Laboratory Aquaria Research Articles

Developing a sentinel mollusc species for toxicity assessment: metal exposure, dose and response – laboratory v. field exposures and resident organisms

Environmental contextMetal contamination in estuarine sediments can affect ecosystem health. Molluscs are commonly used as environmental indicators because they accumulate contaminants that cause adverse health effects. We investigated metal uptake and effects in the Sydney cockle, comparing exposure to contaminated lake sediments in situ and in laboratory aquariums. Although differences were observed between the different exposure types, all approaches were found to be valid for investigating metal health effects in this organism. AbstractRelationships between exposure, tissue dose and biological responses of the benthic marine bivalve Anadara trapezia to an estuarine sediment zinc, copper, lead, cadmium and selenium contamination gradient in Lake Macquarie, NSW, were evaluated using three approaches. Organisms were exposed to sediments in laboratory aquaria, caged in situ in the lake and lake resident organisms collected. Dose included total metal tissue burden and subcellular metal distribution to determine metabolically available metal. Response indices were total antioxidant capacity, lipid peroxidation, lysosomal stability and condition index. Bioaccumulation of total metals was higher in the laboratory and resident organisms than in those transplanted in the field but the contribution of individual metals to the total differed. Laboratory-exposed organisms had increased concentrations of cadmium and lead in their biologically active and detoxified metal fractions but not of the essential elements zinc and copper. Subcellular metal distribution patterns were the same in resident organisms but cadmium and lead burdens were higher in both fractions. Biomarker responses were similar in laboratory, transplanted and resident organisms. Total antioxidant capacity was significantly reduced and lipid peroxidation and lysosomal destabilisation significantly increased in all metal-exposed organisms compared with the reference A. trapezia. Condition index of laboratory-exposed organisms was significantly lower than in situ, resident and reference organisms. Clear metal exposure–dose–response relationships have been demonstrated for A. trapezia in laboratory and in situ experiments. Non-resident organisms, in both exposure scenarios, gave similar responses to resident metal-exposed organisms, showing all approaches are valid when investigating effects in this species.

Effect of PCB Bioavailability Changes in Sediments on Bioaccumulation in Fish.

In situ sediment amendment with sorbents such as activated carbon (AC) can effectively reduce the bioavailability of hydrophobic organic chemicals such as polychlorinated biphenyls (PCBs). However, there is limited experimental or modeling assessment of how bioavailability changes in sediments impact bioaccumulation in fish - the primary risk driver for exposure to humans and top predators in the aquatic ecosystem. In the present study we performed laboratory aquarium experiments and modeling to explore how PCB sorption in sediments impacted exposure pathways and bioaccumulation in fish. Results showed that freely dissolved PCBs in porewater and overlying water measured by passive sampling were reduced by more than 95% upon amendment with 4.5% fine granular AC. The amendment also reduced the PCB uptake in fish by 87% after 90 days of exposure. Measured freely dissolved concentrations were incorporated in equilibrium and kinetic models for predicting uptake by fish. Predicted uptake using the kinetic model was generally within a factor of 2 for total PCBs measured in fish. The kinetic model output was most sensitive to overlying water PCBs, lipid fraction, and dissolved oxygen concentration (regulating gill ventilation). Our results indicate that by incorporating changes in freely dissolved PCB concentrations in bioaccumulation models it is possible to predict effectiveness of sediment remediation in reducing PCB uptake in fish.

Concentration and retention of Toxoplasma gondii oocysts by marine snails demonstrate a novel mechanism for transmission of terrestrial zoonotic pathogens in coastal ecosystems.

