Healthy thalli of the invasive seaweed Rugulopteryx okamurae (Phaeophyceae) being massively dragged into deep-sea bottoms by the Mediterranean Outflow Water

Figures & data

Fig. 1. Map displaying the main deep currents and seafloor geomorphology of the Gulf of Cádiz, together with the coastal areas where Rugulopteryx okamurae has been detected from 2017 to 2019 according to García-Gómez et al. (2020), and sampling stations where R. okamurae was detected in the oceanographic expeditions of this study (including quantitative and semi-quantitative annotations using a rank system). Suspended thalli classification (1, 1.0–4.9; 2, 4.9–9.9; 3, 9.9–30 thalli min^–1); Settled thalli classification (1, 1.0%–14.9%; 2, 15.0%–29.9%; 3, 30.0%–74.9% of bottom coverage). References to figures are indicated on the map. The northern Spartel channel (NS), the southern Spartel channel (SS), the Cádiz channel (CA), the Huelva channel (HU) and the Gil Eanes channel (GE) are shown on the map. Black crosses indicate absence of R. okamurae. The digital bathymetric Model data products have been derived from the EMODnet Bathymetry portal – http://www.emodnet-bathymetry.eu. The main deep currents branches were obtained from Sánchez-Leal et al. (2017).

Figs 2–7. Information about sample collection, morphology and accumulations of Rugulopteryx okamurae thalli (black arrows) on the deep-sea floor and on benthic fauna.

Fig. 2. Thalli of R. okamurae collected with a beam trawl at 258 m depth.Fig. 3. Thallus and transversal cut showing the pluricellular margin (black arrow) characteristic of R. okamurae. This thallus is from a stock collected in beam trawls BT33-24 (36°19.92ʹN, 6°39.90ʹW; 258 m) and BT 11-49 (35°59.16ʹN, 6°57.12ʹW; 800 m) conducted during CIRCASUR 2020 expeditions. Scale bar thallus = 1 cm. Scale bar detail = 100 µm.Fig. 4. Accumulations of R. okamurae covering c. 65% of the seafloor at 628 m depth. Nep., Nephrops norvegicus; Mac., Macropipus sp.; Pla., plastic. Scale bar = 10 cm.Fig. 5. Accumulations of R. okamurae around Cidaris cidaris (Cid.) in a rippled bottom at 804 m depth. Scale bar = 10 cm.Fig. 6. Thalli of R. okamurae (Rug.) attached to the delicate bamboo coral Isidella elongata (Isi.) at 966 m depth. Scale bar = 10 cm.Fig. 7. Thalli of R. okamurae hooked on structuring hard bottom invertebrates at 804 m depth. Pha., Phakellia spp; Swi., Swiftia dubia; Aca., Acanthogorgia hirsuta. Scale bar = 10 cm.

Table 1. Photosynthetic parameters calculated from Chlorophyll a fluorescence measurements (mean ± standard deviation, n = 6) of Rugulopteryx okamurae after 41 and 74 d of culture under either light (70 µmol photons m^–2 s^–1; 12:12 h photoperiod) or continuous dark conditions. No significant differences were found between light and dark conditions (p < 0.05). R > 0.99 was obtained for all curve fittings.

	After 41 days of incubation		After 74 days of incubation
	Light	Dark	Light	Dark
ETRmax (μmol e^– m^–2 s^–1)	20.1 ± 5.78	16.5 ± 4.25	16.9 ± 4.19	23.2 ± 8.3
Ek (μmol photons m^–2 s^–1)	56.4 ± 23.5	42.1 ± 15.1	51.7 ± 7.4	86.5 ± 47.3
Fv/Fm	0.76 ± 0.01	0.75 ± 0.03	0.72 ± 0.01	0.73 ± 0.02

García-Gómez J.C., Sempere-Valverde J., Roi A., Martínez-Chacón M., Oloya-Ponzone L., Sánchez-Moyano E., Ostalé-Valriberas E. & Megina C. 2020. From exotic to invasive in record time: the extreme impact of Rugulopteryx okamurae (Dictyotales, Ochrophyta) in the strait of Gibraltar. Science of the Total Environment 704: Article 135408. DOI: 10.1016/j.scitotenv.2019.135408.

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Sánchez-Leal R., Bellanco M.J., Fernández-Salas L.M., García-Lafuente J., Gasser-Rubinat M., González-Pola C., Hernández-Molina F.J., Pelegrí J.L., Peliz A., Relvas P. et al. 2017. The Mediterranean overflow in the Gulf of Cadiz: a rugged journey. Science Advances 3: Article eaao0609. DOI: 10.1126/sciadv.aao0609.

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