Posts Tagged 'vents'

The emissions of the Tagoro submarine volcano (Canary Islands, Atlantic Ocean): effects on the physical and chemical properties of the seawater

This chapter presents the changes and evolution of the physical and chemical properties of the seawater south of the El Hierro Island (Canary archipelago, Atlantic Ocean) as a consequence of the emissions of the Tagoro submarine volcano, over a 6 year study from 2011 to 2016. Since the eruption, a series of oceanographic studies have been carried out in the area focusing on the evolution of the redox potential and the pH, two master variables that control the chemical equilibrium in seawater. The changes experienced by the carbon dioxide system, the variations in the concentration of Fe(II) and their correlation with the decrease in the pH during the evolution of the volcano, from the beginning of the eruptive stage to the post-eruptive phase, are discussed. The increased TDFe(II) concentrations and the low associated pHT values have controlled the occurrence of an important fertilization event in the sea water around the volcano at the Island of El Hierro, providing optimal conditions for the regeneration of the area. The sites like the Tagoro submarine volcano, in its degasification stage, provide an excellent opportunity to study the carbonate system in a high CO2 world, the volcanic contribution to the global volcanic carbon flux and the potential environmental impact of these emissions on the surrounding ocean and the ecosystem.

Continue reading ‘The emissions of the Tagoro submarine volcano (Canary Islands, Atlantic Ocean): effects on the physical and chemical properties of the seawater’

Ocean acidification drives community shifts towards simplified non-calcified habitats in a subtropical−temperate transition zone

Rising atmospheric concentrations of carbon dioxide are causing surface seawater pH and carbonate ion concentrations to fall in a process known as ocean acidification. To assess the likely ecological effects of ocean acidification we compared intertidal and subtidal marine communities at increasing levels of pCO2 at recently discovered volcanic seeps off the Pacific coast of Japan (34° N). This study region is of particular interest for ocean acidification research as it has naturally low levels of surface seawater pCO2 (280–320 µatm) and is located at a transition zone between temperate and sub-tropical communities. We provide the first assessment of ocean acidification effects at a biogeographic boundary. Marine communities exposed to mean levels of pCO2 predicted by 2050 experienced periods of low aragonite saturation and high dissolved inorganic carbon. These two factors combined to cause marked community shifts and a major decline in biodiversity, including the loss of key habitat-forming species, with even more extreme community changes expected by 2100. Our results provide empirical evidence that near-future levels of pCO2 shift sub-tropical ecosystems from carbonate to fleshy algal dominated systems, accompanied by biodiversity loss and major simplification of the ecosystem.

Continue reading ‘Ocean acidification drives community shifts towards simplified non-calcified habitats in a subtropical−temperate transition zone’

Microhabitat change alters abundances of competing species and decreases species richness under ocean acidification

Highlights

• Niche segregation allows species to co-exist and maintain diversity.
• Ocean acidification could modify niche availability and niche segregation.
• Natural CO2 vents showed altered microhabitat availability and fish abundances.
• Competitively dominant fishes increased in density but others decreased.
• Fish species diversity decreases due to niche alteration under elevated CO2.

Abstract

Niche segregation allows competing species to capture resources in contrasting ways so they can co-exist and maintain diversity, yet global change is simplifying ecosystems and associated niche diversity. Whether climate perturbations alter niche occupancy among co-occurring species and affect species diversity is a key, but unanswered question. Using CO2 vents as natural analogues of ocean acidification, we show that competing fish species with overlapping diets are partially segregated across microhabitat niches and differently-orientated substrata under ambient CO2 conditions. Under elevated CO2, benthic microhabitats experienced a significant increase in non-calcifying turf and fleshy algae but a sharp reduction in calcareous algae. The increased availability of turf and fleshy algae supported increased densities of a competitively dominant species, whilst the reduction in calcifying algal microhabitats decreased densities of several subordinate species. The change in microhabitat availability also drove an increased overlap in microhabitat use among competing fishes at the vents, associated with a reduced fish species richness on horizontal substrates. We conclude that loss of preferred microhabitat niches, exacerbated by population proliferation of competitively dominant species, can drive population losses of less common and subordinate species, and reduce local species richness. The indirect effects of ocean acidification on microhabitat availability can therefore impair maintenance of species populations, and drive changes in local community and biodiversity patterns.

