scholarly journals Biological condition and trophic ecology of the deep-water shrimp Aristaeomorpha foliacea in the Levantine Sea (SW Turkey)

2014 ◽  
Vol 16 (1) ◽  
pp. 103 ◽  
Author(s):  
K. Y. BAYHAN ◽  
J. E. CARTES ◽  
E. FANELLI
Keyword(s):  
Deep Water ◽  
Trophic Ecology ◽  
Water Mass ◽  
Isotope Composition ◽  
Eastern Mediterranean ◽  
Reproductive Period ◽  
Reproductive Capacity ◽  
Levantine Sea ◽  
Deep Water Species ◽  
Aristaeomorpha Foliacea

The trophic ecology (diets, stable isotope composition) and life cycle (gonado-somatic, GSI, and hepato-somatic, HSI, indices) of Aristaeomorpha foliacea were analysed seasonally (in May, June, and November 2012 and January 2013) off southeast Turkey (Levantine Basin), over the slope at 442-600 m depth. A. foliacea females were mature in June, suggesting gonad maturity was somewhat delayed off southeast Turkey compared to other areas in the Eastern Mediterranean. The HSI of A. foliacea was highest in May and June (8.2% of body weight) for males and both immature and mature females, sharply lower in November (3.5%) and then increasing again in winter (7.1%). Stomach fullness (F) showed a tendency similar to HSI in both females and males, increasing from May to June. A. foliacea had rather low d15N (6.68‰ to 8.26‰) off southeast Turkey, with females having higher d15N with increasing size. The δ13C signal (-14.85 to -14.68‰) indicated that diet was mainly though not exclusively based on zooplankton (pelagic shrimps and small myctophids of 1.3-4.5 mm TL, cnidarians, hyperiids and pteropods). The increase of A. foliacea remains in A. foliacea guts and of some benthic prey (polychaetes, bivalves, gastropods) after the reproductive period would explain the moderate depletion of δ13C in spring-summer. The greatest changes in the diet occurred between periods of water mass stratification (June and November) and periods of water mass homogeneity (May and January), with greater consumption of zooplankton in the latter season. A. foliacea seems to have lower reproductive capacity (GSI 5.6%) than other deep-water species of penaeidae that live shallower (Parapenaues longirostris) and deeper (Aristeus antennatus) than it does. The species has a more specialized zooplankton diet, exploiting short, more efficient trophic chains, which could be an advantage explaining its dominance in oligotrophic areas of the Central-Eastern Mediterranean, including the Turkish slope.

The Life History and Post Embryonic Development of the Copepods, Calanus tonsus Brady and Euchaeta japonica Marukawa

1934 ◽  
Vol 1 (1) ◽  
pp. 1-65 ◽  
Author(s):  
Mildred H. Campbell
Keyword(s):  
Life History ◽  
Deep Water ◽  
Reproductive Period ◽  
Spawning Period ◽  
Strait Of Georgia ◽  
Deep Water Species ◽  
One Year ◽  
Development Proceeds ◽  
Water Species ◽  
Reserve Food

Calanus tonsus Brady is an abundant, deep water species in the strait of Georgia. Development is characterized by a distinct metamorphosis and the six nauplius and six copepodid stages are described. The life cycle extends over one year and breeding occurs in the spring at the surface. The nauplii and early copepodid stages are soon replaced by stage V which dominates the plankton from May to December. C. tonsus exists as an adult for approximately two months—January and February. Maturity is accompanied by marked degeneration of the mouth parts in both sexes, death following shortly. The retrograde development appears associated with a change in habits. Stage V stores up reserve food, and the mature females with the disappearance of feeding devices depend upon this accumulated food during the reproductive period. Euchaeta japonica Marukawa occurs in limited numbers in the deep water of the strait of Georgia. It undergoes a similar metamorphosis to C. tonsus and the twelve stages are described. There is no definite spawning period but reproduction occurs throughout the year in deep water where development proceeds. Several broods may be produced by one female but the males are believed to die shortly after copulation. The nauplii differ from those of C. tonsus due to larger size, slight increase in length from stage I to stage VI and retarded development of the appendages. The conspicuous feature of the copepodid development is the extreme degeneration of the male mouth parts.

scholarly journals Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?

