Elephant teeth from the atlantic continental shelf

Teeth of mastodons and mammoths have been recovered by fishermen from at least 40 sites on the continental shelf as deep as 120 meters. Also present are submerged shorelines, peat deposits, lagoonal shells, anz relict sands. Evidently elephants and other large mammals ranged this region during the glacial stage of low sea level of the last 25,000 years.     

Estuarine influences on a continental shelf plankton community

On the southeastern U.S. continental shelf, phytoplankton primary production and the densities of zooplankton, fish eggs, and fish larvae peak simultaneously in late summer and early fall. Some community response to irregular storm events is observed. However, the gross plankton community dynamics on this shelf are dominated by couplings with the local estuaries and shallow nearshore zone.     

Freshwater methane emissions offset the continental carbon sink

Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH(4)) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets. Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least 103 teragrams of CH(4) year(-1), corresponding to 0.65 petagrams of C as carbon dioxide (CO(2)) equivalents year(-1), offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.     

Upper wisconsinan till recovered on the continental shelf southeast of new England

Basal till was identified in two sediment cores collected about 69 kilometers southeast of Nantucket Island on the east and west sides of Great South Channel. These are the first samples of till collected on the outer continental shelf off the northeastern United States. The carbon-14 age of the total organic carbon in the tills provides a "no older than" age of about 20,000 years before present and suggests that the tills were deposited during the late Wisconsinan glaciation. This conclusion is in support of the hypothesis of an extensive Laurentide ice sheet that extended to the northern side of Georges Bank.     

Evidence for upwelling of corrosive "acidified" water onto the continental shelf

The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of approximately 40 to 120 meters along most transect lines and all the way to the surface on one transect off northern California. Although seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area.     

Holocene sea-level curves for santa monica shelf, california continental borderland

A curve is constructed showing changes in sea level at the Santa Monica shelf over the past 18,000 years. The curve is based on radiocarbon dates, sedimentologic data, and high-resolution seismic stratigraphic analysis of late Quaternary terrace deposits. Sea level was 117 meters below its present position about 18,000 years ago. During the first 8000 years of the Flandrian transgression, sea level rose to at least 24 meters, fell to about 46 meters, and then rose to 20 meters, all below present sea level. Subsequently, sea level rose more slowly and without discernible interruption to its present position.     

南海北部陆架区海域科鱼类的分布

1997年12月至1999年6月对南海北部陆架区海域进行了底拖网渔业资源调查。调查分春(4-6月)、夏(7-9月)、秋(10-12月)、冬(12-2月)4个季节,每个季节都进行全海域的大面积定点调查,共采获科鱼类31种,分隶属于11属。通过对渔获种类组成和渔获率在不同区域、不同季节、不同水深以及昼夜变化等的分析,结果表明,北部湾海区的渔获率最高,粤东海区最低,并由西往东呈逐渐递减的趋势;夏、冬季科鱼类的渔获率较高,而春、秋季较低;渔获率沿水深梯度的变化为≤100m水深海域沿水深的增加而增加,>100m水深海域随水深的增加而下降,以80～100m海域的渔获率相对较高;午夜的渔获率最低,14时最高。     

南海北部陆架区海域鯵科鱼类的分布

1997年12月至1999年6月对南海北部陆架区海域进行了底拖网渔业资源调查.调查分春(4-6月)、夏(7-9月)、秋(10-12月)、冬(12-2月)4个季节,每个季节都进行全海域的大面积定点调查,共采获鲹科鱼类31种,分隶属于11属.通过对渔获种类组成和渔获率在不同区域、不同季节、不同水深以及昼夜变化等的分析,结果表明,北部湾海区的渔获率最高,粤东海区最低,并由西往东呈逐渐递减的趋势;夏、冬季鲹科鱼类的渔获率较高,而春、秋季较低;渔获率沿水深梯度的变化为≤100m水深海域沿水深的增加而增加,＞100m水深海域随水深的增加而下降,以80～100m海域的渔获率相对较高;午夜的渔获率最低,14时最高.     

