Bull. Southern CaliforniaAcad. Set 104(2), 2005, pp. 75-99 ©SouthernCaliforniaAcademyofSciences,2005 Structure and Composition of the Polychaete Community from Bahia San Quintin, Pacific Coast of Baja California, Mexico Victoria Diaz-Castaneda,1* A. de Leon Gonzalez,2 and E. Solana Arellano1 lDepartamento de Ecologia, CICESE, Km 107 Carr. Tijuana-Ensenada, Ap. Postal 2732, Ensenada, Baja California -Laboratorio de Biosistemdtica, Facultad Ciencias Biologicas, UANL San Nicolas de Los Garza, Nuevo Leon C. P. 66451 Mexico — Abstract. The diversity patterns of the polychaete fauna from a Pacific coastal lagoon were described. Polychaetes were collected in 1995 and 1998. This lagoon is formed by 2 arms: the western arm named Bahia Falsa and the eastern arm named Bahia San Quintin. 46 stations were sampled with a geological box corer. A total of 3,275 polychaetes, 28 families, 56 genera, and 104 species were iden- tified in 1995, and 3,168 polychaetes were collected in 1998, 21 families, 39 genera and 65 species. From all the macrofauna collected in both surveys, poly- chaetes represented 45.2%. From the species collected, 55% correspond to new records for the area. Families Dorvilleidae, Polynoidae, Oweniidae, Scalibreg- matidae, Sternapsidae and Sigalionidae present in 1995, were not in 1998 survey. The stations with higher abundances (> 100 specimens/0.02 m2) were located on the southern half of Bahia San Quintin. Species richness and diversity were also higher in San Quintin Bay. From the 30 families previously reported for San Quintin lagoon, 23 have been collected and 6 families were added: Ampharetidae, Oweniidae, Scalibregmatidae, Sternapsidae, Dorvilleidae and Sigalionidae. Fam- ilies not found in both surveys were: Paraonidae, Magelonidae, Apistobranchidae, Sphaerodoridae, Trichobranchidae, Chrysopetalidae and Arenicolidae. Results showed slightly lower redox potential values (—336 to +187 mV), slightly higher sediment temperatures (19.8°-22.1°C) and organic matter contents (0.3-4.1%) in 1998. From 1995 to 1998 a change in the composition and structure ofthe polychaete communities was noted; species richness diminished from 104 to 65 species. The trophic complexity changed with an increase of deposit-feeders, the abundance of other trophic categories decreased, indicating a loss of complexity. Significant changes in the abundance of some families were detected, some increased their abundances: Spionidae from 17% to 48%, Orbiniidae from 4% to 13%; other families decreased in terms of abundance and number of species: Lumbrinereidae from 11% to 1.4%, Nereididae from 9% to 1% and Sabellidae from 14% to 5%. These modifications altered the composition and structure of the polychaete com- munities in this lagoon. Increased anthropogenic disturbance (oyster culture, ag- riculture) and environmental variability due to the ENSO 97-98 may have af- fected recruitment and survival of some polychaete species. Corresponding author. E-mail: [email protected] 75 76 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Introduction Some lagoons, located along the Pacific coast of Mexico, present ideal hydro- logical and sedimentary characteristics which make them potential sites for aqua- culture. The San Quintin complex is one of these coastal lagoons that favor the development of bivalve aquaculture. It is considered ecologically important be- cause it is a nursery area for several fish species, a resting site for migrating birds which have lost most of their resting and feeding areas in the United States, and its high productivity and diversity, in part due to upwellings which supply nutri- ents periodically. It is environmentally important to obtain baseline scientific data that help understand how benthic communities function and how they change during different climatological conditions. The hydrology of San Quintin lagoon has been studied (Alvarez-Borrego & & Chee-Barragan 1976; Alvarez-Borrego et al. 1975; del Valle