Effects of ocean acidification on growth and feeding rates of spotted jellyfish
Phyllorhiza punctata early life stage/polyps.
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1
Center for Marine and Environmental Sciences (MARE), Portugal
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2
Portuguese Institute of Ocean and Atmosphere (IPMA), Portugal
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3
Department of Biological and Environmental Sciences, University of Gothenburg, Sweden
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4
Escola Superior de Turismo e Tecnologia do Mar, Politécnico de Leiria, Portugal
The increase of atmospheric carbon dioxide (CO2) is causing the reduction of the seawater pH. Is well known that ocean acidification affects marine organisms causing impacts on its survival and growth rates. In recent years, jellyfish blooms have been increasing the interaction of humans with such organisms, leading to socioeconomic negative impacts. In order to better understand jellyfish blooms dynamics, is essential achieve a better knowledge about the impacts on the different aspects of jellyfish life cycle, both attached polyps and free-swimming medusae. In this study, it was evaluated the effect of ocean acidification on the growth and ingestion rate of Phyllorhiza punctata polyps, when submitted to projected values of seawater pH for the year 2100 (a decrease of 0.3-0.4 units of pH) and extreme values (decrease of 1-2 units of pH).
Three polyps of P. punctata with a similar size (1027 ± 76µm) were placed in microplates containing 5 ml of non-CO2-enriched seawater (pH = 8.1) and CO2-enriched seawater (pH = 7.5, 7.0, 6.5, 6.0). Salinity and temperature were kept constant and equal to 35 and 22, respectively. Prior feeding experiments, polyps were subjected to a 24 hours period of starvation. After that, the polyps were exposed to 50 newly hatched Artemia nauplii. After 1 hour the remaining nauplii were counted.
Feeding rate (prey ind-1 hour-1) was calculate as the number of prey ingested per polyp per hour. The obtained results showed a significant linear relationship between pH and feeding rate (F4,75=52.832 p < 0.001), with feeding rate decreasing with pH (Fig. 1).
For growth rate, one polyp per well with similar size (312 ± 41µm) were transferred to 3 mL 24 wells microplates containing 2 mL of seawater at the same conditions described in previous section. Polyps were fed ad libitum every 2 days with Brachionus sp. and measured every 5 days. Water was changed daily.
The growth rate (mm day-1) was calculated from the relationship between time and size. The pH decrease showed a negative impact on growth rate, inducing a decrease from 19.34 ± 0.685 mm day-1 (pH 8.1) to 14.82 ± 0.732 mm day-1 (pH 6.5) and 14.87 ± 0.930 mm day-1 (pH 6.0) (Fig. 2). Significant differences (H4,50 = 20.867, p < 0.001) were only observed between pH 6.5 and 6.0 (Dunn's method).
The obtained results suggest that polyps of Phyllorhiza punctata may have some resistance to pH levels expected to the year 2100 (a decrease of 0.3 – 0.4 units of pH). Nevertheless, the exposition to extremes value of pH (6.5 and 6.0) showed a clear negative impact on polyp growth.
Although an increase in prey ingestion was expected to compensate the increase cost in basal energy due to acidosis caused by a decrease in pH, in this work it was observed a reduction in ingestion rate, which may contribute to the decrease observed in growth and even affect other biological processes (e.g. reproduction).
Other studies found that when organisms are exposed to both acidification and temperature increase the effect of the acidification may be ameliorated or exacerbated by the temperature increase.
Future studies should evaluate the effect of pH on asexual reproduction and the combined effect of an increased temperature, in order to better understand how global changes will affect Phyllorhiza punctata jellyfish both on polyp and free-swimming medusae.
Acknowledgements
Financial support by FCT through project UID/MAR/04292, Jellyfisheries (POCI-01-0145-FEDER-016772), the Postdoctoral grants attributed to SC Marques (SFRH/BPD/110400/2015), and the Integrated Programme of SR&TD “Smart Valorization of Endogenous Marine Biological Resources Under a Changing Climate” (Centro-01-0145-FEDER-000018), co-funded by Centro 2020 program, Portugal 2020, European Union, through the European Regional Development Fund.
Keywords:
Ocean acidification (OA),
jellyfish,
Phyllorhiza punctata,
Growth and ingestion rate,
Early life cycle
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Poster Presentation
Topic:
Global Change, Invasive Species and Conservation
Citation:
Marques
DF,
Marques
SC,
Duarte
IM,
Dupont
S and
Leandro
S
(2019). Effects of ocean acidification on growth and feeding rates of spotted jellyfish
Phyllorhiza punctata early life stage/polyps..
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00131
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Received:
07 Jun 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Dr. Daniel F Marques, Center for Marine and Environmental Sciences (MARE), Lisbon, Portugal, dfmarques88@gmail.com