NW Mediterranean Waters Research Articles

Taxonomic review of Gallardonerisnonatoi (Ramos, 1976) comb. nov. (Annelida, Lumbrineridae), and description of a new species of Lumbrineris from the Gulf of Mexico.

The small LumbrineridaeGallardonerisiberica Martins, Carrera-Parra, Quintino & Rodrigues, 2012 was first described as new to science based on specimens from Portuguese waters. Then, it was successively reported from several south European areas, including Spain, Italy, Greece, and Cyprus. Here evidence is presented that G.iberica should be placed in synonymy with Lumbrinerisnonatoi Ramos, 1976, originally described from NW Mediterranean waters, a species that fits with the diagnosis of Gallardoneris. Based on specimens from the French coasts of the NW Mediterranean, this paper (1) redescribes the species using the new combination Gallardonerisnonatoi (Ramos, 1976) and (2) provides a morphometric analysis of its main morphological characters. The lack of recent reports of G.nonatoi comb. nov. in Mediterranean waters is presumably due to the recent redescription of the species as L.nonatoi based on specimens from the Gulf of Mexico. However, these specimens belong to Lumbrineris, as currently defined. By assessing their morphological differences, it is concluded that the specimens from the Gulf of Mexico represent a different and new species, namely Lumbrinerisjan sp. nov. Also discussed is the possible assignation of Lumbrinerislongipodiata Cantone, 1990, a poorly known species seldom recorded since its original description from the Gulf of Catania (Mediterranean Sea) to Gallardoneris, as well as on whether it is a valid species or may be an additional junior synonym of G.nonatoi comb. nov.

Life strategies and habitat preferences of Bythitidae and Zoarcidae, specialized fishes with particular life histories, in the Mediterranean deep sea

Deep-sea habitats are home for a variety of yet poorly known fish species, some of which display specialized life strategies, as is the case of Bythitidae and Zoarcidae. With the purpose of elucidating biological and ecological aspects of representatives of these families in NW Mediterranean waters, a large dataset based on 599 specimens of Cataetyx alleni, 30 C. laticeps and 284 Melanostigma atlanticum captured during the last 30 years within the framework of different research projects was used to address their geographical and bathymetric distribution, population structure, reproduction, trophic ecology, parasitism and enzymatic markers in the Balearic basin. Present outcomes revealed a patchy distribution mostly for M. atlanticum, possibly related to aggregation during reproduction and to the association with specific sediments. For the three species, higher densities occurred in the mainland vs. the insular margin, and a diminishing trend in estimated densities over the last decades was observed for C. alleni and M. atlanticum likely linked to climatic oscillations. Trophic data indicated that the two Cataetyx species inhabit the water-sediment interface and mainly feed on suprabenthic prey, while M. atlanticum inhabits the water column near the bottom preying on pelagic organisms and moving towards the seabed during reproduction. These results were supported by the parasitological assessment, which revealed that parasite communities were moderately diverse and abundant for Cataetyx spp. while being highly depauperate for M. atlanticum. Present outcomes from the Mediterranean Sea confirmed reproduction of C. alleni during autumn-winter and of M. atlanticum during autumn. Spawning of the former species may occur in winter-spring, as suggested by the finding, by the first time, of two females captured in March with fully-developed embryos inside. Levels of enzymatic markers quantified in muscle were provided for C. alleni and M. atlanticum for the first time. The special interactions found between the distribution and biology of Bythitidae and Zoarcidae and the sedimentary bottoms that they inhabit indicates that such conventional habitats are more heterogeneous than it is generally assumed and deserve higher attention for future protection.

Captures of Molva molva (Linnaeus, 1758) still happen in NW Mediterranean waters

The ling Molva molva is a widespread gadid in the Northeast Atlantic and one example of a poorly studied species of particular interest, being its distribution affected by climate warming. The ling supposedly occurs in the cold waters of the Northwestern Mediterranean Sea, where it used to be commonly fished, but to our best knowledge, records of M. molva after the 1990s are not availa-ble from the scientific literature. Here we report the recent capture of two individuals, one of them of considerable size, at 35 nautical miles off the coast of Castelló (Spain, NW Mediterranean).

