Low Seawater Temperature Research Articles

Correlated evolution between mode of larval development and habitat in muricid gastropods.

Larval modes of development affect evolutionary processes and influence the distribution of marine invertebrates in the ocean. The decrease in pelagic development toward higher latitudes is one of the patterns of distribution most frequently discussed in marine organisms (Thorson's rule), which has been related to increased larval mortality associated with long pelagic durations in colder waters. However, the type of substrate occupied by adults has been suggested to influence the generality of the latitudinal patterns in larval development. To help understand how the environment affects the evolution of larval types we evaluated the association between larval development and habitat using gastropods of the Muricidae family as a model group. To achieve this goal, we collected information on latitudinal distribution, sea water temperature, larval development and type of substrate occupied by adults. We constructed a molecular phylogeny for 45 species of muricids to estimate the ancestral character states and to assess the relationship between traits using comparative methods in a Bayesian framework. Our results showed high probability for a common ancestor of the muricids with nonpelagic (and nonfeeding) development, that lived in hard bottoms and cold temperatures. From this ancestor, a pelagic feeding larva evolved three times, and some species shifted to warmer temperatures or sand bottoms. The evolution of larval development was not independent of habitat; the most probable evolutionary route reconstructed in the analysis of correlated evolution showed that type of larval development may change in soft bottoms but in hard bottoms this change is highly unlikely. Lower sea water temperatures were associated with nonpelagic modes of development, supporting Thorson's rule. We show how environmental pressures can favor a particular mode of larval development or transitions between larval modes and discuss the reacquisition of feeding larva in muricids gastropods.

Regulation of bacterioplankton activity in Fram Strait (Arctic Ocean) during early summer: The role of organic matter supply and temperature

The bacterial turnover of organic matter was investigated in Fram Strait at 79°N. Both Atlantic Water (AW) inflow and exported Polar Water (PW) were sampled along a transect from Spitsbergen to the eastern Greenland shelf during a late successional stage of the main annual phytoplankton bloom in summer. AW showed higher concentrations of amino acids than PW, while organic matter in PW was enriched in combined carbohydrates. Bacterial growth and degradation activity in AW and PW were related to compositional differences of organic matter. Bacterial production and leucine-aminopeptidase along the transect were significantly correlated with concentrations of amino acids. Activity ratios between the extracellular enzymes β-glucosidase and leucine-aminopeptidase indicate the hydrolysis potential for polysaccharides relative to proteins. Along the transect, these ratios showed a higher hydrolysis potential for polysaccharides relative to proteins in PW than in AW, thus reflecting the differences in organic matter composition between the water masses. Q10 values for bacterial production ranged from 2.4 (±0.8) to 6.0 (±6.8), while those for extracellular enzymes showed a broader range of 1.5 (±0.5) to 23.3 (±11.8). Our results show that in addition to low seawater temperature also organic matter availability contributes to the regulation of bacterial growth and enzymatic activity in the Arctic Ocean.

Comparison of the fecundity rate of Caligus rogercresseyi infesting Atlantic salmon (Salmo salar L.) on farms in two regions of Chile

Monthly sampling of adult lice on a salmon farm located in Region XI was carried out between October 2011 and September 2012 to assess the reproductive behaviour of Caligus rogercresseyi (43°34′LS; 74°78.9LW). The fecundity data were compared with those obtained in Region X (Lat 42°S) for the period 2006–2007. Results have shown that those from the farm in Region XI were smaller than the female lice collected in Region X in the period 2006–2007. In contrast, the male lice collected from Region XI were 14% larger than the males collected from Region X. Even though the average length of the egg sac string and the number of eggs per string were larger in Region XI in comparison with Region X, the egg length was 10% smaller in Region XI. The differences recorded in this study could be attributed to differences in the environmental conditions observed between both regions. Region XI is highly influenced by the Humboldt current, with lower seawater temperature in comparison with Region X.

