The Bellingshausen Sea earthquake of February 5, 1977: Evidence for ridge-generated compression in the Antarctic plate

Body- and surface-wave data from a magnitude M_s = 6.4 event in the Bellingshausen Sea are used to infer a thrust fault mechanism, with compressional stress directed parallel to the vector of relative motion between Antarctica and the Pacific plate at the nearby ridge. The solution would not, on the other hand, be compatible with stress fields involving absolute plate motion, such as asthenospheric drag.     

Future challenges for international management of ocean resources sustainable yield of fish stocks: Future international management

The paper gives a personal overview of fisheries management including the background to sustainable yield and the increasing importance of marine research for fisheries. It gives the characteristics of the marine environment, including the atmosphere, for international fisheries management. Conservation and the need for multispecies management are required and the paper discusses the increases in incidental catch and the effects of overfishing on target and by catch stocks. There are specific concerns of high seas management, including overlapping (straddling) and highly migratory fish stocks. The paper discusses fisheries management against a background of Agenda 21 of the Rio Conference and the 1982 UN Convention on the Law of the Sea.     

Long-term macrozoobenthos changes in a shallow boreal lagoon: Comparison of a recent biodiversity inventory with historical data

The European water framework directive (WFD) aims at achieving good ecological status of water bodies, which implies assessment of their current ecological quality status in respect to defined reference (pristine) conditions. In this paper, two historical biodiversity datasets (from 1920s and 1950s) and results from the recent inventory are used to trace the long-term changes of the macrozoobenthos in the eutrophic boreal lagoon of the Baltic Sea.In comparison of datasets the highest congruence was obtained for molluscs and malacostracan crustaceans, which also had a similar level of taxonomic emphasis between studies. Considering inconsistencies in methodology and taxonomic determination, only few species extinctions in these groups did likely occur during the last 100 years. Two amphipod species (Gammarus pulex and Gammarus lacustris) were not found during the recent survey, whereas five new species of this taxonomic group occurred in the lagoon since 1950s. The causes of these extinctions remain unclear; however displacement by established new amphipods cannot be excluded. Theodoxus fluviatilis was recently recorded in the very restricted area of the lagoon, while in earlier studies the species was mentioned as common and widely distributed in the water body. On the other hand, 10 gastropod species and 9 bivalves were reported for the first time in the lagoon and most likely have been overlooked in earlier surveys. Approximately 10% of the species have their origin outside the Baltic Sea basin and the number of invasions considerably exceeds the number of likely extinctions. Assessment scheme of such changes is unclear following WFD guidelines, therefore elaboration of a framework for evaluation of the alien species diversity in a context of local biodiversity should attain more effort when implementing the WFD.     

Biomagnification of persistent chlorinated and brominated contaminants in food web components of the Yellow Sea

Concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) were measured in 32 species inhabiting the Yellow Sea to assess their bioaccumulation potentials. The concentrations in these samples were lower than those reported for other countries or locations. Relatively high levels of BDE 209 in biota suggest an ongoing source of deca-BDE technical mixing within the Yellow Sea. The accumulation profiles of PCBs were uniform between species, but the concentrations of OCPs and PBDEs varied widely. Pelagic and benthic food-chain components were separated by their δ¹³C values. Significant positive correlations between δ¹⁵N and PCB 153, PCB 138, p,p′-DDE, oxy-chlordane, and trans-nonachlordane were found only for pelagic consumers, indicating that the pelagic food chain is an important bioaccumulation pathway for selected PCB and OCP compounds. The other compounds did not show any biomagnification through benthic and pelagic food chains, suggesting the lower bioaccumulation potentials of these contaminants.     

Contamination status of POPs and BFRs and relationship with parasitic infection in finless porpoises (Neophocaena phocaenoides) from Seto Inland Sea and Omura Bay,Japan

Contamination status of brominated flame retardants (BFRs) and persistent organic pollutants (POPs) in blubber of finless porpoises (Neophocaena phocaenoides) stranded along the coasts of Seto Inland Sea and Omura Bay in Japan were investigated. Levels of PCBs, DDTs and CHLs were significantly higher than those of HCHs, HCB, PBDEs and HBCDs. Concentrations of PBDEs and HBCDs, as well as organochlorine compounds in males increased with body length (p < 0.05). Among 14 PBDE congeners analyzed, BDE-47 was the predominant, which is similar to those generally reported in biota. PBDEs, HBCDs and PCBs showed no obvious temporal trend in concentrations during the study period, suggesting continuous environmental release of these chemicals. On the other hand, levels of DDT, CHLs and HCHs have decreased. Concentrations of PCBs in liver trematode infected individuals were significantly higher than those in not infected individuals, implying there could be a relationship between contaminant levels and parasitic infection.     

