Biogeochemical Modelling

Mesoscale eddies in the south west Pacific region are prominent ocean features that represent distinctive environments for phytoplankton. Here, we examine the seasonal plankton dynamics associated with averaged cyclonic and anticyclonic eddies (CE and ACE, respectively) off eastern Australia. We do this through building seasonal climatologies of mixed layer depth (MLD) and surface chlorophyll-a for both CE and ACE by combining remotely sensed sea surface height (TOPEX/Poseidon, Envisat, Jason-1, and OSTM/Jason-2), remotely sensed ocean color (GlobColour) and in situ profiles of temperature, salinity and pressure from Argo floats. Using the CE and ACE seasonal climatologies, we assimilate the surface chlorophyll-a data into both a single (WOMBAT), and multi-phytoplankton class (EMS) biogeochemical model to investigate the level of complexity required to simulate the phytoplankton chlorophyll-a. For the two eddy types, the data assimilation showed both biogeochemical models only needed one set of parameters to represent phytoplankton but needed different parameters for zooplankton. To assess the simulated phytoplankton behavior we compared EMS model simulations with a ship-based experiment that involved incubating a winter phytoplankton community sampled from below the mixed layer under ambient and two higher light intensities with and without nutrient enrichment. By the end of the 5-day field experiment, large diatom abundance was four times greater in all treatments compared to the initial community, with a corresponding decline in pico-cyanobacteria. The experimental results were consistent with the simulated behavior in CE and ACE, where the seasonal deepening of the mixed layer during winter produced a rapid increase in large phytoplankton. Our model simulations suggest that CE off East Australia are not only characterized by a higher chlorophyll-a concentration compared to ACE, but also by a higher concentration of large phytoplankton (i.e., diatoms) due to the shallower CE mixed layer. The model simulations also suggest the zooplankton community is different in the two eddy types and this behavior needs further investigation.

h i g h l i g h t s • The BFM-POM 1D system successfully replicated the observed seasonal variability. • The microbial food web dominates the Gulf of Trieste trophic structure. • External inputs variability can change the trophic web structure. • A first step for developing a modelling system supporting environmental management.

Process-based models are useful for assessing the impact of changing management practices and climate on yields and greenhouse gas (GHG) emissions from agricultural systems such as grasslands. They can be used to construct national GHG inventories using a Tier 3 approach. However, accurate simulations of nitrous oxide (N 2 O) fluxes remain challenging. Models are limited by our understanding of soil-plant-microbe interactions and the impact of uncertainty in measured input parameters on simulated outputs. To improve model performance, thorough evaluations against in situ measurements are needed. Experimental data of N 2 O emissions under two management practices (control with typical fertilization versus increased clover and no fertilization) were acquired in a Swiss field experiment. We conducted a multimodel evaluation with three commonly used biogeochemical models (DayCent in two variants, PaSim, APSIM in two variants) comparing four years of data. DayCent was the most accurate model for simulating N 2 O fluxes on annual timescales, while APSIM was most accurate for daily N 2 O fluxes. The multimodel ensemble average reduced the error in estimated annual fluxes by 41% compared to an estimate using the Intergovernmental Panel on Climate Change (IPCC)-derived method for the Swiss agricultural GHG inventory (IPCC-Swiss), but individual models were not systematically more accurate than IPCC-Swiss. The model ensemble overestimated the N 2 O mitigation effect of the clover-based treatment (measured: 39-45%; ensemble: 52-57%) but was more accurate than IPCC-Swiss (IPCC-Swiss: 72-81%). These results suggest that multimodel ensembles are valuable for estimating the impact of climate and management on N 2 O emissions. Plain Language Summary We tested the performance of three dynamic simulation models against measured nitrous oxide (N 2 O) fluxes and its driver variables for a Swiss grassland. We showed that DayCent performed best in the prediction of annual N 2 O emissions but was outperformed by APSIM for daily N 2 O emissions. We identified particular strengths and weaknesses of each model. Further, we compared the individual models against the N 2 O flux estimate made with the Intergovernmental Panel on Climate Change (IPCC)-derived method for the Swiss agricultural greenhouse gas inventory (IPCC-Swiss). Most individual models were worse than IPCC-Swiss but the mean of all model predictions was much better than IPCC-Swiss. All methods overestimated the N 2 O mitigation effect of a clover-based N 2 O mitigation. IPCC-Swiss was worst and the model ensemble was best at estimating the effects of the mitigation. The findings highlight that using multiple models in an ensemble is beneficial for assessing management and climate impacts on N 2 O emissions.