南海北部陆架区海域鯵科鱼类的分布

1997年12月至1999年6月对南海北部陆架区海域进行了底拖网渔业资源调查。调查分春(4-6月)、夏(7-9月)、秋(10-12月)、冬(12-2月)4个季节,每个季节都进行全海域的大面积定点调查,共采获科鱼类31种,分隶属于11属。通过对渔获种类组成和渔获率在不同区域、不同季节、不同水深以及昼夜变化等的分析,结果表明,北部湾海区的渔获率最高,粤东海区最低,并由西往东呈逐渐递减的趋势;夏、冬季科鱼类的渔获率较高,而春、秋季较低;渔获率沿水深梯度的变化为≤100m水深海域沿水深的增加而增加,>100m水深海域随水深的增加而下降,以80～100m海域的渔获率相对较高;午夜的渔获率最低,14时最高。     

南海北部陆架区短蛸生物学特性研究

根据2015年8-10月在南海北部陆架区渔业生产期间采集的362尾短蛸样本,对南海北部陆架区短蛸的生物学特性进行了研究。结果表明,样本的胴长范围为24~67 mm,平均胴长为43.2 mm,优势胴长组为35~50 mm,占样本总数的70.9%;样本的体质量范围为9~124 g,平均体质量为37.0 g,优势体质量组为13~52 g,占样本总数的83.8%。不同海域短蛸的胴长和体质量组成不同,北部湾海域的样本个体要小于南海北部海域。回归分析表明,短蛸的胴长与体质量的生长最适合用幂函数表示。样本的雌、雄比例为0.66∶1;不同海域的样本性腺成熟度组成不同,南海北部海域的样本以成熟个体为主,占比66.44%,而北部湾海域的个体几乎都处于未成熟阶段;样本摄食等级以0~1级为主,占样本总数的91.4%,胃含物主要以甲壳类为主。     

南海西北部陆架区鱼类的种类组成与群落格局

根据2006-2007年在南海西北部陆架区海域进行的4航次底拖网调查数据,对该海域鱼类的种类组成和群落格局进行分析.调查共采获鱼类262种,隶属于20目102科.以冬季出现种类数最多,为166种;夏季和秋季次之,分别为161种和155种;春季最少,为135种.运用聚类分析和非度量多维标度(NMDS)方法分析了南海西北部陆架区鱼类群落结构的空间分布.研究表明,该海域鱼类可划分为5个群落,分别为粤西沿岸群落(群落Ⅰ)、海南岛东南沿岸群落(群落Ⅱ)、海南岛东部深海群落(群落Ⅲ)、过渡群落(群落Ⅳ)和混合群落(群落Ⅴ).ANOSIM检验表明,各群落间鱼类组成的差异极为显著(R=0.847-0.939,P＜0.001).鱼类群落格局的变化与海流和水深关系密切,有较明显的沿水深梯度分布的规律.咸淡水鱼类在雷州半岛东部的冷涡区域,形成群落Ⅰ;南海暖流控制区域内的深海鱼类,形成群落Ⅲ;在南海暖流最为强劲的冬季,研究区域内大部分鱼类集结为混合性群落Ⅴ;琼东南沿岸的上升流区内形成群落Ⅱ;沿岸流强劲的夏、秋季,在沿岸流和上升流交汇处,形成过渡性群落Ⅳ.     

