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The combined effects of increased temperature and ocean acidification on the early life history stages of Caribbean coral and its implication for the recovery potential of Florida reefs

The early life history stages of coral are an essential component determining the recovery potential of coral reefs through sexual reproduction and recruitment. The pelagic larval phase is inherent in all coral species regardless of differing reproductive strategies and is the only time in coral life history where large scale movement is possible allowing for the repopulation of reef areas both within and outside the natal reef habitat. In the face of climate change, the larval dispersal and recruitment phase will take place in a warmer more acidic ocean if we continue on the path of unabated fossil fuel emissions. While much research has focused on how increased temperature or ocean acidification affect coral larvae independently, our understanding of how these factors interact to shape larval response is limited, especially in regards to Caribbean coral species.

To gain a better understanding of how the early life history stages of Caribbean coral may be affected by climate change, this dissertation investigates the effects of increased temperature (2.5 °C above historical averages in the Florida Keys) and carbon dioxide levels (900-1000 parts per million CO2) on corals from the Florida Reef tract by investigating the effects on larval metabolism, survivorship, settlement, and post-settlement growth and survival. Additionally, a coupled biophysical model was developed to determine the potential changes in connectivity that may result from the biological effects of increased temperature and ocean acidification on the larval phase. The larval respiratory response of three Caribbean coral species revealed Orbicella faveolata as the most environmentally responsive with significant increases in respiration after 1 day exposure to increased temperature (68% greater than control conditions) with a counteracting effect of ocean acidification significantly decreasing respiration. The changes in metabolism over time correlated with decreased time to competency under elevated temperature in O. faveolata larvae, resulting in a greater number of settlers (76% greater than control) and a relative increase in local retention and self-recruitment rates as revealed by the biophysical model (5 and 7% greater than control respectively). However, when increased temperature occurred in combination with elevated CO2 levels, respiration was not significantly increased relative to control conditions and development of competency is minimally impacted. This resulted in a smaller increase in settlers (13% greater than control) and no significant changes in connectivity patterns. The post-settlement phase was similarly impacted with counteracting effects of increased temperature and ocean acidification on recruit growth.

Overall, this dissertation reveals the potential for adaptation to increased temperature in at least one important coral species (Orbicella faveolata) that is greatly diminished when encountered in combination with ocean acidification. These results encourage the reduction of carbon emissions to give coral species the chance to adapt to elevated temperatures through the recruitment of more resilient individuals without the additional stress of ocean acidification.

Continue reading ‘The combined effects of increased temperature and ocean acidification on the early life history stages of Caribbean coral and its implication for the recovery potential of Florida reefs’

Impact of ocean warming and acidification on the behaviour of two co-occurring gadid species, Boreogadus saida and Gadus morhua, from Svalbard

Ocean acidification induces strong behavioural alterations in marine fish as a consequence of acid-base regulatory processes in response to increasing environmental CO2 partial pressure. While these changes have been investigated in tropical and temperate fish species, nothing is known about behavioural effects on polar species. In particular, fishes of the Arctic Ocean will experience much greater acidification and warming than temperate or tropical species. Also, possible interactions of ocean warming and acidification are still understudied. Here we analysed the combined effects of warming and acidification on behavioural patterns of 2 fish species co-occurring around Svalbard, viz. polar cod Boreogadus saida and Atlantic cod Gadus morhua. We found a significant temperature effect on the spontaneous activity of B. saida, but not of G. morhua. Environmental CO2 did not significantly influence activity of either species. In contrast, behavioural laterality of B. saida was affected by CO2 but not by temperature. Behavioural laterality of G. morhua was not affected by temperature or CO2; however, in this species, a possible temperature dependency of CO2 effects on relative laterality may have been missed due to sample size restrictions. This study indicates that fish in polar ecosystems may undergo some, albeit less intense, behavioural disturbances under ocean acidification and in combination with ocean warming than observed in tropical species. It further accentuates species-specific differences in vulnerability.

Continue reading ‘Impact of ocean warming and acidification on the behaviour of two co-occurring gadid species, Boreogadus saida and Gadus morhua, from Svalbard’

Ocean acidification impacts spine integrity but not regenerative capacity of spines and tube feet in adult sea urchins

Increasing atmospheric carbon dioxide (CO2) has resulted in a change in seawater chemistry and lowering of pH, referred to as ocean acidification. Understanding how different organisms and processes respond to ocean acidification is vital to predict how marine ecosystems will be altered under future scenarios of continued environmental change. Regenerative processes involving biomineralization in marine calcifiers such as sea urchins are predicted to be especially vulnerable. In this study, the effect of ocean acidification on regeneration of external appendages (spines and tube feet) was investigated in the sea urchin Lytechinus variegatus exposed to ambient (546 µatm), intermediate (1027 µatm) and high (1841 µatm) partial pressure of CO2 (pCO2) for eight weeks. The rate of regeneration was maintained in spines and tube feet throughout two periods of amputation and regrowth under conditions of elevated pCO2. Increased expression of several biomineralization-related genes indicated molecular compensatory mechanisms; however, the structural integrity of both regenerating and homeostatic spines was compromised in high pCO2 conditions. Indicators of physiological fitness (righting response, growth rate, coelomocyte concentration and composition) were not affected by increasing pCO2, but compromised spine integrity is likely to have negative consequences for defence capabilities and therefore survival of these ecologically and economically important organisms.