The Cretaceous 'greenhouse' period (~145 to ~65 million years ago, Ma) in Earth's history is relatively well documented by multiple paleo proxy records, which indicate that the meridional sea surface temperature (SST) gradient increased (non-monotonically) from the Valanginian (~135 Ma) to the Maastrichtian (~68 Ma). Changes in atmospheric CO2 concentration, solar constant, and paleogeography are the primary drivers of variations in the spatiotemporal distribution of SST, which plays a key role in the evolution of the rich biodiversity that persisted during the Cretaceous. However, the particular contribution of each of these drivers (and their underlying mechanisms) to changes in the SST distribution remains poorly understood. Here we use data from a suite of paleoclimate simulations to show that atmospheric CO2 fluctuations and paleogeographic changes have a comparable effect on mid-latitudinal SST gradient through the Cretaceous. Further, we use a fundamental model of wind-driven ocean gyres to quantify how changes in the northern hemisphere paleogeography drive a reduction in the meridional oceanic heat transport, leading to an increase in extratropical SSTs. This reduction in heat transport results from a weakening of the subtropical ocean gyres, caused by a decrease in the ratio of meridional to zonal extent of the 'gyral basin'.

The Cretaceous 'greenhouse' period (~145 to ~65 million years ago, Ma) in Earth's history is relatively well documented by multiple paleo proxy records, which indicate that the meridional sea surface temperature (SST) gradient increased (non-monotonically) from the Valanginian (~135 Ma) to the Maastrichtian (~68 Ma). Changes in atmospheric CO2 concentration, solar constant, and paleogeography are the primary drivers of variations in the spatiotemporal distribution of SST, which plays a key role in the evolution of the rich biodiversity that persisted during the Cretaceous. However, the particular contribution of each of these drivers (and their underlying mechanisms) to changes in the SST distribution remains poorly understood. Here we use data from a suite of paleoclimate simulations to show that atmospheric CO2 fluctuations and paleogeographic changes have a comparable effect on mid-latitudinal SST gradient through the Cretaceous. Further, we use a fundamental model of wind-driven ocean gyres to quantify how changes in the northern hemisphere paleogeography drive a reduction in the meridional oceanic heat transport, leading to an increase in extratropical SSTs. This reduction in heat transport results from a weakening of the subtropical ocean gyres, caused by a decrease in the ratio of meridional to zonal extent of the 'gyral basin'.

Zooplankton biomass data have been collected in Australian waters since the 1930s, yet most datasets have been unavailable to the research community. We have searched archives, scanned the primary and grey literature, and contacted researchers, to collate 49187 records of marine zooplankton biomass from waters around Australia (0-60°S, 110-160°E). Many of these datasets are relatively small, but when combined, they provide >85 years of zooplankton biomass data for Australian waters from 1932 to the present. Data have been standardised and all available metadata included. We have lodged this dataset with the australian Ocean Data Network, allowing full public access. the australian Zooplankton Biomass Database will be valuable for global change studies, research assessing trophic linkages, and for initialising and assessing biogeochemical and ecosystem models of lower trophic levels.

 A new method for quantifying mesoscale and submesoscale contributions to high sea surface chlorophyll concentrations is developed  The contribution of submesoscale processes to high chlorophyll is comparable to that of mesoscale eddies in subtropical gyres worldwide

The systematic literature search on the fertility rate was performed on articles from the Web of Science compiled by the Institute of Scientific Information (ISI) to provide major publication characteristics. All articles related to Fertility from year 1980 to 2011 were analyzed with the bibliometric approach using non-parametrics techniques. Total Citation, Citation per year and Cited References were significantly different between the 80’s, 90’s and 2000’s, with more than a 100% increase in the number of publication. The association between number of authors and citation per year were significantly weak. Number of publication in a journal posed a poor negative association with the citation per year. Similarity between Authors Keyword and KeyWords Plus® do not promote the increase in citation per year. The author’s affiliation and country of publication would be an interesting exploration for future fertility research. The bibiliometric analyses on Fertility is rather new and vital...

h i g h l i g h t s • The BFM-POM 1D system successfully replicated the observed seasonal variability. • The microbial food web dominates the Gulf of Trieste trophic structure. • External inputs variability can change the trophic web structure. • A first step for developing a modelling system supporting environmental management.