南海北部陆架区甲壳类的种类组成和资源密度分布

根据2006年-2007年南海北部陆架区4季的调查资料,分析该海区甲壳类的种类组成和资源密度的分布.结果表明,甲壳类有99种,分隶于2目22科46属,其中虾类32种,蟹类51种,虾蛄类16种;以热带和亚热带暖水性种类为主,属于印度-西太平洋区系.优势种为口虾蛄、黑斑口虾蛄、红星梭子蟹、锈斑蟳、银光棱子蟹、逍遥馒头蟹、猛虾蛄、宽突赤虾、武士蟳、香港蟳、长叉口虾蛄;渔获率B断面最高(7.94 kg/h),C断面最低(4.94 kg/h);渔获率有明显的季节变动,秋季最高(10.31 kg/h),冬季最低(4.05 kg/h);平均渔获率为6.54 kg/h,其中:虾类渔获率0.88 kg/h,占13.46%,蟹类渔获率3.68 kg/h,占56.27%,虾蛄类渔获率1.98 kg/h,占30.27%;甲壳类60 m以浅水域分布较多,并密集分布于10～20 m水深处;平均资源密度为87.20 kg/km2,资源密度秋季最高(137.47 kg/km2),冬季最低(54.00 kg/km2).     

南海北部陆架区蟹类的种类组成和数量分布

根据2006—2007年南海北部陆架区4个季节的调查资料,分析了该海区蟹类的种类组成和数量分布状况。结果表明:南海北部陆架区共有蟹类51种,隶属于10科24属,以热带暖水性种类为主,属于印度洋—西太平洋区系中的南中国—东南亚海区;这些蟹类可分为3个生态类群———高温广盐生态类群、广温广盐生态类群和高温高盐生态类群;依据P inkas判定,优势种为银光梭子蟹、红星梭子蟹、锈斑蟳、香港蟳、逍遥馒头蟹、武士蟳、直额蟳、威迪梭子蟹;优势种类渔获率(2.99 kg/h)占蟹类总渔获率(3.66kg/h)的81.69%;经济蟹类为红星梭子蟹、锈斑蟳、武士蟳、三疣梭子蟹、日本蟳、拥剑梭子蟹、远海梭子蟹,均属梭子蟹科种类,经济种类渔获率(2.37 kg/h)占蟹类总渔获率(3.66 kg/h)的64.75%;蟹类资源密度为97.47 kg/km2,经济蟹类资源密度为63.20 kg/km2。蟹类资源密度区域分布以D断面最高(125.60 kg/km2),C断面最低(70.93 kg/km2);蟹类资源密度季节分布以秋季最高(181.60 kg/km2),冬季最低(50.13 kg/km2)。蟹类密集区为10⁶0 m深水域,尤以10 m深附近水域分布最多,达222.13kg/km2,其数量分布趋势大致与水深呈负相关。     

南海北部陆架区蟹类的种类组成和数量分布

根据2006--2007年南海北部陆架区4个季节的调查资料,分析了该海区蟹类的种类组成和数量分布状况。结果表明：南海北部陆架区共有蟹类51种,隶属于10科24属,以热带暖水性种类为主,属于印度洋一西太平洋区系中的南中国一东南亚海区;这些蟹类可分为3个生态类群——高温广盐生态类群、广温广盐生态类群和高温高盐生态类群;依据Pinkas判定,优势种为银光梭子蟹、红星梭子蟹、锈斑蝎、香港婚、逍遥馒头蟹、武士蜉、直额蟳、威迪梭子蟹;优势种类渔获率（2．99kg／h）占蟹类总渔获率（3．66kg／h）的81．69％;经济蟹类为红星梭子蟹、锈斑蜉、武士蝎、三疣梭子蟹、日本蝇、拥剑梭子蟹、远海梭子蟹,均属梭子蟹科种类,经济种类渔获率（2．37kg／h）占蟹类总渔获率（3．66kg／h）的64．75％;蟹类资源密度为97．47kg／km^2,经济蟹类资源密度为63．20kg／km^2。蟹类资源密度区域分布以D断面最高（125．60kg／km^2）,C断面最低（70．93kg／km^2）;蟹类资源密度季节分布以秋季最高（181．60kg／km2）,冬季最低（50．13kg／km^2）。蟹类密集区为10-60m深水域,尤以10m深附近水域分布最多,达222．13kg／km。,其数量分布趋势大致与水深呈负相关。