Basin scale distribution of zooplankton in the Ligurian Sea (north-western Mediterranean) in late autumn

Mesozooplankton biomass and abundance were evaluated in epipelagic waters at 59 stations covering the Italian sector of the Ligurian Sea (north-western Mediterranean) in December 1990. This region is characterised by a cyclonic circulation which encloses a central divergence zone and is associated with a main thermohaline front offshore the western Ligurian coast. At the end of autumn, mesozooplankton biomass (range: 0.80–4.24 mg DW m−3) and the abundance (range: 83.8–932 ind. m−3) were lower in the divergence zone. On the contrary, in the Ligurian frontal zone at the periphery of the divergence and on the eastern continental shelf the greatest values of biomass and abundance were recorded. Copepods and appendicularians dominated the mesozooplankton community, the main taxa being the copepods Clausocalanus spp. (46% of total zooplankton) and Oithona spp. (15%) and the appendicularian Fritillaria spp. (12%). Three hydrological sub-regions, i.e. the divergence, the eastern continental shelf and the periphery of the divergence, were characterised by different zooplankton communities and characteristic species. Environmental differences between the three zones were mainly related to changes in bottom topography, sea surface temperatures and quantity of particulate organic matter. Vertical mesozooplankton abundance and taxa distribution from the surface to 1,900 m depth were also examined in one station. The results showed that the bulk of the community was concentrated in the upper 200 m, small copepods being dominant particularly in the upper 50 m. The copepod community was more diversified in sub-superficial waters, with a maximum observed in the 200–400 m layer. The distributions of main zooplankton taxa described in epipelagic waters in the eastern Ligurian Sea in autumn were compared with their distribution at surface in the north-western Mediterranean obtained by sampling performed with the Continuous Plankton Recorder in 1997–1999. The analysis of the zooplankton community in CPR samples confirms the dominance of small copepods (Paracalanus spp., Clausocalanus spp., Oithona spp.) and appendicularians in the north-western Mediterranean in late autumn-winter and shows that their distribution is mainly related to the main mesoscale hydrographic features characterising this basin.

Lamellibrachia anaximandrin. sp., a new vestimentiferan tubeworm (Annelida) from the Mediterranean, with notes on frenulate tubeworms from the same habitat

A new species of lamellibrachiid vestimentiferan, Lamellibrachia anaximandri n. sp., has been found in the Eastern Mediterranean, close to cold seeps of fluid carrying dissolved methane and sources of sulfide in superficial sediments. It occurs at about 1100 to 2100 m depth, on some of the mud volcanoes on the Anaximander Mountains, south of Turkey, on the Mediterranean Ridge, south of Crete, and on the Nile deep-sea fan. In addition, it has been obtained from rotting paper inside a sunken ship, torpedoed in 1915 and lying at 2800 m depth, southeast of Crete. Some frenulate pogonophores also occur on the mud volcanoes (including a species of Siboglinum resembling S. carpinei and tubes of other unidentified genera). The new Lamellibrachia is the first vestimentiferan species to be described from the Mediterranean. It differs from L. luymesi taken from the Gulf of Mexico population in the very weak development of collars on its tube and in having a smaller number of pairs of branchial lamellae in the branchial plume. Sequencing of the COI and the mt16S genes confirms a difference at the species level between the new species and L. luymesi, and a difference between these two species and four described species of Lamellibrachia from the Pacific Ocean. The largest individuals of L. anaximandri n. sp. may be many years old, but there are numerous young individuals at some sites, showing that favourable conditions are available for settlement and early growth. The development of the branchial plume in a series of young stages reveals that the sheath lamellae, which are characteristic of the genus Lamellibrachia, begin to form only after the establishment of several pairs of branchial lamellae. Examination of the adult trophosome by transmission electron microscopy shows Gram-negative bacteria without internal stacked membranes, indicating that the symbionts are most probably sulfide oxidizing.

