A TAXONOMIC STUDY OF THE GENUS HEDOPHYLLUM SETCHELL

1965 ◽  
Vol 43 (11) ◽  
pp. 1409-1420 ◽  
Author(s):  
Thomas B. Widdowson
Keyword(s):  
Type Species ◽  
Gulf Of Alaska ◽  
Taxonomic Study ◽  
Field Observations ◽  
Northeast Pacific ◽  
Mechanical Effects ◽  
Juan De Fuca ◽  
Variable Species ◽  
Morphological Differences ◽  
Juan De Fuca Strait

The genus Hedophyllum Setchell consists of one variable species, H. sessile (C. Ag.) Setchell. Field observations and experiments show that H. subsessile Setchell was based upon a form characteristic of the type species in the second summer of its life. H. spirale Yendo is reduced to synonymy with Laminaria bongardiana P. et R., and H. kuroshioense Segawa is transferred to the genus Laminaria.Observations of the genus in the field throughout most of its range in the northeast Pacific indicate morphological differences between populations in the areas east and west of Yakutat, in the Gulf of Alaska. These differences appear to be related to sea temperature.Morphological variations in populations of Hedophyllum studied along Juan de Fuca Strait appear to be caused by exposure to sunlight and the mechanical effects of wave action.

A near-ridge origin for seamounts at the southern terminus of the Pratt-Welker Seamount Chain, northeast Pacific Ocean

1999 ◽  
Vol 36 (6) ◽  
pp. 1021-1031 ◽  
Author(s):  
Brian Cousens ◽  
Jarda Dostal ◽  
T S Hamilton
Keyword(s):  
Gulf Of Alaska ◽  
Trace Element Composition ◽  
Primitive Mantle ◽  
Sea Floor ◽  
Northeast Pacific ◽  
Mid Ocean Ridge ◽  
Mantle Sources ◽  
Juan De Fuca ◽  
Seamount Chain ◽  
Ocean Ridge

Three seamounts close to the south end of the Pratt-Welker Seamount Chain, Gulf of Alaska, have been sampled to test whether or not mantle plume-related volcanism extends south of Bowie Seamount. Lavas recovered from Oshawa, Drifters, and Graham seamounts are weathered, Mn-encrusted pillow lavas and sheet-flow fragments, commonly with glassy rims. The glasses and holocrystalline rocks are tholeiitic basalts, with light rare earth element depleted to flat primitive mantle normalized incompatible element patterns and radiogenic isotope compositions within the ranges of mid-ocean ridge and near-ridge seamount basalts from the Explorer and northern Juan de Fuca ridges. Chemically, the seamount lavas strongly resemble older, "shield-phase" tholeiitic rocks dredged from the flanks of southern Pratt-Welker seamounts, but are distinct from the younger alkaline intraplate lavas that cap Pratt-Welker edifices. The weathered, encrusted basalts were most likely erupted in a near-ridge environment, adjacent to Explorer Ridge, between 11 and 14 Ma. No evidence of plume-related activity is found in this area. Compared with northeast Pacific mid-ocean ridge and alkaline intraplate basalts, Graham seamount lavas have anomalously high 206Pb/204Pb, which does not appear to be a function of sea-floor alteration, magma contamination, or mixing between previously identified mantle components. All near-ridge seamounts in the northeast Pacific exhibit isotopic heterogeneity that does not correlate with major or trace element composition, suggesting that the mantle sources of all near-ridge seamounts have been variably depleted by prior, but recent melting events.

Clustering coupled biochemical-physical model results formalizes regional provinces in a coastal region

2021 ◽  
Author(s):  
Susan Allen ◽  
Tereza Jarnikova ◽  
Elise Olson ◽  
Debby Ianson
Keyword(s):  
Physical Model ◽  
Three Dimensional ◽  
Coastal Region ◽  
Sparse Sampling ◽  
Strait Of Georgia ◽  
Northeast Pacific ◽  
Juan De Fuca ◽  
Main Basin ◽  
Physical Variables ◽  
Juan De Fuca Strait

