Assessment of cetacean–fishery interactions in the marine food web of the Gulf of Taranto (Northern Ionian Sea,Central Mediterranean Sea)

Reviews in Fish Biology and Fisheries - The exploitation of fishery resources acts as a driving force on cetaceans both directly, by determining their fishing mortality or injury as by-catch...     

Seasonal monitoring of coral–algae interactions in fringing reefs of the Gulf of Aqaba, Northern Red Sea

This paper presents seasonal in situ monitoring data on benthic coverage and coral–algae interactions in high-latitude fringing reefs of the Northern Red Sea over a period of 19 months. More than 30% of all hermatypic corals were involved in interaction with benthic reef algae during winter compared to 17% during summer, but significant correlation between the occurrence of coral–algae interactions and monitored environmental factors such as temperature and inorganic nutrient availability was not detected. Between 5 and 10-m water depth, the macroalgae Caulerpa serrulata, Peyssonnelia capensis and filamentous turf algae represented almost 100% of the benthic algae involved in interaction with corals. Turf algae were most frequently (between 77 and 90% of all interactions) involved in interactions with hermatypic corals and caused most tissue damage to them. Maximum coral tissue loss of 0.75% day⁻¹ was observed for Acropora-turf algae interaction during fall, while an equilibrium between both groups of organisms appeared during summer. Slow-growing massive corals were more resistant against negative algal influence than fast-growing branching corals. Branching corals of the genus Acropora partly exhibited a newly observed phenotypic plasticity mechanism, by development of a bulge towards the competing organism, when in interaction with algae. These findings may contribute to understand the dynamics of phase shifts in coral reefs by providing seasonally resolved in situ monitoring data on the abundance and the competitive dynamic of coral–algae interactions.     

Ostreopsis cf. ovata in the Gulf of Gabès (south-eastern Mediterranean Sea): morphological,molecular and ecological characterization

In the last few decades, the frequency of the toxic benthic dinoflagellate Ostreopsis cf. ovata proliferation has increased in the Mediterranean Sea. These blooms are associated with harmful effects on human health and the environment. The present work provides the first long term study on the spatio-temporal distribution of O. cf. ovata in relation to physical parameters in the Gulf of Gabès coastal waters (south-eastern Mediterranean Sea), as well as its morphological, molecular and physiological features. The strains of O. cf. ovata were identified morphologically by light and epifluorescence microscopy. The morphology and the size range of cultured strains were similar to those described regarding O. cf. ovata isolated from the Mediterranean Sea. The ultrastructural analysis of O. cf. ovata cells using the transmission electron microscopy showed the presence of numerous vesicles (VE) containing spirally coiled fibers (SCFs) connected to the mucus canal (CH). The phylogenetic tree based on the internal transcribed spacer region containing the 5.8S rDNA (ITS-5.8S rDNA) revealed that O. cf. ovata strains were placed into the Mediterranean/Atlantic clade. In addition, O. cf. ovata toxicity was evaluated by the mouse bioassay and a dose level ≥ 4 × 10⁴ cells was found to be lethal to mice. The examination of the O. cf. ovata occurrence in the Gulf of Gabès at a large temporal scale (1997–2012) revealed a clear seasonal pattern with dominance from midsummer (July) to late autumn (November). Furthermore, a positive correlation was found between the abundance of O. cf. ovata and salinity, whereas no correlation was found as regards temperature. The occurrence of O. cf. ovata was only detected at salinity above 35 and the highest concentrations were observed at 45. Laboratory experiments confirmed such a result and showed that isolated O. cf. ovata strains had optimal growth at salinity ranging between 35 and 45, with its peak at 40.     

Is it possible to calibrate the pollution level of the region of Algiers (Mediterranean Sea) by exploiting marine macrophytes?

