Shallow-water Fauna Research Articles

Shallow ocean deoxygenation drove trilobite turnover during the late Cambrian SPICE event

The spread of marine anoxia is believed to have played a key role in the development of the SPICE (Steptoean Positive Carbon Isotope Excursion) event and the end-Marjuman extinction in the late Cambrian (∼497.5 m.y. ago), but their cause-and-effect relationship is poorly constrained. Here we present an integrated analysis of carbonate δ13C, cerium anomalies (Ce/Ce*), and genus-level diversity data of trilobites from the North China Platform. Our results show tightly coupled changes between the SPICE, an increase in Ce/Ce*, and a trilobite turnover event, which we interpret as indicating enhanced productivity and organic remineralization, leading to the development of low-oxygen conditions in shallow-water settings. This study therefore establishes a direct link between local ecological stress and trilobite turnover during the global SPICE event. Furthermore, the presence of low-oxygen rather than fully anoxic conditions during the peak of the SPICE event could explain the nature of the end-Marjuman crisis, which was characterized by the replacement of shallow-water fauna by deeper-water counterparts that were potentially more tolerant of hypoxia.

How Tolerant Are Hydroids to Climate-Change-Induced Acute Spikes in Sea Water Temperature? A Case Study of Arctic Dynamena pumila (L., 1758)

The temperature of the water surface layer in the Arctic may increase significantly in the coming decades. To what extent will shallow-water fauna be affected by warming? We investigated this issue using an example of one species of colonial hydroid, Dynamena pumila. We judged its reaction to warming via its pulsation activity and the growth of stolons. Pulsations of the coenosarc in colonial hydroids are a sensitive indicator of the body’s reaction to the influence of environmental factors. We tested the ability of D. pumila colonies to survive and adapt to existing at 25 °C for five days. After raising the temperature from 14 °C to 25 °C, colony growth and the pulsation of stolon growth tips on the first day increased and then decreased during the day. In the following days, the growth pulsations almost ceased, the colonies stopped growing, and their coenosarcs began to exfoliate from their perisarcs. However, by the fourth day, this process slowed down, and the colonies existed in an economy mode of experiencing unfavourable conditions. The thermal shock continued in the experiment for five days. Then, after the temperature dropped from 25 °C to 15–16 °C, all the colonies recovered within five days and continued to grow.

Diversity, distribution patterns and indicatory potential of echinoderm communities of the tropical East Atlantic (Gulf of Guinea): Influence of multiple natural and anthropogenic factors along a 25–1000 m depth gradient

All earlier studies of the West African echinoderm fauna have focused on taxonomy, and general knowledge about benthic community responses to various human related threats are poorly diagnosed and not monitored along the whole African coast. Our analysis of diversity and distribution patterns of Ghanaian echinoderms yielded 36 species. Material was collected at nine transects distributed along the coast of Ghana (25–1000 m depth range, total of over 270 samples). Gradual decreases in species richness, diversity, evenness and abundance were observed along the depth gradient, with the most diverse fauna being recorded on the shelf (25–50 m). The most abundant species were Ophiactis luetkeni and Ophiothrix congensis, although both had very patchy distributions. Cluster analysis separated shelf communities (25–100 m) from slope communities (500–1000 m), although on a low level of similarity. Our analysis allowed to select most vulnerable benthic habitats that should be amongst priorities of the future monitoring. Local influence of arsenic was observed at some shelf sites, while slope fauna was affected by elevated levels of hydrocarbons and barium. Changes in salinity and fluorescence also influenced echinoderm assemblages. The most general trend showed patchily distributed, diverse shallow water fauna being influenced by increased microhabitat diversity and food availability, while depauperate slope fauna was affected by local disturbances associated with oil extraction. Tropical echinoderm communities have a great potential as indicators of even minor and local pollution, although high patchiness and low abundance creates difficulties in the multivariate analysis. High sampling effort and high number of replicates allowed to minimise those problems and demonstrated small scale microhabitat diversity.

