In 2001 Italy, France, and Principality of Monaco instituted a protected area for marine mammals in northwestern Mediterranean Sea, named the Pelagos Sanctuary. The agreement foresees the commitment by signing parties to manage human activities in the area, with a special mention to whale watching. Whale watching is a form of wildlife tourism which has considerably grown in the last decades. Understanding the profile of whale watchers and their satisfaction toward the activity, is the first step toward a sustainable and effective management of this touristic activity. In this work we provide the first analysis of the whale watching activity in the Pelagos Sanctuary, focusing on commercial whale watching tours departing from Italian harbors in Liguria. We provide a census of the activity and the results of close-ended questionnaires filled by whale watchers during trips in summer 2016 and 2017. The aim of the questionnaires was to understand the level of awareness of experienced and new whale watchers regarding the Pelagos Sanctuary and some conservation initiative going on in the area. Finally, we analyzed the satisfaction level, with the aim of evidencing weakness and strengths of the service offered. Our results evidence a growth in the activity in the last 15 years, with a wider differentiation of offers and impacting a larger area than previously found. Whale watchers in the area come from a variety of countries, demonstrating the importance of the Pelagos as a hot spot for this activity. A high level of satisfaction has been evidenced, with no difference among new and experienced whale watchers. At the same time, more effort is needed to increase awareness of Pelagos and its conservation initiative both at a national and international level. This study provides useful information for the start of an effective management of whale watching in this protected area.
Extractive activities in the ocean are expanding into the vast, poorly studied deep sea, with the consequence that environmental management decisions must be made for data-poor seafloor regions. Habitat classification can support marine spatial planning and inform decision-making processes in such areas. We present a regional, top–down, broad-scale, seafloor-habitat classification for the Clarion-Clipperton Fracture Zone (CCZ), an area targeted for future polymetallic nodule mining in abyssal waters in the equatorial Pacific Ocean. Our classification uses non-hierarchical, k-medoids clustering to combine environmental correlates of faunal distributions in the region. The classification uses topographic variables, particulate organic carbon flux to the seafloor, and is the first to use nodule abundance as a habitat variable. Twenty-four habitat classes are identified, with large expanses of abyssal plain and smaller classes with varying topography, food supply, and substrata. We then assess habitat representativity of the current network of protected areas (called Areas of Particular Environmental Interest) in the CCZ. Several habitat classes with high nodule abundance are common in mining exploration claims, but currently receive little to no protection in APEIs. There are several large unmanaged areas containing high nodule abundance on the periphery of the CCZ, as well as smaller unmanaged areas within the central CCZ, that could be considered for protection from mining to improve habitat representativity and safeguard regional biodiversity.
For the last six years, the Florida Reef Tract (FRT) has been experiencing an outbreak of the Stony Coral Tissue Loss Disease (SCTLD). First reported off the coast of Miami-Dade County in 2014, the SCTLD has since spread throughout the entire FRT with the exception of the Dry Tortugas. However, the causative agent for this outbreak is currently unknown. Here we show how a high-resolution bio-physical model coupled with a modified patch Susceptible-Infectious-Removed epidemic model can characterize the potential causative agent(s) of the disease and its vector. In the present study, the agent is assumed to be transported within composite material (e.g., coral mucus, dying tissues, and/or resuspended sediments) driven by currents and potentially persisting in the water column for extended periods of time. In this framework, our simulations suggest that the SCTLD is likely to be propagated within neutrally buoyant material driven by mean barotropic currents. Calibration of our model parameters with field data shows that corals are diseased within a mean transmission time of 6.45 days, with a basic reproduction number slightly above 1. Furthermore, the propagation speed of the disease through the FRT is shown to occur for a well-defined range of values of a disease threshold, defined as the fraction of diseased corals that causes an exponential growth of the disease in the reef site. Our results present a new connectivity-based approach to understand the spread of the SCTLD through the FRT. Such a method can provide a valuable complement to field observations and lab experiments to support the management of the epidemic as well as the identification of its causative agent.
Coral diseases contribute to the decline of reef communities, but factors that lead to disease are difficult to detect. In the present study, we develop a multi-species model of colony-scale risk for the class of coral diseases referred to as White Syndromes, investigating the role of current or past conditions, including both environmental stressors and biological drivers at the colony and community scales. Investigating 7 years of coral survey data at five sites in Guam we identify multiple environmental and ecological associations with White Syndrome, including a negative relationship between short-term heat stress and White Syndrome occurrence, and strong evidence of increasing size-dependent White Syndrome risk across coral species. Our findings result in a generalized model used to predict colony-scale White Syndrome risk for multiple species, highlighting the value of long-term monitoring efforts to detect drivers of coral disease.
