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Journal of Coastal Research Fort Lauderdale Prelitninary Data on the Meroplanktonic Larvae of Polychaeta in the NooDlea Lagoon, South-Western New Caledonia! Michel Bhaud Laboratoire Arago, (CNRS, URA 117) 66650 Banyuls-sur-mer, France ABSTRACT _ BHAUD, M., 1986. Preliminary data on the meroplanktnnic larvae of polychaeta in the Noumea lagoon, south-western New Caledonia. Journal ofCoastal Research, 2(3), 297-309. Fort Lauderdale, ,tllllllll,. ISBN 0749-0208. ..•_ ...~ This paper presents preliminary data on Polychaeta Annelida larvae from a coral reef .....- ofNoume~ • lagoon in thearea New-Caledonia. Larvalplanktonisrevealed as a good tool for faunistic investigations. A detailed surveyofbenthic communities shouldproduceas a con sequence, sampling ofnew species for the area: 7 species of Spionidae, 3 Chaetopteridae and 1 Sabellariidae. The advantages offered by such a geographically discrete area for the study oflarval spreading are discussed. The use of4 indices(numberofspecies, numberof individuals, diversity index and equitability) allow specificationofthe distanceofthe larval population sampled from its origin. Size comparisons between taxons sampled inside and outside thelagoonshowthatlengthofplanktoniclarval lifeis not an absoluteparameterbut is a function of extemal circumstances linked with water currents which reduce the ten dancy ofthe larvae to settlewith the sediment. With regard to seasonalvariations oflarval appearance in the plankto~ this area is not characterized by two groups ofspecies, each havingitsown reproductiveperiod. 88 itisundertemperatelatitudes, butbyonlyone group; the center of the reproductive period being adjusted to March and April. ADDITIONAL INDEX WORDS: Annelida, lagoon, laroae, New Caledonia, Polychaeta, seasonal variation, sett1emen~ spreading. INTRODUCTION provided some information It is therefore interest ing to compare the results of these investigations This work is partofa comparative oceanographic with data from a new geographic locale such as an investigation and springs from theremarks ofFAGE intertropical lagoon ofthe Western Pacific, located and DRACH (1957) on the comparative biology of in this study near Noumea in south-west New marine species in various areas within their dis Caledonia This area is becoming increasingly well tribution ranges. One means of knowing to what researched as evidenced by the results of studies extent and in what ways physiological cycles adjust dealing with geomorphology, hydrology, primary to geophysical factors is to see how these param production (DANDONNEAU et al, 1981; ROUGERIE, eters vary in diverse situations in the course of the holoplankton and hyponeuston fauna (BINET, 1984, year and to observe in parallel some biological 1985; CHAMPALBERT, 1982). Investigation of sea criterion, such as the time ofyear when larvae are sonal variations of meroplankton, which relate re present, the size of oocytes, or the proportion of production ofbenthic adults and settlement period juveniles. 0 bservations already made, especially for young stages, seemed a natural extension of on Polychaete annelids, in temperate (BHAUD, these previous works. 1966a), Indian tropical (BHAUD, 1972), and sub antarctic (DUCHENE, 1979, 1980) zones have already MATERIALS AND METHODS 1This work, conductedduringsurvey1979-1) ispartofajointproject This study examins a collection of zooplankton financed by the ORSTOM and the CNRS: IICoral reef and lagoon gathered over several years at several sites in ecosystems in New CakdoniLl' (CNRS - ATP 3393 and 4067. 85037 received 4 November) 1985; accepted in revision 27 Noumea lagoon. The samples were collected by January 1986. researchers at the ORSTOM center andtaken dur- tV co 00 0 N I 22 5/ '\.166°30 E ,0 2 NEW CALEDONIA 1/ 30 " + 4 0 NEW CALEDONIA I Kunie " ~.. Island ~. Q \ ... ", OULARI BAY Boulari Passage --''''- .. _-,' ~ ,- , \ , .. ,; , , ~ , I :r' '--' Qj / ,----rJ '-"" t: X Q.. 0 I!Yl [/Maitre Island 0) ® 0 ~o [ill] LAGOON Goelal'ld Island " .. " ,." <:(' C>" \, '. ;: / ' .. ~ ,'. ~(\\ ~ fA"~ ~rt. _t '''J' ~'-'~ ./ ...... / Amedee ,- . ~~'\. 'J0~...e ,...... .,ort. 0 0 lighthouseri1 .' '; ~'~o ~,' ~--~' ---.:::::>' ",'" ~e o9>e r;-;, ~ .~_.., ~ ~~:' ~~- ~~ ~,~---. Q...O. _ ~~~ --, ~<!" ~oe,e, L!!J ~ :::.~ /. ::::~-- ,'~': c:; \~,-- -- .-- _.- ~~---_ <:>~.--------- ~~ ---,- /.)!: ••-:---~--'.-'"::.'" ~ ---:::.' -----: 0<'" '-,' O~(l) '-- , ... _ ... -- ..... -- ~-J .... ----' ............"-'::=~~/--::::::=:::6f'J...