Mediterranean Sea climate and environmental change

Invading the Mediterranean Sea: biodiversity patterns shaped by human activities

administrator — Mon, 22 Sep 2014 10:08:33 +0000

Human activities, such as shipping, aquaculture, and the opening of the Suez Canal, have led to the introduction of nearly 1,000 alien species into the Mediterranean Sea. We investigated how human activities, by providing pathways for the introduction of alien species, may shape the biodiversity patterns in the Mediterranean Sea. Richness of Red Sea species introduced through the Suez Canal (Lessepsian species) is very high along the eastern Mediterranean coastline, reaching a maximum of 129 species per 100 km2, and declines towards the north and west. The distribution of species introduced by shipping is strikingly different, with several hotspot areas occurring throughout the Mediterranean basin. Two main hotspots for aquaculture-introduced species are observed (the Thau and Venice lagoons). Certain taxonomic groups were mostly introduced through specific pathways – fish through the Suez Canal, macrophytes by aquaculture, and invertebrates through the Suez Canal and by shipping. Hence, the local taxonomic identity of the alien species was greatly dependent on the dominant maritime activities/interventions and the related pathways of introduction. The composition of alien species differs among Mediterranean ecoregions; such differences are greater for Lessepsian and aquaculture-introduced species. The spatial pattern of native species biodiversity differs from that of alien species: the overall richness of native species declines from the north-western to the south-eastern regions, while the opposite trend is observed for alien species. The biodiversity of the Mediterranean Sea is changing, and further research is needed to better understand how the new biodiversity patterns shaped by human activities will affect the Mediterranean food webs, ecosystem functioning, and the provision of ecosystem services.

Katsanevakis S, Coll M, Piroddi C, Steenbeek J, Ben Rais Lasram F, Zenetos A, Cardoso A, 2014: Invading the Mediterranean Sea: biodiversity patterns shaped by human activities, Front. Mar. Sci. 1:32. doi:10.3389/fmars.2014.00032. Article (subscription required).

Vulnerability of Mediterranean Ecosystems to Long-Term Changes along the Coast of Israel

administrator — Mon, 22 Sep 2014 10:06:08 +0000

Although human activity is considered to be a major driving force affecting the distribution and dynamics of Mediterranean ecosystems, the full consequences of projected climate variability and relative sea-level changes on fragile coastal ecosystems for the next century are still unknown. It is unclear how these waterfront ecosystems can be sustained, as well as the services they provide, when relative sea-level rise and global warming are expected to exert even greater pressures in the near future (drought, habitat degradation and accelerated shoreline retreat). Haifa Bay, northern Israel, has recorded a landward sea invasion, with a maximum sea penetration 4,000 years ago, during an important period of urban development and climate instability. Here, we examine the cumulative pressure of climate shifts and relative sea-level changes in order to investigate the patterns and mechanisms behind forest replacement by an open-steppe. We provide a first comprehensive and integrative study for the southern Levant that shows that (i) human impact, through urbanization, has been the main driver behind ecological erosion in the past 4,000 years; (ii) climate pressures have reinforced this impact; and (iii) local coastal changes have played a decisive role in eroding ecosystem resilience. These three parameters, which have closely interacted during the last 4,000 years in Haifa Bay, clearly indicate that for an efficient management of the coastal habitats, anthropogenic pressures linked to urban development must be reduced in order to mitigate the predicted effects of Global Change.

Kaniewski D, Van Campo E, Morhange C, Guiot J, Zviely D, et al., 2014: Vulnerability of Mediterranean Ecosystems to Long-Term Changes along the Coast of Israel, PLoS ONE, 9(7): e102090, doi:10.1371/journal.pone.0102090. Article.

Ecological Shifts in Mediterranean Coralligenous Assemblages Related to Gorgonian Forest Loss

