scholarly journals Comparative Reproductive Biology of Deep-Sea Ophiuroids Inhabiting Polymetallic-Nodule Fields in the Clarion-Clipperton Fracture Zone

2021 ◽  
Vol 8 ◽  
Author(s):  
Sven R. Laming ◽  
Magdalini Christodoulou ◽  
Pedro Martinez Arbizu ◽  
Ana Hilário
Keyword(s):  
Reproductive Biology ◽  
Fracture Zone ◽  
Deep Sea ◽  
Sex Ratios ◽  
Reproductive Mode ◽  
Environmental Drivers ◽  
Polymetallic Nodule ◽  
Clipperton Fracture Zone ◽  
Domains Of Life ◽  
Clarion Clipperton Fracture Zone

Deep-sea mining in the Pacific Clarion-Clipperton Fracture Zone (CCZ), a low-energy sedimentary habitat with polymetallic nodules, is expected to have considerable and long-lasting environmental impact. The CCZ hosts extraordinarily high species diversity across representatives from all Domains of Life. Data on species biology and ecology remain scarce, however. The current study describes the reproductive biology of Ophiosphalma glabrum (Ophiosphalmidae) and Ophiacantha cosmica (Ophiacanthidae), two ophiuroids frequently found in the CCZ. Specimens collected in Spring 2015 and 2019 in four contract areas were examined morphologically and histologically. Size-class frequencies (disc diameter and oocytes feret diameters), sex ratios, gametogenic status, putative reproductive mode, and a simple proxy for fecundity are presented. Habitat use differs in each. While O. glabrum is epibenthic, occurring as single individuals, O. cosmica often forms size-stratified groups living on stalked sponges, suggesting gregarious settlement or retention of offspring (though no brooding individuals were found). Further molecular analyses are needed to establish whether O. cosmica groups are familial. In O. glabrum, for which sample sizes were larger, sex ratios approximated a 1:1 ratio with no size-structuring. In both species, individuals were at various stages of gametogenic maturity, but no ripe females were identified. Based on this, O. glabrum is most probably gonochoric. Reproductive mode remains inconclusive for O. cosmica. Both species are presumptively lecithotrophic, with vitellogenic-oocyte feret diameters exceeding 250 μm. Oocyte feret diameters at times exceeded 400 μm in O. glabrum, indicating substantial yolk reserves. Estimates of instantaneous fecundity (vitellogenic specimens of O. glabrum only) were confounded by interindividual variability in gonad characteristics. The well-furnished lecithotrophic larvae of O. glabrum would be capable of dispersing even under food-impoverished conditions. The current study examines ophiuroid reproductive biology over multiple localities in the CCZ concurrently for the first time, at sites characterised by differing productivity regimes. The reproductive biology of each species is thus discussed with reference to past evolutionary (habitat stability), contemporary (food supply), and future environmental drivers (potential impacts of deep-sea mining).

scholarly journals Comparative reproductive biology of deep-sea ophiuroids inhabiting polymetallic-nodule fields in the Clarion-Clipperton Fracture Zone

2021 ◽  
Author(s):  
Sven R Laming ◽  
Magdalini Christodoulou ◽  
Pedro Martinez Arbizu ◽  
Ana Hilário
Keyword(s):  
Reproductive Biology ◽  
Fracture Zone ◽  
Deep Sea ◽  
Sex Ratios ◽  
Reproductive Mode ◽  
Environmental Drivers ◽  
Polymetallic Nodule ◽  
Clipperton Fracture Zone ◽  
Domains Of Life ◽  
Clarion Clipperton Fracture Zone

