Papers by Jason Hall-Spencer
Ocean acidification is expected to affect the biodiversity and function of marine ecosystems due ... more Ocean acidification is expected to affect the biodiversity and function of marine ecosystems due to the community-level consequences of direct physiological responses of organisms to changing ocean chemistry. Changes in rates of growth, survival, and reproduction in species that either benefit from (‘winners’) or are impacted by (‘losers’) ocean acidification can affect the abundance and productivity of populations. Shifts in population size or growth will alter the structure and function of marine food webs at the level of marine communities, with potentially important consequences for resources used by society. The magnitude of changes in biodiversity and ecosystem function expected by 2100 in response to expanding ocean acidification are not well understood, and could range from mild shifts in the abundances of species, to large changes in the diversity of marine communities, major disruption of ecosystem function, and large alterations in the ecosystem services important to society.
Fish exhibit impaired sensory function and altered behaviour at levels of ocean acidification exp... more Fish exhibit impaired sensory function and altered behaviour at levels of ocean acidification expected to occur owing to anthropogenic carbon dioxide emissions during this century. We provide the first evidence of the effects of ocean acidification on reproductive behaviour of fish in the wild. Satellite and sneaker male ocellated wrasse (Symphodus ocellatus) compete to fertilize eggs guarded by dominant nesting males. Key mating behaviours such as dominant male courtship and nest defence did not differ between sites with ambient versus elevated CO 2 concentrations. Dominant males did, however, experience significantly lower rates of pair spawning at elevated CO 2 levels. Despite the higher risk of sperm competition found at elevated CO 2 , we also found a trend of lower satellite and sneaker male paternity at elevated CO 2. Given the importance of fish for food security and ecosystem stability, this study highlights the need for targeted research into the effects of rising CO 2 levels on patterns of reproduction in wild fish.
The in situ eeects of ocean acidification on zooplankton communities remain largely unexplored. U... more The in situ eeects of ocean acidification on zooplankton communities remain largely unexplored. Using natural volcanic CO 2 seep sites around tropical coral communities, we show a threefold reduction in the biomass of demersal zooplankton in high-CO 2 sites compared with sites with ambient CO 2. Diierences were consistent across two reefs and three expeditions. Abundances were reduced in most taxonomic groups. There were no regime shifts in zooplankton community composition and no diierences in fatty acid composition between CO 2 levels, suggesting that ocean acidification aaects the food quantity but not the quality for nocturnal plankton feeders. Emergence trap data show that the observed reduction in demersal plankton may be partly attributable to altered habitat. Ocean acidification changes coral community composition from branching to massive bouldering coral species, and our data suggest that bouldering corals represent inferior daytime shelter for demersal zooplankton. Since zooplankton represent a major source of nutrients for corals, fish and other planktivores, this ecological feedback may represent an additional mechanism of how coral reefs will be aaected by ocean acidification.
Anthropogenic CO 2 emissions are being taken up from the atmosphere by the oceans, increasing the... more Anthropogenic CO 2 emissions are being taken up from the atmosphere by the oceans, increasing the availability of dissolved inorganic carbon but reducing both the carbonate saturation and pH of seawater. This ocean acidification affects biological processes in a wide range of marine taxa. Here, we assess the likely responses of 'nuisance' species to ocean acidification, meaning those organisms that have undesirable effects from a human perspective. Based on a synthesis of evidence available to date, we predict increased growth and toxicity in harmful algal bloom species, and a significant increase in invasive algae in response to increased CO 2 availability. Blooms of stinging jellyfish are also expected to increase since they are highly resilient to acidification. The effects of ocean acidification on invasive molluscs (eg, oyster drills), damaging echinoderms (eg, crown-of-thorns starfish), and a wide range of nuisance taxa will vary depending on species and location. In the USA, for example, the invasive crab Carcinus maenas is resilient to projected increases in CO 2 and its impact on marine communities is expected to increase since it feeds on organisms that respond to ocean acidification with weaker defensive traits and lower recruitment. Conversely, the Red King Crab, Paralithodes camtschaticus, is adversely affected by acidification and so is expected to die back in the Barents Sea which it has invaded. Overall, we suspect that there will be an increase in nuisance species, as many have traits that are resilient to the combined warming and acidification caused by rising CO 2 levels; region-specific assessments are needed to understand responses of nuisance species in local habitats. Finally, we highlight the need for targeted studies of the effects of global change on particularly harmful marine taxa such as the seaweed Caulerpa taxifolia, the starfish Asterias amurensis, several invasive ascidians, and the lionfish Pterois volitans.