Continuous Plankton Records - Geographical Variations In Numerical Abundance Biomass And Production Of Euphausiids In The North-Atlantic Ocean And The North-Sea

Geographical variations in the numbers, biomass and production of euphausiids and the contribution of common species to the total are described from samples taken during 1966 and 1967 in the North Atlantic Ocean and the North Sea by the Continuous Plankton Recorder at 10 m depth. Euphausiids were most abundant in the central and western North Atlantic Ocean and the Norwegian Sea. Thysanoessa longicaudata (Krøyer) was numerically dominant. Biomass was greatest in the Norwegian Sea and the north-eastern North Sea where Meganyctiphanes norvegica (M. Sars) accounted for 81 and 59%, respectively, of the total biomass. Production was highest off Nova Scotia and in Iberian coastal waters; the dominant species were T. raschi (M. Sars) in the former area and Nyctiphanes couchi (Bell) in the latter. The mean P:B ratios were correlated with temperature.

Regional and annual variation in black-legged kittiwake breeding productivity is related to sea surface temperature

Spatiotemporal variation in seabird demographic parameters is often pronounced and may be an important source of information on the state of marine ecosystems. Black-legged kittiwakes Rissa tridactyla in Britain and Ireland show strong regional structure in breeding productivity, and both temporal and spatial variation are probably related to abundance of the principal prey of breeding kittiwakes, the lesser sandeel Ammodytes marinus. Annual regional estimates of sandeel abundance do not exist, prohibiting direct tests of this hypothesis. We examined relationships between kittiwake breeding productivity and 2 potential proxies of sandeel abundance, winter sea surface temperature (SST) and abundance of Calanus copepods, within and among 6 regions in Britain and Ireland from 1986 to 2004. Means and trends in winter SST differed among regions, with higher means and less pronounced increasing trends in western (Atlantic) regions than in eastern (North Sea) regions. A negative relationship between breeding productivity and winter SST in the previous year was found within 2 regions (East Scotland and Orkney), as well as in a cross-regional analysis. Results were inconclusive for Calanus abundance, with a positive relationship in East Scotland and negative in Orkney. These results demonstrate that although a single environmental driver (SST) is related to both within- and between-region variation in a key demographic parameter, regional heterogeneity in SST trends as well as the importance of other factors may lead to highly variable responses. Understanding this heterogeneity is critical for predicting long-term effects of climate change or other anthropogenic drivers on marine ecosystems.

A blooming jellyfish in the northeast Atlantic and Mediterranean

A long-term time series of plankton records collected by the continuous plankton recorder (CPR) Survey in the northeast Atlantic indicates an increased occurrence of Cnidaria since 2002. In the years 2007 and 2008, outbreaks of the warm-temperate scyphomedusa, Pelagia noctiluca, appeared in CPR samples between 45° N to 58° N and 1° W to 26° W. Knowing the biology of this species and its occurrence in the adjacent Mediterranean Sea, we suggest that P. noctiluca may be exploiting recent hydroclimatic changes in the northeast Atlantic to increase its extent and intensity of outbreaks. In pelagic ecosystems, Cnidaria can affect fish recruitment negatively. Since P. noctiluca is a highly venomous species, outbreaks can also be detrimental to aquaculture and make bathing waters unusable, thus having profound ecological and socio-economic consequences.

Mediterranean marine copepods: basin-scale trends of the calanoid Centropages typicus

The Mediterranean Sea is located in a crossroad of mid-latitude and subtropical climatic modes that enhance contrasting environmental conditions over both latitudinal and longitudinal ranges. Here, we show that the large-scale environmental forcing is reflected in the basin scale trends of the adult population of the calanoid copepod Centropages typicus. The species is distributed over the whole Mediterranean basin, and maximal abundances were found in the north-western basin associated to oceanic fronts, and in the Adriatic Sea associated to shallow and semi enclosed waters. The peak of main abundances of C. typicus correlates with the latitudinal temperature gradient and the highest seasonal abundances occurred in spring within the 14–18°C temperature window. Such thermal cline may define the latitudinal geographic region where C. typicus seasonally dominates the >200 μm-sized spring copepod community in the Mediterranean Sea. The approach used here is generally applicable to investigate the large-scale spatial patterns of other planktonic organisms and to identify favourable environmental windows for population development.

