Seawater Temperature Variations Research Articles

Seasonal variability of prooxidant pressure and antioxidant adaptation to symbiosis in the Mediterranean demosponge Petrosia ficiformis

In symbioses between invertebrates and microalgae, host tissues are exposed to increased levels of photosynthetically produced oxygen. The biochemical consequences of symbioses have been poorly investigated in Mediterranean species, but a general increase in antioxidant defences has been recently reported in the demosponge Petrosia ficiformis as an adaptive response to the cyanobacterium Aphanocapsa feldmanni. Since Mediterranean symbioses naturally experi- ence marked seasonal variations in symbiont content, light intensity and seawater temperature, the aim of this work was to investigate if these fluctuations modulate the prooxidant challenge to sponge tissues. Antioxidant efficiency was characterised on a monthly basis by combining an analysis of the main antioxidants (superoxide dismutase, catalase, glutathione S-transferases, glutathione reduc- tase, glutathione peroxidases) with measurements of the total oxyradical scavenging capacity (TOSC), thus achieving a more holistic assessment of the capacity of sponge tissues to absorb differ- ent forms of reactive oxygen species. Symbiotic sponges showed significant seasonal changes in antioxidant efficiency, with more marked variations in tissues directly exposed to photosynthetically produced reactive oxygen species. The greatest variations were observed during the summer months, with the highest seasonal values for some defences (i.e. catalase) and the lowest for others (i.e. glutathione peroxidases). The marked increase in catalase and TOSC in summer suggests greater production of H2O2 in the symbioses during this period, supporting the hypothesis that sea- water temperature can significantly modulate the prooxidant challenge in Mediterranean symbioses. The results suggest that species with lower antioxidant efficiency may be less tolerant of conditions effecting oxidative damage; e.g. increases in temperature during the summer months.

Coiling direction in <i>Globigerina bulloides</i> of Middle Miocene age

Abstract. Detailed analysis of the early evolutionary stage of Globigerina bulloides in Middle Miocene calcareous nannoplankton zones NN5 and NN6 shows no preference for sinistral or dextral coiling patterns despite seawater temperature variations (as inferred from stable isotope analyses of foraminifer shells). Accordingly, coiling direction was proportional or biased to sinistral.

Temporal Variations in the Second-Degree Stokes Tesseral Geopotential Coefficients from Topex/Poseidon Altimetry

The TOPEX/POSEIDON (T/P) altimetry data set covering the periodof January 1, 1993 to January 3, 2001 was used to derive monthlyseries of the second-degree tesseral geopotential coefficients.To account for the sea water temperature variations, rathersimple models have been devised and discussed, describinglocalized as well as areal variations of sea water temperatureand heights. The second-degree tesseral coefficients have alsobeen shown to be proportional to the pressureportions of the oceanic equatorial effective excitation functions,used in Ocean Angular Momentum (OAM) data. OAM datatogether with Atmospheric Angular Momentum (AAM) data canbe used to study observed polar motion (PM) series.The excess PM rates, derived from the T/P effective excitationfunctions, were compared to the corresponding observed PM rates,derived from the International Earth Rotation Service (IERS)Bulletin A and corrected with AAM also obtainedfrom IERS. The noise of the T/P derived PM rate series was foundto be significantly larger than the corresponding Bulletin A/AAMPM rate residuals as well as the PM rates derived from anindependent OAM series that was also available for the1993–2000 period.

Seasonal and interannual variation in fish assemblages of northern temperate rocky subtidal habitats