Reproductive cycle of Spisula solida (L.) (Mollusca: Bivalvia) on the southwest coast of Spain

The reproductive cycle of Spisula solida (L., 1758) was investigated for the first time in the southwest of Spain, using specimens collected from Punta Umbría (Huelva), between April 2001 and May 2002. A total of 2805 individuals of shell lengths ranging from 9.1 to 38.4 mm were analysed. The gonad development was determined by means of histological methods and variations of dry weight. Five gametogenic stages were identified (I-Immature, II-Maturing, III-Ripe, IV-Spawning, V-Post-spawning). The sex-ratio obtained was 5:4 (χ 2 = 6.12, df = 1, p > 0.01), males being more abundant than females. Two hermaphrodite individuals were recorded. Development of the gonad began in November and spawning occurred between December and June, with maximum peaks in April (82% males) and May (87% females). The period of sexual rest took place from July to October. Gametogenesis in this species is a response to low seawater temperatures, and spawning occurs with low temperatures that increase progressively.

Carbonate system variability in the Gulf of Trieste (North Adriatic Sea)

The seasonal variability of the carbonate system in the waters of the Gulf of Trieste (GoT) was studied at PALOMA station from 2008 to 2009, in order to highlight the effects of biological processes, meteorological forcings and river loads on the dynamics of pHT, CO2 partial pressure (pCO2), dissolved inorganic carbon (DIC), carbonate ion concentration (CO3=), aragonite saturation state (ΩAr) and total alkalinity (AT).During winter, low seawater temperature (9.0 ± 0.4 °C) and a weak biological activity (−10.7 < AOU < 15.7 μmol O2 kg−1) in a homogeneous water column led to the lowest average values of pCO2 (328 ± 19 μatm) and ΩAr (2.91 ± 0.14). In summer, the water column in the area acted as a two-layer system, with production processes prevailing in the upper layer (average AOU = −29.3 μmol O2 kg−1) and respiration processes in the lower layer (average AOU = 26.8 μmol O2 kg−1). These conditions caused the decrease of DIC (50 μmol kg−1) and the increase of ΩAr (1.0) values in the upper layer, whereas opposite trends were observed in the bottom waters. In August 2008, during a hypoxic event (dissolved oxygen DO = 86.9 μmol O2 kg−1), the intense remineralisation of organic carbon caused the rise of pCO2 (1043 μatm) and the decreases of pHT and ΩAr values down to 7.732 and 1.79 respectively.On an annual basis, surface pCO2 was mainly regulated by the pronounced seasonal cycle of seawater temperature. In winter, surface waters in the GoT were under-saturated with respect to atmospheric CO2, thus acting as a sink of CO2, in particular when strong-wind events enhanced air–sea gas exchange (FCO2 up to −11.9 mmol m−2 d−1). During summer, the temperature-driven increase of pCO2 was dampened by biological CO2 uptake, as consequence a slight over-saturation (pCO2 = 409 μatm) turned out. River plumes were generally associated to higher AT and pCO2 values (up to 2859 μmol kg−1 and 606 μatm respectively), but their effect was highly variable in space and time. During winter, the ambient conditions that favour the formation of dense waters on this continental shelf, also favour a high absorption of CO2 in seawater and its consequent acidification (pHT decrease of −0.006 units during a 7-day Bora wind event). This finding indicates a high vulnerability of North Adriatic Dense Water to atmospheric CO2 increase and ocean acidification process.

The invasive gastropod Crepidula fornicata: reproduction and recruitment in the intertidal at its northernmost range in Wales, UK, and implications for its secondary spread

The establishment and spread of a non-native species in an introduced range depends to a large extent on the performance of the species under the prevailing environmental conditions. The spawning, larval and spatfall periods of the invasive gastropod Crepidula fornicata were monitored in the intertidal zone at its northernmost range in Wales, UK, between February 2010 and January 2011. The duration of the reproductive season was similar to that recorded from more southerly European populations. Spawning and larval release occurred throughout most of the year even at low seawater temperatures of 16 °C. Recruitment was low and likely controlled by post-settlement mortality. These observations suggest that C. fornicata’s northwards spread in Welsh waters will not be limited by seawater temperature negatively affecting reproduction, but by processes acting after larval release. These data show the importance of incorporating settlement and post-settlement processes into studies on recruitment success when aiming to predict the potential spread of a potentially harmful invader such as C. fornicata.

