The Ecology of Amorphous Aggregations (Marine Snow) in the Northern Adriatic Sea:

Abstract. In the water-column of the Gulf of Trieste (Northern Adriatic Sea) flocculent, amorphous aggregates known as marine snow reach maximum density and dimensions up to 20cm in diameter during summer months. Sampling of these fragile macro-aggregates was carried out by SCUBA-divers.
A large detrital component was found to be embedded in an organic matrix together with a large array of intact phytoplankton species. Heterotrophic bacterial density ranged from 2–65 × 10⁸ cells-g^-1 (marine snow dry wt) and is therefore of the same order of magnitude as in the surface layer of the sediments of the Gulf. In terms of biomass, bacteria reached only 30–95% of heterotrophic microflagellates.
A mean abundance of marine snow of 5g (marine snow dry wt) m^-3 was obtained for the water-column above the pyenolinc. At this boundary layer, however, a mean abundance of about 10g (marine snow dry wt) m^-3 led to the formation of a distinct, 10-50cm thick layer. Based on these data and sedimentation rates of marine snow to the pyenoclinc (38 g [marine snow dry wt] m^-2 d^-1) the potential ecological significance of these macro-aggregates for the pelagic system of the Gulf of Trieste is discussed.     

Diel vertical migration of medusae in the open Southern Adriatic Sea over a short time period (July 2003)

Diel vertical migration (DVM) of medusae was investigated at a fixed station in the oligotrophic Southern Adriatic Sea at several depths during summer (July) 2003. We hypothesized that medusan DVM is considerably influenced by environmental variables such as hydrographic features, light intensities, and potential prey densities. We used short-term repetitive sampling as an approach to detail these relationships. Of the 26 species collected, the highest abundance was in the layer between the thermocline (15 m) and 100 m depth, where Rhopalonema velatum predominated, reaching the maximum count of 93 individuals per 10 m³. Seven species were observed over a wide depth range: Solmissus albescens (15–1200 m), R. velatum (0–800 m), Persa incolorata (50–1200 m), Octophialucium funerarium (200–1200 m), Arctapodema australis (200–1200 m), Amphinema rubra (100–800 m), and Rhabdoon singulare (15–600). According to the medusan weighted mean depth (WMD) calculations, the longest DVMs were noted for the deep-sea species S. albescens , O. funerarium , and A. australis . The shallowest species, Aglaura hemistoma , was primarily non-migratory. Certain medusan assemblages were associated consistently with a particular depth layer characterized by a particular light intensity. The interplay of environmental factors and trophic relationships explains some of the features of medusan migratory patterns. These findings thus contribute to understanding the variables that determine patterns of medusan vertical migratory behavior.     

An Analysis of the Coastal Fish Assemblage of the Ustica Island Marine Reserve (Mediterranean Sea)

A study of the coastal fish assemblages in the marine park of Ustica Island (Southern Tyrrhenian Sea, Mediterranean) was conducted from June 1994 to September 1995 and from June 1996 to September 1997. The principal aims of the research were to: (1) define the faunistic features of local fish communities; (2) assess the effectiveness of the protection regime of the marine park on the fish assemblages ('reserve effect'); (3) provide information on the distribution of some Epinephelus and Diplodus species in the shallowest depth zone of the island. During seasonal surveys, underwater visual censuses were carried out at several sites located in three zones of the island, each with a different level of protection. Observations were made along 250 m² transects at 3–5, 10–15 and 25–30 m depth ranges. Additional surveys were made by SCUBA diving and snorkelling. A statistically significant effect of depth on the fish community parameters was observed, whereas differences linked to protection level, zones, sites and seasons were not significant. The abundance and frequency of occurrence of some species, particularly dusky grouper Epinephelus marginatus , were positively correlated with the degree of protection of the different zones of the marine park. Certain sites of the island are important as nursery areas for three species of the genus Diplodus ( i.e., D. puntazzo, D. sargus and D. vulgaris ).     