Fish assemblages on two inshore rocky subtidal sites on the west coast of Scotland, were studied using diver visual surveys on a monthly basis between September 1995 and December 1999. A total of 17 689 fishes and 26 species were recorded from the two sites, Saulmore Point (056°27′N; 005°24′W) near Oban and Davy's Rock (055°46′N; 004°53′W) on the Isle of Great Cumbrae. The gobiid Thorogobius eppiphiatus, dominated the Saulmore Point site; six fish species accounted for >93% of total abundance at that site. At Davy's Rock four species contributed at least 93% of total fish abundance, and the dominant species was the labrid Ctenolabrus rupestris. Total abundance of the dominant species displayed a clear seasonal trend, and this was significantly related to recorded daily average seawater temperature. A maximum abundance of 4.9 fishes m−2 was recorded in November 1998 at Davy's Rock and 2.5 fishes m−2 at Saulmore Point in October 1998. Multivariate analysis indicated a degree of variation in assemblage structure between winter and summer at both sites. A number of species showed some degree of interannual variation, in particular the gobiid Gobiusculus flavescens whose abundance increased by over 300 times over a 5 month period in 1998. Correlation analysis showed that variation in annual winter seawater temperature could act as an indicator of interannual variation in abundance of some of the dominant species utilizing rocky subtidal habitats.

Seasonal and interannual variation in fish assemblages of northern temperate rocky subtidal habitats

Fish assemblages on two inshore rocky subtidal sites on the west coast of Scotland, were studied using diver visual surveys on a monthly basis between September 1995 and December 1999. A total of 17 689 fishes and 26 species were recorded from the two sites, Saulmore Point (056°27′N; 005°24′W) near Oban and Davy's Rock (055°46′N; 004°53′W) on the Isle of Great Cumbrae. The gobiid Thorogobius eppiphiatus, dominated the Saulmore Point site; six fish species accounted for >93% of total abundance at that site. At Davy's Rock four species contributed at least 93% of total fish abundance, and the dominant species was the labrid Ctenolabrus rupestris. Total abundance of the dominant species displayed a clear seasonal trend, and this was significantly related to recorded daily average seawater temperature. A maximum abundance of 4.9 fishes m−2 was recorded in November 1998 at Davy's Rock and 2.5 fishes m−2 at Saulmore Point in October 1998. Multivariate analysis indicated a degree of variation in assemblage structure between winter and summer at both sites. A number of species showed some degree of interannual variation, in particular the gobiid Gobiusculus flavescens whose abundance increased by over 300 times over a 5 month period in 1998. Correlation analysis showed that variation in annual winter seawater temperature could act as an indicator of interannual variation in abundance of some of the dominant species utilizing rocky subtidal habitats.

Massive vein-filling gas hydrate: relation to ongoing gas migration from the deep subsurface in the Gulf of Mexico

A gas hydrate mound that contains massive, vein-filling, structure II gas hydrate occurs on the upper continental slope (∼540m water depth) of the Gulf of Mexico, southwest of the Mississippi Delta. The mound is located in the Green Canyon (GC) Block 185, adjacent to Jolliet Field in GC 184. Jolliet Field contains oil and gas that filled fault traps caused by salt deformation during late Pleistocene–Holocene time. In contrast to reservoir oil in Jolliet Field, which shows bacterial oxidation effects, the C1–C5 reservoir gas is unaltered by bacterial oxidation. Disassociated gas is assumed to have recently entered from the subsurface hydrocarbon system. Vertical migration of gas along faults is ongoing, manifested on the sea floor by gas vents, gas hydrate, complex chemosynthetic communities, and by a large gas plume that extends from the vents to the sea surface. The isotopic properties of C1–C5 hydrocarbons from reservoirs, gas vents, and gas hydrate correlate closely. Although outcropping gas hydrate is transiently stable because of variations in seawater temperature, the bulk of buried gas hydrate at GC 185 is stable and perhaps increasing in volume because of the copious gas flux. The massive accumulation of gas hydrate at the GC 185 site is attributed to the gas that has recently entered the vents, largely from Jolliet Field, and to the synchronous activation of fault conduits allowing gas migration to the sea floor. Synchronous late gas charge and faulting could also explain the wide distribution of gas hydrate across the upper Gulf slope.

