Marine Heatwave, Harmful Algae Blooms and an Extensive Fish Kill Event During 2013 in South Australia

Roberts, Shane; Ruth, Paul D. van; Wilkinson, Clinton; Bastianello, Stella S.; Bansemer, Matthew S.

doi:10.3389/fmars.2019.00610

Cited by 78 publications

(57 citation statements)

References 38 publications

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“…Previous studies have shown both negative and positive effects of heatwaves on marine organisms (Bartosiewicz et al, 2019, Lugo et al, 2020, Pansch et al, 2018, Roberts et al, 2019, Siegle et al, 2018, Stuhr et al, 2017. Here, we systematically disentangled how thermal experience and genotype affect the mortality and growth responses of the Southern Ocean diatom Actinocyclus actinochilus to simulated heatwaves, to show how both negative and positive heatwave effects can occur.…”

Section: Discussionmentioning

confidence: 94%

Surviving heatwaves: thermal experience predicts life and death in a Southern Ocean diatom

Samuels

Rynearson

Collins

2020

Preprint

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Extreme environmental fluctuations such as marine heatwaves (MHWs) can have devastating effects on ecosystem health and functioning through rapid population declines and destabilisation of trophic interactions. However, recent studies have highlighted that population tolerance to MHWs is variable, with some populations even benefitting from MHWs. A number of factors can explain variation in responses between populations including their genetic variation, previous thermal experience and the intensity and duration of the heatwave itself. We disentangle the contributions of these factors on population survival and post-heatwave growth rates by experimentally simulating heatwaves (7.5 or 9.2 °C, for up to nine days) for three genotypes of the Southern Ocean diatom Actinocyclus actinochilus. The effects of simulated heatwaves on mortality and population growth varied with both genotype and thermal experience. Firstly, hotter and longer heatwaves increased mortality and decreased post-heatwave growth rates relative to milder, shorter heatwaves. Secondly, growth above the thermal optimum before heatwaves exacerbated heatwave-associated negative effects, leading to higher mortality during heatwaves and slower growth after heatwaves. Thirdly, hotter and longer heatwaves resulted in more pronounced changes to thermal optima (Topt) immediately following heatwaves. Finally, there is substantial intraspecific variation in mortality during heatwaves and in post-heatwave growth. Our findings shed light on the potential of Southern Ocean diatoms to tolerate MHWs, which will increase both in frequency and in intensity under future climate change.

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Section: Discussionmentioning

confidence: 94%

Surviving heatwaves: thermal experience predicts life and death in a Southern Ocean diatom

Samuels

Rynearson

Collins

2020

Preprint

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“…Heatwaves can actuate change in community structure by stimulating emigration and causing regionalized mortality (Sanford et al, 2019). They have been associated with phytoplankton blooms and the development of hazardous blooms species that can cause fish mortality in other species (Roberts et al, 2019). Heatwaves can also impact fishery populations as they have been observed to play a role in the recruitment of both invertebrate (Chandrapavan et al, 2019) and vertebrate species (Smith et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Changing Physical Conditions and Lower and Upper Trophic Level Responses on the US Northeast Shelf

et al. 2020

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Sea surface temperature (SST), salinity, and chlorophyll concentration (CHL) have changed in the US Northeast Shelf ecosystem over recent decades. The changes in these parameters were distinctly marked by change points around the year 2012 resulting in a 0.83 • C increase in SST, a 0.3 PSU increase in salinity, and decrease in CHL in excess of 0.4 mg m −3. Where temperature and salinity shifted in mean level around their respective change points, CHL declined in a more monotonic fashion. Modeled data suggest that the shift in CHL resulted in a greater contribution of picoand nanophytoplankton and a decreased contribution of microphytoplankton to overall CHL. Complementary estimates of the contribution of different phytoplankton functional types suggest a diminished contribution of diatoms to the phytoplankton community. Hence, not only is there evidence of a decline in the overall primary production capacity of the ecosystem, but also evidence of a fundamental change in the size and quality of phytoplankton supporting food webs. Two ecosystem responses to the observed changes in SST, salinity, and CHL were analyzed. Both length and weight at age have declined for a number of species, and both measures of growth appear to be negatively associated with temperature and positively associated with CHL. Biomass of fish and macroinvertebrates has declined in recent years, with a decrease in pelagic species associated with a decrease in CHL, while the decline in demersal species was associated with an increase in temperature. Collectively, these ecosystem changes appear to be the result of the complex interactions of both thermal effects and changes at the base of the food web.

