A Faunal History of the North Atlantic Ocean
TL;DR: It is concluded that the geographic setting of the North Atlantic with its open exposure to the Arctic Ocean and its relatively small size are the main factors responsible for its history of varied surface temperature.
Abstract: Briggs, John C. (Dept. Zoology, Univ. S. Fla., Tampa 33620) 1970. A faunal history of the North Atlantic Ocean, Syst. Zool., 19:19-34 [Paleoclimate; marine faunas; zoogeography; North Atlantic Ocean].-Our modem, Northern Hemisphere boreal faunas apparently had a dual origin. In Paleocene-Eocene times, one cold-temperate evolutionary center probably became established in the Arctic Basin. Then, as the climate grew colder, another center south of the Bering Land Bridge began its development. During the Oligocene, boreal species were able to move out of the Arctic Basin into the North Atlantic and, in the Pacific, southward from the Bering Sea. By the late Miocene, when a seaway first became established through the Bering Strait, the movement of species was predominantly northward into the Arctic Ocean and thence to the North Atlantic. The second opening of the seaway in the late Pliocene had an even more striking result, transforming the character of the North Atlantic fauna yet scarcely affecting that of the North Pacific. In the contemporary North Atlantic, such characteristic features as a depauperate shore fauna; species with broad latitudinal ranges; the complete lack of an endemic, boreal pelagic group; and the very low rate of endemism at the oceanic islands; present a decided contrast to conditions in the North Pacific. These facts together with good evidence of Pleistocene faunal replacements, latitudinal shifts, and extinctions reveal that the North Atlantic has provided for its marine fauna a more rigorous environment than the North Pacific. It seems clear that alteration in temperature, the one evident variable, was the primary cause. It is concluded that the geographic setting of the North Atlantic with its open exposure to the Arctic Ocean and its relatively small size are the main factors responsible for its history of varied surface temperature. The most severe drops in temperature probably took place during the ice ages of the Pleistocene and these appear to have averaged about 30C below the present winter minimum. The shelf and pelagic surface fauna that becomes established under such conditions is vastly different, in terms of diversity and local geographic distribution, from a fauna occupying a more stable environment.
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TL;DR: Support for the hypothesis of ecological opportunity comes from the finding that hard-bottom communities, especially those in the northwestern Atlantic, show a higher representation of molluscan species of Pacific origin, and are likely to have been more affected by climatic events, than were communities on unconsolidated sandy and muddy bottoms.
Abstract: When the Bering Strait between Alaska and Siberia opened about 3.5 Ma during the early Pliocene, cool-temperate and polar marine species were able to move between the North Pacific and Arctic-Atlantic basins. In order to investigate the extent, pattern, and dynamics of this trans- Arctic interchange, I reviewed the Recent and fossil distributions of post-Miocene shell-bearing Mollusca in each of five northern regions: (1) the northeastern Atlantic (Lofoten Islands to the eastern entrance of the English Channel and the northern entrance of the Irish Sea), (2) northwestern Atlantic (southern Labrador to Cape Cod), (3) northeastern Pacific (Bering Strait to Puget Sound), (4) northwestern Pacific (Bering Strait to Hokkaido and the northern Sea of Japan), and (5) Arctic (areas north of the Lofoten Islands, southern Labrador, and Bering Strait). I have identified 295 molluscan species that either took part in the interchange or are descended from taxa that did. Of these, 261 are of Pacific origin, whereas only 34 are of Arctic-Atlantic origin. Various analyses of the pattern of invasion confirm earlier work, indicating that there is a strong bias in favor of species with a Pacific origin. A geographical analysis of invaders implies that, although trans-Arctic interchange contributed to a homogenization of the biotas of the northern oceans, significant barriers to dispersal exist and have existed for trans-Arctic invaders within the Arctic-Atlantic basin. Nevertheless, trans-Arctic invaders in the