Journal of Coastal Research 24 5 1281–1288 West Palm Beach, Florida September 2008

Spatial Variation in Stable Isotopes (␦13C and ␦15N) in Marine along the Coast of Havana City: Evidence of Human Impacts from Harbor and River Waters Consuelo Aguilar†, Gaspar Gonza´lez-Sanso´n†, Isabel Faloh†, and R. Allen Curry‡*

†Centro de Investigaciones Marinas ‡Canadian Rivers Institute Universidad de La Habana University of New Brunswick 16 No. 114 Biology Department Playa 1300, Ciudad Habana, Cuba Fredericton, New Brunswick, Canada E3B 6E1 [email protected] ABSTRACT AGUILAR, C.; GONZA´ LEZ-SANSO´ N, G.; FALOH, I., and CURRY, R.A., 2008. Spatial variation in stable isotopes (␦13C and ␦15N) in marine fish along the coast of Havana City: evidence of human impacts from harbor and river waters. Journal of Coastal Research, 24(5), 1281–1288. West Palm Beach (Florida), ISSN 0749-0208.

We examined the hypothesis that nutrients from land sources are enhancing the food supply for fish in coastal reefs of northwestern Cuba. Spatial variation in stable isotope ratios (␦13C and ␦15N) was investigated at two sites heavily impacted by mixed pollution sources in Havana City, Cuba, and two reference sites. Significant differences in isotope signatures were found among sites for territorial , e.g., ␦15N was consistently enriched at impacted sites. The most plausible explanation is enriched nitrogen and carbon sources in the food web derived from organic pollution of the coastal zone by human wastewaters. This supports earlier findings that fish were larger in the vicinity of the harbor because of nutrient additions due to sewage that can increase ecosystem productivity and enhance growth of fish. It is also evidence of the direct land-to-water linkage in coastal zone food webs and illustrates how additional nutrients may affect marine food web functions.

ADDITIONAL INDEX WORDS: Human impacts, Caribbean reefs, bicolor damselfish, bluehead , slippery dick, yellowhead wrasse, Chromis.

INTRODUCTION (ARECES and TOLEDO, 1985; BELTRA´ N,RUIZ, and VEGA, 1998; GONZA´ LEZ, 1991). Marine eutrophication is one of the most significant im- Recent research by AGUILAR (2005) on bicolor damselfish pacts of humans in coastal zones (ÆRTEBJERG et al., 2001; (Stegastes partitus, Poey), bluehead wrasse (Thalassoma bi- COGNETTI, 2001). The impact of nutrient enrichment and fasciatum, Bloch), slippery dick (H. bivittatus, Bloch), and yel- eventually eutrophication depends on the balance between lowhead wrasse (H. garnoti, Valenciennes) indicated they are the positive (more food) and the negative (e.g., hypoxia and heavier and longer at sites near Havana Harbor and the Al- increase of suspended solids) consequences of adding organic mendares River (Havana City), two major sources of coastal material, e.g., urban, agricultural, or industrial runoff, into pollution. These findings suggest an increased food supply the coastal zone (BREITBURG, 2002). Untreated sewage is a resulting from the eutrophication of these coastal waters. major cause of eutrophication in coastal zones and can be a Stable isotope analyses can elucidate trophic relationships source of toxic substances that affect fish health (e.g., ALBER- in aquatic (CONOLLY, 2003; LEE, 2000; PETERSON TO et al., 2004; AMISAH and COWX, 2000; SCHMIDT et al., and FRY, 1987; VOB and STRUCK, 1997) because ␦13Cisan 1999). effective indicator of food source and ␦15N is an indicator of The nearshore marine environment along the coast of Ha- trophic level (e.g., MINAGAWA and WADA, 1984; VANDER ZAN- vana City, Cuba, is impacted by many human activities, in- DEN et al., 1999; YAMAMURO,KAYANNE, and MINAGAWA, cluding overfishing and pollution from wastewater (sewage 1995; but see also MCCUTCHAN et al., 2003). PETERSON and industrial) and land activity runoff (urban and agricul- (1999) observed that human sewage in the marine environ- tural). Significant changes in fish assemblages of fringe coral ment creates an isotopic signature that may be useful for reefs off Havana City have been recently reported (AGUILAR tracking impacts. Research has demonstrated that stable iso- et al., 2004). Changes were associated with distance from Ha- tope ratios can help to trace inputs of carbon and nitrogen vana Harbor, which is the largest pollution source in the area from land-based activities, including sewage discharge in that includes organic matter and nutrients from sewage, crude oil from a refinery, heavy metals, and fine sediments aquatic ecosystems (DARNAUDE,SALEN-PICARD, and HAR- MELIN-VIVIEN, 2003; RAU et al., 1981; VAN DOVER et al., 1992; VIZZINI and MAZZOLA, 2004). For example, the enrich- DOI: 10.2112/07-0832.1 received 12 February 2007; accepted in re- 15 vision 11 July 2007. ment of nitrogen ( N) could provide a means of assessing the * Corresponding author. degree of exposure of aquatic organisms to municipal sewage 1282 Aguilar et al.