Indications of a climate effect on Mediterranean fisheries

Using the Food and Agriculture Organization’s (FAO) Mediterranean capture fisheries production dataset in conjunction with global and Mediterranean sea surface temperatures, we investigated trends in fisheries landings and landings per unit of effort of commercially important marine organisms, in relation to temperature oscillations. In addition to the overall warming trend, a temperature shift was detected in the Mediterranean Sea in the late 1990s. Fisheries landings fluctuations were examined for the most abundant commercial species (59 species) and showed significant year-to-year correlations with temperature for nearly 60 % of the cases. From these, the majority (~70 %) were negatively related and showed a reduction of 44 % on average. Increasing trends were found, mainly in the landings of species with short life spans, which seem to have benefited from the increase in water temperature. Τhe effect of oceanic warming is apparent in most species or groups of species sharing ecological (e.g. small and medium pelagic, demersal fish) or taxonomic (e.g. cephalopods, crustaceans) traits. A landings-per-unit-of-effort (LPUE) proxy, using data from the seven Mediterranean European Union member states, also showed significant correlation with temperature fluctuations for six out of the eight species examined, indicating the persistence of temperature influence on landings when the fishing effect is accounted for. The speed of response of marine landings to the warming of the Mediterranean Sea possibly shows both the sensitivity and the vulnerable state of the fish stocks and indicates that climate should be examined together with fisheries as a factor shaping stock fluctuations.

Exposure of Mediterranean Countries to Ocean Acidification

This study examines the potential effects of ocean acidification on countries and fisheries of the Mediterranean Sea. The implications for seafood security and supply are evaluated by examining the sensitivity of the Mediterranean to ocean acidification at chemical, biological, and macro-economic levels. The limited information available on impacts of ocean acidification on harvested (industrial, recreational, and artisanal fishing) and cultured species (aquaculture) prevents any biological impact assessment. However, it appears that non-developed nations around the Mediterranean, particularly those for which fisheries are increasing, yet rely heavily on artisanal fleets, are most greatly exposed to socioeconomic consequences from ocean acidification.

Predicting future thermal habitat suitability of competing native and invasive fish species: from metabolic scope to oceanographic modelling

Global increase in sea temperatures has been suggested to facilitate the incoming and spread of tropical invaders. The increasing success of these species may be related to their higher physiological performance compared with indigenous ones. Here, we determined the effect of temperature on the aerobic metabolic scope (MS) of two herbivorous fish species that occupy a similar ecological niche in the Mediterranean Sea: the native salema (Sarpa salpa) and the invasive marbled spinefoot (Siganus rivulatus). Our results demonstrate a large difference in the optimal temperature for aerobic scope between the salema (21.8°C) and the marbled spinefoot (29.1°C), highlighting the importance of temperature in determining the energy availability and, potentially, the distribution patterns of the two species. A modelling approach based on a present-day projection and a future scenario for oceanographic conditions was used to make predictions about the thermal habitat suitability (THS, an index based on the relationship between MS and temperature) of the two species, both at the basin level (the whole Mediterranean Sea) and at the regional level (the Sicilian Channel, a key area for the inflow of invasive species from the Eastern to the Western Mediterranean Sea). For the present-day projection, our basin-scale model shows higher THS of the marbled spinefoot than the salema in the Eastern compared with the Western Mediterranean Sea. However, by 2050, the THS of the marbled spinefoot is predicted to increase throughout the whole Mediterranean Sea, causing its westward expansion. Nevertheless, the regional-scale model suggests that the future thermal conditions of Western Sicily will remain relatively unsuitable for the invasive species and could act as a barrier for its spread westward. We suggest that metabolic scope can be used as a tool to evaluate the potential invasiveness of alien species and the resilience to global warming of native species.