LA PEROUSE

Name: LA PEROUSE
Start: 2016-09-15
End: 2016-09-30
Location: Indian Ocean

Type	Oceanographic cruise
Ship	Antea
Ship owner	IRD
Dates	15/09/2016 - 30/09/2016
Chief scientist(s)	MARSAC Francis
	MARINE BIODIVERSITÉ, EXPLOITATION ET CONSERVATION - UMR - SÈTE Avenue Jean Monnet CS 30171 34203 Sète Cedex 33 (0)4 99 57 32 00 https://umr-marbec.fr/
DOI	10.17600/16004500
Objective	This cruise studied an underwater relief, the La Pérouse seamount, located 90 nautical miles to the NW of Reunion Island, culminating at 52 m from the surface. The operations aimed to study the physical and biological environment associated with this seamount, in order to assess the possible impact on productivity, within a zone which is generally qualified as oligotrophic, set at the centre of the South Equatorial Current. The main objectives were to: 1) Produce an accurate bathymetric survey of the seamount; 2) Characterize the physical processes leading to enrichment of the first trophic levels near a seamount; 3) Assess the spatial-temporal density and faunal diversity of micronekton making up the fodder fauna for higher predators; 4) Take a rapid inventory of demersal fish diversity on the slopes of the seamount; 5) Analyze the food web levels of a seamount ecosystem, principally in the pelagic realm. The related project is "seamount ecosystems in the South-West Indian Ocean", one of the components of the WIOURI (West Indian Ocean Upwelling Regional Initiative) project in the international IIOE-2 (International Indian Ocean Expedition 2) programme. The regional division for research and technology of Reunion Island granted substantial funding to cover operating costs (excluding vessel) for the cruise. The fleet joint service unit UMS Flotte also provided financial support, which we are grateful for.

Sea/Ocean

Indian Ocean

(Mont La Pérouse 90 miles NW of Reunion Island)

Ports

Port of departure : Le Port (Réunion)

Port of return : Le Port (Réunion)

Scientific Authority

MARINE BIODIVERSITÉ, EXPLOITATION ET CONSERVATION - UMR - SÈTE

Avenue Jean Monnet

CS 30171

34203 Sète Cedex

33 (0)4 99 57 32 00

https://umr-marbec.fr/

Participating bodie(s)

IRD, CNRS, Hydro Réunion

Discipline(s)