Matsuno, K., Yamaguchi, A., and Imai, I. 2012. Biomass size spectra of mesozooplankton in the Chukchi Sea during the summers of 1991/1992 and 2007/2008: an analysis using optical plankton counter data. – ICES Journal of Marine Science, 69: . An optical plankton counter was used to examine the regional characteristics of the zooplankton communities in the Chukchi Sea during the summers of 1991, 1992, 2007, and 2008. Zooplankton abundance and biomass ranged from 5000 to 1 170 000 ind. m−2 and 0.2 to 10.9 g dry mass m−2, respectively. Based on zooplankton biovolume in equivalent spherical diameter (ESD) in 48 bins, one every 0.1 mm between 0.25 and 5.0 mm, a Bray–Curtis cluster analysis classified zooplankton communities into four groups (A–D). No changes were observed in zooplankton communities south of the Lisburne Peninsula (group A) throughout the 4 years, but there were differences north of the Peninsula, with group B (normal, intermediate biomass) observed in 1991/1992, group D (...

Many recent studies have focused on how climate variability affects crop production and yields, however, little is known about the effects of climate variability on nitrogen (N) loss despite the necessity of mitigating N loss for sustainable agroecosystems. By using the DeNitrification and DeComposition (DNDC) model and measurements collected from two management systems (conventional (CV) and best management (BM)) from 2000 to 2004), our objective was to evaluate N losses under different climate scenarios. Our modelled results support the conclusions from previous work that reductions in N losses were obtained by implementing BM rather than CV management. Under numerous climate scenarios (n = 25), greater variation was observed in the CV system compared to the BM system for total N losses accumulated over the 5-yr period and for N lost during each year of the crop sequence. Regardless of the management system, the most dominant N loss pathway was NO 3 À leaching, followed by NH 3 volatilization, and N 2 O emissions. The BM system reduced the frequency of total N loss events compared to CV system, yet, the capacity of the BM system to reduce the frequency of major NO 3 À events (>1 kg d À1) was reduced under a high N loss scenario compared to a low N loss scenario. Higher losses were associated with higher daily temperatures, greater total precipitation, more frequent and intense precipitation events. Thus, the effectiveness of BM systems in controlling major N loss events via NO 3 À leaching may decrease in the future as a more variable climate ensues with intense precipitation events. Overall, the effect of management remained greater than the impact of climate in determining accumulated N loss over long-term periods, which emphasizes the importance of implementing conservation practices to control N losses. 2016 Elsevier B.V. All rights reserved.

h i g h l i g h t s • The BFM-POM 1D system successfully replicated the observed seasonal variability. • The microbial food web dominates the Gulf of Trieste trophic structure. • External inputs variability can change the trophic web structure. • A first step for developing a modelling system supporting environmental management.

The systematic literature search on the fertility rate was performed on articles from the Web of Science compiled by the Institute of Scientific Information (ISI) to provide major publication characteristics. All articles related to Fertility from year 1980 to 2011 were analyzed with the bibliometric approach using non-parametrics techniques. Total Citation, Citation per year and Cited References were significantly different between the 80’s, 90’s and 2000’s, with more than a 100% increase in the number of publication. The association between number of authors and citation per year were significantly weak. Number of publication in a journal posed a poor negative association with the citation per year. Similarity between Authors Keyword and KeyWords Plus® do not promote the increase in citation per year. The author’s affiliation and country of publication would be an interesting exploration for future fertility research. The bibiliometric analyses on Fertility is rather new and vital...

Cobalt is an important micronutrient for ocean microbes as it is present in vitamin B and is a co-factor in various metalloenzymes that catalyze cellular processes. Moreover, when seawater availability of cobalt is compared to biological demands, cobalt emerges as being depleted in seawater, pointing to a potentially important limiting role. To properly account for the potential biological role for cobalt, there is therefore a need to understand the processes driving the biogeochemical cycling of cobalt and, in particular, the balance between external inputs and internal cycling. To do so, we developed the first cobalt model within a state-of-the-art three-dimensional global ocean biogeochemical model. Overall, our model does a good job in reproducing measurements with a correlation coefficient of >0.7 in the surface and >0.5 at depth. We find that continental margins are the dominant source of cobalt, with a crucial role played by supply under low bottom-water oxygen conditio...

