The “Grey Area” in the Northern Bay of Bengal: A Note on a Functional Cooperative Solution

The judgments in maritime delimitation cases involving Bangladesh and Myanmar (2012) and between Bangladesh and India (2014) have resulted in a “Grey Area” in the northern Bay of Bengal involving intersecting and overlapping rights and responsibilities in terms of the exclusive economic zone (EEZ) and continental shelf regimes. This article seeks to identify a functional solution for this Grey Area.     

Gap Dynamics in a Seagrass Landscape

We investigated gap dynamics within a shallow subtidal landscape characterized by seagrass vegetation and examined the relationship between gap formation and selected physical factors. The study was conducted over 2 y by using a biannual mapping of seagrass and water depth across an 48,800-m² area in Tampa Bay, Florida. In addition, monthly sediment deposition or erosion was recorded at 96 locations within the landscape. Gaps represented from 2.4% to 5.7% of the seagrass landscape, and all were within monospecific stands of Halodule wrightii. Gaps ranged in size from 10 to 305 m² and most frequently decreased in size over time. Most gaps were small and short lived (less than 6-mo duration), but the second age group most frequently recorded was at least 1.5 y old. No new species of seagrass invaded the gaps with Halodule replacing itself 100% of the time. Gaps were recorded over the entire range of water depths within the landscape. Neither gap area nor persistence of gaps was related to water depth. However gap area was associated positively with the number of extreme sedimentation events. Gaps originated not only from removal of interior vegetation (similar to classic gaps) but also from differential growth of the seagrass margin (similar to edaphic gaps). Distinct seasonal components to the mode of formation were detected with interior-produced gaps originating primarily in the winter and margin gaps most commonly during summer. These results combine to illustrate the importance of large-scale studies with fine-scale resolution for deciphering unique features of seagrass landscape dynamics. Our historical information suggests that a static enumeration of gaps may not provide an accurate assessment of disturbance intensity in this system, and the seagrass mosaic probably is explained best by a combination of disturbance regimes and edaphic factors, such as sediment stability. Moreover, we suggest that even in areas characterized by monospecific stands of vegetation and over short or moderate time periods, gaps indirectly may influence community structure and ecosystem function via modification of habitat arrangement. Received 17 September 1998; accepted 26 April 1999.     

Evidence that the parasitic nematode Skrjabinoclava manipulates host Corophium behavior to increase transmission to the sandpiper, Calidris pusilla

We found evidence that a nematode (Skrjabinoclava morrisoni) adaptivelymanipulates the behavior of its intermediate host (the amphipod Corophiumvolutator) to increase its likelihood of transmission to itsfinal host (the semipalmated sandpiper, Calidris pusilla). We foundthat male and female amphipods parasitized by nematodes increasedtheir surface activity in the field during daytime, but notduring nighttime hours. Increased surface activity is knownto increase susceptibility of amphipods to predation by sandpipersduring the day, but not at night, when sandpipers do not feedvisually. Also, as predicted by the manipulation hypothesis,only late-stage (infective) larvae of nematodes were associatedwith behavioral changes of amphipods. We found no evidence thatparasites were associated with other amphipod behaviors in thelaboratory, such as trail complexity, distance traveled, orburrow-probing activity of crawling males as would be expectedif parasitized hosts altered their own behavior. Survivorshipof amphipods was also unaffected by parasitism, which may favorparasite transmission. Thus, behavioral changes of parasitizedhosts were simple, and their expression was context-dependentand related to likelihood of predation. We argue that maturationtimes of nematodes in relation to migration schedules of sandpipers providea narrow window of opportunity and may explain why nematodes manipulateamphipod behavior.     

Variation in growth rate,carbon assimilation,and photosynthetic efficiency in response to nitrogen source and concentration in phytoplankton isolated from upper San Francisco Bay

