Burdinaren bidezko itsasoaren fertilizazioa klima-aldaketaren aurkako tresna interesgarria ote?

Berotegi efektuko gasak, batez ere CO2, atmosferan metatzerakoan mundu mailako beroketa gertatzen da. Erregai fosilen erreketatik askaturiko CO2 erdiak gutxi gorabehera atmosferan irauten du. Baina beste erdia lur-isurbideak eta batez ere ozeanoek xurgatzen dute. Itsasoan CO2-ren ziklo biogeokimikoa gertatzen da eta CO2 bahitu eta itsas hondoraino garraiatzen da edota CO2 askatzen da (itsas komunitateen arnasketaprozesuen bidez). Bi prozesu hauen arteko balantze netoa positiboa denez, itsasoa planetako karbonoaren erreserbagai handiena dugu. Karbonoaren garraioa ponpa fisikoak eta biologikoak egiten dute gainazaletik itsas hondoraino. Itsas hondoko CO2-ren emendioaren bi heren, fitoplanktonak, zooplanktonak, prokariotoek (bakterioek eta arkeoek) eta birusek osatzen duten ponpa biologikoari dagozkio. Fitoplanktona disolbaturiko elikagaiez eta karbono dioxidoz elikatzen da, eta CO2 materia organiko bihurtzen da fotosintesiaren bidez. Ekoizpen primario hau itsasoko zona fotikoan (lehenengo 100 metroetan) gertatzen da. Zooplanktonak eta prokariotoek bermineralizatzen dute fitoplanktonak askaturiko materia organiko gehiena baina gainontzekoa itsas hondorantz eraman eta han bahitzen da. Gainazaleko nitrato eta fosfatoen kontzentrazioak oso baxuak dira itsaso gehienetan, eta beraz, ponpa biologikoaren indarra elikagai hauen eskuragarritasunaren menpe dago. Baina, HNLC (High Nutrient Low Chlorophyll) zonaldeetan fitoplanktonaren hazkuntza ez dago elikagai hauen menpe, kontzentrazio handietan egon arren fitoplanktonaren hazkuntza txikia delako. John Martinek 1988an burdinaren hipotesia plazaratu zuenetik ("Give me a half tank of iron and I will give you an ice age"), burdinaren bidezko 12 fertilizazio saio egin dira Ozeano Antartikoko, Ozeano Artikoko edo Ozeano Bare ekuatorialeko HNLC zonaldeetan. Eskala txikiko eta epe motzeko saioak izan dira, non burdinaren fertilizazioa egin eta sulfato ferrikoaren kontzentrazio txikiak gehitzen diren. Saio hauek agerian utzi dute HNLC zonaldeetako burdinaren eskasiak mugatu egiten duela fitoplanktonaren hazkuntza. Hori egiaztatuta zenetik, kontuan hartu da itsasoaren ponpa biologikoak atmosferako CO2-ren kontzentrazioa erregula dezakeela eta mundu mailako berotzea murrizteko geoingeniaritza moduan proposatu da burdinaren bidezko itsasoaren fertilizazioa. Baina emaitzak oso aldakorrak izan dira eta informazio gehiago behar da CO2-ren bahiketan burdinaren gehiketak izan dezakeen eraginkortasuna egiaztatzeko. Izan ere, aldakortasun biologikoak, geografikoak eta ozeanografikoak eragin handia dute. Eskala txikiko saioen bidez ezin da zehaztu zer gertatuko den fertilizazio osteko hamarkadetan edo areago, zer gertatuko den fertilizazio osteko mendean, Ozeano Antartiko osoa fertilizatzen badugu. Eredu ekologiko gehienek estimatzen dute burdinaren bidezko fertilizazioari esker urtero Gt karbono bat bahi daitekeela atmosferatik, baina oraingoz ez da guztiz ezagutzen zein izan daitekeen eragina hainbat kontutan: besteak beste zonalde hauetako eta elikagien azaleratze-lekuetako plankton komunitateen egituran, CO2 xurgatzeko gaitasunean, klimatologian, zonalde anoxikoen sorreran, biogasaren ekoizpenean edota azidifikazioan

Influence of age of aggregates and prokaryotic abundance on glucose and leucine uptake by heterotrophic marine prokaryotes

The kinetics of glucose and leucine uptake in attached and free-living prokaryotes in two types of microcosms with different nutrient qualities were compared. Microcosm type M1, derived from unaltered seawater, and microcosm type M2, from phytoplankton cultures, clearly expressed different kinetic parameters (Vmax/cell and K´m). In aggregates with low cell densities (M1 microcosm), the attached prokaryotes benefited from attachment as reflected in the higher potential uptake rates, while in aggregates with high cell densities (M2 microcosm) differences in the potential uptake rates of attached and free-living prokaryotes were not evident. The aging process and the chemical changes in aggregates of M2 microcosms were followed for 15–20 days. The results showed that as the aggregates aged and prokaryotic abundance increased, attached prokaryotes decreased their potential uptake rate and their K´m for substrate. This suggests an adaptive response by attached prokaryotes when aggregates undergo quantitative and qualitative impoverishment. [Int Microbiol 2007; 10(1):13-18