In the past few years, soft computing techniques, such as fuzzy logic, neural networks and cellular automata that are capable of handling the uncertainty in data and analysis have been used in ecosystem modelling. Fuzzy logic can be used to model non-linear relationships easily and effectively even when only limited data is available. Hence it is possible to construct a fuzzy model based on the known relationships between water quality parameters and the Chlorophyll-a pigment in lagoon waters to obtain the trophic status using the available dataset. Thus in the present study, standard fuzzy relationships in the form of the fuzzy intersection, were constructed to determine the combined acceptability of chlorophyll-a concentration (as primary productivity), as the lowest of the partial acceptabilities of six major influencing variableswater temperature, secchi disk depth, salinity, dissolved oxygen, total nitrogen, total phosphorus in the water-as an indicator of the trophic status of the lagoon in the years 2005 and 2006. The results obtained from the present study showed that Pulicat lagoon was oligotrophic during the post monsoon and premonsoon periods of 2005, slightly eutrophic in summer of 2005 and mesotrophic during the monsoon periods. The trend was observed to be similar during 2006, excluding the premonsoon period which exhibited oligotrophic condition in the 2006. Evaluation of the performance of the newly created fuzzy model implied that the indices derived using the present method were good representations of the observed actual field conditions.

The Cenomanian-Turonian oceanic anoxic event (OAE2) is characterized by large perturbations in the oxygen and sulfur cycles of the ocean, potentially resulting from changes in oxygen supply (via oxygen solubility and ocean circulation) and in marine productivity. We assess the relative impact of these mechanisms, comparing model experiments with a new compilation of observations for seafloor dysoxia/anoxia and photic zone euxinia. The model employed is an intermediate-complexity Earth system model which accounts for the main ocean dynamics and biogeochemistry of the Cretaceous climate. The impact of higher temperature and marine productivity is evaluated in the model as a result of higher atmospheric carbon dioxide and oceanic nutrient concentrations. The model shows that temperature is not alone able to reproduce the observed patterns of oceanic redox changes associated with OAE2. Observations are reproduced in the model mainly via enhanced marine productivity due to higher nutrient content (responsible for 85% of the change). Higher phosphate content could have been sustained by increased chemical weathering and phosphorus regeneration from anoxic sediments, which in turn induced an enhanced nitrogen nutrient content of the ocean via nitrogen fixation. The model also shows that the presence of seafloor anoxia, as suggested by black-shale deposition in the proto-North Atlantic Ocean before the event, might be the result of the silled shape and lack of deep-water formation of this basin at the Late Cretaceous. Overall our model-data comparison shows that OAE2 anoxia was quasi-global spreading from 5% of the ocean volume before the event to at least 50% during OAE2.

The Cenomanian-Turonian oceanic anoxic event (OAE2) is characterized by large perturbations in the oxygen and sulfur cycles of the ocean, potentially resulting from changes in oxygen supply (via oxygen solubility and ocean circulation) and in marine productivity. We assess the relative impact of these mechanisms, comparing model experiments with a new compilation of observations for seafloor dysoxia/anoxia and photic-zone euxinia. The model employed is an intermediate-complexity Earth system model which accounts for the main ocean dynamics and biogeochemistry of the Cretaceous climate. The impact of higher temperature and marine productivity is evaluated in the model as a result of higher atmospheric carbon dioxide and oceanic nutrient concentrations. The model shows that temperature is not alone able to reproduce the observed patterns of oceanic redox changes associated with OAE2. Observations are reproduced in the model mainly via enhanced marine productivity due to higher nutrien...

