In this study, the variations of the seawater carbonate system parameters and air-sea CO2 flux (FCO2) of Shen’ao Bay, a typical subtropical aquaculture bay located in China, were investigated in spring 2016 (March to May). Parameters related to the seawater carbonate system and FCO2 were measured monthly in 3 different aquaculture areas (fish, oyster and seaweed) and in a non-culture area near the bay mouth. The results showed that the seawater carbonate system was markedly influenced by the biological processes of the culture species. Total alkalinity was significantly lower in the oyster area compared with the fish and seaweed areas, mainly because of the calcification process of oysters. Dissolved inorganic carbon (DIC) and CO2 partial pressure ( pCO2) were highest in the fish area, followed by the oyster and non-culture areas, and lowest in the seaweed area. Oysters and fish can have indirect influences on DIC and pCO2by releasing nutrients, which facilitate the growth of seaweed and phytoplankton and therefore promote photosynthetic CO2 fixation. For these reasons, Shen’ao Bay acts as a potential CO2 sink in spring, with an average FCO2 ranging from -1.2 to -4.8 mmol m-2 d-1. CO2 fixation in the seaweed area was the largest contributor to CO2 flux, accounting for ca. 58% of the total CO2 sink capacity of the entire bay. These results suggest that the carbonate system and FCO2 of Shen’ao Bay were significantly affected by large-scale mariculture activities. A higher CO2 sink capacity could be acquired by extending the culture area of seaweed.
Elevated atmospheric carbon dioxide (CO2) is causing global ocean changes and drives changes in organism physiology, life-history traits, and population dynamics of natural marine resources. However, our knowledge of the mechanisms and consequences of ocean acidification (OA) – in combination with other climatic drivers (i.e., warming, deoxygenation) – on organisms and downstream effects on marine fisheries is limited. Here, we explored how the direct effects of multiple changes in ocean conditions on organism aerobic performance scales up to spatial impacts on fisheries catch of 210 commercially exploited marine invertebrates, known to be susceptible to OA. Under the highest CO2 trajectory, we show that global fisheries catch potential declines by as much as 12% by the year 2100 relative to present, of which 3.4% was attributed to OA. Moreover, OA effects are exacerbated in regions with greater changes in pH (e.g., West Arctic basin), but are reduced in tropical areas where the effects of ocean warming and deoxygenation are more pronounced (e.g., Indo-Pacific). Our results enhance our knowledge on multi-stressor effects on marine resources and how they can be scaled from physiology to population dynamics. Furthermore, it underscores variability of responses to OA and identifies vulnerable regions and species.
Climate change is at the forefront of today’s global challenges with its potential to turn into a runaway process. Fishing pressure acts in concert and exacerbates the impacts of climate change. The North Atlantic Ocean is no exemption of the increasing anthropogenic stress with Atlantic cod, Gadus Morhua, one of its most prominent fish species, displaying the ocean’s state. Most Atlantic cod stocks have experienced high rates of fishing and biomass declines, leading to renovation of fishing regulations and the implementation of rebuilding strategies. Today, the cod stocks differ considerably in trends and commercial status with 8 stocks considered collapsed and 57 % of today’s landings supplied by one single stock, the North East Arctic cod. What drives the collapse and what drives the recovery of a stock? Elucidating drivers of Atlantic cod productivity at low abundance is inevitable for sustainably managing the species in its changing habitat. This thesis attempts a comprehensive study on climate change impacts by addressing rising ocean temperature (paper I-III), temperature variability (paper II), acidification (paper III) and uncertainty (of the biology and as risk in management under the precautionary approach [paper IV]). Individual and synergistic impacts of climate change are discussed with a particular focus on nonlinear dynamics, including the potential for Allee effects (paper I-III). Allee effects describe the decrease in per capita growth rate at small population size, which can hinder population recovery by reinforcing degradation. Such a shift in the underlying biology can be irreversible and demands proactive and precautionary management measures. Application of precautionary measures to protect the environment and manage risks in situations of high uncertainty is a central tenet of the “precautionary approach”, a guiding principle in fisheries management. The poor state of various commercial fish stocks worldwide stands in contrast to the precautionary approach and suggests a subordinate role of science in fisheries management. In paper IV, Canada’s fisheries policy and advisory process is contrasted with the EU’s Common Fisheries Policy in regard to the precautionary approach and the role of science, in order to identify policy and institutional constraints that have hindered sustainable, precautionary management practices. Drawing from insights on climate change driven productivity changes (paper I-III) and the importance of a policy and institutional framework that acknowledges these (paper IV), this thesis ends with suggestions for scientifically informed, precautionary and sustainable fisheries management practices that can speed up recovery and allow for a vital fishery in the future.
