Behavioral responses of brown shrimp (Crangon crangon) to reduced seawater pH following simulated leakages from sub-sea geological storage of CO2.

Large-scale storage of CO2 within sub-sea geological formations is a viable option for reducing the volume of this greenhouse gas released directly to the atmosphere from anthropogenic activities. Risks to benthic marine life following possible leakage of gas through the seabed from this carbon capture and storage (CCS) initiative are not yet well established. This study examined behavior (activity patterns) in brown shrimp (Crangon crangon), exposed to a range of reduced seawater pH conditions (7.6, 7, or 6.5) simulating leakage scenarios of varying scales. Brown shrimp have an endogenous rhythmicity associated with their activity, which dictates they are most active during hours of darkness, presumably as protection against vision-dependent predators. This endogenous rhythm in activity continues to be expressed when shrimp are held under constant low-light conditions in the lab and provides an ecologically relevant endpoint to measure when examining the influence of reduced pH on the behavior of these animals. No marked differences in activity pattern were observed between control shrimp maintained at pH 8.1 and those at pH 7.6. However, changes in activity were evident at pH 7 and pH 6.5, where significant shifts in timing and intensity of activity occurred. There was an unexpected increase in activity within periods of expected light, probably signaling efforts by shrimp to migrate away from reduced seawater pH conditions. The loss of this important member of the benthic community due to migration may have important consequences for many of the resilient species that remain.

Functional immune response in Pecten maximus: combined effects of a pathogen-associated molecular pattern and PAH exposure.

Pathogen-associated molecular patterns (PAMPs) enable recognition of structures present in microorganisms such as lipopolysaccharides (LPS). LPS are an essential constituent of the outer membrane of Gram-negative bacteria, stimulating the innate immune system of invertebrates. Here, LPS from Escherichia coli (055:B5) were used to investigate the functional immune response of Pecten maximus after stimulation with a PAMP and to determine the combined effect of a phenanthrene exposure and LPS challenge. Organisms were exposed to 200 mug l(-1) phenanthrene and after 7 d were injected with either physiological saline (injection controls) or LPS solution, and returned to their respective exposure tanks. Haemolymph was sampled from the scallops 48 h post-injection and immune function was assessed using a combination of cellular biological responses. The LPS challenge significantly altered the immune response in P. maximus with increased cell counts and phagocytic activity. An immunosuppressive effect of phenanthrene was also observed in this study; however, exposure to phenanthrene did not significantly impair the organism's ability to respond to a PAMP challenge. The overall level of phagocytosis and cytotoxic capability following the LPS challenge was lower in phenanthrene exposed scallops and may have consequences for disease resistance in this commercially-exploited species.

Immunotoxicity and oxidative stress in the Arctic scallop Chlamys islandica: effects of acute oil exposure.

With increasing oil exploration in Arctic regions, the risk of an accidental oil spill into the environment is inevitably elevated. As a result, concerns have been raised over the potential impact of oil exposure on Arctic organisms. This study assessed the effects of an acute oil exposure (mimicking an accidental spill) on the immune function and oxidative stress status of the Arctic scallop Chlamys islandica. Scallops were exposed to the water accommodated fraction of crude oil over 21 d (maximum SigmaPAH 163 microg l(-1)) and immune endpoints and oxidative stress parameters were measured. Mortalities were recorded during the exposure and reductions in immunocompetence were observed, with significant impairment of phagocytosis and cell membrane stability. Scallops were also subjected to oxidative stress, with a significant reduction in glutathione levels and induction of lipid peroxidation. After the acute oil exposure had subsided, no recovery of immune function was observed indicating potential for prolonged sublethal effects.

Effects of oil and global environmental drivers on two keystone marine invertebrates.

Ocean warming (OW) and acidification (OA) are key features of global change and are predicted to have negative consequences for marine species and ecosystems. At a smaller scale increasing oil and gas activities at northern high latitudes could lead to greater risk of petroleum pollution, potentially exacerbating the effects of such global stressors. However, knowledge of combined effects is limited. This study employed a scenario-based, collapsed design to investigate the impact of one local acute stressor (North Sea crude oil) and two chronic global drivers (pH for OA and temperature for OW), alone or in combination on aspects of the biology of larval stages of two key invertebrates: the northern shrimp (Pandalus borealis) and the green sea urchin (Strongylocentrotus droebachiensis). Both local and global drivers had negative effects on survival, development and growth of the larval stages. These effects were species- and stage-dependent. No statistical interactions were observed between local and global drivers and the combined effects of the two drivers were approximately equal to the sum of their separate effects. This study highlights the importance of adjusting regulation associated with oil spill prevention to maximize the resilience of marine organisms to predicted future global conditions.