Seawater Temperature and Wind Speed Dependences and Diurnal Variation of Ambient Noise at the Snapping Shrimp Colony in Shallow Water of Southern Sea of Korea

The seawater temperature and wind dependences and diurnal variation of the ambient noise at the snapping shrimp colony in shallow water of the southern sea of Korea were investigated. The ambient noise levels are significantly affected by the snapping shrimp sound, when the bottom seawater temperature increases and the wind speed decreases. However, they are not exceptively almost affected by the snapping shrimp sound when the wind speed decreases at low seawater temperatures (<10 °C). In diurnal variation, the ambient noise levels are also significantly affected by the snapping shrimp sound in the morning and night time zones. This study shows that the activity of the snapping shrimp affecting the variation in ambient noise level in shallow water can be related to the wind speed as well as the seawater temperature. This study also shows that the snapping shrimp in diurnal activity can be more active in the morning and night time zones.

Seawater Temperature and Wind Speed Dependences and Diurnal Variation of Ambient Noise at the Snapping Shrimp Colony in Shallow Water of Southern Sea of Korea

The seawater temperature and wind dependences and diurnal variation of the ambient noise at the snapping shrimp colony in shallow water of the southern sea of Korea were investigated. The ambient noise levels are significantly affected by the snapping shrimp sound, when the bottom seawater temperature increases and the wind speed decreases. However, they are not exceptively almost affected by the snapping shrimp sound when the wind speed decreases at low seawater temperatures (<10 °C). In diurnal variation, the ambient noise levels are also significantly affected by the snapping shrimp sound in the morning and night time zones. This study shows that the activity of the snapping shrimp affecting the variation in ambient noise level in shallow water can be related to the wind speed as well as the seawater temperature. This study also shows that the snapping shrimp in diurnal activity can be more active in the morning and night time zones.

A Study on the Low Seawater Temperature and Marine Tributes in the 17th Century

A Study on the Low Seawater Temperature and Marine Tributes in the 17th Century

Heat transfer analysis and experimental verification of casted heat exchanger in non-icing and icing conditions in winter

Seawater-source heat pump systems (SWHP) are recognized to be outstanding heating, cooling and water heating systems. A large number of SWHP systems have been used in residential and commercial buildings in coastal areas due to the attractive advantages of high efficiency and environmental friendliness. In this paper, two mathematical models that described heat transfer process of casted heat exchanger (CHE) adopted by SWHP systems in the icing and non-icing conditions in winter have been developed and validated by an experimental study. The CHE is consisted of pipes immersed in the seawater and used for transferring heat between the seawater and the heat exchanger pipes of the SWHP. In addition, a computer code has been implemented to simulate the effects of flow rate of the secondary refrigerant, length of the CHE and the temperature of the seawater on the heat transfer performance. The effect of the ice outside the pipe due to the low seawater temperature on heat transfer has been discussed and the comparison of the heat transfer rate in two conditions demonstrates that the effect of icing on heat transfer performance is great. As a result, application of SWHP systems with CHE in coastal areas in China is feasible due to the favorable geographical conditions and environment.

Acoustic Characteristics of the Snapping Shrimp Sound Observed in the Coastal Sea of Korea

The typical temporal waveforms, spectra, and water-temperature dependence of the snapping shrimp sound in the coastal sea of Korea were investigated. The peak-to-peak source levels of the snapping shrimp sound at three sites in the coastal sea, at water depths of 8, 10, and 40 m, were also investigated. The waveform and dominant frequency response band of the sound were similar to those observed under laboratory conditions. The broad peak frequency components of the normalized average snapping shrimp sound spectra measured in nine different coastal sea areas were differently determined by superposition of the peak frequency components of individual snapping shrimp spectra for the each area. The sound did not significantly affect the ambient noise level at a low seawater temperature (<10 °C). The mean peak-to-peak source levels of the snapping shrimp sound at the sites with water depths of 8 and 10 m were similar, with estimated values of 176 ±3 and 175 ±3 dB (re 1 µPa at 1 m), respectively. However, the estimated mean peak-to-peak source level at the site with a water depth of 40 m was 184 ±2 dB (re 1 µPa at 1 m). The differences in the mean peak-to-peak source levels at the three sites could be caused by the differences in the ambient pressure at the sea bottoms of the sites. For water depths below 10 m, the mean peak-to-peak source levels of the snapping shrimp sound were much lower than those estimated in a previous study, in which the water depth at the experimental site was 6.1 m. On the other hand, the mean peak-to-peak source level at the site with a water depth of 40 m was similar to that estimated in a previous study. This study shows that the mean peak-to-peak source levels of the snapping shrimp sound may change as water depth is largely varied.