The parasite Toxoplasma gondii is an environmentally persistent pathogen that can cause fatal disease in humans, terrestrial warm-blooded animals and aquatic mammals. Although an association between T. gondii exposure and prey specialization on marine snails was identified in threatened California sea otters, the ability of kelp-dwelling snails to transmit terrestrially derived pathogens has not been previously investigated. The objective of this study was to measure concentration and retention of T. gondii by marine snails in laboratory aquaria, and to test for natural T. gondii contamination in field-collected snails. Following exposure to T. gondii-containing seawater, oocysts were detected by microscopy in snail faeces and tissues for 10 and 3 days respectively. Nested polymerase chain reaction was also applied as a method for confirming putative T. gondii oocysts detected in snail faeces and tissues by microscopy. Toxoplasma gondii was not detected in field-collected snails. Results suggest that turban snails are competent transport hosts for T. gondii. By concentrating oocysts in faecal pellets, snails may facilitate entry of T. gondii into the nearshore marine food web. This novel mechanism also represents a general pathway by which marine transmission of terrestrially derived microorganisms can be mediated via pathogen concentration and retention by benthic invertebrates.

Chemosensory Perception of Predators by Larval Amphibians Depends on Water Quality.

The acquisition of sensory information by animals is central to species interactions. In aquatic environments, most taxa use chemical cues to assess predation risk and other key ecological factors. A number of laboratory studies suggest that anthropogenic pollutants can disrupt chemoreception, even when at low, non-toxic concentrations, but there are few tests of whether real-world variation in water quality affects chemoreception. Here we investigate whether chemosensory perception of predators by the gray treefrog, Hyla versicolor, depends on water quality. We evaluated the anti-predator response of anuran tadpoles housed in water collected from three sites that represent strong contrasts in the concentration and types of dissolved solids: de-chlorinated tap water, water from an impaired stream, and treated wastewater effluent. Behavioral assays were conducted in laboratory aquaria. Chemical cues associated with predation were generated by feeding tadpoles to dragonfly predators held in containers, and then transferring aliquots of water from dragonfly containers to experimental aquaria. Tadpoles housed in tap water responded to predator cues with an activity reduction of 49%. Tadpoles housed in stream water and wastewater effluent responded to predator cues by reducing activity by 29% and 24% respectively. The results of factorial ANOVA support the hypothesis that the response to predator cues depended on water type. These results show that alteration of the chemical environment can mediate chemical perception of predators in aquatic ecosystems. Because most aquatic species rely on chemoreception to gather information on the location of food and predators, any impairment of sensory perception likely has important ecological consequences.

Agonistic Behavior among Three Stocked Trout Species

AbstractThe popularity of reservoirs to support sport fisheries has led to the stocking of species that did not co‐evolve, creating novel reservoir fish communities. In Utah, the Bear Lake strain of Bonneville Cutthroat Trout Oncorhynchus clarkii utah and tiger trout (female Brown Trout Salmo trutta × male Brook Trout Salvelinus fontinalis) are being more frequently added to a traditional stocking regimen consisting primarily of Rainbow Trout O. mykiss. Interactions between these three predatory species are not well understood, and studies evaluating community interactions have raised concern for an overall decrease of trout condition. To evaluate the potential for negative interactions among these species, we tested aggression in laboratory aquaria using three‐species and pairwise combinations at three densities. Treatments were replicated before and after feeding. During the three‐species trials Rainbow Trout initiated 24.8 times more aggressive interactions than Cutthroat Trout and 10.2 times more aggressive interactions than tiger trout, and tiger trout exhibited slightly (1.9 times) more aggressive initiations than Cutthroat Trout. There was no significant difference in behavior before versus after feeding for any species, and no indication of increased aggression at higher densities. Although Rainbow Trout in aquaria may benefit from their bold, aggressive behavior, given observations of decreased relative survival in the field, these benefits may be outweighed in reservoirs, possibly through unnecessary energy expenditure and exposure to predators.Received October 1, 2014; accepted January 27, 2015

Вплив побутових забруднювачів на стан металотіонеїнів у тканинах двостулкового молюска Unio tumidus

