimentally measured N2 fixation rates in vegetated and bare sediments at temperatures encompassing current summer mean (25 and 27&thinsp;∘C), projected summer mean (29 and 31&thinsp;∘C), and projected summer maximum (33&thinsp;∘C) seawater surface temperatures (SSTs) by the end of the century under a scenario of moderate greenhouse gas emissions. We found that N2 fixation rates in vegetated sediments were 2.8-fold higher than in bare sediments at current summer mean SST, with no differences among macrophytes. Currently, the contribution of N2 fixation to macrophyte productivity could account for up to 7&thinsp;%, 13.8&thinsp;%, and 1.8&thinsp;% of N requirements for P. oceanica, C. nodosa, and C. prolifera, respectively. We show the temperature dependence of sediment N2 fixation rates. However, the thermal response differed for vegetated sediments, in which rates showed an optimum at 31&thinsp;∘C followed by a sharp decrease at 33&thinsp;∘C, and bare sediments, in which rates increased along the range of the experimental temperatures. The activation energy and Q10 were lower in vegetated than bare sediments, indicating the lower thermal sensitivity of vegetated sediments. The projected warming is expected to increase the contribution of N2 fixation to Mediterranean macrophyte productivity. Therefore, the thermal dependence of N2 fixation might have important consequences for primary production in coastal ecosystems in the context of warming.</p

Effects of wastewater treatment plant effluent inputs on planktonic metabolic rates and microbial community composition in the Baltic Sea

The Baltic Sea is the world's largest area suffering from eutrophication-driven hypoxia. Low oxygen levels are threatening its biodiversity and ecosystem functioning. The main causes for eutrophication-driven hypoxia are high nutrient loadings and global warming. Wastewater treatment plants (WWTP) contribute to eutrophication as they are important sources of nitrogen to coastal areas. Here, we evaluated the effects of wastewater treatment plant effluent inputs on Baltic Sea planktonic communities in four experiments. We tested for effects of effluent inputs on chlorophyll <i>a</i> content, bacterial community composition, and metabolic rates: gross primary production (GPP), net community production (NCP), community respiration (CR) and bacterial production (BP). Nitrogen-rich dissolved organic matter (DOM) inputs from effluents increased bacterial production and decreased primary production and community respiration. Nutrient amendments and seasonally variable environmental conditions lead to lower alpha-diversity and shifts in bacterial community composition (e.g. increased abundance of a few cyanobacterial populations in the summer experiment), concomitant with changes in metabolic rates. An increase in BP and decrease in CR could be caused by high lability of the DOM that can support secondary bacterial production, without an increase in respiration. Increases in bacterial production and simultaneous decreases of primary production lead to more carbon being consumed in the microbial loop, and may shift the ecosystem towards heterotrophy

Deoxygenation in the oxygen minimum zone of the eastern tropical North Atlantic

Observations and model results both indicate increasing oxygen minimum zones (OMZ) in the tropical oceans. Here we report on record low dissolved oxygen minimum concentrations in the eastern tropical North Atlantic in fall of 2008, with less than 40 mu mol kg(-1) in the core of the OMZ. There we find a deoxygenation rate of similar to 0.5 mu mol kg(-1) a(-1) during the last decades on two repeat sections at 7.5 and 11 degrees N. The potential temperature and salinity in the surface and central water layers increased on both sections compared to previous observations. However, in contrast to the oxygen decrease in the core of the OMZ, increasing oxygen concentrations were observed in the central water layer above the OMZ. The observed deoxygenation was thus restricted to the core of the oxygen minimum layer. It remains unclear whether the vertical expansion of the oxygen minimum represents a long time trend or decadal variation

The effects of changing climate on faunal depth distributions determine winners and losers

Changing climate is predicted to impact all depths of the global oceans, yet projections of range shifts in marine faunal distributions in response to changing climate seldom evaluate potential shifts in depth distribution. Marine ectotherms’ thermal tolerance is limited by their ability to maintain aerobic metabolism (oxygen- and capacity-limited tolerance), and is functionally associated with their hypoxia tolerance. Shallow-water (&lt;200 m depth) marine invertebrates and fishes demonstrate limited tolerance of increasing hydrostatic pressure (pressure exerted by the overlying mass of water), and hyperbaric (increased pressure) tolerance is proposed to depend on the ability to maintain aerobic metabolism, too. Here, we report significant correlation between the hypoxia thresholds and the hyperbaric thresholds of taxonomic groups of shallow-water fauna, suggesting that pressure tolerance is indeed oxygen-limited. Consequently, it appears that the combined effects of temperature, pressure, and oxygen concentration constrain the fundamental ecological niches (FENs) of marine invertebrates and fishes. Including depth in a conceptual model of oxygen- and capacity-limited FENs’ responses to ocean warming and deoxygenation confirms previous predictions made based solely on consideration of the latitudinal effects of ocean warming (e.g. Cheung et al., 2009), that polar taxa are most vulnerable to the effects of climate change, with Arctic fauna experiencing the greatest FEN contraction. In contrast, the inclusion of depth in the conceptual model reveals for the first time that temperate fauna as well as tropical fauna may experience substantial FEN expansion with ocean warming and deoxygenation, rather than FEN maintenance or contraction suggested by solely considering latitudinal range shifts

