Reef of Ficopomatus Enigmaticus (Polychaeta; Serpulidae) in the Mar Chiquita Coastal Lagoon, Argentina

Reef of Ficopomatus enigmaticus (polychaeta; Serpulidae) in the Mar Chiquita CoastaI Lagoon, Argentina

Evangelina SCHWINDT & Osear Osvaldo IRIBARNE

Schwindt, E. & Iribarne, 0.0. 1998. Reef of Ficopomatus enigmaticus (Polychaeta; Serpulidae) in the Mar Chiquita Coastal Lagoon, Argentina. Boll. SHNB Soco Hist. Nat. Ba/ears, 41: 35-40. ISSN 0212-260X. Palma de Mallorca.

Ficopomatus enigmaticus (Polychaeta, Serpulidae) is a reef-building polychaete that since the sixties has colonized the SW Atlantic Mar Chiquita coastal lagoon (Argentina, 37° 32' to 37° 45' S and 57° 19' to 57° 26' W; a UNESCO MAS site). The reefs have an approximately circular shape reaching up to 4 m in diameter and 0.5 m in height. Living individuals are at the edges where larval settlement occurs. Settlement has al so been observed on shells, bottles, rocks, SOCIETAT O'HISTORIA pillars and bones. The habitat created by their tubes provide shelter for NATURAL DE LES BALEARS numerous organisms that have largely increased the amount of organisms that inhabit in structured habitats. AII evidence accumulated to the present suggests that the introduction of this reef building species has provoked a significant environmental change, affecting the sediment dynamics and the ecological structure of the lagoon. Keywords: Ficopomatus enigmaticus, reef, po/ychaete, coastal /agoon.

ESCULLS DE F1COPOMATUS EN1GMATlCUS (POLYCHAETA; SERPULIDAE) EN LA LLACUNA COSTERA DE MAR CHIQUITA, ARGENTINA. Ficopoma/us enigmaticus (Polychaeta, Serpulidae), és un poliquet formador d'esculls que des deis anys 60 ha colonitzat la lIacuna costera Mar Chiquita del sud-oest atlimtic (Argentina, 37° 32' a 37° 45' S Y 57° 19' a 57° 26' O; un 1I0c MAS de I'UNESCO). Els esculls tenen una forma aproximadament circular, podent arribar fins els 4 m de diametre i 0,5 m d'al¡¡;ilria. Els individus vius es troben en les vores, on també esdevé I'assentament larval. L'assentament també ha estat observat sobre les valves, ampolles, roques, pilars de ponts i 05505. L'habitat creat pels seu s tubs dóna refugi a nombrosos organismes i ha augmentat en gran manera I'abundancia d'organismes que viuen en hilbitats estructurats. Totes les evidencies acumulades fins ara suggereixen que la introducció d'aquesta especie ha provocat un canvi ambiental significatiu, afectant la dinilmica sedimentaria i I'estructura ecológica de la lIacuna. Paran/es clan: Ficopomatus enigmaticus, escull, polique/s, llacuna costera.

Evangelina SCHW1NDT and Osear Osvaldo lRlBARNE Labora/orio de Ecología, Depar/amento de Biología (FCEyN), Universidad Nacional de Mar del Plata, Argentina. Dirección Postal: Casilla de Correo 573. Correo Central Mar de/ Plata, (7600) Mar del Plata, Argentina. Correo Electrónico: [email protected]

Recepció del manuscrit: 6-ago-98; revisió acceptada: 16-set-98. 36 Boll. Soco Hist. Nat. Balears, 41 (/998)