--.... ',,--- - ... --- -- :')'\ ",O~J('\.'lJ <:00 ::; b ",0 ~O'" ~ ~ 0 a... 1660 E 22°305 Jo'igure 1 Map of the reef lagoon, south-west New Caledonia. showing stations where planktonic larvae were collected; (1) stations on the lighthouse Amedee transect; (2) location of 24-hour studies; (3) coastal stations; (4) open sea sampling station in La Sarcelle straits. ing a field trip between March and May 1979, distances and compaction effects. Readings were (Figure 1). Different plankton nets, WP2 and FCO, taken after 24 hours of sedimentation. where used on different occasions, providing rapid In five out of the six samples, the collecting comparison of their catching power. The samples efficiency of net WP2 was greater, by 12% of the were taken during5 or 10 minute hawls at a depthof mean ofthe two measurements. Howeverthere was 1 to 2 m. The greatest depths in the lagoon are cer no indication that the differences were the same for tainly as much as 50 m, but around the small coral all the taxonomic groups considered. Thus, from reefs the water was shallower (10 to 20 m) and the precise counting of one particularly well represen depth in the sampling zone was often only 4 to 5 m. ted larval category of the family Spionidae, one The boat most often used, particularly around the observed that the WP2 net collected many more small coral islands, was ofthe Zodiac type. with an larvae than a comparisonofbiomass would lead one outboard engine. In this case, to maintain a steady to expect (Table 1B). In particular it retained those bearing it was necessary for the net to be towed size classes to which the larvae of annelids most directly behind the engine. The net was maintained often belong. This class makes up only a small frac in this position either by an assistant or by two tion of the biomass, which explains the small dif ropes attached to the sides ofthe boat at two points ferences between the comparative results for total forward of the engine. A more powerful boat, the biomass. oceanographic vesselDawa, 11 m long, was used for Although the FCO net seemed to be oflimited use coastal exploration. Inside the lagoon a thirdtypeof for collectingmaterialofaround300Jim, some sam boat La Santa Maria, 8 m long, was used for the ples taken.. outside the lagoon produced larger lar seasonal samplings of station IV and for com vae, up to 2 mm in size, which permitted precise parisons between the two types ofnets. Outside the identification to species level. Because the FCO net lagoon, the oceanographic vessel Vauban, 28 m sampled a wider range of sizes than was gener long, was used for a limited number of collections ally encountered in the lagoon, it was very madeinorderto study the mechanisms oflarval dis complementary. persion. Identifications in this preliminary study are limited to the family leveL Some larval forms Taxonomic Observations about not previously reported are described, although Polychaete Families their specific identification still remains imprecise Although it is not necessary to comment on each in the absence of cultures. However, in some cases family represented in the various tables, it should the determination was sufficiently precise to allow be noted that the two family names Aphroditidae us to come to some conclusions about the fauna and and Amphinomidae are used in the broad sense the biogeography. (FAUVEL, 1923) in that they are nowadays con RESULTS sidered to consist of five and two families, respec tively Our data suggest that the collected larvae Comparison of the Collecting Efficiencies belong in the former case to the Polynoidae and in of the Nets the latter case to the strict Amphinomidae as dis tinct from the Euphrosinidae. Likewise, the generic Because two different nets were used to obtain designations Prionospio and Polydora refer to the samples [WP2 net with mesh size 200 Jim, 0.57 m Prionospio andPolydora complexes, containingres diameter aperture and 2.6 m lonq (UNESCO, 1968) pectively four and six genera; Paraprionospio, and FeO net 300 Jim mesh size, 0.50 m diameter Orthopnonospio, Streblospio, andPrionospio on the and 2.9 m long (BINET, 1984)], a comparison of one hand, and Pseudopolydora, Polydora, Caraz their catching power was necessary. For this pur ziella, Tripolydora, Boccardiella, and Boccardia pose, both nets were simultaneously towed for 10 (BLAKE and KYDENOV, 1978) on the other. minutes in parallelover part of the transect from Noumea to Amedee lighthouse. Six pairs of sam Family Opheliidae ples were obtained at 2 m below the surface at a (A) One very common species was collected in speed of 1.5 m/ s. After each sampling the total the sub-surface plankton samples. Gills present catch was assessed (Table 1A). The results were from the second setiger, ocular spots on the median compared on the basis of the biomass collected in parapodia, a ventral furrow over the whole body, test-tubes, whose diameters were not necessarily and the presence of29 setigerous segments indicated the same, so as to have similar sedimentation it to be Armandia lanceolata