Temporal evolution of 137Cs, 237Np, and 239+240Pu and estimated vertical 239+240Pu export in the northwestern Mediterranean Sea

The evolution of 137Cs, 237Np and 239+240Pu at the DYFAMED station (NW Mediterranean) is discussed in relation to physical processes, downward fluxes of particles, and changes in the main input sources. The data set presented in this study represents the first complete 237Np vertical profiles (0.12–0.27μBqL−1), and constitutes a baseline measurement to assess future changes. A similar behavior of Cs and Np has been evidenced, confirming that Np behaves conservatively. While the 137Cs decrease has been driven by its radioactive decay, the vertical distribution of 237Np has not substantially changed over the last decade. In the absence of recent major inputs, a homogenization of their vertical distribution occurred, partly due to deep convection events that became more intense during the last decade. In contrast, 239+240Pu surface levels in the NW Mediterranean waters have fallen in the past four decades by a factor of 5. This decrease in surface has been balanced by higher concentrations in the deep-water layers. A first estimate of the downward 239+240Pu fluxes in the NW Mediterranean Sea is proposed over more than two decades. This estimation, based on the DYFAMED sediment trap time-series data and published 239+240Pu flux measurements, suggests that sinking particles have accounted for 60–90% of the upper layer (0–200m) Pu inventory loss over the period 1989–2013. The upper layer residence time of Pu is estimated to be ~28years, twice as long as the residence time estimated for the whole western Mediterranean (~15years). This difference highlights the slow removal of Pu in the open waters of the NW Mediterranean and confirms that most of the Pu removal occurs along the coastal margin where sedimentation rates are high.

Bio-optical characterization of offshore NW Mediterranean waters: CDOM contribution to the absorption budget and diffuse attenuation of downwelling irradiance

We investigated the peculiar bio-optical characteristics of the Mediterranean Sea focusing on the spectral diffuse attenuation coefficient [Kd (λ)] and its relationship with chlorophyll a concentration (Chl a), complemented with measurements of light absorption by chromophoric dissolved organic matter (CDOM) and the optical properties of particulate material. The non-water absorption budget showed that CDOM was the largest contributor in the 300–600nm range (>60% of the absorption at 443nm in the euphotic layer), increasing to 80% within the first optical depth (FOD). This translated into CDOM accounting for >50% of KdBio (λ) (the irradiance attenuation coefficient caused by all non-water absorptions) between 320 and 555nm and throughout both layers (FOD and euphotic). Indeed, we tested three Chl a-based bio-optical models and all three underestimated Kd (λ), evidencing the importance of CDOM beside Chl a to fully account for light attenuation. The Morel & Maritorena (2001) model (M&M 01) underestimated Kd (λ) in the UV and blue spectral regions within the FOD layer, showing lower differences with increasing wavelengths. The Morel et al. (2007a) model (BGS 07) also underestimated Kd (λ) in the FOD layer, yet it performed much better in the 380–555nm range. In the euphotic layer, the Morel (1988) model (JGR 88) underestimated Kd ( λ) showing higher differences at 412 and 443nm and also performed better at higher wavelengths. Observed euphotic layer depths (Z1%) were 28m shallower than those predicted with the M&M 01 empirical relationship, further highlighting the role of CDOM in the bio-optical peculiarity of Mediterranean Sea. In situ measurements of the CDOM index (Φ), an indicator of the deviation of the CDOM-Chl a average relationship for Case 1 waters, gave a mean of 5.9 in the FOD, consistent with simultaneous estimates from MODIS (4.8±0.4). The implications of the bio-optical anomaly for ecological and biogeochemical inferences in the Mediterranean Sea are discussed.

Parasite communities of the deep-sea fish Alepocephalus rostratus Risso, 1820 in the Balearic Sea (NW Mediterranean) along the slope and relationships with enzymatic biomarkers and health indicators

This study examines the parasite communities of Alepocephalus rostratus and its influence on some fish biochemical markers and histological alterations. A. rostratus constitutes the second most important fish species, in terms of biomass, inhabiting the deep slope of the Catalan Sea (Balearic Sea, NW Mediterranean). The study revealed eight different parasite species in this host: one coccidian, one digenean, one monogenean, one cestode and four nematodes. The parasite fauna of A. rostratus was partially dominated by larval forms (four of the seven metazoan taxa found), which combined with low species richness corresponds to a parasite fauna pattern more typical of bathypelagic fish species rather than demersal ones. The larval tetraphyllideans and cucullanid nematodes were the predominant species. In relation to depth, differences in abundance of the nematodes Cucullaninae gen. sp. and Hysterothylacium aduncum were found, probably due to the dietary shift in the fish host at greater depth. Thus, Cucullaninae gen. sp. and H. aduncum could be regarded as indicators for discriminating populations of A. rostratus in relation to depth in NW Mediterranean waters. Of the biochemical markers examined, acetylcholinesterase (AChE) and lactate dehydrogenase (LDH) activities and lipid peroxidation (LP) levels, only LP showed significant differences between depths. A positive relationship was found between AChE activity and Tetraphyllidea fam. gen. sp., Anisakis physeteris and H. aduncum abundance and a negative one with the abundance of Cucullaninae gen. sp. LDH showed a positive relationship with the abundance of the parasites Paracyclocotyla cherbonnieri and Tetraphyllidea fam. gen. sp. At cyto-histological level, coccidians were detected in the pyloric caeca with a prevalence of 90% in Barcelona, but in the rest of organs almost no alterations were detected. The restricted macroplanktonic diet of A. rostratus, that maintains it distant from the sea-floor for longer periods than other demersal species, probably makes this species less susceptible to sediment-associated impacts including parasitism.

