Changes in abundance of fish-parasitic gnathiid isopods associated with warm-water bleaching events on the northern Great Barrier Reef

Sikkel, Paul C.; Richardson, M. A.; Sun, Derek; Narvaez, Pauline; Feeney, William E.; Grutter, Alexandra S.

doi:10.1007/s00338-019-01835-3

Cited by 20 publications

(21 citation statements)

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“…Not surprisingly, where the broader ecosystem is examined, impacts from severe coral mortality ripple through the associated fauna and impact the entire ecosystem (Richardson et al 2018;Sikkel et al 2019;Wilson et al 2019). Stuart-Smith et al (2018) surveyed a year after the 2016 marine heatwave hit the GBR, finding widespread impacts throughout coral reef ecosystems, with an expected patchiness as local impacts varied.…”

Section: What Have We Learned From Gcbe-3?mentioning

confidence: 99%

The 2014–2017 global-scale coral bleaching event: insights and impacts

Eakin

Sweatman

Brainard³

2019

Coral Reefs

274

184

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2014-2017 was an unprecedented period of successive record-breaking hot years, which coincided with the most severe, widespread, and longest-lasting globalscale coral bleaching event ever recorded. The 2014-2017 global-scale coral bleaching event (GCBE) resulted in very high coral mortality on many reefs, rapid deterioration of reef structures, and far-reaching environmental impacts. Through the papers in this special issue of Coral Reefs entitled The 2014-2017 Global Coral Bleaching Event: Drivers, Impacts, and Lessons Learned, as well as papers published elsewhere, we have a good analysis of the 2014-2017 GCBE and its impacts. These studies have provided key insights into how climate change-driven marine heatwaves are destroying coral reef ecosystems: (a) The 2014-2017 GCBE is unique in the satellite record in its spatial scale, duration, intensity, and repetition of bleaching. (b) The impacts have been the most severe ever seen at many reefs. (c) Timing of observations matters and needs to be considered during the analysis of impacts. (d) On both global and local scales, the intensity of heat stress and impacts varied. (e) We continue to see important differences among and within coral taxa, with key roles played by algal symbionts and the microbiome. (f) Heat stress and bleaching both play a role in subsequent disease, which plays a key role in mortality. (g) Impacts ripple far beyond corals, with significant changes to the fish and invertebrate community that may last decades. (h) The structure of both individual coral's skeletons and entire reefs has been eroded much more quickly than previously realized. (i) The 2014-2017 GCBE provided little support for the proposed ''lifeboat'' hypothesis, whereby deep or mesophotic reefs serve as a means of coral reef salvation. (j) While marine protected areas (MPAs) provide protection from local stressors, they not only do not protect reefs from global-scale stressors, but also here is also little evidence they provide significant resilience. Keywords Coral bleaching Á Heat stress Á Coral Reef Watch Á CoralTemp Á Marine heatwave Á Symbionts Á Microbiome Á Coral disease Á El Niño Á ENSO

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Section: What Have We Learned From Gcbe-3?mentioning

confidence: 99%

The 2014–2017 global-scale coral bleaching event: insights and impacts

Eakin

Sweatman

Brainard³

2019

Coral Reefs

274

184

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“…However, such studies largely ignore the cryptofauna that comprises most of coral reef's biodiversity and biomass, including parasites [67]. In the only long-term monitoring study of any marine parasitic crustacean, Sikkel et al (2019) [65] reported that during extreme warm-water events in the GBR parasitic gnathiid isopod populations crashed. The findings reported here are consistent with their hypothesis that this may be attributable, in part, to a direct effect of temperature on gnathiid mortality.…”

Section: Discussionmentioning

confidence: 99%

“…However even with such a large presence in coral reef communities, they are significantly underrepresented in ecological studies [10,55,63]. Coral reef parasites are also ectothermic, and as such, may be affected by changes to their environmental temperature [10,11,[64][65][66][67]. Some parasites are ectoparasitic and would be highly vulnerable to increased temperatures.…”

Section: Introductionmentioning

confidence: 99%

“…A long-term monitoring study of gnathiid isopods off Lizard Island, GBR, revealed a significant decrease in gnathiid abundance during extreme warm-water periods associated with bleaching events, compared with cooler periods in the same year or during non-bleaching years [65]. However, the cause of this decline was unclear.…”

Section: Introductionmentioning

confidence: 99%

“…However, the cause of this decline was unclear. [65] hypothesized that the direct effects of temperature on gnathiid mortality may have partly contributed to the decline in gnathiid abundance. The aim of this study therefore, was to assess the direct effect of a rapid increase in seawater temperatures on mortality of shallow-reef gnathiid isopods.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Acute Seawater Temperature Increase on the Survival of a Fish Ectoparasite

Shodipo

Duong

Graba‐Landry

et al. 2020

Oceans

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Extreme warming events that contribute to mass coral bleaching are occurring with increasing regularity, raising questions about their effect on coral reef ecological interactions. However, the effects of such events on parasite-host interactions are largely ignored. Gnathiid isopods are common, highly mobile, external parasites of coral reef fishes, that feed on blood during the juvenile stage. They have direct and indirect impacts on their fish hosts, and are the major food source for cleaner fishes. However, how these interactions might be impacted by increased temperatures is unknown. We examined the effects of acute temperature increases, similar to those observed during mass bleaching events, on survivorship of gnathiid isopod juveniles. Laboratory experiments were conducted using individuals from one species (Gnathia aureamaculosa) from the Great Barrier Reef (GBR), and multiple unknown species from the central Philippines. Fed and unfed GBR gnathiids were held in temperature treatments of 29 °C to 32 °C and fed Philippines gnathiids were held at 28 °C to 36 °C. Gnathiids from both locations showed rapid mortality when held in temperatures 2 °C to 3 °C above average seasonal sea surface temperature (32 °C). This suggests environmental changes in temperature can influence gnathiid survival, which could have significant ecological consequences for host-parasite-cleaner fish interactions during increased temperature events.

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