Atlantic have significantly broader geographical ranges than do taxa with a pre- Pliocene history in the Atlantic. Among the possible explanations for the asymmetry of trans-Arctic invasion, two hypotheses were explicitly tested. The null hypothesis of diversity states that the number of invaders from a biota is proportional to the total number of species in that biota. Estimates of Recent molluscan diversity show that the North Pacific is 1.5 to 2.7 times richer than is the Arctic-Atlantic, depending on how faunistic comparisons are made. This difference in diversity is much smaller than is the asymmetry of trans-Arctic invasion in favor of Pacific species. Rough estimates of regional Pliocene diversity suggest that differences in diversity during the Pliocene were smaller than they are in the Recent fauna. The null hypothesis was therefore rejected. The hypothesis of ecological opportunity states that the number of invaders to a region is pro- portional to the number of species that became extinct there. The post-Early Pliocene magnitude of extinction was lowest in the North Pacific, intermediate in the northeastern Atlantic, and probably highest in the northwestern Atlantic. The absolute number and faunistic importance of post-Early Pliocene invaders (including trans-Arctic species, as well as taxa previously confined to warm- temperate waters and western Atlantic species that previously occurred only in the eastern Atlantic) was lowest in the North Pacific, intermediate in the northeastern Atlantic, and highest in the northwestern Atlantic. Further support for the hypothesis of ecological opportunity comes from the finding that hard-bottom communities, especially those in the northwestern Atlantic, show a higher representation of molluscan species of Pacific origin, and are likely to have been more affected by climatic events, than were communities on unconsolidated sandy and muddy bottoms. Support for the hypothesis does not rule out other explanations for the observed asymmetry of trans-Arctic invasion. A preliminary study of species-level evolution within lineages of trans-Arctic invaders indicates that anagenesis and cladogenesis have been more frequent among groups with Pacific origins than among those with Atlantic origins, and that the regions within the Arctic-Atlantic basin with the highest absolute number and faunistic representation of invaders (western Atlantic and Arctic) are the regions in which speciation has been least common among the invaders. The asymmetry of invasion is therefore distinct from the asymmetry of species-level evolution of invaders in the various northern marine regions.
374 citations
Journal Article•
TL;DR: A comparison study of the morphology of sediments in the interstitial environment of the Delta area and the effects of weather and climate on sediments and organic matter.
Abstract: CONTENTS
1. Introduction 5
2. Methods 8
2.1. Sampling methods 8
2.2. Sorting and preservation of the samples 10
2.3. Measuring methods for the environmental factors....... 10
2.3.1. Introduction 10
2.3.2. The grain-size data 10
2.3.3. Amount of organic matter 12
2.3.4. The interstitial water 14
2.3.5. Exposure to waves 14
2.4. Mathematical methods 15
3. The environment 17
3.1. Weather and climate 17
3.2. The morphology of the Delta area 19
3.3. Substrate and sediments 20
3.3.1. Types of sediments and substrate 20
3.3.2. Distribution of sediments..... ...... 22
3.3.3. Sorting of sediments 25
3.3.4. Important characteristics of sediments........ 25
3.3.4.1. Water circulation 25
3.3.4.2. Interstitial temperature 29
3.3.4.3. Interstitial salinity 29
3.3.4.4. Oxygen in the interstitial environment...... 34
3.3.5. Organic matter 35
253 citations
TL;DR: The consistent geographic structuring within presumed widespread species suggests that historical range fragmentation during the Pleistocene ultimately increased Canadian polychaete diversity and that the coastal British Columbia fauna played a minor role in Arctic recolonization following deglaciation.
Abstract: Background
Although polychaetes are one of the dominant taxa in marine communities, their distributions and taxonomic diversity are poorly understood. Recent studies have shown that many species thought to have broad distributions are actually a complex of allied species. In Canada, 12% of polychaete species are thought to occur in Atlantic, Arctic, and Pacific Oceans, but the extent of gene flow among their populations has not been tested.
