Assessing the risk of climate change to aquaculture: a case study from south-east Australia

A qualitative screening-level risk assessment was developed to evaluate relative levels of risk from climate change to aquaculture industries. The assessment was applied to 7 major industries in the temperate south-east region of Australia and involved a simple, transparent and repeatable methodology that was appropriate for a range of different aquaculture systems and taxa. Two key stages were involved: the development of comprehensive expertise-based literature reviews or ‘species profiles’ and a scoring assessment, with the latter providing a defined framework within which industries could be ranked (from high to low risk). In addition to informing the second stage of the risk assessment process, the species’ profiles also highlighted important climate change drivers and key information uncertainties and knowledge gaps. There was good resolution among the scoring assessments, with only 2 industries receiving the same risk score. The results indicated that oysters farmed from wild spat (Sydney rock oysters Saccostrea glomerata) were at most risk to climate change, with warm temperate hatchery-based finfish species (yellowtail kingfish Seriola lalandi) being the least at risk. This study provides critical guidance for scientists, resource managers and stakeholders for future research, both in addressing key knowledge gaps and focussing the development of more detailed risk analyses for high risk aquaculture industries in south-east Australia.

Mixed responses of tropical Pacific fisheries and aquaculture to climate change

Pacific Island countries have an extraordinary dependence on fisheries and aquaculture. Maintaining the benefits from the sector is a difficult task, now made more complex by climate change. Here we report how changes to the atmosphere–ocean are likely to affect the food webs, habitats and stocks underpinning fisheries and aquaculture across the region. We found winners and losers—tuna are expected to be more abundant in the east and freshwater aquaculture and fisheries are likely to be more productive. Conversely, coral reef fisheries could decrease by 20% by 2050 and coastal aquaculture may be less efficient. We demonstrate how the economic and social implications can be addressed within the sector—tuna and freshwater aquaculture can help support growing populations as coral reefs, coastal fisheries and mariculture decline.

Towards improved socio-economic assessments of ocean acidification’s impacts

Ocean acidification is increasingly recognized as a component of global change that could have a wide range of impacts on marine organisms, the ecosystems they live in, and the goods and services they provide humankind. Assessment of these potential socio-economic impacts requires integrated efforts between biologists, chemists, oceanographers, economists and social scientists. But because ocean acidification is a new research area, significant knowledge gaps are preventing economists from estimating its welfare impacts. For instance, economic data on the impact of ocean acidification on significant markets such as fisheries, aquaculture and tourism are very limited (if not non-existent), and non-market valuation studies on this topic are not yet available. Our paper summarizes the current understanding of future OA impacts and sets out what further information is required for economists to assess socio-economic impacts of ocean acidification. Our aim is to provide clear directions for multidisciplinary collaborative research.

Review of climate change impacts on marine fisheries in the UK and Ireland

1. Commercial fishing is an important socio-economic activity in coastal regions of the UK and Ireland. Ocean–atmospheric changes caused by greenhouse gas emissions are likely to affect future fish and shellfish production, and lead to increasing challenges in ensuring long-term sustainable fisheries management.
2. The paper reviews existing knowledge and understanding of the exposure of marine ecosystems to ocean-atmospheric changes, the consequences of these changes for marine fisheries in the UK and Ireland, and the adaptability of the UK and Irish fisheries sector.
3. Ocean warming is resulting in shifts in the distribution of exploited species and is affecting the productivity of fish stocks and underlying marine ecosystems. In addition, some studies suggest that ocean acidification may have large potential impacts on fisheries resources, in particular shell-forming invertebrates.
4. These changes may lead to loss of productivity, but also the opening of new fishing opportunities, depending on the interactions between climate impacts, fishing grounds and fleet types. They will also affect fishing regulations, the price of fish products and operating costs, which in turn will affect the economic performance of the UK and Irish fleets.
5. Key knowledge gaps exist in our understanding of the implications of climate and ocean chemistry changes for marine fisheries in the UK and Ireland, particularly on the social and economic responses of the fishing sectors to climate change. However, these gaps should not delay climate change mitigation and adaptation policy actions, particularly those measures that clearly have other ‘co-benefits’.