In this study, the wave-induced distribution of 13 microplastic (MP) samples of different size, shape, and density was investigated in a wave flume with a sandy mobile beach bed profile. The particle parameter were chosen based on an occurrence probability investigated from the field. MP abundances were analyzed in cross-shore and vertical direction of the test area after over 40,000 regular waves. It was found, that MP particles accumulated in more shallow waters with increasing size and density. Particles with high density (ρs>1.25 g/cm3ρs>1.25 g/cm3) have been partly confined into deeper layers of the sloping beach during the formation of the bed profile. Particles with a density lower than that of water used in the experiments floated constantly in the surf zone or deposited on the beach caused by wave run-up. A correlation was found between the settling velocity of the MP particles and the flow velocity at the accumulation point and a power function equation developed. The obtained results were critically discussed with findings from the field and further laboratory studies.
Knowledge about fish behavior is crucial to be able to influence the capture process and catch species composition. The rapid expansion of the use of underwater cameras has facilitated unprecedented opportunities for studying the behavior of species interacting with fishing gears in their natural environment. This technological advance would greatly benefit from the parallel development of dedicated methodologies accounting for right-censored observations and variable observation periods between individuals related to instrumental, environmental and behavioral events. In this paper we proposed a methodological framework, based on a parametric Weibull mixture model, to describe the process of escapement attempts through time, test effects of covariates and estimate the probability that a fish will attempt to escape. We additionally proposed to better examine the escapement process at the individual level with regard to the temporal dynamics of escapement over time. Our approach was used to analyze gadoids swimming and escapement behaviors collected using a video set up in front of a selective device known to improve selectivity on gadoids in the extension of a bottom trawl. Comparison of the fit of models indicates that i) the instantaneous rate of escape attempts is constant over time and that the escapement process can be modelled using an exponential law; ii) the mean time before attempting to escape increases with the increasing number of attempts; iii) more than 80% of the gadoids attempted to escape through the selective device; and iv) the estimated probability of success was around 15%. Effects of covariates on the probability of success were investigated using binomial regression but none of them were significant. The data set collected is insufficient to make general statements, and further observations are required to properly investigate the effect of intrinsic and extrinsic factors governing gadoids behavior in trawls. This methodology could be used to better characterize the underlying behavioral process of fish in other parts of a bottom trawl or in relation to other fishing gears.
Marine reserves constitute effective tools for preserving fish stocks and associated human benefits. However, not all reserves perform equally, and predicting the response of marine communities to management actions in the long run is challenging. Our decadal-scale survey of recreational fishing yields at France’s 45-year old Cerbère-Banyuls marine reserve indicated significant protection benefits, with 40–50% higher fishing yields per unit effort in the partial-protection zone of the reserve (where fishing is permitted but at a lower level) than in surrounding non-reserve areas. Over the period 2005–2014, catch per unit effort (CPUE) declined both inside and outside the reserve, while weight per unit effort (WPUE) increased by 131% inside and decreased by 60% outside. Different CPUE and WPUE trajectories among fish families indicated changing catch assemblages, with yields increasing for the family most valued by fisheries, Sparidae (the ecological winners). However, reserve benefits were restricted to off-shore fishermen (the social winners), as on-shore yields were ~4 times lower and declining, even inside the reserve. Our study illustrates how surveys of recreational fishing yields can help evaluate the effectiveness of marine protected areas for key social and ecological protagonists. We show that, more than four decades after its establishment, fishing efficiencies at the historical Cerbère-Banyuls marine reserve are still changing, but benefits in terms of catch abundance, weight, and composition remain predominantly restricted to off-shore fishermen. Further regulations appear necessary to guarantee that conservation strategies equitably benefit societal groups.
