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Oceans

Oceans is an international, peer-reviewed, open access journal of oceanography, published bimonthly online by MDPI.

Quartile Ranking JCR - Q3 (Marine and Freshwater Biology | Oceanography)

All Articles (277)

Annotated Checklist and Biodiversity of Sea Cucumbers (Holothuroidea) in Indian Waters

  • Karthika Padmini,
  • Ameen Ummath and
  • Atikulla Shaikh
  • + 1 author

Holothuroids play a vital role in nutrient cycling and bioturbation to enhance the marine ecosystem. They enhance the biodiversity for various symbiotic marine organisms by providing essential shelter and spawning grounds. This review focuses on the Class Holothuroidea (Phylum Echinodermata) in Indian waters, encompassing a total of 187 species organized into 7 orders and 21 families. Notably, the order Holothuriida represents the largest proportion of species, accounting for 27%. These species are well-distributed across India, with the Andaman and Nicobar Islands exhibiting the highest level of species richness (107 species), followed by the East Coast (102 species), Lakshadweep (39 species), and the West Coast (34 species). Species diversity was assessed using the Shannon–Weiner diversity index. Results indicate that the Andaman and Nicobar Islands (H’ = 2.23) and the West Coast (H’ = 2.14) demonstrate the highest levels of diversity. This review provides a comprehensive and precise inventory of all species of Holothuroidea reported in Indian waters, which is provided to facilitate understanding of the reported species, their systematics, and distribution. In addition, a significant insight for both conservation and management of sea cucumbers in India has also been provided.

18 December 2025

Map showing the Location of the West Coast, the East Coast, the Andaman and Nicobar Islands, and the Lakshadweep in India. Stars indicate the coastal cities of India.
  • Feature Paper
  • Article
  • Open Access

Τhe trophic ecology of Pterois miles in the Mediterranean Sea was performed by integrating data from stomach contents (SCA) and stable isotopes analyses (SIA), based on samples caught off the Greek island of Rhodes, SE, Aegean Sea, for the first time. This combined approach provides information on ingested (SCA) and assimilated (SIA) food and thus allows for the depiction of predator–prey relationships. Specimens of devil firefish, including both juveniles and adults (total length of analyzed specimens spanned from 11.40 to 31.50 cm), were collected from different sites around Rhodes. Their diet consisted of bony fish, cephalopods, crustaceans, and gastropods. The δ13C and δ15N values ranged from −18.0 ‰ to −14.4 ‰ and from 7.2 ‰ to 9.2 ‰, respectively. SIA data allowed for the estimation of the trophic position of devil firefish from Rhodes Island, which showed a mean value of 3.1 ± 0.6 and confirms that the species primarily relies on a benthic baseline. Further, our isotopic values approach those obtained in North Carolina and Bermuda, confirming its role as a mesopredator in the Mediterranean benthic food webs. Although preliminary, such results can provide an important baseline for future investigations on the species and the potential impact on the Mediterranean food webs.

12 December 2025

Map of sampling sites around the island of Rhodes in Greece. The five sampling sites are depicted with black dots (S1: Kritika; S2: Kritika; S3: Faliraki; S4: Afandou; S5: Plimmiri).

Cape Town, South Africa, experiences coastal upwelling during austral summer. In this study, the effects of kinematic and thermal ‘roughness’ on wind stress are analyzed using 5–25 km resolution multi-satellite and coupled reanalysis datasets in the period 2010–2024. Average conditions for austral summer (December–February) are calculated to identify east–west gradients in sensible heat flux, wave height, and equatorward winds and to assess their consequences for the drag coefficient, wind-driven Ekman transport, and entrainment over the shelf from 16.9 to 18.7° E, north of Cape Town (33.7° S). Statistical and numerical outcomes are compared for austral summer and during active coastal upwelling in January 2018 with chlorophyll concentrations > 3 mg/m3. A subtropical anticyclone generated shallow equatorward winds next to a wind shadow north of Cape Town. Sharp cross-shore gradients in momentum flux were amplified by shoreward reductions in sensible heat flux and wave height, which suppressed the drag coefficient 10-fold. The inclusion of kinematic and thermal roughness in wind stress calculations results in a higher average cyclonic curl (−2.4 × 10−6 N/m3), which translates into vertical entrainment > 3 m/day at 33.7° S, 18° E. The research links coastal upwelling leeward of a mountainous cape with cross-shore gradients in air–sea fluxes that support recirculation and phytoplankton blooms during austral summer.

9 December 2025

(a) The study area with elevation shaded, shelf edge (dashed isobaths −200 m, −400 m), and ERA5 summertime surface temperature < 15 °C (blue contours); locations: section (33.7°S), virtual buoy (dot 33.7° S, 18.2° E), weather station (square 33.0° S, 18.2° E), and airport sounding (triangle 34.0° S, 18.6° E); arrow indicates the prevailing 3 m wave direction, terrestrial roughness > 0.3 m (labelled). (b) Multi-satellite chlorophyll concentration maps (green shaded mg/m3) for January 2016 and January 2018 (right) with average currents in the surface mixed layer (blue vector, key 0.1 m/s) and ERA5 surface air temperature (red contour > 23 °C) of the leeside thermal low.

Two new species of free-living marine nematodes were collected in the Yellow Sea, China, and they are described herein as Actinonema sinica sp. nov. and Comesoma zhangi sp. nov. Actinonema sinica sp. nov. is characterized by short cephalic setae; lateral differentiation consisting of a row of longitudinal sclerotized bars and beginning at the level of anterior third of the pharyngeal region; horn-shaped telamons; a curved rod-shaped gubernaculum; and an elongate conical tail with a smooth, pointed tip. Comesoma zhangi sp. nov. is characterized by long, thick cephalic setae, reaching up to 28 µm in length; a cup-shaped buccal cavity lacking a tooth and narrowing posteriorly with small projections; an amphidial fovea with two turns; slender, arcuate spicules 2.6 times the cloacal body diameter in length, lacking a proximal capitulum; a plate-like gubernaculum without apophysis; and the absence of precloacal supplements. Updated keys to the valid species of the genus Actinonema and the genus Comesoma are provided. A comparative morphological table of all currently accepted species of Comesoma is also provided.

3 December 2025

Line drawings of Actinonema sinica sp. nov. (a) Lateral view of the holotype anterior end, showing the cephalic setae, amphid, and buccal cavity tooth; (b) Lateral view of the holotype cloacal region, showing the telamon and gubernaculum; (c) Entire view of a female; (d) Entire view of the holotype. Scale bars: (a,b) = 10 μm; (c,d) = 30 μm.

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Feature Papers of Oceans 2024
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Feature Papers of Oceans 2024

Editors: Alexander Werth, João Silva
The Future of Coral Reefs
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The Future of Coral Reefs

Research Submitted to ICRS 2020, Bremen, Germany
Editors: Rupert Ormond, Peter Schupp

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Oceans - ISSN 2673-1924