In the absence of water-quality data, a biological indicator is the only way to estimate the pollution level. Samples of macrophytes from exposed shallow rocky substrata of the region of Algiers (Algeria, Mediterranean Sea) were collected in supposedly (in the absence of available pollution data) polluted and pristine waters. These samples were compared to a set of samples spanning a known pollution gradient found near Marseilles (France) and to some samples from a variety of other Mediterranean localities. All samples were collected in similar conditions. The diversity point (i.e., the number of species per sample) was not greater at Cherchell (control site) than at the three sites in the Bay of Algiers. Analysis of the dataset was successful in ranking the Algerian sites, but failed to calibrate the pollution level of the Algerian sites by inserting Algerian samples within the pollution gradient of Marseilles. In contrast, regional characteristics of the macrophyte communities appear to be largely prevalent. This means that water-quality biological indicators and indices based upon marine macrophytes, at least for the open waters and exposed shallow Mediterranean habitats studied here, could be reliable within a given region, but may require validation and/or adjustment, perhaps considerable, for other regions.     

Reproductive biology of the lessepsian Reticulated leatherjacket Stephanolepis diaspros (Fraser - Brünner, 1940) in the Gulf of Gabes (Eastern Mediterranean Sea)

Fundamental information on the reproductive biology of the lessepsian fish Reticulated leatherjacket Stephanolepis diaspros from the Gulf of Gabes (Eastern Mediterranean Sea) was considered in this study. The study was carried out on a sample of 1,053 specimens of the Reticulated leatherjacket caught by trawlers and were monthly collected from May 2003 to December 2005. The length frequency distribution indicated that males are taller than females. The sex-ratio was 0.87:1 which significantly deviated from the hypothetical distribution of 1:1. The size and the season have an effect on this sex-ratio. Gonadosomatic Index (GSI%) values were highest in July for both sexes and this species accumulates energy reserves in the liver to be spent during the maturity of gonads and the spawning. First maturation occurred at 7.96 cm for females and 10.58 cm (L₅₀) for males. The fecundity of S. diaspros ranged from 28,250 to 218,000 with a mean of 100,778.76 ± 17,702.1. The relationships between absolute fecundity and total length, eviscerated weight and weight of gonads were will described and the correlation coefficients calculated between fecundity and each of these independent variables, are judged to be either significant (R² > 0.8) indication of a very good model for the fecundity study.     

Diet of juvenile cod (age 0–2) in the Barents Sea in relation to food availability and cod growth

Diet investigations were carried out on 0-, 1- and 2-year-old Northeast Arctic cod (Gadus morhua) sampled in the Barents Sea during 1984–2002. Stomach-content analyses showed that the 0 and 1 group cod fed mainly on crustaceans, with krill and amphipods composing up to 70% of their diet. Krill (Thysanoessa spp. and Meganyctiphanes norvegica) and amphipods (Themisto spp.) were mainly found in cod stomachs sampled in the central and close to the Polar Front region in the Barents Sea where these prey organisms are reported to be abundant in summer. A shift in the main diet from crustaceans to fish was observed from age 1 to age 2. The diet of 2-year-old cod mainly comprised capelin (Mallotus villosus) and other fish, and to a lesser degree, krill and amphipods. Shrimp (mainly Pandalus spp.) was also an important prey in both age 1 and 2 cod. A statistically significant positive relationship was obtained between capelin stock size and the amount of capelin in the diet of 2-year-old cod. Results from this study also show that the larger age-2 cod preyed more on capelin in winter and that larger cod (>22 cm) prefer larger capelin (>12 cm). During periods of low capelin abundance, the 2-year-old cod shift their diet more to crustaceans, such as krill and amphipods. A positive significant relationship was also obtained between Total Fullness Index (TFI) and the amount of capelin in the diet and between TFI and the growth of 2-year-old cod, indicating that the growth of age-2 cod is to a large extent dependent on the amount of capelin consumed. Growth of age-1 cod was also positively correlated to TFI.     