The global carbon cycle during the mid-Cretaceous ($125-88 million years ago, Ma) experienced numerous major perturbations linked to increased organic carbon burial under widespread, possibly basin-scale oxygen deficiency and episodes of euxinia (anoxic and H 2 S-containing). The largest of these episodes, the Cenomanian-Turonian boundary event (ca. 93.5 Ma), or oceanic anoxic event (OAE) 2, was marked by pervasive deposition of organic-rich, laminated black shales in deep waters and in some cases across continental shelves. This deposition is recorded in a pronounced positive carbon isotope excursion seen ubiquitously in carbonates and organic matter. Enrichments of redox-sensitive, often bioessential trace metals, including Fe and Mo, indicate major shifts in their biogeochemical cycles under reducing conditions that may be linked to changes in primary production. Iron enrichments and bulk Fe isotope compositions track the sources and sinks of Fe in the proto-North Atlantic at seven localities marked by diverse depositional conditions. Included are an ancestral mid-ocean ridge and euxinic, intermittently euxinic, and oxic settings across varying paleodepths throughout the basin. These data yield evidence for a reactive Fe shuttle that likely delivered Fe from the shallow shelf to the deep ocean basin, as well as (1) hydrothermal sources enhanced by accelerated seafloor spreading or emplacement of large igneous province(s) and (2) local-scale Fe remobilization within the sediment column. This study, the first to explore Fe cycling and enrichment patterns on an ocean scale using iron isotope data, demonstrates the complex processes operating on this scale that can mask simple source-sink relationships. The data imply that the proto-North Atlantic received elevated Fe inputs from several sources (e.g., hydrothermal, shuttle and detrital inputs) and that the redox state of the basin was not exclusively euxinic, suggesting previously unknown heterogeneity in depositional conditions and biogeochemical cycling within those settings during OAE-2.

An analysis of orbitally influenced climate-sensitive sedimentation is conducted across a meridional transect of the proto-North Atlantic, to reconstruct the behavior of the carbon cycle and climate during Oceanic Anoxic Event 2 (OAE 2; $94 Ma). Midlatitude to near equatorial sites spanning deep-ocean to shelf environments are evaluated using a new inverse method for the identification and calibration of orbital influence in ancient strata. The results yield consistent independent astrochronologies at each location-compatible with the recently published radioisotopic/astrochronologic time scale at the Cenomanian-Turonian GSSP-and thus provide a unified high-resolution temporal context for evaluation of the event. The proto-North Atlantic astrochronologies document an amplification of obliquity power during OAE 2, indicating that obliquity was the dominant pacemaker of organic matter accumulation by the latter portion of the event. The strong obliquity signal suggests an influence of high-latitude climate processes across midlatitude deep-ocean to tropical shelf environments. Changes in oceanic circulation during OAE 2 represent a likely mechanism for the propagation of a high latitude signal, and proxy data from Demerara Rise reveal the development of a new intermediate water mass source synchronous with the record of obliquity amplification. We hypothesize that a dense high-latitude water mass displaced a pre-existing nutrient-rich anoxic deep-water layer in the proto-North Atlantic (augmented by enhanced volcanism), driving an episode of high productivity that lasted 700-800 ka. The development and intensification of the new intermediate/deep water source was potentially driven by eustatic sea level rise, which created expansive seaways in mid to high latitudes.

Oceanic anoxic events (OAEs) document major perturbations of the global carbon cycle with repercussions for the Earth's climate and ocean circulation that are relevant to understanding future climate trends. Here, we compare the onset and development of Cretaceous OAE1a and OAE2 in two drill cores with unusually high sedimentation rates from the Vocontian Basin (southern France) and Tarfaya Basin (southern Morocco). OAE1a and OAE2 exhibit remarkable similarities in the evolution of their carbon isotope (δ 13 C) records, with long-lasting negative excursions preceding the onset of the main positive excursions, supporting the view that both OAEs were triggered by massive emissions of volcanic CO 2 into the atmosphere. However, there are substantial differences, notably in the durations of individual phases within the δ 13 C positive excursions of both OAEs. Based on analysis of cyclic sediment variations, we estimate the duration of individual phases within OAE1a and OAE2. We identify (1) a precursor phase (negative excursion) lasting ∼ 430 kyr for OAE1a and ∼ 130 kyr for OAE2, (2) an onset phase of ∼ 390 and ∼ 70 kyr, (3) a peak phase of ∼ 600 and ∼ 90 kyr, (4) a plateau phase of ∼ 1340 and ∼ 200 kyr, and (5) a recovery phase of ∼ 380 and ∼ 440 kyr. The total duration of the positive δ 13 C excursion is estimated at 2700 kyr for OAE1a and 790 kyr for OAE2, and that of the main carbon accumulation phase is estimated at 980 and 180 kyr. The long-lasting peak, plateau and recovery phases imply fundamental changes in global nutrient cycles either (1) by submarine basalt-seawater interactions, (2) through excess nutrient inputs to the oceans by increasing continental weathering and river discharge, or (3) through nutrient recycling from the marine sediment reservoir. We investigated the role of phosphorus in the development of carbon accumulation by analysing phosphorus speciation across OAE2 and the mid-Cenomanian Event (MCE) in the Tarfaya Basin. The ratios of organic carbon and total nitrogen to reactive phosphorus (C org /P react and N total /P react) prior to OAE2 and the MCE hover close to or below the Redfield ratio characteristic of marine organic matter. Decreases in reactive phosphorus resulting in C org /P react and N total /P react above the Redfield ratio during the later phase of OAE2 and the MCE indicate leakage from the sedimentary column into the water column under the influence of intensified and expanded oxygen minimum zones. These results suggest that a positive feedback loop, rooted in the benthic phosphorus cycle, contributed to increased marine productivity and carbon burial over an extended period of time during OAEs.