Tintinnids (Ciliophora) and Other Net Microzooplankton (> 30 µm) in Southwestern Atlantic Shelf Break Waters

Abstract. Proportions of foraminifers, tintinnids, polycystine radiolarians, pteropods and crustacean larval stages were estimated in a collection of 76 vertically stratified (0 – 100 m) 30 µm net microplankton samples from 16 stations along the Argentine shelf-slope (around 200 m isobath – between 40 and 56° S), covered on 13 – 18 November 1996. Tintinnids were identified to species. Relative abundances of the microzooplankton assessed and chlorophyll a values allow to define two contrasting groups of stations: 'deep' and 'shallow'. The former, located in pelagic, purely subantarctic Malvinas Current waters, hosted higher proportions of foraminifers and lower proportions of tintinnids, as well as less chlorophyll a (all differences were significant at the 0.1 % level). 'Shallow' stations were located in the area of the thermohaline front where the Patagonian Current comes in contact with the Malvinas Current, and were generally characterized by higher chlorophyll a levels (up to 3.7 µg Chl a  · l^–1). The distribution of tintinnid species, on the other hand, allowed no discrimination between these two areas, although some of the dominant forms showed much higher relative abundances in one of the two groups of stations. Twenty-six tintinnid taxa were recorded, yet only 6 accounted for 95 % of the specimens identified. Tintinnid taxocoenoses were characterized by a few abundant species and many rare ones. Numbers of tintinnid species and specific diversity did not differ noticeably with depth and latitude. Cape Horn Current waters were detected in the area by the presence of expatriated organisms presumably originating at mid-latitudes in the South Pacific Ocean.     

Fungal Invasion of Massive Corals

Abstract. Five species of corals from the Andaman Islands in the Bay of Bengal (Indian Ocean) have been regularly found to have single or multiple necrotic patches. The occurrence of such corals with necrotic patches varied from 10–50% in the field. Sections revealed a septate dark brown mycelial fungus on the surface and subsurface of the dead patches in five coral species. The fungus was isolated in culture and identified as Scolecobasidium sp.
The fungus formed a distinct dense brown to black zone of 0.5-1.5 cm width immediately below the surface of the corals. In terms of biomass, the fungus was estimated to contribute 3–5 mg cm ^-3 of coral skeleton.     

Effects of eelgrass (Zostera marina) canopy removal and sediment addition on sediment characteristics and benthic communities in the Northern Baltic Sea

The eelgrass Zostera marina is a key structural and functional species across the European coastline. The separate and interactive effects of eelgrass canopy removal and sediment addition on the sediment characteristics and the structure of benthic communities were studied in a factorial field experiment in the Northern Baltic Sea in July–August 2006. The removal of eelgrass canopy temporarily increased the sediment oxygen consumption, reduced the content of fine particles (<100 μm) and organic matter in the sediment, and increased the share of sand fraction (250–500 μm). Sediment addition increased the content of fine particles (<100 μm) and reduced the share of sand fraction (250–1000 μm). The effects were strongest in the presence of eelgrass canopy. Benthic invertebrates and macroalgae were affected by eelgrass canopy removal but not by sediment addition. The removal of eelgrass canopy significantly decreased benthic species richness and invertebrate and macroalgal densities. To conclude, our experiment demonstrates that Z. marina defines the patterns of benthic macroalgae and invertebrates but has moderate effects on sediment structure and metabolism in the Northern Baltic Sea.     

Ontogenetic and gender-modulated behavioural rhythms in the deep-water decapods Liocarcinus depurator (Brachyura: Portunidae), Munida tenuimana and Munida intermedia (Anomura: Galatheidae)

The regulation and expression of biological rhythms with respect to sex and ontogeny in deep-water benthic decapod crustaceans constitutes an exciting field in marine biology that is far from understood. Liocarcinus depurator , Munida intermedia and Munida tenuimana are ecologically key crustacean decapod species of the Atlantic and Mediterranean shelves and slopes, and their activity rhythms in the field are poorly known. Our aim was to measure the behavioural rhythms of these species, while at the same time defining their type of displacement ( i.e. endobenthic, nektobenthic or benthopelagic). Whether gender and ontogeny modulate the rhythmic behaviour of these decapods is unknown, and we sought to clarify this issue. A temporally scheduled series of trawl hauls and light intensity measures was performed on the western Mediterranean shelf (100–110 m depth) and slope (400–430 m), close to the autumn equinox and the summer solstice. The sex and the size of animals in the catches were analysed. Catch patterns were evaluated through waveform and periodogram analyses. Liocarcinus depurator was captured at night on the shelf, whereas on the slope, animals displayed peaks both in the middle of the day and night. Size-related differences (but no gender differences) were found in its rhythmic behaviour, possibly due to intra-specific competition ( e.g. fighting) between juveniles and adults. Munida intermedia were weakly diurnal in October and both diurnal and nocturnal in June. Munida tenuimana presented no discernible rhythmicity in October, but was nocturnal in June. Both species showed no evident sex or size modulation of their behaviour. Data were interpreted assuming that all tested species present an endobenthic behaviour ( i.e. animals emerge from the substrate during the active phase of their behavioural cycle).     