Molecular phylogeny and biogeography of the living Pleurotomariidae (Vetigastropoda), with the description of a new genus

ABSTRACT The once diverse family Pleurotomariidae had a widespread global distribution spanning shallow-water faunas throughout the Mesozoic but is presently known only from bathyal habitats along the western margins of the Atlantic and Indo-Pacific Oceans at temperate and tropical latitudes. We evaluate the relationships among surviving lineages of Pleurotomariidae using partial sequences of two mitochondrial genes and three nuclear genes for 22 of the 45 named Recent species-level taxa for which sequence data were available for two or more genes. Phylogenetic analyses partition these species among five lineages, including the new genus Bouchetitrochus n. gen. that is described herein. Of the five lineages, two are present in both the western Atlantic and the western Indo-Pacific Oceans, one is endemic to the western Atlantic and two are endemic to the western Indo-Pacific.

New Middle Ordovician (Darriwilian) faunas from the Sultanate of Oman

New trilobite material and the first graptolites from outcrop are described from the Am5 member of the Amdeh Formation near Al Fleij in northeast Oman. The sediments in which these faunas occur are interpreted as distal-shelf deposits with storm beds packed with brachiopods and orthoconic nautiloids. The deposits and its faunas are considered of late Darriwilian age and younger than the shallower-water Am5 deposits known from other outcrops. No palynomorphs could be recovered to confirm this due to the increased burial temperature the Al Fleij area has experienced.The trilobites are of considerable palaeo-biogeographic interest as few faunas of this age are known from the Arabian Plate, though their preservation precludes the establishment of new species. They include Isabelinia aff. glabrata, Liomegalaspides sp., Neseuretus tristani, Neseuretinus sp. and the deeper-water forms, Cyclopyge cf. C. bohemica, Arthrorhachis sp. and Brachypleura sp. The graptolites are pendent Didymograptus spp. of later Darriwilian type.Rare elements of the conodonts Nordiora, Amorphognathus and Microzarkodina have been recovered from shell beds that occur interbedded with the faunas. They too indicate a late Darriwilian age and differ from richer, restricted, shallow-water faunas known from the Am5 at other locations, and the more cosmopolitan shelf fauna from the Ayim Member of the Rann Formation of the United Arab Emirates.A coarser, 80 m-thick, terrestrial sequence containing igneous pebbles, included in the Am5 in the 1980s, is shown from the occurrence of fossil plants to be of Permian age and probably equivalent to the Basal Saiq Clastics of Jabal al Akhdar.

Unusual shallow-water boreal gastropod species associations at the Northern part of Arctic archipelago Novaya Zemlya

The fauna of the Barents Sea is the richest compared to other Arctic seas and is represented by a mixture of Arctic and boreal species, the distribution of which is believed to be due to the temperature conditions. In this study, this hypothesis was tested using data on the species composition of gastropods in the northern part of Novaya Zemlya, one of the coldest regions in the Barents Sea. Species associations with the predominance of the boreal species Lacuna vincta (Montagu, 1803) were found in the studied area; additionally, the fauna of gastropods was generally more similar to that of the boreal regions (White Sea and the Murman Coast) than the Arctic (fjords of Svalbard, Matochkin Shar (Novaya Zemlya), Franz Josef Land). The results obtained do not agree with the assumption about the effect of the temperature being the main factor determining the distribution of benthic communities in the Barents Sea. Two alternative hypotheses are proposed: either the influence of the Novaya Zemlya current as a corridor for the dispersal of species; or the existence of a glacier refugium off the coast of Novaya Zemlya where the shallow-water fauna could have survived the last glaciation.

Brachyuran crabs (Crustacea, Decapoda) from the remote oceanic Archipelago Trindade and Martin Vaz, South Atlantic Ocean.