- Environmental triclosan levels alter the reproductive output of R. philippinarum.
- Environmental triclosan levels reduce body mass in R. philippinarum.
- R. decussatus growth was resilient to environmental changes.
- Worst case scenario (TCS and climate change) will affect Manila clam production.
We built a simulation model based on Dynamic Energy Budget theory (DEB) to assess the growth and reproductive potential of the native European clam Ruditapes decussatus and the introduced Manila clam Ruditapes philippinarum under current temperature and pH conditions in a Portuguese estuary and under those forecasted for the end of the 21st c. The climate change scenario RCP8.5 predicts temperature increase of 3 °C and a pH decrease of 0.4 units. The model was run under additional conditions of exposure to the emerging contaminant triclosan (TCS) and in the absence of this compound. The parameters of the DEB model were calibrated with the results of laboratory experiments complemented with data from the literature available for these two important commercial shellfish resources. For each species and experimental condition (eight combinations), we used data from the experiments to produce estimates for the key parameters controlling food intake flux, assimilation flux, somatic maintenance flux and energy at the initial simulation time. The results showed that the growth and reproductive potential of both species would be compromised under future climate conditions, but the effect of TCS exposure had a higher impact on the energy budget than forecasted temperature and pH variations. The egg production of R. philippinarum was projected to suffer a more marked reduction with exposure to TCS, regardless of the climatic factor, while the native R. decussatus appeared more resilient to environmental causes of stress. The results suggest a likely decrease in the rates of expansion of the introduced R. philippinarum in European waters, and negative effects on fisheries and aquaculture production of exposure to emerging contaminants (e.g., TCS) and climate change.
Ocean acidification (OA) is increasing predictably in the global ocean as rising levels of atmospheric carbon dioxide lead to higher oceanic concentrations of inorganic carbon. The Gulf of Maine (GOM) is a seasonally varying region of confluence for many processes that further affect the carbonate system including freshwater influences and high productivity, particularly near the coast where local processes impart a strong influence. Two main regions within the GOM currently experience carbonate conditions that are suboptimal for many organisms—the nearshore and subsurface deep shelf. OA trends over the past 15 years have been masked in the GOM by recent warming and changes to the regional circulation that locally supply more Gulf Stream waters. The region is home to many commercially important shellfish that are vulnerable to OA conditions, as well as to the human populations whose dependence on shellfish species in the fishery has continued to increase over the past decade. Through a review of the sensitivity of the regional marine ecosystem inhabitants, we identified a critical threshold of 1.5 for the aragonite saturation state (Ωa). A combination of regional high-resolution simulations that include coastal processes were used to project OA conditions for the GOM into 2050. By 2050, the Ωa declines everywhere in the GOM with most pronounced impacts near the coast, in subsurface waters, and associated with freshening. Under the RCP 8.5 projected climate scenario, the entire GOM will experience conditions below the critical Ωa threshold of 1.5 for most of the year by 2050. Despite these declines, the projected warming in the GOM imparts a partial compensatory effect to Ωa by elevating saturation states considerably above what would result from acidification alone and preserving some important fisheries locations, including much of Georges Bank, above the critical threshold.
The impacts of anthropogenic climate change are already discernible throughout the ocean, from the equator to the poles, and from the surface to abyssal depths. Further climate change impacts are inevitable; however, their damage to marine organisms and ecosystems, and the services they provide, can be greatly reduced if greenhouse gas emissions are rapidly reduced. This review covers six main climate-related drivers (warming, acidification, deoxygenation, sea level rise and storm events, sea ice loss, stratification, and nutrient supply) and their impacts on 13 marine ecosystems, broadly defined. Seven of these are near-shore (coral reefs, kelp ecosystems, seagrass meadows, rocky and sandy intertidal, saltmarshes, estuaries, and mangroves) and six are in shelf seas and the open ocean (shelf sea benthos, upper ocean plankton, fish and fisheries, cold water corals, ice-influenced ecosystems, and the deep seafloor). Three cross-cutting issues are emphasized: that climate change impacts are not single factors, but interact together and with other human pressures in a multistressor context; that there are fast and slow climate processes in the ocean, with overall temporal uncertainties relating to future societal behavior; and that there can be high spatial heterogeneity in marine ecosystem impacts and vulnerabilities.