Offshore wind power generation requires large areas of sea to accommodate its activities, with increasing claims for exclusive access. As a result, pressure is placed on other established maritime uses, such as commercial fisheries. The latter sector has often been taking a back seat in the thrust to move energy production offshore, thus leading to disagreements and conflicts among the different stakeholder groups. In recognition of the latter, there has been a growing international interest in exploring the combination of multiple maritime activities in the same area (multi-use; MU), including the re-instatement of fishing activities within, or in close proximity to, offshore wind farms (OWFs). We summarise local stakeholder perspectives from two sub-national case studies (East coast of Scotland and Germany's North Sea EEZ) to scope the feasibility of combining multiple uses of the sea, such as offshore wind farms and commercial fisheries. We combined a desk-based review with 15 semi-structured qualitative interviews with key knowledge holders from both industries, regulators, and academia to aggregate key results. Drivers, barriers and resulting effects (positive and negative) for potential multi-use of fisheries and OWFs are listed and ranked (57 factors in total). Factors are of economic, social, policy, legal, and technical nature. To date, in both case study areas, the offshore wind industry has shown little interest in multi-use solutions, unless clear added value is demonstrated and no risks to their operations are involved. In contrast, the commercial fishing sector is proactive towards multi-use projects and acts as a driving force for MU developments. We provide a range of management recommendations, based on stakeholder input, to support progress towards robust decision making in relation to multi-use solutions, including required policy and regulatory framework improvements, good practice guidance, empirical studies, capacity building of stakeholders and improvements of the consultation process. Our findings represent a comprehensive depiction of the current state and key stakeholder aspirations for multi-use solutions combining fisheries and OWFs. We believe that the pathways towards robust decision making in relation to multi-use solutions suggested here are transferable to other international locations.
Assessment of chemical exposures in the marine environment is frequently undertaken in sedentary organisms inhabiting coastal environments. However, predatory pelagic fish should be considered sentinel species, as they play an important role in the sustainability of the ecosystems due to their high position in trophic webs. In this study, carboxylesterase (CE) activities were analysed in four predatory tuna species of commercial interest along the western Mediterranean Sea: little tunny (Euthynnus alletteratus), Atlantic bonito (Sarda sarda), bullet tuna (Auxis rochei) and albacore tuna (Thunnus alalunga). CEs are potential biomarkers of chemical exposure, as they are an important family of enzymes involved in the metabolism of xenobiotic and endogenous compounds. CE measures were taken from the liver of these tuna species using five commercial substrates: 4-nitrophenyl acetate (4NPA), 4-nitrophenyl butyrate (4NPB), 1-naphthyl acetate (1NA), 1-naphthyl butyrate (1NB), and 2-naphthyl acetate (2NA). Butyrate substrates (1NB and 4NPB) yielded the highest hydrolysis rates, and were thus the best substrates for these measures. CE activities differed between species. The larger differences were attained with 1NB-CE, with higher activities seen in bullet tuna, followed by little tunny, Atlantic bonito and albacore tuna. Individual size was identified as one of the main factors modulating CE activities, while there was no evidence for a role for trophic level (measured as δ15N). Using little tunny as sentinel, no geographical differences but inter-annual variation in CE activity was observed. The kinetic parameters and in vitro exposure to the pesticide dichlorvos provided complementary information on the sensitivity of tuna CEs to this model pesticide. Our results propose that the little tunny could be considered a potential bioindicator species in the pelagic realm.
International scientific collaboration is vital for supporting global and regional measures to protect marine biodiversity in and beyond national jurisdiction. While scientists and governments seem to agree that scientific cooperation is also needed to reduce global imbalances to explore and exploit marine biodiversity, progress in defining and assessing developing countries’ needs has been slow. This paper aims to identify some of those needs by mapping the global distribution of scientific publications from the marine biodiversity field from 1990 until 2018. We present bibliographic data gathered from the Web of Science Core Collection using network analysis and article meta-data to examine international cooperation patterns both within and across regions. We introduce a novel measure, ‘collaboration capital’, which, based on metrics derived from a co-authorship network, attempts to gauge how valuable other actors in the network perceive the collaboration with an actor. Our data reveal that the US and Europe’s usual suspects allocate a significant proportion of collaboration capital from all regions. In turn, regional research networks in Asia, South America, and Africa are severely underdeveloped. These results suggest that measures to strengthen scientific collaboration within regions and between neighboring countries may contribute to strengthening regional research networks, for instance, by encouraging large emerging economies such as Brazil and China to become leaders in their regions in this respect. We conclude that capacity-building measures, such as discussed in current marine biodiversity negotiations, should foster regional scale cooperation efforts.
