Sea In August Research Articles

Marine gravimetry using the strapdown gravimeter SGA-WZ

Gravity can be measured in many ways, from static-point observations to dynamic measurement using land vehicles, ships, aircrafts and satellites. China has developed a gravimetry system based on SINS (Strapdown Inertial Navigation System) named SGA-WZ. This system is the first strapdown gravimetry system in China. Some airborne gravimetry campaigns have been implemented using SGA-WZ. The flight tests indicate that the accuracy of SGA-WZ is 1.5 mGal at a 4.8 km resolution. To test the performance of SGA-WZ when installed on a ship, a marine gravimetry campaign was conducted in the South China Sea in August 2013. In the test, a state-of-the-art commercial sea gravimeter, the LaCoste & Romberg (LR the evaluation of the repeatability was based on repeat lines. The measurement and in-movement alignment algorithm for strapdown gravimeters in the sea are discussed, and the results and analysis of this test are presented. The results from the repeated lines and the comparison with L&R showed that the accuracy of SGA-WZ is at the level of 1 mGal with a resolution between 0.4 and 0.8 km for shipborne gravimetry. These results indicate that the strapdown gravimetry system SGA-WZ can be used in marine gravimetry and the moving base alignment method can improve the computation efficiency greatly when using the strapdown gravimetry system.

Characterization and Genome Sequence of Marine Alteromonas gracilis Phage PB15 Isolated from the Yellow Sea, China

A novel marine Alteromonas gracilis siphovirus, phage PB15, was isolated from the surface water of the Yellow Sea in August 2015. It has a head diameter of 58±5nm head and a contractile tail approximately 105±10nm in length, and overall, the morphology suggests that PB15 belongs to the family Siphoviridae. PB15 phage is stable at over the temperature range 0-60°C. The best MOI of these phage was 0.1, and infectivity decreased above 60°C. The results suggest that phage is stable at pH value ranging between 3.0 and 11.0. Chloroform test shows that PB15 is not a lipid-containing phage. A one-step growth curve with a strain of A. gracilis gave a latent period of 16min and rise period of 24min and burst size of 60PFU/cell. Genomic analysis of PB15 reveals a genome size of 37,333bp with 45.52% G+C content, and 61 ORFs. ORF sequences accounted for 30.36% of the genome sequence. There is no obvious similarity between PB15 and other known phages by genomic comparison using the BLASTN tool in the NCBI database.

Decadal trends in phytoplankton production in the Pacific Arctic Region from 1950 to 2012

This paper provides a synthesis of available in situ primary production (PP) measurements from the Pacific Arctic Region (PAR), collected between 1950 and 2012. Seasonal integrated primary production (IPP) across the PAR was calculated from 524 profiles, 340 of which were also analyzed to determine the average vertical distribution of PP rates for spring, summer and fall months. The Chirikov Basin and Chukchi Shelf were the most productive areas, with the East Siberian Sea, Chukchi Plateau and Canada Basin the lowest. Decadal-scale changes were indicated in the southern Chukchi Sea, and across Hanna Shoal. In the southern Chukchi Sea in August, IPP increased significantly from 113±35mgCm-2 d-1 in 1959 and 1960 to 833±307mgCm-2 d-1 in the 2000s. Increases in the magnitude of IPP were accompanied by variations in the vertical distribution, the subsurface peak observed in the 1959/60 was not present in the 2000s. The mechanism behind this change was undetermined but could have included changes in stratification, mixing or surface distribution of water masses as well as methodological differences. Over Hanna Shoal, the phytoplankton surface bloom now occurs earlier by several weeks compared to 1993, linked to increases in light due to earlier sea- ice retreat. In 1993 with sea ice still present in the region the surface bloom occurred in August, in 2002 and 2004 this same period was characterized by open water and low surface PP and strong subsurface production. This dataset provides a region-wide quantification of IPP and decadal trends and highlights the need for a cooperative monitoring program to observe the long-term impacts of climate change in the Arctic ecosystem.