Personal care products and pharmaceuticals are the most common novel water pollutants, and it is difficult to predict the effects. It is expected that they can modulate the activity of molecular detoxification systems. Since the production of the metal-binding proteins, metallothioneins (MTs) are activated by a wide range of stress factors, the aim of the study was to compare the functional characteristics of the MTs from digestive gland (DG) of male bivalve mollusc Unio tumidus from reference pond, polluted by sewage effluents pond and after the exposure to widespread water personal care pollutants ibuprofen (I, 250 ng / L), triclosan (T, 500 ng / L) or estrone (E1, 100 ng / L) for 14 days (overall term of staying in the laboratory aquaria – 21 days). The elevation of the content of zinc, copper and cadmium in bivalves’ tissues of DG, gonads and MTs as well as total level of MTs was noted in polluted pond compared to the reference one. Exposure factors and chronic pollution caused an increase of level of Zn-binding MT form on a background of reduced (I-, T-group) or increased (E1 group) total protein content of MTs and constant total level of zinc and copper in tissue. Under the effect of I, T and E1, marked decreasing in copper level and increasing (in 2.2–3 times) in zinc level were observed in the gonads. Thus, we should assume that the elevation of the content of zinc-MT in the bivalves DG can be considerded as the compound of the unspecific supporting strategy of the signa­ling function of these ions under the harmful efects. Keywords : bivalve mollusc, ibuprofen, triclosan, estron, metallothioneins, zinc.

Three new gnathiid species with larvae ectoparasitic on coastal sharks from southwestern Japan (Crustacea: Isopoda)

Gnathiid larvae were collected from the gill chambers of coastal sharks in southwestern Japan. Some were reared in a laboratory aquarium and successfully metamorphosed into adults. Morphological observations of the adult males identified three undescribed species, which are designated Gnathia albipalpebrata n. sp., G. parvirostrata n. sp., and G. dejimagi n. sp. on the basis of their larval morphologies and pigmentation patterns.

Do omnivorous shrimp influence mayfly nymph life history traits in a tropical island stream?

Interspecific interactions can play an important role in determining habitat selection and resource use between competing species. We examined interactions between an omnivorous shrimp and a grazing mayfly, two co-dominant taxa found in Puerto Rican headwater streams, to assess how predator presence may influence mayfly resource use and instantaneous growth in a tropical rainforest ecosystem. We conducted a series of behavioral and growth experiments to determine the effects of the freshwater shrimp, Xiphocaris elongata, on the growth rate and resource selection of mayfly nymphs in the family Leptophlebiidae. For resource choice assessments, we conducted a series of five day laboratory experiments where mayflies were given access to two resource substrate choices (cobble vs. leaves) in the presence or absence of shrimp. To assess for the effects of shrimp on mayfly fitness, we measured mayfly growth in laboratory aquaria after five days using four treatments (cobble, leaves, cobble + leaves, no resource) in the presence or absence of shrimp. In resource choice experiments, mayflies showed preference for cobble over leaf substrata (p < 0.05) regardless of the presence of shrimps, however, the preference for cobble was significantly greater when shrimp were present in the leaf habitat. In growth experiments, there were no statistical differences in mayfly growth in the presence or absence of shrimp (p = 0.07). However, we measured increased mayfly nymph growth in the absence of predators and when both cobble and leaves were available. Our results suggest that interspecific interactions between these taxa could potentially influence organic matter resource dynamics (e.g., leaf litter processing and export) in Puerto Rican streams.

An environmental oestrogen disrupts fish population dynamics through direct and transgenerational effects on survival and fecundity

