Review of climate change impacts on marine fish and shellfish around the UK and Ireland

1. Recent and projected future changes in the temperature and chemistry of marine waters around the UK and Ireland are having, and will in the future have, effects on the phenology, productivity and distribution of marine fish and shellfish. However, the overall consequences are still hard to predict because behaviour, genetic adaptation, habitat dependency and the impacts of fishing on species, result in complex species’ responses that may be only partially explained by simple climate envelope predictions.
2. There is a broad body of evidence that climatic fluctuations are playing an important role in changing fish distributions and abundances, which is discernible against the background of trends in abundance due to fishing. During warm periods, southern species have tended to become more prominent and northern species less abundant. However, the changes in distribution are often more complicated than might be expected from a simple climate envelope approach, partly due to ocean circulation patterns which create invasion routes for southern water species into the North Sea from the south and from the north via the continental shelf west of Britain and Ireland.
3. The eventual population-scale impacts of ocean acidification on fish and shellfish are currently very difficult to predict. However, the scant evidence suggests that indirect food web effects arising from the enhanced sensitivity of calcifying planktonic organisms may be important, and the direct effect on fish sensory systems leading to subtle influences on behaviour with possible population-level implications are possible.
4. In British waters, the lesser sandeel (Ammodytes marinus) is identified as being at particular risk from climate change. Owing to its strict association with coarse sandy sediments it is unable to adapt its distribution to compensate for warming sea temperatures. Sandeels are a key link in the food web, linking primary and zooplankton production to top predators.

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.

Integrated management of nutrients from the watershed to coast in the subtropical region

This paper is a brief review on nutrient variation (changes in element concentrations and ratios) and the associated aquatic ecosystem responses in the subtropical region. Human activities have significantly modified both the flux and the ratio of nutrients delivered to aquatic ecosystems. Climate perturbations influence the hydrological regime and enhance nutrient mineralization and transport from land to receiving waters. Changes in land use and damming have resulted in changes in the balance among nitrogen, phosphorus and silicon elements, thus increasing the risk of algal bloom. Nutrient variation and its ecological effects in the subtropical region could be more significant than in other areas because of rapid development and high population. Aquatic ecosystems respond to nutrient variation in complex and dynamic ways resulting in eutrophication, hypoxia/anoxia, acidification, and changes in phytoplankton and microbial communities. This review suggests that harmful algal bloom, jellyfish bloom, and serious pathogens are often associated with nutrient variations. The current challenges to scientific research and management include the facts that (1) the link between nutrient dynamics and ecosystem responses is poorly understood; (2) monitoring data to support modeling and management are scarce; (3) aquatic ecosystems are site-specific and/or situation-specific and are highly dynamic, giving greater complexity in research and management; and (4) the lack of regional coordination in traditional management causes transboundary gaps. To address these current challenges, an integrated management framework was proposed for effective nutrient management. Institutional arrangements should be developed to coordinate across multiple government agencies and other stakeholders from watershed to coast. The framework should integrate an interdisciplinary scientific approach and adaptive principles regarding nutrient management.

Biogeochemical response of tropical coastal systems to present and past environmental change

Global climate and environmental change affect the biogeochemistry and ecology of aquatic systems mostly due to a combination of natural and anthropogenic factors. The latter became more and more important during the past few thousand years and particularly during the ‘Anthropocene’. However, although they are considered important in this respect as yet much less is known from tropical than from high latitude coasts. Tropical coasts receive the majority of river inputs into the ocean, they harbor a variety of diverse ecosystems and a majority of the population lives there and economically depends on their natural resources. This review delineates the biogeochemical response of coastal systems to environmental change and the interplay of natural and anthropogenic control factors nowadays and in the recent geological past with an emphasis on tropical regions. Weathering rates are higher in low than in high latitude regions with a maximum in the SE Asia/Western Pacific region. On a global scale the net effect of increasing erosion due to deforestation and sediment retention behind dams is a reduced sediment input into the oceans during the Anthropocene. However, an increase was observed in the SE Asia/Western Pacific region. Nitrogen and phosphorus inputs into the ocean have trebled between the 1970s and 1990s due to human activities. As a consequence of increased nutrient inputs and a change in the nutrient mix excessive algal blooms and changes in the phytoplankton community composition towards non-biomineralizing species have been observed in many regions. This has implications for foodwebs and biogeochemical cycles of coastal seas including the release of greenhouse gases. Examples from tropical coasts with high population density and extensive agriculture, however, display deviations from temperate and subtropical regions in this respect. According to instrumental records and observations the present-day biogeochemical and ecological response to environmental change appears to be on the order of decades. A sediment record from the Brazilian continental margin spanning the past 85,000 years, however, depicts that the ecosystem response to changes in climate and hydrology can be on the order of 1,000-2,000 years. The coastal ocean carbon cycle is very sensitive to Anthropocene changes in land-derived carbon and nutrient fluxes and increasing atmospheric carbon dioxide. As opposing trends in high latitude regions tropical coastal seas display increasing organic matter inputs and reduced calcification rates which have important implications for calcifying organisms and the carbon source or sink function of the coastal ocean. Particularly coral reefs which are thriving in warm tropical waters are suffering from ocean acidification. Nevertheless, they are not affected uniformly and the sensitivity to ocean acidification may vary largely among coral reefs. Therefore, the prediction of future scenarios requires an improved understanding of present and past responses to environmental change with particular emphasis put on tropical regions.

