Bathyal Sea Research Articles

Trophic ecology, diet and feeding behaviour of three bathyal sea anemones (Actiniaria: Cnidaria) in the Northwest Atlantic

Sea anemones are often presented as a major component of benthic communities and described as ecologically important in benthic food webs. However, studies on the trophic ecology of deep-sea species are rare. Here, the feeding habits and dietary sources of three species of bathyal sea anemones (Actinostola callosa, Actinauge cristata, Urticina sp.) from the Northwest Atlantic were studied in a multi-faceted approach including stable isotopes, gastrovascular contents, lipid and fatty acids analysis and observations in a mesocosm. Stable isotope analysis showed that A. callosa sits at a slightly lower trophic level than A. cristata and Urticina sp. and that the two latter species rely on different carbon sources at roughly the same trophic level. The gastrovascular cavity contents and mesocosm study revealed that all three species ingest a variety of food items, from inorganic materials to a diversity of metazoans, including whole large prey. Total lipid content varied across species and was highest in Urticina sp. Phospholipids constituted the main lipid class in all three species, with consistently high levels of wax ester storage lipids. All sea anemones were also characterized by high proportions of mono and polyunsaturated fatty acids (MUFA and PUFA) as well as ω3 and ω9 FAs, and strikingly low proportions of 20:4ω6 (ARA). High values of 20:5ω3 (EPA), 20:1ω9 and 22:1ω11(13) evoke a diet centered on zooplankton, with notable particularities. For instance, Urticina sp. had the highest PUFA to saturated FAs ratio, indicative of carnivory. Overall, results suggest that the three sea anemone species occupy different niches in the spectrum of opportunistic polyphagous predation/feeding, with Urticina sp. relying chiefly on more energetic and larger prey and A. cristata targeting smaller zooplankton, foraminifera and particulate food, highlighting that large actinians play diverse roles in benthic food webs.

The Cenozoic sedimentary environment and sedimentary filling evolution of Wan'an Basin in the western South China Sea

As one of the basins with extremely abundant oil and gas resources in South China Sea, the Wan'an Basin has attracted great attention from domestic and international geologists and hydrocarbon explorers. Currently, the sequence stratigraphic framework, distribution of sedimentary systems and sedimentary filling evolution of the Wan'an Basin are still not clear, consequently, it bring some difficulties for hydrocarbon exploration. Based on the palaeobios, well drilling, well logging, and seismic and other data, the sequence stratigraphic framework of the Wan'an Basin is established, and the sequence interfaces of T100, T60, T50, T40 and T30 in this study are identified. On this basis, the sedimentary environment and sedimentary filling evolution of the Wan'an Basin are systematically analyzed. The results show that the basin had experienced three tectonic evolution periods since Cenozoic, i.e., the Oligocene–Early Miocene extensional fault-depression period, Middle Miocene strike-slip reformation period and Late Miocene–Quaternary regional depression period. Thereinto, the provenance in the extensional fault-depression period (Oligocene–Early Miocene) was mainly from the western uplift of the basin, where the delta–shore-shallow lacustrine–bathylimnetic sedimentary system during Early Oligocene and delta–littoral-neritic sedimentary system during Late Oligocene–Early Miocene were developed respectively. The provenance during the strike-slip reformation period (Middle Miocene) was still mainly from the western uplift of the basin, where the delta–littoral-neritic–carbonate platform sedimentary system was developed, and the carbonate platform began to develop abundantly. The provenance during the regional depression period (Late Miocene–Quaternary) is mainly supplied by input of the western distal large rivers, the delta–littoral-shallow sea–carbonate platform–bathyal sea sedimentary system was developed in the Late Miocene, and the shelf-margin delta–continental slope–bathyal sea sedimentary system was developed during Pliocene-Quaternary. Therefore, the Wan'an Basin has a favorable hydrocarbon resource potential.