administrator — Mon, 22 Sep 2014 10:04:51 +0000

Mediterranean gorgonian forests are threatened by several human activities and are affected by climatic anomalies that have led to mass mortality events in recent decades. The ecological role of these habitats and the possible consequence of their loss are poorly understood. Effects of gorgonians on the recruitment of epibenthic organisms were investigated by manipulating presence of gorgonians on experimental panels at 24 m depth, for Eunicella cavolinii, and at 40 m depth, for Paramuricea clavata, at two sites: Tavolara Island (Tyrrhenian Sea) and Portofino Promontory (Ligurian Sea). After 4 months, the most abundant taxa on the panels were encrusting green algae, erect red algae and crustose coralline algae at 24 m depth and encrusting brown algae and erect red algae at 40 m depth. Assemblages on the panels were significantly affected by the presence of the gorgonians, although effects varied across sites and between gorgonian species. Species diversity and evenness were lower on panels with gorgonian branches. Growth of erect algae and recruitment of serpulid polychaetes were also affected by the presence of the gorgonians, primarily at Tavolara. Crustose coralline algae and erect sponges were more abundant on E. cavolinii panels at 24 m depth, while encrusting bryozoans were more abundant on P. clavata panels at 40 m depth. Effects of gorgonians on recruited assemblages could be due to microscale modification of hydrodynamics and sediment deposition rate, or by a shading effect reducing light intensity. Gorgonians may also intercept settling propagules, compete for food with the filter-feeders and/or for space by producing allelochemicals. Presence of gorgonians mainly limits the growth of erect algae and enhances the abundance of encrusting algae and sessile invertebrates. Therefore, the gorgonian disappearances may cause a shift from assemblages characterised by crustose coralline algae to filamentous algae assemblages, decreasing complexity and resilience of coralligenous bioconstructions.

Ponti M, Perlini RA, Ventra V, Grech D, Abbiati M, et al., 2014: Ecological Shifts in Mediterranean Coralligenous Assemblages Related to Gorgonian Forest Loss, PLoS ONE, 9(7): e102782, doi:10.1371/journal.pone.0102782. Article.

Trace element profiles of the sea anemone Anemonia viridis living nearby a natural CO2 vent

administrator — Mon, 22 Sep 2014 10:03:03 +0000

Ocean acidification (OA) is not an isolated threat, but acts in concert with other impacts on ecosystems and species. Coastal marine invertebrates will have to face the synergistic interactions of OA with other global and local stressors. One local factor, common in coastal environments, is trace element contamination. CO₂ vent sites are extensively studied in the context of OA and are often considered analogous to the oceans in the next few decades. The CO₂ vent found at Levante Bay (Vulcano, NE Sicily, Italy) also releases high concentrations of trace elements to its surrounding seawater, and is therefore a unique site to examine the effects of long-term exposure of nearby organisms to high pCO₂ and trace element enrichment in situ. The sea anemoneAnemonia viridis is prevalent next to the Vulcano vent and does not show signs of trace element poisoning/stress. The aim of our study was to compare A. viridis trace element profiles and compartmentalization between high pCO₂ and control environments. Rather than examining whole anemone tissue, we analyzed two different body compartments—the pedal disc and the tentacles, and also examined the distribution of trace elements in the tentacles between the animal and the symbiotic algae. We found dramatic changes in trace element tissue concentrations between the high pCO₂/high trace element and control sites, with strong accumulation of iron, lead, copper and cobalt, but decreased concentrations of cadmium, zinc and arsenic proximate to the vent. The pedal disc contained substantially more trace elements than the anemone’s tentacles, suggesting the pedal disc may serve as a detoxification/storage site for excess trace elements. Within the tentacles, the various trace elements displayed different partitioning patterns between animal tissue and algal symbionts. At both sites iron was found primarily in the algae, whereas cadmium, zinc and arsenic were primarily found in the animal tissue. Our data suggests that A. viridis regulates its internal trace element concentrations by compartmentalization and excretion and that these features contribute to its resilience and potential success at the trace element-rich high pCO₂ vent.

Horwitz R, Borell EM, Fine M, Shaked Y, 2014: Trace element profiles of the sea anemone Anemonia viridis living nearby a natural CO₂ vent, PeerJ, 2:e538, doi:10.7717/peerj.538. Article.

Effects of different pCO2 concentrations on marine bacterial community structure, Eastern Harbor, Alexandria, Egypt