Human beings have radically altered the that occurred during the Holocene period world wide species distribution pattern by (Fasano et al., 1982). Today the lagoon transporting species throughout the world covers a surface of approximately 46 km 2 and 2 deliberately and accidentally, and introducing has a drainage basin of about 10.000 km • them into areas where they are not native The shape is elongated with an NE-SW (e.g. by shipping; Primack, 1993; Cohen & orientation, and is characterized by mudflats Carlton 1998). These exotic species may and large surrounding areas dominated by the displace native species through competition cordgrass Spartina densiflora (Olivier et al., for limited resources, predation to the point of 1972a; Fasano et al., 1982). The mean depth extinction or, change the habitat to such is 0.6 m, but depths of up to 2 m occur extent that natives are no longer able to along the discharges channel (Isla, 1997). The persist (Primack, 1993). Several exotic species mouth of the lagoon is affected by low are easily able to invade and dominate new amplitude (S 1.5 m) tides, and the lagoon habitats for many reasons. One of these being receives sediment and water charges from the absence of their natural predators to con creeks and artificial channels (Fasano et al., trol their population growth. Exotic species 1982). Wind is the principal force controlling may also have better adaptive qualities than the variations in water level (Reta et al., native species to the disturbances generated 1997). Salinity changes are particularly by the activity of modern humans (e.g. important oscillating from a salt content dredging, contamination, resource overex higher than the sea during the summer (up to ploitation; Adam, 1990). Moreover, exotic 40, pers. obs.) mainly due to marine input species may be very difficult to remove from and evaporation, and to freshwater during the the colonized environments (Coblentz, 1990). rainy autumn (Fasano etal., 1982). The mean Most accidental introductions are from annual precipitation in the area is 790 mm (in fouling organisms growing on the undersides 30 years, Fasano et al., 1982). of ships (e.g. barnacles; Raffaelli & Hawkins, The lagoon mudflats are important 1997) favoring their dispersion. Serpulid stopover sites for several migratory shorebirds worms are one of the most important groups that breeds in the northern parts of North of fouling organisms (AlIen, 1953). Fico America wintering in South America (e.g., pomatus enigmaticus (Polychaeta, Serpulidae) Charadrius falklandicus, two-banded plover; is a calcareous reef-building species dis Calidris canutus, red knot; C. alba, tributed in brackish waters in temperate zones sanderling; C. fuscicollis, white-rumped throughout the world (Ten Hove & sandpiper; Limosa haemastica, hudsonian Weerdenburg, 1978). This species originated godwit; Tringa melanoleuca, greater in Australia (AlIen, 1953) and was observed yellowlegs; T. flavipes, lesser yellowlegs; in Argentina in 1943 (Rioja, 1943 in Pluvialis dominica, American golden plover; Orensanz & Estivariz, 1971). This species P. squatarola, black-bellied plover; Numenius was already present in the Mar Chiquita phaeopus, whimbrel; Botto el al., 1998). coastal lagoon (Argentina, 37° 32' to 37° 45' Several bird species are residents of this site S, and 57° 19' to 57° 26' W; Fig. 1) in the (Martínez, 1993; Bortolus et al., 1998) early seventies (Orensanz & Estivariz, 1971). including swans (Cygnus melancoryphus and However, there is no evidence of their Coscoroba coscoroba), roseate spoonbills presence in Holocene sediments (Orensanz & (Platalea ajaja), flamingos (Phoenicopterus Estivariz, 1971) which suggest that it is a chilensis), white-faced ibis (Plegadis chihi) new invader. and oystercatchers (Haematopus palliatus). Mar Chiquita is one of the few coastal Due in part to their importance as a sto po ver lagoons of Argentina which has evolved site for shorebirds the lagoon is now a "Man following the relative oscillations of sea level and the Biosphere" (MAB) site and is being E. Schwindt & 0.0. Iribarne, Reel 01 Ficopomatus enigmaticus in Argentina 37