Compositional variations of brown seaweeds Laminaria digitata and Saccharina latissima in Danish waters

Around Denmark, Laminaria digitata and Saccharina latissima are particularly common macroalgae species and are considered as prospective candidates for biorefineries. In this study, the carbohydrate composition and protein levels of L. digitata and S. latissima from three different sites in Denmark were compared for 1 year, and compositional variations of wild L. digitata harvested in August from the North Sea was monitored for 3 years. Glucan levels of L. digitata were consistently higher than those of S. latissima irrespective of harvest site and time of the year. Glucan levels in wild L. digitata from Kattegat peaked in October with 37.0% by dry weight compared to 22.6% by dry weight in wild S. latissima (Kattegat) and were accompanied by lower ash contents (18.5% w/w in L. digitata versus 26.5% w/w inS. latissima). Alginate contents were almost constant throughout the year, but mannuronic/glucuronic acid ratios differed between species and location from 1.33 to 3.64. Wild L. digitata harvested from the North Sea in August contained >50% glucans by weight and had low ash contents for three consecutive years (2012–2014). Compositional variation of the seaweeds was mainly related to season but also varied with species, location, and within populations. Among environmental variables (temperature, salinity, phosphate, nitrate, ammonia), only temperature was found to correlate with the chemical composition of the seaweeds. Amino acid profiles were dominated by glutamic acid, aspartic acid, and alanine and varied with season, especially for L. digitata from the North Sea, and location. Total nitrogen contents fluctuated more between samples than the actual protein contents; hence, application of a common N-to-protein factor cannot be recommended.

Seasonal distribution of short-tailed shearwaters and their prey in the Bering and Chukchi seas

Abstract. The short-tailed shearwater (Ardenna tenuirostris) is one of the abundant marine top predators in the Pacific; this seabird spends its non-breeding period in the northern North Pacific during May–October and many visit the southern Chukchi Sea in August–September. We examined potential factors affecting this seasonal pattern of distribution by counting short-tailed shearwaters from boats. Their main prey, krill, was sampled by net tows in the southeastern Bering Sea/Aleutian Islands and in the Bering Strait/southern Chukchi Sea. Short-tailed shearwaters were mainly distributed in the southeastern Bering Sea/Aleutian Islands (60 ± 473 birds km−2) in July 2013, and in the Bering Strait/southern Chukchi Sea (19 ± 91 birds km−2) in September 2012. In the Bering Strait/southern Chukchi Sea, krill size was greater in September 2012 (9.6 ± 5.0 mm in total length) than in July 2013 (1.9 ± 1.2 mm). Within the Bering Strait/southern Chukchi Sea in September 2012, short-tailed shearwaters occurred more frequently in cells (50 × 50 km) where large-sized krill were more abundant. These findings, and information previously collected in other studies, suggest that the seasonal northward movement of short-tailed shearwaters might be associated with the seasonal increase in krill size in the Bering Strait/southern Chukchi Sea. We could not, however, rule out the possibility that large interannual variation in krill abundance might influence the seasonal distribution of shearwaters. This study highlights the importance of krill, which is advected from the Pacific, as an important prey of top predators in the Arctic marine ecosystem.

Results of complex surveys in the East Siberian Sea in August 2015

Data on oceanographic conditions, composition of plankton communities, benthic and demersal fish and invertebrates in the southern East Siberian Sea are presented by results of the complex survey conducted in August 2015, The bottom trawl survey assessed 10 species of fish and 3 species of jellyfish with total biomass 1900 t. Arctic cod Boreogadus saida dominated absolutely in the benthic ichthyocenose (60.6 % of the total biomass). Besides, 3 species of shrimps, 1 crab species, 4 species of gastropods, and 6 other taxonomic groups of macrobenthos including starfish and isopods were found in trawl catches, with the average biomass of macrobenthos 41.7 kg/km 2 . In the bottom samples of macrobenthos, 12 taxonomic groups were presented, with predominance of bivalves, polychaetes, isopods, and amphipods (summary 95 % of the total biomass).