Economic valuation of the Seto Inland Sea by using an Internet CV survey

We estimate the economic value of the natural environment damaged in the Seto Inland Sea after the introduction of the Law on Temporary Measures for the Environmental Conservation of the Seto Inland Sea (Setouchi Law) and the value of the natural environment that survived, using a Contingent Valuation (CV) survey on an Internet web site. The CV survey contains three plans. Plan 1 is to restore 4 ha of reclaimed land. By estimating the Willingness To Pay (WTP) for plan 1, we can appraise the value of the natural environment that was damaged as a result of the original reclamation. Plan 2 is to transplant Zostera (eel-grass) into an area of 10 ha offshore. Plan 3 is to preserve the shore area, a natural habitat for rare animal species, under the National Trust Program. From the WTP for plans 2 and 3, we can estimate the value of the shore area and the areas a little farther offshore. The value of the natural environment damaged in the Seto Inland Sea as a result of reclaiming projects after the introduction of the Setouchi Law and the value of the existing natural environment of the Seto Inland Sea from the WTP for the plans were estimated to about 172 trillion yen (1.46 trillion dollars) and about 424 trillion yen (3.60 trillion dollars), respectively. The results indicate that in the 25 years since the introduction of the Setouchi Law, we have degraded every year about 6.88 trillion yen (58.5 billion dollars) worth of the natural environment by reclaiming. Some seaweed farms and natural shore areas, natural habitats to rare marine life-forms like the horseshoe crab and the fiddler crab have survived, but their value amounts to about 80% of Japan's GDP.     

Difference of mercury bioaccumulation in red mullets from the north-western Mediterranean and Black seas

The relationships between total mercury (Hg) concentration and stable nitrogen isotope ratio (δ¹⁵N) were evaluated in Mullus barbatus barbatus and M. surmuletus from the Mediterranean Sea and M. barbatus ponticus from the Black Sea. Mercury concentration in fish muscle was six times higher in the two Mediterranean species than in the Black Sea one for similar sized animals. A positive correlation between Hg concentration and δ¹⁵N occurred in all species. Increase in Hg concentration with δ¹⁵N was high and similar in the two Mediterranean fishes and much lower in the Black Sea species. Since this was neither related to trophic level difference between species nor to methylmercury (MeHg) concentration differences between the north-western Mediterranean and the Black Sea waters, we suggested that the higher primary production of the Black Sea induced a dilution of MeHg concentration at the base of the food webs.     

The Marmara Sea region: Seismic behaviour in time and the likelihood of another large earthquake near Istanbul (Turkey)

The North Anatolian Fault (NAF) extends for about 1500 km from Karliova to the east, to the Egean Sea in the west. The Marmara region, located near the western end of the NAF, is a tectonically active zone characterized by the transition between a strike slip stress regime and an extensional one in the Aegean Sea. Microseismic studies performed around the Marmara Sea in 1995 [Tectonophysics 316, 2000, 1], and just before the 1999 Izmit Earthquake Bull. Seism. Soc. Am. 92, 2002a, 361;J. Seismol. 6, 2002b, 287) permitted the analysis of the evolution of seismicity connected to this destructive earthquake and its sequels. Several observations indicate that the aftershock distribution fits well the EW orientation of the NAF, but the ruptures are not simple and linear as a first glance would suggest. Instead they are segmented in at least five pieces as shown by the slip variation and aftershock clusters, showing complexity at different scales (Bull. Seism. Soc. Am. 92, 2002a, 361). There is still a gap, across the northern border of the Marmara Sea that has not ruptured, and this is the only sector that did not break on the NAF since the 1939 great Erzincan earthquake. Will it rupture as a whole with a large magnitude earthquake, or by segments with smaller magnitude events? The Hurst analysis of the overall behaviour of the seismicity in the Marmara region since historical times shows that if a large earthquake occurs in the near future, it might break the complete gap. The Hurst character of the time variation of seismicity is persistent with H= 0.82. The aftershocks of the 1999 Izmit earthquake can be analyzed by using the Hurst method, showing an exceptionally high persistent memory.     

