A unique temperate rocky coastal hydrothermal vent system (Whakaari–White Island, Bay of Plenty, New Zealand): constraints for ocean acidification studies

Abstract

In situ effects of ocean acidification are increasingly studied at submarine CO2 vents. Here we present a preliminary investigation into the water chemistry and biology of cool temperate CO2 vents near Whakaari–White Island, New Zealand. Water samples were collected inside three vent shafts, within vents at a distance of 2m from the shaft and at control sites. Vent samples contained both seawater pH on the total scale (pHT) and carbonate saturation states that were severely reduced, creating conditions as predicted for beyond the year 2100. Vent samples showed lower salinities, higher temperatures and greater nutrient concentrations. Sulfide levels were elevated and mercury levels were at concentrations considered toxic at all vent and control sites, but stable organic and inorganic ligands were present, as deduced from Cu speciation data, potentially mediating harmful effects on local organisms. The biological investigations focused on phytoplankton, zooplankton and macroalgae. Interestingly, we found lower abundances but higher diversity of phytoplankton and zooplankton at sites in the direct vicinity of Whakaari. Follow-up studies will need a combination of methods and approaches to attribute observations to specific drivers. The Whakaari vents represent a unique ecosystem with considerable biogeochemical complexity, which, like many other vent systems globally, require care in their use as a model of ‘future oceans’.

Ocean acidification locks algal communities in a species‐poor early successional stage

“…The gas being released at our study site is 98 ± 3 (SD) % CO 2 , and although concentrations of hydrogen sulfide are detected at the main vent, they are below detection limits ~50 m away from the main vents (Agostini et al, 2015) and the study site used in this study is more than 300 m away from the main vent. The possibility remains that other trace elements or heavy metals (as yet unmeasured) may be present either in the water or bioaccumulated in biota, as has been shown in other CO 2 seeps (Mirasole et al, 2020; Mishra et al, 2020; Vizzini et al, 2013; Zitoun et al, 2020), which could influence the response of marine organisms to ocean acidification. An additional consideration for CO 2 seeps is that they demonstrate the consequences of future ocean acidification but in the absence of concurrent ocean warming (Hughes et al, 2017), and temperatures will mediate the response of organisms and communities to future ocean acidification.…”

“…Natural analogues provide a number of benefits for advancing our understanding about the responses of shallow‐water marine communities to ocean acidification conditions, but they are not perfect analogues. Carbonate chemistry at some CO 2 seeps can be highly variable (Rastrick et al, 2018), and areas in close proximity to CO 2 vents can be enriched in some metals and toxins (Vizzini et al, 2013; Zitoun et al, 2020). It is possible to reduce such confounding factors by avoiding toxic areas and only selecting sites a suitable distance away, since contamination from hydrothermal fluids can be quickly diluted by mixing with seawater (Agostini et al, 2015; Pichler et al, 2019).…”

Volcanic CO2 seep geochemistry and use in understanding ocean acidification

“…Other calcified taxa showed consistent reductions in abundance in the extreme OA scenario, which were similar among coccolithophores, gastropods, bryozoans and serpulid worms. Our evidence that marine taxa potentially vulnerable to low pH conditions may in some instances thrive under OA is not new, as local environmental conditions like nutrient availability (Connell et al 2017) or exposure over multiple generations (Cornwall et al 2020), may help some organisms to thrive (Zitoun et al 2020).…”

“…As such, care is needed when using these systems as natural proxies or studying OA effects on marine organisms. Trace element contents in seawater surrounding hydrothermal seeps have been measured in several cases, including at Vulcano Island, the main focus of this paper (Boatta et al 2013;Brinkman 2014;Donnarumma et al 2019;Pichler et al 2019;Zitoun et al 2020). Bio-availability of trace-elements depends on metal speciation (Rainbow 2002;Vizzini et al 2013;Mishra et al 2020) and so seeps provide areas in which to assess the effects of ocean acidification on trace element toxicity.…”

Keith Hunter’s legacy to Marine Science in New Zealand

“…He was a strong supporter of this journal where he served as co-Editor between 2008 and 2011. The articles published in this research front cover a small range of Keith's research interests and include articles on marine chemistry with specific emphasis on the marine carbonate system, ocean acidification, trace metal biogeochemistry and trace metal speciation (Cornwall and Hurd 2020;Ellwood et al 2020;Frew et al 2020;Hassler et al 2020;Hurd et al 2020;Mosley and Liss 2020;Vance et al 2020;Zitoun et al 2020).…”