Cabrera-Muro & 1981 a, b; Farfan Alvarez-Borrego 1983). In contrast, there is a lack of infor- mation on macrofauna. One of the most neglected, major groups of marine in- vertebrates may be the polychaetous annelids that could be useful as indicators & of varying degrees of marine pollution (Tsutsumi 1990; Pocklington Wells 1992). Only three polychaete surveys were found on the literature: Reish (1963) 90 stations sampled in 1960 in Bahia San Quintin (BSQ eastern arm), Calderon- Aguilera & Jorajurfa-Corbo (1986) 11 stations sampled in 1981-82, 8 in BSQ and 3 in Bahia Falsa (BF western arm); and Diaz-Castaneda & Rodriguez Vil- lanueva (1998) 39 stations sampled in December 1992, 13 in BF and 26 in BSQ. Coastal marine benthic communities are threatened by human activities, and the present rate ofhabitat degradation is alarming. Given that only a small fraction of the benthic organisms that reside on or are buried in sediments have been described, it is likely that species are being lost without ecologists knowing they existed (Snelgrove 1999). Polychaetes constitute an important macrofaunal group in this lagoon comprising about 70% of the benthic biomass and individuals (Barnard 1970; Calderon-Aguilera & Jorajuria-Corbo 1986). More than 1,450 polychaete species are known from Mexico (Salazar-Vallejo et al. 1989; Diaz- Castafieda & Rodriguez-Villanueva 1998). Polychaetes are a significant compo- nent of all marine ecosysytems, they dominate soft-bottoms communities in terms of numbers of species and individuals. These annelid worms are important in food webs and in energy transference, both as predators and as important prey items for other animals, including crustaceans, fish and wading birds (Knox 1960). They present different feeding modes (carnivores, herbivores, omnivores, deposit-feed- ers, symbiotic chemoautotrophic bacteria), this plasticity could be the reason of their success in many environments (Beesley et al. 2000). Many species are im- portant bioturbators of sediment and facilitate the incorporation oforganic matter into sediments. Polychaetes show a spectacular diversity of reproductive and de- velopmental modes which allow them to live in different environments (Wilson 1991; Giangrande 1997). Because of their cosmopolitan distribution, polychaetes can be used as indicators of pollution and the "state of health" of a benthic community (Pearson & Rosenberg 1978; Reish 1980; Bellan et al. 1988; Pock- & & lington Wells 1992; Lardicci Rossi 1998). From a management perspective, they are useful organisms for identifying problem sites and for the assessment ofthe severity ofthe problem. They respond POLYCHAETES FROM THE PACIFIC COAST OF BAJA CALIFORNIA 77 to disturbance induced by different kinds of pollution, by exhibiting quantitative changes in assemblage distribution. Polychaetes can also be used as indicators of recovery of benthic environments from perturbations since in many cases they are major elements of the recolonization process (Diaz-Castaneda et al. 1989; & Diaz-Castaneda Almeda-Jauregui 1999). In spite of their importance in benthic communities few faunal studies have occurred in Mexico, in part because of identification problems due to lack of proper identification keys as well as the low number ofpolychaetologists (Salazar- & Vallejo et al. 1989; Pocklington Wells 1992). El Nino is an important phenomenon throughout the world. Its effects on ma- rine ecosysytems and organisms may go beyond temperature change. Invertebrates have complex life cycles in which certain life stages, and therefore the dynamics of entire populations, are at the mercy of various physical processes acting within the ocean-atmosphere system (Arntz & Tarazona 1990; Bakun 1996; Escribano et al. 2004). During El Nino Southern Oscillation (ENSO) 1997-1998, high tem- peratures and low nutrient concentrations resulted in widespread mortality ofgiant & kelp forests (Macrocystis pyriferd) (Tegner Dayton 1987) and other marine