benefits and impacts for the marine environment due to the

Benefits and impacts for the marine environment due to the pH changes

Caterina Lanfredi / Valentina De Santis / Arianna Azzellino

caterina.lanfredi@polimi.it / valentina.desantis@polimi.it /

arianna.azzellino@polimi.it

DESARC - MARESANUS

DEcreasing Seawater Acidification Removing Carbon

La rimozione di CO2 dall’atmosfera e il progetto Desarc-Maresanus. 4-5 febbraio, 2020

Approximately 1/3 of the atmospheric CO2 is absorbed by the oceans, where it is transformed into carbonic acid, which rapidly dissociates into bicarbonate, carbonate and H+ ions, resulting in an increase of acidity of the sea waters and altering marine ecosystems.

More CO2 into the atmosphere→Higher concentration of H+ ions into the sea→ Lower pH value

ACIDIFICATION PROCESS

Laboratory experiments show that calcification rates of many marine calcifyers, like certain corals, foraminifera, coccolithophores and shellfish, reduce under more acidic (high CO2) conditions.

Confidence levels (IPCC)

EFFECTS OF ACIDIFICATION

Turley et al., 2006

Rapid ocean acidification

Jason Hall-Spencer

iStockphoto.com/Eduardo Luzzatti

Coral Reefs

iStockphoto.com/t.light

Changes in marine ecosystems

iStockphoto.com/Richard Carey

Calcifying organisms

Ulf Riebesell; GEOMAR

Marine snails

Steve Ringman

Species directly affected by acidification

Species indirectly affected by acidification

The marine food web is highly interconnected. While some species like shelled organisms are directly affected by ocean acidification, other species are affected indirectly because they eat shelled organisms or live in habitats they created.

Nitrogen fixation stimulated

NASA's Goddard Space Flight Center/USGS)

Economic losses

iStockphoto.com/Thomas Bradford

Commercially important organismsEFFECTS OF ACIDIFICATION

pH CHANGES IN THE MARINE ENVIRONMENT

Most of the literature on the biological response to changes in seawatercarbonate chemistry has focused on acidifying condition.

The problem of ocean acidification

affects also the Mediterranean Sea

EFFECTS OF ALKALINIZATION

The potential environmental effects and the magnitude of the ocean limingimpact depend on different factors such as the following:

• the variation in the pH level generated at the deployment site;• the deployment depth (m)• the applied spatial scale: local (localized in the vicinity of the ship; along the

ship route; the volume of water moved by the ship) regional?• the applied temporal scale: short-term (hours to days) long-term (months to

years)• the ecosystems involved (coastal or pelagic)

EFFECTS OF ALKALINIZATION

The variation of ocean alkalinity influences the saturation state of carbonate minerals that are essentials for marine carbonate-producing organisms, such as reefs populated with benthic species (coral shellfish and green macroalgae) and the pelagic ecosystems (e.g., components of planktonic ecosystem such as coccolithophores, foraminifera, pteropods/heteropods).

EFFECTS OF ALKALINIZATION: Benthonic species

The marine biota relies on pH to regulate ion transport;

The energy they invest to maintain intra- and extra-cellular pH depends on ambient pH.

Experimental studies reveal that the increase of alkalinity could disrupt the acid-base balance of marine organisms (i.e. Carcinus meanas).

Ophioderma longicauda Lithophyllum stictaeformePorites porites

Marine calcifies which mediate calcification by providing nucleation sites on abiological template (e.g. corals, shellfish, crustacean) are most likely toincrease their calcification rate in response to rising alkalinity and saturationstate.

If suitable control of alkalinity were possible, it might benefit such species byprotecting them against the damaging effect of ocean acidification.

Experimental studies have been conducted on the capability of some marine species to produce and dissolute carbonate at elevated levels of alkalinity.

These deposit feeders process carbonate sand and rubble through their digestive tract and dissolve CaCO3 as part of their digestive process increasing ambient total alkalinity.

Density of animals: 1 ind/m2

This additional alkalinity could partially buffer changes in seawater pH associated with increasing atmospheric CO2 locally, thus reducing the impact of ocean acidification on coral growth.

EFFECTS OF ALKALINIZATION: Phytoplankton

Studies have reviewed the pH tolerance of marine phytoplankton, one examining theresults obtained from batch culture experiments, the other from a variety of laboratoryand enclosure experiments.