Forty species of shore and shallow water brachyuran crabs are reported from the remote oceanic Archipelago Trindade and Martin Vaz (TMV), 11 of which were previously known from Trindade Island, 28 are recorded from the Archipelago for the first time, and one is a new species, Epialtus parvulus sp. nov. This brings the total known shore and shallow water decapod fauna of TMV to 99 species. The opportunity is taken here to elaborate on the taxonomy of the species reported from TMV. One new genus, Mecataleptodius, is recognized for two species, Cancer parvulus Fabricius, 1793, its type species, and Cataleptodius olsoni Manning Chace, 1990, endemic to Ascension Island. The following seven nominal species are synonymized: Acanthonyx dissimulatus Coelho in Coelho Torres, 1993; A. scutiformis (Dana, 1851a); Dromia gouveai Melo Campos Junior, 1999; Epialtus portoricensis Rathbun, 1923; Ranilia guinotae Melo Campos Junior, 1994; R. saldanhai H. Rodrigues da Costa, 1970; and Omalacantha garthi (Lemos de Castro, 1953). TMV is a subset of the western Atlantic crab fauna (23 species or 57.5%), also including 8 (20%) amphi-Atlantic species, 3 (7.5%) amphi-American, 3 (7.5%) endemic, 2 (5%) cosmopolitan, 1 (2.5%) known from both sides of the Atlantic and the Indo-West Pacific. The crab fauna of TMV, Ascension (AS) and Saint Helena (SH) are compared with one another as well as with that of the oceanic islands Fernando de Noronha (FN) and the Rocas Atoll (RA) by means of nonmetric multidimensional scaling (NMDS) applied to a dissimilarity matrix generated by Jaccards coefficient. TMV-FN-RA and AS-SH clustered into two distinct groups according to the composition of their crab fauna. The NMDS analysis ranked the species that cause segregation of the crab faunal assemblages among TMV, AS, and SH, while revealing a gradient in species composition between the two groups of islands (TMV-FN-RA and AS-SH) formed by the amphi-Atlantic species. Island isolation, age and size alone do not explain the existing differences in species richness among TMV, AS and SH. The taxonomic composition of the shallow water fauna in these islands is likely to have been determined by several variables that were interwoven differently along their evolutionary history.

First description of deep benthic habitats and communities of oceanic islands and seamounts of the Nazca Desventuradas Marine Park, Chile

Seamounts and oceanic islands of the Chilean Exclusive Economic Zone at the intersection of the Nazca and Salas y Gómez ridges lie within one of the least explored areas in the world. The sparse information available, mainly for seamounts outside Chilean jurisdiction and shallow-water fauna of the Desventuradas Islands, suggests that the area is a hotspot of endemism. This apparent uniqueness of the fauna motivated the creation of the large Nazca-Desventuradas Marine Park (NDMP, ~ 300,000 km2) around the small islands San Felix and San Ambrosio in 2015. We report for the first time a detailed description of benthic microhabitats (i.e., centimeter to meter scale), macrohabitats (i.e., meter to kilometer-scale) and associated megafauna within the NDMP. Descriptions were based on analysis of fauna collected by trawling and ROV video observations from ~ 50 to 370 m depth. Rocky, coarse sand and silty sediment bottom habitats were observed at island slopes. In contrast, rocky and coarse sandy bottom habitats with a predominance of rhodoliths, thanatocoenosis, and other biogenic components were observed at seamounts. Mobile fauna and predators dominated the oceanic islands and nearby seamounts, whereas seamounts farther from the islands were dominated by sessile and hemisessile fauna that were mainly suspension and deposit feeders. Based on the register of 118 taxonomic units, our results provide an expanded and updated baseline for the benthic biodiversity of NDMP habitats, which seemed pristine, without evidence of trawling or anthropogenic debris.

Stratigraphy and paleogeographic environments for the forming the Carpian Series (Stryi and Opir River basins, Ukrainian Carpathians)