administrator — Mon, 22 Sep 2014 10:01:21 +0000

The direct effect of an elevated CO₂ concentration range (280, 385, 550, 750 and 1050 µatm) on the marine bacterial counts and dominancy of species were examined. Our results demonstrated that the variation in glucose consumption corresponding to the incubation period (h) of bacterial community structure showed that glucose degradation as a carbon source for bacteria is in good consistency with the total bacterial count pattern. Glucose uptake and oxygen consumption are increased by increasing the temperature from 28 to 35°C and also by increasing pCO₂ from nowadays pCO₂ (385µatm) to (1050 µatm). The highest consumption of glucose and oxygen was recorded in consistence with the dominancy of glucose degrading bacteria. The dominant bacterial species isolated from the Eastern Harbor, Alexandria, Egypt were counted and genetically identified. The total bacterial count (CFU/ml) increased linearly with increasing different pCO₂ at 35°C from 280 and 1050, respectively. Total bacterial count (CFU/ml) at different pCO₂ increased linearly with the incubation temperature (28-35°C). There were seven bacterial isolates from the Eastern Harbor with codes (HW1-HW7). They were affiliated according to their 16S rDNA to Bacillus cereus HW1, Psychrobacter maritimus HW2, Shima marina HW3, Pseudoalteromonas atlanticaHW4, Bacillus horikoshii HW5, Oceanicola marinus HW6 and Oceanicola nanhaiensis HW7, respectively. Oceanicola nanhaiensis HW7 exhibited fluctuation in hydrolytic activities against several carbon sources. The highest activity was for lipase followed by agarase, while the lowest activity was for cellulase. This It is also concluded that ocean acidification will impact bacterial organic matter degradation by changing reaction velocities of extracellular enzymes.

Ibrahim HAH, El-Sayed WMM, Shaltout NA, El-Shorbagi EK, 2014: Effects of different pCO₂concentrations on marine bacterial community structure, Eastern Harbor, Alexandria, Egypt, Life Sci J 2014;11(10):781-789. Article.

Space-time variability of alkalinity in the Mediterranean Sea

administrator — Mon, 22 Sep 2014 09:59:05 +0000

The results indicate that the Mediterranean Sea shows alkalinity values that are much higher than those observed in the Atlantic Ocean on a basin-wide scale. A marked west-to-east surface gradient of alkalinity is reproduced as a response to the terrestrial discharges, the mixing effect with the Atlantic water entering from the Gibraltar Strait and the Black Sea water from Dardanelles, and the surface flux of evaporation minus precipitation. Dense water production in marginal seas (Adriatic and Aegean Seas), where alkaline inputs are relevant, and the Mediterranean thermohaline circulation sustains the west-to-east gradient along the entire water column. In the surface layers, alkalinity has a relevant seasonal cycle (up to 40 μmol kg⁻¹) that is driven both by physical and biological processes. A comparison of alkalinity vs. salinity indicates that different regions present different relationships. In regions of freshwater influence, the two measures are negatively correlated due to riverine alkalinity input, whereas they are positively correlated in open seas. Alkalinity always is much higher than in the Atlantic waters, which might indicate a higher than usual buffering capacity towards ocean acidification, even at high concentrations of dissolved inorganic carbon.

Cossarini G, Lazzari P, Solidoro C, 2014: Space-time variability of alkalinity in the Mediterranean Sea, Biogeosciences Discuss., 11, 12871-12893, doi:10.5194/bgd-11-12871-2014. Article.

Lagocephalus sceleratus (Gmelin, 1789) expands through the African coasts towards the Western Mediterranean Sea: A call for awareness

administrator — Wed, 30 Jul 2014 13:58:01 +0000

The silver-cheeked toadfish Lagocephalus sceleratus is one of the most recent invaders in the Mediterranean Sea and a serious risk for public health. In June 2011, an awareness campaign to disseminate information related with this toxic species was launched by the Tunisian Ministry of Agriculture. Whilst providing a step toward the development of an appropriate early warning system, this case highlights a remarkable geographical extension of L. sceleratus along the entire Tunisian shoreline (from the island of Djerba to the region of Tabarka). We illustrate how the first step in the process of effectively managing the risks posed by an invasive species is to engage and communicate with the public.

Ben Souissi J, Rifi M, Ghanem R, Ghozzi L, Boughedir W, Azzurro E, 2014: Lagocephalus sceleratus (Gmelin, 1789) expands through the African coasts towards the Western Mediterranean Sea: A call for awareness, Management of Biological Invasions, 5(4). Article.