Sedimentary evolution of Neoproterozoic rift basin in northern Tarim

Based on the outcrop, drilling and seismic data, the sedimentary successions, evolution and hydrocarbon exploration potential of the Neoproterozoic rift basin in the northern Tarim were firstly analyzed. Due to assembly and breakup of the Rodinia supercontinent, the Tabei paleocontinent and the Tarim paleocontinent were developed in the Tarim craton with an EW-trending back-arc rift basin between them during Neoproterozoic time; very thick marine clastic rocks, carbonate rocks and volcanic rocks (including tillite) were deposited in the Kuruktag and Aksu area of the northern Tarim, which experienced deep sea, bathyal sea and littoral sea environments with transitional delta and ice-sea. During the Early Cryogenian and the Late Ediacaran, the northern rift basin evolved from the deep sea to the littoral-neritic sea, while the lithology changed from clastic rocks to carbonate rocks. According to the field and production data, the formation and preservation of the source rocks and reservoirs indicate a good exploration potential of the Neoproterozoic rift basin.

Sublittoral and bathyal sea cucumbers (Echinodermata: Holothuroidea) from the Northern Mozambique Channel with description of six new species.

The 2009 expedition with the research vessel Miriky sampled the sublittoral and bathyal waters of the northern Mozambique Channel. This exploration campaign resulted in a small, but very diverse collection of holothuroids comprising 174 specimens representing 31 species, 18 genera, 10 families and 5 orders. Of these species, many were hitherto unknown for Madagascar or even for the Indian Ocean, and six, Bathyplotes aymeric sp. nov., Holothuria (Cystipus) yann sp. nov., Holothuria (Stauropora) bo sp. nov., Holothuria (Metriatyla) alex sp. nov., Holothuria (Theelothuria) cyrielle sp.nov., Molpadia thandari sp. nov., are new to science. Molpadia lenticulum (Cherbonnier & Féral, 1981) is a new combination. This contribution provides an illustrated and annotated overview of the poorly known, highly biodiverse, sublittoral and bathyal sea cucumber fauna of the northern Mozambique Channel. Our findings demonstrate how ignorant we are about the poorly explored habitats of our planet and therefore stress the urgent need for more explorations to such regions.

Reconstruction of the Triassic Tectonic Lithofacies Paleogeography in Qiangtang Region, Northern Qinghai‐Tibet Plateau, China

Abstract:The Triassic petrostratigraphic system and chronologic stratigraphic sketch have been updated and perfected in the Qiangtang area, Qinghai‐Tibet Plateau based on the integrated 1:250000 regional geological survey and the latest research progeny. The first finished 1:3000000 Triassic tectonic lithofacies paleogeographic maps in the Qiangtang area shows that the Triassic tectonic unit in the Qiangtang area can been divided into three parts from north to south: northern Qiangtang block; Longmucuo‐Shuanghu suture zone; and southern Qiangtang block.The early‐middle Triassic tectonic paleogeography in the Qiangtang area is divides into three sub‐units: northern Qiangtang passive continental marginal basin (NQPB), Longmucuo‐ Shuanghu residual basin (LSRB) and southern Qiangtang residual basin (SQRB). The NQPB can be subdivided into four paleogeography units: The Tanggula‐Zangxiahe shallow and bathyal sea; The Wangquanhe‐Yingshuiquan carbonate platform; The Rejuechaka‐Jiangaidarina littoral‐ shallow sea; and Qiangtang central uplift. The above units of The NQPB possess EW trend, geomorphology high in the south and low in the north, the seawater depth northward. The basinal paleo‐current direction is unidirectional, and basinal tectonic subsidence center is in accord with the depo‐center, located in the Tanggula‐Zangxiahe belt, north of the basin. The sedimentation and tectonic evolution of the NQPB are characterized with passive continental marginal basin. The Qiangtang central orogenic denuded area (ancient land) may be as a sedimentary materials source of the NQPB. SQRB can be divided into two units: Duoma carbonate platform and southern Qiangtang neritic‐deep sea.The late Triassic tectonic paleogeography in the Qiangtang area is the framework of the “archipelagic‐sea” as a whole, and it may be divided into three sub‐units: northern Qiangtang back‐arc foreland basin(NQFB), Longmucuo‐Shuanghu residual basin(LSRB) and southern Qiangtang marginal‐sea basin(SQMB). Thereinto, NQFB can be divided into five paleogeography units: the Zangxiahe‐Mingjinghu bathyal basin characterized with the flysch; the Tanggula shallow‐sea shelf with the fine‐clastics; the Juhuashang platform with carbonates; the Tumenggela‐Shuanghu coastal‐delta with coal‐bearing clastics and the Nadigangri‐ Geladandong arc with volcanics and tuffs. In transverse section, the NQFB fills is wedge‐shaped, and the sediments characterized with thicker in north and thinner in south, and with double materials derived from the Ruolagangri orogenic belt in north and the Shuanghu central orogenic belt in south. The late Triassic depocenter of NQFB is located in the middle of the basin, the Yakecuo‐Bandaohu‐Quemocuo belt, but the subsidence center in the north, the Zangxiahe‐ Mingjinghu belt, and basinal tectonic subsidence center not concordant with the depo‐center. Late Triassic, the SQMB may be divided into three sub‐units: Xiaochaka shallow‐sea; Riganpeicuo platform; and South Qiangtang southern bathyal basin. In transverse section, the basement of the SQMB is characterized with low in the northern and southern, but high in the middle; forming wedge shaped sediments with thicker in the north and thinner in the south; the sedimentary materials derived from the Qiangtang central uplift and Nadigangri arcs in north. The late Triassic subsidence centre of the SQMB is located in the northern (Xiaochaka area), but the depocenter in the southern (Qixiancuo Suobucha area). The sedimentation and tectonic evolution of the SQMB are characterized with marginal sea.

