Effects of ocean acidification on the brown alga "Padina pavonica": decalcification due to acute and chronic events

[EN] Since the industrial revolution, anthropogenic CO2 emissions have caused ocean acidification, which particularly affects calcified organisms. Given the fan-like calcified fronds of the brown alga Padina pavonica, we evaluated the acute (shortterm) effects of a sudden pH drop due to a submarine volcanic eruption (October 2011–early March 2012) affecting offshore waters around El Hierro Island (Canary Islands, Spain). We further studied the chronic (long-term) effects of the continuous decrease in pH in the last decades around the Canarian waters. In both the observational and retrospective studies (using herbarium collections of P. pavonica thalli from the overall Canarian Archipelago), the percent of surface calcium carbonate coverage of P. pavonica thalli were contrasted with oceanographic data collected either in situ (volcanic eruption event) or from the ESTOC marine observatory data series (herbarium study). Results showed that this calcified alga is sensitive to acute and chronic environmental pH changes. In both cases, pH changes predicted surface thallus calcification, including a progressive decalcification over the last three decades. This result concurs with previous studies where calcareous organisms decalcify under more acidic conditions. Hence, Padina pavonica can be implemented as a bio-indicator of ocean acidification (at short and long time scales) for monitoring purposes over wide geographic ranges, as this macroalga is affected and thrives (unlike strict calcifiers) under more acidic conditions

IMBER mini-Symposium with Spanish oceanographers

Celebrado en la Sala de Grado de la Facultad de Ciencias del Mar (ULPGC) el 18 de junio de 2013

The submarine volcano eruption off El Hierro Island: Effects on the scattering migrant biota and the evolution of the pelagic communities

[EN] The submarine volcano eruption off El Hierro Island (Canary Islands) on 10 October 2011 promoted dramatic perturbation of the water column leading to changes in the distribution of pelagic fauna. To study the response of the scattering biota, we combined acoustic data with hydrographic profiles and concurrent sea surface turbidity indexes from satellite imagery. We also monitored changes in the plankton and nekton communities through the eruptive and post-eruptive phases. Decrease of oxygen, acidification, rising temperature and deposition of chemicals in shallow waters resulted in a reduction of epipelagic stocks and a disruption of diel vertical migration (nocturnal ascent) of mesopelagic organisms. Furthermore, decreased light levels at depth caused by extinction in the volcanic plume resulted in a significant shallowing of the deep acoustic scattering layer. Once the eruption ceased, the distribution and abundances of the pelagic biota returned to baseline levels. There was no evidence of a volcano-induced bloom in the plankton community.

Impact of increasing pCO2 on marine potential respiratory activity

[EN]Due to the increasing atmospheric CO2, several on-going research programs, including the German-led KOSMOS GC14 experiment, are evaluating the impact of acidification on marine organisms, intent to predict their future. In the KOSMOS GC14 mesocosm experiment we assessed the effect of different CO2 concentrations on metabolism in microplankton (0.7-50µm size) and in biogenic particles harvested by sediment traps.

A preview of the ocean acidification’s impact on potential respiratory activity

[EN]The increase in the anthropogenic CO2 released to the atmosphere, induces an increase in the dissolved CO2 in the ocean, causing elevated pCO2 values and a pH decrease. Due to the increasing atmospheric CO2, several on-going research programs are evaluating the impact of acidification on marine organisms, intent to predict their future. In this mesocosm experiment (KOSMOS 14GC), we assessed the effect of different CO2 concentrations on metabolism in microplankton (0.7-50μm size) and in biogenic particles harvested by sediment traps.