organisms in the region. Temperature anomalies greater than 1°C persisted con- tinuously for 8 months in the west coast of Baja California, in some cases anom- alies attained +3°C (Dayton et al. 1992). The purpose of this study is to describe the composition and structure of poly- chaete communities in San Quintfn lagoon in 1995 and 1998 before and after the El Nino 1997-98. Study Area San Quintin complex is a slightly hypersaline, highly productive coastal lagoon W located between 30°24'-30°30' N and 1 15°57'-1 16°01' in the Pacific coast of Km Baja California (Fig. 1). This lagoon has an area of 42 2 (4,200 hectares) and around 80% of it is covered by the eelgrass Zostera marina (Inclan-Rivadeneyra & Acosta-Ruiz 1988; Poumian-Tapia & Ibarra-Obando 1999). It has been ex- ploited for many years (mariculture) but it can still be considered a relatively non disturbed area, although oyster culture is increasing. The region is arid, with a mean annual rainfall of about 150 mm. About 90 percent of the rainfall occurs between October and March. Seagrass beds are important nursery areas for many species of fish and inver- tebrates, including several of economic importance (Stoner 1980 a, b; Orth & van Montfrans 1984, 1990). They also help to stabilize sediments thus reducing coastal erosion and are responsible for the composition and diversity of the seagrass infauna. The lagoon has the shape of an inverted fc'Y", it consists of two sub-basins: BF (west) and BSQ (east). BF has an average depth of 4 m whereas BSQ has an average depth of 8 m. The bay has extensive intertidal and shallow subtidal shoals m and channels up to about 10 deep extending along the length of each basin. It has a permanent entrance and exchanges water with the coastal ocean. During low tides around 20% of the seafloor is exposed. An important aspect of the marine environment is the pattern ofcoastal upwelling, which is strongest between May and August (Aguirre-Mufioz et al. 1999). The granulometric studies show that in shallow areas as well as to the north of both arms clay and silty-sand W 78 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 115° U.S.A. 30°3 MEXICO 30,:'- 30°25'N METROS 116°00' 115°55' J I I Fig. 1. Location of San Quintin lagoon on the Pacific coast of Baja California and sampling stations. predominate, whereas near the mouth very fine sands are more abundant. The channel sediments are highly diverse, going from medium to fine sand and silt & (Calderon-Aguilera 1992; Camacho-Ibar et al. 1997; Poumian-Tapia Ibarra- Obando 1999). The lagoon margins present a typical saltmarsh flora with Spartina foliosa and Salicornia virginica and other vascular plants (Dawson 1962; Barnard 1970). Material and Methods Forty six stations were sampled in December 1995 and April 1998, including 15 stations in BF and 31 in BSQ (Fig. 1). Samples were collected using a box corer (16 cm internal diameter, 13 cm depth, sampling area of 0.02 m2). Tem- perature and redox potential were measured immediately after collection of each POLYCHAETES FROM THE PACIFIC COAST OF BAJA CALIFORNIA 79 sample by probing 2-3 cm inside the sediments an electrode coupled to a field potentiometer and a thermometer. Sediments were sieved in the field using a 1.0 mm mesh size and retained material was fixed in 10% buffered formaldehyde. In the laboratory, samples were washed and transferred to 70% isopropanol. Differ- ent zoological groups and particularly polychaetes were then sorted and identified at species level whenever possible. Organic matter (percent of dry weight) was evaluated by ignition loss (Byers et al. 1978). Statistical methods were used to describe the structure and organi- zation of the polychaete communities within the bay. Shannon diversity index and Pielou equitability were calculated in order to study the structure and degree of organization of the communities (Shannon & Weaver 1963; Frontier 1985; Pielou 1977). Trophic groups were determined using Fauchald & Jumars (1979) and Rouse & Pleijel (2001). Olmstead and Tukey's test (Sokal & Rohlf 1995) was applied to analyze spatial distribution of polychaetes. This technique plots the frequency of appearance in each site sampled expressed as percentage against the density of organisms for each species. A mean average was calculated for both axes, resulting in four quadrants: I Frequent and abundant species, II Non frequent and abundant species, III Non frequent and non abundant species and IV Frequent and non abundant species. Stress predictability (Alcolado 1992) modeling was applied to establish the level of environmental stress existing in the bay. Environmental severity or stress was predicted based on values of diversity (FT) and evenness (J'), coupled with redox potential values. Ordination and classification methods were used to detect spatial patterns among the polychaete fauna. The relationship between sample stations is reflected by the position they display in factorial space; when the two stations were close to each other, they had more similar faunistic profiles (Frontier & Pichod-Viale 1993; Diaz-Castaneda et al. 1993). A factorial correspondence analysis was car- ried out on the faunistic data: abundance of species and 46 stations. Cluster anal- & & ysis using Pearson and Bray-Curtis coefficients (Bray Curtis 1957; Sokal Rohlf 1995) was employed to evaluate the level ofassociation ofdifferent stations and species. A non-metric multidimensional scaling (MDS) method was used for the.community ordination (Program PRIMER 5.1.1 for windows) since this tech- nique has demonstrated to be suitable for multiple ecological purposes (Clarke 1993; Clarke & Green 1988). The MDS is based on the calculation of similarity/ dissimilarity coefficients among samples, in this case, the similarity coefficient of Bray-Curtis. One data matrix was created for each sampling period using abun- dance per species. Data were treated using Primer Program 5.1.1 for windows and Statistica v. 5.0, after transformation to log10 (X + 1) as suggested by Frontier & (1983) and Legendre Legendre (1984). Results In 1995, the redox potential values (Eh) were negative in most of the stations. In the eastern arm they varied between —340 and +162 mV; BF presented values between — 320 to +161 mV. Sediment temperatures oscillated between 19.1 and 22.0°C. Organic matter values varied between 0.3 to 3.4% in BSQ and 0.1 to 3.1% in BF. In 1998 only 43% of stations were measured for Eh and temperature. 80 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Table 1. Physico-chemical values of San Quintin lagoon sediments. 1995 1998 Station Eh(mV) T°C % O.M. Eh(mV) T°C % O.M. 2 3.40 3 -340 21.8 2.03 -336 20.2 4.05 4 155 21.6 1.68 -208 21.1 2.90 5 -106 20.2 2.84 7 -160 20.9 1.86 -175 21.4 2.04 8 -196 20.8 1.38 -180 21.6 1.35 9 -245 20.8 2.01 -253 20.9 2.14 10 130 21.2 2.19 11 -73 21.0 1.10 12 -102 20.3 1.03 -98 20.8 1.66 13 -155 20.2 0.84 14 -197 21.0 1.32 -144 21.2 1.48 16 -187 19.9 2.35 17 -167 20.0 1.83 18 -109 20.1 2.04 -120 21.4 2.40 19 -219 20.6 2.12 21 -177 1.15 -174 21.5 1.57 22 -82 19.1 1.50 -92 21.4 1.92 24 162 21.7 2.46 25 -112 21.1 1.27 -126 21.7 1.94 26 -95 21.6 0.80 28 -62 20.5 1.38 103 21.5 1.45 29 66 21.1 0.91 30 -43 21.3 0.30 154 19.8 0.50 31 -69 21.5 0.42 32 -92 21.4 1.30 33 161 21.7 0.22 187 21.3 0.55 34 -24 21.3 2.14 35 -128 21.1 2.45 36 -85 21.6 1.60 -106 21.8 1.66 38 -123 21.6 2.90 -152 21.8 1.87 39 -136 21.2 2.78 40 -49 41 33 21.3 2.90 -190 20.9 2.70 42 -176 21.5 44 -320 21.2 3.27 -277 21.8 2.95 45 -308 22.1 4.11 46 -249 21.4 3.30 In the eastern arm the Eh varied between -336 mV and + 154, while the western arm presented values between — 308 and + 87 mV. Sediment temperatures were 1 in the range 19.8 to 22.1°C, while the organie matter content ranged between 0.5 to 4.0% in BSQ and 0.3 to 4.1% in BF (Table 1). These results show slightly lower Eh values and slightly higher temperature and organic matter contents in 1998. The lists of