Oxygen and carbon isotopic "dissection" of Baculites compressus (Mollusca: Cephalopoda) from the Pierre Shale (Upper Campanian) of South Dakota: Implications for paleoenvironmental reconstructions

A systematic stable isotopic study of an exceptionally well-preserved Baculites compressus specimen from the Pierre Shale (Upper Campanian) of South Dakota was conducted to assess whether the variations recorded in the calcareous shells of baculitids can be used as a reliable indicator of paleoenvironmental conditions. We sampled the B. compressus conch along four sampling profiles: (1) an ontogenetic traverse parallel to growth direction, (2) a virtually isochronous traverse along two different lirae delineated by growth lines, (3) a septal traverse, and (4) a shell-wall traverse through the conch wall. To date, the ontogenetic sequence is the longest record produced from baculitids. We interpret the isotopic variations determined from the ontogenetic, septal, and depth-profile traverses to be dominated by an environmental signal, especially in shell material deposited prior to septal crowding (i.e., maturity). In contrast, we interpret the isotopic variations determined from the isochronous traverse along the two different lirae to be altered by biological vital effects. Our results indicate that a careful sampling strategy that avoids strongly ornamented areas of the shell is required if a true paleoenvironmental signal is to be extracted from the calcareous shells of baculitids, and perhaps other ammonites as well. Our best estimate of seasonal seawater-temperature variation in the Late Campanian Western Interior Seaway at 42 degrees N, based on the oxygen isotopic data from the baculitid specimen, is 10.0 degrees C (range of 29.7 degrees C to 19.7 degrees C).

The Relation of Seafloor Voltages to Ocean Transports in North Atlantic Circulation Models: Model Results and Practical Considerations for Transport Monitoring*

Motionally induced voltage differences offer one of the few observational methods sensitive to changes in large-scale ocean transports. They present a useful contrast to most oceanographic data by virtue of their natural spatial integration, temporal continuity, and potentially long duration. However, widespread oceanographic use of the voltages observable with seafloor cables has been impeded by uncertainties of interpretation. Interpretation in terms of volume transport fluctuations has proved successful in the Straits of Florida and for a short cable in the easternmost part of the Bering Strait. Still, a number of older experimental studies resulted in disappointment, the Bering Strait work has been little known, and the Florida success might be a special case. The question considered in this paper is: Does a linear relationship between net transport and voltage difference fluctuations hold for long, open-ocean cables? This question is addressed by using a numerical model based on two years of results from the WOCE Community Modeling Effort, which simulated the wind-driven and thermohaline circulation in the North Atlantic using mean monthly winds and realistic topography with a resolution sufficient to permit mesoscale eddies. The model includes the effects of spatial and temporal variations of seawater temperature and salinity, electric current loops, the effects associated with the meandering of ocean currents over realistic topography and sediment thickness, realistic earth conductivity, and the spatially varying geomagnetic field. The main result is that the relationship between voltage and net cross-cable transport fluctuations can be remarkably linear over long distances. In view of the difficulties of long-term, large-scale transport monitoring by other methods, the implication of this work is that well chosen and carefully interpreted voltage observations hold great promise. This should be explored through renewed modeling, observation, and interpretation efforts.

Motional induction in North Atlantic circulation models

Motionally induced voltage differences provide one of the few observation methods sensitive to fluctuations of large‐scale ocean transports. However, uncertainties of interpretation have impeded widespread oceanographic use of voltages measured on open‐ocean cables. To resolve these uncertainties, we have developed a numerical simulation of the flow‐induced voltages in general circulation models. The model includes the effects of flow meandering, the spatial and temporal variations of seawater temperature and salinity, three‐dimensional Earth models with realistic sediment conductances, and the full physics applicable to the large‐scale, long‐period circulation when self‐induction may be neglected. For the oceanographic input, we used the World Ocean Circulation Experiment Community Modeling Effort's model, which simulates the wind‐driven and thermohaline circulation in the North Atlantic using mean monthly winds and realistic topography with resolution permitting mesoscale eddies. The results are in good agreement with the experimental cable calibration results from the Straits of Florida and with the Mid‐Ocean Dynamics Experiment. We find less influence of large‐scale electric current loops on the seafloor horizontal electric field than has previously been feared, our results supporting a local relationship of the seafloor electric field and ocean transport and the interpretation of seafloor horizontal electric field measurements in terms of local transport over much of the North Atlantic basin.