Summary Increased need for water and projected declines in precipitation due to climate change could leave waterways increasingly dominated by wastewater effluent. Understanding how components of wastewater influence fish populations is necessary for effective conservation and management. Despite research demonstrating effects of oestrogens, such as 17α‐ethynylestradiol (EE2), on fish physiology and population failure, the generality of population responses is uncertain and the underlying mechanisms affecting population declines are unknown. EE2 is the steroid oestrogen in human contraceptive pills and has been measured up to 11 ng L−1 in the environment. We identify disrupted population dynamics due to direct and transgenerational effects on survival and fecundity. We conducted a year‐long study on three generations of fathead minnows Pimephales promelas Rafinesque in aquatic mesocosms and laboratory aquaria. We added environmentally relevant concentrations of EE2 daily using a static renewal, which approximates a pulsed exposure that fish experience in natural systems. EE2 (3·2 ng L−1) reduced F0 male survival to 17% (48% lower than controls) and juvenile production by 40% compared to controls. F1 fish continuously exposed to EE2 failed to reproduce, and reproduction of the F1 transferred to clean water was 70–99% less than controls. F2 larval survival, exposed only as germ cells in their parents, was reduced by 51–97% compared to controls. The indirect effect on F2 survival suggests the possibility of transgenerational effects of EE2. Synthesis and applications. Our results suggest that fish populations exposed to environmentally relevant 17α‐ethynylestradiol (EE2) concentrations may not recover from exposure. Management of short‐lived highly fecund fishes should be prioritized to protect fish from the embryo through gonadal differentiation. Reducing effluent will not be possible in many situations; hence, conservation of breeding and rearing habitat in unpolluted tributaries or reaches is needed. Additionally, resource managers could enhance habitat connectivity in rivers to facilitate immigration. Finally, investment in advanced wastewater processing technology should improve removal of bioactive chemicals such as EE2. Our results provide a baseline for regulatory agencies to consider when assessing the ecological effects of environmental oestrogens, and our approach to evaluating population‐level effects could be widely applied to other contaminants.

Regulation of laboratory populations of snails (Biomphalaria and Bulinus spp.) by river prawns, Macrobrachium spp. (Decapoda, Palaemonidae): Implications for control of schistosomiasis

Human schistosomiasis is a common parasitic disease endemic in many tropical and subtropical countries. One barrier to achieving long-term control of this disease has been re-infection of treated patients when they swim, bathe, or wade in surface fresh water infested with snails that harbor and release larval parasites. Because some snail species are obligate intermediate hosts of schistosome parasites, removing snails may reduce parasitic larvae in the water, reducing re-infection risk. Here, we evaluate the potential for snail control by predatory freshwater prawns, Macrobrachium rosenbergii and M. vollenhovenii, native to Asia and Africa, respectively. Both prawn species are high value, protein-rich human food commodities, suggesting their cultivation may be beneficial in resource-poor settings where few other disease control options exist. In a series of predation trials in laboratory aquaria, we found both species to be voracious predators of schistosome-susceptible snails, hatchlings, and eggs, even in the presence of alternative food, with sustained average consumption rates of 12% of their body weight per day. Prawns showed a weak preference for Bulinus truncatus over Biomphalaria glabrata snails. Consumption rates were highly predictable based on the ratio of prawn: snail body mass, suggesting satiation-limited predation. Even the smallest prawns tested (0.5–2g) caused snail recruitment failure, despite high snail fecundity. With the World Health Organization turning attention toward schistosomiasis elimination, native prawn cultivation may be a viable snail control strategy that offers a win–win for public health and economic development.

ADAPTIVE TEMPERATURE-DEPENDENT ACTIVITY PATTERNS IN MARINE GASTROPODS

ABSTRACT Activity patterns measured by vertical movement (VM) in laboratory aquaria were higher in the marine gastropod Monodonta turbinata than in M. turbiformis at 20–36°C. Higher temperatures induced increase VM values for both species, in particular for M. turbinata, which reached 0.95 VM at 31–36°C. We suggest that the differential temperature-dependent activity patterns found may be related to the different ecological niches of these two species.

Progress in Controlled In Situ Ocean Acidification Experiments

Ocean acidification is widely recognized as a significant climate‐related oceanic threat, not only independently but also in connection with other oceanic stressors, including warming and deoxygenation. Recent work shows that ocean acidification will negatively affect processes such as calcification of most species, including reef‐building corals, and could also cause diminished fish sensory ability and respiratory stress. However, almost all of these findings result from short‐term experiments on organisms in laboratory aquaria. But how can scientists perform long‐term in situ experiments that may confirm, or modify, conclusions drawn from laboratory experiments? With funding from the BNP Paribas Foundation, the xFOCE workshop brought together a group of 20 scientists and engineers to examine this.