MATERIALS AND METHODS Study Areas The main study area was the northern coast of Cuba, west of Havana City (Figure 1). In this region, the upper subtidal zone is a submarine terrace with a gentle slope to 8 m deep. The slope increases significantly until 12–15 m, where a sandy plain begins. The terrace is about 300 m wide and di- vided into four distinct biotopes existing as bands running parallel to the coastline (AGUILAR et al., 2004): ● Echinometra: The most shoreward and shallowest biotope. The main feature of this zone is the huge population of the sea urchin, Echinometra lucunter, a species that excavates the rocky bottom for shelter. ● Rocky plain: A biotope whose main feature is the smooth rocky bottom that is covered by seaweed seasonally. ● Terrace edge: The area just before the point where the bot- tom slope becomes steeper. ● Terrace base: The deepest biotope, where the rocky wall of the terrace meets the sandy plain. Figure 1. Location of study sites (black circles) in western Cuba. Sam- pling sites: BR ϭ Havana Harbor, C30 ϭ Miramar, Ca ϭ Cantiles Key, In the vicinity of Havana City, there were three sampling ϭ RIO Almendares River. stations. The entrance of Havana Harbor, site BR, is heavily impacted by the polluted waters from this industrial harbor (23Њ8.864Ј N, 82Њ21.576Ј W; Figure 1). Waters are eutrophic; in the receiving environment (e.g., LAKE et al., 2001; WAY- coral growth is low; sponge density is high; polychaetes are LAND and HOBSON, 2001). numerous (Table 1). Site RIO was the eastern coastal area at We hypothesized that nutrients coming from land-based the mouth of Almendares River (23Њ8.250Ј N, 82Њ24.565Ј W; activities in the area around Havana City are enhancing the Figure 1). A dominant coastal current flowing from SW to food supply for fish in coastal coral reefs. We present results NW directs river discharge to the NW. The river is heavily for stable carbon and nitrogen isotope ratios of selected fish polluted as it flows through the city with organic matter from species and their potential food items at several sites varying sewage, heavy metals, and other sources of unknown nature in sewage inputs along the coast of Havana City. We observed from several industries (AGUILAR and GONZA´ LEZ-SANSO´ N, larger fish than AGUILAR (2005) and predicted that fish were 2002). There is greater coral cover and colony size and num- larger in the vicinity of the harbor because of its enriched ber than BR, but these indicators are still low (Table 1). Algal environment. We predicted that stable isotope levels would cover increases at this site. Site C30 was the area off 30th reflect this proximity to human inputs, e.g., elevated ␦15N and Street in Miramar, Havana City (23Њ7.587Ј N, 82Њ25.793Ј W; lower ␦13C, and thus provide additional evidence that nutri- Figure 1). This site was considered a reference site in the ents from human activities on land are entering coastal reef northern zone. It is an open area with good currents running food webs. parallel to the coast toward the city (AGUILAR et al., 2004).

Table 1. Key features of substrate and benthos at the sampling stations of the northern coast; see Figure 1.