PHYSICAL OCEANOGRAPHY
BIOLOGICAL OCEANOGRAPHY
CHEMICAL OCEANOGRAPHY
FISHERIES

Code	Label	Quantity	PI
B02	Phytoplankton pigments (eg chloroph Hervé Demarcq - On filtration manifold, 3 or 4 levels (depending on station) - Filters frozen at -80°C	88 samples	MARSAC Francis
B09	Zooplankton Bongos 200 µ and 300-500 µ in oblique lines (respect. 200 and 500 m) - 22 samples preserved in formalin for biomass and taxonomy - 66 samples (6 size classes) oven-dried for calculation of isotope ratios	88 samples	MARSAC Francis
B10	Neuston Manta fillet, 15 min. haul	2 samples	MARSAC Francis
B14	Pelagic fish Yves Chérel, Evgeny Romanov and Pavanee Annasawmy - 2000 fish recovered - Mesopelagic fauna by trawling - Identification, counts, size measurements	-	MARSAC Francis
B20	Molluscs Yves Chérel, Evgeny Romanov and Pavanee Annasawmy - Several dozen cephalopods - Mesopelagic fauna by trawling - Identification, counts, size measurements	-	MARSAC Francis
B21	Crustaceans Yves Chérel, Evgeny Romanov and Pavanee Annasawmy - Several hundred crustaceans - Mesopelagic trawl fauna - Identification, counts, size measurements	-	MARSAC Francis
B25	Birds Njaratiana Raberisoa - Around a hundred birds, 8 species - Counting along linear transects - Daily frequency, 5 to 6 h/d	-	MARSAC Francis
B65	Exploratory fishing + Frédéric Nair - Demersal longlining on the slopes of La Pérouse (60 to 500m)	4 deployments	BACH Pascal
B71	Particulate organic matter (inc POC Hervé Demarcq - 64 samples (32 for C isotope measurements, 32 for N isotope measurements) - On a two-stage filtration ramp (surface and maximum fluorescence) - Pre-calcined filters, dried and stored at room temperature.	64 samples	MARSAC Francis
D71	Current profiler (eg ADCP) + Marc Soria - 360 continuous 12h S-ADCP profiles on the summit of Mont La Pérouse - 11 L-ADCP profiles on bathysonde, depths from 100 to 1500m	371 profiles	GRELET Jacques
G73	Single-beam echosounding Marc Soria - EK-60, 4 frequencies (38, 70, 120, 200 kHz), continuous along transects	76 hours	MARSAC Francis
H09	Water bottle stations Hervé Demarcq - Rosette	11 stations	MARSAC Francis
H10	CTD stations Rosette 11 bottles + 2 L-ADCP 300 kHz + SBE 911Plus - Max depth: 1500 m	23 stations	GRELET Jacques
H11	Subsurface meas. underway (T,S) Continuous (every 5 minutes)	-	GRELET Jacques
H13	Bathythermograph XBT - 4 launches during transit Réunion-La Pérouse	4 stations	GRELET Jacques
H17	Optics (eg underwater light levels) PAR profiles (SBE 19)	23 stations	GRELET Jacques
H21	Oxygen Hervé Demarcq - 3-level water sampling for bathysonde calibration	23 stations	MARSAC Francis
H22	Phosphate Hervé Demarcq - Rosette water sampling for nutrient analysis on Technicon	138 samples	MARSAC Francis
H24	Nitrate Hervé Demarcq - Rosette water sampling for nutrient analysis on Technicon	138 samples	MARSAC Francis
H25	Nitrite Hervé Demarcq - Rosette water sampling for nutrient analysis on Technicon	138 samples	MARSAC Francis
H26	Silicate Hervé Demarcq - Rosette water sampling for nutrient analysis on Technicon	138 samples	MARSAC Francis
H32	Isotopes Pavanee Annasawmy - Tissue sampling of micronektonic organisms for analysis of stable N and C isotope ratios	180 samples	MARSAC Francis
H90	Other chemical oceanographic meas. Salinity (rosette water sampling)	51 samples	MARSAC Francis

Summary of measurements

-Detailed bathymetric survey of La Pérouse seamount, whose mapping was inaccurate and poorly positioned.
-Hydrology stations (11) at 11 levels (max 1,500 m) with water samples taken to measure oxygen, salinity, nutrients, chlorophyll pigments and particulate organic matter.
-22 oblique hauls with 200-micron (0-200 m), and 300 and 500 micron (0-500 m) Bongo nets to assess the biomass and zooplankton diversity; Sieving to measure stable isotopes (N and C), 6 separate fractions of zooplankton size.
-1 fixed-point station (12 hourly profiles) on the summit of La Pérouse seamount (0-60 m) with water samples and continuous ADCP measurements.
-Petal-shaped transects (6) with acoustic sounder to characterize the scattering layers between the seamount and the surrounding 8 nautical miles.
-Acoustic legs along the Azores around the seamount.
-Trawling for micronekton (10 hauls) at different depths (50 to 500m), for biomass assessment and taxonomic identification of species present; Tissue samples taken on micronekton organisms for analyses of stable isotopes (C, N).
-Fishing trials to catch demersal fish with bottom longline, and of pelagic fish using vertical longlines and a drifting pelagic longline.
-XBT casts along the transit underway between La Pérouse seamount and Reunion Island.
-Counts of seabirds observed along linear legs.