The Our Ocean conferences focus on voluntary commitments by different pledgers in support of actions towards a clean, healthy and productive ocean. We analysed the content and summarised the progress of implementation of the commitments related to sustainable fisheries at the Our Ocean conferences during 2014–2018. A total of 77 different entities provided commitments. Governments was the largest group (34) followed by NGOs (23). The majority (58%) of commitments were related to enforcement, transparency and cooperation. In particular, combating illegal, unreported and unregulated fisheries and support for the port state measures process were the focus of many of the commitments. To increase transparency and effectiveness of commitments, we suggest that more emphasis should be put on documenting and evaluating the impact of commitments. There is good progress in the implementation, and the commitments are largely reality and not empty words. We consider that the commitments have been successful in terms of generating attention and providing funding of projects that are supportive of sustainable fisheries. The diversity of pledgers is large, and an objective gap analysis on requirements for achieving sustainable fisheries regionally could provide pledgers with common ground and further increase the impact of the Our Ocean conferences.
Over the past several decades marine conservation policy has supported the implementation of protected areas in ocean and coastal environments to restrict some elements of human use for ecological benefits. The appropriate extent of protection and the allowable uses are often the subject of public debate about marine protected area policy. Local community dynamics around marine protected area designation and management have been the subject of much ocean and coastal management social science research. However, broader public opinions and attitudes about marine protected areas are not well understood and are critical for managers seeking to maintain their public trust obligations in environmental management. This paper provides a model for understanding the attitudes and beliefs that foster public support for or opposition to marine protections. We explored the relationships between awareness, attitudes and beliefs towards coastal and marine resource issues and uses, and demographics among a sample of Oregon, USA residents (n = 459), and tested their influence on support for expanding Oregon's recently established marine reserves. We found that Oregonians have relatively low familiarity with Oregon's marine reserve system, but that familiarity did not influence public support for Oregon's marine reserves. Instead public support was lower among coastal residents and those with positive attitudes towards commercial fisheries, and higher for those concerned with the ecological integrity of Oregon's ocean and supportive of some limits to human uses of the ocean. Our findings highlight the need for managers to engage both coastal communities and the general public to make a case for the value of marine protected areas in safeguarding the public trust.
Ebb-tidal deltas filter incoming wave energy and mitigate erosion of basins and coasts by temporarily providing sediment. In many systems, these coastal safety functions are under threat from human activities. Here we use Delft3D/SWAN to assess the effects of relative sea-level rise and changes in basin area on the long-term dynamics of ebb-tidal deltas. The results show that the time scales of the cyclic channel-shoal dynamics of ebb-tidal deltas are affected. An instantaneous decrease in basin area slows down the cyclic behavior during the initial adjustment period. The duration of the adjustment period increases with larger basin area reduction. After the adjustment, smaller basins have shorter time scales of cyclic channel-shoal dynamics. This is linked to a decrease in tidal prism and ebb-tidal delta volume. Moreover, we find that the effects of relative sea-level rise depend on the rate of rising water levels. For relatively low rates, the period of the cycles eventually shortens, whereas higher rates can cause longer periods. The volume of ebb-tidal deltas appears to be unaffected by relative sea-level rise; but because the average water depth increases, more energetic waves reach the basin. By showing how ebb-tidal deltas adjust to relative sea-level rise and basin area reduction and by unraveling the underlying mechanisms, this study contributes to our understanding of the long-term evolution of tidal inlets.
Subaqueous dredging is a management activity undertaken globally to improve navigation, remove contaminants, mitigate flood risk and/or generate aggregate. Water Injection Dredging (WID) is a hydrodynamic technique involving the turbation and downstream displacement of fine sediments using vessel-mounted water jets. Despite the technique being widely applied internationally, the environmental and ecological effects of WID are poorly understood. For the first time, this study used a Before-After-Control-Impact (BACI) experimental design to assess the effects of WID on water physicochemistry, and macroinvertebrate and fish communities within a 5.7 km-long reach of tidal river. WID targeted the central channel (thalweg) to avoid disturbance of the channel margins and banks. Mean but not peak turbidity levels were substantially elevated, and dissolved oxygen levels were reduced during periods of WID, although effects were relatively short-lived (≈3 h on average). Dredging resulted in significant reductions in benthic macroinvertebrate community abundance (particularly taxa that burrow into fine sediments), taxonomic richness and diversity. In contrast, minor changes were detected in marginal macroinvertebrate communities within and downstream of the dredged reach following WID. Reductions in fish taxonomic richness and diversity were recorded downstream of the dredged reach most likely due to behavioural avoidance of the sediment plume. No visibly stressed or dead fish were sampled during dredging. Results suggest that mobile organisms and marginal communities were largely unaffected by thalweg WID and that the technique represents a more ecologically sensitive alternative to traditional channel margin mechanical dredging techniques.
