No abstract

Abstract. We present a new natural carbon dioxide (CO2) system located off the southern coast of the island of La Palma (Canary Islands, Spain). Like CO2 seeps, these CO2 submarine groundwater discharges (SGDs) can be used as an analogue to study the effects of ocean acidification (OA) on the marine realm. With this aim, we present the chemical characterization of the area, describing the carbon system dynamics, by measuring pH, AT and CT and calculating Ω aragonite and calcite. Our explorations of the area have found several emission points with similar chemical features. Here, the CT varies from 2120.10 to 10 784.84 µmol kg−1, AT from 2415.20 to 10 817.12 µmol kg−1, pH from 7.12 to 8.07, Ω aragonite from 0.71 to 4.15 and Ω calcite from 1.09 to 6.49 units. Also, the CO2 emission flux varies between 2.8 and 28 kg CO2 d−1, becoming a significant source of carbon. These CO2 emissions, which are of volcanic origin, acidify the brackish groundwater that is discharged to the coast and alter the local seawater chemistry. Although this kind of acidified system is not a perfect image of future oceans, this area of La Palma is an exceptional spot to perform studies aimed at understanding the effect of different levels of OA on the functioning of marine ecosystems. These studies can then be used to comprehend how life has persisted through past eras, with higher atmospheric CO2, or to predict the consequences of present fossil fuel usage on the marine ecosystem of the future oceans.

In recent years, recurrent sea urchin mass mortalities in the Canary Islands have been registered. These mortality-related events have decimated 93% of the eastern Atlantic populations of the barren-forming sea urchin Diadema africanum. Two severe episodes of rough southeastern seas led to winter storms in February 2010 (Xynthia) and February 2018 (Emma) and preceded the last mass mortality event. We hypothesized that these events are related to the mass mortalities registered during the February in those years. Previous studies identified Neoparamoeba branchiphila as the causal agent of the disease, possibly acting in synergy with Vibrio alginolyticus and/or other pathogens. To determine the link between winter storms and the sea urchin pathogen community, we monitored the marine pathogen assemblage before and after the winter storm Filomena (February 2020) on Tenerife Island, on different habitats (sea water, sediment and algae) and in four species of sea urchin hosts (D. africanum, Arbacia lixula, Paracentrotus lividus and Sphaerechinus granularis). A total of six pathogens, including N. branchiphila, Vexillifera minutissima, Acanthamoeba sp., Vahlkampfia sp., V. alginolyticus and green colonies of Vibrio spp., were identified. Only small amoebas were found in sea urchins, while Vibrio species were more common in seawater, sediment and algae substrates. V. alginolyticus was occasionally detected in three sea urchins specimens, while N. branchiphila was found in the coelom of all four sea urchin studied. As previously hypothesized, a significant pathogen increment in seawater and in the sea urchin species D. africanum and P. lividus, was found after Filomena. Our results confirmed the relationship between the winter storms and marine pathogen dynamics. However, further studies are needed to demonstrate the direct relationship between these pathogen increases and the sea urchin mass mortalities.

No abstract

Abstract. We present a new natural carbon dioxide (CO2) system located off the southern coast of La Palma Island (Canary Islands, Spain). Like others CO2 seeps, these seeps can be used as an analogue to study the effects of ocean acidification (OA) on the marine realm. With this aim, we present an accurate chemical characterization of the seeps system carbon emissions, describing the carbon system dynamics, by measuring pH, AT and CT, as well as, Ω aragonite and calcite. Our explorations on the area have found several emission points with similar chemical features. Here, the CO2 emission flux varies between 2.8 kg CO2 d−1 to 28 kg CO2 d−1, becoming a significant source of carbon. CO2 seeps are of volcanic origin and the alteration of local ocean chemistry is due to acid brackish water discharges. Although this kind of acidified system is not a perfect image of future oceans, this area of La Palma island is an exceptional spot to perform studies aimed to understand the effect of different levels of OA on the functioning of marine ecosystems. These studies can then be used to comprehend how life has persisted through past Eras, with higher atmospheric CO2, or to predict the consequences of present fossil fuel usage on the marine ecosystem of the future oceans.