어획특성을 이용한 삼치(Scomberomorus niphonius)의 회유경로 추정

Seasonal catch distributions of large purse seines and daily landings of coastal set nets were analyzed to understand the migration path of the Spanish mackerel Scomberomorus niphonius around Korean waters. The Spanish mackerel start to move toward the coastal region in the South and West Sea in May for spawning and stay until July, when spawning finishes. Afterwards, they start to migrate to the East China Sea and the southern East Sea and are found irrespective of the onshore and offshore regions. Therefore, they disappear from the offshore region during the spawning season in June and July, and a new recruitment population of age 0 begins to inflow into the coastal fishing grounds in the South Sea and West Sea in August, one month earlier than in the Japanese coastal region of the East Sea.

The level and bioaccumulation of Cd, Cu, Cr and Zn in benthopelagic species from the Bering Sea

The Bering Sea is an area of high biological productivity, with large populations of sea-birds, demersal and pelagic fishes, so it seemed desirable to assess the bioaccumulation of trace metals in the marine organisms from this area. However, few data on trace metal concentrations are available for the benthopelagic organisms from the Bering Sea till now. Ten specimens of benthos (including 120 biological samples) were collected in the western Bering Sea in August 2008 during the 3rd Chinese National Arctic Research Expeditions, and the concentration of Cd, Cu, Cr and Zn determined using atomic absorption spectrometry. Zn, Cr and Cd concentrations in muscle tissues of the crab species were much higher than those from fish and cephalopod species, and the highest concentration of Cu was observed in the muscle tissues of Cylichna nucleoli. The results showed a similar hierarchy for Zn, Cr, Cd and Cu concentrations among different tissues as follows: hepatopancreas>muscle tissue>gonad. Bioconcentration factors indicated that benthic organisms had high accumulation abilities for Zn and Cu.

Hydrochemical studies of deep-water basins of the Caspian Sea in August–September 2013 aboard the R/V Nikifor Shurekov

Hydrochemical studies of deep-water basins of the Caspian Sea in August–September 2013 aboard the R/V Nikifor Shurekov

Hydrochemical Studies of Deep-Water Basins of the Caspian Sea in August–September 2013 Onboard the R/V “Nikifor Shurekov”

Hydrochemical Studies of Deep-Water Basins of the Caspian Sea in August–September 2013 Onboard the R/V “Nikifor Shurekov”

Intrusion of low-salinity water into the Yellow Sea Interior in 2012

Abnormally low-salinity water was detected in the surface layer of the central region of the Yellow Sea in August 2012. The presence of such low-salinity water in the Yellow Sea interior has never been reported previously. To understand the origin of this low-salinity water, oceanographic and wind data were analyzed, and the circulation of the surface layer was also examined in the Yellow and East China Seas using a numerical ocean model. The results confirmed that typhoons caused the low-salinity water. Two consecutive typhoons passed from east to west across the East China Sea, around the Changjiang Bank in early August 2012. Strong easterly and southeasterly winds created by the typhoons in the Yellow and East China Seas drove the low-salinity water to the north along the coast of China and northeastward toward the central region of the Yellow Sea, respectively. Usually, the northward drifting of Changjiang Diluted Water along the coast of China ends around the Jiangsu coast, where the drifting is blocked and is turned by the offshore Eulerian residual current. Therefore, the Changjiang Diluted Water does not intrude more into the Yellow Sea interior. However, in 2012, the low-salinity water drifted up to the Shandong Peninsula along the coast of China, and formed massive low-salinity water in the Yellow Sea interior combining with the other low-salinity water extended toward the central region of the Yellow Sea directly from the Changjiang Bank. Thus, the typhoons play a key role in the appearance of abnormally low-salinity water in the Yellow Sea interior and it means that the Yellow Sea ecosystem could be significantly influenced by the Changjiang Diluted Water.