species found in each survey are given in Table 2. In 1995, a total of 8,680 benthic organisms were collected, of which 38% were polychaetes, 36.5% were crustaceans and 27.4% were molluscs. The 3,275 polychaetes col- POLYCHAETES FROM THE PACIFIC COAST OF BAJA CALIFORNIA 81 lected and identified belonged to 28 families, 56 genera and 104 species (Table 2). The families best represented were Capitellidae (19%), Spionidae (17%), Sa- bellidae (14%), Lumbrinereidae (11%), Nereididae (9%), Cossuridae (8%) and Syllidae (8%). The 10 top dominant species were Prionospio heterobranchia (331), Chone infundiliformis (295), Mediomastus californiensis (264), Cossura Candida (236), Scoletoma crassidentata (222), Exogone lourei (206), Capitella capitata (147), Armandia brevis (130), Neanthes arenaceodentata (121), Chone mollis (117). The first eight species constitute 55% of the total abundance, the first five have been reported as abundant in previous studies (Reish 1963; Cald- & eron-Aguilera 1986; Diaz-Castaneda Rodriguez-Villanueva 1998). Reish (1963) found six species that constituted the dominant bay species on the basis ofnumber of specimens. These were, in decreasing order of importance, Prionospio malm- greni, Exogone verugera, Cossura Candida, Capitia ambiseta, Scoloplosacmeceps and Fabricia limnicola. Calderon-Aguilera (1992) reported five numerically dom- inant species: Exogone occidentalis, Pseudipolydora ketnpi, Scoloplos acmeceps, Prionospio heterobranchia and Neanthes arenaceodentata. In April 1998, a total of 5,584 benthic organisms were collected, of which 56.7% were polychaetes, 27.2% were crustaceans and 7.5% were molluscs. The 3,168 polychaetes identified, belonged to 21 families, 39 genera and 65 species (Table 2). The families best represented were Spionidae (47.6%), Capitellidae (12.3%), Syllidae (10.5%), Paraonidae (7%) and Orbiniidae (6.8%). The first six species constitute around 75% of the total abundance. The ten top dominant spe- cies were Prionospio heterobranchia (832 specimens), Polydora websteri (548), Scoloplos acmeceps (370), Exogone lourei (291), Mediomastus californiensis (273), Cirriformia spirabrancha (128), Capitella capitata (68), Chone mollis (62), Megalomma pigmentum (59) and Fabricinuda limnicola (50). The following families present in 1995 were not found in the 1998 survey: Dorvilleidae, Polynoidae, Oweniidae, Scalibregmatidae, Sternapsidae and Siga- lionidae. Some of these families have species that are carnivorous. The increase in temperature in 1998 is related to a diminution of prey items which in turn may have affected their abundances. & Olmstead Tukey's graph is only presented at the family level (Fig. 2a), because there were too many species to produce a clear graph. In 1995 and 1998 the polychaete families were placed in three out of four possible categories: dom- inant, restricted and rare. In 1995, in quadrant I (frequent and abundant), 6 poly- chaete families were characterized as dominant. Spionidae, Nereididae, Sabellidae, Lumbrinereidae, Capitellidae and Syllidae families displayed high densities and wide distribution throughout the lagoon. The families Spionidae, Capitellidae, and Sabellidae presented the highest densities and combined accounted for 45% of the total abundance of polychaetes. Ten families restricted to certain areas of the lagoon were located in quadrant II (non-frequent and abundant) and corresponded to 32% of all families. Within quadrant III (non-frequent and non-abundant), 12 polychaete families were located, classified as rare oroccasional. No families were located in quadrant IV corresponding to frequent and non-abundant families. Ap- proximately 35% of species were located in quadrant I (36 species). In 1998 (Fig. 2b), in quadrant I, only 3 polychaete families were characterized as dominant. The families Spionidae, Orbiniidae and Capitellidae displayed high densities and 82 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Table 2. Polychaete