2014 ◽  
Vol 11 (1) ◽  
pp. 391-423 ◽  
Author(s):  
V. Cardin ◽  
G. Civitarese ◽  
D. Hainbucher ◽  
M. Bensi ◽  
A. Rubino
Keyword(s):  
Deep Water ◽  
Water Mass ◽  
Deep Layer ◽  
Eastern Mediterranean ◽  
Salt Content ◽  
Intermediate Water ◽  
Levantine Basin ◽  
Mass Properties ◽  
Wide Scale ◽  
East West

Abstract. We present temperature, salinity and oxygen data collected during the M84/3 and P414 cruises in April and June 2011 on a basin-wide scale to determine the ongoing oceanographic characteristics in the Eastern Mediterranean (EM). The east–west transect through the EM sampled during the M84/3 cruise together with data gained on previous cruises over the period 1987–2011 are analysed in terms of regional aspects of the evolution of water mass properties and heat and salt content variation. The present state of the EM basin is also evaluated in the context of the evolution of the Eastern Mediterranean Transient (EMT). From this analysis we can infer that the state of the basin is still far from achieving the pre-EMT conditions. Indeed, the 2011 oceanographic conditions of the deep layer of the central Ionian lie between the thermohaline characteristics of the EMT and the pre-EMT phase, indicating a possible slow return towards the latter. In addition, the thermohaline properties of the Adriatic Deep Water are still in line (warmer and saltier) as when it restarted to produce dense waters after the EMT. Special attention is given to the variability of thermohaline properties of the Levantine Intermediate Water and Adriatic Deep Water in three main areas: the Cretan, the central Levantine and the central Ionian Seas. Finally, this study evidences the relationships among the hydrological property distributions of the upper-layer in the Levantine basin and the circulation regime in the Ionian.

scholarly journals Aegean Sea Water Masses during the Early Stages of the Eastern Mediterranean Climatic Transient (1988–90)

2006 ◽  
Vol 36 (9) ◽  
pp. 1841-1859 ◽  
Author(s):  
I. Gertman ◽  
N. Pinardi ◽  
Y. Popov ◽  
A. Hecht
Keyword(s):  
Surface Water ◽  
Deep Water ◽  
Water Mass ◽  
Sea Water ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Water Masses ◽  
Intermediate Water ◽  
Central Basin ◽  
Cretan Sea

Abstract The Aegean water masses and circulation structure are studied via two large-scale surveys performed during the late winters of 1988 and 1990 by the R/V Yakov Gakkel of the former Soviet Union. The analysis of these data sheds light on the mechanisms of water mass formation in the Aegean Sea that triggered the outflow of Cretan Deep Water (CDW) from the Cretan Sea into the abyssal basins of the eastern Mediterranean Sea (the so-called Eastern Mediterranean Transient). It is found that the central Aegean Basin is the site of the formation of Aegean Intermediate Water, which slides southward and, depending on their density, renews either the intermediate or the deep water of the Cretan Sea. During the winter of 1988, the Cretan Sea waters were renewed mainly at intermediate levels, while during the winter of 1990 it was mainly the volume of CDW that increased. This Aegean water mass redistribution and formation process in 1990 differed from that in 1988 in two major aspects: (i) during the winter of 1990 the position of the front between the Black Sea Water and the Levantine Surface Water was displaced farther north than during the winter of 1988 and (ii) heavier waters were formed in 1990 as a result of enhanced lateral advection of salty Levantine Surface Water that enriched the intermediate waters with salt. In 1990 the 29.2 isopycnal rose to the surface of the central basin and a large volume of CDW filled the Cretan Basin. It is found that, already in 1988, the 29.2 isopycnal surface, which we assume is the lowest density of the CDW, was shallower than the Kassos Strait sill and thus CDW egressed into the Eastern Mediterranean.

scholarly journals Levantine Intermediate and Levantine Deep Water Formation: An Argo Float Study from 2001 to 2017

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1781 ◽  
Author(s):  
Elisabeth Kubin ◽  
Pierre-Marie Poulain ◽  
Elena Mauri ◽  
Milena Menna ◽  
Giulio Notarstefano
Keyword(s):  
Deep Water ◽  
Eastern Mediterranean ◽  
Potential Temperature ◽  
Sea Surface ◽  
Intermediate Water ◽  
Deep Water Formation ◽  
Argo Float ◽  
Levantine Sea ◽  
Water Formation ◽  
The Mediterranean