Location map

Positionning system

Geodetic system : WORLD GEODETIC SYSTEM 1984 = WGS84

Positioning system : GPS naturel

Data managed by SISMER

Bibliography

Publications

Annasawmy Pavanee, Bustamante Paco, Point David, Churlaud Carine, Romanov Evgeny V., Bodin Nathalie (2022). Trace elements and δ15N values in micronekton of the south-western Indian Ocean. Marine Pollution Bulletin, 184, 114053 (16p.). Publisher's official version : https://doi.org/10.1016/j.marpolbul.2022.114053 , Open Access version : https://archimer.ifremer.fr/doc/00811/92284/

Annasawmy Pavanee, Point David, Romanov Evgeny V., Bodin Nathalie (2022). Mercury concentrations and stable isotope ratios (δ13C and δ15N) in pelagic nekton assemblages of the south-western Indian Ocean. Marine Pollution Bulletin, 174, 113151 (16p.). Publisher's official version : https://doi.org/10.1016/j.marpolbul.2021.113151 , Open Access version : https://archimer.ifremer.fr/doc/00811/92286/

Romanov Evgeny V., Cherel Yves, Marsac Francis (2021). New record of Ectreposebastes niger (Fourmanoir, 1971) (Setarchidae, Scorpaeniformes): a rare bathypelagic fish from La Pérouse Seamount, Western Indian Ocean, and distribution of Ectreposebastes Garman, 1899 in the Indian Ocean. Zoosystema, 43(15), 283-296. Publisher's official version : https://doi.org/10.5252/zoosystema2021v43a15 , Open Access version : https://archimer.ifremer.fr/doc/00700/81172/

Le Croizier Gaël, Lorrain Anne, Sonke Jeroen E., Jaquemet Sébastien, Schaal Gauthier, Renedo Marina, Besnard Lucien, Cherel Yves, Point David (2020). Mercury isotopes as tracers of ecology and metabolism in two sympatric shark species. Environmental Pollution, 265(Part B), 114931 (11p.). Publisher's official version : https://doi.org/10.1016/j.envpol.2020.114931 , Open Access version : https://archimer.ifremer.fr/doc/00633/74465/

Noyon Margaux, Rasoloarijao Zo, Huggett Jenny, Ternon Jean-Francois, Roberts Michael (2020). Comparison of mesozooplankton communities at three shallow seamounts in the South West Indian Ocean. Deep-sea Research Part Ii-topical Studies In Oceanography, 176, 104759 (17p.). Publisher's official version : https://doi.org/10.1016/j.dsr2.2020.104759 , Open Access version : https://archimer.ifremer.fr/doc/00609/72157/

Marsac Francis, Annasawmy Pavanee, Noyon Margaux, Demarcq Herve, Soria Marc, Rabearisoa Njaratiana, Bach Pascal, Cherel Yves, Grelet Jacques, Romanov Evgeny (2020). Seamount effect on circulation and distribution of ocean taxa in the vicinity of La Pérouse, a shallow seamount in the southwestern Indian Ocean. Deep-sea Research Part Ii-topical Studies In Oceanography, 176, 104806 (18p.). Publisher's official version : https://doi.org/10.1016/j.dsr2.2020.104806 , Open Access version : https://archimer.ifremer.fr/doc/00631/74286/

Annasawmy Pavanee, Ternon Jean-Francois, Cotel Pascal, Cherel Yves, Romanov Evgeny V., Roudaut Gildas, Lebourges-Dhaussy Anne, Ménard Fréderic, Marsac Francis (2019). Micronekton distributions and assemblages at two shallow seamounts of the south-western Indian Ocean: Insights from acoustics and mesopelagic trawl data. Progress In Oceanography, 178, 102161 (21p.). Publisher's official version : https://doi.org/10.1016/j.pocean.2019.102161 , Open Access version : https://archimer.ifremer.fr/doc/00510/62135/

Thesis using campaign data

Panetier Aurélie (2023). Shipborne Global Navigation Satellite Systems for Offshore Atmospheric Water Vapor Monitoring. PhD Thesis, ENSTA Bretagne.

Annasawmy Pavanee (2019). Structures des communautés micronectoniques en relation avec les conditions environnementales à deux monts sous-marins peu profonds du sud-ouest de l'Océan Indien / Patterns among micronekton communities in relation to the environmental conditions at two shalow seamounts in the south-western Indian Ocean. PhD Thesis, Université de Montpellier, University of Cape Town.