Comparative determinations of trace and minor elements in coral aragonite by ion microprobe analysis, with preliminary results from Phuket, southern Thailand

The ion microprobe technique was developed for semiquantitative analysis of trace and minor elements in coralline aragonite. The size of the microprobe beam (ca. 30 μm diameter) allows an examination of the spatial geochemical heterogeneity of coral skeletons on a much finer scale than has previously been possible. Of the elements investigated magnesium, calcium, rubidium, strontium, barium, and uranium appeared suitable for analysis under the operating conditions used although it was not possible to unequivocally confirm that 85Rb and 238U were not subject to molecular interferences. A homogenous carbonate standard was only available for magnesium so some relative ion yields were calculated using a standard silicate glass. Magnesium, rubidium, strontium, and barium concentrations were in reasonable agreement with previously reported values. Uranium concentrations were considerably lower, probably reflecting a miscalibration of the ion microprobe. Reproducibility of analysis was investigated by comparing immediately adjacent pairs of analyses on coral material. Although analytical accuracy was questionable, precision was good and concentration differences between samples reflect true variations in geochemistry. High resolution time series analyses of magneisum, rubidium, strontium, barium, and uranium in Porites lutea corals indicated that the aragonite was heterogeneous on a small spatial scale (over distances attributed to less than one month's skeletal growth). This heterogeneity does not appear to reflect expected variations in seawater temperature or chemistry. It may reflect the metal binding capacity of a heterogeneous organic matrix unevenly distributed throughout the coral skeleton. Individual coral colonies deposited substantially different ranges of Mg and Ba, within and between reef sites, which could lead to significantly different seawater:coral distribution coefficients being calculated between individuals of the same coral species.

Factors influencing the stable carbon and oxygen isotopic composition ofPorites lutea coral skeletons from Phuket, South Thailand

We determined the δ18O and δ13C composition of the same fixed growth increment in severalPorites lutea coral skeletons from Phuket, South Thailand. Skeletal growth rate and δ18O are inversely related. We explain this in terms of McConnaughey's kinetic isotopic disequilibria model. Annual trends in δ18O cannot be solely explained by observed variations in seawater temperature or salinity and may also reflect seasonal variations in calcification rate. Coral tissue chlorophylla content and δ13C of the underlying 1 mm of skeleton are positively related, suggesting that algal modification of the dissolved inorganic carbonate pool is the main control on skeletal δ13C. However, in corals that bleached during a period of exceptionally high seawater temperatures in the summer of 1991, δ13C of the outer 1 mm of skeleton and skeletal growth rate (over 9 months up to and including the bleaching event) are inversely related. Seasonal variations in °13C may reflect variations in calcification rate, zooxanthellae photosynthesis or in seawater δ13C composition. Bleached corals had reduced calcification over the 9-month period up to and including the bleaching event and over the event they deposited carbonate enriched in13C and18O compared with unaffected corals. However, calcification during the event was limited and insufficient material was deposited to influence significantly the isotopic signature of the larger seasonal profile samples. In profile, overall decreases in δ18O and δ13C were observed, supporting evidence that positive temperature anomalies caused the bleaching event and reflecting the loss of zooxanthellae photosynthesis.

Candesal: A canadian nuclear desalination system

The CANDESAL Nuclear Desalination System integrates two well established and proven technologies — reverse osmosis seawater desalination and CANDU nuclear power generation — into a single facility for the co-generation of both fresh water and electricity in relative proportions dictated by local requirements. By coupling the desalination plant with the reactor both thermally and electrically and by optimizing the system design, increases in the range of 20–40% in water production efficiency are achieved, depending on seawater conditions. These improvements result in significant reductions in desalination plant capital costs as well as levelized water costs. Through the illustrative use of site-specific applications studies, the real issues of designing a nuclear desalination plant for an actual operational situation, as opposed to simply addressing a single set of design conditions, are discussed. Fresh water production targets are achieved, without compromise in water quality or reverse osmosis system efficiency, over annual variations in inlet seawater temperature and total dissolved solids. The demand for water and electrical energy is critical in many parts of the world and the CANDESAL Nuclear Desalination System provides a readily available and economically attractive solution which meets both these needs without contributing to the ever-increasing global pollution problem. In addition, the installation and operation of such a system contributes positively to regional and national economies through the creation of jobs, industrial benefits and technology transfer.

