The Ocean as a Solution to Climate Change: Five Opportunities for Action

The ocean is a dominant feature of our planet, covering 70 percent of its surface and driving its climate and biosphere. The ocean sustains life on earth and yet is in peril from climate change. However, while much of recent attention is focused on the problems that the ocean faces, the ocean is also a source of potential solutions and innovation. This report explores how the ocean, its coastal regions and economic activities can provide opportunities in the fight against climate change

Low coral cover in a high-CO2 world

Coral reefs generally exist within a relatively narrow band of temperatures, light, and seawater aragonite saturation states. The growth of coral reefs is minimal or nonexistent outside this envelope. Climate change, through its effect on ocean temperature, has already had an impact on the world's coral reefs, with almost 30% of corals having disappeared since the beginning of the 1980s. Abnormally warm temperatures cause corals to bleach ( lose their brown dinoflagellate symbionts) and, if elevated for long enough, to die. Increasing atmospheric CO2 is also potentially affecting coral reefs by lowering the aragonite saturation state of seawater, making carbonate ions less available for calcification. The synergistic interaction of elevated temperature and CO2 is likely to produce major changes to coral reefs over the next few decades and centuries. Known tolerances of corals to projected changes to sea temperatures indicate that corals are unlikely to remain abundant on reefs and could be rare by the middle of this century if the atmospheric CO2 concentration doubles or triples. The combination of changes to sea temperature and carbonate ion availability could trigger large- scale changes in the biodiversity and function of coral reefs. The ramifications of these changes for the hundred of millions of coral reef - dependent people and industries living in a high- CO2 world have yet to be properly defined. The weight of evidence suggests, however, that projected changes will cause major shifts in the prospects for industries and societies that depend on having healthy coral reefs along their coastlines

Cell death and degeneration in the symbiotic dinoflagellates of the coral Stylophora pistillata during bleaching

Rising sea temperatures are increasing the incidences of mass coral bleaching (the dissociation of the coral–algal symbiosis) and coral mortality. In this study, the effects of bleaching (induced by elevated light and temperature) on the condition of symbiotic dinoflagellates (Symbiodinium sp.) within the tissue of the hard coral Stylophora pistillata (Esper) were assessed using a suite of techniques. Bleaching of S. pistillata was accompanied by declines in the maximum potential quantum yield of photosynthesis (Fv/Fm, measured using pulse amplitude modulated [PAM] fluorometry), an increase in the number of Sytox-green-stained algae (indicating compromised algal membrane integrity and cell death), an increase in 2’,7’-dichlorodihydrofluroscein diacetate (H2DCFDA)- stained algae (indicating increased oxidative stress), as well as ultrastructural changes (vacuolisation, losses of chlorophyll, and an increase in accumulation bodies). Algae expelled from S. pistillata exhibited a complete disorganisation of cellular contents; expelled cells contained only amorphous material. In situ samples taken during a natural mass coral bleaching event on the Great Barrier Reef in February 2002 also revealed a high number of Sytox-labelled algae cells in symbio. Dinoflagellate\ud degeneration during bleaching seems to be similar to the changes resulting from senescence-phase cell death in cultured algae. These data support a role for oxidative stress in the mechanism of coral bleaching and highlight the importance of algal degeneration during the bleaching of a reef coral

Coral reef sustainability through adaptation: glimmer of hope or persistent mirage?

Coral reefs are highly threatened by human activities at both global (ocean warming and acidification) and local scales (overfishing, pollution, and physical destruction) especially given that current rates of environmental change exceed those seen for tens of millions of years. Recent authors, however, have suggested that coral reefs might increase their tolerance to these rapid environmental changes through acclimatisation, genetic adaptation, and migration. While there is evidence of all three responses acting within coral populations, there is little basis for the conclusion that reef-building corals and coral reefs will become more sustainable and resilient over time under current high rates of change. Most studies that make this claim have correctly identified components and mechanisms but have otherwise incorrectly extended this evidence which is otherwise necessary but not sufficient to support the conclusion that coral reefs will survive due to their ability to acclimatise, adapt and/or migrate to the current rapid environmental changes

Coral Reef Ecosystems under Climate Change and Ocean Acidification

Coral reefs are found in a wide range of environments, where they provide food and habitat to a large range of organisms as well as providing many other ecological goods and services. Warm-water coral reefs, for example, occupy shallow sunlit, warm, and alkaline waters in order to grow and calcify at the high rates necessary to build and maintain their calcium carbonate structures. At deeper locations (40–150 m), “mesophotic” (low light) coral reefs accumulate calcium carbonate at much lower rates (if at all in some cases) yet remain important as habitat for a wide range of organisms, including those important for fisheries. Finally, even deeper, down to 2,000 m or more, the so-called “cold-water” coral reefs are found in the dark depths. Despite their importance, coral reefs are facing significant challenges from human activities including pollution, over-harvesting, physical destruction, and climate change. In the latter case, even lower greenhouse gas emission scenarios (such as Representative Concentration Pathway RCP 4.5) are likely drive the elimination of most warm-water coral reefs by 2040–2050. Cold-water corals are also threatened by warming temperatures and ocean acidification although evidence of the direct effect of climate change is less clear. Evidence that coral reefs can adapt at rates which are sufficient for them to keep up with rapid ocean warming and acidification is minimal, especially given that corals are long-lived and hence have slow rates of evolution. Conclusions that coral reefs will migrate to higher latitudes as they warm are equally unfounded, with the observations of tropical species appearing at high latitudes “necessary but not sufficient” evidence that entire coral reef ecosystems are shifting. On the contrary, coral reefs are likely to degrade rapidly over the next 20 years, presenting fundamental challenges for the 500 million people who derive food, income, coastal protection, and a range of other services from coral reefs. Unless rapid advances to the goals of the Paris Climate Change Agreement occur over the next decade, hundreds of millions of people are likely to face increasing amounts of poverty and social disruption, and, in some cases, regional insecurity