Bathyal sea urchins of the Bahamas, with notes on covering behavior in deep sea echinoids (Echinodermata: Echinoidea)

In a survey of the bathyal echinoderms of the Bahama Islands region using manned submersibles, approximately 200 species of echinoderms were encountered and documented; 33 species were echinoids, most of them widespread in the general Caribbean area. Three species were found to exhibit covering behavior, the piling of debris on the upper surface of the body. Active covering is common in at least 20 species of shallow-water echinoids, but it has been reliably documented previously only once in deep-sea habitats. Images of covered deep-sea species, and other species of related interest, are provided. Some of the reasons adduced in the past for covering in shallow-water species, such as reduction of incident light intensity, physical camouflage, ballast in turbulent water, protection from desiccation, presumably do not apply in bathyal species. The main reasons for covering in deep, dark, environments are as yet unknown. Some covering behavior in the deep sea may be related to protection of the genital pores, ocular plates, or madreporite. Covering in some deep-sea species may also be merely a tactile reflex action, as some authors have suggested for shallow-water species.

Ovalidota milleri, a new genus and species of bathyal sea cucumber from the Caribbean Sea (Echinodermata: Holothuroidea: Apodida)

Ovalidota milleri, a new genus and species of bathyal sea cucumber from the Caribbean Sea (Echinodermata: Holothuroidea: Apodida)

Ovalidota milleri, a new genus and species of bathyal sea cucumber from the Caribbean Sea (Echinodermata: Holothuroidea: Apodida)

Ovalidota milleri new genus, new species, is a chiridotid holothurian with an egg-shaped body, a broad oral field surrounded by 18 19 (?20) tentacles, and body wall ossicles in the form of typical Chiridota wheels gathered into papillae and also scattered among the papillae. It is known from two localities in the Caribbean, near St. Vincent and at Grand Cayman Island, in bathyal depths of 366-414 metres. The egg-shaped body of this new genus is unique in the Order Apodida. When more material becomes available for study, Ovalidota milleri may be referred to a new family.

Global distribution of naturally occurring marine hypoxia on continental margins

Hypoxia in the ocean influences biogeochemical cycling of elements, the distribution of marine species and the economic well being of many coastal countries. Previous delineations of hypoxic environments focus on those in enclosed seas where hypoxia may be exacerbated by anthropogenically induced eutrophication. Permanently hypoxic water masses in the open ocean, referred to as oxygen minimum zones, impinge on a much larger seafloor surface area along continental margins of the eastern Pacific, Indian and western Atlantic Oceans. We provide the first global quantification of naturally hypoxic continental margin floor by determining upper and lower oxygen minimum zone depth boundaries from hydrographic data and computing the area between the isobaths using seafloor topography. This approach reveals that there are over one million km 2 of permanently hypoxic shelf and bathyal sea floor, where dissolved oxygen is <0.5 ml l −1; over half (59%) occurs in the northern Indian Ocean. We also document strong variation in the intensity, vertical position and thickness of the OMZ as a function of latitude in the eastern Pacific Ocean and as a function of longitude in the northern Indian Ocean. Seafloor OMZs are regions of low biodiversity and are inhospitable to most commercially valuable marine resources, but support a fascinating array of protozoan and metazoan adaptations to hypoxic conditions.