Development and reproduction of Saprolegnia species in biofilms

Saprolegnia spp. can cause mortality and economic losses in freshwater fish and eggs. Biofilm formation is generally regarded as a virulence factor, and biofilms can be an important cause of infection recurrence. Evidence of persistent sources of Saprolegnia infections on fish and eggs in fish farms support the assumption that Saprolegnia spp. might be able to form biofilms. In this study, we aimed to test the ability of Saprolegnia to form biofilms where it can survive, reproduce and resist different chemicals used for its control. Naturally formed biofilms were obtained from laboratory aquaria. Saprolegnia growth within these biofilms was demonstrated with light microscopy and confirmed by isolation. Isolates were identified morphologically and molecularly on the basis of ITS-sequences. Two isolates were identified as Saprolegnia parasitica, a species known to be highly pathogenic for fish, while the other belonged to S. australis. Selected Saprolegnia strains obtained from natural biofilms were then used to establish simple methods for in vitro induction of Saprolegnia biofilm. The ability of Saprolegnia isolates to form biofilms with subsequent production of infective motile zoospores within the biofilm was documented by light and confocal laser scanning microscopy. We demonstrate for the first time that isolates of S. parasitica and S. australis can form biofilm communities together with multiple microorganisms, wherein they grow and reproduce. It is therefore likely that natural biofilms constitute incessant Saprolegnia reservoirs in nature and aquaculture.

Acoustics of fish shelters: Frequency response and gain properties

Many teleosts emit sounds from cavities beneath stones and other types of submerged objects, yet the acoustical properties of fish shelters are virtually unexplored. This study examines the gain properties of shelters commonly used by Mediterranean gobies as hiding places and/or nest sites in the field (flat stones, shells belonging to five bivalve species), or within aquarium tanks (tunnel-shaped plastic covers, concrete blocks, concrete cylinder pipe, halves of terracotta flower pots). All shelters were acoustically stimulated using a small underwater buzzer, placed inside or around the shelter to mimic a fish calling from the nest site, and different types of driving stimuli (white noise, pure tones, and artificial pulse trains). Results showed the presence of significant amplitude gain (3-18 dB) at frequencies in the range 100-150 Hz in all types of natural shelters but one (Mytilus), terracotta flower pots, and concrete blocks. Gain was higher for stones and artificial shelters than for shells. Gain peak amplitude increased with the weight of stones and shells. Conclusions were verified by performing analogous acoustical tests on flat stones in the stream. Results draw attention to the use of suitable shelters for proper recording of sounds produced by fishes kept within laboratory aquaria.

Phylogenetic Analysis of Microbial Communities in Different Regions of the Gastrointestinal Tract in Panaque nigrolineatus, a Wood-Eating Fish

The Neotropical detritivorous catfish Panaque nigrolineatus imbibes large quantities of wood as part of its diet. Due to the interest in cellulose, hemi-cellulose and lignin degradation pathways, this organism provides an interesting model system for the detection of novel microbial catabolism. In this study, we characterize the microbial community present in different regions of the alimentary tract of P. nigrolineatus fed a mixed diet of date palm and palm wood in laboratory aquaria. Analysis was performed on 16S rRNA gene clone libraries derived from anterior and posterior regions of the alimentary tract and the auxiliary lobe (AL), an uncharacterized organ that is vascularly attached to the midgut. Sequence analysis and phylogenetic reconstruction revealed distinct microbial communities in each tissue region. The foregut community shared many phylotypes in common with aquarium tank water and included Legionella and Hyphomicrobium spp. As the analysis moved further into the gastrointestinal tract, phylotypes with high levels of 16S rRNA sequence similarity to nitrogen-fixing Rhizobium and Agrobacterium spp. and Clostridium xylanovorans and Clostridium saccharolyticum, dominated midgut and AL communities. However, the hindgut was dominated almost exclusively by phylotypes with the highest 16S rRNA sequence similarity to the Cytophaga-Flavobacterium-Bacteroides phylum. Species richness was highest in the foregut (Chao1 = 26.72), decreased distally through the midgut (Chao1 = 25.38) and hindgut (Chao1 = 20.60), with the lowest diversity detected in the AL (Chao1 = 18.04), indicating the presence of a specialized microbial community. Using 16S rRNA gene phylogeny, we report that the P. nigrolineatus gastrointestinal tract possesses a microbial community closely related to microorganisms capable of cellulose degradation and nitrogen fixation. Further studies are underway to determine the role of this resident microbial community in Panaque nigrolineatus.