where the water flow is multidirectional dominated by wind (pers. obs.). In these areas mean depth is 0.4 m depending of rainfall and reefs have an approximately circular shape (Fig. 2). The size is variable (up to 4 m in diameter and 0.5 m in height) and the maximum height depends on the water level (Obenat & Pezzani, 1994). It is also common to find pairs of reefs that are fused (Obenat & Pezzani, 1989; Schwindt, 1997a). When water flow is unidirectional (i.e. in channels and creeks), the shapes of reefs are generally elongated, mainly parallel to current direction. The accumulation of sediment inside the reef produces the mortality of the oldest organisms (Keene, 1980; Pezzani & Obenat, 1988). The abundance of reefs decreases towards the mouth of the lagoon (where salinity increases), and their distribution is restricted to only a few sites (mainly pillars; pers. obs.). Areas covered by reefs, lead to retention of sediments that would otherwise be transported out of the lagoon (pers. obs.). As a result sediment input to the lagoon during heavy rainfall, river drainage or human activities is accumulating, decreasing the lagoons mean depth (Fasano et al., 1982). Ficopomatus enigmaticus is an annual Fig. 1. Map showing the location of the Mar iteroparous whose females may produce 1 to Chiquita Coastal Lagoon (Buenos Aires, Argenti 2 batches of small eggs per reproductive na). lnset in the lower right comer shows the period that are freely released into the water. location of the lagoon in South America. The eggs develop into planktonic Fig. l. Localització de la l/acuna costera de Mar planktothrophic larvae that act as a dispersal Chiquita (Buenos Aires, Argentina). El requadre phase (Obenat & Pezzani, 1994). There are de la part inferior dreta mostra la localització de two larval settlement periods, the first occurs la l/acuna costanera a Sudamerica. between March and April and the second between November and December (Obenat & Pezzani, 1994), and individuals reach up to 55 mm in length (Obenat, 1984). Individuals proposed as a "Ramsar" site. However, this is are suspension feeders mainly capturing the only SW Atlantic estuarine environment detritus (Olivier el al., 1972b). The only notoriously invaded by the reef-building predator described is a reef inhabitant fish serpulid Ficopomatus enigmaticus, and today (Austrogobius parri, Olivier et al., 1972b), a the reefs occur in almost all sites of the species found at very low density in the lagoon (Pezzani & Obenat, 1994). lagoon (pers. obs.). The size of Ficopomatus enigmaticus The living polychaetes are at the reef reefs depends on their location. The areas edges and larval settlement occurs between most covered by reefs are the embayments their calcareous tubes (Obenat & Pezzani, 38 Bol/. SOCo ¡-lis/. Na/. Balears, ./1 (/998)

Fi g, 2, Ph otograph showin g the sizc and shape of th e Ficopolllo /u s el1ig lllo/lCIIs reefs. Fig. 2. Fa /agrafia que lil as/ro la Iluda i jarillo deis esculls de Fico[1 0lll atll s cni glll at icus.

1994). Rec ruilmenl also may occur on shell s, orga ni sms (Orensanz & ESli vari z, 197 1; principall y on lhe gaslropod Adelomelon Schwin cl t. 1997a) including lh e mollu sk: brasiliana, and second aril y on lhe bivalves Lilloridina parchappi. po lyc haetes (adu lt s ancl Mac/ra isabel/eana and Tagelus plebeius juven il es): Laeonereis acura, He/eromas/us (Schwin dl & Iribarne 1998). The lhree simi/is, Nephtys fluviati/is, Nean/hes succinea, species are represenled in Holocene fossil Polydora /ig ni and Boccardia hama/a, shell assembl ages (Fasano e/ al., 1982). amphipods: Corophium insidiosus and Melita However. today on ly T. plebeius lives in lhe palma/a. Several aq uali c birds (e.g .. swan s, lagoon wh il e A . brasilia na and M. dueks) use th e ree fs as resting siles in crcasi ng isabel/eana are exclu sive ly mar in e species. th e co ncentration of guano (pers. obs. ). The Occasionall y lh e larval settl emenl occurs on tubes, wh ich are whit e when inili all y secreled. bottl es, rocks, pi ll ars bones and di slodged are slcacli ly covercd by br iozoa (Conopeum parl s of lh e reefs (pers. obs. ). bul which cf. seura/i), gree n algae (Cladophora sp. and allVays need a hard fi xed sub slralum on lhe En/eromorpha sp.) and dialoms (Obenat. sedimen l (Obenal & Pezza ni , 1994). 1984) as th ey age. Large grapsid crabs (e. Simil arl y lo other reefs. lh e one's angula/u s ancl Chasmag na/hlls g ranilla/a) generated by Ficopoma/us enig ma/icus shelt er unclerneath the reefs e. (Schwin dt. increase lh e hab il at" s Slru Clural compl ex ily, 1997a). e. angllla /lI s is th e mo sl cO lllmon affecling abundance. diversily and di slri bul ion erab and th eir ab unclan ce is positi ve ly rclaled of ilS associated fau na. In thi s case lhere is a lo Ih e reef size (Schwin clt. 1997b). significanl increase of ad ults and juveniles of The soft bo tt om arcas surrounding Ih e lhe crab Cyr/ograpsus altimanus (E. Spiva k reefs are inhabited by four infauna l pers. co m. ) and recenll y mo lted juveniles of po lyehaetes: Laeonereis aCllra, He/eromas/lI s th c crab e. angula/us (4 to 7 mm size) with simi/is. /\'eph/ys flllvinri/is and Neal7lhes an abundance of up lO 4.800 incl ivicl uals'm'¡ sll ccinea (lh e latler found in low ab uncl anee). (Spivak e/ al. . 1994). The F. enigrna/icus The abundanee of infaun al po lychaetes is lu bes also provicle refuge to numerous affected by lh e rcels. JI. sill/i/is and L. aC II/a decrease in c1cn sit y while N. flll1'ia/i/is E. Schwindt & 0.0. Iribarne. Reel 01 Ficopomatus enigmaticus in Argentina 39