Sampling Sites

Variable BR RIO C30 Comments Complexity index† 1.17 1.05 1.16 The complexity of substrate is very similar in all sites. Number of coral species 3 11 17 Higher number of species, higher density of colonies, bigger colonies, and Density of coral colonies (per m2) 0.4 2.4 6.3 higher cover are indicators of better environmental conditions in coral Coral size (cm) 10.3 15.4 25.8 reefs. Coral cover (%) 0.0 0.6 6.5 Density of sponges (ind/m2) 11.2 2.0 5.9 In general, more sponges and fewer gorgonaceans are predicted at eutro- Density of gorgonaceans (ind/m2) 0.3 0.1 2.1 phic sites. Algal cover (%) 62.8 97.1 45.6 Algal cover is positively correlated with nutrient levels. Polychaete cover (%) 35.2 0.0 0.0 Both are considered good indicators of organic pollution. Cyanobacteria cover (%) 6.8 0.0 0.0 (Unpublished data provided by E. de la Guardia and P. Gonza´lez-Dı´az, Center of Marine Research, University of Havana, Cuba). BR ϭ Havana Harbor, C30 ϭ Miramar, RIO ϭ Almendares River. † Using the chain method.

Journal of Coastal Research, Vol. 24, No. 5, 2008 Human Impacts on Cuban Reef Fish 1283