Multiple predator effects and native prey responses to two non-native Everglades cichlids

Abstract – Non-native predators may have negative impacts on native communities, and these effects may be dependent on interactions among multiple non-native predators. Sequential invasions by predators can enhance risk for native prey. Prey have a limited ability to respond to multiple threats since appropriate responses may conflict, and interactions with recent invaders may be novel. We examined predator–prey interactions among two non-native predators, a recent invader, the African jewelfish, and the longer-established Mayan cichlid, and a native Florida Everglades prey assemblage. Using field enclosures and laboratory aquaria, we compared predatory effects and antipredator responses across five prey taxa. Total predation rates were higher for Mayan cichlids, which also targeted more prey types. The cichlid invaders had similar microhabitat use, but varied in foraging styles, with African jewelfish being more active. The three prey species that experienced predation were those that overlapped in habitat use with predators. Flagfish were consumed by both predators, while riverine grass shrimp and bluefin killifish were eaten only by Mayan cichlids. In mixed predator treatments, we saw no evidence of emergent effects, since interactions between the two cichlid predators were low. Prey responded to predator threats by altering activity but not vertical distribution. Results suggest that prey vulnerability is affected by activity and habitat domain overlap with predators and may be lower to newly invading predators, perhaps due to novelty in the interaction.

Fine sediment on leaves: shredder removal of sediment does not enhance fungal colonisation

Inorganic fine sediments are easily carried into streams and rivers from disturbed land. These sediments can affect the stream biota, including detritivorous invertebrates (shredders) and impair ecosystem functions, such as leaf litter decomposition. We hypothesized that fine sediment (kaolin) deposited on leaves would reduce or suppress fungal development, reducing decomposition rates of leaves. Moreover, we predicted that shredders would act as ecosystem engineers by perturbing sediment deposition, reducing its impact on decomposition and fungi. We used a fully crossed experimental design of sediment addition (control, 400 mg L−1) and shredders (none, Gammarus, Potamophylax) in laboratory aquaria. Leaf mass loss, suspended solids, microbial respiration, fungal biomass and spore production were measured. Sediment addition had no significant effects on the leaf mass remaining nor on shredders’ consumption rates. However, sediment slightly reduced fungal assemblage richness and the sporulation rate of three fungal species. The presence of shredders substantially increased the resuspension of fine sediments (>300%), resulting in higher suspended loads. However, the action of shredders did not have a significant effect on fungal biomass nor on leaf mass loss. Even if shredders did not enhance fungal colonisation, they affected the settlement of fine sediment, serving as allogenic engineers. Our study suggests that concentrations of fine sediment of 400 mg L−1 with short exposure times (192 h) can have some effect on leaf decomposition.

A new sclerite-free genus and species of Clavulariidae (Coelenterata: Octocorallia)

This short communication describing only a single new taxon is necessary to facilitate further research publications by Neil Blackstone &amp; Austin Parrin (Northern Illinois University) and colleagues. Neil and Austin have found the new species to be an ideal experimental animal that is fast-growing and extremely easy to maintain in laboratory aquaria (Parrin et al. 2010). [NTM = Museum &amp; Art Gallery of the Northern Territory, PO Box 4646, Darwin, NT 0801, Australia].