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“…The influence of a changing climate on oceanic conditions is often envisaged as a long-term phenomenon occurring gradually over decades, with the most severe consequences occurring close to year 2100, progressing cumulatively over time and tracking modeled projections (Hobday, Cochrane, et al, 2016;Schmidt & Boyd, 2016). However, abrupt ecosystem degradation, as a result of extreme events, has now been documented in kelp forests, temperate benthic habitats, coral reefs, and polar systems (Grebmeier, 2012;Hughes et al, 2017;Pansch et al, 2018;Roberts, Van Ruth, Wilkinson, Bastianello, & Bansemer, 2019;Smale et al, 2019;Wernberg et al, 2016). Some of the most immediate consequences of rapidly emerging episodic heat stress events include altered commercial fish stocks, changes to planktonic communities, species redistributions, coastal expansion of toxic algal blooms, and increasing instances of disease outbreaks (Bodin, 2017;Filbee-Dexter & Wernberg, 2018;Hobday, Cochrane, et al, 2016;McCabe et al, 2016;Paerl, 2018;Pecl et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Marine heat waves have occurred in locales ranging from tropical to cold temperate waters, extended over thousands of square kilometres and persisted on timeframes from weeks to months (see http://www.marin eheat waves.org/track er. html; Frölicher, Fischer, & Gruber, 2018;Hobday, Cochrane, et al, 2016;Oliver et al, 2018;Roberts et al, 2019). It is of particular concern that marine heat waves are now more severe and of longer duration than at any time during the past 90 years (Oliver et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

How do we overcome abrupt degradation of marine ecosystems and meet the challenge of heat waves and climate extremes?

Ainsworth

Hurd

Gates

et al. 2019

Global Change Biology

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Extreme heat wave events are now causing ecosystem degradation across marine ecosystems. The consequences of this heat‐induced damage range from the rapid loss of habitat‐forming organisms, through to a reduction in the services that ecosystems support, and ultimately to impacts on human health and society. How we tackle the sudden emergence of ecosystem‐wide degradation has not yet been addressed in the context of marine heat waves. An examination of recent marine heat waves from around Australia points to the potential important role that respite or refuge from environmental extremes can play in enabling organismal survival. However, most ecological interventions are being devised with a target of mid to late‐century implementation, at which time many of the ecosystems, that the interventions are targeted towards, will have already undergone repeated and widespread heat wave induced degradation. Here, our assessment of the merits of proposed ecological interventions, across a spectrum of approaches, to counter marine environmental extremes, reveals a lack preparedness to counter the effects of extreme conditions on marine ecosystems. The ecological influence of these extremes are projected to continue to impact marine ecosystems in the coming years, long before these interventions can be developed. Our assessment reveals that approaches which are technologically ready and likely to be socially acceptable are locally deployable only, whereas those which are scalable—for example to features as large as major reef systems—are not close to being testable, and are unlikely to obtain social licence for deployment. Knowledge of the environmental timescales for survival of extremes, via respite or refuge, inferred from field observations will help test such intervention tools. The growing frequency of extreme events such as marine heat waves increases the urgency to consider mitigation and intervention tools that support organismal and ecosystem survival in the immediate future, while global climate mitigation and/or intervention are formulated.

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Marine Heatwave, Harmful Algae Blooms and an Extensive Fish Kill Event During 2013 in South Australia

Cited by 78 publications

References 38 publications

Surviving heatwaves: thermal experience predicts life and death in a Southern Ocean diatom

Surviving heatwaves: thermal experience predicts life and death in a Southern Ocean diatom

Changing Physical Conditions and Lower and Upper Trophic Level Responses on the US Northeast Shelf

How do we overcome abrupt degradation of marine ecosystems and meet the challenge of heat waves and climate extremes?

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