Circannual Cycle and Oxygen Consumption in Eudendrium glomeratum (Cnidaria, Anthomedusae): Studies on a Shallow Water Population

Abstract. The oxygen consumption of Eudendrium glomeratum was measured monthly, throughout the period of active presence of the species in the field, to obtain indications on its physiological condition in the different phases of the cycle. Sets of one hundred polyps were assayed in the laboratory under normothermic (according to field temperature: 14–19°C) and hyperthermic conditions (22–25°C). The different response to identical temperatures at the extremes of the cycle, together with a differential ability to face stressful conditions in the same periods, suggests that other factors, besides temperature, regulate the seasonal cycle of Eudendrium glomeratum.     

Biology of three Malacostraca (Decapoda) in a Mediterranean lagoon with particular emphasis on the effect of rapid environmental changes on the activity (catchability) of the species

The activity of three Malacostraca (Decapoda), Crangon crangon, Carcinus aestuarii and Paleamon squilla, was studied following rapid environmental changes in a Mediterranean lagoon linked temporarily with the sea. Nekton was sampled every 2–3 days using fixed fyke nets. A canonical analysis and a stepwise multiple regression were computed to determine which factor(s) can predict or account for the catch of these three decapods. In spite of rapid environmental changes no exceptional mortality was observed in each of the three species. Temperature is the environmental factor with major impact on the activity of C. crangon. Activity of P. squilla is controlled by water depth. At a depth of less than 20 cm two factors, salinity and phase of the moon, have a significant influence on the activity of this species. At depths deeper than 20 cm the activity is inhibited. There is only a weak relationship between the catch of C. aestuarii and salinity. Additional data on the life cycle of these species are given. The limitations of a monthly sampling period are discussed and the need for more short-term, consecutive sampling periods is stressed in order to understand the dynamics of systems with rapid environmental fluctuations.     

Fecundity in the marine spiny lobster Jasus verreauxi (H. Milne Edwards) (Crustacea: Decapoda: Palinuridae)

Fecundity in Jasus verreauxi (H. Milne Edwards, 1851) has been studied by a detailed investigation of (a) the total weight of eggs carried by female specimens, (b) the average number of eggs per 1 g sample, and (c) the total number of eggs carried by females. In mid October 1966, 217 females “in berry” (that is, carrying external eggs) were examined and measured at Spirits Bay, New Zealand. The fecundity study is based on the results obtained from 21 selected specimens, with carapace lengths from 15.5 cm to 23.5 cm.

A direct relation was found between the total weight of eggs carried and increase in carapace length. The total weight of eggs carried varied from about 51 g to 238 g for carapace lengths of 15.5 cm to 23.5 cm. No correlation was shown between the average number of eggs per 1 g sample and increase in carapace length. Considerable variation was noted in the number of eggs per 1 g sample, which ranged from a low count of 6,453 eggs to a high count of 8,341 eggs. The total number of eggs carried by female J. verreauxi was found to be related to an increase in carapace length. Furthermore, increase in fecundity per relative carapace length increase was noted to be greater in smaller specimens than in larger specimens. The total number of eggs carried ranged from about 385,000 for a carapace length of 15.5 cm to 1,940,000 for a carapace length of 23.5 cm.

Fecundity, as measured by the total weight of eggs carried and the total number of eggs produced, was found to be much higher in J. verreauxi than in several Jasus species previously studied by other workers.     