Excessive CO 2 in the present-day ocean–atmosphere system is causing ocean acidification, and is ... more Excessive CO 2 in the present-day ocean–atmosphere system is causing ocean acidification, and is likely to cause a severe biodiversity decline in the future 1 , mirroring eeects in many past mass extinctions 2–4. Fossil records demonstrate that organisms surviving such events were often smaller than those before 5,6 , a phenomenon called the Lilliput eeect 7. Here, we show that two gastropod species adapted to acidified seawater at shallow-water CO 2 seeps were smaller than those found in normal pH conditions and had higher mass-specific energy consumption but significantly lower whole-animal metabolic energy demand. These physiological changes allowed the animals to maintain calcification and to partially repair shell dissolution. These observations of the long-term chronic eeects of increased CO 2 levels forewarn of changes we can expect in marine ecosystems as CO 2 emissions continue to rise unchecked, and support the hypothesis that ocean acidification contributed to past extinction events. The ability to adapt through dwarfing can confer physiological advantages as the rate of CO 2 emissions continues to increase. The present rate of ocean acidification is a global concern because many of the mass extinction events that affected evolution of life on Earth are associated with evidence for elevated CO 2 and global warming, triggered by large-scale continental volcanism 3. These include the largest known extinction event, which occurred in the late Permian 2,8 , where atmospheric CO 2 levels are estimated to have increased by a factor of four to six 9,10 , and the Late Triassic event that saw a doubling in CO 2 levels 4 and was the most severe extinction to have affected extant groups such as scleractinian corals 11. Evidence that ocean acidification due to volcanism played a significant role in past marine extinctions comes from analyses of physiological selectivity 12 , and changes in shell mineralogy and lithology 13. In the immediate aftermath of the mass extinction events, many of the survivors were smaller than before 5 (for example, brachiopods 14 , gastropods 14 , bivalves and shelled cephalopods 6); a phenomenon termed the 'Lilliput effect' 7. After the most severe Late Permian extinction, gastropod species remained relatively small for millions of years 15. One hypothesis is that this dwarfing was an adaptation to ocean acidification to mitigate against the increased energetic cost of carbonate secretion 8. Calcifiers use the ion transporter Ca 2+ ATPase to build shells/skeletons which pumps protons out of the extracellular calcifying medium, increasing the internal pH and favouring calcification. This is an energetically expensive process 16 , the cost of which increases for animals exposed to high p CO 2 conditions. For instance, scleractinian corals have an extra metabolic cost of about 10% per 0.1 unit decrease in seawater pH (ref. 17). It is possible that faced with an increase in calcification costs, some species may adapt by decreasing in size 18. Areas with naturally high levels of CO 2 provide opportunities to study the adaptation of organisms exposed to chronic hyper-capnia 19,20. At such sites, increased CO 2 levels cause biodiversity loss on sufficiently large spatial and temporal scales to reveal ocean acidification effects at the ecosystem level 21,22. Off Vulcano Island, Sicily 23 , seep gas composition is 97–98% CO 2 , which acidifies the surrounding waters down to pH T 5.64 (where pH T is the pH value based on the total hydrogen ion concentration scale) near the main seeps, rising to ambient levels of pH T 8.2 over a distance of around 400 m (ref. 23). Traces of other hydrothermal gases (H 2 , CH 4 and H 2 S) are also present near the seeps but become undetectable around 5 m away 23. Seawater temperature and oxygen levels reach ambient values a few tens of metres from the main seep area. At about 100 m from the main seeps the nassariid gastropods Nassarius corniculus and Cyclope neritea are abundant on coarse sand and gravel (Fig. 1). These species are widespread in coastal lagoons and salt marshes in the Mediterranean as well as at shallow-water hydrothermal seeps (for example, off Milos 24 and Pantelle-ria 25). We know that populations of C. neritea and N. corniculus had developed at the CO 2 seeps because their shells had paucispiral protoconches indicating these snails lack a planktotrophic larval stage (see Supplementary Information for more details). Seawater off Vulcano has been acidified since the late Pleistocene epoch 23 and a dwarf population of N. corniculus has been present for at least 30 years 25 , providing an opportunity to study chronic effects of ocean acidification on gastropods submitted to high CO 2 levels over multiple generations. Here, we compared gastropods living in naturally acidified shallow-water conditions near CO 2 seeps off Vulcano with those
Current climate policy and issues of energy security mean wind farms are being built at an increa... more Current climate policy and issues of energy security mean wind farms are being built at an increasing rate to meet energy demand. As wind farm development is very likely in the Mediterranean Sea, we provide an assessment of the offshore wind potential and identify expected biological effects of such developments in the region. We break new ground here by identifying potential offshore wind farm (OWF) " hotspots " in the Mediterranean. Using lessons learned in Northern Europe, and small-scale experiments in the Mediterranean, we identify sensitive species and habitats that will likely be influenced by OWFs in both these hotspot areas and at a basin level. This information will be valuable to guide policy governing OWF development and will inform the industry as and when environmental impact assessments are required for the Mediterranean Sea.