␦ ϭ Ϫ ϫ No significant pollution sources exist near the shore, except X [(Rsample/Rstandard) 1] 1000 delta, for a small, intermittently flowing drainage pipe receiving where X ϭ 13Cor15N and R ϭ 13C/12Cor15N/14N. illegal sewage effluents. Effects on the subtidal zone are not Replicates of commercially available isotope standards apparent. Benthos is well developed with large corals and a yielded results that were both accurate and precise (Inter- high density of colonies, including gorgonaceans (Table 1). A national Atomic Energy Agency). second reference site, site Ca, was located in the southwest- Algae and were also sampled for stable iso- ern coast of Cuba at the fringe reef offshore of the Cantiles topes at each site. Specimens were collected by hand. Algae Key (Figure 1; 21Њ34.239Ј N, 82Њ01.724Ј W). This site is lo- and soft-body invertebrates were preserved whole. Mollusks cated approximately 70 km from any urban discharge zone, were separated from the shell, and muscular tissue was pre- and the reef appears to be unimpacted by human inputs. served. Only soft tissue was used in the case of . For corals, the tissue was separated from the skeleton by Food and Isotope Analyses means of a water pick. All samples were preserved in 70% ethanol. Sample preparation was as described for fish. Fish for all analyses were collected using scuba diving and dipnets. Fish were collected at depths of 10–12 m, coinciding Data Analysis with the terrace-base biotope. Target fish species were bicolor damselfish (S. partitus), blue chromis (Chromis cyanea), and The dissimilarity of diet composition was assessed using brown chromis (C. multilineata) from the family Pomacentri- cluster analysis based on frequency-of-occurrence data. The Ϫ dae; bluehead wrasse (T. bifasciatum), slippery dick (H. biv- dissimilarity index was 1 rs, where rs is Spearman’s rank ittatus), and yellowhead wrasse (H. garnoti) from the family correlation coefficient (ZAR, 1996). The unweighted pair- Labridae; squirrelfish (Holocentrus adscencionis) and long- group method with arithmetic mean (UPGMA) algorithm was spine squirrelfish (H. rufus) from the family Holocentridae; used for hierarchical grouping. Calculations and graphs were coney (Epinephelus fulvus) from the family Serranidae; and made using Statistica 5.0. ocean surgeonfish (Acanthurus bahianus) from the family Differences in ␦13C and ␦15N among sites were tested using Acanthuridae. Not all species were present in sufficient num- one-way, fixed factor analysis of variance followed by a pair- bers for collections at every site. Stomach content analyses wise Student-Newman-Keuls (SNK) comparison of means were made for the damselfish (Pomacentridae) and (UNDERWOOD, 1997). Assumptions of normality and homo- (Labridae). For comparative purposes, feeding habits of the geneity of variances were examined following the criteria of other four species included in stable isotope analyses were ZAR (1996) and UNDERWOOD (1997). Mean values are re- classified after RANDALL (1967), i.e., ocean surgeonfish is a ported with 1 standard error. Analyses were performed using typical herbivore of the reefs, feeding mainly on benthic algae SPSS 10.0. and some phanerogams; squirrelfish consume crabs and shrimps; and coney feed mainly on fish, shrimps, crabs, and RESULTS stomatopods. Diet Analyses Fish were sacrificed in the field and returned to the labo- ratory on ice from January to April, 2003. The total length Diets varied among species and sites (Table 2), but the of each individual was measured (nearest 1 mm). The stom- dominant food items were benthic algae and small pelagic ach was extracted and preserved in 70% ethanol for later and benthic animals. Four basic groups of fish were apparent analysis of diet. A portion of the dorsal epaxial muscle was based on feeding habits. preserved in 70% ethanol for stable carbon and nitrogen iso- ● Group 1: Bicolor damselfish were omnivorous, feeding tope analyses. mainly on benthic algae and small crustaceans dominated Stomach contents were analyzed for a subset of fish at each by planktonic copepods. The most frequently consumed al- site. Additional samples were available from previous studies gae were the genera Cladophora, Ceramium, Dictyota, Gel- (March 1999 to April 2002, C. AGUILAR, unpublished data). idium, Griffithsia, and Hypnea. The species Asparogopsis Food items were identified to the lowest taxon possible using taxiformis in the sporophyte stage was also a food item. microscopes. Many of the items were small, partially digest- Copepods were mainly calanoids with some harpacticoids ed, and fragmented; therefore, the frequency-of-occurrence present. Eggs were found in stomachs (elliptical in most method (HYSLOP, 1980) was used to report results. cases, with some spherical) and appear to be both benthic For stable isotope analyses, muscle samples were dried at (e.g., a peduncle was present) and pelagic (e.g., an oil drop) 50ЊC for 48 hours and then ground into a fine powder with a in origin. Spearman’s rank correlation coefficients for pairs mortar and pestle. An aliquot of 200 ␮g was taken from every of sites yielded significant correlations for bicolor damsel- ϫ ϭ Ͻ sample and packed into a 3 mm 5 mm tin cup. Samples fish (Figure 2; C30–BR: rs 0.93, p 0.01; C30–RIO: rs ϭ Ͻ ϭ Ͻ were combusted to gas using a Thermoquest NC 2500 ele- 0.95, p 0.01; RIO–BR: rs 0.91, p 0.01). mental analyzer, and gases were submitted via a continuous ● Group 2: Bluehead wrasse consumed mainly small crus- flow of helium to a Finnigan MAT Delta Plus isotope-ratio taceans and copepods. Algae were absent. Other food items mass spectrometer for carbon and nitrogen analyses at the included nematodes, polychaetes, isopods, shrimps, fish Stable Isotopes in Nature Laboratory, University of New eggs, and fish scales. Insufficient data was available for Brunswick. Isotope ratios are reported as correlation analyses.

Journal of Coastal Research, Vol. 24, No. 5, 2008 1284 Aguilar et al.

Table 2. Frequency of occurrence (%) of food items in stomachs of damselfish and wrasses.

Fish Sampled

Thalassoma Stegastes Halichoeres Chromis Chromis Food Item bifasciatum partitus bivittatus garnoti cyanea multilineata N: 52 380 14 39 46 51 TL range (mm): 43–83 28–88 49–152 38–176 27–42 23–103 Cyanobacteria 7.9 Algae 44.4 14.3 Foraminifera 25.0 2.6 Anthozoa 2.6 57.1 41.4 Gastropoda 14.3 27.6 Pelecypoda 7.1 13.8 Nematoda 4.9 Annelida 6.9 Polychaeta 2.4 3.4 Crustacea 12.2 11.4 12.9 37.5 Copepoda 9.8 34.9 37.5 65.8 Tanaidacea 2.6 Isopoda 2.4 Decapoda 10.3 Brachiura 6.9 Natantia 2.4 Insecta 4.9 Equinodermata 13.8 Equinoidea 14.3 Ophiuroidea 7.1 Fish eggs 2.4 18.8 44.7 Fish scales 7.3 8.7 3.4 N ϭ sample size, TL ϭ total length of individual fish.

