Marine Pollution Bulletin 46 (2003) 1273–1284 www.elsevier.com/locate/marpolbul Sublethal effects of contamination on the Mediterranean sponge Crambe crambe: metal accumulation and biological responses E. Cebrian a,*, R. Martı a, J.M. Uriz a, X. Turon b a Centre d’Estudis Avancßats de Blanes, CSIC, C/ Acces a la Cala St. Francesc, 14, 17300 Blanes, (Girona), Spain b Departament d’Invertebrats, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain Abstract The effect of low levels of pollution on the growth, reproduction output, morphology and survival of adult sponges and settlers of the sponge Crambe crambe were examined. We transplanted sponges from a control area to a contaminated site and measured the main environmental variables (chemical and physical) of both sites during the study period. Except some punctual differences in particulate organic matter, silicates, nitrates, and water motion, most environmental variables in the water were similar at both sites during the study months. Mainly copper, lead and OM concentrations in the sediment, and water motion were significantly higher at the polluted site and may be implicated in the biological effects observed: decrease in the percentage of specimens with embryos, increase in shape irregularity and decrease in growth rate. Individuals naturally occurring at the polluted site and those transplanted there for four months accumulated ten times more copper than either untouched or transplant controls. Although lead concen- tration in sediment did not differ between sites, native specimens from the contaminated site accumulated this metal more than untouched controls. Vanadium concentration also tended to increase in the sponges living at or transplanted to the contaminated site but this difference was not significant. C. crambe is a reliable indicator of metal contamination since it accumulates copper, lead and vanadium in high amounts. At the contaminated site, sponge growth, fecundity and survival were inhibited, whereas sponge irregularity ending in sponge fission was promoted. All these effects may compromise the structure and dynamics of the sponge populations in sheltered, metal-contaminated habitats. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Mediterranean; Sublethal contamination; Sponges; Crambe crambe; Heavy metals; Copper 1. Introduction than experimental, and contamination impacts are usu- ally assessed from observed mortality or changes in Many studies on the effects of contaminants on the community structure, which are measured by structure aquatic environment have been performed in the lab- descriptors such as diversity indices, species richness, oratory using target organisms easy to maintain in lab- species abundance or presence/absence of indicator spe- oratory conditions (e.g. Brown and Ahsnullah, 1971; cies (Carman et al., 1995; Carballo and Naranjo, 2002). Kobayashi, 1980; Rainbow et al., 1980; Rainbow and When changes in the structure of benthic communi- Wang, 2001). Laboratory studies involve the exposure of ties are detected, we are restricted to measuring the le- organisms to well-defined concentrations of one or a few thal effects of pollution. However, most contaminants contaminants in controlled environmental conditions. enter marine waters as low-level chronic toxicants whose Unfortunately, it is difficult to predict the responses to harmful effects are not always obvious and take time to toxicants in the field from these laboratory experiments, appear (Young et al., 1979). Small doses of pollutants since they do not take into account a variety of complex affect the physiological functions and behaviour of or- environmental interactions (Cairns and Pratt, 1989). On ganisms without killing them (e.g. Newton and the other hand, field studies tend to be descriptive rather McKenzie, 1995; Agell et al., 2001). Yet, these cryptic effects compromise not only individual fitness but also population success. Most of these studies have been * Corresponding author. carried out on soft bottom invertebrates (e.g. Ozoh, E-mail address: [email protected] (E. Cebrian). 1990; Warwick et al., 1990) or plankton species 0025-326X/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0025-326X(03)00190-5 1274 E. Cebrian et al. / Marine Pollution Bulletin 46 (2003) 1273–1284 (e.g. Brown and Ahsnullah, 1971; Riisgaard, 1979) and sisted of a vertical concrete wall from 0 to 5 m deep with scarce data are available on benthic filter feeders other similar facing and depth to control site. than mussels and clams (Bjerregaard and Depledge, From previous studies (Pinedo, 1998) organic matter, 1994; Abbe et al., 2000). Thus, the sublethal effects of most trace metals, TBT, and THC in the sediment at the contamination on many invertebrates, which dominate polluted site were no present at concentrations high most rocky assemblages, are unknown. enough to be considered pollutants. In contrast, copper Sponges are among the main constituents of sciaph- was at a mean concentration of 97 lggÀ1 at the polluted ilous, rocky communities in the Mediterranean benthos site (versus 6 lggÀ1 at