Impacts of climate change, including acidification, on marine ecosystems and fisheries

Marine ecosystems have always been affected by changes in climate at timescales from decades to millions of years. Since the industrial revolution in the nineteenth century the increase in greenhouse gases (GHG) has caused an accelerating rise in global temperature whose effects on marine biota can be detected at individual, population and ecosystem level. The rising level of CO₂ and consequent acidification of the oceans is having an impact on metabolism and calcification in many organisms, with damage to vulnerable ecosystems, such as coral reefs, already occurring. The pH of the oceans is already lower now than it has been for the past 600,000 years.

The potential impacts of ocean acidification: scaling from physiology to fisheries

Views expressed on the potential impact of ocean acidification range from wholesale degradation of marine ecosystems through to no discernable impact with minimal consequences. Constraining this range of predictions is necessary for the development of informed policy and management. The direct biological impacts of acidification occur at the molecular and cellular level; however, it is the expression of these effects at the population and ecosystem level that is of societal concern. Here, we consider the potential impact of ocean acidification on fisheries with particular emphasis on approaches to scaling from physiological responses to population- and ecosystem-level processes. In some instances, impacts of ocean acidification may lead to changes in the relative species composition at a given trophic level without affecting the overall productivity, whilst in other instances, ocean acidification may lead to a reduction in productivity at a given tropic level. Because of the scale at which ecological processes operate, modelling studies are required. Here, ocean acidification is situated within ongoing research into the ecological dynamics of perturbed systems, for which many models have already been developed. Whilst few existing models currently explicitly represent physiological processes sensitive to ocean acidification, some examples of how ocean acidification effects may be emulated within existing models are discussed. Answering the question of how acidification may impact fisheries requires the integration of knowledge across disciplines; this contribution aims to facilitate the inclusion of higher trophic level ecology into this ongoing debate and discussion.

Integrating ecophysiology and plankton dynamics into projected maximum fisheries catch potential under climate change in the Northeast Atlantic

Previous global analyses projected shifts in species distributions and maximum fisheries catch potential across ocean basins by 2050 under the Special Report on Emission Scenarios (SRES) A1B. However, these studies did not account for the effects of changes in ocean biogeochemistry and phytoplankton community structure that affect fish and invertebrate distribution and productivity. This paper uses a dynamic bioclimatic envelope model that incorporates these factors to project distribution and maximum catch potential of 120 species of exploited demersal fish and invertebrates in the Northeast Atlantic. Using projections from the US National Oceanic and Atmospheric Administration’s (NOAA) Geophysical Fluid Dynamics Laboratory Earth System Model (ESM2.1) under the SRES A1B, we project an average rate of distribution-centroid shift of 52 km decade−1 northwards and 5.1 m decade−1 deeper from 2005 to 2050. Ocean acidification and reduction in oxygen content reduce growth performance, increase the rate of range shift, and lower the estimated catch potentials (10-year average of 2050 relative to 2005) by 20–30% relative to simulations without considering these factors. Consideration of phytoplankton community structure may further reduce projected catch potentials by ∼10%. These results highlight the sensitivity of marine ecosystems to biogeochemical changes and the need to incorporate likely hypotheses of their biological and ecological effects in assessing climate change impacts.

The effects of climate change on aquaculture

Climate change is an additional pressure on top of the many (fishing pressure, loss of habitat, pollution, disturbance, introduced species) which fish stocks already experience. The impact of climate change must be evaluated in the context of other anthropogenic pressures, which often have much greater and more immediate effect. Factors that can shape climate are climate changes. These include such processes as variations in solar radiation, deviations in the Earth’s orbit, mountain-building and continental drift, and changes in greenhouse gas concentrations. Some parts of the climate system, such as the oceans and ice caps, respond slowly in reaction to climate changes because of their large mass. Therefore, the climate system can take centuries or longer to fully respond to new external changes. Many of the studies made assumptions about changes in baseline socioeconomic conditions, adaptation, and biophysical processes. Almost all of the studies we examined estimated that there will be increasing adverse impacts beyond an approximate 3 to 4°C increase in global mean temperature. The studies do not show a consistent relationship between impacts and global mean temperatures between 0 and 3 to 4°C. In coastal resources it is clear that impacts will be adverse with low levels of temperature change.