Shallow-Water Gasohydrothermal Vents of Ushishir Volcano and the Ecosystem of Kraternaya Bight (The Kurile Islands)

Abstract. A marine ecosystem in the crater of the Ushishir Volcano (Kraternaya Bight, Yankich Island, the Kuriles) showing gasothcrmal activity was studied for hydrographical, hydrochemical, and biological characteristics. Maximal changes in chemical and biological characteristics were observed in the surface water layer of 0–5 m. This layer had higher water temperature, was saturated with volcanogcnic carbon dioxide (up to 2000 10^-6 torr), ovcrsaturatcd with oxygen (up to 200 %), and contained high concentrations of chlorophyll a. Hydrogen sulfide was found in the surface water layer and at a depth of 15 m in the area of maximal effect of volcanic effluents.
The planktonic community is characterized by high rates of production and destruction of organic matter only in the 0–5 m layer. Daily vertical migrations of the ciliatc Mesodinium rubrum were observed, which caused "red tides".
Bacterial, algobacterial, and diatom mats developed on the bottom of the bight in the zone of gasohydrothermal vents and in areas of volcanic water seeping. The rate of organic matter production in algobacterial mats reached 33.4g C-rrr²-d^-l, chcmolithotrophy predominating. Bottom settlements had high population density and great animal biomass, which reached 10 kg m^-2 in gasohydrothermal fields. They obtain sufficient energy from primary production of microphy-tobenthos, algobacterial, and bacterial mats. Bcnthic species dominant in the bight were not found off the Ushishir Islands.
Some species of macrobenthos inhabiting the Kraternaya Bight differ markedly in size and biomass from the same species found beyond the bight.     

A Comparison of Phytoplankton Biomass Estimators and Their Environmental Correlates in the Mali Ston Bay (Southern Adriatic)

Abstract. Phytoplankton biomass estimators – total cell number (CN), total cell volume (CV), chlorophyll a (Chl a ). phytoplankton organic carbon (PC), and their response to environmental variables, with a special emphasis on the vertical variability in the structure of the water column – were examined in the Mali Ston Bay (Southern Adriatic). Correlations among biomass estimators as well as with physical-chemical parameters varied according to hydrodynamic characteristics of the water column. The amount of Chl a per cell ranged from 0.28.06–10^-6μg during stratification to 0.7–2.0.10^-6μg during the mixing period. Most frequent values for PC/Chl a ratios and for Chl a /CV in mixed natural phytoplankton populations were 20–25 and 1–2, respectively.     

The Sponge Population of the Cabrera Archipelago (Balearic Islands): Characteristics, Distribution, and Abundance of the Most Representative Species

Abstract. The abundance, distribution, and species richness of the littoral sponges (0–55 m) from the Cabrera Archipelago (Balearic Islands) were studied along light gradients from the surface to the sea bottom and from cave mouths to their inner parts. A total of 98 species (11 Calcarea and 87 Demospongiae ) were recorded, 8 of which are new records for the Spanish coast.
Cluster and correspondence analyses enabled the identification of a sciophilous sponge group including three subgroups: sponges found only in semi-dark cave habitats, a subgroup common to the coralligenous, precoralligenous, and semi-dark cave biocoenoses, and a third subgroup exclusive to the coralligenous biocoenosis. A small number of photophilic species and other species having a wide bathymetric distribution made up another separate group. No species clusters for the different semi-sciophilous (either fleshy or carbonate) or photophilic seaweed communities were discernible. The number of sponge species was negatively correlated with the irradiance level.     

Description of the Phytoplanktonic Community of the Oligotrophic Waters of the SE Aegean Sea (Mediterranean)

Abstract. A seasonal sampling program of five stations off the Island of Rhodes (SE Aegean Sea) was carried out in 1983–1984. Temperature, salinity, Secchi disk transparency, P-PO₄, N-NO₃, N-NO₂, N-NH₃, Si-SiO₂, and chl a were measured and phytoplankton species recorded. Cell concentrations and chl a varied seasonally. with the highest values in summer (l.2 times 10⁴ -1^--¹ total mean cells; 0.13 mgam^-3 total mean chl a ) and the lowest in winter (2.3 times 10³, 1^--¹ total mean cells; 0.06 mg^.m-^- total mean chl a ). A variation in cell abundance among stations was also noted. Quantitative relationships among the recorded taxa showed that diatoms and dinoflagellates were richer in species composition (88 and 58 total species, respectively) than coccolithophores (8 species) and other flagellates (8 species). Comparison of phytoplankton samples from different depths and stations by cluster analysis showed an irregularity or discontinuity in species associations. The SE Aegean Sea was characterized as oligotrophic on the basis of the estimated nutrient and phytoplankton concentration levels.     

