Safi subslrate macrobenlhos of the GAR /agoon. Noies er Doc. Océanogr. /996,46: 17-46 17 Soft substrate macrobenthos of Fiji's Great Astrolabe Reer lagoon. List of taxons, densities and their biomass by 1. Clavier"', P. Newell**, C Garrigue*"'''', B. Richer de Forges"'*"', A. Di Matteo"'*'" * ** *"'* Centre ORSTOM, B.P. 70, 29280 Plouzané, France The University of the South Pacifie, School of Pure and Applied Sciences, P.O. Box 1168 Suva, Fiji. Centre ORSTOM, B.P. A5, Nouméa, New Caledonia Abstract During the Jornt Fijian-French ASTRü cruise conducted in April 1994 in the Great Astrolabe lagoon, the soft bottom macrobenthos \Vas quantitatively investigated at 25 sampling stations, using a 0.1 m 2 Smith-McIntyre grab. At each station, sediment was sampled with a total 1m 2 area (10 replicate grabs) and washed through a set of 20, 5 and 2 mm sieves to retain Oora and fauna. A total of 207 taxa was identified. This paper presents methods and raw data obtained from the study expressed for each taxon as numbers of individuais, dry weight and ash [Tee dry weight pel' m 2 . Résumé Au cours de la mission franco-lidjienne réalisée en avril 1994 dans le lagon du Grand récif de l'Astrolabe, le macrobenthos des fonds meubles a été échantillonné quantitativement sur 25 stations, à l'aide d'une benne Smith-McIntyre. Sur chaque station, le sédiment a été prélevé sur une superficie totale de 1 m 2 (10 coups de benne) et passé sur des tamis de 20, 5 et 2 mm pour isoler la flore et la faune. Un total de 207 taxons a été identifié. Le présent document regroupe un exposé des méthodes mises en oeuvre et une liste des résultats bruts issus de l'étude. Pour chaque taxon, ces derniers portent sur le nombre d'individus, le poids sec et le poids de matière sèche sans cendre. 1. Introduction Quantitative studies on the benthic fauna of the sediments behind coral reefs are surprisingly sparse, and no such studies have previously been made in Fijian waters. The Great Astrolabe Reef and Lagoon have been the subject of a baseline study (Morrison and Naqasima, 1992) but this did not include the fauna and flora of the lagoonal sediments, concentrating limited analysis and collecting resources on the reef (Naqasima and Brandy, 1992). Quantitative studïes on the marine benthos of soft substrate have been made in the South West Pacifie, centred on the work of the üRSTOM team based in Nouméa, New Caledonia. These include work on the South West lagoon of New Caledonia (Chardy et al., 1988; Chardy and Clavier, 1988), Chesterfield Lagoon (WNW of New Caledonia, Clavier and Garrigue, 1990) and Uvea Lagoon (Loyalty Islands, NE of New Caledonia; Clavier et al., 1992). Sampling soft sediments has been reviewed by Hartley and Dicks (1987) and the methods used in this study are described below. The protocol followed is the one that has been developed by the ORSTOM team operating from Nouméa, New Caledonia, and was followed in this study to facilitate comparisons between this and the carlier work done in New Calcdonia. 2. Materials and methods The study focused on subtidal sedinlents. Macrobenthic communities were sampled at 25 sites locatcd between 17 and 43 m depth over the lagoon (Table 1 and Figure 1). Sampling was carried out with the RV 'ALIS' in April 1994. If: c •. " Figure 1: Location of sampling stations
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Safi subslrate macrobenlhos ofthe GAR /agoon. Noies er Doc. Océanogr. /996,46: 17-46 17
Soft substrate macrobenthos of Fiji's Great Astrolabe Reer lagoon. List oftaxons, densities and their biomass
by 1. Clavier"', P. Newell**, C Garrigue*"'''', B. Richer de Forges"'*"', A. Di Matteo"'*'"
***
*"'*
Centre ORSTOM, B.P. 70, 29280 Plouzané, FranceThe University of the South Pacifie, School of Pure and Applied Sciences, P.O. Box 1168Suva, Fiji.Centre ORSTOM, B.P. A5, Nouméa, New Caledonia
Abstract
During the Jornt Fijian-French ASTRü cruiseconducted in April 1994 in the Great Astrolabelagoon, the soft bottom macrobenthos \Vasquantitatively investigated at 25 sampling stations,using a 0.1 m2 Smith-McIntyre grab. At each station,sediment was sampled with a total 1 m2 area (10replicate grabs) and washed through a set of 20, 5and 2 mm sieves to retain Oora and fauna. A total of207 taxa was identified. This paper presents methodsand raw data obtained from the study expressed foreach taxon as numbers of individuais, dry weightand ash [Tee dry weight pel' m2
.