in crease as the result of distance (0.2 m, 2 m References and 6 m) to the reefs (Schwindt, I 997a). The meiofaunal organisms that inhabit the upper Adam, P. 1993. Saltmarsh Ecology. Cam sediment (approximately 3 cm) are dominated bridge Studies in Ecology. Cambridge by: ostracods, juvenile polychaetes, copepods University Press. Cambridge. harpacticoideos, nematodes, the gastropod Allen, F. E. 1953. Distribution of marine Littoridina parchappi and the amphipods invertebrates by ships. Aust. J. Mar. Melita palmata and Corophium insidiosus. Freshwater Res., 4: 307-316. The most abundant meiofaunal organisms are Bortolus, A., rribarne, O. & Martínez, M. ostracods and juvenile polychaetes (93% of 1998. Relationship between waterfowl and the total abundance), and their abundance is the seagrass Ruppia marítima in a not affected by the reefs (Schwindt, 1997a). southwestern Atlantic coastal lagoon. After rainfall periods, and fresh water drai nage from the creeks, there are also observed, Estuaries, 21 (4): (in press). ciliates, cladocerans, hydroids, gnathosto Botto, F., lribarne, O., Martínez, M., Delhey, mulids, the shrimp Palaeomonetes argentinus K. & Carrete, M. 1998. The effect of and hirudineans (Schwindt, 1997a). migratory shorebirds on the benthic fauna In conclusion the introduction of of three SW Atlantic estuaries. Estuaries, Ficopomatus enigmaticus in the Mar Chiquita 21 (4): (in press). coastal lagoon has provoked a significant. Coblentz, B. E. 1990. Exotic organisms: A change in the lagoons ecological and dilemma for conservation biology. Con sedimentological dynamics, affecting recrea servation Bio/., 4: 21-265. tional and sport navigation given the changes Cohen, A. N. & Carlton, J. T. 1998. Acce in depth. This pattern is similar to changes lerating invasion rate in a highly invaded reported for serpulid in other coastal lagoons estuary. Science, 279: 555-558. (Fornós et al., 1997). Furthermore,. all Fasano, J. L., Hernández, M. A., Isla, F. 1. & evidence suggests that the reefs have pro Schnack, E. 1. 1982. Aspectos evolutivos duced a large change in the ecology of·this y ambientales de la laguna Mar Chiquita environment, mainly by transforming a soft (Provincia de Buenos Aires, Argentina). bottom habitat into a structured hard bottom Oceanol. Acta N°SP: 285-292. environment (Schwindt, 1997a; 1997b). Fomós, J.1., Forteza, V. & Martínez-Taberner, A. 1997. Modern polychaete reefs in Western Mediterranean lagoons: Fico Acknowledgments pomatus enigmaticus (Fauvel) in the Albufera of Menorca, Balearic Islands. We thank to Dr. J. J. Fornós and A. Palaeogeogr. Palaeoclimatol. Palaeoecol., Bortolus for his useful comments on the 128: 175-186. manuscript and F. 1. Isla for his enthusiasm. Isla, F. 1. 1997. Seasonal behaviour of Mar Support for this project was provided by Chiquita tidal inlet in relation to adjacent grants from Percy Sladen Memorial Fund and beaches, Argentina. J. Coast. Res., 13: Lerner Gray Fund for Marine Research of the 1221-1232. American Museum of Natural History to E. Keene, W. C. Jr. 1980. The importance of a Schwindt, and Universidad Nacional de Mar reef-forming polychaete, Mercierella del Plata, CONICET (PIA No: 6097) and IFS enigmatica Fauvel, in the oxygen and (Sweden, No. A/2501-1/2) to O. Iribarne. E. nutrient dynamics of a hypereutrophic Schwindt was supported by a scholarship subtropical lagoon. Estuar. Coast. Mar. from crc (Argentina). Sci, 11: 167-178. Martínez, M. M. 1993. Las aves y la limnología. In: Boltovskoy, A. & López 40 Bol/. SOCo Hist. Nat. Balears, 41 (1998)

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