Seasonal variation in stable C and N isotope ratios of the Rhone River inputs to the Mediterranean Sea (2004–2005)

The temporal variation in the stable carbon and nitrogen isotope ratios of particulate organic matter (POM) in the Rhone River was investigated on a monthly basis during a 2-year period (2004–2005). In spite of high month-to-month variation, interannually consistent seasonal trends appeared, with significantly lower δ¹³C (<?28.2‰) in spring than in the other seasons. In contrast, δ¹⁵N did not exhibit significant temporal variation. In spring and summer, high chlorophyll a and b concentrations were associated with low C/N values (<8) and a high percentage of organic carbon (%C) and organic nitrogen (%N), testifying to high development of autochthonous riverine phytoplankton (mainly diatoms and chlorophytes). In fall and winter, higher δ¹³C (>?27.2‰) and C/N (>8) values, and lower %C, %N, and chlorophylls concentrations indicated the predominance of allochthonous terrestrial detritus material in the river POM. The lower δ¹³C values recorded in spring–summer, when the phytoplankton biomass was high, were related to the lower carbon isotopic signatures of freshwater diatoms and chlorophytes compared to those of terrestrial plants. Overall, Rhone River POM was mainly composed of terrestrially derived material (90%), with autochthonous phytoplankton representing only 10% as a mean, in spite of a higher mean contribution of phytoplankton (27%) to river POM in summer.     

Correction to: Assessment of Polygala paniculata (Polygalaceae) characteristics for evolutionary studies of legume–rhizobia symbiosis

Journal of Plant Research - A correction to this paper has been published: https://doi.org/10.1007/s10265-021-01295-3     

Trend in aliens species in the Mediterranean. An answer to Galil, 2009 «Taking stock: inventory of alien species in the Mediterranean Sea»

The number of marine alien species reported in Galil (Biol Invasions, 2009) is incomplete. Recent literature suggests that the number of aliens is nearly 1,000 and that the introduction rate is way off the 10 species per year suggested by Galil (Biol Invasions, 2009).     

Epidemiological features of the first Unusual Mortality Event linked to cetacean morbillivirus in the South Atlantic (Brazil, 2017–2018)

Since the 1980s, cetacean morbillivirus (CeMV) has caused mass mortality events worldwide. However, no epizootics had been recorded in the South Atlantic, until an unusual mortality event (UME) linked to Guiana dolphin cetacean morbillivirus (GD-CeMV) began in Ilha Grande Bay, southeastern Brazil, in November 2017. In a five-month period, the UME spread to neighboring Sepetiba Bay and accounted for the death of at least 277 Guiana dolphins (Sotalia guianensis). Prevalence of morbillivirus positive dolphins, as estimated from RT-PCR diagnostics, was 92.3% (24/26) in Ilha Grande Bay and 91.9% (57/62) in Sepetiba Bay. Females had higher mortality rates during the UME (1.5:1), in contrast with historical mortality data from both bays that showed a 2:1 male to female death ratio. Calf mortality rates also increased in both bays. These results suggest that females and calves were more vulnerable to morbilliviral infection. Herein, we discuss possible explanations for such sex-biased death pattern during the UME and their implication for the conservation of endangered Guiana dolphins. We also speculate about the origin and spread of morbillivirus in the South Atlantic Ocean.     

Reproductive traits of marine terns (Sternidae): evidence for food limitation in the tropics?

Marine terns breed between 80°N and 70°S, making them a suitable group for examining links between latitude and reproductive traits. We investigated such traits for 34 taxa in seven genera, using analyses of residuals to correct for effects of e.g. female body mass and egg mass on other life history traits. Both tree- and K-means clustering, based on four traits excluding chick provisioning mode, identified two groups of terns—those that breed on tropical oceanic islands and those that breed along mainland coasts and at temperate islands (>40° from the Equator). Among mainland terns, there is a tendency for reduced clutch investment at low latitudes both between and within species. There is no interspecific latitudinal variation in incubation or fledging period of these terns, but intraspecific variation in fledging period (longer in the tropics) has been reported for one species. Tropical island terns, which mostly breed at sites lacking native ground predators, show extreme clutch reduction and lay a single, relatively large egg that has a long incubation period. Fledging periods are also long, despite the fact that these are the only terns to use multiple prey loading or regurgitation to feed their chicks. These patterns are interpreted as responses to low food availability stemming from a combination of low oceanic productivity, high bird densities because of breeding space limitation and localised prey depletion associated with central place foraging.     