Behavioral responses of Arctica islandica (Bivalvia: Arcticidae) to simulated leakages of carbon dioxide from sub-sea geological storage.

Sub-sea geological storage of carbon dioxide (CO2) provides a viable option for the Carbon Capture and Storage (CCS) approach for reducing atmospheric emissions of this greenhouse gas. Although generally considered to offer a low risk of major leakage, it remains relevant to establish the possible consequences for marine organisms that live in or on sediments overlying these storage areas if such an event may occur. The present study has used a series of laboratory exposures and behavioral bioassays to establish the sensitivity of Arctica islandica to simulated leakages of CO2. This long-lived bivalve mollusc is widely distributed throughout the North Sea, an area where geological storage is currently taking place and where there are plans to expand this operation significantly. A recently published model has predicted a maximum drop of 1.9pH units in seawater at the point source of a substantial escape of CO2 from sub-sea geological storage in this region. Valve movements of A. islandica exposed to reduced pH seawater were recorded continuously using Hall effect proximity sensors. Valve movement regulation is important for optimising the flow of water over the gills, which supplies food and facilitates respiration. A stepwise reduction in seawater pH showed an initial increase in both the rate and extent of valve movements in the majority of individuals tested when pH fell to 6.2 units. Exposing A. islandica to pH 6.2 seawater continuously for seven days resulted in a clear increase in valve movements during the first 40h of exposure, followed by a gradual reduction in activity intensity over the subsequent five days, suggesting acclimation. The ability of both exposed and control bivalves to burrow successfully into sediment on completion of this exposure was very similar. A final exposure trial, testing whether increased valve movements initiated by reduced pH were related to foot extension during attempted burrowing, found no such association. In summary, significant changes in valve behavior did not occur until seawater pH fell to 6.2 units. The response took the form of an increase in valve activity rather than closure. The absence of foot extension coincident with increased valve movements indicates A. islandica were not attempting to burrow, leaving the possibility that valve movements are supporting a respiratory response to hypercapnia. In conclusion, A. islandica appears to be tolerant of reductions in seawater pH equivalent to those predicted for substantial losses of CO2 through leakage from sub-sea geological storage.

Bioconcentration, biotransformation, and elimination of polycyclic aromatic hydrocarbons in sheepshead minnows (Cyprinodon variegatus) exposed to contaminated seawater.

Sheepshead minnows (Cyprinodon variegatus) were continuously exposed to two concentrations of polycyclic aromatic hydrocarbons (PAHs) dissolved in seawater (sigma PAH = 7.57 and 72.31 microg/L) for 36 d, followed by 8 d of depuration. The PAHs studied were naphthalene (NPH or C0-NPH), phenanthrene (PHE or C0-PHE), pyrene (PYR), 2-methylnaphthalene (C1-NPH), 1,3-dimethylnaphthalene (C2-NPH), 2-isopropylnaphthalene (C3-NPH), 9-methylphenanthrene (C1-PHE), and 9-ethylphenanthrene (C2-PHE). Uptake rate constants (k1) for NPHs increased with increasing degree of alkylation and log value of the octanol/water partition coefficient (Kow), whereas k1 values for three- and four-ring PAHs were lower despite their high log Kow values. Elimination rate constants (k2) for the homologue series of NPHs and PHEs generally increased with decreasing degree of alkylation and log Kow values. However, the depuration time did not directly correlate with the molecular size for nonalkylated PAHs. Bioconcentration factors (BCFs) were estimated from the ratio of k1 to k2 and also directly from PAH concentrations in fish tissue and water samples, and the factors generated by the two methods were very similar. A significant positive correlation was determined between log BCFs and log Kow values for the series of C0- through C3-NPH at both low (r2 = 0.985, p = 0.0077) and high (r2 = 0.956, p = 0.022) exposures, although this correlation was not determined for all the PAHs studied. As a result of increased metabolism and/ or reduced bioavailability with increasing lipophilic character, the estimated BCFs for C0- through C2-PHE and PYR were generally lower than those for C0- through C3-NPH. The two exposure levels revealed minor variations in k1 and k2 values for parent PAHs and in the temporal pattern of PAH metabolite concentrations in bile. The present results indicate that the presence and nature of alkyl groups have a significant influence on the kinetics and metabolism of PAHs in fish.