Quantifying the spatial and temporal footprint of multiple environmental stressors on marine fisheries is imperative to understanding the effects of changing ocean conditions on living marine resources. Pacific Cod (Gadus macrocephalus), an important marine species in the Gulf of Alaska ecosystem, has declined dramatically in recent years, likely in response to extreme environmental variability in the Gulf of Alaska related to anomalous marine heatwave conditions in 2014–2016 and 2019. Here, we evaluate the effects of two potential environmental stressors, temperature variability and ocean acidification, on the growth of juvenile Pacific Cod in the Gulf of Alaska using a novel machine-learning framework called “stress-scapes,” which applies the fundamentals of dynamic seascape classification to both environmental and biological data. Stress-scapes apply a probabilistic self-organizing map (prSOM) machine learning algorithm and Hierarchical Agglomerative Clustering (HAC) analysis to produce distinct, dynamic patches of the ocean that share similar environmental variability and Pacific Cod growth characteristics, preserve the topology of the underlying data, and are robust to non-linear biological patterns. We then compare stress-scape output classes to Pacific Cod growth rates in the field using otolith increment analysis. Our work successfully resolved five dynamic stress-scapes in the coastal Gulf of Alaska ecosystem from 2010 to 2016. We utilized stress-scapes to compare conditions during the 2014–2016 marine heatwave to cooler years immediately prior and found that the stress-scapes captured distinct heatwave and non-heatwave classes, which highlighted high juvenile Pacific Cod growth and anomalous environmental conditions during heatwave conditions. Dominant stress-scapes underestimated juvenile Pacific Cod growth across all study years when compared to otolith-derived field growth rates, highlighting the potential for selective mortality or biological parameters currently missing in the stress-scape model as well as differences in potential growth predicted by the stress-scape and realized growth observed in the field. A sensitivity analysis of the stress-scape classification result shows that including growth rate data in stress-scape classification adjusts the training of the prSOM, enabling it to distinguish between regions where elevated sea surface temperature is negatively impacting growth rates. Classifications that rely solely on environmental data fail to distinguish these regions. With their incorporation of environmental and non-linear physiological variables across a wide spatio-temporal scale, stress-scapes show promise as an emerging methodology for evaluating the response of marine fisheries to changing ocean conditions in any dynamic marine system where sufficient data are available.
Promoting the Sustainable Development Goals (SDGs) must contend with the often siloed nature of governance institutions, making the identification of cooperative institutional networks that promote SDG targets a priority. We develop and apply a method that combines SDG interaction analysis, which helps determine prerequisites for SDG attainment, with the transition management framework, which helps align policy goals with institutional designs. Using Aruba as a case study, we show that prioritizing increased economic benefits from sustainable marine development, including those of tourism, provides the greatest amount of direct co-benefits to other SDGs. When considering indirect co-benefits, reducing marine pollution emerged as a key supporting target to achieve SDGs. The results also show that, as in many other small island states, sustainable ocean development in Aruba depends on international partnerships to address global issues—including climate change mitigation—over which it has little control. Using SDG relationships as a guide for institutional cooperation, we find that the institutions with the most potential to coordinate action for sustainable ocean development are those that address economic, social and international policy, rather than institutions specifically focused on environmental policy. Our results provide key methodologies and insights for sustainable marine development that require coordinated actions across institutions.
Climate driven range shifts are driving the redistribution of marine species and threatening the functioning and stability of marine ecosystems. For species that are the structural basis of marine ecosystems, such effects can be magnified into drastic loss of ecosystem functioning and resilience. Rhodoliths are unattached calcareous red algae that provide key complex three-dimensional habitats for highly diverse biological communities. These globally distributed biodiversity hotspots are increasingly threatened by ongoing environmental changes, mainly ocean acidification and warming, with wide negative impacts anticipated in the years to come. These are superimposed upon major local stressors caused by direct destructive impacts, such as bottom trawling, which act synergistically in the deterioration of the rhodolith ecosystem health and function. Anticipating the potential impacts of future environmental changes on the rhodolith biome may inform timely mitigation strategies integrating local effects of bottom trawling over vulnerable areas at global scales. This study aimed to identify future climate refugia, as regions where persistence is predicted under contrasting climate scenarios, and to analyze their trawling threat levels. This was approached by developing species distribution models with ecologically relevant environmental predictors, combined with the development of a global bottom trawling intensity index to identify heavily fished regions overlaying rhodoliths. Our results revealed the importance of light, thermal stress and pH driving the global distribution of rhodoliths. Future projections showed poleward expansions and contractions of suitable habitats at lower latitudes, structuring cryptic depth refugia, particularly evident under the more severe warming scenario RCP 8.5. Our results suggest that if management and conservation measures are not taken, bottom trawling may directly threaten the persistence of key rhodolith refugia. Since rhodoliths have slow growth rates, high sensitivity and ecological importance, understanding how their current and future distribution might be susceptible to bottom trawling pressure, may contribute to determine the fate of both the species and their associated communities.