Microplastics (MPs) are ubiquitous in the aquatic environment due to plastic waste proliferation in diverse sectors. The recent years have witnessed exponential growth in the number of studies focusing on their occurrence, distribution and toxicity in several parts of India. The overarching aim of this article is to evaluate the sources, abundance, and characteristics of MPs reported in the sediments, water, and biota of the aquatic ecosystems in India. The review revealed that while the MPs from land-based sources such as littering, domestic sewage, and industrial runoff were carried by rivers and streams, MPs from other sources including marine litter and accidental spillages during shipping directly enter the aquatic environment. The unique hydrodynamic conditions during the southwest and northeast monsoons were found to influence the abundance and distribution of MPs in the Indian aquatic ecosystems. Although the seaward flushing and monsoonal flux were reported to increase the abundance of MPs, the reversal of the winds and currents during the NE monsoon was observed to oppose the drift of MPs towards the Goa coast. The reported higher concentrations of MPs in the beach sediments collected from the high tide line (1323 ± 1228 mg/m2) as compared to that of low tide line (178 ± 261 mg/m2) along the southeast coast of India also emphasize the tidal influence. While the shape and type of MPs can help in determining their sources, their size and colour might influence their ingestion in aquatic biota and also indicate the amount of degradation. The variability in the characteristics of MPs observed between different studies could also be a factor of difference in the sampling and analysis techniques adopted. Although the general practice of degutting before consumption could lower the risk of MPs transfer from fish, popular delicacies of dried fish and shrimps could be potential sources of human ingestion. Since the research was mostly confined to the southern coasts of India and some urban recreational beaches, the MP pollution on other coastal regions of India remains largely unexplored. Moreover, with very few studies reporting on the MP pollution in the freshwater ecosystems, the wide network of rivers and enclosed water bodies could also be the major focus of future research.
Life in the Pacific is characterised by interconnected, fast and slow socio-ecological change. These changes inevitably involve navigating questions of justice, as they shift who benefits from, owns, and governs resources, and whose claims and rights are recognized. Thus, greater understanding of perceptions of environmental justice within communities will be crucial to support fair adaptation. We contend that an environmental justice approach offers a theoretical foundation to help illuminate key concerns and trade-offs as communities navigate global change. Here, we apply an empirical environmental justice lens to the use and customary management of coastal resources in Papua New Guinea. Through two case studies, we examine perceptions of distributional, procedural and recognitional justice. We find similarities and differences. There were common concerns about the injustice of unequal fishing pressure and destructive methods, but in one case, concerns about people’s material needs overrode concerns about non-compliance and unequal costs. In the other case, deliberative decision-making served as a platform for not only negotiating and re-defining the distribution of costs and benefits, but also airing grievances, thereby strengthening recognition of different people’s values and concerns. In addition, we find that recognitional aspects of justice, such as respect, can confer or undermine the legitimacy of procedures for governing resources and thus making fair decisions about distribution. The heterogeneity of justice criteria in our cases emphasizes the need to elicit and understand plural justice perceptions in different contexts.
Comprehensive, spatially explicit data that include regulatory information are essential for evaluating the level of protection that marine protected areas (MPAs) and other marine managed areas (MMAs) provide to marine life, and to inform progress towards ocean protection targets. An analysis based on the ProtectedSeas database, which includes information on regulated activities, found that 85% of U.S. waters are in managed areas that restrict living resource extraction at some level above generally applicable regulations, with 52% managed at a low level of protection and 3% managed as highly protected no-take areas. States with the most state waters area in no-take MPAs are Hawaii (~25%), California (~9%), and Oregon (~3%). The majority of highly protected areas in U.S. waters exist in low-populated areas of the Pacific, such as the Papahānaumokuākea and Pacific Remote Islands Marine National Monuments. Under a quarter of U.S. waters are closed to bottom trawling, with the West Coast and Alaska each contributing one-third of trawl closures by area. Bottom trawling is prohibited in nearly 90% of West Coast waters. Focusing on waters off California showed that overlapping management and fishing gear restrictions can increase overall protection. In state waters, no-take MPAs account for roughly 9% of the area, while restricted take MPAs of different types cover 27% of the area. About 40% of California state waters are in some kind of MPA, while 13.4% of state waters have a high level of protection from fishing impacts. In federal waters off California, under one percent are in no-take areas while nearly all waters are subject to some kind of fishery restriction. Capturing regulatory information at the individual MPA and MMA level will improve assessments of current protection, inform planning of new protections, and provide ocean users a more accessible way to increase compliance through awareness.