AbstractDeep-sea mining in the Pacific Clarion-Clipperton Fracture Zone (CCZ), a low-energy sedimentary habitat with polymetallic nodules, is expected to have considerable and long-lasting environmental impact. The CCZ hosts extraordinarily high species diversity in nearly all domains of Life present. Data on species biology and ecology remain scarce, however. The current study describes the reproductive biology of Ophiosphalma glabrum (Lütken & Mortensen, 1899) (Ophiosphalmidae) and Ophiacantha cosmica (Lyman, 1878) (Ophiacanthidae), two ophiuroids frequently found in the CCZ. Specimens collected in Spring 2015 and 2019 in four contract areas (BGR, IOM, GSR, Ifremer) and one Area of Particular Interest (APEI 3) were examined morphologically and histologically. Size-class frequencies (disc diameter and oocytes feret diameters), sex ratios, gametogenic status, putative reproductive mode and a simple proxy for fecundity are presented. Habitat use differs in each. While O. glabrum is epibenthic, occurring as single individuals, O. cosmica often form size-stratified groups living on stalked sponges, suggesting gregarious settlement or retention of offspring (though no brooding individuals were found). Further molecular analyses are needed to establish whether O. cosmica groups are familial. In O. glabrum, for which sample sizes were larger, sex ratios approximated a 1:1 ratio with no size-structuring. In both species, individuals were at various stages of gametogenic maturity but no ripe females were identified. Based on this, O. glabrum is most probably gonochoric. Reproductive mode remains inconclusive for O. cosmica. Both species are presumptively lecithotrophic, with vitellogenic-oocyte feret diameters exceeding 250 µm. Oocyte feret diameters at times exceeded 400 µm in O. glabrum, indicating substantial yolk reserves. Estimates of instantaneous fecundity (vitellogenic specimens of O. glabrum only) were confounded by interindividual variability in gonad characteristics. The well-furnished lecithotrophic larvae of O. glabrum would be capable of dispersing even under food-impoverished conditions. The current study examines ophiuroid reproductive biology over multiple localities in the CCZ concurrently for the first time, at sites characterised by differing productivity regimes. The reproductive biology of each species is thus discussed with reference to past evolutionary (habitat stability), contemporary (food supply) and future environmental drivers (potential impacts of deep-sea mining).

scholarly journals Are seamounts refuge areas for fauna from polymetallic nodule fields?

2019 ◽  
Author(s):  
Daphne Cuvelier ◽  
Pedro A. Ribeiro ◽  
Sofia P. Ramalho ◽  
Daniel Kersken ◽  
Pedro Martinez Arbizu ◽  
...  
Keyword(s):  
Fracture Zone ◽  
Deep Sea ◽  
Soft Sediment ◽  
Sea Floor ◽  
Polymetallic Nodule ◽  
Refuge Area ◽  
Clipperton Fracture Zone ◽  
Clarion Clipperton Fracture Zone ◽  
Refuge Areas ◽  
Hard Substrata

Abstract. Seamounts are abundant and prominent features on the deep-sea floor and intersperse with the nodule fields of the Clarion-Clipperton Fracture Zone (CCZ). There is a particular interest in characterising the fauna inhabiting seamounts in the CCZ because they are the only other ecosystem in the region to provide hard substrata besides the abundant nodules on the soft sediment abyssal plains. It has been hypothesised that seamounts could provide refuge for organisms during deep-sea mining actions or that they could play a role in the (re-)colonisation of the disturbed nodule fields. This hypothesis is tested by analysing video transects in both ecosystems, assessing megafauna composition and abundance. Nine video transects (ROV dives) from two different license areas and one Area of Particular Environmental Interest in the eastern CCZ were analysed. Four of these transects were carried out as exploratory dives on four different seamounts in order to gain first insights in megafauna composition. The five other dives were carried out in the neighbouring nodule fields in the same areas. Variation in community composition observed among and along the video transects was high, with little morphospecies overlap on intra-ecosystem transects. Despite these observations of considerable faunal variations within each ecosystem, differences between seamounts and nodule fields prevailed, showing significantly different species associations characterising them, thus questioning their use as a possible refuge area.

scholarly journals Are seamounts refuge areas for fauna from polymetallic nodule fields?

2020 ◽  
Vol 17 (9) ◽  
pp. 2657-2680 ◽  
Author(s):  
Daphne Cuvelier ◽  
Pedro A. Ribeiro ◽  
Sofia P. Ramalho ◽  
Daniel Kersken ◽  
Pedro Martinez Arbizu ◽  
...  
Keyword(s):  
Fracture Zone ◽  
Deep Sea ◽  
Soft Sediment ◽  
Sea Floor ◽  
Polymetallic Nodule ◽  
Refuge Area ◽  
Clipperton Fracture Zone ◽  
Clarion Clipperton Fracture Zone ◽  
Refuge Areas ◽  
Hard Substrata