Relationships Between Community Structure of the Intertidal Macroinfauna and Sandy Beach Characteristics Along the Chilean Coast

Abstract. Eight sandy beaches were seasonally sampled along the coast of Chile, from ca. 21 to 42° S (about 3000 km) to study the relationship between community structure of the intertidal macroinfauna and beach characteristics. Sediment samples (0.1 m², 30 cm deep) were collected (July – September 1998 and December 1998 – January 1999) with plastic cylinders at 15 equally spaced levels along three replicated transects extending from above the drift line to the swash zone. The sediment was sieved through a 1 mm mesh and the organisms collected stored in 5 % formalin. To define beach types, Dean's parameter (Ω) was calculated from wave heights and periods, and fall velocity of sand particles from the swash zone. Crustaceans (mainly peracarids) were the most diverse group with 14 species, followed by polychaetes with 5 species. The talitrid amphipod Orchestoidea tuberculata , the cirolanid isopods Excirolana braziliensis and E. hirsuticauda and the anomuran decapod Emerita analoga were the most widely distributed and common species. Regression analyses between species richness, abundance and biomass of the whole macroinfauna versus sediment characteristics, beach face slopes and morphodynamic beach states showed no significant relationships. Thus, macroinfaunal community characteristics did not increase linearly from lower intermediate to higher intermediate or dissipative beach states as had been found before in Chile or in other coasts. A comparative analysis with data from sandy beaches of other world regions showed that the number of species inhabiting Chilean sandy beaches was generally lower, whereas total population abundances were generally higher compared with values reported elsewhere.     

Quantitative analysis of fish schooling behavior with different numbers of medaka (Oryzias latipes) and goldfish (Carassius auratus)

Fish form schools of various sizes, according to species or environmental conditions, to attain several advantages, such as protection from predators or to improve efficiency in searching for prey. Thus, quantifying the mechanisms of how group size affects schooling behavior may contribute to better understanding fish biology and the evolution of the collective behavior of fishes. In the present study, we explored how school size affected the behavior of medaka (Oryzias latipes) and goldfish (Carassius auratus). Size groups of 10 to 40 individuals were placed in a circular aquarium (100 cm diameter, 30 cm height, 5 cm water depth) and videoed for 4 hours. Eight to 10 video clips of 3 seconds in length for each group size were evaluated for 6 physical parameters of fish schooling behavior. Regardless of species, the mean distance among individuals increased with increasing school size. However, due to variations in certain physical parameters, the schooling pattern of goldfish was more elongated than medaka, possibly related to body size, or indicating species-specific differences in schooling characteristics. Our experimental datasets could be incorporated into theoretical mathematical models of fish schooling behavior, by contributing new information about school size and species differences.     

Community structure of bathyal decapod crustaceans off South-Eastern Sardinian deep-waters (Central-Western Mediterranean)

Community structure and faunal composition of bathyal decapod crustaceans off South-Eastern Sardinian deep-waters (Central-Western Mediterranean) were investigated. Samples were collected during 32 hauls between 793 and 1598 m in depth over the 2003–2007 period. A total of 1900 decapod specimens belonging to 23 species were collected. Multivariate analysis revealed the occurrence of three faunistic assemblages related to depth: (i) an upper slope community at depths of 793–1002 m; (ii) a middle slope community at depths of 1007–1212 m and (iii) a lower slope community at depths greater 1420 m. In the upper and middle slopes the benthic ( Polycheles typhlops ) and epibenthic–endobenthic feeders (mainly Aristeus antennatus and Geryon longipes ), which eat infaunal prey, were dominant, followed by the macroplankton–epibenthic feeders such as Acanthephyra eximia and Plesionika acanthonotus . In the deepest stratum, the most remarkable feature was the prevalence of macroplankton–epibenthic feeders ( A. eximia and P. acanthonotus ). A small percentage of the benthic deep-sea lobster Polycheles sculptus was also present. The biomass presented higher values in the middle slope and declined strongly in the lower slope. There was no general pattern of mean individual weight/size versus depth among decapods, and the changes seemed to be species-specific with different trends.     