Continue reading ‘Ocean acidification impacts spine integrity but not regenerative capacity of spines and tube feet in adult sea urchins’

The hunt for a super coral: can cold-water corals adapt to ocean acidification?

When most people think of a coral reef they are imagining a sunny tropical beach, but many coral species are actually found in the dark, cold waters of the deep sea. These corals, commonly known as cold-water corals due to their preference for low temperatures, form beautiful ecosystems that are teeming with life. One of the largest threats to these slow-growing and fragile ecosystems is ocean acidification, the gradual reduction in the pH of our oceans caused by the excess carbon dioxide humans emit into the atmosphere. By the year 2100, it is expected that over 70% of stony corals in the deep sea will live in waters that are so acidic that they may corrode corals and make it difficult or even impossible for them to form hard skeletons.

In a previous publication scientists from Marine Conservation Institute and Temple University showed that cold-water corals in different ocean basins had completely opposite responses to ocean acidification, suggesting some populations may be much more resilient to climate change. What about individual corals within a population – could they also exhibit different responses? Enter the hunt for a ‘super coral’, corals with a genetic makeup that render them more resilient to ocean acidification. In an increasingly acidic ocean super corals would have higher survival and reproductive rates, and over many generations would comprise an increasingly large portion of the population. If these super corals already exist in the deep sea, there is a chance that cold-water coral populations may be able to adapt quickly enough to survive in the face of climate change.

Continue reading ‘The hunt for a super coral: can cold-water corals adapt to ocean acidification?’

Is the chemical composition of biomass the agent by which ocean acidification influences on zooplankton ecology?

Climate change impacts prevail on marine pelagic systems and food webs, including zooplankton, the key link between primary producers and fish. Several metabolic, physiological, and ecological responses of zooplankton species and communities to global stressors have recently been tested, with an emerging field in assessing effects of combined climate-related factors. Yet, integrative studies are needed to understand how ocean acidification interacts with global warming, mediating zooplankton body chemistry and ecology. Here, we tested the combined effects of global warming and ocean acidification, predicted for the year 2100, on a community of calanoid copepods, a ubiquitously important mesozooplankton compartment. Warming combined with tested pCO2 increase affected metabolism, altered stable isotope composition and fatty acid contents, and reduced zooplankton fitness, leading to lower copepodite abundances and decreased body sizes, and ultimately reduced survival. These interactive effects of temperature and acidification indicate that metabolism-driven chemical responses may be the underlying correlates of ecological effects observed in zooplankton communities, and highlight the importance of testing combined stressors with a regression approach when identifying possible effects on higher trophic levels.

Continue reading ‘Is the chemical composition of biomass the agent by which ocean acidification influences on zooplankton ecology?’

Building international capacity to monitor, understand, and act on ocean acidification

The Ocean Foundation commits to building international capacity to address ocean acidification through four types of actions: monitoring, analyzing, engaging and acting.


Observing how, where, and how quickly is change occurring
Ocean acidification is causing rapid changes in chemistry, and these changes are not consistent across the globe. The first step to fighting ocean acidification is to monitor our waters so that we can better understand how, where, and how quickly the change is occurring. We have tools to monitor both the chemistry such as the change in pH and the biology like the change in algae distribution. Right now, entire regions of the ocean have limited or no capacity for such monitoring. The Ocean Foundation will work to increase monitoring capacity by providing training workshops for early career scientists, deploying tailored kits that enable monitoring efforts, and by supporting the Global Ocean Acidification Observing Network (the GOA-ON).

Continue reading ‘Building international capacity to monitor, understand, and act on ocean acidification’

World gone sour: the impact of CO2 emissions

You’re no doubt familiar with the ongoing and highly contentious political debate on the connection between carbon dioxide (CO2) emissions and climate change. But as we battle over greenhouse gases in the air, we overlook an equally serious problem: the increasing acidity of our oceans.

Little known by the public, the impact of CO2 emissions on our oceans is called ocean acidification.

Not all of the carbon dioxide emitted by human industrial activities remains in the atmosphere. In fact, about one-third of the CO2 released as a result of the burning of fossil fuels (like coal, oil and natural gas) currently ends up in the ocean. The ocean is the largest natural carbon sink on Earth; in other words, it acts as a reservoir, accumulating and storing carbon. This reduces the CO2 build-up in our atmosphere, but it also comes at a considerable price.

As ocean waters absorb CO2, the water becomes more acidic. The acidity of global surface waters has increased by 30 percent over the course of the last two centuries—a rather staggering figure—and this rate of acidification is only expected to accelerate. This doesn’t mean that the oceans will become acid. What it means is that there may be catastrophic impacts to marine ecosystems within the next hundred years.

Continue reading ‘World gone sour: the impact of CO2 emissions’

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Ocean acidification in the IPCC AR5 WG II

OUP book