Trends in Parasitology
Volume 28, Issue 9, September 2012, Pages 365-369
Journal home page for Trends in Parasitology

Opinion
Host–parasite interactions: a litmus test for ocean acidification?

https://doi.org/10.1016/j.pt.2012.06.007Get rights and content

The effects of ocean acidification (OA) on marine species and ecosystems have received significant scientific attention in the past 10 years. However, to date, the effects of OA on host–parasite interactions have been largely ignored. As parasites play a multidimensional role in the regulation of marine population, community, and ecosystem dynamics, this knowledge gap may result in an incomplete understanding of the consequences of OA. In addition, the impact of stressors associated with OA on host–parasite interactions may serve as an indicator of future changes to the biodiversity of marine systems. This opinion article discusses the potential effects of OA on host and parasite species and proposes the use of parasites as bioindicators of OA disturbance.

Section snippets

Increased CO2, seawater chemistry, and marine life

Anthropogenic emissions of carbon dioxide (CO2) since the beginning of the industrial revolution (ca. 1780) have caused atmospheric CO2 to increase at an unprecedented rate and have resulted in a corresponding increase in dissolved CO2 in the global ocean [1]. This addition of CO2 has altered the carbonate chemistry of seawater, increasing hydrogen ion (H+) and bicarbonate ion (HCO3) concentrations, and reducing the concentration of carbonate ions (CO32–) (Box 1). The predominant consequences

Physiological consequences of OA

As described in Box 1, the addition of CO2 to seawater alters the concentrations of hydrogen (H+), bicarbonate (HCO3), and carbonate (CO32–) ions. These chemical species play important roles in fundamental physiological processes such as protein function, enzyme activity, ion transport, and calcification. Protein function and enzyme activity are responsible for many important physiological processes, including growth and the generation of metabolic energy. A change in the electrochemical state

Current OA research

The effect of altered environmental pH on marine systems and organisms has been investigated as a basic biological and biogeochemical parameter since the early 20th century (reviewed in [15]). Recently, however, investigations into decreased pH in the context of OA have become the focus of increased scientific attention. Other than a few isolated studies, the majority of research on OA has been conducted since the late 1980s, with 79% of OA articles published since 2004 (see bibliometric

Ecological role of parasites

Undoubtedly, pH is an important regulatory factor in parasite physiology and population dynamics, as demonstrated by research into the effects of pH on parasites in culture [27], in the internal environment of the host [28], and, perhaps most importantly, in freshwater habitats 29, 30, 31, 32. Accordingly, it is likely that changing oceanic pH will have an effect on marine parasite survival or infectivity, especially for species that produce free-living developmental stages (reviewed in [33]).

Parasites as bioindicators

The use of host–parasite interactions as an effective bioindicator of anthropogenic perturbation of community biodiversity and ecosystem structure has been frequently encouraged since 1997 38, 39, 40, 41. Parasites are a ubiquitous component of all ecosystems and, due to their complex life cycles, experience a wide range of environments which represent most biological niches possibly affected by abiotic stressors, for example, the internal compartments of host species (endoparasites), the

Concluding remarks

Despite the abundance of evidence which suggests that the overall effects of OA will be negative, a significant number of marine organisms either benefit from, or are unaffected by, the associated changes to seawater chemistry [1]. For example, some pteropod species which naturally migrate through oxygen minimum zones are unaffected by elevated CO2 levels [54], whereas certain coccolithophore species increase calcification rates under simulated OA conditions [55]. These positive or neutral

Acknowledgements

We wish to thank A. Studer and H. Randhawa for their constructive comments on an earlier draft of this article. This research was funded by the University of Otago, New Zealand.

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