Salinity tolerances of 62 strains of Pflesteria and Pfiesteria-like heterotrophic flagellates (Dinophyceae)

The salinity tolerance of 62 strains of Pfiesteria and Pfiesteria‐like heterotrophic dinoflagellates was measured. All strains were acclimated at 12 psu for at least 1 year before experimentation. Strains isolated from the Chesapeake Bay and Neuse River systems tolerated lower salinities than strains isolated from the Wilmington River system (P< 0.005). Swimming cells were still observed after 5 days at 0.5 psu for one strain, and at 1 psu for most other Chesapeake Bay and Neuse River strains. Swimming cells for the Wilmington River were still observed after 5 days at 3–5 psu, but no swimming cells were observed at ≤ 2 psu. With regard to the upper salinity tolerance, the Wilmington River strains tolerated higher salinities than the Chesapeake Bay and Neuse River systems (P< 0.005). Most Wilmington River strains were swimming after 5 days at salinities ≥ 50 psu, whereas the Chesapeake Bay and Neuse River system strains rarely had swimming cells at salinities exceeding 35–45 psu. For all three water systems and for both lower and higher salinities, cells apparently encysted in many instances. However, when salinities were returned to 12 psu, swimming cells often re‐appeared. Statistically significant geographic differences in salinity tolerance suggest a geographic adaptation has occurred and that salinity tolerance is under genetic control. The results also suggest there is diversity among the strains.     

Factors influencing swimming in bay scallops, Argopectenirradians (Lamarck, 1819)

Factors influencing the probability, distance, and direction of swimming in bay scallops (Argopectenirradions Lamarck, 1819) were studied through a series of experimental releases in the field and in a 3-m tank. The probability of a scallop swimming was significantly influenced by the type of substratum on which it was released (sand vs. grassbed), by contact with two natural gastropod predators (Murex, Fasciolaria), and by the amount of rest allowed after a previous swim. The horizontal distance traveled by a swimming scallop was significantly influenced by artificial weight of a magnitude equivalent to a normal load of shell-encrusting organisms, by the amount of rest allowed after a previous swim, by the height attained in the water column, and by the scallop's size. The direction of scallop swimming was significantly influenced by the location along the mantle edge where a predator was contacted, and by factors probably related to the asymmetrical water flow pattern through the mantle cavity. Swimming in bay scallops apparently serves to maintain position in grassbeds and to avoid predators.     

DECLINES IN HARBOR SEAL (PHOCA VITULINA) NUMBERS IN GLACIER BAY NATIONAL PARK, ALASKA, 1992–2002

Glacier Bay National Park had one of the largest breeding aggregations of harbor seals in Alaska, and it is functionally the only marine reserve for harbor seals in Alaska; yet, numbers of seals in the Bay are declining rapidly. Understanding why seals in Glacier Bay are declining may clarify their minimal habitat needs. We estimated population trends using models that controlled for environmental and observer‐related factors. In 1992, 6,200 seals were counted on icebergs in a tidewater glacial fjord and at terrestrial sites; by 2002 only 2,550 seals were counted at these same haul‐outs. Numbers of non‐pups in the glacial fjord declined by 6.6%/yr (?39%/8 yr) in June and by 9.6%/yr (?63%/11 yr) in August and at all other haul‐outs by 14.5%/yr (?75%/10 yr) during August. In the glacial fjord the number of pups remained steady from 1994 to 1999 and made up an increasing proportion of seals counted (5.4%/yr), and the proportion of pups peaked at 34%–36%. The rapid declines do not appear to be due to changes in seal behavior or redistribution. The declines reinforce genetic evidence that harbor seals in Glacier Bay are demographically isolated from other populations and indicate that current management stocks need to be redefined. Changes in Glacier Bay's ecosystem and population demographic data from the glacial fjord suggest that interspecific competition and predation are likely factors in the declines.     

REPRODUCTIVE LONGEVITY OF DRIFTING KELP MACROCYSTIS PYRIFERA (PHAEOPHYCEAE) IN MONTEREY BAY,USA1

Drifting Macrocystis pyrifera (L.) C. Agardh sporophytes have long been viewed as the primary long‐distance dispersal vector; yet, few data exist that support the ability of reproductive viable sporophytes to actually travel the presumed hundreds to thousands of kilometers. This study addressed the reproductive longevity of experimental and naturally occurring M. pyrifera drifters. Temporal variability in sporophyte size and reproduction was estimated for experimental drifting sporophytes that were tethered to surface buoys and compared with attached plants (controls). Reproductive viability was also studied for beach‐cast drifters (BCD), and naturally drifting sporophytes observed during field surveys in Monterey Bay. Detached drifting sporophytes were tracked with radio transmitters to follow drifter trajectories and to measure drifting speed. Experimental drifters (ED) experienced a 74% reduction in frond length after 35 days, a 76% reduction in average frond number after 70 days, and a reduction in average sorus area by 83% after 28 days. Although zoospore production was reduced following detachment, sporophytes remained fertile with high zoospore germination success as long as sori were present (125 days). Zoospore production and germination success for natural and BCD was similar to ED. The average displacement of radio‐tagged drifters was 7.12 km·day^?1, suggesting that a sporophyte adrift for 125 days disperses viable propagules (zoospores) over 890 km (±363). Dispersal of propagules is important for population restoration, distribution, and genetic diversity. Such dispersal distances are long enough to connect potentially all Northern Hemisphere Macrocystis populations across a generational timescale and may facilitate inter‐hemispheric gene flow.     