Respiratory Rate and Assessment of Secondary Production in the Holothuroid Holothuria tubulosa (Echinodermata) from Mediterranean Seagrass Beds

Abstract. Respiration in Holothuria tubulosa was investigated in individuals from the Posidonia oceanica meadow off Lacco Ameno (Ischia Island, Italy). Respiratory rates increase with increasing body weight and increasing sea water temperature. Oxygen consumption of an average individual (7g dw body wall) ranges from 0.409 (14 °C) to 1.300 (26 °C) mg O2· h‐1. Data on population density, mean size of individuals, and annual sea water temperature variations allow an assessment of holothuroid production. Values of 45.65 and 13.75 kJ · m‐2· y‐1 were calculated for shallow (3 to 10 m) and deep (25 to 33 m) areas of the Posidonia meadow, respectively. Holothuroid production shows a bathymetric pattern similar to primary production of the Posidonia‐epiphytes complex and the production of Posidonia litter.

The vertical structure of seasonal variations of the sea-water temperature in the North Atlantic

The results of investigations on the seasonal variations of the water temperature field constructed from observational data based on the statistical method of variance analysis are reported. Oceanic areas with dominant semi-annual variations are discriminated. The depth of the seasonal sea-water temperature variation is estimated for the North Atlantic.

Seawater temperature and sublethal coral bleaching in Jamaica

Permanent study sites were established at 6 m, 12 m and 18 m on the West Fore Reef at Discovery Bay, Jamaica. Colonies of Montastrea annularis, Porites astreoides, Porites porites and Agaricia spp. were assessed for presence and extent of bleached tissue at two month intervals between October 1986 and September 1987. In 98% of all corals exhibiting a bleaching response, less than 25% of the colony appeared pale. In the remaining 2%, more than 25% of the tissue appeared pale. M. annularis, P. astreoides and Agaricia spp. showed a significant positive correlation between the percent of colonies exhibiting a partial bleaching response and seawater temperature. There was no significant difference in the percentage of colonies bleached between the three depths. M. annularis and Agaricia spp. exhibited a significantly higher percentage of colonies bleached than P. astreoides and P. porites. For M. annularis 15% of coral colonies studied showed 1–2 cm2 randomly seattered patches of pale tissue which remained constant throughout the study. The partial bleaching patterns observed in this study were never lethal and are considered, in part, to be a response to seasonal variations in seawater temperature.

FIELD AND CULTURE STUDIES OF A POPULATION OF ENDARACHNE BINGHAMIAE (PHAEOPHYTA) FROM SOUTHERN CALIFORNIA1

ABSTRACTAbundances of the erect, blade phase of Endarachne binghamiae J. Ag. (Scytosiphonales, Phaeophyta) varied seasonally at a southern California rocky intertidal site. Blade cover and density were much greater in the fall through early spring; blades were mostly absent from quadrats during the summer. Blade abundances were negatively correlated with both seasonal variations in seawater temperature and photoperiod. Laboratory culture studies failed to provide evidence for sexual reproduction. The life history appears to be of the “direct” type with plurangia‐produced zooids germinating into crustose disks. Most disks developed erect blade clusters under spring/fall (17° C) and winter (13° C) temperatures over the range of natural photoperiods employed (14:10, 12:12, 10:14 h LD). In contrast, cultures held under the summer temperature (21° C) produced almost entirely crustose growths regardless of photoperiod. Similar results were obtained for cultures grown at 100 and 200 μE · m−2· s−1. E. binghamiae blades were fertile throughout the year and produced viable zooids indicating that reproductive seasonality did not influence the seasonal pattern of blade abundance. Culture and field studies suggest that the initiation of new erect blade clusters from crustose disks is confined to the cooler months of the year (winter and spring). The summer reduction or absence of E. binghamiae blades appears to be due to increased mortality rates and temperature constraints on the development of new erect bladed thalli. Hypothetical causes of mortality are desiccation stress, sand burial, increased grazing activity and a genetically‐based short life span.