Results of studying the Carpian Series – a component of the thick Lower Cretaceous-Miocene flysch of the Outer (Flysch) Carpathians are presented in the article. Sediments of the Carpian Series (Middle Paleocene – Eocene) were studied in the Skole Beskids in the basin of the middle and lower reaches of the river Opir in the area of conducting geological and geographical educational practices of students of Ukrainian universities. Using the method of sedimentological analysis, it was found that the investigated sediments are the product of the activity of gravitational flows (mainly turbidites, as well as grainites, debrites), bottom currents and background hemipelagic sedimentation. These sediments are compared with the facies of deep-marine fans placed on the continental slope and its foot. Medium- and coarse-grained turbidites and grainites (Yamna and Vyhoda formations) correspond to the submarine valley-channel facies. Fine- and medium-grained turbidites and hemipelagites (Manyava and Bystrytsa formations) belong to the inter-channel facies. The composition of the clastic material (green and red phyllites) suggests, that the sediments were drifted from the Eurasian continental margin into the deep-marine fan (fans?). Applying the micropaleontological method, it was established that the Paleocene-Eocene background red and green clay hemipelagites are enriched in buried in situ benthic foraminifera (deep-water agglutinated foraminifera: DWAF), which indicate lower bathyal – abyssal depths of flysch accumulation below a calcite compensation depth (CCD). Late Eocene calcareous lithofacies of the Popiele Formation contain a mixed foraminifera assemblage formed as a result of mud and debris flows. Shallow-water fauna and “exotic” debris (including the red and green phyllites) were transferred from the shelf area to the deep basin. The Latest Eocene hemipelagic clay-carbonate sediments of the Sheshorian horizon contain the foraminiferal assemblage with plankton dominance, which indicates a general shallowing of the paleobasin (middle-upper bathyal conditions above a calcite compensation depth) at the end of the Carpian time. Key words: stratigraphy, paleogeography, Ukrainian Outer Carpathians, Paleocene-Eocene flysch, turbidites, foraminifera.

Sedimentary and volcanic record of the nascent Izu-Bonin-Mariana arc from IODP Site U1438

Abstract The oldest known, intact sedimentary record of a nascent intraoceanic arc was recovered in a ∼100-m-thick unit (IV) above ca. 49 Ma basaltic basement at International Ocean Discovery Program Site U1438 in the Amami Sankaku Basin. During deposition of Unit IV the site was located ∼250 km from the plate edge, where Izu-Bonin-Mariana subduction initiated at 52 Ma. Basement basalts are overlain by a mudstone-dominated subunit (IVC) with a thin basal layer of dark brown metalliferous mudstone followed by mudstone with sparse, graded laminae of amphibole- and biotite-bearing tuffaceous sandstone and siltstone. Amphibole and zircon ages from these laminae suggest that the intermediate subduction-related magmatism that sourced them initiated at ca. 47 Ma soon after basement formation. Overlying volcaniclastic, sandy, gravity-flow deposits (subunit IVB) have a different provenance; shallow water fauna and tachylitic glass fragments indicate a source volcanic edifice that rose above the carbonate compensation depth and may have been emergent. Basaltic andesite intervals in upper subunit IVB have textures suggesting emplacement as intrusions into unconsolidated sediment on a volcanic center with geochemical and petrological characteristics of mafic, differentiated island arc magmatism. Distinctive Hf-Nd isotope characteristics similar to the least-radiogenic Izu-Bonin-Mariana boninites support a relatively old age for the basaltic andesites similar to detrital amphibole dated at 47 Ma. The absence of boninites at that time may have resulted from the position of Site U1438 at a greater distance from the plate edge. The upper interval of mudstone with tuffaceous beds (subunit IVA) progresses upsection into Unit III, part of a wedge of sediment fed by growing arc-axis volcanoes to the east. At Site U1438, in what was to become a reararc position, the succession of early extensional basaltic magmatism associated with spontaneous subduction initiation is followed by a rapid transition into potentially widespread subduction-related magmatism and sedimentation prior to the onset of focused magmatism and major arc building.

Triumph and tribulation for shallow water fauna during the Paleocene–Eocene transition; insights from the United Arab Emirates

Triumph and tribulation for shallow water fauna during the Paleocene–Eocene transition; insights from the United Arab Emirates

Geochemistry and paleoecology of shales from the Cenomanian-Turonian Afowo formation Dahomey Basin, Nigeria: Implication for provenance and paleoenvironments

