The relationship between the behavioral activity and the underwater vocalization of the beluga whale (<Emphasis Type="Italic">Delphinapterus leucas</Emphasis>)

The underwater vocalizations of the beluga whale summering in Onega Bay (64°24′N, 35°49′E) were recorded in June–July of 2008. The vocalizations were classified into five major whistle types, four types of pulsed tones, click series, and noise vocalizations. To determine the relationship between the behavioral activity and the underwater vocalizations, a total of fifty-one 2 minute-long samples of the audio records were analyzed in the next six behavioral contexts: directional movements, quiet swimming, resting, social interactions, individual hunting behavior, and the exploration of hydrophones by beluga whales. The overall vocalization rate and the percentage of the main types of signals depend on the behavior of the belugas. We suggest that one of the whistle types (the “stereotype whistle”) is used by belugas for long-distance communications, while other whistle types (with the exception of “squeaks”) and three types of pulsed tones (with the exception of “vowels”) are used for short distance communication. The percentage of “squeaks” and “vowels” was equally high in all the behavioral situations. Thus, we assume that “squeaks” are contact signals. “Vowels” have a specific physical structure and probably play a role in identification signals. A high rate of the click series was observed in the process of social interactions.     

Studies of the structure of the Solovetsky reproductive gathering of beluga whales (<Emphasis Type="Italic">Delphinapterus leucas</Emphasis>) in the White Sea using the photo identification method

The structure of the reproductive gathering of beluga whales (RG) was studied near Cape Beluzhii in the Solovetsky Islands in the White Sea by the photo identification of individuals in 2007–2008; in addition, the peculiarities of the seasonal and interseasonal dynamics of the RG incomings were analyzed. The gathering is formed by predominantly females and calves of different ages, which visit the RG area as stable “family” groups. About 15% of the observed females come to Beluzhii Cape every year and stay there during the whole summer season; thus, forming the regular part of the RG. The other animals come there for a certain time period, which is probably preconditioned by their physiological readiness for coupling and procreation for some of the females. When comparing our data with the catalogue of the visually registered beluga whales’ markers (1996–2008), we found that most of the identified animals of the Solovetsky RG appear here during one summer season or even with an off period of several years despite the significantly regular findings of most of them for this area. We conclude this may be linked with the natural changes of the individual markers due both to the shedding and the sexual cycle in the mature animals. Our data allow concluding that the total population of the Solovetsky PG is higher than was reported before using the visual supervision methods.     

Distribution of ephyrae and polyps of jellyfish <Emphasis Type="Italic">Aurelia</Emphasis><Emphasis Type="Italic">aurita</Emphasis> (Linnaeus 1758) <Emphasis Type="Italic">sensu lato</Emphasis> in Mikawa Bay,Japan

We surveyed the distribution of colonies of polyps of Aurelia aurita sensu lato (s.l.) in Mikawa Bay, Japan. First, we surveyed the distribution of ephyrae of A. aurita s.l. at 75 stations encompassing the whole of Mikawa Bay in early 2008. A total of 37 ephyrae were sampled mostly from fishing ports. Ephyrae were most abundant around the islands located near the mouth of the bay, and decreased from the western part to the eastern part of Mikawa Bay. Next, we selected five fishing ports in Mikawa Bay where ephyrae occurred and surveyed the underside of floating piers and underwater overhangs of wharfs. We found dense colonies of polyps of A. aurita s.l. under nearly all of the floating piers at the two islands located near the mouth of the bay. Fitting a logistic regression model to the dataset showed that the percentage coverage of Aurelia polyps was significantly greater at the two islands compared with the other locations. In addition, the coverage of Aurelia polyps was greater when the coverage of other fouling organisms was in the range of 65–90%, and the coverage of Aurelia polyps was lower on floating piers with a vinyl surface and on concrete wharfs. The combined distribution of polyp colonies of A. aurita s.l. in Ise Bay and Mikawa Bay suggested that A. aurita s.l. in the two bays probably forms a single population and shoals of medusae mainly originate from protected harbors along the mouth-part of the bays.     