An annual survey of bacterial production, respiration and ectoenzyme activity in coastal NW Mediterranean waters: temperature and resource controls.

We simultaneously measured bacterial production (BP), bacterial respiration (BR), alkaline phosphatase activity (phos) and ectoaminopeptidase activity (prot) in relation to biogeochemical parameters, nutritive resources and in situ temperature over a 1-year survey at the long-term observatory the SOLEMIO station (Marseille bay, NW Mediterranean Sea). Despite its proximity to the coast, oligotrophic conditions prevailed at this station (yearly mean of Chl a = 0.43 μg dm(-3), NO3 = 0.55 μmol dm(-3) and PO4 = 0.04 μmol dm(-3)). Episodic meteorological events (dominant winds, inputs from the Rhone River) induced rapid oscillations (within 15 days) in temperature and sometimes salinity that resulted in rapid changes in phytoplankton succession and a high variability in C/P ratios within the particulate and dissolved organic matter. Throughout the year, BP ranged from 0.01 to 0.82 μg C dm-(3) h-(1) and bacterial growth efficiency varied from 1 to 39%, with higher values in summer. Enrichment experiments showed that BP was limited most of the year by phosphorus availability (except in winter). A significant positive correlation was found between in situ temperature, BP, BR and phos. Finally, we found that temperature and phosphate availability were the main factors driving heterotrophic bacterial activity and thus play a fundamental role in carbon fluxes within the marine ecosystem.

Temperature effects on the heterotrophic bacteria, heterotrophic nanoflagellates, and microbial top predators of the NW Mediterranean

Prokaryotes and protists are important players in the carbon biogeochemistry of mar- ine ecosystems, and temperature is one of the physical factors most influential in the metabolism and composition of plankton communities. Small changes in temperature can change the flow of carbon and the community structure of planktonic ecosystems, and climatological models predict a rise in temperature of 2 to 5°C toward the end of the century in the NW Mediterranean. Labora- tory culture experiments have shown that warming can increase the transfer of carbon between bacteria and protists and alter the community composition of microbial top predators (i.e. ciliates and dinoflagellates) by increasing the abundance of bacterivores and producing the extinction of herbivores. Here, we tested whether a small rise in temperature would produce these effects in the coastal Mediterranean. Between March 2003 and February 2004, we established 12 micro- cosm experiments with water from the Bay of Blanes. The samples were incubated for 48 h at ambient and warmer temperatures (~2.7°C higher than in situ values), and the net and gross growth rates of bacteria and heterotrophic nanoflagellates (HNF) were measured using unfiltered and 0.8 µm filtered treatments. Warming increased the rates of bacterial gross production and bacterial losses to grazing with a clear seasonality; the largest increments in the rates were observed during the cooler months of the year. Warming did not change the net growth rates of dinoflagellates. It decreased the net production of HNF and the net growth rates of ciliates but did not promote the extinction of herbivorous protists. Temperature changed the microbial food web function in NW Mediterranean waters, with small alterations in the community composition of microbial top predators.

Inorganic nutrient control of dissolved organic carbon (DOC) dynamics in NW Mediterranean waters: An experimental approach

In order to understand the microbial processes controlling seasonal DOC accumulation in NW Mediterranean Sea surface waters, nutrient addition experiments were conducted. The dynamics of DOC as well as the response of heterotrophic bacteria in terms of abundance, activity, and community composition were investigated in October, January, March, and July of 2006–2007. During the summer stratified period, the addition of phosphorus (at 0.1 and 1 µM final concentrations), as well as nitrogen and phosphorus (at 10 µM N and 1 µM P) yielded marked decreases in DOC concentrations. Bacterial DOC consumption was 5.6 µM C per day in the low phosphorus treatment, 8.6 µM C per day in the high phosphorus treatment, and 8 µM C per day in the nitrogen plus phosphorus treatment. Most, but not all experiments, showed a clear decrease in the DOC concentrations when amended with phosphorus, even when in-situ concentrations were low. The addition of phosphorus also enhanced bacterial production and caused changes in the community composition of the bacterioplankton. The phosphorus limitation of bacterial activity and the changes in the relative abundance of specific phylotypes upon relieving nutrient limitation might explain the low DOC consumption rates during the summer stratified period.