The rising concentrations of carbon dioxide and other greenhouse gases have caused observed physical, chemical and biological changes in the oceans, with further changes projected over coming decades. The impact of climate change on the oceans are profound, with rapid warming in ocean hotspots combined with extreme events such as marine heatwaves changing the distribution and abundance of a wide range of marine species. Further, ocean acidification, sea level rise, and deoxygenation may have important consequences for the marine ecosystems and the ecosystem services derived from the ocean. These observed and future ocean changes are irreversible on the timescale of many centuries. As a result, management of marine resources, for both extractive (for example, fishing) and non-extractive (for example, marine tourism) will need to account for the effects of climate change. For example, changes in abundance of marine species will impact harvesting levels and ecosystem structure, while changes in species’ distribution will challenge place-based management and agreements between nations. Adaptation to some of these changes will be possible; however, without substantial reduction in greenhouse gas emissions the oceans will change and not provide the same support for human activities as currently enjoyed. The changing nature of the ocean, and the impact it may have on ecosystems and communities, represents a huge challenge to future community interactions at local, national and international scales. It also raises the possibility of active intervention in the climate system to minimize the impacts of climate change which will introduce a complex set of issues to be considered before implementing any intervention.
- Food web models and scenarios were used to forecast effects of climate change.
- Modeled bays were vulnerable to the effects of climate change.
- In two of three study bays the ability to support bivalve aquaculture disappeared.
Coastal ecosystems provide important ecosystem services for millions of people. Climate change is modifying coastal ecosystem food web structure and function and threatens these essential ecosystem services. We used a combination of two new and one existing ecosystem food web models and altered scenarios that are possible with climate change to quantify the impacts of climate change on ecosystem stability in three coastal bays in Maine, United States. We also examined the impact of climate change on bivalve fisheries and aquaculture. Our modeled scenarios explicitly considered the predicted effects of future climatic change and human intervention and included: 1) the influence of increased terrestrial dissolved organic carbon loading on phytoplankton biomass; 2) benthic community change driven by synergisms between climate change, historical overfishing, and increased species invasion; and 3) altered trophic level energy transfer driven by ocean warming and acidification. The effects of climate change strongly negatively influenced ecosystem energy flow and ecosystem stability and negatively affected modeled bivalve carrying capacity in each of our models along the Maine coast of the eastern United States. Our results suggest that the interconnected nature of ecosystem food webs make them extremely vulnerable to synergistic effects of climate change. To better inform fisheries and aquaculture management, the effects of climate change must be explicitly incorporated.
This paper presents the first comprehensive review and synthesis of studies that forecast economic impacts of ocean acidification. The changes in seawater chemistry resulting from increased carbon dioxide emissions, collectively known as ocean acidification, will have detrimental impacts to marine ecosystem services. Those services include wild capture fisheries, aquaculture, recreation, shoreline protection, and others. The current literature valuing expected impacts to those services is rather thin and tends to focus on mollusk harvesting and aquaculture. Despite the paucity of studies, we divide all relevant estimates into seven additively separable economic sectors to provide the first aggregate estimate of economic damages from ocean acidification at the end of this century. We perform non-parametric bootstrap to characterize the distribution of estimates within each sector and the aggregation across sectors. We also perform meta-regressions to explore whether estimates provided by these studies are generally consistent with expectations based on ocean chemistry and economic theory. We find a global average of per capita annual losses in the year 2100 between $47 and $58 and we find strong evidence that estimates are consistent with expectations given future emissions and socio-economic scenarios that underlie the original studies.