Six species of phytoplankton recently isolated from upper San Francisco Bay were tested for their sensitivity to growth inhibition by ammonium (NH₄⁺), and for differences in growth rates according to inorganic nitrogen (N) growth source. The quantum yield of photosystem II (F_v/F_m) was a sensitive indicator of NH₄⁺ toxicity, manifested by a suppression of F_v/F_m in a dose‐dependent manner. Two chlorophytes were the least sensitive to NH₄⁺ inhibition, at concentrations of >3,000 μmoles NH₄⁺ · L^?1, followed by two estuarine diatoms that were sensitive at concentrations >1,000 μmoles NH₄⁺ · L^?1, followed lastly by two freshwater diatoms that were sensitive at concentrations between 200 and 500 μmoles NH₄⁺ · L^?1. At non‐inhibiting concentrations of NH₄⁺, the freshwater diatom species grew fastest, followed by the estuarine diatoms, while the chlorophytes grew slowest. Variations in growth rates with N source did not follow taxonomic divisions. Of the two chlorophytes, one grew significantly faster on nitrate (NO₃^?), whereas the other grew significantly faster on NH₄⁺. All four diatoms tested grew faster on NH₄⁺ compared with NO₃^?. We showed that in cases where growth rates were faster on NH₄⁺ than they were on NO₃^?, the difference was not larger for chlorophytes compared with diatoms. This holds true for comparisons across a number of culture investigations suggesting that diatoms as a group will not be at a competitive disadvantage under natural conditions when NH₄⁺ dominates the total N pool and they will also not have a growth advantage when NO₃^? is dominant, as long as N concentrations are sufficient.     

青岛崂山湾人工鱼礁区底层游泳动物群落结构特征

基于2015年5月至2016年1月在青岛崂山湾人工鱼礁区的调查数据, 采用Margalef种类丰富度指数(d)、Shannon-Wiener多样性指数(H')、Pielou均匀度指数(J)、丰度/生物量曲线、等级聚类分析、SIMPER相似性百分比分析和非度量多维尺度排序(NMDS)分析, 对底层游泳动物群落结构和多样性进行研究。调查期间共捕获游泳动物61种, 隶属34科, 其中鱼类36种, 甲壳类22种, 头足类3种。优势种为日本蟳(Charybdis japonica)、许氏平鲉(Sebastes schlegelii)、大泷六线鱼(Hexagrammus otakii)、斑头鱼(H. agrammus)和星康吉鳗(Conger myriaster), 其中日本蟳(26.91%)和许氏平鲉(26.74%)的生物量占绝对优势。礁区游泳动物的渔获量和渔获种类数均多于对照区, 月平均单位捕捞努力量渔获量(CPUE)最高值出现在5月, 达到735.74 ± 316.59 g·net^-1·d^-1。游泳动物群落组成的特征值上, 7、8月的多样性指数较高, 但鱼礁区和对照区无显著差异(P>0.05)。丰度/生物量曲线表明, 5、6月游泳动物群落处于严重受干扰状态, 11月和次年1月群落处于相对稳定状态。聚类分析表明, 除1月外, 各月份不同区域的样方相似性都较高, 5、6月三亩前礁区的相似性最高, 达到86.21%。     

Morphological variation and phylogenetic analysis of the dinoflagellate Gymnodinium aureolum from a tributary of Chesapeake Bay

Cultures of four strains of the dinoflagellate Gymnodinium aureolum (Hulburt) G. Hansen were established from the Elizabeth River, a tidal tributary of the Chesapeake Bay, USA. Light microscopy, scanning electron microscopy, nuclear-encoded large sub-unit rDNA sequencing, and culturing observations were conducted to further characterize this species. Observations of morphology included: a multiple structured apical groove; a peduncle located between the emerging points of the two flagella; pentagonal and hexagonal vesicles on the amphiesma; production and germination of resting cysts; variation in the location of the nucleus within the center of the cell; a longitudinal ventral concavity; and considerable variation in cell width/length and overall cell size. A fish bioassay using juvenile sheepshead minnows detected no ichthyotoxicity from any of the strains over a 48-h period. Molecular analysis confirmed the dinoflagellate was conspecific with G. aureolum strains from around the world, and formed a cluster along with several other Gymnodinium species. Morphological evidence suggests that further research is necessary to examine the relationship between G. aureolum and a possibly closely related species Gymnodinium maguelonnense.     