Bacterial and organic matter distribution in the sediments of the Thracian Sea (NE Aegean Sea)

Recently, black carbon has been introduced as the form of carbon that may be separated from the biologically mediated carbon cycle thereby representing the non-bioavailable fraction of the estimated organic carbon. It has been speculated that the bioavailability of organic matter may be a limiting factor for the presence of active bacteria within the sediments. In order to address this question, marine sediments were collected from the Thracian Sea (Eastern Mediterranean), a complex system impacted by riverine inputs and Black Sea water masses. In addition to counts of total bacteria, we estimated the fraction of active bacteria by using a destaining step to the DAPI staining method. Black carbon was also estimated following the thermal oxidation method in order to determine the fraction of the refractory organic matter. The fraction of black carbon to total organic carbon varied from 16% to 53% indicating that black carbon constitutes a significant pool of sedimentary organic carbon in the Thracian sea. A fraction ranging from 18% to 97% was scored as nucleoid containing cells. We did not record any significant differences in the fraction of nucleoid-containing bacteria among sediment depths (P<0.05) indicating that there was no accumulation of dead bacterial cells with depth. The same was observed for the fraction of black carbon and bioavailable organic carbon with sediment depth (P<0.05) indicating that benthic consumers are not the key regulators of the organic matter pool in these sediments but have a minor effect. A possible reason for these observations and for the uncoupling between the active bacterial fraction and the bioavailability of organic matter could be (i) the presence of refractory components in the estimated bioavailable organic matter and (ii) the hydrological and geological complexity of the study area. The North Aegean marginal slopes are highly unstable experiencing frequent seismic events. These events are capable of inducing sediment transport from the upper slopes thus altering the entire sediment profile. On the other hand, the significant correlations that were recorded between nucleoid-containing cells and phytopigments (chlorophyll a, phaeopigments, chloroplastic pigment equivalents) at all sediment depths indicate that bacterial communities respond immediately to the deposited phytodetritus, using it as a primary source of carbon and energy. Our data suggests that the Thracian Sea sediments are by no means homogeneous and can best be described as a mosaic controlled by numerous local and regional environmental factors.     

The 18.6 yr nodal modulation in the tides of Southern European coasts

The nodal modulation of the diurnal (K₁ and O₁) and semi-diurnal (M₂ and K₂) tidal constituents at the coasts of the Mediterranean Sea and the eastern Atlantic is estimated and its spatial variability mapped. Fourteen hourly tide gauge records each spanning more than 18 years are considered in this analysis. Ten tide gauges are located in the Mediterranean Sea and four in the Bay of Biscay. The nodal modulation of the most energetic tidal constituent (M₂) reaches up to 5 cm at the eastern Atlantic coasts, while within the Mediterranean Sea its modulation is in general less than 1.1 cm. The largest K₂ nodal modulation found is 3.7 cm in the eastern Atlantic coasts. In the Mediterranean Sea, smaller modulation amplitudes, ranging between 0.4 and 1.4 cm are found. The K₁ tide constituent has the largest amplitude nodal modulation within the Mediterranean Sea of 1.9 cm in the north Adriatic Sea, which is also larger than the modulation of this constituent at the eastern Atlantic coasts. The O₁ tide constituent has the highest amplitude nodal modulation (1.4 cm) at the eastern Atlantic coasts. In the Mediterranean Sea the maximum value is 1 cm in the north Adriatic Sea.     

The Sierra Club and the Law of the Sea

The office of International Environmental affairs of the Sierra Club is focusing its attention on a number of issues, identified at the UN Stockholm conference last year as significant. One of these is the Law of the Sea. This article is an abbreviated version of a preliminary paper prepared for a Working Party or Task Force that is examining the issues and attempting to produce an integrated view of all the issues.     

On a possible origin of the anomalous effects that were observed during the May 24, 2013 earthquake in the Sea of Okhotsk

The deep-focus Sea of Okhotsk earthquake that occurred on May 24, 2013 (h = 630 km, M _w = 8.3) was accompanied by anomalous effects that were unknown previously. A combined analysis of published data concerning the source rupture evolution and some features of the deep structure provided an explanation of some anomalous effects, such as the large number of aftershocks and the low level of ground shaking in the epicentral area. However, GPS observations revealed high coseismic vertical displacements in the area. The seafloor uplift in the Sea of Okhotsk and the adjacent coasts was 3–12 mm, peaking at the approximate center of the sea, while Kamchatka and the North Kuril Islands subsided by 3–18 mm, peaking at the Apacha station 190 km east of the earthquake epicenter. These maximum estimates are 1.2–1.8 times the analogous values (10 mm) for the Chile mega-earthquake of May 20, 1960 (M _w ~ 9.5). It is known that the large distances at which ground shaking is felt during deep-focus earthquakes are due to the fact that the body waves travel through the high-Q lower mantle. However, this does not explain the paradox of the present earthquake in the Sea of Okhotsk, viz., a constant intensity of shaking (two grades) in the range of epicentral distances between 1300 and 9500 km. The explanation requires consideration of the earth’s free oscillations excited by the earthquake.     