Successful antiscalant field trial — Optimization at higher pH and seawater temperature — Larnaca Desalination Plant

A desalination plant has been operating for a number of years at elevated pH both at the first and second reverse osmosis stages at feed seawater temperature up to 30°C. The main reason for operating at higher pH was to enhance the boron rejection capability of existing membranes and thus omit the operation of the second stage whenever lower seawater temperatures allow to do so and subsequently produce more water with less energy. However, a higher pH in conjunction with high seawater temperatures creates conditions for membrane scaling. Therefore an appropriate cost effective antiscalant has to be used at minimum dose level. This paper describes field trials of selecting and applying an appropriate antiscalant and the dosing optimisation process in function of feed seawater temperature and pH.

Cost reduction of subsea gas production systems using emerging hydrate remediation technology

Gas flowlines are presenting flow assurance challenges in hydrate management resulting from low ambient seawater temperatures in an increasing number of deepwater developments. When the equilibrium hydrate temperature of the produced fluid is above the minimum seabed temperature, and the hydrate inhibition system fails, there is a risk of hydrate blockage in the subsea system. The industry-preferred approach for hydrate blockage remediation is dual sided depressurisation (DSD). The objective is to depressurise the flowline below hydrate onset conditions, thus allowing hydrate dissociation and safe disposal of the gas inventory. This is generally performed by one of two methods: installation of a dual flowline system for facility-based depressurisation (CAPEX impact) or by connecting a mobile offshore drilling unit (MODU) to an appropriate wellhead or christmas tree (XT) to allow simultaneous depressurisation at the MODU and the facility (OPEX impact). It is recognised that both methods incur significant costs. Typically the cost, schedule and availability uncertainties of bringing in a MODU to solve these production stoppages are too high. Consequently, subsea developments often select the increased CAPEX option. An optimisation of the MODU-based intervention method is the subject of this paper. The feasibility of using a lightweight intervention vessel (e.g. an offshore support vessel) in place of the MODU is investigated. In discussing this optimisation, this paper also presents an introduction to hydrate remediation theory, some practical challenges, case studies and vessel requirements.

Long-Term Relationships between the Marine Environment, Krill and Salps in the Southern Ocean

Long-term variations (1975–2002) in climatology of marine environmental parameters, Antarctic krill,Euphausia superba, and the pelagic tunicate,Salpa thompsoni, were compared within the Atlantic Sector of the Southern Ocean. Sea water temperature in the top 400 m increased at a rate of 0.020–0.030°C ⋅ yr−1, which was accompanied by the dissolved oxygen decline. Top 100 m water layer became fresher with lower concentrations of phosphates and nitrates, while at subsurface layers (200–400 m) both salinity and nutrients showed small increasing trend. Unlike phosphates and nitrates, silicate concentrations decreased in the entire water column. Shorter-term water temperature dynamics closely correlated with the El Nino events expressed as the Southern Oscillation Index which in turn was linked to the propagation of the Antarctic Circumpolar Wave (ACW). The variations of sea-ice extent matched well the changes in both air and water temperatures. In general, abundance of krill and salps showed opposite to each other trends. Due to large area considered in this study, no significant relationships between abiotic factors and both krill and salps were found. However, our analysis demonstrated that krill abundance was greater in years with lower sea water temperature, greater sea-ice extent and higher nutrient concentration, while salps showed the opposite pattern.