Revisiting the dilution technique to quantify the role of microzooplankton in DMS(P) cycling: laboratory and field tests

With the aim of re-examining the suitability of the dilution technique in studies of dimethylated sulfur cycling in the sea, we conducted two types of experiments: one with a simplified food chain of cultured organisms, and secondly with field-sampled natural communities. In the case of Isocrhysis galbana being grazed by Oxyrrhis marina, algal growth (μ) and grazing mortality (m) rates calculated using either chlorophyll a (Chla) or particulate dimethylsulfoniopropionate (DMSPp) were very similar. By means of a parallel incubation of prey with no predator, the regression-derived phytoplankton μ was validated. Net 24-h changes in DMS concentration showed a linear trend against DMSP grazing rates, with a slope that allowed estimation of the rate of DMS production due to grazing. When the method was applied to natural communities from coastal NW Mediterranean waters, μ values of the bulk Chla-containing phytoplankton assemblage were higher than that of the DMSP-containing algae, but m were not significantly different. The grazing-mediated DMS production rate was successfully estimated, and parallel incubations with and without a specific inhibitor of bacterial DMS metabolism allowed us to estimate the gross DMS production by the whole community and the bacterial DMS consumption rate. A further experiment showed that bacterial consumption was not affected by dilution.

Feeding ecology of the marine cladoceran Penilia avirostris: natural diet, prey selectivity and daily ration

Penilia avirostris is an important component of the mesozooplankton of shelf waters dur- ing the stratification period. This study investigates the feeding ecology of P. avirostris under natural dietary conditions in the NW Mediterranean during their summer appearance. The results indicate that P. avirostris feeds on particles in a wide size range, mostly on nanoplankton (2 to 20 µm), includ- ing larger prey such as dinoflagellates and ciliates. Autotrophic and heterotrophic bacteria were not grazed on, but picoflagellates (<2 µm) were significant contributors to diet, indicating a narrow threshold of lower prey size. Ciliates were cleared at low rates which, at times, were not significant, probably because of their ability to escape feeding currents. Although this marine cladoceran is con- sidered to behave like a filter feeder, our results indicate that it can display variable selectivity pat- terns that do not only depend on prey size. During the strict oligotrophic conditions that were present in summer NW Mediterranean waters, daily rations of P. avirostris averaged 82% body C d -1 (range: 26 to 157%). Such feeding rates seem to be an adaptation to allow them to succeed under low food conditions and outcompete other components of the marine zooplankton, such as copepods.

Atlas of Northwestern Mediterranean Coccolithophores

The present Atlas contains a detailed study, based in scanning electron microscopy (SEM) observations, of living coccolithophores from NW Mediterranean waters. The study contains 103 figures with 411 micrographs, which correspond to 168 coccolithophores (including different taxonomic and morphotypic entities). The figured specimens were collected during different cruises carried out from 1995 to 1999.Classification of the organisms follows modern taxonomy of living calcareous nannoplankton. Measures of the specimens and notes on their taxonomy are given in addition to abridged descriptions of the studied taxa. The atlas contains a large number of previously undescribed forms, specially in the genera Syracosphaera, Papposphaera, Polycrater, Anthosphaera, Corisphaera and Sphaerocalyptra . Several species never illustrated in the literature are presented here for the first time. Coccospheres having coccoliths of different recognized species are presented. These combination coccospheres are nowadays considered as transitional steps between different phases in the cellular life-cycle. An introduction with a brief overview of the actual coccolithophore knowledge and an abridged glossary with figures of the basic terminology are included.

Annual Zooplankton Succession in Coastal NW Mediterranean Waters: The Importance of the Smaller Size Fractions

Zooplankton abundance, biomass (biovolume) and taxonomic composition were studied within an annual cycle (August 1995-October 1996) in the Bay of Blanes (northwest Mediterranean). Weekly zooplankton sampling included oblique tows made with a 200 μm Juday-Bogorov net, and vertical tows made with a 53 μm net, to adequately sample both mesoplankton and the smaller zooplankton fractions. Total zooplankton abundance showed high variability, lacking any clear seasonal pattern. However, the different species within the zooplankton community displayed a clear succession throughout the year. In general, cyclopoid copepods (Oithona spp.) and cladocerans (Penilia wirostris) dominated the summer and autumn communities, whereas in winter and spring, calanoid copepods (Clausocalanus spp., Paracalanus sp. and Centropages typicus) were predominant. The zooplankton annual cycle in the Bay of Blanes does not resemble those of other Mediterranean littoral areas, probably due to the inherent particularity and variability associated with open coastal environments. On average, the abundance of organisms estimated with a traditional 200 μm Juday-Bogorov net was 8.1 times lower than the values obtained with a 53 μm net. Even if only organisms >200 μm collected in the 53 μm tows were considered, the total abundance within the 53 μm net was still 4.4 times higher than the estimates from the Juday-Bogorov net. These results suggest the need for accurate samplings of the entire zooplankton assemblage when characterizing the structure and dynamics of zooplanktonic communities.