Methodology/Principal Findings
Sequence variation in a segment of the mitochondrial cytochrome c oxidase I (COI) gene was employed to compare morphological versus molecular diversity estimates, to examine gene flow among populations of widespread species, and to explore connectivity patterns among Canada's three oceans. Analysis of 1876 specimens, representing 333 provisional species, revealed 40 times more sequence divergence between than within species (16.5% versus 0.38%). Genetic data suggest that one quarter of previously recognized species actually include two or more divergent lineages, indicating that richness in this region is currently underestimated. Few species with a tri-oceanic distribution showed genetic cohesion. Instead, large genetic breaks occur between Pacific and Atlantic-Arctic lineages, suggesting their long-term separation. High connectivity among Arctic and Atlantic regions and low connectivity with the Pacific further supports the conclusion that Canadian polychaetes are partitioned into two distinct faunas.
Conclusions/Significance
Results of this study confirm that COI sequences are an effective tool for species identification in polychaetes, and suggest that DNA barcoding will aid the recognition of species overlooked by the current taxonomic system. The consistent geographic structuring within presumed widespread species suggests that historical range fragmentation during the Pleistocene ultimately increased Canadian polychaete diversity and that the coastal British Columbia fauna played a minor role in Arctic recolonization following deglaciation. This study highlights the value of DNA barcoding for providing rapid insights into species distributions and biogeographic patterns in understudied groups.
248 citations
Cites background from "A Faunal History of the North Atlan..."
...5 Ma [25,58] or since the formation of ice sheets in North America 2....
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...Consistent with other marine taxa [25,58], the highest proportion of unique species was apparent in the Pacific (British Columbia), while Arctic and Atlantic species typically had broad distributions (Figure 6)....
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...Interestingly, the Atlantic had a lower proportion of unique species in this study than the Arctic, which may reflect its substantial impoverishment during the last glaciation and its recolonization by Pacific and European species [25,58]....
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TL;DR: The European green crab, Carcinus maenas, has a native distribution that extends from Norway to Mauritania as discussed by the authors, and a clear genetic break (11% sequence divergence) occurs between the Mediterranean and Atlantic, supporting the species-level status of these two forms.
Abstract: The European green crab, Carcinus maenas , has a native distribution that extends from Norway to Mauritania. It has attracted attention because of its recent invasions of Australia, Tasmania, South Africa, Japan and both coasts of North America. To examine the population structure of this global invader in its native range, we analysed a 502-base-pair fragment of the mitochondrial cytochrome c oxidase I (COI) gene from 217 crabs collected in the North Atlantic and 13 specimens from the Mediterranean. A clear genetic break (11% sequence divergence) occurs between the Mediterranean and Atlantic, supporting the species-level status of these two forms. Populations in the Faeroe Islands and Iceland were genetically distinct from continental populations ( F ST = 0.264–0.678), with Iceland represented by a single lineage also found in the Faeroes. This break is consistent with a deep-water barrier to dispersal in green crabs. Although there are relatively high levels of gene flow along the Atlantic coast of Europe, slight population structure was found between the central North Sea and populations to the south. Analysis of variance, multidimensional scaling, and the distribution of private haplotypes support this break, located between Bremerhaven, Germany, and Hoek van Holland. Similar biogeographical and genetic associations for other species, such as benthic algae and freshwater eels, suggest that the marine fauna of Europe may be generally subdivided into the areas of Mediterranean, western Europe and northern Europe.
242 citations
01 Jan 1995
TL;DR: A history of marine research on the Azores is outlined in this paper, where a meeting point for shallow water marine fauna and flora of different origins is described, and the species composition of one of the best studied groups of organisms, the fish, is compared between locations in the northeastern Atlantic.