Résumé
Au cours de la mission franco-lidjienne réalisée enavril 1994 dans le lagon du Grand récif del'Astrolabe, le macrobenthos des fonds meubles aété échantillonné quantitativement sur 25 stations, àl'aide d'une benne Smith-McIntyre. Sur chaquestation, le sédiment a été prélevé sur une superficietotale de 1 m2 (10 coups de benne) et passé sur destamis de 20, 5 et 2 mm pour isoler la flore et lafaune. Un total de 207 taxons a été identifié. Leprésent document regroupe un exposé des méthodesmises en oeuvre et une liste des résultats bruts issusde l'étude. Pour chaque taxon, ces derniers portentsur le nombre d'individus, le poids sec et le poids dematière sèche sans cendre.
1. Introduction
Quantitative studies on the benthic fauna of thesediments behind coral reefs are surprisingly sparse,and no such studies have previously been made inFijian waters. The Great Astrolabe Reef and Lagoonhave been the subject of a baseline study (Morrisonand Naqasima, 1992) but this did not include thefauna and flora of the lagoonal sediments,concentrating limited analysis and collectingresources on the reef (Naqasima and Brandy, 1992).
Quantitative studïes on the marine benthos of softsubstrate have been made in the South West Pacifie,
centred on the work of the üRSTOM team based inNouméa, New Caledonia. These include work on theSouth West lagoon of New Caledonia (Chardy et al.,1988; Chardy and Clavier, 1988), ChesterfieldLagoon (WNW of New Caledonia, Clavier andGarrigue, 1990) and Uvea Lagoon (Loyalty Islands,NE of New Caledonia; Clavier et al., 1992).
Sampling soft sediments has been reviewed byHartley and Dicks (1987) and the methods used inthis study are described below. The protocolfollowed is the one that has been developed by theORSTOM team operating from Nouméa, NewCaledonia, and was followed in this study tofacilitate comparisons between this and the carlierwork done in New Calcdonia.
2. Materials and methods
The study focused on subtidal sedinlents.Macrobenthic communities were sampled at 25 siteslocatcd between 17 and 43 m depth over the lagoon(Table 1 and Figure 1). Sampling was carried outwith the RV 'ALIS' in April 1994.
If:c
~r;i( •. "
Figure 1: Location of sampling stations
Soft sllbslrale macrobenthos ofthe GAR lagoon Notes er Doc. Océanogr. 1996. 46: 17-46 18
Macrofauna and macroflora were sampled using a0.1 ml Smith Mclntyre grab weighed down with anadditional 60 kg lead ballast (Figure 2). Thesampling unit was a 1ml area, i.e. ten 0.1 ml grabs.The total collected volume of sediment was about 601. The boat was moored with a bow anchor and wasfree to swing under the influence of wind. Theprobability of a bite coincidence between sampleswas consequently very low. The samples from thesame station were mixed and passed through 20, 5and 2 mm stacked sieves. On board, organisms wereseparated from the substrate, sorted by majortaxonomie groups and preserved in 10 ~/;, fonnalinneutra1ised with borax.
Figure 2: The Smith-Mc-Intyre grab
In the laboratory, taxonomie detenninations werecarried out as precisely as possible using theavailable literature. The results per station have beenexpressed as the number of individuals per m2 foreach identified taxon for macrofauna. Dry weightswere measured after oven-drying (60°C) untilconstant weight and the ash weight by fùrtherheating at 550°C for 3 hours. The ash free dryweight is the difference between these two values.The biomasses have been expressed in grams of dryweight and ash free dry weight per ml formacrofauna and macroflora. Taxonomie biomasseshave been summed to obtain the total macrobenthicbiomass per station.
Table 1 : Depth (m) and position of the sampIingstations
Chard)' P. & J. Clavier, 1988. Biomass and trophic structure ofthe macrobenthos in the south west \agoon of NewCaledonia, Afar. Biol., 99 : \95-202.
Chardy P., C. Chevillon & J. Clavier, 1988, Major communitiesin the south-west lagoon of New Caledonia. Coral Reefs, 7 :69-75.
Clavier J. & C. Garrigue, 1990. Étude qLlantitative dumacrobenthos dans le lagon des îles Chesterfield. Listestaxonomiques, densités et biomasses. Nouméa. OR5TOM.Rapp. Sei. lech., sei mer, biol. mar., 59: 100 pp.
Clavier J., C. Garrigue, G. Bargibant. A Di Matteo, P. Hamel,M. Kulbicki ct R. Urbain., 1992. Etude quantitative dubenthos dans le lagon d'Ouvéa. Liste taxonomique, densitéset biomasses du macrohenthos, ATP, pigmentsphotosynthétiqucs et matière organique dans le sédimentNouméa: ORSTOM Rapp. sci tech., Sci Mer Biol. mar.,64: 72 pp.
Hartley J.P, & B. Dicks, 1987. Macrofauna of subtidal sedimentsusing remote sampling. In : Biological surveys of estuariesand coasts. J.M Baker & W,J. Wolff (cds.), CambridgeUniversity Press, Cambridge. 449 pp.
Naqasima M.R. & M. Brandy, 1992. Marine Biologypreliminary studies of the Astrolabe lagoon, In : Fiji's GreatAstrolabe reef and lagoon : a baseline stndy. R.J. Morrison& MK Naqasima (eds.). Institute of Natural Resources, TheUniversity of the South Pacific, Environmental StudiesReport, 56