Abstract. Seamounts are abundant and prominent features on the deep-sea floor and intersperse with the nodule fields of the Clarion-Clipperton Fracture Zone (CCZ). There is a particular interest in characterising the fauna inhabiting seamounts in the CCZ because they are the only other ecosystem in the region to provide hard substrata besides the abundant nodules on the soft-sediment abyssal plains. It has been hypothesised that seamounts could provide refuge for organisms during deep-sea mining actions or that they could play a role in the (re-)colonisation of the disturbed nodule fields. This hypothesis is tested by analysing video transects in both ecosystems, assessing megafauna composition and abundance. Nine video transects (ROV dives) from two different license areas and one Area of Particular Environmental Interest in the eastern CCZ were analysed. Four of these transects were carried out as exploratory dives on four different seamounts in order to gain first insights into megafauna composition. The five other dives were carried out in the neighbouring nodule fields in the same areas. Variation in community composition observed among and along the video transects was high, with little morphospecies overlap along intra-ecosystem transects. Despite the observation of considerable faunal variations within each ecosystem, differences between seamounts and nodule fields prevailed, showing significantly different species associations characterising them, thus calling into question their use as a possible refuge area.

scholarly journals Physical and hydrodynamic properties of deep sea mining-generated, abyssal sediment plumes in the Clarion Clipperton Fracture Zone (eastern-central Pacific)

Elem Sci Anth ◽  
2019 ◽  
Vol 7 ◽  
Author(s):  
Benjamin Gillard ◽  
Kaveh Purkiani ◽  
Damianos Chatzievangelou ◽  
Annemiek Vink ◽  
Morten H. Iversen ◽  
...  
Keyword(s):  
Fracture Zone ◽  
Deep Sea ◽  
Transport Model ◽  
Dry Weight ◽  
In Situ Tests ◽  
Central Pacific ◽  
Polymetallic Nodule ◽  
Clipperton Fracture Zone ◽  
Clarion Clipperton Fracture Zone ◽  
Nodule Mining

The anthropogenic impact of polymetallic nodule harvesting in the Clarion-Clipperton Fracture Zone is expected to strongly affect the benthic ecosystem. To predict the long-term, industrial-scale impact of nodule mining on the deep-sea environment and to improve the reliability of the sediment plume model, information about the specific characteristics of deep-sea particles is needed. Discharge simulations of mining-related fine-grained (median diameter ≈ 20 μm) sediment plumes at concentrations of 35–500 mg L–1 (dry weight) showed a propensity for rapid flocculation within 10 to 135 min, resulting in the formation of large aggregates up to 1100 μm in diameter. The results indicated that the discharge of elevated plume concentrations (500 mg L–1) under an increased shear rate (G ≥ 2.4 s–1) would result in improved efficiency of sediment flocculation. Furthermore, particle transport model results suggested that even under typical deep-sea flow conditions (G ≈ 0.1 s–1), rapid deposition of particles could be expected, which would restrict heavy sediment blanketing (several centimeters) to a smaller fall-out area near the source, unless subsequent flow events resuspended the sediments. Planning for in situ tests of these model projections is underway.

scholarly journals Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Carlos Muñoz-Royo ◽  
Thomas Peacock ◽  
Matthew H. Alford ◽  
Jerome A. Smith ◽  
Arnaud Le Boyer ◽  
...  
Keyword(s):  
Fracture Zone ◽  
Deep Sea ◽  
Environmental Concern ◽  
Field Studies ◽  
Research Activity ◽  
Polymetallic Nodule ◽  
Commercial Scale ◽  
Clipperton Fracture Zone ◽  
Clarion Clipperton Fracture Zone ◽  
Nodule Mining

AbstractDeep-sea polymetallic nodule mining research activity has substantially increased in recent years, but the expected level of environmental impact is still being established. One environmental concern is the discharge of a sediment plume into the midwater column. We performed a dedicated field study using sediment from the Clarion Clipperton Fracture Zone. The plume was monitored and tracked using both established and novel instrumentation, including acoustic and turbulence measurements. Our field studies reveal that modeling can reliably predict the properties of a midwater plume in the vicinity of the discharge and that sediment aggregation effects are not significant. The plume model is used to drive a numerical simulation of a commercial-scale operation in the Clarion Clipperton Fracture Zone. Key takeaways are that the scale of impact of the plume is notably influenced by the values of environmentally acceptable threshold levels, the quantity of discharged sediment, and the turbulent diffusivity in the Clarion Clipperton Fracture Zone.

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