Abstract: A history of marine research on the Azores is outlined. Until two decades ago most oceanic and littoral marine studies had been carried out by foreign scientists. Studies by Azorean scientists started to increase in the early 1980s when the University of the Azores was created. 2. Ocean circulation in this part of the Atlantic is described as a background for biogeography and diversity. The picture emerges that Azores is a 'meeting point' for shallow water marine fauna and flora of different origins. 3. The species composition of one of the best studied groups of organisms, the fish, is compared between locations in the northeastern Atlantic. The work on fish is also compared with other well studied groups (algae and hydroids) to highlight the interest of the Azores as a natural biogeographical experiment. 4. Studies of marine resources began less than two decades ago. The development of demersal fisheries is described focusing on the switch from small-scale artisanal fishing to more commercial fisheries. 5. Conservation of species and legislation in force for molluscs, crustaceans, fishes, marine turtles, seabirds and marine mammals are summarized. 6. Protected marine areas already designated are defined, as well as new areas recommended. 7. The paper concludes with a discussion of current threats and future management strategies.
224 citations
References
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TL;DR: A within-habitat analysis was made of the bivalve and polychaete components of soft-bottom marine faunas which differed in latitude, depth, temperature, and salinity, and it was indicated that species number is the more valid diversity measurement.
Abstract: In this paper a methodology is presented for measuring diversity based on rarefaction of actual samples. By the use of this technique, a within-habitat analysis was made of the bivalve and polychaete components of soft-bottom marine faunas which differed in latitude, depth, temperature, and salinity. The resulting diversity values were highly correlated with the physical stability and past history of these environments. A stability-time hypothesis was invoked to fit these findings, and, with this hypothesis, predictions were made about the diversities present in certain other environments as yet unstudied. The two types of diversity, based on numerical percentage composition and on number of species, were compared and shown to be poorly correlated with each other. Our data indicated that species number is the more valid diversity measurement. The rarefaction methodology was compared with a number of diversity indexes using identical data. Many of these indexes were markedly influenced by sample size. Good...
2,354 citations
"A Faunal History of the North Atlan..." refers background in this paper
...Were the early Tertiary cycles more severe in the arctic and the North Atlantic? Faunal diversity is related not only to geographic area but to climatic stability; that is, the more stable the climate, the greater the diversity (Sanders, 1968)....
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Book•
01 Jan 1953
TL;DR: Zoogeography of the sea as discussed by the authors, Zoogeography in the sea, Zoogeographical of the Sea, Zoo Geography of Sea, and Zoo geography of the ocean.
Abstract: Zoogeography of the sea , Zoogeography of the sea , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
1,250 citations
Book•
01 Jan 1925
TL;DR: The first part of the general report, dealing with the fishes was published in 1925, as Bulletin of the United States Bureau of FisherIes, and subsequent parts describing the plankton of the offshore waters of the Gulf and the physical Characteristics of its waters were published in 1926-27, as Part 2. as discussed by the authors.
Abstract: During the summer of 1912 the Bureau of Fisheries with the cooperation of the Museum of Com;arative Zoology of Harvard Un~vers~ty, cOInInenced an oceanographic and bIOlogIcal survey of the Gulf of Maine, with special reference to its fishes to its floating plants and animals (Plankton), to the physical and chemical state of its waters and to the circulation of the latter. Cruises ;ere made on the Fisheries schooner Grampu8 during the summers and autumns of 1912, 1913, 1914, 1915 and 1916, and during the winters and springs of 1913 and 1915. The work Was interrupted by the war, but was resumed with a cruise of the Fisheries steamer Albatross in the late winter and spring of 1920, and was continued by the Fisheries steamer Halcyon during the winter and spring of 1920-21, and the summers of 1921 and 1922. The first part of the general report, dealing with the fishes was published in 1925, as Bulletin ~o (Pt. 1) of the United States Bureau of FisherIes; 1 SUbsequent parts describing the plankton of the offshore waters of the Gulf and the physical Characteristics of its waters were published in 1926-27, as Part 2. The preparation of the section on the fishes was assigned originally to W. W. Welsh, who had gathered a large body of original observations on the growth, reproduction, diet, and other phases of the lives of many of the more important species. The report was far advanced when it was interrupted by his untimely death, and H. B. Bigelow ~dertook to carry it to publication along the Imes originally laid down. The new edition, entailing a general revision and the addition of In'Uch new lnaterial, has been prepared jointly by !: B. Bigelow and by W. C. Schroeder.
1,143 citations
969 citations