Inorganic carbon dynamics in the upwelling system off the Oregon coast and implications for commercial shellfish hatcheries

The increasing absorption of anthropogenic CO2 by the global ocean and concomitant decrease in pH will alter seawater carbonate chemistry in ways that may negatively impact calcifying organisms. In particular, the change in saturation state (Ω) of calcium carbonate minerals calcite and aragonite may be energetically unfavorable for shell formation while favoring shell dissolution. Eastern boundary upwelling systems may provide insights into how ecosystems respond to future conditions of ocean acidification when deep water with high dissolved inorganic carbon (DIC), low pH and low Ω is forced toward the surface. Mortality in commercial seed stock and reduced wild set of the oyster Crassostrea gigas in the northeast Pacific during 2005-2009 reinforced the need for understanding biological responses to acidified ocean water. In response, a long-term strategy to understand local carbonate chemistry dynamics, seasonal perturbations and the effects on development of calcifying bivalves was developed. At present, a time-series of pCO2 measurements was implemented in April 2010 in Netarts Bay, Oregon at Whiskey Creek Shellfish Hatchery (WCH). The intake sits at a depth of 0.5-8ft and water is pumped in at 100gpm. A line taken off the intake is run continuously through a thermosalinograph at approximately 1.5gpm into a showerhead style equilibrator in which the headspace is recirculated by aerating the water for enhanced gas exchange. CO2 in equilibrated air is analyzed by NDIR. Additionally two discrete samples of intake seawater were taken across tidal cycles weekly and analyzed for total CO2 (TCO2) according to the methods of Hales et al. (2004) and pCO2 for quality control. The pCO2 in the bay exhibits a diurnal cycle representative of daytime photosynthesis and nighttime respiration. However, the phasing and profiles of these cycles are dominated by tidal mixing and are affected by the introduction of high pCO2 water during upwelling events. Diurnal pCO2 during periods of low wind stress ranges from 100-700µatm. When strong equatorward winds induce upwelling, pCO2 levels exhibit a higher daily range of 300-2000µatm. The saturation state was calculated from the pCO2/TCO2 measurements of the discrete samples. The Ω for calcite and aragonite ranged from 2.07 and 1.15 to 8.58 and 4.69 respectively from April through August. Increased pCO2 and decreased pH have been shown to negatively impact larval development in C. gigas (Kurihara, 2007). Periods of elevated pCO2 in May and June 2010 correlated with commercial losses at WCH. The use of precise pCO2 measurements in real time has proven to be a valuable tool for use in aquaculture. As a commercial practice WCH has elected to only use source water that is below empirical pCO2 thresholds for spawning and culturing larvae. This has resulted in continued production and cost saving in an industry crucial to coast economies. A continuous TCO2/pCO2 monitoring system will be integrated into this long time-series to constrain inorganic carbon providing insight into carbonate chemistry dynamics in Netarts Bay, effects of ocean acidification on bivalve development and possible water treatment approaches for commercial aquaculture.

Adaptation to impacts of greenhouse gases on the ocean

Greenhouse gases are producing changes in ocean temperature and circulation, and these changes are already adversely affecting marine biota. Furthermore, carbon dioxide is absorbed by the oceans from the atmosphere, and this too is already adversely affecting some marine ecosystems. And, of course, sea-level rise affects both what is above and below the waterline. Clearly, the most effective approach to limit the negative impacts of climate change and acidification on the marine environment is to greatly diminish the rate of greenhouse gas emissions. However, there are other measures that can be taken to limit some of the negative effects of these stresses in the marine environment. Marine ecosystems are subject to multiple stresses, including overfishing, pollution, and loss of coastal wetlands that often serve as nurseries for the open ocean. The adaptive capacity of marine environments can be improved by limiting these other stresses. If current carbon dioxide emission trends continue, for some cases (e.g., coral reefs), it is possible that no amount of reduction in other stresses can offset the increase in stresses posed by warming and acidification. For other cases (e.g., blue-water top-predator fisheries), better fisheries management might yield improved population health despite continued warming and acidification. In addition to reducing stresses so as to improve the adaptive capacity of marine ecosystems, there is also the issue of adaptation in human communities that depend on this changing marine environment. For example, communities that depend on services provided by coral reefs may need to locate alternative foundations for their economies. The fishery industry will need to adapt to changes in fish abundance, timing and location. Most of the things we would like to do to increase the adaptive capacity of marine ecosystems (e.g., reduce fishing pressure, reduce coastal pollution, preserve coastal wetlands) are things that would make sense to do even in the absence of threats from climate change and ocean acidification. Therefore, these measures represent “no regrets” policy options for the marine environment. Nevertheless, even with adaptive policies in place, continued greenhouse gas emissions increasingly risk damaging marine ecosystems and the human communities that depend on them.