species from San Quintin lagoon, Baja California. Species 1995 1998 AMPHARETIDAE Ampharete labrops Harman, 1961 x Ampharete sp x Amphicteis acutifrons Grube, 1850 x Amphicteis sp Grube, 1850 x CAPITELLIDAE Capitella capitata Fabricius, 1780 x x Mediomastus californiensis Hartman, 1944 x x Mediomastus sp x x Notomastus magnus Hartman, 1947 x Notomastus tenuis Moore, 1909 x x Notomastus sp x CIRRATULIDAE Aphelochaeta marioni Saint-Joseph, 1894 x Aphelochaeta sp x Cirriformia spirabranchia Moore, 1904 x x Monticellina tesselata Harman, 1960 x Protocirrineris socialis Blake, 1996 x Protocirrineris sp x COSSURIDAE Cossura Candida Hartman, 1955 x x Cossura sp A x x DORVILLEIDAE Dorvillea sp x EUNICIDAE Lysidice ninetta Verril, 1900 x Marphysa disjuncta Harman, 1961 x M. sanguinea Montagu, 1815 x x Marphysa sp x x FLABELLIGERIDAE Pherusa capulata Moore, 1909 x x Piromis arenosus Kinberg, 1867 x x Piromis sp x GLYCERIDAE Glycera americana Leidy, 1855 x x G. tenuis Hartman, 1944 x x GONIADIDAE Goniada brunnea Treadwell, 1906 x G. littorea Hartman, 1950 x x HESIONIDAE Podarkeopsis glabra Hartman, 1961 x x Podarkepugettenisis Johnson, 1901 x x LUMBRINERIDAE Scoletoma crassidentata Fauchald, 1970 x S. erecta Moored 1904 x S. monroi Fauchald. 1970 x S. tetraura Schmarda, 1860 x x POLYCHAETES FROM THE PACIFIC COAST OF BAJA CALIFORNIA 83 Table 2. Continued. Species 1995 1998 MALDANIDAE Axiothella rubrocincta Johnson, 1901 x Axiothella sp Verril, 1900 x Clymenura gracilis Moore, 1923 x Euclymeninae sp A Ardwidsson, 1906 x Isocirrus longiceps Moore, 1923 x Maldane sp x NEPHTYIDAE Nephtys caecoides Hartman, 1938 x x Nephtys sp x NEREIDIDAE Neanthes caudata delle Chiaje, 1828 x x Nereis latescens Chamberlin, 1919 x N. pelagica Linne, 1758 x Nereis sp x Platynereis bicanaliculata Baird, 1863 x P. marphysa x OENONIDAE Arabella tricolorMontagu, 1804 x x A. pectinata Fauchald, 1970 x Drilonereisfalcata Moore, 1911 x D. longa Webster, 1879 x D. mexicana Fauchald, 1970 x Drilonereis sp x Notocirrus californiensis Hartman, 1944 x ONUPHIDAE Kinbergonuphis sp x x OPHELIIDAE Armandia bioculata Hartman, 1938 x A. brevis Moore, 1906 x x Opheliapulchela Tebble, 1953 x Polyophthalmuspicuts Dujardin, 1839 x ORBINIDAE Leiioscoloplos mexicanus Fauchald, 1972 x L. normalis Day, 1977 x Naineris grubei Gravier, 1908 x Phylofelix Kinberg, 1866 x P. ornatus Verril, 1873 x Scoloplos acmeceps Chamberlain, 1919 x x S. armigerMiiller, 1776 x S. ohlini Ehlers, 1901 x S. texana Maciolek & Holland, 1978 x OWENIIDAE Owenia collaris Hartman, 1955 x PHYLLODOCIDAE Eieonepacifica Hartman, 1936 x Eteone sp x x Eulalia bilineata Johnston, 1840 x Eumida sp x 84 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Table 2. Continued. Species 1995 1998 POLYNOIDAE Harmothoe imbricata Linne, 1767 x Harmothoe sp x SABELLIDAE Chone infundibuliformis Kroyer, 1856 x C. mollis Bush, 1904 x x Fabricinuda limnicola Hartman, 1951 x x Megalommapigmentum Reish, 1963 x x SCALIBREGMATIDAE Scalibregma sp x SIGALIONIDAE Sthenelaisfusca Johnson, 1897 x SPIONIDAE Aporionospiopigmaeus Hartman, 1961 x Boccardiella hamata Webster, 879 x x 1 Microspiopigmentata Reish, 1959 x Minuspio cirrifera Wiren, 1883 x Polydora socialis Schmarda, 1861 x P. websteri Hartman, 1943 x Prionospio heterobranchia Reish, 1959 x x P. lighti Maciolek, 1985 x x Pseudopolydorapauchibranchiata Okuda, 1937 x Scolelepis squamata Muller, 1806 x Spiophanes bombyx Claparede, 870 x 1 S. duplex Chamberlain, 1919 x x S. missionensis Hartman, 1941 x Spiopacifica Blake & Kudenov, 1978 x Spio sp x SYLLYDAE Cicese sphaerosylliformis Diaz & San Martin, 2001 x x Eusyllis sp x Exogone lourei Berkeley & Berkeley, 1938 x x Grubeosyllis mediodentata Westheide, 1974 x x Pionosyllis sp x x Sphaerosyllis californiensis Hartman, 1966 x Syllis aciculata Treadwell, 1945 x S. gracillis Grube, 1840 x x S. heterochaeta Moore, 1909 x Syllis sp x TEREBELLIDAE xx Eupolymnia nebulosa Montagu, 1818 x Pista alata Moore, 1909 x x Pista sp Polycirrus sp x