Until now, few sightings of the alien lionfish Pterois miles have been reported in the Mediterran... more Until now, few sightings of the alien lionfish Pterois miles have been reported in the Mediterranean and it was questionable whether the species could invade this region like it has in the western Atlantic. Here, we present evidence from divers and fishermen that lionfish have recently increased in abundance and within a year colonised almost the entire south eastern coast of Cyprus, likely due to sea surface warming. At least 23 different fish are reported of which 6 were removed. Groups of lionfish exhibiting mating behaviour have been noted for the first time in the Mediterranean. Managers need this information and should alert stakeholders to the potential ecological and socioeconomic impacts that may arise from a lionfish invasion. Actions could involve incentives to engage divers and fishermen in lionfish removal programmes, as these have worked well at shallow depths in the Caribbean. Given that the Suez Canal has recently been widened and deepened, measures will need to be put in place to help prevent further invasion.
Marine Ecology, Jun 1, 2011
The possible effects of ocean acidification on the calcareous skeleton of the Mediterranean bryoz... more The possible effects of ocean acidification on the calcareous skeleton of the Mediterranean bryozoan Myriapora truncata (Pallas, 1766) were studied by transplanting live and dead colonies into an area of natural volcanic CO 2 vents at Ischia (Gulf of Naples, Tyrrhenian Sea), Italy. Morphology and geochemistry were compared between colonies from normal (mean pH= 8.07, min. pH 7.95), below-normal (mean pH 7.66, min. pH 7.32) and acidic (mean pH 7.43, min. pH 6.83) conditions after colonies had been exposed in ...
Nature Climate Change, 2015
Excessive CO 2 in the present-day ocean-atmosphere system is causing ocean acidification, and is ... more Excessive CO 2 in the present-day ocean-atmosphere system is causing ocean acidification, and is likely to cause a severe biodiversity decline in the future 1 , mirroring e ects in many past mass extinctions 2-4 . Fossil records demonstrate that organisms surviving such events were often smaller than those before 5,6 , a phenomenon called the Lilliput e ect 7 . Here, we show that two gastropod species adapted to acidified seawater at shallow-water CO 2 seeps were smaller than those found in normal pH conditions and had higher mass-specific energy consumption but significantly lower whole-animal metabolic energy demand. These physiological changes allowed the animals to maintain calcification and to partially repair shell dissolution. These observations of the long-term chronic e ects of increased CO 2 levels forewarn of changes we can expect in marine ecosystems as CO 2 emissions continue to rise unchecked, and support the hypothesis that ocean acidification contributed to past extinction events. The ability to adapt through dwarfing can confer physiological advantages as the rate of CO 2 emissions continues to increase.
The Biological bulletin, 2014
A natural pH gradient caused by marine CO2 seeps off Vulcano Island (Italy) was used to assess th... more A natural pH gradient caused by marine CO2 seeps off Vulcano Island (Italy) was used to assess the effects of ocean acidification on coccolithophores, which are abundant planktonic unicellular calcifiers. Such seeps are used as natural laboratories to study the effects of ocean acidification on marine ecosystems, since they cause long-term changes in seawater carbonate chemistry and pH, exposing the organisms to elevated CO2 concentrations and therefore mimicking future scenarios. Previous work at CO2 seeps has focused exclusively on benthic organisms. Here we show progressive depletion of 27 coccolithophore species, in terms of cell concentrations and diversity, along a calcite saturation gradient from Ωcalcite 6.4 to <1. Water collected close to the main CO2 seeps had the highest concentrations of malformed Emiliania huxleyi. These observations add to a growing body of evidence that ocean acidification may benefit some algae but will likely cause marine biodiversity loss, espec...