Cenomanian – Turonian (CT) Afowo shales selected from offshore X, and coastline Orimedu-1 and Ise-2 exploratory wells in the Dahomey Basin, southwestern Nigeria, were analyzed for foraminifera, major oxide and trace elements to evaluate their provenance and paleoenvironments.The hydrocarbon rich calcareous CT shale is about 100m thick in the coastline area and 300m thick in offshore area with abundant of marine planktonic and benthonic foraminifera. Benthonic species were significantly present in the coastline wells suggesting a shallow marine condition probably a neritic to inner shelf environments while abundant deep water Rotaliporid sp. and shallow water fauna heterohelix sp. in X well suggest inner shelf to bathyal (ca. >350 m) depositional environments.SiO2 and Al2O3 are the most abundant oxides of CT shale with average value of 46.4% and 12.7% in X, 57.1% and 15.65% in Orimedu-1 and 55.3% and 13.1% in Ise-2 respectively suggesting high influx of terrigenous and argillaceous sediments at the coastal area. Average Al2O3/TiO2 of 19.2 in X, 17.8 in Orimedu-1 and 19.3 in Ise-2 indicates that the sediments were sourced from intermediate igneous rock. Favorable oxic conditions for chemical weathering is more pronounce in the manganese concentration of 658–937 ppm in Orimedu-1 and 829–838 ppm in Ise-2 than 364–604 ppm in the shales from X well. Their degree of weathering estimated from chemical index of alteration (CIA) averaging 97 in the coastline wells is higher than 61 in X well, thus indicating high degree of oxidation in the depositional environments. Vanadium to nickel ratio ranging from 2.88 to 5.0 in X well suggest mixed marine and terrigenous source under dysoxic to oxic conditions for the shales while 0.48–1.2 values in Orimedu-1 further indicates a prevailing oxidizing condition at the time of deposition.Dysoxic-oxic and moderate deep-water conditions were more favorable in the offshore area and probably a significant paleo-factor for organic matter preservation of CT shales in the basin.

Digenean parasites of deep-sea teleosts: A progress report.

The developments in the study of digeneans of deep-sea fish in the 21st Century are documented and discussed. Most recent work has been on the bathyal fauna (i.e. 1,000m-2,999 m depth), with virtually nothing on the abyssal fauna (i.e. deeper than 3,000 m). The one study on hydrothermal vent digeneans has indicated that these regions probably harbour a distinctive fauna. The demarcation of the deep-sea fauna is blurred at the poles, where the cold-adapted fauna appears similar to the shallower bathyal fauna. The abyssal fauna, however, appears distinct, possibly due to adaptations to variable or ultra-high pressures. The digenean fauna of bathypelagic fishes is depauperate. Recent phylogenetic studies reinforce the view that the typical deep-sea fauna has radiated in the deep-sea. Encroachment into the deep from shallow water is relatively rare. Overall, the digenean fauna in the deep-sea is distinctly less diverse that the equivalent fauna in shallow waters. A major conclusion is that our understanding of the deep-sea digenean fauna is poor, and that much further work over a much wider area is needed.

Long-term turnover of the sponge fauna in Faro Lake (North-East Sicily, Mediterranean Sea)

The paper focuses on the long-term taxonomic composition and distribution of the shallow-water sponge fauna from the meromictic–anchialine coastal basin Faro Lake (Southern Italy), comparing recent qualitative field data with literature data over a 50-year period. The Faro Lake shallow water currently hosts 24 conspicuous species of Porifera belonging to 21 genera, 18 families, eight orders, three subclasses and two classes, i.e. Demospongiae (23) and Calcarea (one). The comparison between the present and past status of the sponge fauna showed a high turnover, with 15 new colonizers and only nine persistent species. Thirteen species reported in the literature are missing, suggesting the occurrence of remarkable changes in the faunal composition during the last 50 years. The analysis of the geographic distribution of each species allowed us to outline the prevalent North Atlantic affinity of the sponge community. Worthy of note is the new record of the alien calcareous sponge Paraleucilla magna of cryptogenic origin.

An Upper Cretaceous (middle Campanian) marine chondrichthyan and osteichthyan fauna from the Rattlesnake Mountain sandstone member of the Aguja Formation in West Texas