Intrusion of the Pearl River plume into the main channel of the Taiwan Strait in summer

The Penghu Channel is the main channel connecting the East and South China Seas, two of the largest marginal seas in the world. Located in the southeast of Taiwan Strait, the Penghu Channel is usually covered by the high salinity water from the South China Sea and the Kuroshio. However, we observed abnormal low-salinity water in the Penghu Channel during a cruise through the southern Taiwan Strait and northern South China Sea in August 2008. We argue that the normalized alkalinity is a good indicator for the identification of a river plume as it is not affected by rainwater. Using satellite-derived water transparency and chlorophyll images and field-measured alkalinity, the source of this low salinity water was found to be the intrusion of the Pearl River plume. A significant phytoplankton bloom across the entire Taiwan Strait occurred with the intrusion event. The intrusion was not a unique event, as we also found a strong jet-shaped Pearl River plume intruding into the Penghu Channel in the summer of 2009 from cloud-free satellite-derived images. Time series satellite data reveal that the Pearl River plume intrudes into the Penghu Channel in the summer of most years. Multiple data analysis and modeling simulation indicate that a large river discharge and strong southwesterly winds on the shelf may be responsible for the significant intrusion of the Pearl River plume into the Penghu Channel in summer. As the Pearl River plume has a high nutrient and dissolved inorganic carbon content, combined with the strong northward flows through the Penghu Channel, such intrusions may contribute to the nutrient dynamics and carbon budget of the East and northern South China Seas.

2013년 8월, 9월 동해 남부연안 살오징어 유생 분포

Paralarvae of the common squid, Todarodes pacificus Steenstrup were sampled with the bongo net (diameter: 60 cm, mesh: ) by using oblique tow method with the oceanographic research vessel (Tamgu 12) at 21 stations along the southwestern coastal waters of the East Sea in August and September, 2013. Paralarvae were collected 16 ind./ in August and 7 ind./ in September at approximately, and bottom depth was from 70 m to 500 m. Mantle length of paralarvae was from 1.7 to 6.0 mm. Paralavae were distributed mainly in offshore stations in August and near by Cape Janggi in September. Optimum embryo survival temperature () was formed shallower than 35 m depth for almost stations where paralarvae were existed, and survival temperature () for embryo stage was located shallower than 75 m.

CARIBIC DOAS observations of nitrous acid and formaldehyde in a large convective cloud

Abstract. The chemistry in large thunderstorm clouds is influenced by local lightning-NOx production and uplift of boundary layer air. Under these circumstances trace gases like nitrous acid (HONO) or formaldehyde (HCHO) are expected to be formed or to reach the tropopause region. However, up to now only few observations of HONO at this altitude have been reported. Here we report on a case study where enhancements in HONO, HCHO and nitrogen oxides (NOx) were observed by the CARIBIC flying laboratory (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container). The event took place in a convective system over the Caribbean Sea in August 2011. Inside the cloud the light path reaches up to 100 km. Therefore the DOAS instrument on CARIBIC was very sensitive to the tracers inside the cloud. Based on the enhanced slant column densities of HONO, HCHO and NO2, average mixing ratios of 37, 468 and 210 ppt, respectively, were calculated. These data represent averages for constant mixing ratios inside the cloud. However, a large dependency on the assumed profile is found; for HONO a mixing ratio of 160 ppt is retrieved if the total amount is assumed to be situated in the uppermost 2 km of the cloud. The NO in situ instrument measured peaks up to 5 ppb NO inside the cloud; the background in the cloud was about 1.3 ppb, and hence clearly above the average outside the cloud (≈ 150 ppt). The high variability and the fact that the enhancements were observed over a pristine marine area led to the conclusion that, in all likelihood, the high NO concentrations were caused by lighting. This assumption is supported by the number of flashes that the World Wide Lightning Location Network (WWLLN) counted in this area before and during the overpass. The chemical box model CAABA is used to estimate the NO and HCHO source strengths which are necessary to explain our measurements. For NO a source strength of 10 × 109 molec cm−2 s−1 km−1 is found, which corresponds to the lightning activity as observed by the World Wide Lightning Location network, and lightning emissions of 5 × 1025 NO molec flash−1 (2.3–6.4 × 1025). The uncertainties are determined by a change of the input parameters in the box model, the cloud top height and the flash density. The emission rate per flash is scaled up to a global scale and 1.9 (1.4–2.5) tg N a−1 is estimated. The HCHO updraught is of the order of 120 × 109 molec cm−2 s−1 km−1. Also isoprene and CH3OOH as possible HCHO sources are discussed.