Prokaryotic capability to use organic substrates across the global tropical and subtropical ocean

Prokaryotes play a fundamental role in decomposing organic matter in the ocean, but little is known about how microbial metabolic capabilities vary at the global ocean scale and what are the drivers causing this variation. We aimed at obtaining the first global exploration of the functional capabilities of prokaryotes in the ocean, with emphasis on the under-sampled meso- and bathypelagic layers. We explored the potential utilization of 95 carbon sources with Biolog GN2 plates® in 441 prokaryotic communities sampled from surface to bathypelagic waters (down to 4,000 m) at 111 stations distributed across the tropical and subtropical Atlantic, Indian, and Pacific oceans. The resulting metabolic profiles were compared with biological and physico-chemical properties such as fluorescent dissolved organic matter (DOM) or temperature. The relative use of the individual substrates was remarkably consistent across oceanic regions and layers, and only the Equatorial Pacific Ocean showed a different metabolic structure. When grouping substrates by categories, we observed some vertical variations, such as an increased relative utilization of polymers in bathypelagic layers or a higher relative use of P-compounds or amino acids in the surface ocean. The increased relative use of polymers with depth, together with the increases in humic DOM, suggest that deep ocean communities have the capability to process complex DOM. Overall, the main identified driver of the metabolic structure of ocean prokaryotic communities was temperature. Our results represent the first global depiction of the potential use of a variety of carbon sources by prokaryotic communities across the tropical and the subtropical ocean and show that acetic acid clearly emerges as one of the most widely potentially used carbon sources in the ocean

Kinetic modulation of bacterial hydrolases by microbial community structure in coastal waters

In this study, we hypothesized that shifts in the kinetic parameters of extracellular hydrolytic enzymes may occur as a consequence of seasonal environmental disturbances and would reflect the level of adaptation of the bacterial community to the organic matter of the ecosystem. We measured the activities of enzymes that play a key role in the bacterial growth (leucine aminopeptidase, β- and α-glucosidases) in surface coastal waters of the Eastern Cantabrian Sea and determined their kinetic parameters by computing kinetic models of distinct complexity. Our results revealed the existence of two clearly distinct enzymatic systems operating at different substrate concentrations: a high-affinity system prevailing at low substrate concentrations and a low-affinity system characteristic of high substrate concentrations. These findings could be the result of distinct functional bacterial assemblages growing concurrently under sharp gradients of high-molecular-weight compounds. We constructed an ecological network based on contemporaneous and time-delayed correlations to explore the associations between the kinetic parameters and the environmental variables. The analysis revealed that the recurring phytoplankton blooms registered throughout the seasonal cycle trigger the wax and wane of those members of the bacterial community able to synthesize and secrete specific enzymes.his work has been supported by projects EFICIENCIA (CTM2006-08023) and CAMBIO (CTM2010-19308), co-financed by Ministry of Science and Innovation of the Spanish Government and European FEDER founds, the Basque Government (Grant to Research Group IT1657-22) and by the UPV/EHU (Grant to Research Group GIU10/17). Naiara Abad was supported by a scholarship from the Basque Government and currently by the grant Margarita Salas from the European Union—NextGenerationEU through the UPV/EHU. Zuriñe Baña and Ainhoa Uranga were financed by scholarships from the UPV/EHU

Burdinaren bidezko itsasoaren fertilizazioa klima-aldaketaren aurkako tresna interesgarria ote?