Temporal and spatial dynamics of large lake hypoxia: Integrating statistical and three‐dimensional dynamic models to enhance lake management criteria

Hypoxia or low bottom water dissolved oxygen (DO) is a world‐wide problem of management concern requiring an understanding and ability to monitor and predict its spatial and temporal dynamics. However, this is often made difficult in large lakes and coastal oceans because of limited spatial and temporal coverage of field observations. We used a calibrated and validated three‐dimensional ecological model of Lake Erie to extend a statistical relationship between hypoxic extent and bottom water DO concentrations to explore implications of the broader temporal and spatial development and dissipation of hypoxia. We provide the first numerical demonstration that hypoxia initiates in the nearshore, not the deep portion of the basin, and that the threshold used to define hypoxia matters in both spatial and temporal dynamics and in its sensitivity to climate. We show that existing monitoring programs likely underestimate both maximum hypoxic extent and the importance of low oxygen in the nearshore, discuss implications for ecosystem and drinking water protection, and recommend how these results could be used to efficiently and economically extend monitoring programs.Key Points:We modeled seasonal and spatial dynamics of Lake Erie hypoxiaWe showed hypoxia starts nearshore and can persist after traditional monitoring programs endWe recommend monitoring adjustments and explore impacts of different hypoxia definitionsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133547/1/wrcr22074.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133547/2/wrcr22074-sup-0001-2015WR018170-s01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133547/3/wrcr22074_am.pd

Testing local and global stressor impacts on a coastal foundation species using an ecologically realistic framework

Despite the abundance of literature on organismal responses to multiple environmental stressors, most studies have not matched the timing of experimental manipulations with the temporal pattern of stressors in nature. We test the interactive effects of diel-cycling hypoxia with both warming and decreased salinities using ecologically realistic exposures. Surprisingly, we found no evidence of negative synergistic effects on Olympia oyster growth; rather, we found only additive and opposing effects of hypoxia (detrimental) and warming (beneficial). We suspect that diel-cycling provided a temporal refuge that allowed physiological compensation. We also tested for latent effects of warming and hypoxia to low-salinity tolerance using a seasonal delay between stressor events. However, we did not find a latent effect, rather a threshold survival response to low salinity that was independent of early life-history exposure to warming or hypoxia. The absence of synergism is likely the result of stressor treatments that mirror the natural timing of environmental stressors. We provide environmental context for laboratory experimental data by examining field time series environmental data from four North American west coast estuaries and find heterogeneous environmental signals that characterize each estuary, suggesting that the potential stressor exposure to oysters will drastically differ over moderate spatial scales. This heterogeneity implies that efforts to conserve and restore oysters will require an adaptive approach that incorporates knowledge of local conditions. We conclude that studies of multiple environmental stressors can be greatly improved by integrating ecologically realistic exposure and timing of stressors found in nature with organismal life-history traits

Hypoxic induced decrease in oxygen consumption in Cuttlefish (Sepia officinalis) is associated with minor increases in mantle octopine but no changes in markers of protein turnover

The common cuttlefish (Sepia officinalis), a dominant species in the north-east Atlantic ocean and Mediterranean Sea, is potentially subject to hypoxic conditions due to eutrophication of coastal waters and intensive aquaculture. Here we initiate studies on the biochemical response to an anticipated level of hypoxia. Cuttlefish challenged for 1 h at an oxygen level of 50% dissolved oxygen saturation showed a decrease in oxygen consumption of 37% associated with an 85% increase in ventilation rate. Octopine levels were increased to a small but significant level in mantle, whereas there was no change in gill or heart. There were no changes in mantle free glucose or glycogen levels. Similarly, the hypoxic period did not result in changes in HSP70 or polyubiquinated protein levels in mantle, gill, or heart. As such, it appears that although there was a decrease in metabolic rate there was only a minor increase in anaerobic metabolism as evidenced by octopine accumulation and no biochemical changes that are hallmarks of alterations in protein trafficking. Experiments with isolated preparations of mantle, gill, and heart revealed that pharmacological inhibition of protein synthesis could decrease oxygen consumption by 32 to 42% or Na+/K+ ATPase activity by 24 to 54% dependent upon tissue type. We propose that the decrease in whole animal oxygen consumption was potentially the result of controlled decreases in the energy demanding processes of both protein synthesis and Na+/K+ ATPase activity.info:eu-repo/semantics/publishedVersio