MIS3阶段以来黄骅北部地区潮坪地层中的微体生物群

依据渤海湾湾顶南侧、古黄河三角洲河北省黄骅市北部地区13个钻孔岩芯材料微体古生物学研究,以及地球化学背景、沉积构造分析,本文确定了自相当海洋氧同位素MIS3阶段以来中潮坪、高潮坪、淡水注入的潮坪、潮汐通道、分支河道及边滩、牛轭湖、贫营养湖、滨海湿地与富营养湖、泛滥平原一泛滥盆地等不同沉积地层中的微体生物(有孔虫、海相与非海相介形类)分布特征.在MIS3阶段高潮坪一低地沉积之后,河口与相邻低地依然持续或断续出现海相微体生物,个别钻孔中其分布甚至延续到末次盛冰期低海面地层中,但是基本都是广盐种和低盐种.这一现象与沿海构造沉降背景下河口位置长期向陆迁移,微体生物随短暂的强潮及突发的风暴潮搬运、甚至与风、水和鸟的搬运作用有关;远离古河道地点则无此现象.这些海侵事件与全球海面变化和古海面高度无关.与渤海湾顶北侧天津沿海相比,黄骅北部未见天津沿海确定的全新世早期潮下带砂质沉积单元,以及相应的微体生物群,应与当时天津沿海构造沉降速率较高有关.在三角洲与潮坪研究中,微体古生物学发挥了重要作用,而不仅是记述内容之一.     

Do sturgeon limit burrowing shrimp populations in Pacific Northwest Estuaries?

Green sturgeon, Acipenser medirostris, and white sturgeon, Acipenser transmontanus, are frequent inhabitants of coastal estuaries from northern California, USA to British Columbia, Canada. An analysis of stomach contents from 95 green sturgeon and six white sturgeon commercially landed in Willapa Bay, Grays Harbor, and the Columbia River estuary during 2000–2005 revealed that 17–97% had empty stomachs, but those fish with items in their guts fed predominantly on benthic prey items and fish. Burrowing thalassinid shrimp (mostly Neotrypaea californiensis) were important food items for both white and especially for green sturgeon taken in Willapa Bay, Washington during summer 2003, where they represented 51% of the biomass ingested (84.9% IRI). Small pits observed in intertidal areas dominated by these shrimp, are likely made by these sturgeon and we present evidence from exclusion studies and field observation that the predator making the pits can have a significant cumulative negative effect on burrowing shrimp density. These burrowing shrimp present a threat to the aquaculture industry in Washington State due to their ability to de-stabilize the substrate on which shellfish are grown. Despite an active burrowing shrimp control program in these estuaries, it seems unlikely that current burrowing shrimp abundance and availability as food is a limiting factor for threatened green sturgeon stocks. However, these large predators may have performed an important top down control function on shrimp populations in the past when they were more abundant.     

Movements of narwhals (<Emphasis Type="Italic">Monodon monoceros</Emphasis>) from Admiralty Inlet monitored by satellite telemetry

Twenty-one narwhals tagged in 2003 and 2004 in Admiralty Inlet showed a different summer distributional pattern than previous narwhal-tracking studies from Somerset Island, Eclipse Sound and Melville Bay. The migration of the narwhals tracked from Admiralty Inlet moved out through Lancaster Sound 15 days earlier (P < 0.0001) than the narwhals summering around Eclipse Sound, whereas the Admiralty Inlet narwhals reached the mouths of Eclipse Sound 18 days later (P < 0.0001) than the Eclipse Sound summering population. The winter range of the Admiralty Inlet narwhals overlapped with the winter range of narwhals from Melville Bay and Eclipse Sound in central southern Baffin Bay and Northern Davis Strait, but not with the winter range of narwhals from Somerset Island that wintered further north. Distribution size of range, and population size did not appear to be related. An example of considerable year to year variation between area of summer and winter distribution in the 2 years was believed to be related to the sample size and number of pods of whales tagged, rather than to differences in sex or age classes.     

Reproductive biology of the guitarfish <Emphasis Type="Italic">Rhinobatos hynnicephalus</Emphasis> (Batoidea: Rhinobatidae) in Ariake Bay,Japan

Size at sexual maturity, reproductive cycle, and fecundity of the guitarfish, Rhinobatos hynnicephalus, were examined in Ariake Bay, Japan. Females reached sexual maturity at a larger size than males [total length (TL) at 50% sexual maturity: males, 431 mm; females, 476 mm]. Monthly gonadosomatic indices of males decreased abruptly from July to August. Histological examinations confirmed the presence of mature spermatozoa in the testes in July, with semen in seminal vesicles in July and August. Preovulatory ova were observed in females with near-term embryos in August. Parturition occurred in August, immediately followed by mating, ovulation, and fertilization. Gestation period is approximately 1 year. Fertilized uterine eggs without embryonic development were present throughout the annual reproductive cycle. Embryonic development began in June and ended in August, indicating that R. hynnicephalus undergoes embryonic diapause (9 months). Fecundity increased with TL and ranged from 1 to 9 (mean, 4.4) embryos per litter.