The role of gametes of the macroalgae <Emphasis Type="Italic">Ascophyllum nodosum</Emphasis> (L.) Le Jolis and <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> L. (Fucales,Phaeophyceae) in summer nanoplankton of the White Sea coastal waters

Studies of macrophytes in the coastal zone of the Artic Seas, including the White Sea, have shown the essential role of these algae in the activity of the coastal half-latitude ecosystems. In summer, during the macrophyte reproduction period, a great number of reproduction products are released into the water. For a short time, this considerably affects the ratio of the nanoplankton in the populations that inhibit the vast and shallow coastal areas. At different coastal sites in Chernorechenskaya Inlet, Kadalaksha Bay, during the period of intensive reproduction of Ascophyllum nodosum and Fucus vesiculosus, 42 plankton samples were collected in 2005. During this period the concentration of antherozoids in the water reached 55000 cells/ml (216 mg C/m³). The number of eggs was within the range of 0.05–0.7 cells/ml. The proportion of antherozoids in the total biomass of nanoplankton varied at different coastal sites from 0.37 to 99%, with a mean of 46% for the reproduction period of A. nodosum, and only 7% for the reproduction period of F. vesiculosus. As was shown by counts of F. vesiculosus female gametes in sedimentation traps, 1 m² of the macrophyte bed (assuming 100% coverage) produces 18000–108000 eggs per day (0.33–2 mg C). The calculated flux of the reproductive material from the brown algae beds to the coastal water shows good agreement with the sample counts.     

Morphological identification of <Emphasis Type="Italic">Alexandrium</Emphasis> species (Dinophyceae) from Jinhae-Masan Bay,Korea

Outbreaks of paralytic shellfish poisoning (PSP) and dense blooms caused by Alexandrium species in Jinhae-Masan Bay, Korea have been nearly annual events for many years. However, excluding some Alexandrium species responsible for PSP, there are no critical reports on the morphology of Alexandrium species in this bay. To identify the Alexandrium species based on detailed morphological features, vegetative cells collected water samples and established by the incubation of resting cysts isolated from sediment trap samples were analyzed. Four species of Alexandrium were identified: Alexandrium affine, A. fundyense, A. catenella, and A. insuetum. Morphological features of these species were basically consistent with those outlined in previous studies. However, the ventral pore and the connecting pore on the sulcal plate, which have been accepted as diagnostic characteristics for the identification of A. fundyense and A. catenella, need to be reevaluated, indicating that useful morphological features for identifying these two species should be recommended to avoid confusion in the classification of species in genus Alexandrium.     

Vertical Distributions of Larvae of the Clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> and the Striped Horse Mussel <Emphasis Type="Italic">Musculista senhousia</Emphasis> in Eastern Ariake Bay,Southern Japan

We have examined the vertical distributions of planktonic bivalve larvae, particularly the clam Ruditapes philippinarum and the mussel Musculista senhousia which are common and abundant on tidal flats of eastern Ariake Bay, southern Japan. Submersible pumping gear was used to take samples at 2 stations every 2 hours during the spring tide over a whole tidal cycle and/or through daytime and nighttime. Water samples were pumped up from 3 to 5 depths from the surface to sea bottom. Regardless of tidal cycles, D-shaped larvae were concentrated near the surface, while umbo larvae were found at the surface to intermediate depths. On average, these larval densities were significantly higher at the station close to the shore than the offshore station, with no significant difference between daytime and nighttime and between flood and ebb tides at each station. The velocity and direction of water movement at both stations revealed remarkable difference between the surface and bottom waters. The larvae at the surface may quickly disperse and be transported elsewhere, while those in water close to the sea bottom may tend to be retained.     

Molecular phylogeny of the genus <Emphasis Type="Italic">Chondracanthus</Emphasis> (Rhodophyta), focusing on the resurrection of <Emphasis Type="Italic">C. okamurae</Emphasis> and the description of <Emphasis Type="Italic">C. cincinnus</Emphasis> sp. nov.

Determining the taxonomic status of the red algal genus Chondracanthus based on morphological characters is challenging due to the similarity and high degree of plasticity of the thallus. Since the taxonomic history of several Chondracanthus species remains unclear, we analyzed the plastid rbcL and mitochondrial COI genes of the specimens from Korea and Japan, in combination with morphological observations, to examine their phylogenetic relationships. Our results confirmed the distinction of C. okamurae, which is separated from C. intermedius, and identified a novel species, C. cincinnus sp. nov. Three species (C. okamurae, C. intermedius and C. cincinnus) formed a monophyletic clade with C. tenellus. C. okamurae is distinguished by linear, narrow, cylindrical to compressed, slightly recurved axes, and a high-intertidal to subtidal distribution. It was collected from Korea and Japan, while C. intermedius was identified from Japan only. A new species, Chondracanthus cincinnus sp. nov., is characterized by linear, compressed, strongly recurved axes, and a low-intertidal to subtidal distiribution. Based on the molecular phylogeny using rbcL and COI data, we herein resurrect C. okamurae as a distinct species and identify C. cincinnus as a new species.     

