Recovery of the commercial sponges in the central and southeastern Aegean Sea (NE Mediterranean) after an outbreak of sponge disease

The distribution and biometry of commercial sponges (Porifera) in coastal areas of the central and southeastern Aegean Sea was investigated to estimate the recovery progress of the populations eight years after the first appearance of sponge disease. Signs of the disease were detected only in 1.6% of the harvested sponges. Multivariate analysis on the percentage abundance of sponges showed two distinct groups among the sixteen fishing grounds studied: the eight deep (50-110 m) and the eight shallow ones (<40 m). The group from the deep depths consisted of Spongia officinalis adriatica, S. agaricina and S. zimocca. The infralittoral zone was characterized by the presence of Hippospongia communis, S. officinalis adriatica and S. officinalis mollissima. These bath sponges showed an enhanced abundance in the eastern Cretan Sea (S. Aegean Sea). In addition, their dimensions, particularly height, increased with increasing depth. It is indicated that the hydrographic conditions prevailing in the eastern Cretan Sea affected the repopulating processes of sponge banks. In each species, the biometric characteristics of the experimental specimens were similar to those of the sponges found in the market and harvested at respective depths prior to the appearance of sponge disease

Microplanktic assemblages (sarcodines and alveolates) in the central and southeastern Aegean Sea (NE Mediterranean)

Spatial changes in the structure of microplanktic assemblages (sarcodines and alveolates) in the surface waters of coastal regions in the central and southeastern Aegean Sea were estimated during late summer to early autumn. Tintinnidae (Ciliophora), as well, Acanthometridae (Radiolaria) and Globiderinidae (Foraminifera) exhibited a higher abundance in the central Aegean Sea, compared to that in the more oligotrophic southeastern area of the same sea. Multivariate analysis revealed that the samples from the eastern Cretan Sea (South Aegean Sea) were highly distinguished from all the others and showed the highest densities of polycystines (Radiolaria), specifically of the families Thalassicollidae, Thalassosphaeridae, Sphaerozoidae (Collodaria), as well as of Actinommidae (Spumellaria) and Theoperidae (Nassellaria). In addition, the families Ceratiaceae and Prorocentraceae (Dinoflagellata) were more abundant in the southeastern than in the central Aegean Sea. It is indicated that the hydrographic conditions prevailing in the eastern Cretan Sea affected the structure of the microplanktic community in the surface layer. It is proposed that the assemblage of the identified radiolarian families belonging to Collodaria, Spumellaria (S) and Nassellaria (N), with a high S/N ratio, could be used as biological proxy of weak upwelling systems in the warm stratified waters of the oligotrophic eastern Mediterranean

Beat length measurement in directional couplers by thermo-optic modulation

In integrated optical directional couplers formed by two parallel waveguides, we measure the difference Δβ = βeven - βodd between the propagation constants of the 'supermodes'. They are coupled locally by heating a fine spot on one of the guides. When the spot is scanned along the coupler the output power from one of the guides is found to vary periodically. The period of variation is the modal beat length λ = 2π/Δβ. We demonstrate this technique with directional couplers fabricated by K+-exchange in glass. Beat lengths in the range of 0.6 ... 2.2 mm are measured with an accuracy of ±0.3%.<br/

Bacterial Community Legacy Effects Following the Agia Zoni II Oil-Spill, Greece

In September 2017 the Agia Zoni II sank in the Saronic Gulf, Greece, releasing approximately 500 tonnes of heavy fuel oil, contaminating the Salamina and Athens coastlines. Effects of the spill, and remediation efforts, on sediment microbial communities were quantified over the following 7 months. Five days post-spill, the concentration of measured hydrocarbons within surface sediments of contaminated beaches was 1,093–3,773 μg g–1 dry sediment (91% alkanes and 9% polycyclic aromatic hydrocarbons), but measured hydrocarbons decreased rapidly after extensive clean-up operations. Bacterial genera known to contain oil-degrading species increased in abundance, including Alcanivorax, Cycloclasticus, Oleibacter, Oleiphilus, and Thalassolituus, and the species Marinobacter hydrocarbonoclasticus from approximately 0.02 to >32% (collectively) of the total bacterial community. Abundance of genera with known hydrocarbon-degraders then decreased 1 month after clean-up. However, a legacy effect was observed within the bacterial community, whereby Alcanivorax and Cycloclasticus persisted for several months after the oil spill in formerly contaminated sites. This study is the first to evaluate the effect of the Agia Zoni II oil-spill on microbial communities in an oligotrophic sea, where in situ oil-spill studies are rare. The results aid the advancement of post-spill monitoring models, which can predict the capability of environments to naturally attenuate oil

A deep learning approach to photo–identification demonstrates high performance on two dozen cetacean species

We thank the countless individuals who collected and/or processed the nearly 85,000 images used in this study and those who assisted, particularly those who sorted these images from the millions that did not end up in the catalogues. Additionally, we thank the other Kaggle competitors who helped develop the ideas, models and data used here, particularly those who released their datasets to the public. The graduate assistantship for Philip T. Patton was funded by the NOAA Fisheries QUEST Fellowship. This paper represents HIMB and SOEST contribution numbers 1932 and 11679, respectively. The technical support and advanced computing resources from University of Hawaii Information Technology Services—Cyberinfrastructure, funded in part by the National Science Foundation CC* awards # 2201428 and # 2232862 are gratefully acknowledged. Every photo–identification image was collected under permits according to relevant national guidelines, regulation and legislation.Peer reviewedPublisher PD

The effect of temperature, salinity and diet on final size of female Tisbe holothuriae (Copepoda, Harpacticoida)

