Chapter: Volcanic past cycles indicators: paleoclimatology and extinctions using benthic and planktonic forams community dynamics

The Benthic and planktonic foraminiferal communities’ dynamics as volcanic past cycles indicators are very well placed within the Paleoclimatology and extinctions studies. We have showed a bit, of what is available to explain how communities have evolved in the past. The past volcanic activity has released as much carbon dioxide into the atmosphere as anthropogenic as predicted emissions projections for the twenty-first century and they are linked to increases in carbon dioxide emissions and with faunal patterns, with marine extinctions observed sediment cores after volcanic episodes, and this increase in carbon dioxide and other volcanic gaseous influences on global warming and ocean acidification is responsible for the extinction of three quarters of species on Earth on the past. For example, dinosaurs were pretty much extinct because of “The Deccan Traps”, an igneous province, one of the largest volcanic features on Earth, located on the west-central India, and the Siberian Traps have influenced the end-Permian extinction, in which more than 90% of life on Earth disappeared. Many patterns should be first understood to be able to forecast future climate change scenarios. We can however explain that the modern ongoing carbon dioxide emissions are similar to those that led to the end-Triassic mass extinction. The importance of understanding Earth’s deep water past is predicated on predicting how it will respond to future climate change. The mass extinction and high-stress conditions were explained by the intense Deccan volcanism leading to rapid global warming and cooling, with enhanced weathering, continental runoff, and ocean acidification, resulting in a carbonate crisis in the marine environment. The chronic explosive volcanic activity generated unstable benthic habitat colonized by only a few species. The increase in atmospheric CO2 concentrations lead to decreased pH and carbonate availability in the ocean, known as Ocean Acidification, and the ability of marine invertebrates to tolerate acidity are the ‘windows into the future’ to study. Cores with ashes and tephra in Papua New Guinea (PNG) during Expedition 363 sampled by the IODP show that total foraminiferal diversity was low when volcanic activity was in place detected by the presence of tephra and volcanic ashes. Foraminiferal density and diversity in PNG were high and similar to those observed on the Great Barrier Reef or other sites, however diversity decreases, and show inverse correlation by benthic foraminifera to high presence of ashes and tephra in the past. However, ecological studies from shallow reef environments observed increased foraminiferal dominance of opportunists when corals became rare from chronic or acute anthropogenic influences, for example with sewage and oil spills. Agglutinate taxa that do not rely on calcification will replace calcifying species, and we call it a fauna replacement by invasive species. Density and diversity of agglutinated taxa is also in decline, but are less marked than calcifying taxa in an environment where pH is low. Dissolution of foraminifera seen in marine sediment under elevated pCO2 unravels other direct ecological impacts. Impacts such as dissolution and loss of biogenesis of carbonate by other organisms that are under near-future pCO2 conditions, which will reach a problematic real-time scenario. None of the previous extinctions were as severe as the ecological or even taxonomic extinction in shallow carbonate areas which we are predicting. Because of the rate of increasing pCO2, and unfortunately, we expect that the increase in the temperature in the Holocene and the tendency until 2100 will take us to the warmest Pliocene climate with the unfortunate consequences of living in a warmer than optimum world. The variability based on the frequency and intensity of some events are one of the warmest our world has ever seen, reflecting changes in temperature derived from data from deep sea sediment core samples, and of course shells of benthic and planktonic Forams and other organisms like pollen act as proxies in drilled marine sediment cores reflecting historic climate. A unique fauna of foraminiferal species from these highly opposed environments created by differences in temperature in the past are recorded paleo cycles, of which responds to the amount of ice in the world, due to their high sensitivity to the environmental changes in the modern and past sediments. Here we show that tephra and ashes of IODP Hole U1485A (Exp. 363 WPWP) record a periodicity of explosive volcanism within the last 0.8 Myr. Possible triggering mechanisms for these mass flow deposits include earthquakes and associated tsunamis and shelf/slope sediment instabilities during times of rapid deposition such as can occur during river flood events. Over longer timescales, it is also possible that sea level played a role in the storage and release of sediment from the PNG shelf (although the shelf itself is very narrow) and from the paleo-valley of the Sepik River, which is a relatively large area presently few meters above sea level. Changes in diversity shows balance of alternating deep (cold) and shallow (warm) benthic foraminifera fauna along time in the past. The “at least” five decreases in diversity peaks in the past show that the response of the benthic community to adverse climate is a change in their ecological pattern. These changes can take a whole community and an entire ecosystem to extinctions, and we have already seen five extinctions along Earth’s history. And if history teaches us anything, it is how to react to and prepare for crisis rather than repeat mistakes. Research suggests we are fast approaching disastrous effects of this sixth Anthropocene extinction. However, we can successfully surmount the challenges of biodiversity loss and climate change and dramatically alter the trajectory if we can pinpoint and remediate problems within a near future. With our planet “in crisis”, evidence demonstrates widespread ecological collapse and biodiversity loss. We know that as average temperatures rise and the frequency of extremely warm years increases, the impacts of habitat loss and fragmentation become even more increasingly apparent. We are with without a doubt entering a sixth mass extinction event because of the rapid decline in biodiversity. The majority of these species inhabit environmentally delicate tropical and subtropical areas susceptible to human impacts. This refers to a situation where the extinction of one species affects other species that rely on it for survival, thereby also placing them at a ‘domino effect’ risk of extinction as part of a destructive chain reaction. Stop cutting and burn forests, stop global trade of wild species, study and protect, preserve, and conserve our planet’s biodiversity.

Beck Eichler P. P. & Barker C. P., 2020. Volcanic past cycles indicators: paleoclimatology and extinctions using benthic and planktonic forams community dynamics. In: Beck Eichler P. P. & Barker C. P. (Eds.), Benthic Foraminiferal Ecology, pp 133-145. Springer, Cham. Chapter (restricted access).

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