The potential of combined Mg/Ca and δ 18O measurements within the shell of the bivalve Pecten maximus to estimate seawater δ 18O composition

The combined use of δ 18O and another independent palaeotemperature proxy from the same carbonate biomineral archive forms the basis of a much desired palaeosalinity proxy by circumventing the main source of uncertainty in interpreting δ 18O palaeorecords, i.e. variations in the isotopic composition of seawater. Contrary to the δ 18O proxy, transferring the Mg/Ca–temperature proxy to marine bivalves has proved problematic, since a strong seawater temperature control on shell calcite Mg/Ca has rarely been observed. In this study, a preliminary evaluation of the combined use of δ 18O calcite and Mg/Ca from Pecten maximus inner shell calcite to estimate δ 18O water is reported. New Mg/Ca data obtained by milling the inner shell regions from P. maximus specimens grown in laboratory aquaria under constant seawater temperatures between 10 and 20 °C exhibit a strong relationship between Mg/Ca and temperature [Mg/Ca = 2.56 (± 0.42) + 0.17 (± 0.03) ∗ T, r 2 = 0.77, p < 0.001, N = 54], while the relationship between Sr/Ca and temperature was not strong (r 2 = 0.30, p < 0.001, N = 54). Using specimens grown in a separate aquaria validation experiment, estimated Mg/Ca-derived seawater temperature was within 0.48 °C of measured seawater temperature, while estimated δ 18O water was within 0.05 to 0.15‰ of measured seawater δ 18O composition, depending on the δ 18O–temperature equation used, and with uncertainty estimates of 0.63‰ and 0.35‰. Such observations indicate the strongest potential to date for the development of valid temperature and δ 18O water/salinity proxies in bivalves from the combined application of Mg/Ca and δ 18O calcite in the inner shell regions of P. maximus. Further studies for a wide range of pectinid species, ages and different natural environmental settings are needed to validate the observations of this study.

Bioaccumulation of copper and zinc by the giant kelp Macrocystis pyrifera

This study examined the bioaccumulation of the heavy metals copper (Cu) and zinc (Zn) by the giant kelp, Macrocystis pyrifera, by exposing meristematic kelp tissue to elevated metal concentrations in seawater within laboratory aquaria. Specifically, we carried out two different experiments. The first examined metal uptake under a single, ecologically-relevant elevation of each metal (30 ppb Cu and 100 ppb Zn), and the second examined the relationships between varying levels of the metals (i.e., 15, 39, 60, 120, 240, and 480 ppb Cu, and 50, 100, 200, 300, 500, and 600 ppb Zn). Both experiments were designed to contrast the uptake of the metals in isolation (i.e., when only one metal concentration was elevated) and in combination (i.e., when both metals` concentrations were elevated). Following three days of exposure to the elevated metal concentrations, we collected and analyzed the M. pyrifera tissues using inductively coupled plasma atomic emissions spectroscopy. Our results indicated that M. pyrifera bioaccumulated Cu in all treatments where Cu concentrations in the seawater were elevated, regardless of whether Zn concentrations were also elevated. Similarly, M. pyrifera bioaccumulated Zn in treatments where seawater Zn concentrations were elevated, but this occurred only when we increased Zn alone, and not when we simultaneously increased Cu concentrations. This suggests that elevated Cu concentrations inhibit Zn uptake, but not vice versa. Following this, our second experiment examined the relationships among varying seawater Cu and Zn concentrations and their bioaccumulation by M. pyrifera. Here, our results indicated that, as their concentrations in the seawater rise, Cu and Zn uptake by M. pyrifera tissue also rises. As with the first experiment, the presence of elevated Zn in the water did not appear to affect Cu uptake at any concentration examined. However, although it was not statistically significant, we observed that the presence of elevated Cu in seawater appeared to trend toward inhibiting Zn uptake, especially at higher levels of the metals. This study suggests that M. pyrifera may be useful as a bio-indicator species for monitoring heavy metal pollution in coastal environments.