The True Colours of Carbon

Carbon offset projects in developing countries are one of the principal mechanisms designed to reduce greenhouse gas emissions and promote sustainable development yet have critical limitations in both areas. Here we present a framework for categorizing carbon offset projects according to four general approaches to the reduction of greenhouse gas emissions: (1) efficiency ('Brown'); innovation ('Red'), terrestrial sequestration ('Green') or sequestration in aquatic environments ('Blue'). Analysis of the 6109 CDM projects currently in the CDM "pipeline" reveals that 99% are Brown or Red, and only 1% are Green or Blue, yet Green and Blue projects typically offer a far greater range of benefits for ecosystems and society. The analysis concludes that the designers of emissions trading schemes should endorse Green and Blue offset projects as preferred forms of emissions offsetting, and that firms using offsets for compliance purposes be required to declare in public reports the colours of their offset acquisitions. Such reform will help redirect demand in carbon markets toward blue and green offset projects, increasing the sustainability outcomes of carbon offset developments

A test of the ash-free dry weight technique on the developmental stages of Patiriella spp. (Echinodermata : Asteroidea)

Determination of the ash-free dry weight (AFDW) of marine specimens requires samples to be rinsed, soaked, and centrifuged. Problems associated with this technique were examined with the developmental stages of seastar species (Patiriella) with different modes of development. The influence of three rinsing solutions (ammonium formate [AF], filtered seawater [FSW], and reverse osmosis water [RO]) was assessed. The hypothesis that the AFDW technique is a measure of organic material was addressed by drying inorganic salts. Developmental stages of Patiriella calcar rinsed in FSW were twice as heavy as those rinsed in RO or AE indicating that samples should be rinsed in RO or AF before weighing. Soaking treatments had a significant effect on the AFDW of samples of P. calcar (planktonic developer), indicating that the rinsing period should be brief. Zygotes of Patiriella re gularis (planktonic developer) were significantly heavier than ova or gastrulae, regardless of treatment. In contrast, there were no significant differences in the AFDW of any stages or treatments of Patiriella exigua (benthic developer). This may be due to the presence of a modified fertilization envelope, which protects these benthic embryos. Inorganic salts with water of crystallization and FSW lost 20-75% and 14% of their dry weight, respectively, after ashing. We propose that salt ions may retain water, which does not evaporate during drying but is lost during ashing, resulting in the overestimation of sample AFDW. If a similar process occurs in the developmental stages of marine invertebrates, changes in the intracellular ionic composition through development may result in inaccurate estimates of biomass

Effect of Ammonium Enrichment on Animal and Algal Biomass of the Coral Pocillopora damicornis

Algal and animal biomass parameters of colonies of the Pacific coral Pocillopora damicornis (Linnaeus) were measured as a function of time of exposure to elevated concentrations of seawater ammonium (20 and 50 uM [(NH4)2S04]) ranging from 2 to 8 weeks. Areal concentrations of zooxanthellae, chlorophyll, and protein increased with 20 uM ammonium addition. During the 8-week period of exposure to 20 uM ammonium, the population density of zooxanthellae increased from 3.5 to 7.5 x 105 cells cm-2, chlorophyll a content of zooxanthellae increased from 5.7 to 8.6 pg, and animal protein concentration doubled (from 0.74 to 1.38 mg cm-2). These data indicate that both the coral animal and the zooxanthellae respond to the addition of exogenous dissolved inorganic nitrogen provided as 20 uM ammonium. Growth of the symbiotic association in response to the addition of 20 uM ammonium adds further evidence to support the argument that growth of tropical symbioses is limited by the availability of nitrogen. However, the coral response is likely to depend on the concentration of ammonium provided, because the biomass parameters of corals held at 50 uM ammonium did not change significantly with time of exposure to the added nutrient

Chapter 17: Vulnerability of coral reefs of the Great Barrier Reef to climate change

The Great Barrier Reef (GBR) contains the most extensive coral reef ecosystem on earth. It consists of 2900 coral reefs and 900 coral cays that cover approximately 20,000 km2 of the total 345,000 km2 area of the GBR Marine Park. As a consequence of unusually high summer sea surface temperatures, between 42 to 60 percent of the reefs of the GBR experienced mass coral bleaching in 19988. Bleaching was also reported from 31 other nations around the world during 1997–1998. For example, about 50 percent of reefs in the Indian Ocean and south Asia lost much of their coral cover, and an estimated 16 percent of the world’s area of coral reefs was severely damaged. The event coincided with the strongest recorded El Niño-Southern Oscillation event (ENSO) and one of the warmest years on record.This is Chapter 17 of Climate change and the Great Barrier Reef: a vulnerability assessment. The entire book can be found at http://hdl.handle.net/11017/13