Juvenile sockeye salmon distribution, size, condition and diet during years with warm and cool spring sea temperatures along the eastern Bering Sea shelf

Interannual variations in distribution, size, indices of feeding and condition of juvenile Bristol Bay sockeye salmon Oncorhynchus nerka collected in August to September (2000–2003) during Bering–Aleutian Salmon International Surveys were examined to test possible mechanisms influencing their early marine growth and survival. Juvenile sockeye salmon were mainly distributed within the southern region of the eastern Bering Sea, south of 57°0' N during 2000 and 2001 and farther offshore, south of 58°0' N during 2002 and 2003. In general, juvenile sockeye salmon were significantly larger ( P < 0·05) and had significantly higher indices of condition ( P < 0·05) during 2002 and 2003 than during 2000 and 2001. The feeding index was generally higher for age 1.0 year sockeye salmon than age 2.0 year during all years. Among-year comparisons suggested that Pacific sand lance Ammodytes hexapterus were important components of the juvenile sockeye salmon diet during 2000 and 2001 (20 to 50% of the mean wet mass) and age 0 year walleye pollock Theragra chalcogramma were important components during 2002 and 2003 (50 to 60% of the mean wet mass). Warmer sea temperatures during spring and summer of 2002 and 2003 probably increased productivity on the eastern Bering Sea shelf, enhancing juvenile sockeye salmon growth.     

Woody Debris in the Mangrove Forests of South Florida1

Woody debris is abundant in hurricane‐impacted forests. With a major hurricane affecting South Florida mangroves approximately every 20 yr, carbon storage and nutrient retention may be influenced greatly by woody debris dynamics. In addition, woody debris can influence seedling regeneration in mangrove swamps by trapping propagules and enhancing seedling growth potential. Here, we report on line‐intercept woody debris surveys conducted in mangrove wetlands of South Florida 9–10 yr after the passage of Hurricane Andrew. The total volume of woody debris for all sites combined was estimated at 67 m³/ha and varied from 13 to 181 m³/ha depending upon differences in forest height, proximity to the storm, and maximum estimated wind velocities. Large volumes of woody debris were found in the eyewall region of the hurricane, with a volume of 132 m³/ha and a projected woody debris biomass of approximately 36 t/ha. Approximately half of the woody debris biomass averaged across all sites was associated as small twigs and branches (fine woody debris), since coarse woody debris >7.5 cm felled during Hurricane Andrew was fairly well decomposed. Much of the small debris is likely to be associated with post‐hurricane forest dynamics. Hurricanes are responsible for large amounts of damage to mangrove ecosystems, and components of associated downed wood may provide a relative index of disturbance for mangrove forests. Here, we suggest that a fine:coarse woody debris ratio ≤0.5 is suggestive of a recent disturbance in mangrove wetlands, although additional research is needed to corroborate such findings.     

莱州湾三疣梭子蟹的生物学特征、时空分布及环境因子的影响

根据2011年5月—2012年4月进行的9个航次(月份)的底拖网调查,研究了莱州湾水域三疣梭子蟹的生物学特征、数量分布以及环境因子的影响.结果表明: 莱州湾三疣梭子蟹生物量密度的月间排序为9月>10月>7月>8月>6月>11月>3月>5月>4月.其中1龄以下个体占绝对优势,2011年7—10月4个航次所占比例平均值为86.1%.9个航次中,三疣梭子蟹的体质量、头胸甲宽及头胸甲长的平均值均以8月最高、4月最低.7—11月,雌、雄个体肥满度均以8月最高,分别为1.030和1.023,7月最低,雌雄均为1.007;雌雄个体肥满度的性别差异不显著.除6—8月外,其他月份性比(雌/雄)均小于1.0.莱州湾三疣梭子蟹5—7月主要集中在黄河口、龙口近岸,8—9月以潍坊及龙口近海密度最高,11月至翌年4月主要集中在湾口深水区.Pearson相关分析表明,莱州湾三疣梭子蟹数量分布与表层水温、溶解氧和水深的相关性最高,其次为盐度和浮游动物密度,与浮游植物密度及其他底层渔业生物个体数的相关性最低.与1981年同期对比,2011年莱州湾三疣梭子蟹的头胸甲长显著降低.建议适当降低捕捞强度,提高捕捞规格,进一步加强三疣梭子蟹增殖基础的研究,提出更加合理的增殖放流数量,以利于三疣梭子蟹资源的可持续利用.     

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.     

Primary cultures of heart cells from the scallp Pecten maximus (mollusca-bivalvia)

Summary Primary cultures of Pecten maximus heart cells, isolated by an enzymatic procedure, were routinely obtained with a high level of reproducibility in a simple medium based on sterile seawater. Cells attached to the plastic substratum without the need to add a special factor. The number of adhering cells gradually increased with the time of culture. Two types of adhering cells were observed: epitheliallike cells and fibroblastlike cells, which were more numerous. The latter cells were identified as myocytes by electron microscopy and immunofluorescent staining. Results obtained by autoradiography, after incorporation of [¹⁴C]leucine, [³H]thymidine, and [¹⁴C]acetate, confirmed functional activity of the cells. These cultures were maintained viable in vitro during at least 1 mo.