● Group 3: Slippery dick and yellowhead wrasse fed mainly Mean values of ␦15N ranged from 6.6 Ϯ 0.1 (blue chromis) to on small mollusks. Most of the food remains were frag- 12.2 Ϯ 0.2 (squirrelfish). mented, but it was possible to identify the gastropods Mod- Differences in ␦13C among sites were sometimes statisti- ulus modulus, Nassarius antillarum, Columbella mercato- cally significant, but a consistent pattern of spatial variation ria, Rissoina sp., Retusa sp., and unidentified species of the along a gradient of human impact was not apparent (Table family Turridae. Pelecypods were Laevicardium laeviga- 3). Most values at impacted sites (BR, RIO) were depleted tum, Gouldia cerina, Pitar fulminatus, Codakia orbicularis, compared to those at reference sites (C30, Ca). Chione cancelata, and species of families Lucinidae and Ve- Differences in ␦15N among sites were more apparent in bi- neridae. Other infrequent food items were polychaetes, color damselfish and wrasses. Mean values were always high- crustaceans, and . Insufficient data was avail- est at the entrance of Havana Harbor (BR) and declined with able for correlation analyses. distance from the harbor (Table 3). The south-shore site, Ca, ● Group 4: Blue and brown chromis were both planktivorous. always had the lowest values. Copepods were the most frequently occurring food item, Ocean surgeonfish had isotope signatures significantly low- followed by pelagic fish eggs and small unidentified crus- er at the most impacted sites near the entrance of the harbor, taceans. Insufficient data was available for correlation BR, and mouth of the urban river, RIO (Table 3). For the analyses. squirrelfish and coney, no significant differences were found among sampling sites. Cluster analysis of diet composition identified two main groups (Figure 3). One group fed mainly on benthic algae and small invertebrates other than mollusks. Within this group, DISCUSSION a distinct subgroup was formed by the planktivorous species. The food of damselfish and wrasses, which dominated our The second group was species that fed mainly on mollusks. reef communities, has been reported by many authors (BEE- BE and TEE VAN, 1928; EMERY, 1973; FEDDERN, 1965; HIX- Isotope Analyses ON and BEETS, 1993; HIXON and CARR, 1997; LONGLEY and Stable isotope ratios were variable among nonfish organ- HILDEBRAND, 1941; RANDALL, 1967; SIERRA,CLARO, and isms (Table 3). Mean values of ␦13C ranged from Ϫ16.8 Ϯ 0.3 POPOVA, 2001; WALDNER and ROBERTSON, 1980; WELLING- (gastropods) to Ϫ6.2 Ϯ 0.8 (ophiuroids). Mean values of ␦15N TON and VICTOR, 1989, cited by BOOTH and HIXON, 1999). ranged from 5.3 Ϯ 0.7 (crabs) to 8.2 Ϯ 0.2 (myscids). For fish In western Cuba, diets were similar; therefore, we have con- (Table 3), mean values of ␦13C ranged from Ϫ17.5 Ϯ 0.1 fidence that the stable isotope measures, which are also com- (brown chromis) to Ϫ14.5 Ϯ 0.1 (longspine squirrelfish). parable to existing reports (e.g., COCHERET DE LA MORINIE` RE

Journal of Coastal Research, Vol. 24, No. 5, 2008 Human Impacts on Cuban Reef Fish 1285

Table 3. Total body length and ␦13Cand␦15N in fish, algae, and invertebrates of western Cuba. Mean, standard error, and sample sizes are given, as are results of statistical comparisons among sites; see Figure 1.