Radium in the near-surface Caribbean Sea

Recent radium measurements from the near-surface Caribbean Sea are presented. The surface horizontal and vertical distributions of²²⁶Ra are essentially the same as reported by Szabo et al. (1967) for the early 1960's. The²²⁶Ra activity at the surface is relatively uniform across the Caribbean, with an average of8.2±0.4dpm/100kg. The subsurface distribution to ～200 m averages7.8±0.4dpm/100kg and increases slowly below 200 m. reaching ～9.5 dpm/100 kg at 560 m. In contrast to²²⁶Ra, the surface concentration of²²⁸Ra was much more variable in both time and space. An average increase of 33% was found between 1968 and 1976 in the western Caribbean and during both years an anomalously high²²⁸Ra activity was found in the eastern Caribbean. These data support previous hypotheses that water entering the eastern Caribbean has been enriched in²²⁸Ra prior to entry and that variable mixing of the Atlantic water masses found to the northeast and southeast of the Lesser Antilles may produce temporal variations in the near-surface²²⁸Ra activity. Scatter plots of²²⁸Ra vs. salinity and sigma-t indicate that the near-surface vertical distribution of²²⁸Ra in the Caribbean Sea is predominantly influenced by advection. Thus²²⁸Ra cannot be used to study near-surface vertical mixing rates in this region.     

Geochemical studies on the Feshcha Springs,Dead Sea basin

The Feshcha springs issue in a 4 km long strip on the Dead Sea shores. They constitute two separate groups: a) T-N waters, similar in their salt composition, temperature and radon content to the many other members of the Rift Valley “Tiberias-Noit water association”. The hydrologic, radon, tritium and carbon-14 indicate they are mixtures of recent meteoric waters with ancient (trapped) T-N waters of an age of at least 18000 years. b) Z-Y waters which, like other members of the Dead Sea basin “Zohar-Yesha water group”, originate by a mixing of T-N waters with Dead Sea waters. This is seen in the chemical compositions and is confirmed by the oxygen-18 and deuterium data.     

Using blood samples to estimate persistent organic pollutants and metals in green sea turtles (Chelonia mydas)

Persistent organic pollutants (POPs) and heavy metals have been reported in a number of green turtle (Chelonia mydas) populations worldwide. However, due to ethical considerations, these studies have generally been on tissues from deceased and stranded animals. The purpose of this study was to investigate the use of blood samples to estimate the tissue contamination of live C. mydas populations. This study analysed 125 POP compounds and eight heavy metals in the blood, liver, kidney and muscle of 16 C. mydas from the Sea World Sea Turtle Rehabilitation Program, Gold Coast, Australia. Strong correlations were observed between blood and tissue concentrations for a number of POPs and metals. Furthermore, these correlations were observed over large ranges of turtle size, sex and condition. These results indicate that blood samples are a reliable non-lethal method for predicting chemical contamination in C. mydas.     

P/Ca in coral skeleton as a geochemical proxy for seawater phosphorus variation in Daya Bay, northern South China Sea

The P/Ca ratio in coral skeletons is considered to be a direct proxy for the nutrient P in seawater. We examined the reliability of this proxy by analyzing P/Ca in a Porites coral collected from a eutrophic area in the northern South China Sea. P concentrations were significantly higher compared to previously reported values from pristine and open seas, corresponding to the elevated nutrients from the study site. We compared coral P/Ca against recent in-situ records of seawater P concentrations. Our results show that P/Ca was primarily a function of TP sw rather than PO₄sw, and that the signal of skeletal P included not only phosphate, but also organic phosphorus. Besides the form of skeletal P, sub-sampling and analytical procedures and the distinctive nutrient regime were the most reasonable explanations for our results. We suggest that total P in coral skeletons may be an efficient proxy for seawater P variations and associated phytoplankton dynamics in eutrophic environments.     

The distribution of split shear-wave parameters in the backarc region of the South Kuril subduction zone

This paper reports a study in the distribution of parameters of split shear waves excited by deep earthquakes in the Sakhalin and Hokkaido area, with the orientation of the axes of symmetry in the earth being estimated assuming a viscoelastic anisotropic model for the mantle. A mantle flow along NW 310° ± 20° has been identified beneath the Japan Sea. The flow is inclined at an angle of 20–30° relative to the horizontal plane and is consistent with the motion of the Pacific plate. Beneath the southern Sea of Okhotsk the fast a-axis [100] of olivine is oriented NE 30 ± 15°, nearly parallel to the trend of the Kuril arc, while the c-axis [001] is inclined at ～35° relative to the horizontal plane. Bearing in mind the increased heat flow in the region, we assume the development of a mantle flow along the olivine c-axis at NW 300° ± 20° and with the shear plane [010] in the conditions of partial mantle melting (the B-type LPO). The lowest anisotropy (1–2.5%) was identified beneath Sakhalin and the greatest (3–5%) beneath the Japan Sea. An increasing degree of anisotropy is also noted to occur with an increasing depth of focus (down to 350 km).     