The impact of bottom trawling noise was quantified on two surrounding marine acoustic habitats using fixed mooring acoustic recorders. Noise during trawling activity is shown to be considerably louder than ambient noise and a nearby underway research vessel. Estimated source levels were above cetacean damage thresholds. Measurements at a submarine canyon indicated potential noise focussing, inferring a role for such features to enhance down slope noise propagation at continental margin sites. Modelled sound propagates more efficiently when sourced from trawling gear dragging along the seabed relative to the vessel as a surface source. Results are contextualised with respect to marine mammal harm, to other anthropogenic ocean noise sources, topography and seasons. Noise energy emitted by bottom trawling activity is a source of pollution that requires further consideration, in line with other pervasive trawling pressures on marine species and seabed habitats, especially in areas of heightened ecological susceptibility.
Globally, aquaculture is expanding rapidly, with salmon becoming one of the most dynamic and fast-growing production systems in the world. Despite its commercial success, Chilean salmon production has navigated through severe economic and sanitary crises; followed by consecutive policy changes. Between 2007 and 2009, the rapid spread and the multiple effects of the Infectious Salmon Anemia virus (ISAV) marked a tipping point in the trajectory of the salmon aquaculture in southern Chile. This paper examines the discursive mechanisms through which the Chilean salmon aquaculture industry is currently being re-framed in the aftermath of the ISAV crisis, with a focus on searching for the emergence of ecosystem-related elements post crisis. The analysis shows that Chilean salmon aquaculture is being re-framed by the reproduction of three main discourses: biosecurity, sustainable protein and The Promise of Patagonia. The paper concludes that despite the staggering effects of the ISAV crisis on the national salmon production and on coastal communities more than a decade ago, new discourses are focused on the legitimization to growth, in the absence of integrated marine ecosystem-related elements, indicating a crucial gap toward environmental sustainability in salmon aquaculture.
Early evidence suggests that DNA methylation can mediate phenotypic responses of marine calcifying species to ocean acidification (OA). Few studies, however, have explicitly studied DNA methylation in calcifying tissues through time. Here, we examined the phenotypic and molecular responses in the extrapallial fluid and mantle (fluid and tissue at the calcification site) in adult eastern oyster (Crassostrea virginica) exposed to experimental OA over 80 days. Oysters were reared under three experimental pCO2 treatments (“control,” 580 μatm; “moderate OA,” 1,000 μatm; “high OA,” 2,800 μatm) and sampled at 6 time points (24 h−80 days). We found that high OA initially induced an increase in the pH of the extrapallial fluid (pHEPF) relative to the external seawater that peaked at day 9, but then diminished over time. Calcification rates were significantly lower in the high OA treatment compared to the other treatments. To explore how oysters regulate their extrapallial fluid, gene expression and DNA methylation were examined in the mantle-edge tissue of oysters from days 9 and 80 in the control and high OA treatments. Mantle tissue mounted a significant global molecular response (both in the transcriptome and methylome) to OA that shifted through time. Although we did not find individual genes that were significantly differentially expressed under OA, the pHEPF was significantly correlated with the eigengene expression of several co-expressed gene clusters. A small number of OA-induced differentially methylated loci were discovered, which corresponded with a weak association between OA-induced changes in genome-wide gene body DNA methylation and gene expression. Gene body methylation, however, was not significantly correlated with the eigengene expression of pHEPF-correlated gene clusters. These results suggest that OA induces a subtle response in a large number of genes in C. virginica, but also indicate that plasticity at the molecular level may be limited. Our study highlights the need to reassess our understanding of tissue-specific molecular responses in marine calcifiers, as well as the role of DNA methylation and gene expression in mediating physiological and biomineralization responses to OA.