Ecology and Evolution, 2015
Ocean acidification causes biodiversity loss, alters ecosystems, and may impact food security, as... more Ocean acidification causes biodiversity loss, alters ecosystems, and may impact food security, as shells of small organisms dissolve easily in corrosive waters. There is a suggestion that photosynthetic organisms could mitigate ocean acidification on a local scale, through seagrass protection or seaweed cultivation, as net ecosystem organic production raises the saturation state of calcium carbonate making seawater less corrosive. Here, we used a natural gradient in calcium carbonate saturation, caused by shallow-water CO 2 seeps in the Mediterranean Sea, to assess whether seaweed that is resistant to acidification (Padina pavonica) could prevent adverse effects of acidification on epiphytic foraminifera. We found a reduction in the number of species of foraminifera as calcium carbonate saturation state fell and that the assemblage shifted from one dominated by calcareous species at reference sites (pH~8.19) to one dominated by agglutinated foraminifera at elevated levels of CO 2 (pH~7.71). It is expected that ocean acidification will result in changes in foraminiferal assemblage composition and agglutinated forms may become more prevalent. Although Padina did not prevent adverse effects of ocean acidification, high biomass stands of seagrass or seaweed farms might be more successful in protecting epiphytic foraminifera.
Genome announcements, 2015
Bacterial communities at a CO2 vent (pH 6.7) were compared with those at control (pH 8.0) and tra... more Bacterial communities at a CO2 vent (pH 6.7) were compared with those at control (pH 8.0) and transition sites (pH 7.6) using 16S rRNA metagenomics. Firmicutes and unclassified bacteria dominated across all sites, Proteobacteria, especially Gammaproteobacteria, declined, and Epsilonproteobacteria increased in the vent with an increase in Bacteroidetes at both the vent and transition sites.
Ocean acidification is increasingly recognized as a component of global change that could have a ... more 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. Communicated by H.-O. Pörtner. Electronic supplementary material The online version of this article (
Water, 2014
This study examines the potential effects of ocean acidification on countries and fisheries of th... more This study examines the potential effects of ocean acidification on countries and fisheries of the Mediterranean Sea. The implications for seafood security and supply are evaluated by examining the sensitivity of the Mediterranean to ocean acidification at chemical, biological, and macro-economic levels. The limited information available on impacts of ocean acidification on harvested (industrial, recreational, and artisanal fishing) and cultured species (aquaculture) prevents any biological impact assessment. However, it appears that non-developed nations around the Mediterranean, particularly those for which fisheries are increasing, yet rely heavily on artisanal fleets, are most greatly exposed to socioeconomic consequences from ocean acidification.
Scientific Reports, 2014
Vermetids form reefs in sub-tropical and warm-temperate waters that protect coasts from erosion, ... more Vermetids form reefs in sub-tropical and warm-temperate waters that protect coasts from erosion, regulate sediment transport and accumulation, serve as carbon sinks and provide habitat for other species. The gastropods that form these reefs brood encapsulated larvae; they are threatened by rapid environmental changes since their ability to disperse is very limited. We used transplant experiments along a natural CO 2 gradient to assess ocean acidification effects on the reef-building gastropod Dendropoma petraeum. We found that although D. petraeum were able to reproduce and brood at elevated levels of CO 2 , recruitment success was adversely affected. Long-term exposure to acidified conditions predicted for the year 2100 and beyond caused shell dissolution and a significant increase in shell Mg content. Unless CO 2 emissions are reduced and conservation measures taken, our results suggest these reefs are in danger of extinction within this century, with significant ecological and socioeconomic ramifications for coastal systems.
PLoS ONE, 2014
Ocean acidification is expected to alter marine systems, but there is uncertainty about its effec... more Ocean acidification is expected to alter marine systems, but there is uncertainty about its effects due to the logistical difficulties of testing its large-scale and long-term effects. Responses of biological communities to increases in carbon dioxide can be assessed at CO2 seeps that cause chronic exposure to lower seawater pH over localised areas of seabed. Shifts in macroalgal communities have been described at temperate and tropical pCO2 seeps, but temporal and spatial replication of these observations is needed to strengthen confidence our predictions, especially because very few studies have been replicated between seasons. Here we describe the seawater chemistry and seasonal variability of macroalgal communities at CO2 seeps off Methana (Aegean Sea). Monitoring from 2011 to 2013 showed that seawater pH decreased to levels predicted for the end of this century at the seep site with no confounding gradients in Total Alkalinity, salinity, temperature or wave exposure. Most nutrient levels were similar along the pH gradient; silicate increased significantly with decreasing pH, but it was not limiting for algal growth at all sites. Metal concentrations in seaweed tissues varied between sites but did not consistently increase with pCO2. Our data on the flora are consistent with results from laboratory experiments and observations at Mediterranean CO2 seep sites in that benthic communities decreased in calcifying algal cover and increased in brown algal cover with increasing pCO2. This differs from the typical macroalgal community response to stress, which is a decrease in perennial brown algae and proliferation of opportunistic green algae. Cystoseira corniculata was more abundant in autumn and Sargassum vulgare in spring, whereas the articulated coralline alga Jania rubens was more abundant at reference sites in autumn. Diversity decreased with increasing CO2 regardless of season. Our results show that benthic community responses to ocean acidification are strongly affected by season.
