紫外线照射剂量对九孔鲍胚胎及幼虫的影响

采用不同的紫外线照射剂量的海水诱导九孔鲍产卵,观察其对卵子的受精率、畸形率和孵化率的影响.紫外线照射剂量的配制方法是:用紫外线照射过的最大剂量的海水与新鲜海水混合配制出各种剂量的海水.实验把雌亲鲍分成7组,每组20只,分别用紫外线照射剂量为0(对照组)、450、600、750、900、1 050和1 200mW.h/dm3的海水进行刺激产卵.试验重复3次.结果表明,紫外线照射剂量在1 200mW.h/dm3以内,对卵子的受精率影响不大;紫外线照射剂量在750mW.h/dm3以内,对卵子的畸形率影响不大,但在900~1 200mW.h/dm3,对卵子的畸形率影响很大;紫外线照射剂量在600mW.h/dm3以内,对卵子的孵化率没有什么影响,但在750~1 200mW.h/dm3,对卵子的孵化率影响很大.综合考虑卵子的受精率、畸形率和孵化率,九孔鲍催产的适宜的紫外线照射剂量应为450~750mW.h/dm3.     

Ecological characteristics of Walleye pollock eggs and larvae in the southeastern Bering Sea during the late 1970s

Walleye pollock (Theragra chalcogramma) is an ecologically and economically important groundfish in the eastern Bering Sea. Its population size fluctuates widely, driving and being driven by changes in other components of the ecosystem. It is becoming apparent that dramatic shifts in climate occur on a decadal scale, and these “regime shifts” strongly affect the biota. This paper examines quantitative collections of planktonic eggs and larvae of pollock from the southeastern Bering Sea during 1976–1979. Mortality, advection, and growth rates were estimated, and compared among the years encompassing the 1970s’ regime shift. These data indicate that pollock spawning starts in late February over the basin north of Bogoslof Island. Over the shelf, most spawning occurs north of Unimak Island near the 100 m isobath in early or mid April. Pollock eggs are advected to the northwest from the main spawning area at 5–10 cm/sec. Larvae are found over the basin north of Bogoslof Island in April, and over the shelf between Unimak Island and the Priblof Islands in May. Compared to 1977, the spawning period appeared to be later in 1976 (a cold year) and earlier in 1978 (a warm year) in the study area. At the lower temperatures in 1976, egg duration would be longer and thus egg mortality would operate over a longer period than in the other years. Mean larval growth appeared to be lower in 1976 than in 1977 and 1979. Estimated egg mortality rate in 1977 was 0.6 in April and 0.3 in early May.     

The contribution of atmospheric acid deposition to ocean acidification in the subtropical North Atlantic Ocean

The absorption of anthropogenic CO₂ and atmospheric deposition of acidity can both contribute to the acidification of the global ocean. Rainfall pH measurements and chemical compositions monitored on the island of Bermuda since 1980, and a long-term seawater CO₂ time-series (1983–2005) in the subtropical North Atlantic Ocean near Bermuda were used to evaluate the influence of acidic deposition on the acidification of oligotrophic waters of the North Atlantic Ocean and coastal waters of the coral reef ecosystem of Bermuda. Since the early 1980's, the average annual wet deposition of acidity at Bermuda was 15 ± 14 mmol m^− 2 year^− 1, while surface seawater pH decreased by 0.0017 ± 0.0001 pH units each year. The gradual acidification of subtropical gyre waters was primarily due to uptake of anthropogenic CO₂. We estimate that direct atmospheric acid deposition contributed 2% to the acidification of surface waters in the subtropical North Atlantic Ocean, although this value likely represents an upper limit. Acidifying deposition had negligible influence on seawater CO₂ chemistry of the Bermuda coral reef, with no evident impact on hard coral calcification.     

Microbial Biomass Dynamics Along a Trophic Gradient at the Atlantic Barrier Reef off Belize (Central America)

Abstract. Recent findings indicate that heterotrophic bacteria and not phytoplankton are the most numerous biomass components even in the euphotic zone of oligotrophic, open oceans. In this study it was hypothesized that the microbial biomass components change within a few hundred meters as oligotrophic water flows across the reef and becomes enriched with nutrients. Along a trophic gradient, four stations at the Atlantic Barrier Reef off Belize (Central America) were sampled for microbial biomass components. Phytoplankton biomass (measured as chlorophyll a) ranged from the most oligotrophic station (St. 1) to the most eutrophic station (St. 4) from 6.9–415.5 μg CI"' (assuming a C:chl a ratio of 30): heterotrophic bacterial biomass increased 4-fold (from 10.1–46.4μg C 1^-1), heterotrophic nanoflagellate (HNAN) biomass increased from 4.6-19ug C 1^-1, and cyanobacteria from 0.9-4.5 μg C-1^-1. Production estimates derived from seawater cultures revealed a 5-fold increase in bacterial production from the oligotrophic station (3.7 ug C 1^-1 d^-1) to the eutrophic St. 4 (17.8ug C-1-d1^-1)- Cyanobacterial production rose from 1.1–3.5ug C-1–d^-1 and HNAN production from 0.65-1.13 μg C-1^-1 -d^-1. While cyanobacteria contributed between 13 and 20% to the autotrophic plankton component in the oligotrophic waters, their contribution dropped to about 1 % at the eutrophic stations.