The systematic literature search on the fertility rate was performed on articles from the Web of Science compiled by the Institute of Scientific Information (ISI) to provide major publication characteristics. All articles related to Fertility from year 1980 to 2011 were analyzed with the bibliometric approach using non-parametrics techniques. Total Citation, Citation per year and Cited References were significantly different between the 80's, 90's and 2000's, with more than a 100% increase in the number of publication. The association between number of authors and citation per year were significantly weak. Number of publication in a journal posed a poor negative association with the citation per year. Similarity between Authors Keyword and KeyWords Plus® do not promote the increase in citation per year. The author's affiliation and country of publication would be an interesting exploration for future fertility research. The bibiliometric analyses on Fertility is rath...

Linking lower to higher trophic levels requires a special focus on the pivotal role played by mid-trophic levels, i.e. the zooplankton. One of the most relevant information on zooplankton in term of fluxes of matter lies in its size structure. We present here an extensive dataset of size measurements covering part of the western European shelf and slope, from the Galician coast to the Ushant front, during springs from 2005 to 2012. Zooplankton size spectra were estimated using both measurements carried out in situ by the Laser-Optical Plankton Counter (LOPC, 816 records) and WP2 net (200 μm mesh size) samples scanned following the ZooScan methodology and image analysis (a total of 89 samples were analyzed). The LOPC counts and sizes all particles in the range 100 to 2000 μm of spherical equivalent diameter (ESD) whereas the WP2/ZooScan allows the counting, sizing and identification of zooplankton from ~400 μm ESD. The difference between the LOPC (all particles) and the WP2/ZooSca...

Oceanic anoxic event 2 (OAE2), which occurred during the Cenomanian-Turonian (C-T) transition and lasted 1 m.y., is characterized by a positive global carbon isotopic excursion and stepwise extinctions in marine biota. To examine temporal variations in the dissolved oxygen content of the water column, shallow-marine C-T sediments from northern Spain were ana

The geological record provides evidence for the periodic occurrence of water column anoxia and formation of organic-rich deposits in the North Atlantic Ocean during the mid-Cretaceous (hereafter called proto-North Atlantic). Both changes in primary productivity and oceanic circulation likely played a role in the development of the low oxy-5 25 is difficult to achieve in the model. This suggests that the ocean circulation used in the model may be too vigorous and/or that anoxia in the proto-North Atlantic was less widespread than previously thought.

The Late Cretaceous Oceanic Anoxic Event 2 (OAE2; ca. 94 Ma) was one of the largest global carbon cycle perturbations during the Phanerozoic. OAE2 represents an important, although extreme, case study for modern trends because widespread anoxia and enhanced organic carbon burial during OAE2 were linked to exceptionally warm climates and high atmospheric CO 2 concentrations. However, the consequences of this warmth for the hydrological cycle remain poorly understood, hampering our understanding of its impact on biogeochemical cycles during this greenhouse episode. Here we show evidence for changes in the hydrological cycle during OAE2 based on combined geochemical and palynological data for the stratigraphically expanded coastal OAE2 succession at Bass River, located on the New Jersey shelf (Ocean Drilling Program Leg 174AX), eastern United States. Paleothermometry, based on TEX 86 , indicates sea-surface warming at the onset of OAE2 and a subsequent pronounced cooling event. Palynological data show that these changes in temperature were associated with strong variations in precipitation and runoff. We suggest that an acceleration of the hydrological cycle during OAE2 played a key role in supplying nutrients to coastal waters and enhancing stratifi cation, thus contributing to the development of ocean anoxia.