Heavy Metals Affect Nematocysts Discharge Response and Biological Activity of Crude Venom in the Jellyfish Pelagia noctiluca (Cnidaria, Scyphozoa)

administrator — Wed, 30 Jul 2014 13:55:11 +0000

Pollution of marine ecosystems and, specifically, heavy metals contamination may compromise the physiology of marine animals with events occurring on a cellular and molecular level. The present study focuses on the effect of short-term exposure to heavy metals like Zinc, Cadmium, Cobalt and Lanthanum (2-10 mM) on the homeostasis of Pelagia noctiluca (Cnidaria, Scyphozoa), a jellyfish abundant in the Mediterranean sea. This species possesses stinging organoids, termed nematocysts, whose discharge and concomitant delivery of venom underlie the survival of all Cnidaria. Nematocysts discharge response, elicited by combined chemico-physical stimulation, was verified on excised oral arms exposed to heavy metals for 20 min. In addition, the hemolytic activity of toxins, contained in the crude venom extracted from nematocysts isolated from oral arms, was tested on human erythrocytes, in the presence of heavy metals or their mixture. Treatment with heavy metals significantly inhibited both nematocysts discharge response and hemolytic activity of crude venom, in a dose-dependent manner, not involving oxidative events, that was irreversible in the case of Lanthanum. Our findings show that the homeostasis of Pelagia noctiluca, in terms of nematocysts discharge capability and effectiveness of venom toxins, is dramatically and rapidly compromised by heavy metals and confirm that this jellyfish is eligible as a model for ecotoxicological investigations.

Morabito R, Dossena S, La Spada G, Marino A, 2014: Heavy Metals Affect Nematocysts Discharge Response and Biological Activity of Crude Venom in the Jellyfish Pelagia noctiluca (Cnidaria, Scyphozoa), Cellular Physiology and Biochemistry, 34(2), 244-254, doi:10.1159/000362979. Article (subacription required).

Flux measurements in the surface marine Atmospheric Boundary Layer over the Aegean Sea, Greece

administrator — Wed, 30 Jul 2014 13:52:26 +0000

Micro-meteorological measurements within the surface Marine Atmospheric Boundary Layer took place at the shoreline of two islands at northern and south-eastern Aegean Sea of Greece. The primary goal of these experimental campaigns was to study the momentum, heat and humidity fluxes over this part of the north-eastern Mediterranean Sea, characterized by limited spatial and temporal scales which could affect these exchanges at the air–sea interface. The great majority of the obtained records from both sites gave higher values up to factor of two, compared with the estimations from the most widely used parametric formulas that came mostly from measurements over open seas and oceans. Friction velocity values from both campaigns varied within the same range and presented strong correlation with the wind speed at 10 m height while the calculated drag coefficient values at the same height for both sites were found to be constant in relation with the wind speed. Using eddy correlation analysis, the heat flux values were calculated (virtual heat fluxes varied from − 60 to 40 W/m²) and it was found that they are affected by the limited spatial and temporal scales of the responding air–sea interaction mechanism. Similarly, the humidity fluxes appeared to be strongly influenced by the observed intense spatial heterogeneity of the sea surface temperature.

Kostopoulos VE, Helmis CG, 2014: Flux measurements in the surface marine Atmospheric Boundary Layer over the Aegean Sea, Greece, Science of the Total Environment, 494-495, 166-176, doi:10.1016/j.scitotenv.2014.06.127. Article (subscription required).

Distribution and biological features of the common pandora, Pagellus erythrinus (Linnaeus, 1758), in the southern Tyrrhenian Sea (Central Mediterranean)

administrator — Wed, 30 Jul 2014 07:56:59 +0000

A synthetic analysis of the distribution, abundance and some biological traits of the common pandora (Pagellus erythrinus) was performed. Data were gathered in 15 experimental bottom trawl surveys carried out off the southern Tyrrhenian Sea from 1994 to 2008. A total of 2,166 P. erythrinuswere found in the investigated area, with a preference for the upper continental shelf (10–100 m). The highest persistence was recorded in the trawl-banned areas. The sex ratio Sr = F/(F + M) ranged between 0.60 and 0.96 (overall 0.78). The size at which 50 % of the individuals were mature was 157 and 170 mm total length for females and males, respectively. The length–weight relationship for all individuals was described by the following parameters: a = 0.016 and b = 2.905. Growth was evaluated (sexes combined) by applying length-based methods; up to eight significant modal components were evidenced. The von Bertalanffy growth parameters for the whole population were estimated at L _∞ = 454 mm, K = 0.08 and t ₀ = −2.57. The present results are in agreement with the information available for the other Mediterranean stocks suggesting common biological features.

Busalacchi B, Bottari T, Giordano D, Profeta A, Rinelli P, in press: Distribution and biological features of the common pandora, Pagellus erythrinus (Linnaeus, 1758), in the southern Tyrrhenian Sea (Central Mediterranean), Helgoland Marine Research, doi:10.1007/s10152-014-0404-5. Article (subscription required).