Correlating environmental changes during early Albian oceanic anoxic event 1B using benthic foraminiferal paleoecology

The nature and consequences of mid-Cretaceous oceanic anoxic events (OAEs) are the subject of ongoing debate, and recent studies have shown that different scenarios are needed to explain each of these events. Nevertheless, similarities between the different OAEs can be observed. Here, we have reconstructed paleoenvironmental changes during the early Albian OAE 1b using benthic foraminiferal distributions and lithologies in three sections from different basins and paleowater depths. Eutrophic conditions, as indicated by the presence of infaunal as well as opportunistic genera such as Gyroidinoides, Pseudobolivina, Pleurostomella and bolivinitids, prevailed before and during the OAE and led to dysoxic to anoxic conditions. Dysoxia was most intense in the bathyal sections but also occurred in the outer shelf where more heterogeneous patterns of foraminiferal distributions are believed to reflect fluctuations of the upper boundary of an oxygen-minimum zone. A change from eutrophic to mesotrophic conditions caused the termination of OAE 1b and opportunistic benthic foraminifera (e.g. Pseudobolivina, Pleurostomella) were the first to subsequently repopulate the bathyal sea floor. Repopulation occurred rapidly in the shallow settings and gradually in the deeper sites, where a normal, diverse pre-event fauna was established a few tens of thousands of years after OAE 1b.

Foraminiferal microhabitats in four marine environments around Japan

Microhabitats of benthic foraminifera are described from four environments typical of the Japanese Islands: the tidal zone of a rocky shore, a brackish bay, shallow sea, and bathyal sea. Many microenvironments exist around the sediment-water interface, providing a rich diversity of potential microhabitats for benthic foraminifera. Benthic foraminifera occupy the full range of potential life positions with respect to the sediment-water interface. There are attached epifaunal, free living epifaunal, shallow infaunal, and deep infaunal species. The distribution of individual species tends to be segregated by microhabitat preferences.

Larval phototaxis in barnacles and snails associated with bathyal sea urchins

Larvae of many shallow-water marine invertebrates show phototactic behaviors which may allow them to exercise some control over their positions in the water column. Such behavior should be useful only in regions where light provides a consistent directional cue and might not, therefore, be expected in species found exclusively in deep water where light levels are extremely low. In this paper, we investigated larval phototactic responses in two barnacle and one prosobranch gastropod species that occur epifaunally on tropical, bathyal sea urchins. Newly released larvae of the gastropod Pelseneeria sp. did not respond to light but Stage I nauplii of both barnacle species ( Verruca floridana and Paralepas pedunculata) showed strong positive phototaxis at light intensities greater than 2.66 μmol m −2s −1. Larvae are expected to encounter the threshold intensities at depths no greater than 90 m in Caribbean waters. As both barnacle species were collected at much greater depths, phototaxis (at least in the early larvae) should have little effect. The ability to detect and respond to light may foreshadow functional photoresponses in later larvae that move to shallower depths. Alternatively, the presence of photoreceptors and light responses may be interpreted as evidence that these barnacles, which now reside in the deep sea, may have originated in shallow water.