Berotegi efektuko gasak, batez ere CO2, atmosferan metatzerakoan mundu mailako beroketa gertatzen da. Erregai fosilen erreketatik askaturiko CO2 erdiak gutxi gorabehera atmosferan irauten du. Baina beste erdia lur-isurbideak eta batez ere ozeanoek xurgatzen dute. Itsasoan CO2-ren ziklo biogeokimikoa gertatzen da eta CO2 bahitu eta itsas hondoraino garraiatzen da edota CO2 askatzen da (itsas komunitateen arnasketaprozesuen bidez). Bi prozesu hauen arteko balantze netoa positiboa denez, itsasoa planetako karbonoaren erreserbagai handiena dugu. Karbonoaren garraioa ponpa fisikoak eta biologikoak egiten dute gainazaletik itsas hondoraino. Itsas hondoko CO2-ren emendioaren bi heren, fitoplanktonak, zooplanktonak, prokariotoek (bakterioek eta arkeoek) eta birusek osatzen duten ponpa biologikoari dagozkio. Fitoplanktona disolbaturiko elikagaiez eta karbono dioxidoz elikatzen da, eta CO2 materia organiko bihurtzen da fotosintesiaren bidez. Ekoizpen primario hau itsasoko zona fotikoan (lehenengo 100 metroetan) gertatzen da. Zooplanktonak eta prokariotoek bermineralizatzen dute fitoplanktonak askaturiko materia organiko gehiena baina gainontzekoa itsas hondorantz eraman eta han bahitzen da. Gainazaleko nitrato eta fosfatoen kontzentrazioak oso baxuak dira itsaso gehienetan, eta beraz, ponpa biologikoaren indarra elikagai hauen eskuragarritasunaren menpe dago. Baina, HNLC (High Nutrient Low Chlorophyll) zonaldeetan fitoplanktonaren hazkuntza ez dago elikagai hauen menpe, kontzentrazio handietan egon arren fitoplanktonaren hazkuntza txikia delako. John Martinek 1988an burdinaren hipotesia plazaratu zuenetik ("Give me a half tank of iron and I will give you an ice age"), burdinaren bidezko 12 fertilizazio saio egin dira Ozeano Antartikoko, Ozeano Artikoko edo Ozeano Bare ekuatorialeko HNLC zonaldeetan. Eskala txikiko eta epe motzeko saioak izan dira, non burdinaren fertilizazioa egin eta sulfato ferrikoaren kontzentrazio txikiak gehitzen diren. Saio hauek agerian utzi dute HNLC zonaldeetako burdinaren eskasiak mugatu egiten duela fitoplanktonaren hazkuntza. Hori egiaztatuta zenetik, kontuan hartu da itsasoaren ponpa biologikoak atmosferako CO2-ren kontzentrazioa erregula dezakeela eta mundu mailako berotzea murrizteko geoingeniaritza moduan proposatu da burdinaren bidezko itsasoaren fertilizazioa. Baina emaitzak oso aldakorrak izan dira eta informazio gehiago behar da CO2-ren bahiketan burdinaren gehiketak izan dezakeen eraginkortasuna egiaztatzeko. Izan ere, aldakortasun biologikoak, geografikoak eta ozeanografikoak eragin handia dute. Eskala txikiko saioen bidez ezin da zehaztu zer gertatuko den fertilizazio osteko hamarkadetan edo areago, zer gertatuko den fertilizazio osteko mendean, Ozeano Antartiko osoa fertilizatzen badugu. Eredu ekologiko gehienek estimatzen dute burdinaren bidezko fertilizazioari esker urtero Gt karbono bat bahi daitekeela atmosferatik, baina oraingoz ez da guztiz ezagutzen zein izan daitekeen eragina hainbat kontutan: besteak beste zonalde hauetako eta elikagien azaleratze-lekuetako plankton komunitateen egituran, CO2 xurgatzeko gaitasunean, klimatologian, zonalde anoxikoen sorreran, biogasaren ekoizpenean edota azidifikazioan

Functional diversity of bacterioplankton assemblages in the world's oceans

SAME13 - 13th Symposium on Aquatic microbial Ecology, 8-13 September 2013, Stresa, ItalyPeer Reviewe

Metabolic diversity of bacterioplankton in the ocean

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainBacterioplankton plays a key role in decomposing organic matter and recycling nutrients in the ocean, although still little is know on the metabolic abilities of bacterioplankton, and even less of bacteria living in the deep ocean. We tested the utilization of 95 carbon sources (belonging to the main categories: carbohydrates, amino acids, carboxylic acids) in the Atlantic, Indian and Pacific oceans in order to assess functional diversity of bacterioplankton in vertical profiles from surface to 4000 m. Samples were inoculated in the microplates, incubated in the dark at in situ temperature and the absorbance of the plates was measured. The results show a generally higher utilization of carbohydrates and amino acids in the upper layers of all the oceans, above 100m, with the highest values in the southern Pacific Ocean. The utilization of carbon sources in the deep ocean was generally lower, with the exception of an area in the equatorial Pacific OceanPeer Reviewe

Bacterial functional diversity in the Global Ocean

2nd International Ocean Research Conference, One planet one ocean, 17-21 November 2014, Barcelona, SpainBacterioplankton plays a key role in decomposing organic matter and recycling nutrients in the ocean. Although we have advanced in the last decades in the knowledge of the diversity of microbial communities, still little is know on the metabolic abilities of bacterioplankton, and even less of bacteria living in the deep ocean. During the circumnavigation expedition Malaspina we took samples in the Atlantic, Indic and Pacific oceans in order to assess functional diversity of bacterioplankton in vertical profiles from surface to 4,000 m. We tested the utilization of 95 carbon sources (belonging to the main categories: carbohydrates, amino acids, carboxylic acids) included in the Biolog plates, and 8 additional sources selected by their relevance in marine environments. Samples were inoculated in the microplates, incubated in the dark at in situ temperature and the absorbance of the plates was measured. The results show a generally higher utilization of carbohydrates and amino acids in the upper layers of all the oceans, above 100m, with the highest values in the southern Pacific Ocean. The utilization of carbon sources in the deep ocean was lower, with the exception of an area in the southern Pacific Ocean where utilization of carbohydrates, amino acids and carboxylic acids at 4000m exceeded even that found in upper layers of the oceanPeer Reviewe