Ocean warming and species exploitation have already caused large-scale reorganization of biological communities across the world. Accurate projections of future biodiversity change require a comprehensive understanding of how entire communities respond to global change. We combined a time-dynamic integrated food web modelling approach (Ecosim) with a community-level mesocosm experiment to determine the independent and combined effects of ocean warming and acidification, and fisheries exploitation, on a temperate coastal ecosystem. The mesocosm enabled important physiological and behavioural responses to climate stressors to be projected for trophic levels ranging from primary producers to top predators, including sharks. We show that under current-day rates of exploitation, warming and ocean acidification will benefit most species in higher trophic levels (e.g. mammals, birds, demersal finfish) in their current climate ranges, with the exception of small pelagic fish, but these benefits will be reduced or lost when these physical stressors co-occur. We show that increases in exploitation will, in most instances, suppress any positive effects of human-driven climate change, causing individual species biomass to decrease at high-trophic levels. Species diversity at the trailing edges of species distributions is likely to decline in the face of ocean warming, acidification and exploitation. We showcase how multi-level mesocosm food web experiments can be used to directly inform dynamic food web models, enabling the ecological processes that drive the responses of marine ecosystems to scenarios of global change to be captured in model projections and their individual and combined effects to be teased apart. Our approach for blending theoretical and empirical results from mesocosm experiments with computational models will provide resource managers and conservation biologists with improved tools for forecasting biodiversity change and altered ecosystem processes due to climate change.
Recent studies call for transdisciplinary research to address the consequences of anthropogenic change on human-environment systems, like the impact of ocean acidification (OA) on oyster aquaculture. I surveyed oyster farmers in coastal British Columbia, Canada, about their first-hand experiences of ocean change. Farmers reported that oyster mortality (die-off events) is one of many challenges they face and is likely related to several interacting environmental factors, including water temperature and oyster food, particularly in 2016. I examined temperature, productivity, and carbonate chemistry conditions from 2013 to 2017 using available observations and the Salish Sea model, to understand poor oyster growing conditions in 2016. While temperatures were relatively high and chlorophyll relatively low during the 2016 spring bloom, carbonate conditions were relatively good, suggesting OA was not a key driver of difficult oyster growing conditions. This work provides a novel example of using local knowledge to better inform scientific investigation and adaptation to environmental change.
• Modelling suggests the effect of climate change on snapper populations is uncertain.
• Impacts range from a 29% reduction to a 44% increase in fishery yield.
• These impacts are most likely mediated via impacts on recruitment.
Anthropogenic CO2 emissions are warming and acidifying Earth’s oceans, which is likely to lead to a variety of effects on marine ecosystems. Fish populations will be vulnerable to this change, and there is now substantial evidence of the direct and indirect effects of climate change on fish. There is also a growing effort to conceptualise the effects of climate change on fish within population models. In the present study knowledge about the response of New Zealand snapper to warming and acidification was incorporated within a stock assessment model. Specifically, a previous tank experiment on larval snapper suggested both positive and negative effects, and otolith increment analysis on wild snapper indicated that growth may initially increase, followed by a potential decline as temperatures continue to warm. As a result of this uncertainty, sensitivity analysis was performed by varying average virgin recruitment (R0) by ±30%, adult growth by ±6%, but adjusting mean size at recruitment by +48% as we had better evidence for this increase. Overall adjustments to R0 had the biggest impact on the future yield (at a management target of 40% of an unfished population) of the Hauraki Gulf snapper fishery. The most negative scenario suggested a 29% decrease in fishery yield, while the most optimistic scenario suggested a 44% increase. While largely uncertain, these results provide some scope for predicting future impacts on the snapper fishery. Given that snapper is a species where the response to climate change has been specifically investigated, increasing uncertainty in a future where climate change and other stressors interact in complex and unpredictable ways is likely to be an important consideration for the management of nearly all fish populations.
The effects of climate change on the ocean environment – especially ocean warming, acidification, and sea level rise – will impact fish stocks and fishers in important ways. Likely impacts include changes in fish stocks’ productivity and distribution, human migration to and away from coastal areas, stresses on coastal fisheries infrastructure, and challenges to prevailing maritime boundaries. In this paper, we explore these and other related phenomena, in order to assess whether and how the impacts of climate change on fisheries will contribute to the risk of fisheries conflict. We argue that climate change will entail an increase in the conditions that may precipitate fisheries conflict, and thereby create new challenges for existing fisheries management institutions. Several potential changes in fisheries management policy are recommended to avert the growing risk of fisheries-related conflicts.