A thin phosphate-granule conglomerate within the Upper Cretaceous (middle Campanian) Rattlesnake Mountain sandstone member of the Aguja Formation preserves a diverse chondrichthyan and osteichthyan fauna. This highly fossiliferous deposit (the ‘Ten Bits Microsite’) yielded about 5000 teeth, spines, and denticles in a small amount of matrix (c. 150 kg). About 30 identifiable species of sharks, rays, and bony fishes are recognized. Two of the three most abundant chondrichthyan species at Ten Bits (Scapanorhynchus texanus and Ischyrhiza mira) are also the most common species in other middle to late Campanian marine vertebrate faunas along the Gulf and Atlantic Coastal Plain. The myliobatiform rays Brachyrhizodus and Rhombodus that occur at Ten Bits also appear to be characteristic of the Gulf and Atlantic Coast, as are lamniform sharks such as Cretalamna and Serratolamna. These taxa are entirely absent or extremely rare in Western Interior Campanian faunas. In contrast, some small orectolobiform sharks (Cantioscyllium, Chiloscyllium, Columbusia) and small rays (Protoplatyrhina) found at Ten Bits are common in shallow water faunas of the Western Interior and Texas Coastal Plain, but rarely reported from the eastern Gulf or Atlantic Coast. The common Western Interior ray Myledaphus bipartitus does not occur at Ten Bits or in any Gulf or Atlantic Coast fauna. Ptychotrygon agujaensis is abundantly represented in the Ten Bits fauna, but unknown in correlative marine faunas. Although Ptychotrygon occurs in all Western Interior, Gulf and Atlantic Coastal Plain faunas, it is represented elsewhere by apparently endemic species at each collection site. The differences between Western Interior, Gulf, and Atlantic Coastal Plain faunas probably reflect latitudinal variation in water temperature or salinity, or different oceanic water circulation patterns between the Western Interior Seaway and the Gulf or Atlantic Coast that restricted the distributions of some marine fish species. The Ten Bits fauna shares typical species with both Western Interior and Gulf and Atlantic Coast faunas, reflecting its position at the border between these provinces; however, the dominant taxa found at Ten Bits are the same as those found on the Gulf and Atlantic Coast, and indicate that western Texas was more closely allied biogeographically with that province than with the Western Interior of North America. One species tentatively identified in the Ten Bits fauna on the basis of a single tooth, Igdabatis cf. I. indicus, is otherwise known only from southern Europe and Asia, although a similar large myliobatid ray also occurs rarely in Texas Coastal Plain faunas. These occurrences indicate that western Texas may have been near the northern limit of the range for some tropical Tethyan marine vertebrate species.

USING MULTI-FORAMINIFERAL-PROXIES TO RESOLVE THE PALEOGEOGRAPHIC HISTORY OF A LOWER MIOCENE, SUBDUCTION-RELATED, SEDIMENTARY BASIN (WAITEMATA BASIN, NEW ZEALAND)