Ecology, 2014
Ocean acidification -chemical changes to the carbonate system of seawater -is emerging as a key e... more Ocean acidification -chemical changes to the carbonate system of seawater -is emerging as a key environmental challenge accompanying global warming and other human-induced perturbations. Considerable research seeks to define the scope and character of potential outcomes from this phenomenon, but a crucial impediment persists. Ecological theory, despite its power and utility, has been only peripherally applied to the problem. Here we sketch in broad strokes several areas where fundamental principles of ecology have the capacity to generate insight into ocean acidification's consequences. We focus on conceptual models that, when considered in the context of acidification, yield explicit predictions regarding a spectrum of population-and community-level effects, from narrowing of species ranges and shifts in patterns of demographic connectivity, to modified consumer-resource relationships, to ascendance of weedy taxa and loss of species diversity. Although our coverage represents only a small fraction of the breadth of possible insights achievable from the application of theory, our hope is that this initial foray will spur expanded efforts to blend experiments with theoretical approaches. The result promises to be a deeper and more nuanced understanding of ocean acidification and the ecological changes it portends. Running head: Theory and ocean acidification Gaylord et al. 3
Biogeosciences, 2012
Here we show the use of the 210 Pb-226 Ra excess method to determine the growth rate of two coral... more Here we show the use of the 210 Pb-226 Ra excess method to determine the growth rate of two corals from the world's largest known cold-water coral reef, Røst Reef, north of the Arctic circle off Norway. Colonies of each of the two species that build the reef, Lophelia pertusa and Madrepora oculata, were collected alive at 350 m depth using a submersible. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and trace element compositions were studied. 210 Pb and 226 Ra differ in the way they are incorporated into coral skeletons. Hence, to assess growth rates, we considered the exponential decrease of initially incorporated 210 Pb, as well as the increase in 210 Pb from the decay of 226 Ra and contamination with 210 Pb associated with Mn-Fe coatings that we were unable to remove completely from the oldest parts of the skeletons. 226 Ra activity was similar in both coral species, so, assuming constant uptake of 210 Pb through time, we used the 210 Pb-226 Ra chronology to calculate growth rates. The 45.5 cm long branch of M. oculata was 31 yr with an average linear growth rate of 14.4 ± 1.1 mm yr −1 (2.6 polyps per year). Despite cleaning, a correction for Mn-Fe oxide contamination was required for the oldest part of the colony; this correction corroborated our radiocarbon date of 40 yr and a mean growth rate of 2 polyps yr −1 . This rate is similar to the one obtained in aquarium experiments under optimal growth conditions.
… Ecology Progress Series, Jan 1, 2009
Fisheries closures are rapidly being developed to protect vulnerable marine ecosystems worldwide.... more Fisheries closures are rapidly being developed to protect vulnerable marine ecosystems worldwide. Satellite monitoring of fishing vessel activity indicates that these closures can work effectively with good compliance by international fleets even in remote areas. Here we summarise how remote fisheries closures were designed to protect Lophelia pertusa habitat in a region of the NE Atlantic that straddles the EU fishing zone and the high seas. We show how scientific records, fishers' knowledge and surveillance data on fishing activity can be combined to provide a powerful tool for the design of Marine Protected Areas.
Ices Journal of Marine Science, 1999
1999. The impact of Rapido trawling for scallops, Pecten jacobaeus (L.), on the benthos of the Gu... more 1999. The impact of Rapido trawling for scallops, Pecten jacobaeus (L.), on the benthos of the Gulf of Venice. -ICES Journal of Marine Science, 56: 111-124.
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Papers by Jason Hall-Spencer