Successful antiscalant field trial — Optimization at higher pH and seawater temperature, Larnaca desalination plant

Larnaca Desalination Plant (LDP) has lead the way in operating for a number of years at elevated pH both at the first and second Reverse Osmosis (RO) stages at higher feed sea water temperature up to 30 °C. The main reason for the higher pH was to enhance the boron rejection capability of existing membranes and thus reduce the need for a second stage at lower sea water temperatures and subsequently produce more water at less energy. However, higher pH in conjunction with high sea water temperatures create conditions for membrane scaling. Therefore an appropriate cost effective antiscalant has to be used with minimum dosing rate. This article describes field trials of choosing and applying an appropriate antiscalant and dosing optimisation as a function of feed sea water temperature and pH.

Partial pressure and air–sea CO 2 flux in the Aegean Sea during February 2006

Data on the distribution of fCO 2 were obtained during a cruise in the Aegean Sea during February 2006. The fCO 2 of surface water ( fCO 2 sw) was lower than the atmospheric fCO 2 ( fCO 2 atm) throughout the area surveyed and Δ fCO 2 values varied from −34 to −61 μatm. The observed under-saturation suggests that surface waters in the Aegean represent a sink for atmospheric CO 2 during the winter of 2006. Higher fCO 2 sw values were recorded in the ‘less warm’ and ‘less saline’ shallow northernmost part of the Aegean Sea implying that the lower seawater temperature and salinity in this area play a crucial role in the spatial distribution of fCO 2 sw. A first estimate of the magnitude of the air–sea CO 2 exchange and the potential role of the Aegean Sea in the transfer of atmospheric CO 2 was also obtained. The air–sea CO 2 fluxes calculated using different gas transfer formulations showed that during February 2006, the Aegean Sea absorbs atmospheric CO 2 at a rate ranging from −6.2 to −11.8 mmol m −2 d −1 with the shipboard recorded wind speeds and at almost half rate (−3.5 to −5.5 mmol m −2 d −1) with the monthly mean model-derived wind speed. Compared to recent observations from other temperate continental shelves during winter period, the Aegean Sea acts as a moderate to rather strong sink for atmospheric CO 2. Further investigations, including intensive spatial and temporal high-resolution observations, are necessary to elucidate the role of the Aegean Sea in the process of transfer of atmospheric CO 2 into the deep horizons of the Eastern Mediterranean.

Seasonality in the infection and invasion of Marteilioides chungmuensis in the Pacific oyster Crassostrea gigas

The protozoan parasite Marteilioides chungmuensis causes irregular enlargement of the ovary in the Pacific oyster Crassostrea gigas. The parasite invades the oyster through the epithelial tissue of the labial palp, replicates in the connective tissue, and then moves to the gonad, producing spores inside the oocytes. In this study the seasonality and invasion period of the parasite into the host was investigated over a 1 yr cycle. Uninfected 1 and 0 yr old (spat) oysters were placed in an epizootic area every month from July 2004 to July 2005 and September 2005 to March 2006, respectively, and left for 1 mo. Labial palps and gonad were sampled monthly and examined for infection by nested PCR and histological observations. Prevalence of infection detected by PCR was 70% or higher from August to October, but declined sharply in November and reached 7% or lower from February to April. To explain the low detection rate in winter, 1 yr old uninfected oysters were placed in an epizootic area in winter (water temperature: 8 to 10 degrees C) for 2 wk and then transferred to M. chungmuensis-free seawater at 24 degrees C. Although prevalence of infection was ca. 7% before transfer to heated seawater, levels of 87% were detected after 1 wk. After a 3 wk exposure to heated seawater, parasites were found in host oocytes by histological observation. It was concluded that the low prevalence in winter was due to insufficient replication of M. chungmuensis at low seawater temperatures, resulting in levels not detectable by nested PCR, and not to the absence of invasion.

The effect of different holding systems and diets on the performance of spiny lobster juveniles, Jasus edwardsii (Hutton, 1875)