A combination of five techniques was used to infer the paleobathymetry and paleoecology of 103 foraminiferal faunas (>63μm, census counts of 384 benthic species) from throughout the lower Miocene Waitemata Basin, Auckland, northern New Zealand. A canonical correspondence analysis ordination showed that environmental factors related to paleo-bathymetry were the main drivers of benthic foraminiferal composition and samples were sorted in approximate paleo-depth order using increasing planktic percentage and species diversity proxies. Cluster analysis recognised seven associations (A–G) and eight subassociations, which were interpreted in terms of paleo-bathymetry and paleoproductivity by qualitative comparison with modern faunas. Planktic-percentage-based regression (with benthic stress-indicator taxa removed) and a Modern Analogue Technique comparison (at generic level) of fossil benthic assemblages with a modern dataset (626 faunas from 0–5000 m) were both used to provide quantitative paleo-bathymetry estimates for each Miocene fauna. These paleo-depth estimates were refined using the upper- and lower-depth limits of some of the less common benthics present. No one technique appears to be better than others. All can provide anomalous paleo-bathymetric estimates that need to be explained. Paleo-depth estimates are most consistent and precise for inner–mid shelf faunas and become less precise and more frequently inconsistent with increasing depth. A number of faunas with inconsistent paleo-bathymetric estimates contain both shallow- and deep-water-restricted benthic tests. These are interpreted as resulting from the inclusion of reworked deep-water fossil tests into shallow faunas, or mixing of contemporaneous tests as sediment flowing from shelf depths down into the basin in turbidity currents and debris flows. The eight bathyal–abyssal associations and subassociations have overlapping depth ranges but only 3–4 of them were present in the basin at any one time. Their geographic distribution reflects a crude depth-related zonation, whereas their stratigraphic succession is inferred to have resulted from a period of increased carbon flux and decreased bottom oxygen sandwiched between periods of lower carbon flux and more oxic bottom conditions. The recognised associations are: A, Elphidium , intertidal–subtidal beach; B, Nonionella-Notorotalia , sheltered inner shelf; C, Amphistegina-Cibicides , exposed inner–outer shelf; D, Astrononion-Gyroidina , ≥mid-bathyal; E, Bolivina , mid–lower bathyal; F, Cibicides-Bolivina , bathyal; G, Oridorsalis-Neugeborina-Pullenia , ≥lower bathyal. The inferred paleoenvironment of the faunas is used to help resolve the paleogeographic history of the Waitemata Basin. Thin basal transgressive sequences of lensing conglomerate, shelly sandstone and limestone containing shelf faunas (Assocs A–C) record initiation of basin subsidence over a wide area (300 × 100 km), ~21 Ma. Continued subsidence (estimated from foraminiferal data at ~1 mm/yr) was accompanied by sediment starvation with little or no sediment accumulating until the basin reached lower bathyal depths (F, G). This created sufficient slope for turbidity currents from the north to flow down submarine canyons and deposit three interfingering submarine fans of sandstone (800–1000 m thick). Displaced Cretaceous–Oligocene nappes and melange (Northland Allochthon) moved part way into the basin from the north and large sub-seafloor slides of mixed basinal sediment and allochthon slid off its advancing toe. These slides were triggered by uplift of the northern part of the basin, which created land fringed by a wide shelf (C). A large submarine stratovolcano built up on the west side of the basin and shed volcaniclastic sediment (C, D, F) down its eastern slopes with some debris flows transporting mixed shallow water faunas up to 30 km into the basin. The ~4 million-year-life of this subduction-related basin came to an end with complete eversion before the end of the early Miocene.

A review of contemporary patterns of endemism for shallow water reef fauna in the Red Sea

AbstractAimThe Red Sea is characterised by a unique fauna and historical periods of desiccation, hypersalinity and intermittent isolation. The origin and contemporary composition of reef‐associated taxa in this region can illuminate biogeographical principles about vicariance and the establishment (or local extirpation) of existing species. Here we aim to: (1) outline the distribution of shallow water fauna between the Red Sea and adjacent regions, (2) explore mechanisms for maintaining these distributions and (3) propose hypotheses to test these mechanisms.LocationRed Sea, Gulf of Aden, Arabian Sea, Arabian Gulf and Indian Ocean.MethodsUpdated checklists for scleractinian corals, fishes and non‐coral invertebrates were used to determine species richness in the Red Sea and the rest of the Arabian Peninsula and assess levels of endemism. Fine‐scale diversity and abundance of reef fishes within the Red Sea were explored using ecological survey data.ResultsWithin the Red Sea, we recorded 346 zooxanthellate and azooxanthellate scleractinian coral species of which 19 are endemic (5.5%). Currently 635 species of polychaetes, 211 echinoderms and 79 ascidians have been documented, with endemism rates of 12.6%, 8.1% and 16.5% respectively. A preliminary compilation of 231 species of crustaceans and 137 species of molluscs include 10.0% and 6.6% endemism respectively. We documented 1071 shallow fish species, with 12.9% endemic in the entire Red Sea and 14.1% endemic in the Red Sea and Gulf of Aden. Based on ecological survey data of endemic fishes, there were no major changes in species richness or abundance across 1100 km of Saudi Arabian coastline.Main conclusionsThe Red Sea biota appears resilient to major environmental fluctuations and is characterized by high rates of endemism with variable degrees of incursion into the Gulf of Aden. The nearby Omani and Arabian Gulfs also have variable environments and high levels of endemism, but these are not consistently distinct across taxa. The presence of physical barriers does not appear to explain species distributions, which are more likely determined by ecological plasticity and genetic diversity.