Assessing trend and variation of Arctic sea-ice extent during 1979–2012 from a latitude perspective of ice edge

Arctic sea-ice extent (in summer) has been shrinking since the 1970s. However, we have little knowledge of the detailed spatial variability of this shrinking. In this study, we examine the (latitudinal) ice extent along each degree of longitude, using the monthly Arctic ice index data sets (1979–2012) from the National Snow and Ice Data Center. Statistical analysis suggests that: (1) for summer months (July–October), there was a 34-year declining trend in sea-ice extent at most regions, except for the Canadian Arctic Archipelago, Greenland and Svalbard, with retreat rates of 0.0562–0.0898 latitude degree/year (or 6.26–10.00 km/year, at a significance level of 0.05); (2) for sea ice not geographically muted by the continental coastline in winter months (January–April), there was a declining trend of 0.0216–0.0559 latitude degree/year (2.40–6.22 km/year, at a significance level of 0.05). Regionally, the most evident sea-ice decline occurred in the Chukchi Sea from August to October, Baffin Bay and Greenland Sea from January to May, Barents Sea in most months, Kara Sea from July to August and Laptev Sea and eastern Siberian Sea in August and September. Trend analysis also indicates that: (1) the decline in summer ice extent became significant (at a 0.05 significance level) since 1999 and (2) winter ice extent showed a clear changing point (decline) around 2000, becoming statistically significant around 2005. The Pacific–Siberian sector of the Arctic accounted for most of the summer sea-ice decline, while the winter recovery of sea ice in the Atlantic sector tended to decrease. Keywords: NSIDC ice index; Arctic; sea-ice extent; ice-edge latitude. (Published: 11 September 2014) Citation: Polar Research 2014, 33 , 21249, http://dx.doi.org/10.3402/polar.v33.21249

Accidental exposure to electromagnetic fields from the radar of a naval ship: a descriptive study

Part of a crew on a Norwegian naval ship was exposed to the radar waves for approximately 7 min from an American destroyer during an incident at sea in August 2012. Information about the exposure was not given by the navy. This is a description of what happened with the crew on board after this event. 14 persons had been on the ship bridge or outside on the deck during the exposure and the rest of the crew had been inside the ship. 27 persons were examined at a hospital 6-8 months after the event, as they had developeda large number of symptoms from different organ systems. They were very worried about all types of possible adverse health effects due to the incident. All were examined by an occupational physician and anophthalmologist, by an interview, clinical examinations and blood tests at the hospital. The interview of the personnel revealed that they had not experienced any major heating during the episode. Their symptoms developed days or weeks after the radar exposure. They had no objective signs of adverse health effects at the examination related to the incident. Long-term health effect from the exposure is highly unlikely. The development of different symptoms after the incident was probably due to the fear of possible health consequences. Better routines for such incidents at sea should be developed to avoid this type of anxiety.