PEMBAHASAN Natural selection and culture variationInteraction Julian StewardCulture ecology as means to introduce you to some of the main issues in applyingecological and evolutionary ideas to human(Budaya ekologi adalah sebagai sarana untuk memperkenalkan anda untukbeberapa isu utama dalam menerapkan ekologi dan evolusi ide-ide untuk manusia)Technology : Penghetahuan PendudukSocial Structure : Paling Sederhana1. Keluarga2. Rt3. KelurahanPolulation density : Kepadatan Penduduk .

RANGKUMAN Ilmu lingkungan adalah kajian tentang apa yang harus dilakukan oleh manusia untuk mengelola lingkungan hidup sesuai fungsi dan perannya. Ilmu itu secara filosofis harus memiliki 3 ciri, yang pertama Ontologis yang berfungsi untuk menjawab pertanyaan apa, yang kedua Epistemologis yang berfungsi untuk menjawab pertanyaan bagaimana, dan yang ketiga itu Aksiologis yang berfungsi untuk menjawab

Cretaceous oceanic anoxic event 2 (OAE2) is thought to have been contemporary with extensive volcanism and the release of large quantities of volcanic CO 2 capable of triggering marine anoxia through a series of biogeochemical feedbacks. High-resolution reconstructions of atmospheric CO 2 concentrations across the initiation of OAE2 suggest that there were also two distinct pulses of CO 2 drawdown coeval with increased organic carbon burial. These fluctuations in CO 2 likely led to significant climatic changes, including fluctuations in temperatures and the hydrological cycle. Paleofire proxy records suggest that wildfire was a common occurrence throughout the Cretaceous Period, likely fueled by the estimated high atmospheric O 2 concentrations at this time. However, over geological time scales, the likelihood and behavior of fire are also controlled by other factors such as climate, implying that CO 2-driven climate changes should also be observable in the fossil charcoal record. We tested this hypothesis and present a high-resolution study of fire history through the use of fossil charcoal abundances across the OAE2 onset, and we compared our records to the estimated CO 2 fluctuations published from the same study sites. Our study illustrates that inferred wildfire activity appears to relate to changes in CO 2 occurring across the onset of OAE2, where periods of CO 2 drawdown may have enabled an increase in fire activity through suppression of the hydrological cycle. Our study provides further insight into the relationships between rapid changes in the carbon cycle, climate, and wildfire activity, illustrating that CO 2 and climate changes related to inferred wildfire activity can be detected despite the estimated high Cretaceous atmospheric O 2 concentrations.

Cobalt is an important micronutrient for ocean microbes as it is present in vitamin B 12 and is a co-factor in various metalloenzymes that catalyze cellular processes. Moreover, when seawater availability of cobalt is compared to biological demands, cobalt emerges as being depleted in seawater, pointing to a potentially important limiting role. To properly account for the potential biological role for cobalt, there is therefore a need to understand the processes driving the biogeochemical cycling of cobalt and, in particular, the balance between external inputs and internal cycling. To do so, we developed the first cobalt model within a state-of-the-art three-dimensional global ocean biogeochemical model. Overall, our model does a good job in reproducing measurements with a correlation coefficient of >0.7 in the surface and >0.5 at depth. We find that continental margins are the dominant source of cobalt, with a crucial role played by supply under low bottom-water oxygen conditions. The basin-scale distribution of cobalt supplied from margins is facilitated by the activity of manganese-oxidizing bacteria being suppressed under low oxygen and low temperatures, which extends the residence time of cobalt. Overall, we find a residence time of 7 and 250 years in the upper 250 m and global ocean, respectively. Importantly, we find that the dominant internal resupply process switches from regeneration and recycling of particulate cobalt to dissolution of scavenged cobalt between the upper ocean and the ocean interior. Our model highlights key regions of the ocean where biological activity may be most sensitive to cobalt availability. Plain Language Summary Biological activity in the sea requires cobalt, primarily due to its role in vitamin B12 but also because it is required in other cellular enzymes. While our observations of cobalt distributions in the ocean is growing, we do not have a quantitative understanding of the role of different external sources of cobalt or how it is internally processed by different biological and chemical processes in the ocean. To answer these questions, we built the first ever global ocean cobalt model that coupled the cycling of cobalt to the major biogeochemical processes occurring in the ocean. Using this model, we identified that sediments are the major cobalt source and that the combination of oxygen levels and scavenging removal by bacteria allow externally supplied cobalt to pervade the ocean as a whole. We find that in certain regions of the upper ocean, cobalt levels may be low enough to affect biological activity but that to quantify this requires further work on how we represent cellular biochemistry.