Effects of temperature on growth,photophysiology, Rubisco gene expression in <Emphasis Type="Italic">Prorocentrum donghaiense</Emphasis> and <Emphasis Type="Italic">Karenia mikimotoi</Emphasis>

To explore the effects of temperature changes on dinoflagellate bloom succession in the coastal waters of the East China Sea, changes in the growth, photophysiology, and Rubisco gene expression of Prorocentrum donghaiense and Karenia mikimotoi, two harmful algal species, were investigated at different temperatures (16 to 28°C). The maximal specific growth rate and the maximal mRNA expression of Rubisco gene in P. donghaiense and K. mikimotoi occurred at 20 and 24°C, respectively. The photosynthetic activity of P. donghaiense was generally stable, but K. mikimotoi photosynthesis increased when temperatures rose from 16 to 28°C. The effective photochemical efficiency (F _q ^′ /F _m ^′ ) and the maximal relative electron transfer rate (rETR_max) of K. mikimotoi increased significantly with increasing temperature, and the lowest and highest values occurred at 16 and 28°C, respectively. It seems that P. donghaiense has higher photosynthetic capacity than K. mikimotoi due to its higher F _q ^′ /F _m ^′ , rETR_max, and photosynthetic efficiency (α). However, K. mikimotoi has a higher growth rate than P. donghaiense. These results suggest that the photosynthetic activity and genetic responses of dinoflagellates are species-dependent. It is likely that temperature changes affect species composition during blooms, leading to the observed patterns of bloom succession.     

Winter thermal inversion and <Emphasis Type="Italic">Trichodesmium</Emphasis> dominance in north-western Bay of Bengal

Clear thermal inversion was observed with cold surface waters (< 24°C) overlying the warm (> 26°C) subsurface water in the coastal waters of the northwestern Bay of Bengal during winter (January 2015). Simultaneously, preponderance of the cyanobacteria Trichodesmium erythraeum was observed dominating the phytoplankton community with > 90% of total population, reaching maximum density of 9.8 × 10⁵ filaments/L. Further, the Trichodesmium predominance was associated with low water temperature (< 24°C).     

Blooms of <Emphasis Type="Italic">Trichodesmium erythraeum</Emphasis> in the South Eastern Arabian Sea during the onset of 2009 summer monsoon

This study presents in situ evidence for the blooms of Trichodesmium erythraeum observed in the shelf waters of the South Eastern Arabian Sea (SEAS) during the onset of the southwest monsoon in June 2009. Evidence showed that water surface discoloration was caused by the accumulation of T. erythraeum, and that the water column contained a colony of T. thiebautii. The surface water color in the bloom region varied from pale brown to pinkish red. Pale brown indicated healthy algae at the peak of its photosynthetic activity, while pinkish red indicated the presence of photosynthetically less active filaments. Zooplankton abundance, especially copepodites, in the bloom area substantiated the theory that Trichodesmium filaments are excellent epiphytes to which the copepodites cling. The bloom area was very fertile with copious quantities of dissolved oxygen (6.85 ml L^?1), PO₄-P (0.108 μmol L^?1) and SiO₄ (1.29 μmol L^?1). Lower NO₃-N (0.028 μmol L^?1) values in the bloom area did not appear to affect Trichodesmium growth from molecular nitrogen fixation. However, lower NO₃-N values altered the normal phytoplankton composition of this area.     

