Palio dubia (Nudibranchia: Doridina) from the north-west Atlantic Ocean: is its morphology at hatching consistent with settlement one day later?

2010 ◽  
Vol 91 (8) ◽  
pp. 1651-1654 ◽  
Author(s):  
Jeffrey H.R. Goddard
Keyword(s):  
Embryonic Development ◽  
Atlantic Ocean ◽  
Larval Period ◽  
North West ◽  
The North ◽  
Order Of Magnitude ◽  
Size And Morphology ◽  
Mode Of Development ◽  
Veliger Larvae

Hamel et al. (2008) reported that veliger larvae of the nudibranch gastropod Palio dubia settled 1 to 3 days after hatching and that metamorphosis commenced shortly thereafter. This is an anomalously short larval period for a nudibranch described as having planktotrophic development. I examined the embryonic development and hatching larvae of P. dubia collected intertidally from Maine, USA. Veliger larvae with shells 120 μm long and lacking eyespots and propodia developed in 7 days at 20°C from eggs averaging 69 μm in diameter. Their size and morphology were typical of planktotrophic nudibranchs known to have minimum larval periods of weeks to months, and the available evidence does not suggest any other mode of development exists in P. dubia. The larval period of P. dubia is likely an order of magnitude longer than reported by Hamel et al. (2008).

Subtidal Rocky Shores of the North-West Atlantic Ocean

2019 ◽  
pp. 90-127
Author(s):  
Ladd E. Johnson ◽  
Kathleen A. MacGregor ◽  
Carla A. Narvaez ◽  
Thew S. Suskiewicz
Keyword(s):  
Atlantic Ocean ◽  
Rocky Shores ◽  
North West ◽  
The North

WIRELINE FORMATION-TESTER PERFORMANCE ON THE NORTH WEST SHELF

1975 ◽  
Vol 15 (1) ◽  
pp. 127
Author(s):  
M. D. Agostini
Keyword(s):  
Single Point ◽  
Test Method ◽  
Reservoir Rock ◽  
Relative Reduction ◽  
Well Testing ◽  
North West ◽  
Drill Stem ◽  
The North ◽  
Order Of Magnitude ◽  
Time Required

The formation-interval-tester was introduced to the North West Shelf in December, 1970 Originally it was used as a first-look test method, with drill stem testing retained as the standard evaluation technique in all potential reservoir sections. Systematic use of this technique in parallel with drill-stem testing has allowed the accumulation of a significant volume of comparative data. This has provided a unique opportunity to examine the validity of wireline-testing as an alternative to the more traditional method of reservoir evaluation.The wireline-tester has been found to be a reliable indicator of movable hydrocarbons in reservoir rock, after experience allowed the development of regional interpretation limits. Such variables as gas:oil ratios and oil gravities are determined within acceptable limits of accuracy. Formation pressure determinations are consistent' and are thought to be more reliable than those derived from drill-stem-testing. With the data available it is normally possible to calculate the indicated formation permeability. This however being a single point determination the result is of questionable value. Experience has shown that "order of magnitude" agreement is normally achieved between wireline-tester permeabilities and those determined from drill-stem-testing in the same interval.The reduction in cost resulting from the application of this technique is particularly significant. Savings may be related directly to the relative reduction in rig time required by this operation compared with that required for drill-stem-testing. As the cost of offshore operations increases rapidly the resultant savings will grow in significance.Also of concern in all well-testing operations is the risk to which the rig and personnel are subjected. On floating offshore rigs the flowing well condition required by drill-stem-testing requires the acceptance of certain associated risks. Wireline testing is by comparison a risk-free operation.The recognition of the inherent limits of this approach to well testing is important if satisfactory results are to be achieved. Where the required reservoir parameters are those that can be satisfactorily determined with the wireline tester it offers a real alternative to the more traditional evaluation techniques.

Shallow Water Muddy Sands of the North-West Atlantic Ocean

2019 ◽  
pp. 128-163
Author(s):  
Sarah A. Woodin ◽  
Susan S. Bell ◽  
Jon Grant ◽  
Paul V. R. Snelgrove ◽  
David S. Wethey
Keyword(s):  
Atlantic Ocean ◽  
Shallow Water ◽  
North West ◽  
The North

Age and growth of the scalloped hammerhead shark, Sphyrna lewini, in the north-west Atlantic Ocean and Gulf of Mexico

2007 ◽  
Vol 58 (1) ◽  
pp. 34 ◽  
Author(s):  
Andrew N. Piercy ◽  
John K. Carlson ◽  
James A. Sulikowski ◽  
George H. Burgess
Keyword(s):  
Atlantic Ocean ◽  
Gulf Of Mexico ◽  
Growth Parameters ◽  
Fork Length ◽  
Age And Growth ◽  
North West ◽  
Scalloped Hammerhead ◽  
The North ◽  
The Usa ◽  
Cent Error

The scalloped hammerhead, Sphryna lewini (Griffith & Smith, 1834), is a globally exploited species of shark. In order to gain insight into the life history of this species in the USA waters, age and growth was examined from specimens (n = 307) captured from the north-west Atlantic Ocean and from the Gulf of Mexico. The von Bertalanffy growth model resulted in growth parameters of L∞ = 214.8 cm fork length (FL), k = 0.13 year–1, t0 = –1.62 year for males and L∞ = 233.1 cm FL, k = 0.09 year–1, t0 = –2.22 year for females. The oldest age estimates obtained for this population were 30.5 years for both males and females, which corresponded to FL of 234 cm and 241 cm respectively. Bowker’s test of symmetry and Index of Average Per Cent Error suggests that our ageing method represents a non-biased and precise approach to the age assessment. Marginal increments were significantly different between months (Kruskal–Wallis P = 0.017) with a distinct trend of increasing monthly increment growth beginning in January. When compared to previously published studies, our growth estimates suggest slower growth than populations in the Pacific Ocean but faster growth than previously reported in the Gulf of Mexico.

New insights into North Sea tunnel valley infill and genesis from high-resolution 3D seismic data

2020 ◽  
Author(s):  
James Kirkham ◽  
Kelly Hogan ◽  
Robert Larter ◽  
Ed Self ◽  
Ken Games ◽  
...  
Keyword(s):  
High Resolution ◽  
North Sea ◽  
Seismic Data ◽  
3D Seismic ◽  
Seismic Reflection Data ◽  
North West ◽  
The North ◽  
Reflection Data ◽  
Order Of Magnitude ◽  
Subglacial Meltwater

<p>Tunnel valleys are large (kilometres wide, hundreds of metres deep) channels incised into bedrock and soft sediments by the action of pressurised subglacial meltwater. Discovered over a century ago, they are common across large swathes of North-West Europe and North America. However, many aspects of tunnel valley formation, and the processes by which they are infilled, remain poorly understood. Here, we use new high-resolution 3D seismic reflection data, collected by the geohazard assessment industry, to examine the infill lithology and architecture of buried tunnel valleys located in the central North Sea. The spatial resolution of our seismic data (3.125-6.25 m bin size) represents an order of magnitude improvement in the data resolution that has previously been used to study tunnel valleys in this region, allowing us to examine their infill in unprecedented detail. Inside the tunnel valleys, we identify a suite of buried subglacial landforms, some of which have rarely been reported inside tunnel valleys before. These landforms include a 14-km-long system of segmented eskers, crevasse-squeeze ridges, subsidiary meltwater channels and retreat moraines. Their presence suggests that, in some cases, tunnel valleys in the North Sea were reoccupied by ice following their initial formation, casting doubt on hypotheses which invoke catastrophic releases of water to explain tunnel valley creation.</p>

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