Observations on the Spatio-Temporal Distribution of Crustacean Amphipods in the Fusaro Coastal Lagoon (Central Tyrrhenian Sea, Italy) and Some Notes on Their Presence in Mediterranean Lagoons

Abstract. The amphipod population of the Fusaro coastal lagoon (Tyrrhenian Sea, Italy) was studied on a spatial-temporal scale. During a one-year period, samples were collected on hard and soft bottoms along a transect from the inland to the seaward side of the lagoon. Thirteen species were identified. The dominant taxa included species typical of lagoon environments, such as Corophium insidiosum and Microdeutopus gryllotalpa , and species typical of marine environments yet also inhabiting sheltered or semi-closed areas, such as Corophium acutum, Ericthonius brasiliensis , and Elasmopus rapax.
An inner-outer gradient was not evident, while a seasonal pattern was recognizable. At the community level, clear differences between the two substrata were not evident because of high algal growth and organogenic detritus on the soft bottoms. The importance of hydrodynamic forces in a euhaline lagoon in selecting amphipod communities - characterized by a typical trophic behaviour and way of life – is discussed. Information on the ecology of the collected species and a list of Mediterranean lagoons where they are present are also provided.     

Abundance and biomass of meiobenthos in the spawning ground of anchovy (Engraulis japanicus) in the southern Huanghai Sea

1 Introduction Meiofauna is an important group in benthic small food web energetically due to their small size, high abundance and fast turnover rates. The production of meiofauna is equal to or higher than that of macrofau- na in estuaries, shallow waters and deep sea (Gerlach, 1971; Platt and Warwick, 1980; Heip et al., 1985; Zhang et al., 2004). A role of meiofauna may be the recycling of nutrients. Marine nematodes may keep the bacterial colonies on sand grains in active phase of growth …     

Comparison of benthic foraminifera inside and outside a sulphur-oxidizing bacterial mat from the present oxygen-minimum zone off Pakistan (NE Arabian Sea)

Assemblages of live (Rose-Bengal-stained) and dead benthic foraminifera and stable oxygen and carbon isotopic composition of live benthic foraminifera were studied in and outside a bacterial mat composed of the large sulphur-oxidizing bacteria Thioploca and Beggiatoa from the oxygen-minimum zone off Pakistan (NE Arabian Sea). Two cores from the same Multicorer retrieved a bacterial mat and ambient sediment. The dominant species (Globobulimina affinis, G. turgida, Bolivina pacifica, B. pseudopunctata, Uvigerina peregrina and Buliminella tenuata) in both cores are characteristic for dysoxic oxygen minimum zone conditions. The most significant difference between the two cores is the reduced number of stained benthic foraminifera (SBF) in the top 0.5 cm of the bacterial mat. Faunal densities of stained species are more than four times higher in the sediment surface sample (0–0.5 cm) outside the bacterial mat, at a distance of only 1.5 m. All stained species, however, observed outside the Beggiatoa/Thioploca mat were also observed in the core with the mat. Two species, Virgulinella fragilis and Bolivina dilatata, occur exclusively in the core with the bacterial mat. The diversity within the bacterial mat core is thus slightly higher than outside. Furthermore, the abundances of the species Buliminella morgani, B. tenuata and Alliatina primitiva are substantially higher in the bacterial mat than outside. Globobuliminids, on the other hand, seem to prefer the conditions outside the bacterial mat and are five times more frequent in the core taken outside the bacterial mat. Benthic foraminifers inhabit a broader microhabitat range outside the bacterial mat (∼5 cm) than within (3.5 cm). A marked decrease in SBF abundances was observed at the level of a black sulphur-rich layer which is interpreted to mark the shallow redox front below the bacterial mat. Stable carbon isotope analyses on live benthic foraminifera do not support a relation of the investigated Beggiatoa/Thioploca mat to a constant or seasonal seepage of methane at the continental slope off Pakistan. Surprisingly, however, stable oxygen isotope values of many species and especially of U. peregrina decrease with depth, which calls into question the suitability of U. peregrina as a recorder of bottom-water δ¹⁸O.