Monitoring PAH contamination in the field (South west Iberian Peninsula): biomonitoring using fluorescence spectrophotometry and physiological assessments in the shore crab Carcinus maenas (L.) (Crustacea: Decapoda).

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants of the marine environment, arising predominantly from petrochemical contamination and pyrogenic sources. A biomarker of PAH exposure was employed in a field study (South West, Spain) in both captured (indigenous) and deployed (caged) shore crabs (Carcinus maenas) in the chronic PAH-exposed Bays of Algeciras and Gibraltar (from associated harbour and boating activity) compared to a relatively 'clean' site (Cadiz). Metabolite fluorescence was attributed to the following key priority PAH groups; naphthalenes (NAPs), pyrenes (PYRs) and benzo[a]pyrenes (BAPs). Temporal variability was assessed using deployed populations over an eight week period. Petrogenic and pyrogenic PAH contamination (as an indicator of the PAH type) was demonstrated using a ratio between FF(BAP + PYR)/FF(NAP). Physiological assessments from deployed crabs demonstrated both physiological and cellular alterations as shown by reduced heart rates (at rest) and increased cellular stress in crabs from the PAH contaminated sites.

Effects of the model PAH phenanthrene on immune function and oxidative stress in the haemolymph of the temperate scallop Pecten maximus.

Phenanthrene, a major component of crude oil, is one of the most abundant PAHs in aquatic ecosystems, and is readily bioavailable and toxic to a range of marine invertebrates. Within bivalves, the haemolymph acts as a transfer medium for these pollutants and their metabolic products, leaving haemocytes susceptible to deleterious effects. Using a suite of biological endpoints, this study determined the sublethal (7-d exposure to 50, 100 and 200microgL(-1)) effects of phenanthrene on several oxidative stress and immunological parameters in the haemolymph of the commercially-important scallop Pecten maximus. Phenanthrene exposure (200microgL(-1)) resulted in immune modulation with significant reductions in cell membrane stability (P<0.05) and phagocytosis (P<0.05), and a significant increase in the number of total haemocytes (P<0.05). Oxidative stress was also observed with a significant decrease in total glutathione (P<0.05) and significantly increased levels of lipid peroxidation in the haemolymph (P<0.05). Changes in the cellular and biochemical endpoints observed in this study illustrate their potential use in assessing the subtle effects of contaminant exposure. Whilst previous reports have suggested a link between free radical generation and immune suppression in vertebrates, this is the first instance where oxidative stress and immune function have been measured together in the haemolymph of a bivalve mollusc, demonstrating a possible link between PAH-induced oxidative stress and the subsequent inhibition in haemocyte immune function.

Immune function in the Arctic Scallop, Chlamys islandica, following dispersed oil exposure.

With the current expansion of offshore oil activities in Arctic regions, there is an urgent need to establish the potential effects of oil-related compounds on Arctic organisms. As susceptibility to growth, disease and survival is determined partly by the condition of an organism's immune system, measurement of endpoints linked to the latter system provide important early warning signals of the sub-lethal effects of exposure to contaminants. This study assessed the impact of dispersed oil exposure on immune endpoints in the Arctic Scallop Chlamys islandica, using a combination of cellular and humoral biological responses. Laboratory exposures of C. islandica to sub-lethal dispersed oil concentrations (0.06 and 0.25 mg l(-1)) were conducted over 15 days, followed by a 7-day recovery period in clean, filtered seawater. Cellular endpoints were significantly altered following dispersed oil exposure: haemocyte counts (P<0.01) and protein levels (P<0.01) were significantly elevated, whilst cell membrane stability (P<0.001) and phagocytosis (P<0.01) demonstrated a significant reduction. Whilst these results indicate alteration in the immune endpoints measured, this appears to be reversible upon removal of the contaminant stress. However, the impact of long-term continuous exposure and high-level acute exposure to oil is still unknown, and may have consequences for disease resistance and hence survival.