This study evaluated the growth and survival of lobster juveniles over 8 months when fed fresh Perna canaliculus mussel and stocked at a density of 35 ind. m − 2 in one of three holding systems: a prototype sea-cage design, a commercial sea-cage design, and small experimental land-based holding tanks. At the same time the growth, survival and nutritional condition of lobsters fed fresh mussel in the prototype sea-cages were compared with lobsters feeding only on the biofouling of the sea-cages or fed two artificial diets (dry and moist) three times a week. Survival in the prototype sea-cages (83.3 ± 2.3%) was similar to the experimental flow-through tanks (87.9 ± 8.0%) but significantly higher than the commercial sea-cage (55.4 ± 1.8%). Furthermore, the prototype sea-cages resulted in significantly higher specific growth rate (SGR = 0.96% BW day − 1 ) than the other system designs (flow-through tank SGR = 0.86 BW day − 1 and commercial sea-cage SGR = 0.77% BW day − 1 ). The growth rate in the prototype sea-cages was one of the fastest ever recorded for this species, over this size range of juveniles (3–31 g) and at comparatively low seawater temperatures (15.2 °C). The survival of lobsters in the prototype sea-cages did not differ between the three experimental feeding regimes. However, growth when feeding on biofouling alone or with the addition of artificial diets was comparatively inferior to the lobsters fed mussels (SGR = 0.96% BW day − 1 ; survival = 83.3 ± 2.3%). Lobsters fed the dry formulated diet (SGR = 0.78% BW day − 1 ; survival = 79.3 ± 1.2%) grew significantly faster than on the moist formulated diet (0.60% BW day − 1 ; 59 ± 17.8%) or on the biofouling only (0.38% BW day − 1 ; 66.3 ± 4.9%). The growth of lobsters fed the dry formulated diet in the prototype sea-cage was better than in previous tank growth studies using experimental diets and was probably attributable to animals feeding on biofouling of the sea-cages. Digestive gland histology supported the growth trends, with lobsters fed fresh mussel and the dry formulated diet being in best nutritional condition at the end of the growth experiment. The results indicate that sea-cage culture of juvenile spiny lobsters can provide significant growth advantages over tank systems possibly due to supplementary nutrition from biofouling. However, sea-cage structural design, feeding and diet type are important factors influencing the performance of J. edwardsii juveniles in sea-cages.

Multistratigraphy of condensed ammonoid beds of the Rappoltstein (Berchtesgaden, southern Germany): unravelling palaeoenvironmental conditions on ‘Hallstatt deep swells’ during the Reingraben Event (Late Lower Carnian)

Two new sites of condensed Hallstatt Red Limestones were found in the Rappoltstein mountain range near Berchtesgaden (SE Bavaria). Conodont and ammonoid assemblages allowed for a concise age-dating of the lower two of seven already described Hallstatt ammonoid horizons as latest Ladinian to Lower Carnian (Upper Triassic). Biostratigraphy, microfacies analysis and stratigraphic cross-correlation of other Hallstatt sites allowed the documentation of the Late Lower Carnian ‘Reingraben Event’ within a mixed allochthonous–autochthonous carbonaceous lithofacies at the Rappoltstein, and gave further insights into the special architecture of the so-called ‘Hallstatt deep swells’ and the Hallstatt Basin. δ18Ophos of conodont apatite was measured in order to reconstruct marine palaeotemperatures. The reconstructed low seawater temperatures may be at least due to different palaeoclimatic scenarios that could have preceded the ‘Carnian crisis’.

Pilot plant demonstration of energy reduction for RO seawater desalination through a recovery increase

Energy reduction through a recovery increase was demonstrated for RO seawater desalination using a pilot plant (5 m 3/h). Energy reduction was possible through a recovery increase. Based on the relationship developed in this study, a recovery increase from 30% to 50% reduced energy consumption by half from 10 kWh/m 3 to 5 kWh/m 3. Achieving the target recovery of 50% depended upon such parameters as temperature, salinity, and operating pressure. The target recovery was possible when seawater temperature was higher than 24°C under the study conditions. When the temperature was low and salinity was high, the target recovery was never achieved. Low seawater temperature together with high salinity required excessive operating pressure (73 bar) for the pilot plant to achieve the target recovery, which led to damage of the RO membranes. Subsequently, the target recovery could not be attained and TDS leakage occurred. Temperature was found important for recovery. The linear relationship between recovery and seawater temperature predicted that recovery could increase by almost twice the temperature, which is more than what is expected from the viscosity effect. Based on the relationship developed, the maximum salinity that this pilot plant could achieve as the target recovery was 33‰. As expected, the pilot plant was effective in turbidity removal as well as in red-tide removal.