Heat flow in Eastern Egypt: The thermal signature of a continental breakup

The Red Sea is a modern example of continental fragmentation and incipient ocean formation. Heat flow data have been collected from eastern Egypt to provide information relating to the mode and mechanism of Red Sea opening. Preliminary heat flow data, including new data reported here, are now available from twenty-five sites in eastern Egypt and one site in western Sinai. A pattern of low to normal heat flow (35–55 mW m⁻²) inland with high heat flow (75–100 mW m⁻²) in a zone within 30 to 40 km of the coast is indicated.Moderately high heat flow (around 70 mW m⁻²) is indicated for the Gulf of Suez. The coastal zone thermal anomaly appears continuous with high heat flow previously reported for the Red Sea shelf. Heat production data indicate that the coastal thermal anomaly is not primarily related to crustal radiogenic heat production. The effects of rapid erosion may contribute to the anomaly, but are not thought to be the primary cause of the anomaly. If the anomaly is caused by lateral conduction from hot, extended, offshore lithosphere, the extension must have been active for the last 30 Ma or so, and a minimum of 100% extension is indicated. Alternatively, the anomaly is primarily caused by high mantle heat flow causing lithospheric thinning, centred beneath the Red Sea. The Red Sea is probably underlain by dominantly basic crust, formed either by intrusion into attenuated continental crust or sea-floor spreading, and for most purposes the crust formed in these two modes of extension may be essentially indistinguishable. Fission-track ages from eastern Egypt indicate that uplift started prior to, or at latest at the time of initial Red Sea opening, and this result, together with thermo-mechanical considerations, suggests an active asthenospheric upwelling beneath the Red Sea and high temperature in the lithosphere prior to extension.     

Predominance of anaerobic bacterial community over aerobic community contribute to intensify ‘oxygen minimum zone’ in the eastern Arabian Sea

The presence of a delicately poised mid-depth oxygen minimum zone (OMZ) makes the Arabian Sea a unique and important ecosystem. So far, various aspects responsible for its formation have been studied. However, the contributions from bacterial groups mediating its formation and maintaining its intensity are described for the first time in this study. Thus, we hypothesize that the bacterial dynamics along with organic carbon loading result in bringing about differences in the intensity of OMZ between two stations in the Eastern Arabian Sea (EAS). Water column from 2 stations, one from offshore and another from slope, in the EAS were examined for phytoplankton diversity and pertinent groups of culturable bacteria. Vertical profiles of dissolved oxygen, productivity, chlorophyll a, total organic carbon and different physiological groups of bacteria showed well-defined stratified patterns in tandem with physical and chemical stratifications of the water column. The phytoplankton diversity was higher at the slope station (SS) and was dominated by the heterotrophic dinoflagellates. The offshore station (OS) on the other hand, showed lower diversity dominated by diatoms (p<0.05). This observation could imply relatively higher autotrophy at the OS. Our results show that OMZ from these ‘oligotrophic’ regions is dominated by anaerobic bacteria. We believe that these bacteria contribute to intensify the OMZ in the EAS. Further, a higher abundance of viable anaerobic bacteria (TVC_anaero) and other anaerobic groups at the SS than the OS suggest that the OMZ is relatively much more intense near the slope. Besides, total organic carbon (TOC) load is three-fold higher at the SS than at OS implying its higher accumulation and lower degradability in slope waters. Settling of this more preserved organic carbon in mid-slope sediments in contact with OMZ results in one of the highest enrichments of sedimentary TOC in the world oceans.     

Stomach contents in Baltic fourhorn sculpin (Myoxocephalus quadricornis L.) with normal and deformed spinal vertebrae

In the northern part of the Baltic Sea, the Gulf of Bothnia, fourhorn sculpin (Myoxocephalus quadricornis) is one of the dominant fish species. A considerable proportion of the population (up to 54% of fish in gill net catches) have been reported to have spinal deformations, with a higher frequency in polluted than in clean areas. The stomach content of sculpins with normal and with severely deformed backbone were compared, but no statistically significant differences were revealed. The diet was generally dominated by the isopod Mesidotea entomon and three-spined stickleback (Gasterosteus aculeatus).