The spatial distribution of surface <Emphasis Type="Italic">f</Emphasis>CO<Subscript>2</Subscript> in the Southwestern East Sea/Japan sea during summer 2005

Fugacity of CO₂ (fCO₂), temperature, salinity, nutrients, and chlorophyll-a were measured in the surface waters of southwestern East Sea/Japan Sea in July 2005. Surface waters were divided into three waters based on hydrographic characteristics: the water with moderate sea surface temperature (SST) and high sea surface salinity (SSS) located east of the front (East water); the water with high SST and moderate SSS located west of the front (West water); and the water with low SST and SSS located in the middle part of the study area (Middle water). High fCO₂ larger than 420 μatm were found in the West water. In the Middle water, CO₂ was undersaturated with respect to the atmosphere, with values between 246 and 380 μatm. Moderate fCO₂ values ranging from 370 to 420 μatm were observed in the East water. For the East and West waters, estimates of temperature dependency of fCO₂ (12.6 and 15.1 μatm °C⁻¹, respectively) were rather similar to a theoretical value, indicating that SST is likely to be a major factor controlling the surface fCO₂ distribution in these two regions. In the Middle water, however, the estimated temperature dependence was somewhat lower than the theoretical value, and relatively high concentrations of surface chlorophyll-a coincided with the low surface fCO₂, implying that biological uptake may considerably affect the fCO₂ distribution. The net sea-to-air CO₂ flux of the study area was estimated to be 0.30±4.81 mmol m⁻² day⁻¹ in summer, 2005.     

Behavioral patterns and <Emphasis Type="Italic">in-situ</Emphasis> target strength of the hairtail (<Emphasis Type="Italic">Trichiurus lepturus</Emphasis>) via coupling of scientific echosounder and acoustic camera data

The present study focuses on the influence of target strength (TS) changes in the swimming angle of the hairtail (Trichiurus lepturus). We measured in-situ TS at 38 and 120 kHz with luring lamps at a fishing ground for jigging boats near the coastal waters of Jeju-do in Korea. Swimming angle and size of hairtails were measured using an acoustic camera. Results showed that mean preanal length was estimated to be 13.5 cm (SD = 2.7 cm) and mean swimming tilt angle was estimated to be 43.9° (SD = 17.6°). The mean TS values were ?35.7 and ?41.2 dB at 38 and 120 kHz, respectively. The results will assist in understanding the influence of swimming angle on the TS of hairtails and, thus, improve the accuracy of biomass estimates.     

Dietary shift and feeding intensity of <Emphasis Type="Italic">Stenobrachius leucopsarus</Emphasis> in the Bering Sea

The food habits of the dominant myctophid Stenobrachius leucopsarus were examined in the central basin of the Bering Sea in relation to oceanographic conditions, in summer 2002 and 2003 and spring 2006. S. leucopsarus exhibited an ontogenetic and seasonal dietary shift. In spring, small fish (≤40 mm) preyed mainly on Neocalanus flemingeri/plumchrus whereas large fish fed mainly on Neocalanus cristatus. In summer, small fish preyed mainly on Metridia pacifica whereas large fish fed mainly on euphausiids (Thysanoessa spp.). In the summer of 2003, when water temperature in the epipelagic layer (≤100 m) was warmer, reflecting the prevalence of the Alaskan Stream, small-sized S. leucopsarus showed a higher stomach content index, perhaps reflecting the greater abundance of M. pacifica. Thus, the present study shows that the physical variability in the epipelagic layer affects not only diets but also feeding performance of micronekton.     

Species diversity of the genus <Emphasis Type="Italic">Skeletonema</Emphasis> (Bacillariophyceae) in the industrial harbor Dokai Bay,Japan

Seven Skeletonema species were identified at one station in the industrial harbor Dokai Bay, Japan, in October 2007 and then monthly from January 2008 to December 2009 by morphological scanning electron microscopy observations and molecular analyses of mainly the large subunit (LSU) rDNA. We refer to one species identified as S. dohrnii using LSU rDNA, but as S. marinoi using the small subunit (SSU) rDNA and consequently we use the term S. marinoi-dohrnii complex. This is the first time that S. ardens, S. costatum s.s., and S. pseudocostatum have been recorded in Japan and that S. menzelii and S. tropicum have been identified by molecular methods in Japan. The S. marinoi-dohrnii complex was isolated with high frequency all year-round, and S. japonicum was also isolated with high frequency but not so in summer. S. Tropicum was isolated from September to December, but S. ardens and S. costatum s.s. were isolated only when the water temperature exceeded 20°C. S. pseudocostatum bloomed just once, in summer, but S. menzelii was isolated in May and again in October. The continuous year-round occurrence of S. costatum s.l. in the bay is supported by the succession of these seven species. Six of the species, except S. menzelii, were important components of algal blooms in the bay. One to four species of Skeletonema were isolated every month. Monthly species diversity was higher when S. ardens, S. costatum s.s., and S. tropicum that are usually associated with tropical or subtropical waters, were isolated. In general, species diversity of the genus Skeletonema was very high in Dokai Bay.     