Fenxiang biota: a new Early Ordovician shallow-water fauna with soft-part preservation from China

Our perception of biodiversity in the geological past is incomplete and biased because most organisms did not have mineralized skeletons and therefore had little chance of fossilization. This especially refers to shallow-water marine environments, rarely represented by localities with exceptional preservation of fossil material (known as taphonomic windows or Konservat-Lagerstätten). Such extraordinary “windows” may markedly broaden our knowledge of biodiversity of the past. Here, we show a review of the invertebrate fossils from recently discovered locality in the Lower Ordovician Fenxiang Formation of Hubei Province in southern China revealing exceptional preservation of soft tissues. The fauna, generally of shallow-water aspect, contains linguloid brachiopods with a remarkably preserved pedicle, the oldest traces of nematode life activities, the oldest reliable record of hydroids, the first fossil antipatharian corals, a pyritized colonial organism of unknown affinity, supposed arthropod appendages, probable phosphatized scalidophoran worm embryo and other fossils. Our discovery supports the opinion that the famous soft-bodied preservation of Burgess Shale- or Chengjiang-type did not vanish from the fossil record in post-Cambrian times. The new finding represents a prelude to the Great Ordovician Biodiversification Event and provides evidence for calibration of molecular clock of several invertebrate lineages.

The metabolic cost of developing under hydrostatic pressure: experimental evidence supports macroecological pattern

Hydrostatic pressure is the most constant physical parameter on Earth. It increases linearly with water depth and is stable over evolutionary timescales. Despite this, bathymetric shifts in physiological adaptations that are observed in marine invertebrates (eg in metabolic rate and egg size) are currently interpreted to result predominantly from decreases in temperature. However, analysis of invertebrate egg size data presented here indicates an increase in egg volume with depth in the absence of a thermal gradient. This suggests hydrostatic pressure may also be important in determining resource allocation to offspring. In order to test the hypothesis that an increase in energy expenditure during development occurs with increasing depth, we examined the effect of sustained exposure to pressure (1, 100, 200 and 300 atm) on development of a shallow-water marine gastropod, Buccinum undatum. Embryos developed successfully at 1, 100 and 200 atm, but the rate of development slowed with increasing pressure (by 3 days at 100 atm and 6 days at 200 atm). No development was observed at 300 atm. In embryos reared at 200 atm, veliger dry weight and carbon and nitrogen biomass were significantly reduced. These results indicate that high pressure significantly increases the metabolic cost associated with development, demonstrating a negative and ultimately critical effect. We hypothesise that pressure imposes increased metabolic cost on all physiological processes. This offers an additional explanation for physiological adaptations observed with increasing depth, indicating that hydrostatic pressure is an important and previously underestimated factor contributing to metabolic theory for approximately 99% of our biosphere. This may represent a critical physiological bottleneck for the maximum depth distribution of shallow-water fauna.

The effects of changing climate on faunal depth distributions determine winners and losers.

Changing climate is predicted to impact all depths of the global oceans, yet projections of range shifts in marine faunal distributions in response to changing climate seldom evaluate potential shifts in depth distribution. Marine ectotherms' thermal tolerance is limited by their ability to maintain aerobic metabolism (oxygen- and capacity-limited tolerance), and is functionally associated with their hypoxia tolerance. Shallow-water (<200 m depth) marine invertebrates and fishes demonstrate limited tolerance of increasing hydrostatic pressure (pressure exerted by the overlying mass of water), and hyperbaric (increased pressure) tolerance is proposed to depend on the ability to maintain aerobic metabolism, too. Here, we report significant correlation between the hypoxia thresholds and the hyperbaric thresholds of taxonomic groups of shallow-water fauna, suggesting that pressure tolerance is indeed oxygen limited. Consequently, it appears that the combined effects of temperature, pressure and oxygen concentration constrain the fundamental ecological niches (FENs) of marine invertebrates and fishes. Including depth in a conceptual model of oxygen- and capacity-limited FENs' responses to ocean warming and deoxygenation confirms previous predictions made based solely on consideration of the latitudinal effects of ocean warming (e.g. Cheung et al., 2009), that polar taxa are most vulnerable to the effects of climate change, with Arctic fauna experiencing the greatest FEN contraction. In contrast, the inclusion of depth in the conceptual model reveals for the first time that temperate fauna as well as tropical fauna may experience substantial FEN expansion with ocean warming and deoxygenation, rather than FEN maintenance or contraction suggested by solely considering latitudinal range shifts.