Spatiotemporal statistical analyses reveal predator-driven zooplankton fluctuations in the Barents Sea

There is limited statistical support for top-down effects on plankton in oceanic ecosystems. We quantify the combined effects of key planktivorous fish, invertebrates and climate on mesozooplankton dynamics in the Barents Sea. Zooplankton biomass was measured during Russian and Norwegian surveys in April–May and June–July 1959–1990 and August–early October (1981) 1984–2010. We found that zooplankton biomass in the central and northern Barents Sea in August–October showed pronounced multi-year fluctuations that were strongly negatively correlated with the total biomass of planktivorous fish. Fish predation explained >50% of the interannual variability in the biomass of medium-sized and large mesozooplankton in these parts of the Barents Sea and the predation effects remained significant while accounting for effects of climate variables. Spatiotemporal statistical analyses for different zooplankton size fractions supported the interpretation of top-down control, predominantly from capelin, on the zooplankton. In the southwestern Barents Sea the fluctuations were less pronounced and uncorrelated to total biomass of planktivorous fish, suggesting weaker top-down control by fish in this region, characterised by higher productivity and higher diversity of the predators. We suggest that predator-driven zooplankton fluctuations may play an important role in the ecosystem dynamics of the Barents Sea and potentially other Arcto-boreal shelves.

Nearshore Fish Assemblages of the Northeastern Chukchi Sea, Alaska

The Arctic ecosystem is changing rapidly, yet information on nearshore fish assemblages for the northeastern Chukchi Sea is extremely limited. To address this information gap, we sampled nearshore fish assemblages with a beach seine and a small bottom trawl at six stations in the northeastern Chukchi Sea in August 2007, 2008, and 2009, and in September 2009. Catch and species composition differed by gear type and between sample periods, including the two in 2009. A total of 16 039 fish representing 18 species were captured in 24 beach seine hauls, and 3108 fish representing 24 species were captured in 48 trawl tows. Beach seine catch was dominated by capelin (83%), and trawl catch was dominated by Arctic cod (56%). Species that were good discriminators between gear types were capelin (seine) and slender eelblenny (trawl), and unidentified small sculpins were the most common taxa caught with both gear types. Capelin and Arctic cod captured by either gear type were mostly juveniles (judging by size). Variability among sampling periods in catch and species composition within gear types can likely be attributed to annual variations in environmental conditions, including differences in water temperature (range: 2˚–9˚C). The shallow nearshore environment of the northeastern Chukchi Sea provides important habitat for many fish species and is extremely vulnerable to disturbance. Loss of sea ice from global warming may open up formerly inaccessible areas to oil and gas exploration, vessel traffic, and commercial fishing. Thus, long-term monitoring of nearshore fish assemblages in the Alaskan Arctic is necessary for managers to make informed decisions in this fragile environment.

The first record of Maeotias marginata (Modeer, 1791) (Cnidaria, Hydrozoa) from Finland, northern Baltic Sea

The hydromedusa, Maeotias marginata (Cnidaria, Hydrozoa), was observed in the low salinity (ca 4) archipelago of Southwest Finland in the northern Baltic Sea in August 2012. The species is considered to be native to the Sea of Azov. The only previous records of M. marginata in the Baltic are from 200 km south in western Estonia, in 1999-2003.

Application of Buoy Observations in Determining Characteristics of Several Typhoons Passing the East China Sea in August 2012

The buoy observation network in the East China Sea is used to assist the determination of the characteristics of tropical cyclone structure in August 2012. When super typhoon “Haikui” made landfall in northern Zhejiang province, it passed over three buoys, the East China Sea Buoy, the Sea Reef Buoy, and the Channel Buoy, which were located within the radii of the 13.9 m/s winds, 24.5 m/s winds, and 24.5 m/s winds, respectively. These buoy observations verified the accuracy of typhoon intensity determined by China Meteorological Administration (CMA). The East China Sea Buoy had closely observed typhoons “Bolaven” and “Tembin,” which provided real-time guidance for forecasters to better understand the typhoon structure and were also used to quantify the air-sea interface heat exchange during the passage of the storm. The buoy-measured wind and pressure time series were also used to correct the intensity of “Damrey” initially determined by CMA.