Carbonate production by calcareous red algae and global change

The most important groups of modern red calcareous algae are the Mg-calcite secreting Corallinales and Sporolithales, and the aragonitic Peyssonneliales and Nemaliales. They are common on the world’s shelves and are vulnerable to the global warming and the lowering of pH of sea water, caused by the ongoing increase in anthropogenic CO2. Among them, coralline algae are ecosystem engineers and major producers of carbonate sediment, of particular importance in temperate and cold seas. Corallines respond to marine acidification and rising temperature showing decreased net calcification, decreased growth and reproduction, as well as reduced abundance and diversity, leading to death and ecological shift to dominant non-calcifying algae. Despite their key ecological and sedimentological role, and because of their vulnerability to marine warming and acidification, our knowledge of the distribution of coralline-dominated habitats and the quantification of their carbonate production is not adequate to allow proper environmental management and confident modelling of a global carbon budget. Locating the algal carbonate factories around the world, then describing them, e.g., evaluating their extent and their production, are a priority for future research.

Oceanic acidification: A comprehensive overview

This book critically examines the available literature on oceanic acidification, including a historical review of pH and atmospheric CO₂ levels over the millennia; natural and anthropogenic sources of CO₂ to the atmosphere and sea surface; chemical, physical, and biological mode of action; biological effects of acidification to marine plants and animals under laboratory conditions; field observations on seawater chemistry and effects of declining pH; and various technical and political mitigation strategies. Written by Dr. Ronald Eisler, a noted authority on chemical risk assessment, the book summarizes real and projected effects of oceanic acidification.

Ocean Acidification – How will ongoing ocean acidification affect marine life?

Implications of observed inconsistencies in carbonate chemistry measurements for ocean acidification studies

The growing field of ocean acidification research is concerned with the investigation of organisms’ responses to increasing pCO₂ values. One important approach in this context is culture work using seawater with adjusted CO₂ levels. As aqueous pCO₂ is difficult to measure directly in small scale experiments, it is generally calculated from two other measured parameters of the carbonate system (often A_T, C_T or pH). Unfortunately, the overall uncertainties of measured and subsequently calculated values are often unknown. Especially under high pCO₂, this can become a severe problem with respect to the interpretation of physiological and ecological data. In the few datasets from ocean acidification research where all three of these parameters were measured, pCO₂ values calculated from A_T and C_T are typically about 30 % lower (i.e. ~300 μatm at a target pCO₂ of 1000 μatm) than those calculated from A_T and pH or C_T and pH. This study presents and discusses these discrepancies as well as likely consequences for the ocean acidification community. Until this problem is solved, one has to consider that calculated parameters of the carbonate system (e.g. pCO₂, calcite saturation state) may not be comparable between studies, and that this may have important implications for the interpretation of CO₂ perturbation experiments.

Review of Ocean Acidification, edited by J.-P. Gattuso and L. Hansson

This new book edited by Jean-Pierre Gattuso and Lina Hansson is a timely, interdisciplinary look at the phenomenon of ocean acidification, which refers broadly to changes in seawater chemistry caused by rising atmospheric carbon dioxide (CO2) and the resulting effects on marine life and biogeochemistry. Atmospheric CO2 has increased almost 40% above pre-industrial levels, and the ocean removes roughly a quarter of current human CO2 emissions, driven mostly by the burning of fossil fuels. The topic of ocean acidification was brought to wide attention of the research community only recently with the publication of an influential Royal Society report in 2005. Since then, the scientific literature on acidification has virtually exploded, and targeted national and international research programs are blossoming. While many useful review articles, planning documents, and special volumes exist on the subject, a good example being the Oceanography special issue on “The Future of Ocean Biogeochemistry in a High CO2 World” (volume 22[4], December 2009, http://www.tos.org/oceanography/archive/22-4.html), until the publication of this book, the community lacked a single, authoritative source spanning the full disciplinary breadth of the topic.

A decade of climate change experiments on marine organisms: procedures, patterns and problems

The first decade of the new millennium saw a flurry of experiments to establish a mechanistic understanding of how climate change might transform the global biota, including marine organisms. However, the biophysical properties of the marine environment impose challenges to experiments which can weaken their inference space. To facilitate strengthening the experimental evidence for possible ecological consequences of climate change, we reviewed the physical, biological and procedural scope of 110 marine climate change experiments published between 2000 and 2009. We found that 65% of these experiments only tested a single climate change factor (warming or acidification), 54% targeted temperate organisms, 58% were restricted to a single species and 73% to benthic invertebrates. In addition, 49% of the reviewed experiments had issues with the experimental design, principally related to inappropriate replication of the main test-factors (temperature or pH), and only 11% included field assessments of processes or associated patterns. Guiding future research by this inventory of current strengths and weaknesses will expand the overall inference space of marine climate change experiments. Specifically, increased effort is required in five areas: (i) the combined effects of concurrent climate and non-climate stressors; (ii) responses of a broader range of species, particularly from tropical and polar regions as well as primary producers, pelagic invertebrates, and fish; (iii) species interactions and responses of species assemblages, (iv) reducing pseudo-replication in controlled experiments; and (v) increasing realism in experiments through broad-scale observations and field experiments. Attention in these areas will improve the generality and accuracy of our understanding of climate change as a driver of biological change in marine ecosystems.