Oceanological conditions and reproduction of the spotted seal (<Emphasis Type="Italic">Phoca larga</Emphasis>) in Peter the Great Bay of the Sea of Japan

The long-term studying of the reproduction of the spotted seal Phoca larga and the analysis of the oceanological conditions in Peter the Great Bay of the Sea of Japan have shown that the ice situation is not right for the successful parturition and breeding of pups due to the impossibility of synchronization of the reproduction processes with the dynamics and properties of the ice substratum. A major factor promoting the spotted seal’s coastal reproduction in this area is the existence of an archipelago of small islands with a specific geomorphological structure. Being the historical norm, the coastal reproduction has a number of advantages in comparison with ice reproduction and, as a whole, allows the existence in Peter the Great Bay of local groupings of the spotted seal with extremely small numbers of members.     

<Emphasis Type="Italic">Zostera marina</Emphasis> seed burial can be enhanced by Manila clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis>: A microcosm study

Seagrass seed bank plays a key role in the regeneration of new vegetation when seagrasses are removed by the natural or man-made disaster. Various factors may affect the development of sediment seed bank. We conducted a microcosm experiment to test the effects of burrowing and feeding activities of Manila clam, Ruditapes philippinarum on the burial of Zostera marina seeds in sediments. The effects of lasting time (3-hour, 1-day, 3-day, 7-day, 14-day and 28-day), clam density (0, 2, 4 and 8 clams with shell length of 3 cm in each microcosm) and clam size (shell length of 2, 3 and 4 cm at 4-clam density) on seed burial were examined in plastic microcosm cores (30 cm high × 10 in inner diameter) in a 28-day period. Results showed that the seed burial depth significantly increased with time, the density and the size of clams. No seeds were buried in the sediment in the cores without clams during the whole experiment period. For the 3-cm clams, about 91.61% of the seeds were buried in the sediment at the end of the experiment in the high-density treatment (8 clams at each core); while in the medium and low-density treatments (4 and 2 clams in each core, respectively), about 76.93% and 60.61% of the seeds were buried in the sediment, respectively. For the size treatments, large (4 cm) clams buried 89.56% of the seeds at the end of the experiment, much more than those of medium (3 cm, 76.93%) and small (2 cm, 61.50%) size clams. During the whole experiment period, nearly all of the buried seeds were at a depth of from 0 cm to 5 cm. These results suggested that Manila clam Ruditapes philippinarum may play an important positive role in seagrass seed bank dynamics in the field.     

Temporal changes in the geographic distribution of two clam species <Emphasis Type="Italic">Meretrix lusoria</Emphasis> and <Emphasis Type="Italic">M. petechialis</Emphasis> along the coast of Japan and South Korea

The objectives of this study were to distinguish fossil specimens of Meretrix (Bivalvia, Veneridae) using discriminant score and multivariate analysis, and to examine temporal changes in the geographical distributions of M. lusoria and M. petechialis in Japan and South Korea. Fossil shells of Meretrix were collected from Miyagi, Fukui, Aichi and Kumamoto in Japan, and Gimhae, Seosan, Siheung and Ganghwa-do in South Korea. The outside of the right valve was photographed with a digital camera, and ten characteristics of the shell morphology, such as shell height and shell length, were measured using image analysis software and a digital slide caliper. The discriminant score and multivariate analysis of the shell morphology identified all of the examined fossils as M. lusoria, while living individuals collected from the western coast of South Korea were identified as M. petechialis. These results suggest that the fossil shells excavated from the western coast of South Korea are a different species from the living individuals collected from the same areas. Radioactive carbon isotopic results revealed that the ages of the four fossil shells collected from tidal flats in Ganghwa-do ranged between 3,270 ± 30 and 1,830 ± 30 Cal BP. These results suggest that M. lusoria inhabited the western coast of South Korea until at least 2,000 years ago, but was replaced by M. petechialis during the last 2,000 years. Therefore, we propose that either M. petechialis spats were introduced artificially, or planktonic larvae migrated naturally from China to the western coast of South Korea during the last 2,000 years.