Response to variation of carbonateion concentration of seawater

Incomplete growth of coccolithsMalformed coccoliths

Both studies show that changes in growth rate (or substrate uptake) for a given changein pH vary considerably. Some species are rather insensitive to changes in pH. However,there are species relatively sensitive to changes in pH.

pH values outside the range of 7.0 to 8.5 can preclude the growth of some species.

The growth rates of the 3 dinoflagellates weremeasured at different pH within the range of 7.5to 10.

The growth rate was highest at pH 7.5 to 8.0 inall species.

It is evident from the compiled data on pH limitsfor marine phytoplankton growth that the abilityto tolerate high pH is not related to any particularalgal groups, but rather is species-specific.

In such environments, pH changes may drivespecies succession of phytoplankton and limitprimary production, because many species arequite sensitive to high pH.

To avoid the risk of pH shock,

Water Quality Guidelines of both the U.S. EnvironmentalProtection Agency (1976) and the Canadian Council of Ministersof the Environment (1999)

recommend to protect marine biota with narrow pH tolerances,human activities should not result in a change in environmentalpH of more than 0.2 pH units from normally occurring values.

EFFECTS OF ALKALINIZATION: Guidelines

EFFECTS OF ALKALINIZATION: Zooplankton

Principaligruppitassonomicierappresentatividellozooplanctonoloplanctonico

PHYLUM SOTTOGRUPPI GENERICOMUNI

Protozoa Dinoflagellata Noctiluca

Zooflagellata Bodo

Foraminifera Globigerina

Radiolaria Aulcantha

Ciliophora Strombidium;Favella

Cnidaria Medusae Aglantha;Cynea

Siphonophora Physalia;Nanomia

Ctenophora Tentaculata Pleurobrachia

Nuda Boroe

Chaetognatha Sagitta

Annelida Polychaeta Tomopteris

Mollusca Heteropoda Atlanta

Thecosomata Limacina;Clio

Gymnosomata Clione

Arthropoda Cladocera Evadne;Podon

Ostracoda Conchoecia

Copepoda Calanus;Oithona

Mysidacea Neomysis

Amphipoda Parathemisto

Euphausiacea Euphausia

Decapoda Sergestes;Lucifer

Urochordata Appendicularia Oikopleura

Thaliacea Salpa;Pyrosoma

Principaligruppitassonomicierappresentatividellozooplanctonoloplanctonico Classiditagliaesuddivisioneincomponentiautotrofeedeterotrofedegliorganismidelplancton

GRUPPO TAGLIA ORGANISMIPRESENTI

Femtoplancton 0.02-0.2µm Viruspresentinellacolonnad'acqua

Picoplancton 0.2-2.0µm Batteri,Archaea,Cianobatteri,Picoeucariotiautotrofi

Nanoplancton 2.0-20µm Eucariotiunicellulari,diatomeebentoniche

Microplancton 20-200µm Microalgheplanctoniche,amebe,tintinnidi,foraminiferi,rotiferi

Mesoplancton 0.2-2.0cm Copepodi

Macroplancton 2.0-20cm Policheti,anfipodi

Megaplancton 20-200cm Meduse,sinofori,ctenofori

Effective pH valuescausing toxic effectsin marine organisms.Copepod T. japonicusLC 50: 11mM DIC

pH variability of the Mediterranean Sea

During the time-period of 1995-2011, at 10 m-depth:

• The estimated rate of pH decrease is 0.003 ±0.001 per year.

• The magnitude of seasonal pH variation at the Dyfamed site was 0.25 ± 0.03.

• pH fluctuated among years, ranging across 0.03, 0.05, 0.05, and 0.02 pH units in winter, spring, summer and fall, respectively.

MAIN ISSUES OF ALKALINIZATION

• Effects of ocean alkalization on ocean biogeochemistry andmarine ecosystems have mainly been explored throughtheoretical and modeling exercises and much less so inlaboratory or in-situ experiments;

• The bioavailability of important trace metals is likely impactedby changes in ocean chemistry;

• Food-web effects are complex and difficult to predict butbiomass and size structure of copepods (zooplanktonicorganisms) for example have seen to be negatively affected;

• Many factors in addition to acidification may influence algalcomposition, growth rates, and productivity (e.g. pollution, UV,sea surface temperature and limiting factors e.g. nitrate,phosphate, and iron) may play crucial role

CONCLUSIONS

• Alkalinization has the potential to counter-balance the pH increasethat is occurring also in the Mediterranean sea;

• The available knowledge on the alkalinity enhancement is verylimited.

• Research on alkalization effects has focused on specific speciesrather than ecosystem.

• Experimental studies are required to improve the understanding of the responses of marine organisms and ecosystem to localized pH variations.

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