<p>Coastal regions by their very nature are dynamically diverse.  Within one geographical region there are often multiple areas dominated by substantially different dynamics that shape not only the physical characteristics but also the ecosystem.  The Salish Sea, in the northeast Pacific, is an excellent example with strongly tidally mixed regions, freshwater-dominated regions, and regions directly influenced by the open ocean.  These regions are generally well known and multiple disciplines refer to them with various boundaries and under various names.  Here we use unsupervised clustering on numerical model results to formalize these regional provinces.  The model is SalishSeaCast,  a three-dimensional real-time coupled bio-chem-physical model based on the NEMO framework.  We find that the regions clustered on ecosystem variables (phytoplankton biomass) spatially coincide with those clustered on physical variables, particularly the stratification as diagnosed by the halocline depth.  The clusters are robust across years with interannual variability manifesting mostly in changes in the size of the clusters.  As the clusters are dynamically distinct, they provide a natural framework on which to evaluate the model against observations.  We find that the model accurately simulates each of the major clusters.  The spatial and temporal resolution of the model can then characterize these different clusters more systematically than the observations, revealing biases associated with sparse sampling in the observations. Two examples will be given, one addressing a long-standing issue of the productivity gradient in the stratified main basin, the Strait of Georgia, and another concerning the seasonal cycle of productivity in the ocean-influenced Juan de Fuca Strait.</p>

Two New Records of Benthic Polychaetes from Washington

1971 ◽  
Vol 28 (10) ◽  
pp. 1491-1492
Author(s):  
Frederic H. Nichols
Keyword(s):  
Pacific Ocean ◽  
New Records ◽  
Puget Sound ◽  
Polychaete Species ◽  
Incomplete Knowledge ◽  
Northeast Pacific ◽  
Juan De Fuca ◽  
Juan De Fuca Strait ◽  
Northeast Pacific Ocean

Two benthic polychaete species, Chloeia entypa Chamberlin and Drilonereis falcata minor Hartman, heretofore not recorded from the northeast Pacific Ocean, have been found in samples from the Washington coast, Juan de Fuca Strait, and Puget Sound. These new records reflect incomplete knowledge of the polychaete fauna of these areas.

Two new natatory asellote isopods (Crustacea) from the San Juan Archipelago, Baeonectes improvisus n. gen., n. sp. and Acanthamunnopsis milleri n. sp., with a revised description of A. hystrix Schultz

1982 ◽  
Vol 60 (12) ◽  
pp. 3332-3343 ◽  
Author(s):  
George D. Wilson
Keyword(s):  
Surface Waters ◽  
Type Species ◽  
Saline Water ◽  
Original Description ◽  
San Juan ◽  
The Family ◽  
Two New Species ◽  
Juan De Fuca ◽  
Taxonomic Concept ◽  
Highly Evolved

Two new species of asellote isopods from the waters surroundng the San Juan Archipelago are described and diagnosed. Baeonectes improvisus n. gen., n. sp. and Acanthamunnopsis milleri n. sp. belong to the highly evolved, natatory families Eurycopidae and Munnopsidae, respectively. Baeonectes, a circum-arctic and boreal shallow-water genus, also includes B. muticus (Sars), the type-species. The taxonomic concept of Acanthamunnopsis has difficulties that must be resolved before A. milleri can be described. To this end, the family Acanthamunnopsidae Schultz is invalidated and merged with the Munnopsidae; the genus Acanthamunnopsis Schultz is revised; and A. hystrix, the type-species, is redescribed with corrections and additions to the original description. The unusual presence of the bathypelagic genus Acanthamunnopsis in the surface waters of the San Juan Archipelago is discussed. Acanthamunnopsis milleri is tentatively postulated to be a deep resident of the open ocean that was carried landward into the Strait of Juan de Fuca by upwelled intrusions of cold, saline water.

Seiche Excitation in Port San Juan, British Columbia

1979 ◽  
Vol 36 (10) ◽  
pp. 1223-1227
Author(s):  
D. D. Lemon ◽  
P. H. LeBlond ◽  
T. R. Osborn
Keyword(s):  
British Columbia ◽  
Water Waves ◽  
Pressure Gauge ◽  
Low Frequency ◽  
San Juan ◽  
External Forcing ◽  
Edge Waves ◽  
Rectangular Basin ◽  
Juan De Fuca ◽  
Juan De Fuca Strait