the control site) and can be (Vacelet, 1979; Urizet al., 1992a,b), where they play a considered a contaminant, according to UNEP policies. paramount role in the energy transfer processes (Rei- Contamination in this harbour was expected to be due swig, 1971). According to the rare studies on sponge mainly to cleaning of small shipsÕ hulls, and urban responses to pollution (Alcolado and Herrera, 1987; sewage. Carballo et al., 1996; Perez, 2001), sponges are either resistant or susceptible to contaminants depending on 2.2. Environmental variables at the study sites the contaminant and the species considered. Here we examine the effect of low levels of pollution 2.2.1. Chemical parameters on the growth, reproduction output, morphology and During whole experiment period water was collected survival of adult sponges and settlers. These effects may weekly with a Niskins sampler from a depth of 3–4 m, at alter the species fitness and so its population dynamics, eight sampling points (four at the control site and four which will affect whole benthic assemblages. at the polluted site). We transplanted sponges from a control area to a For the analysis of particulate organic matter (or- contaminated site and measured the main environmen- ganic carbon and nitrogen), a 2 l sample of seawater was tal variables (chemical and physical) of both sites during screened through a 100 lm pore net to remove large the study period. Scattered individuals of Crambe plankton forms and detritus. Water was then passed crambe inhabited the contaminated site selected, which through a 0.22 lm diameter, GF/F glass fibre filter, allows us to state that the levels of contamination of this previously exposed to hydrochloric acid vapour for 48 h site were not lethal for the sponge. We subjected the in order to eliminate any inorganic material. Filters sponges transplanted to the same environmental condi- containing the organic matter were dried and analysed tions affecting the natural populations at both the con- with a C:H:N autoanalyser Eager 200. trol and contaminated areas for a four-month period. Filtered water was used to analyse nutrient salts, Since early life stages of benthic invertebrates are usually polycyclic aromatic hydrocarbons (PAHs) and heavy more susceptible to contamination than adult stages metals. Nutrient salts (nitrites, nitrates, phosphates and (Kobayashi, 1980), we also studied the survival rates of silicates) were analysed by colorimetric techniques settlers transplanted to both sites. (autoanalyser Technicon). Total PAHs were determined by gas chromatography coupled to mass spectrometry in the electron impact mode (GC-MS-EI) using a Fison 2. Material and methods GC8000 series chromatograph interfaced to a Fison MD 800 mass spectrometer (Sole et al., 2000). 2.1. Organism and study site 2.2.2. Sedimentation We studied the sponge C. crambe, a widespread sub- Gross sedimentation rates were assessed by placing littoral sponge in western Mediterranean (Vacelet, 1979; sediment traps, placed monthly during the experiment Urizet al., 1992a), which is well known from a biological (from February to June 1999) ðN ¼ 5Þ, at each study and ecological perspective (Becerro et al., 1994; Turon site. Traps remained in the water for three days. Dried et al., 1998; Urizet al., 1995). The encrusting growth sediment was weighed and then combusted at 300 °C for habit of this sponge allowed us to determine sponge 48 h and the mineral residue was weighed. The organic growth and shape by measuring increases in area and matter was calculated by subtracting the mineral com- the perimeter/area ratio, respectively. Furthermore, C. ponent of the sediment from the total dry weight. To crambe also lives at some polluted sites, what makes it search for possible differences in granulometry, a con- suitable for studies of sublethal contamination. stant amount of sediment was suspended in a constant The study was carried out at the Blanes sublittoral volume of water, and an aliquot (20 ll) of this suspen- (NE Iberian Peninsula, western Mediterranean) (NE of sion was placed in a haemocytometer and examined Spain, 41° 40.40 N, 2° 48.20 E). The control site was a under a light microscope. Microscope fields ðN ¼ 3Þ, vertical rocky wall, from 2 to 10 m deep, facing west. selected at random, were captured in a digital video The polluted site, 500 m from the control, was on the camera connected to a computer and the images were inner side of the Blanes harbour breakwater and con- used for quantification of particle size-classes with the E. Cebrian et al. / Marine Pollution Bulletin 46 (2003) 1273–1284 1275 NIH Image program (public domain). The sediment was 2.4.2. Sponge growth, shape and survival classed in very fine (VF) (diameter <12 lm), and fine (F) Sponge growth, shape and survival of transplanted (between 12 and 30 lm in diameter), which can enter the individuals were assessed from monthly photographs sponge through its orifices, and medium (M) (between from which perimeter and area were calculated with 30 and 100 lm in diameter) and coarse (C) (diameter > NIH image program for Macintosh.