␦13C ␦15N

TL (mm) Mean SE N F p SNK† Mean SE F p SNK† Acanthurus bahianus BR 164–192 Ϫ16.48 0.32 10 4.4 0.02 a 10.40 0.15 6.4 0.01 a RIO 163–229 Ϫ16.34 0.31 11 a 9.73 0.39 a C30 257–295 Ϫ15.43 0.21 12 b 11.61 0.48 b Stegastes partitus BR 35–74 Ϫ16.39 0.11 11 29.0 Ͻ0.01 a 8.15 0.15 62.8 Ͻ0.01 a RIO 56–67 Ϫ17.24 0.14 10 b 6.84 0.10 b C30 35–74 Ϫ15.86 0.32 11 a 6.80 0.07 b Ca 43–61 Ϫ14.42 0.21 10 c 6.04 0.11 c Thalassoma bifasciatum BR 58–131 Ϫ16.73 0.13 13 47.7 Ͻ0.01 a 8.41 0.19 57.3 Ͻ0.01 a RIO 50–113 Ϫ17.28 0.08 10 b 7.86 0.10 b C30 54–96 Ϫ17.50 0.05 10 b 6.65 0.07 c Ca 50–105 Ϫ15.91 0.10 9 c 6.27 0.09 c Halichoeres bivittatus BR 63–131 Ϫ14.77 0.06 11 21.6 Ͻ0.01 a 10.96 0.18 29.9 Ͻ0.01 a RIO 58–145 Ϫ16.06 0.19 11 b 9.84 0.14 b C30 61–114 Ϫ15.39 0.13 11 c 9.22 0.16 c Halichoeres garnoti BR 60–182 Ϫ15.37 0.16 10 13.0 Ͻ0.01 a 10.62 0.16 5.8 0.01 a RIO 55–165 Ϫ15.77 0.14 13 a 10.24 0.14 a, b C30 61–125 Ϫ14.79 0.14 16 b 9.86 0.15 b Chromis cyanea BR 40–83 Ϫ17.62 0.25 4 5.2 0.01 a 7.05 0.20 22.4 Ͻ0.01 a RIO 43–90 Ϫ17.75 0.13 6 a 6.73 0.07 a C30 22–72 Ϫ17.19 0.07 11 b 6.90 0.07 a Ca 22–90 Ϫ17.09 0.18 7 b 5.80 0.16 c Chromis multilineata RIO 32–130 Ϫ17.60 0.21 6 0.4 0.68 N/A 7.10 0.13 30.9 Ͻ0.01 a C30 39–130 Ϫ17.29 0.41 5 7.21 0.25 a Ca 32–38 Ϫ17.45 0.05 7 5.83 0.05 b Epinephelus fulvus BR 72–244 Ϫ15.36 0.05 11 36.4 Ͻ0.01 a 10.39 0.11 2.9 0.07 N/A RIO 153–197 Ϫ15.94 0.06 10 b 10.05 0.04 C30 158–220 Ϫ15.07 0.09 13 c 10.27 0.11 Holocentrus adscencious BR 172–200 Ϫ14.87 0.06 11 3.5 0.06 N/A 12.13 0.06 2.6 0.11 N/A RIO 207–283 Ϫ14.67 0.16 7 12.68 0.58 C30 270–276 Ϫ14.32 0.01 2 11.01 0.03 Holocentrus rufus BR 208–256 Ϫ14.47 0.12 6 0.5 0.49 N/A 11.56 0.22 0.1 0.79 N/A RIO 182–242 Ϫ14.53 0.15 12 11.50 0.11 Polychaetes BR Ϫ15.62 0.24 5 2.1 0.95 N/A 7.78 0.61 9.4 Ͻ0.01 a RIO Ϫ16.06 0.52 5 5.93 0.06 b C30 Ϫ15.83 1.16 4 5.72 0.44 b Ca Ϫ15.29 2.30 2 3.96 0.28 c Gastropods BR Ϫ14.96 0.30 5 11.7 Ͻ0.01 a 8.72 0.37 53.8 Ͻ0.01 a RIO Ϫ17.68 0.50 4 b 7.70 0.25 b C30 Ϫ17.63 0.32 5 b 6.37 0.32 b Ca Ϫ16.98 0.45 4 b 3.29 0.24 c Algae BR Ϫ12.02 0.83 9 1.4 0.26 N/A 7.78 0.18 81.8 Ͻ0.01 a RIO Ϫ9.02 1.95 9 6.76 0.29 b C30 Ϫ12.76 1.00 8 5.54 0.27 c Ca Ϫ9.92 1.68 9 2.73 0.22 d Sample sites: BR ϭ Havana Harbor, RIO ϭ Almendares River, C30 ϭ Miramar, and Ca ϭ Cantiles Key, F ϭ calculated ratio of between/within sums of squares, N ϭ sample size, SE ϭ standard error, SNK ϭ Student-Newman-Keuls, TL ϭ total body length (mm). † Similar letters are not significantly different, ␣ϭ0.05.