 

Continue reading ‘Microhabitat change alters abundances of competing species and decreases species richness under ocean acidification’

Impact of carbonate saturation on large Caribbean benthic foraminifera assemblages

Increasing atmospheric carbon dioxide and its dissolution in seawater have reduced ocean pH and carbonate ion concentration with potential implications to calcifying organisms. To assess the response of Caribbean benthic foraminifera to low carbonate saturation conditions, we analyzed benthic foraminifera abundance and relative distribution in proximity to low carbonate saturation submarine springs and at adjacent control sites. Our results show that the total abundance of benthic foraminifera is significantly lower at the low pH low calcite saturation submarine springs than at control sites, despite higher concentrations of inorganic carbon at the spring sites. The relative abundance of symbiont-bearing foraminifera and agglutinated foraminifera was higher at the low pH low calcite saturation submarine springs compared to control sites. These differences indicate that non-symbiont bearing heterotrophic calcareous foraminifera are more sensitive to the effects of ocean acidification than non-calcifying and symbiont bearing foraminifera, suggesting that future ocean acidification may impact natural benthic foraminifera populations.

Continue reading ‘Impact of carbonate saturation on large Caribbean benthic foraminifera assemblages’

Coccolithophore community response along a natural CO2 gradient off Methana (SW Saronikos Gulf, Greece, NE Mediterranean)

A natural pH gradient caused by marine CO2 seeps off the Methana peninsula (Saronikos Gulf, eastern Peloponnese peninsula) was used as a natural laboratory to assess potential effects of ocean acidification on coccolithophores. Coccolithophore communities were therefore investigated in plankton samples collected during September 2011, September 2016 and March 2017. The recorded cell concentrations were up to ~50 x103 cells/l, with a high Shannon index of up to 2.8, along a pH gradient from 7.61 to 8.18, with values being occasionally <7. Numerous holococcolithophore species represented 60–90% of the surface water assemblages in most samples during September samplings. Emiliania huxleyi was present only in low relative abundances in September samples, but it dominated in March assemblages. Neither malformed nor corroded coccolithophores were documented. Changes in the community structure can possibly be related to increased temperatures, while the overall trend associates low pH values with high cell densities. Our preliminary results indicate that in long-termed acidified, warm and stratified conditions, the study of the total coccolithophore assemblage may prove useful to recognize the intercommunity variability, which favors the increment of lightly calcified species such as holococcolithophores.

Continue reading ‘Coccolithophore community response along a natural CO2 gradient off Methana (SW Saronikos Gulf, Greece, NE Mediterranean)’

CO2 emissions boost the benefits of crop production by farming damselfish

Farming is a technique employed by both humans and animals to enhance crop yields, allowing their populations to increase beyond the natural carrying capacity of the environment. Using volcanic CO2 vents, we investigate how a species of herbivorous fish (the black scalyfin Parma alboscapularis) may use increasing anthropogenic CO2 emissions to enhance its crop yields. We found that these farming fish can take advantage of this resource enrichment, to grow crops within smaller territories and increase the capacity of the environment to support more densely packed fish populations.

Continue reading ‘CO2 emissions boost the benefits of crop production by farming damselfish’

Marine hydrothermal vents as templates for global change scenarios

Subsurface marine hydrothermal vents (HVs) may provide a particular advantage to better understand evolutionary conditions of the early earth and future climate predictions for marine life. Hydrothermal vents (HV) are unique extreme environments that share several similarities with projected global and climate change scenarios in marine systems (e.g., low pH due to high carbon dioxide and sulfite compounds, high temperature and turbidity, high loads of toxic chemicals such as H2S and trace metals). Particularly, shallow hydrothermal vents are easily accessible for short-term and long-term experiments. Research on organisms from shallow HVs may provide insights in the molecular, ecological, and evolutionary adaptations to extreme oceanic environments by comparing them with evolutionary related but less adapted biota. A shallow-water hydrothermal vent system at the northeast Taiwan coast has been intensively studied by several international research teams. These studies revealed astounding highlights at the levels of ecosystem (being fueled by photosynthesis and chemosynthesis), community (striking biodiversity changes due to mass mortality), population (retarded growth characteristics), individual (habitat attractive behavior), and molecular (adaptations to elevated concentrations of heavy metals, low pH, and elevated temperature). The present opinion paper evaluates the potential of shallow hydrothermal vents to be used as a templates for global change scenarios.

Continue reading ‘Marine hydrothermal vents as templates for global change scenarios’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,113,505 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book