Tisbe holothuriae was collected from the Saronices Gulf (Greece) and cultured in the laboratory at various conditions. Growth of females reared under 12 combinations of temperature (14-24°C) and salinity (26-44‰) and 7 different diets was evaluated. Adult female body length increased slightly with salinity and decreased greatly with temperature, with a maximum value (1.096 mm) at 14°C and 38‰. There were no apparent interactions between these factors. Length is related to temperature and salinity by the following equation, L = 1.39 + 0.025S - 0.0003S2 - 0.071T + 0.0009T2 + 0.00005ST. There were no significant differences in length of adult females as a result of testing 7 different diets. Significant differences in length were found between the instars on successive days of development, except between the 4th and 5th day, when nauplii were transformed to copepodites

Effects of light (photoperiod, spectral composition) on the population dynamics of Tisbe holothuriae Humes (Copepods, Harpacticoida)

The harpacticoid copepod Tisbe holothuriae Humes was reared for several generations under different photoperiods (white light) and spectral quality (continuous illumination). The main life cycle parameters were measured and demographic variables were determined. Development time was retarded under green wavelengths and at photoperiods different from LD 12:12, especially under continuous white light. Total body length of females and males was shortest under LD 12:12 and longest under constant dark. Photoperiods different from LD 12:12 prolonged the interval between broods of egg sacs. Short photoperiods caused higher abortion rate, while long photoperiods retarded the maturation time of the egg sacs. Red wavelengths stimulated the abortion rate. Photoperiod LD 12:12 and blue wavelengths increased the production of offspring and the life span of females. Highest intrinsic rates of natural increase were estimated under LD 12:12 (rm =0.304) and blue wavelengths (rm = 0.254). These light conditions proved the most favourable for rearing Tisbe holothuriae. © 1992 Kluwer Academic Publishers

Effects of light (photoperiod, spectral composition) on the population dynamics of Tisbe holothuriae Humes (Copepods, Harpacticoida)

The harpacticoid copepod Tisbe holothuriae Humes was reared for several generations under different photoperiods (white light) and spectral quality (continuous illumination). The main life cycle parameters were measured and demographic variables were determined. Development time was retarded under green wavelengths and at photoperiods different from LD 12:12, especially under continuous white light. Total body length of females and males was shortest under LD 12:12 and longest under constant dark. Photoperiods different from LD 12:12 prolonged the interval between broods of egg sacs. Short photoperiods caused higher abortion rate, while long photoperiods retarded the maturation time of the egg sacs. Red wavelengths stimulated the abortion rate. Photoperiod LD 12:12 and blue wavelengths increased the production of offspring and the life span of females. Highest intrinsic rates of natural increase were estimated under LD 12:12 (rm =0.304) and blue wavelengths (rm = 0.254). These light conditions proved the most favourable for rearing Tisbe holothuriae. © 1992 Kluwer Academic Publishers

Temperature, salinity and light induced variations on larval survival and sex ratio of Tisbe holothuriae Humes (Copepoda: Harpacticoida)

Tisbe holothuriae was collected from the Saronicos Gulf of Greece (38%.) and reared under laboratory conditions. The effects of temperature (14, 19, 24 °C), salinity (26, 32, 38, 44%., for each tested temperature), two modalities of light: photoperiod (LD 24:0, 18:6, 12:12, 6:18, 0:24 h), spectral composition (blue, green and red wavelengths) on mortality during larval development and sex ratio of adults were studied. Survival and proportion of females decrease as temperature declines from medium levels (19°C) and salinity from normal levels (38%.). The effects of low temperatures and salinities appear to be pronounced on both parameters studied. Multiple regression analysis proved the quadratic and linear effects of temperature to be more important factors affecting the time required for the death of 50% of the initial nauplii than those of salinity. The linear effect of salinity is a more important factor affecting the sex ratio than temperature. Continuous illumination and long-day photoperiod significantly reduce the larval survival and the proportion of females. Red and green wavelengths markedly increase the percentage mortality. Spectral composition seems not to influence sex ratio. © 1993

Effects of seven diets on the population dynamics of laboratory cultured Tisbe holothuriae Humes (Copepoda, Harpacticoida)

The harpacticoid copepod Tisbe holothuriae was collected from Saronicos Gulf (Greece) and reared under constant laboratory conditions. In order to study the effects of food on the population dynamics, seven diets were tested: the seaweed Ulva; five artificial compound feeds: the liquid Fryfood® (Waterlife), a powder of Mytilus, yeast, soya and Spirulina, respectively; and a mixed diet consisting of Ulva and Fryfood. The life cycle parameters (mortality, sex ratio, generation time, offspring production) were measured, and the demographic variables [mean generation time (T), net reproductive rate (Ro), and intrinsic rate of natural increase (rm)] were determined. As to their efficiency regarding population dynamics, the diets ranked as follows: (1)Ulva+Fryfood, (2), Ulva, (3) Fryfood, (4)Mytilus, (5) soya, (6) yeast, and (7)Spirulina. In this order they cause a progressive increase of both larval mortality and generation time, a progressive decrease of sex ratio, number of offspring per egg sac, number of egg sacs per female and, consequently, of Ro and rm. The observed differences between diets were most pronounced with respect to offspring production. Of the compound diets, those containing animal extracts were more efficient than those containing vegetable materials. Ulva plays an important role in the nutrition of T. holothuriae, favouring offspring production as well as larval survival, development and pigmentation. Ulva in combination with Fryfood led to a greater copepodid survival and offspring production. This mixed diet proved to be the most favourable for rearing the Greek population of t. holothuriae, resulting in an efficient intrinsic rate of natural increase (rm=0.304) of the population. © 1991 Biologische Anstalt Helgoland