et al., 2003; REN˜ ONES,POLUNIN, and GONI, 2002), reflect al- these species, we hypothesize that smaller invertebrates, terations of carbon and nitrogen cycling in our reef ecosys- mainly from zooplankton or benthos, with a lower trophic lev- tems. el are the main prey, i.e., the planktonic copepods observed Five fish species—both squirrelfish, slippery dick, yellow- in their diets. COCHERET DE LA MORINIERE et al. (2003) re- head wrasse, and coney—showed an enrichment of 3–5‰ for port ␦13C ϭϪ13.5 and ␦15N ϭ 3.2 (approximated from their ␦15N in relation to invertebrates. The value agrees with the Figure 2) for sea grass zooplankton in Curacao (southern Ca- mean enrichment value between two adjacent trophic levels ribbean Sea). These ratios agree with our observed zooplank- typical for marine food webs (e.g., FRY, 1988; MINAGAWA and ton consumers based on an enrichment of 3‰ in ␦15N (as per WADA, 1984; PETERSON and FRY, 1987) and supports the hy- VANDER ZANDEN et al., 1999). The ocean surgeonfish were pothesis that these groups are the main food inconsistent with enrichment from our sampled algae, prob- source for these five species. Four other species—both ably because the algal species sampled were not those pre- Chromis spp., bicolor damselfish, and bluehead wrasse—had ferred by ocean surgeonfish. ␦15N comparable to those of the invertebrate groups. For Differences in ␦13C values among sites weakly suggest that

Journal of Coastal Research, Vol. 24, No. 5, 2008 1286 Aguilar et al.