Ovarian ultrastructure and vitellogenesis in ten species of shallow-water and bathyal sea cucumbers (Echinodermata: Holothuroidea)

Comparative ultrastructural features of the ovary and vitellogenesis have been described for six shallow water and four bathyal species of sea cucumbers representing four major holothuroid orders. Ovarian structure is similar in all ten species except for features of the peritoneal cells of the outer layer and the follicular inner epithelial cells surrounding the developing oocytes. The peritoneal cells vary from monociliated squamous or cuboidal cells to large columnar cells. Ultrastructural evidence suggests that these cells might be capable of incorporating materials from the perivisceral coelom. The follicular inner epithelial cells of two deep-sea species resemble podocytes, a feature previously unre-ported in holothuroid ovaries. It is suggested that these cells function to increase nutrient exchange between the genital haemal sinus and the oocyte during vitellogenesis. In all ten species, the oocytes appear to participate in yolk synthesis through the interaction of the Golgi complex and rough endoplasmic reticulum. The similarity in the ultrastructural features of vitellogenesis suggests that the process of yolk synthesis has been highly conserved in holothuroids. Endocytotic activity was detected in seven of ten species but it is uncertain if this is directly related to vitellogenesis. Cilia and intracellular structures resembling striated ciliary rootlets were observed in the oocytes of four of the ten species studied. The significance of this finding is unclear but could indicate that germ cells have a somatic cell origin.

Ontogcnetic vertical migration in Sebastolobus altivelis as a mechanism for transport of particulate organic matter at continental slope depths

Ontogenetic vertical migration by a demersal fish inhabiting the continental slope off central California was studied as a mechanism for coupling transport of particulate matter between surface waters and the bathyal sea floor. We conducted a 1‐yr survey of Sebastolobus altivelis, a dominant demersal fish, over much of its depth range (400–1,600 m), with a camera sled and bottom trawl. This scorpaenid spawns gelatinous masses of eggs which float to the surface. After hatching, S. altivelis has a protracted pelagic phase and settles as a benthic juvenile at a length of ∼55 mm. We determined the production of particulate organic matter (POM) in masses of eggs as a measure of the passive upward flux of POM, and the recruitment of POM by settling juveniles as a measure of active transport back to the sea floor. Upward and downward fluxes of particulate organic carbon (POC) associated with planktonic development and ontogenetic migration of S. altivelis were 4.1–5.8 and 3.0–5.5 mg C m−2 yr−1. These upward and downward fluxes are lower by factors of ∼10 and ∼104 than the reported passive upward and downward fluxes measured with particulate interceptor traps in the eastern North Pacific. These data suggest that at bathyal depths, it is unlikely that vertical ontogenetic migrations contribute &gt;1% to the POC flux reaching the deep‐sea floor. The upward flux of POC as buoyant eggs could represent, however, a significant portion of the total upward flux.

Distribution and species diversity of deep-sea nematodes in the Venezuela Basin

Abstract In three sedimentary regions in the deep (>3400 m) Venezuela Basin, nematode abundance and dry weight biomass (ean ±1 S.E.) were higher in hemipelagic sediments (94 ± 1.5 individuals, 88 ± 2.5 μg per 10 cm−2) than in pelagic (67 ± 3 individuals, 32 ±33 μg per 10 cm−2) or turbidite (36 ± 3 individuals, 30 ± 3 μg per 10 cm−2) sediments. Abundance of nematodes appears to be at least partially related to geographic position within the basin; hemipelagic sediments lie closer to an area of elevated surface production near the Lesser Antilles than do the pelagic or turbidite sediments. Abundance of nematodes is also directly correlated with macrofauna abundance and presence of sedimentary lipids. Normal hierarchical classification indicates the presence of two faunal groups in the sediments: a ‘sand’ fauna in coarser pelagic sediments (median grain size, 65 μm) and a ‘silt-clay’ fauna in the finer hemipelagic and turbidite sediments (median grain size in both, 0.65 μm). Animals among the two faunal groups differ mostly in their feeding morphology: selective deposit feeding species, unable to utilize large, pelagically derived particles (mainly foraminiferan tests) are more abundant in finer hemipelagic and turbidite sediments, whereas species capable of rasping food particles off large sedimentary particles (epistrate feeders) are more abundant in pelagic sands than in finer sediments. Species diversity is higher in the hemipelagic than turbidite and pelagic sediments. Two reasons postulated for this are (1) the possible input of relatively fresh, surface-derived organic matter that might permit a large number of species to exist in hemipelagic sediments than in the other two, and (2) an optimally heterogeneous grain size distribution that might allow the species to coexist equitably. All three sediments support more diverse nematode assemblages than those in the North Carolina slope region, probably reflecting the greater physical stability of the abyssal than bathyal sea floor.