Distribution and variations of oceanic carbon dioxide in the western North Pacific, eastern Indian, and Southern Ocean south of Australia

The partial pressure of carbon dioxide (pCO2) in surface seawater was measured to clarify its time and space variation in the western North Pacific, eastern Indian and Southern Ocean south of Australia during the Southern Cross Cruise in 1968169, the BIOMASS Cruise in 1983/84 and the Ryofu-maru Cruises in 1984 and 1987. The pCO2 in surface seawater was high in high latitudes, coastal and equatorial regions and low in the subtropics. The spatial variation of pCO2 clearly reflects the general circulation of seawater, i.e., vertical mixing of seawater plays an important rijle in determining the pCO2 in surface seawater.Two kinds of periodicities during the annual cycle, which are caused by the variations in seawater temperature, vertical mixing and biological activities, were found off Japan's coast. The pCO2 in surface seawater obtained in the boreal winters of 1969 and 1984 suggests an increase due to the enhancement of CO2 flux from air to sea. The apparent increase was 20.0 f 10.6 ppm in the western North Pacific, and 24.4 8.3 ppm in the Southern Ocean, south of Australia.

Sea water temperature variation east of Taiwan

Temperature, wave and wind data over two years off Ho Peng, Shi Ti and Jang Yuan of east Taiwan are analyzed to study their seasonal variations. A model for predicting the mixed layer thickness is developed by use of wave data. The vertical profile of temperature indicates that there are basically three layers; mixed layer, thermocline layer and deep cold layer. The surface mixed layer appears in winter and disappears in summer. While surface water is warmer in summer than in winter, water at a depth of 50 m is warmer in winter than in summer. The seasonal variation in the deep cold layer is weak. The sea surface temperature is generally higher offshore than nearshore. The surface temperature off east Taiwan is almost equal to that in Taiwan Strait in summer, but in winter it is about 4°C warmer off northeast Taiwan than in the northeast of the Taiwan Strait, if compared at the same latitude. This is an effect of the seasonal variation of the Kuroshio. A model is developed for predicting the mixed layer thickness in terms of the input wave energy. The model successfully accounts for the observed features.

Long-term changes in some benthic species in the Firth of Clyde, with particular reference to Tellina tenuis da Costa

SynopisPresent knowledge of long-term changes in benthic species in the Firth of Clyde is reviewed.Recent work on the annual variations in seasonal cycles of the sand-dwelling bivalve Tellina tenuis da Costa shows some correlations with natural and man-made variations in seawater temperature. Between 1973 and 1984 inclusive good settlements of young occurred on the two beaches examined in the autumns of years when higher mean seawater temperatures occurred in June and July. The implications are discussed in relation to cycles of climatic change. In general, settlements at Hunterston, a thermally enriched area, were considerably greater than at Kames Bay, a site affected only by natural temperature changes. However, T. tenuis at Kames Bay grew to much larger maximum sizes than at Hunterston, except in 1979, when Hunterston animals were larger. The possible interactions of food availability and the modifying effects of heated discharges are discussed.Earlier results by Dr A. C. Stephen between 1926 and 1951 are reassessed in the light of present knowledge.

Living planktonic foraminifera from the eastern Arabian Sea

Living planktonic foraminifera from three cruises of the eastern Arabian Sea (R.V. Gaveshani, November 1982; Osiris II-MD-10, July 1976; and Osiris III-MD-13, June 1977) were analyzed in the present study. Planktonic foraminifera of the eastern Arabian Sea are much more abundant at 0 to 10 than at 0 to 200 m, but species diversity is less. G. ruber and G. sacculifer are the most abundant species in the eastern Arabian Sea water column. G. aequilateralis, G. glutinata, P. obliquiloculata, G. menardii, G. tenelus, G. hexagona, and G. pachyderma dwell preferentially in deeper water. In the November cruise, three assemblages were found: a winter tropical assemblage (southern Arabian Sea), a winter tropical assemblage (middle Arabian Sea), and a winter tropical upwelling assemblage (northern Arabian Sea). Another tropical upwelling assemblage was encountered during the July cruise. The variation of living planktonic foraminifera in the eastern Arabian Sea appears to be governed more by upwelling events, which vary seasonally and spatially, than by seasonal seawater temperature and latitude variations.