Levantine intermediate water (LIW) is formed in the Levantine Sea (Eastern Mediterranean) and spreads throughout the Mediterranean at intermediate depths, following the general circulation. The LIW, characterized by high salinity and relatively high temperatures, is one of the main contributors of the Mediterranean Overturning Circulation and influences the mechanisms of deep water formation in the Western and Eastern Mediterranean sub-basins. In this study, the LIW and Levantine deep water (LDW) formation processes are investigated using Argo float data from 2001 to 2017 in the Northwestern Levantine Sea (NWLS), the larger area around Rhodes Gyre (RG). To find pronounced events of LIW and LDW formation, more than 800 Argo profiles were analyzed visually. Events of LIW and LDW formation captured by the Argo float data are compared to buoyancy, heat and freshwater fluxes, sea surface height (SSH), and sea surface temperature (SST). All pronounced events (with a mixed layer depth (MLD) deeper than 250 m) of dense water formation were characterized by low surface temperatures and strongly negative SSH. The formation of intermediate water with typical LIW characteristics (potential temperature > 15 °C, salinity > 39 psu) occurred mainly along the Northern coastline, while LDW formation (13.7 °C < potential temperature < 14.5 °C, 38.8 psu < salinity < 38.9 psu) occurred during strong convection events within temporary and strongly depressed mesoscale eddies in the center of RG. This study reveals and confirms the important contribution of boundary currents in ventilating the interior ocean and therefore underlines the need to rethink the drivers and contributors of the thermohaline circulation of the Mediterranean Sea.

scholarly journals Post-eastern Mediterranean Transient Oxygen Decline in the Deep Waters of the Southeast Mediterranean Sea Supports Weakening of Ventilation Rates

2021 ◽  
Vol 7 ◽  
Author(s):  
Guy Sisma-Ventura ◽  
Nurit Kress ◽  
Jacob Silverman ◽  
Yaron Gertner ◽  
Tal Ozer ◽  
...  
Keyword(s):  
Deep Water ◽  
Water Mass ◽  
Eastern Mediterranean ◽  
Mean Value ◽  
Oxygen Levels ◽  
Dissolved Inorganic Nutrients ◽  
Deep Waters ◽  
Long Term Trends ◽  
Ventilation Rates

Long-term trends in oxygen, salinity, and nutrients were followed in the Southeastern Mediterranean (SEMS) deep waters from 2002 to 2020. Results show a net decrease in oxygen since 2008 of −0.5 ± 0.1 μmol kg−1 yr−1 in the bathypelagic depths (1,200–2,000 m). Multiannual variability in oxygen levels superimposed this trend, and is likely associated with variations in thermohaline fluxes. The 2020 mean oxygen concentration of 179.5 ± 2.3 μmol kg−1 is comparable to the pre-Eastern Mediterranean Transient (EMT) mean value. The post-EMT signature is clearly demonstrated in both oxygen and salinity over the period of 2002–2013, but since 2014 it diminished, mainly due to mixing of the Aegean deep water (AegDW) mass with the overlying old Adriatic water mass. This trend reflects a switch back to the pre-EMT regime, characterized by thermohaline homogeneity of the deep water column in the SEMS. The long-term decline of deep water oxygen levels is also accompanied by a corresponding increase in dissolved inorganic nutrients, supporting aging of the deep water masses. Our results suggest that ventilation of the SEMS deep water is currently occurring at a lower, pre-EMT rate, probably as a result of moderated deep water formation in recent time.

Bougainvillia aberrans (Cnidaria, Hydrozoa), a new species of hydroid and medusa from the upper bathyal zone off Bermuda

1993 ◽  
Vol 71 (5) ◽  
pp. 997-1002 ◽  
Author(s):  
Dale R. Calder
Keyword(s):  
New Species ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
Deep Water ◽  
North Atlantic Ocean ◽  
Deep Water Species ◽  
A New Species ◽  
Water Species

Bougainvillia aberrans n.sp. is described from Bermuda in the western North Atlantic Ocean. Specimens were collected at a depth of 150 fathoms (274 m) from the polypropylene buoy line of a crab trap. The hydroid colony of B. aberrans is erect, with a polysiphonic hydrocaulus, a smooth to somewhat wrinkled perisarc, hydranths having a maximum of about 16 tentacles, and medusa buds arising only from hydranth pedicels. Medusae liberated in the laboratory from these hydroids differ from all other known species of the genus in having a long, spindle-shaped manubrium, lacking oral tentacles, having marginal tentacles reduced to mere stubs, and being very short-lived (surviving for a few hours at most). Gonads develop in medusa buds while they are still attached to the hydroids, and gametes are shed either prior to liberation of the medusae or shortly thereafter. The eggs are surrounded by an envelope bearing nematocysts (heterotrichous microbasic euryteles). The cnidome of both hydroid and medusa stages consists of desmonemes and heterotrichous microbasic euryteles. The diagnosis of the genus Bougainvillia is modified to accommodate this new deep-water species.

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