Seiche motions observed in San Juan Harbour with a bottom-mounted pressure gauge have been Fourier-analyzed and interpreted in terms of a theoretical model of oscillations in a rectangular basin with an exponential depth profile. Two of the observed periods (at 14.6 and 38.5 min) are identified with resonances of the basin; two other significant low frequency peaks (at 21 and 55 min) do not coincide with resonant periods of the basin and must be due to strong external forcing. Higher frequency fluctuations (20–160 s) are attributed to swell and to its subharmonic interactions with edge waves. Key words: water waves, seiches, mathematical model, Juan de Fuca Strait, British Columbia

Zooplankton biomass, advection and production on the northern Gulf of Alaska shelf from simulations and field observations

2013 ◽  
Vol 128 ◽  
pp. 185-207 ◽  
Author(s):  
K.O. Coyle ◽  
G.A. Gibson ◽  
K. Hedstrom ◽  
A.J. Hermann ◽  
R.R. Hopcroft
Keyword(s):  
Gulf Of Alaska ◽  
Zooplankton Biomass ◽  
Field Observations

Leaf anatomy of the South African Danthonieae (Poaceae). III. Merxmuellera stricta

Bothalia ◽  
1980 ◽  
Vol 13 (1/2) ◽  
pp. 191-198 ◽  
Author(s):  
R. P. Ellis
Keyword(s):  
Environmental Factors ◽  
South African ◽  
Leaf Anatomy ◽  
Leaf Blade ◽  
Transverse Section ◽  
Anatomical Structure ◽  
The South ◽  
Abaxial Epidermis ◽  
Variable Species ◽  
Morphological Differences

The anatomical structure, of the leaf blade as seen in transverse section, and of the abaxial epidermis, of Merxmuellera stricta (Schrad.) Conert is described and illustrated. In this variable species four distinct anatomical “forms” are recognized viz. the typical  M. stricta form, the Cathedral Peak form, the Drakensberg form and the alpine form. The alpine and Cathedral Peak forms have recently been described as M. guillarmodiae Conert (1975). The degree of anatomical differentiation of these “forms” resembles the situation described in M. disticha (Nees) Conert (Ellis, 1980). Populations of both M. stricta and M. disticha from the Drakensberg mountains display extensive anatomical diversification which appears to be correlated with environmental factors. In addition, morphological differences are exhibited as well and the anatomical “forms” of M. stricta probably warrant taxonomic recognition.

scholarly journals Mexican dancer in Ecuador: molecular confirmation, embryology and planktotrophy in the sea slug Elysia diomedea

2020 ◽  
Vol 52 ◽  
Author(s):  
Lola Moreano-Arrobo ◽  
Oscar D. Pérez ◽  
Federico D. Brown ◽  
Fernanda X. Oyarzún ◽  
Cristian B. Canales-Aguirre
Keyword(s):  
Genetic Information ◽  
Ex Situ ◽  
Adult Size ◽  
Mtdna Sequences ◽  
Cell Stage ◽  
Egg Capsules ◽  
Northeast Pacific ◽  
Morphological Differences ◽  
General Aspects ◽  
Veliger Larvae

Elysia diomedea varies in adult size and color across its geographical distribution in Ecuador. Because of morphological variation and the absence of genetic information for this species in Ecuador, we analyzed mtDNA sequences in three populations (Ballenita, La Cabuya, and Mompiche) and confirmed that (1) individuals from the three locations belonged to E. diomedea and (2) that there was no population structure that could explain their morphological differences. Next, we analyzed general aspects about the reproductive biology and embryology of this species. Live slugs from the Ballenita population were maintained and reproduced ex situ. Egg ribbons and embryos were fixed and observed by brightfield and confocal microscopy. We observed a single embryo per capsule, 98 embryos per mm2 of egg ribbon, and compared the cleavage pattern of this species to other heterobranchs and spiralians. E. diomedea early development was characterized by a slight unequal first cleavage, occurrence of a 3-cell stage in the second cleavage, and the formation of an enlarged second quartet of micromeres. We observed clear yolk bodies in the egg capsules of some eggs ribbons at early stages of development. Both reproductive and embryological characteristics, such as presence of stomodeum in the larva, and ingestion of particles after hatching confirmed the planktotrophic veliger larvae of this species, consistent with the majority of sacoglossans from the Eastern and Northeast Pacific Oceans.

Sign in / Sign up

Export Citation Format

Share Document