On the occurrence of the fireworm Eurythoe?complanata complex (Annelida,Amphinomidae) in the Mediterranean Sea with an updated revision of the alien Mediterranean amphinomids

The presence of two species within the Eurythoe complanata complex in the Mediterranean Sea is reported, as well as their geographical distributions. One species, Eurythoe laevisetis, occurs in the eastern and central Mediterranean, likely constituting the first historical introduction to the Mediterranean Sea and the other, Eurythoe complanata, in both eastern and Levantine basins. Brief notes on their taxonomy are also provided and their potential pathways for introduction to the Mediterranean are discussed. A simplified key to the Mediterranean amphinomid genera and species of Eurythoe and Linopherus is presented plus an updated revision of the alien amphinomid species reported previously from the Mediterranean Sea. A total of five exotic species have been included; information on their location, habitat, date of introduction and other relevant features is also provided.     

Offshore Evidence for an Undocumented Tsunami Event in the ‘Low Risk’ Gulf of Aqaba-Eilat,Northern Red Sea

Although the Gulf of Aqaba-Eilat is located in the tectonically active northern Red Sea, it has been described as low-risk with regard to tsunami activity because there are no modern records of damaging tsunami events and only one tsunami (1068 AD) referred to in historical records. However, this assessment may be poorly informed given that the area was formed by and is located along the seismically active Dead Sea Fault, its population is known to fluctuate in size and literacy in part due to its harsh hyper-arid climate, and there is a dearth of field studies addressing the presence or absence of tsunamigenic deposits. Here we show evidence from two offshore cores for a major paleotsunami that occurred ~2300 years ago with a sedimentological footprint that far exceeds the scarce markers of the historically mentioned 1068 AD event. The interpretation is based on the presence of a laterally continuous and synchronous, anomalous sedimentological deposit that includes allochtonous inclusions and unique structural characteristics. Based on sedimentological parameters, these deposits could not be accounted for by other transport events, or other known background sedimentological processes.     

Correction to: Preliminary insights of a mixed‑species shark aggregation: a case study of two carcharhinids from the Mediterranean Sea

Environmental Biology of Fishes -     

What are the potential drivers of blooms of the toxic dinoflagellate Karenia selliformis? A 10-year study in the Gulf of Gabes,Tunisia, southwestern Mediterranean Sea

We report on a 10-year study of the dynamics of toxic dinoflagellate Karenia selliformis at 20 stations along the nearshore of the Gulf of Gabes (Tunisia) in relation to environmental variables. Dinoflagellates and K. selliformis have dominated the phytoplankton community and K. selliformis blooms have taken place since 2001. Phytoplankton groups showed significant variability among sampling sites, but did not vary significantly from year to year. Redundancy analysis revealed that salinity, nitrate and phosphorus significantly explained the variability of the main phytoplanktonic groups namely, diatoms, dinoflagellates, cyanobacteria and euglenoids, while K. selliformis exhibited a specific pattern. Because of the wide variability in K. selliformis abundance, we tested the influence of environmental variables on its presence/absence using a generalized linear mixed-effect model (GLMM). K. selliformis occurrence had a positive relationship with nitrate and a negative one with total phosphorus. The different spatial gradients of these two chemical variables led to spatial differences in K. selliformis development prevalent near touristic areas. Temperature was also retained in the GLMM and since it rose over the 10 years of the study, it likely supports the expansion of K. selliformis. The discrepancies between model predictions and observed occurrences suggest that consideration of other sources of environmental forcing may improve our understanding of the determinism of K. selliformis dynamics. Our study may be useful in the management of this ecosystem so as to plan for the best disposal options in the treatment of urban and industrial wastes in the gulf's coastal waters.