Figure 2. Diet composition of bicolor damselfish at sites along the north- ern coast. ALG ϭ algae, COP ϭ copepods, CRU ϭ unidentified crusta- ceans, CYA ϭ cyanobacteria, EGG ϭ fish eggs, SCA ϭ fish scales. See text for statistical analysis of the data. Figure 3. Cluster analysis (UPGMA) for diet composition of all species. ϭ rs Spearman’s rank correlation coefficient. Acronyms for species are the first three letters of genus and species name. small benthophagous fish, e.g., squirrelfish and coney, and surgeonfish had lower values in the most impacted sites. The Ocean surgeonfish is a strict herbivore feeding on a broad probable cause is carbon from terrestrial sources arriving in range of algae and phanerogams. It is also highly mobile, the coastal zone from the harbor and river at Havana City. regularly patrolling the bottom. Again, such dispersal will ␦13 LEE (2000) found more positive C values for animals sam- probably mask any site-specific, stable isotope signatures. We pled with increasing distance out of Deep Bay, a harbor in also observed that surgeonfish from the most distant site southern China. The hypothesized shift was a gradual change from Havana City on the north coast (C30) were larger than from dependence on a mixture of carbon sources, e.g., anthro- those from other sites (BR, RIO). It has been reported that pogenic particulate organic matter, estuarine seston, and larger-bodied individuals are enriched in ␦15N(DARNAUDE, benthic algae, at the inner bay and increasing dependence on SALEN-PICARD, and HARMELIN-VIVIEN, 2003; RAU et al., benthic algae toward the estuary (Pearl River). 1981, cited by MINAGAWA and WADA, 1984); therefore, this ␦15 Differences in N ratios among sites for damselfish and difference in body size could also be masking differences at- wrasses suggest that nitrogen is also enriched at the city. tributable to human impacts. Several authors have found that sewage effluents have ele- In summary, our results indicate that nitrogen and carbon ␦15 vated N values (HEATON, 1986; MACKO and OSTROM, sources appear to vary along the coastal zone near Havana 1994) and that coastal ecosystems receiving sewage discharg- City, Cuba. The evidence supports the hypothesis that organ- ␦15 es have high N values (BOUILLON et al., 2002; FRY, 1999; ic matter coming from human activities on land enters the HANSSON et al., 1997; LAKE et al., 2001; MCCLELLAND and food web, passing from plankton and small invertebrates to VALIELA, 1998; MCCLELLAND,VALIELA, and MICHENER, benthophagous fish, as reported in the River Po, Italy (DAR- 1997; VOB and STRUCK, 1997). YAMAMURO,KAYANNE, and NAUDE,SALEN-PICARD, and HARMELIN-VIVIEN, 2003). It is YAMANO (2003) demonstrated that sea grasses impacted by also possible that some nitrogen in the form of nitrate or am- sewage effluent have elevated ␦15N ratios. A few studies have monium from fertilizers is being taken up by autotrophs ␦15 suggested that N can decrease in coastal waters if sewage (HEIKOOP et al., 2000a, 2000b). While nutrient additions may effluent is treated (GASTON and SUTHERS, 2004; RAU et al., enhance growth through an increase of food supply (e.g., GAS- 1981). In Havana City, there is evidence that nitrogen from TON and SUTHERS, 2004), the nutrients are indicative of sew- human pollution, probably untreated sewage effluent, is in- age effluent in the coastal zone, which can also conceal po- corporated in the food web of coral reefs. tentially deleterious or toxic substances. It will be important The results for bicolor damselfish corroborate early find- to elucidate the complete impact of the discharge of the har- ings (AGUILAR, 2005) that fish are larger in the vicinity of bor and its urban rivers on the adjacent coral reefs of the the harbor because sewage was enriching this environment. coastal zone. We have provided a first look at the food webs We demonstrate that diets were similar among sites; how- and the effects of human activities, but more research is ever, ␦15N ratios were different. needed to expand our results. We need to better understand No differences in ␦15N ratios were found among sites for the complex food webs of coral reefs (SOBEL and DAHLGREN, species at higher trophic levels, e.g., squirrelfish and coney. 2004; SOROKIN, 1995) and how ontogenetic and temporal These species are less territorial than damselfish and wrass- shifts in diet potentially affect variation of stable isotope com- es and move along the shore, and the squirrelfish are noc- positions. turnal, dispersing during the night to search for food (VALDE´ S-MUN˜ OZ and MOCHEK, 2001). Such behavior will re- ACKNOWLEDGMENTS duce the site-specific results, as we observed for the more The authors thank L. Sanchez and I. Rodriguez for their territorial species. assistance in the field, the crew of the Felipe Poey, and staff

Journal of Coastal Research, Vol. 24, No. 5, 2008 Human Impacts on Cuban Reef Fish 1287 of Centro de Investigaciones Marinas (CIM), Universidad de coastal wetlands. Estuarine, Coastal and Shelf Science, 58(4), 929– la Habana. Thanks to A.M. Suarez, A. Valdivia, and J. Es- 936. DARNAUDE, A.M.; SALEN-PICARD, C., and HARMELIN-VIVIEN,M., pinosa for assistance identifying seaweeds and mollusks; M. 2003. Stable isotope evidence of terrestrial organic matter incor- Ortiz, R. Lalana, and C. Varela for identifying crustaceans; poration into coastal marine food webs: impact of Rhone River and our colleagues from the Stable Isotopes in Nature Lab- inputs on five NW Mediterranean marine flatfish species. Geo- oratory, University of New Brunswick (UNB), Fredericton. physical Research Abstracts, 5, 02518. EMERY, A.R., 1973. 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