Chemical Oceanography

Insects  comprise  the  most  diverse  group  of  multicellular  organisms  in  the  planet  Earth,  which  provide  several  ecosystem  services like pollination, pest control (bio-control), decomposition, transference of energy through food chain etc. In addition, insects are  widely  used  today  as  human  edible  items  and  ingredients  of  fish-feed, turtle-feed, livestock, etc. In this paper we focus on the vital ecosystem services provided by insects with special reference to  their  services  in  the  domain  of  human  food.  Our  research  stands  on  the  high  nutritional  value  of  insects  preferably  protein  which  ranges  between  13%  -  77%.  Our  paper  has  two-fold  goals  namely  documentation  of  selective  ecosystem  services  of  insects  and  highlighting  the  edible  value  of  insects.  In  this  paper  we  have  intentionally excluded the value of commercially produced insect-derived products like honey, wax, silk, shellac, etc. rather our main focus  is  to  highlight  the  nutritional  value  of  insects  which  is  the  most demanding subject to feed the rapidly rising population in the present world. Insects  play  an  important  role  in  the  reproduction  of  plant  species. About one lakh pollinator species have been identified out of which 98% are insects [1]. Over 90% of two lakh fifty thousand flowering plant species depend on pollinators. This is applicable for 75% of the hundred crop species that generate most of the worlds’ food grain.

To clarify the sources and biogeochemical dynamics of dissolved methane (CH 4) in shallow-water coastal oceans, we investigated the concentrations, sea-to-air fluxes, and net cycling rate of CH 4 in the central Bohai Sea in summer 2018. During the survey, both summertime stratification and dissolved oxygen (DO) deficit were observed. In the surface layer, CH 4 concentration ([CH 4 ]) ranged from 3.08 to 10.27 nmol kg −1. The average sea-to-air flux was estimated at 6.46 ± 3.32 µmol m −2 d −1 , indicating that the Bohai Sea serves as a source of atmospheric CH 4. In the bottom layer, [CH 4 ] ranged from 4.29 to 31.04 nmol kg −1. The downward increase in [CH 4 ] within the water column indicated substantial sources of CH 4 in the seafloor. Based on the complex relationship between the saturation ratio of CH 4 and DO, three types of CH 4 release from the seafloor were identified, including diagenesis of buried organic matter, natural leakage from geological settings, and anthropogenic release from offshore oil/gas development. The saturation ratios of CH 4 in bottom waters were positively correlated with the degree of stratification of the water column. Using a two-layer box model, sedimentary CH 4 release rates at two oxygen-deficient stations were estimated to be 56.0-60.8 µmol m −2 d −1 , which was much higher than the sea-to-air fluxes. The modeling results also indicated that the majority of seafloor released CH 4 (>90%) was consumed in the water column of this shallow-water coastal sea. This is the first comprehensive study on CH 4 cycling in the Bohai Sea. This work shows the indicative role of DO in identifying multiple CH 4 sources and highlights the dominance of water stratification and microbial consumption in local CH 4 dynamics. KEY POINTS-Dissolved CH 4 exhibited complex relations with oxygen in the Bohai Sea.-Three types of CH 4 sources from seafloor were identified.-Stratification hampered the upward transport of dissolved CH 4 .-Strengths of CH 4 cycling terms are quantified.

Environmental context.Polyfluorinated compounds are an emerging group of organic pollutants that are globally distributed in urban and natural environments. Reliable air monitoring methods are crucial to our understanding of how these pollutants are released to, and transported in, the atmosphere. This intercomparison study, involving laboratories that investigate polyfluorinated compounds in air, uncovers inconsistencies in the reported data, and highlights necessary analytical improvements for future research projects. .Fluorotelomer alcohols, perfluorinated sulfonamides or sulfonamido ethanols are volatile precursors of persistent perfluorinated acids. Published air-sampling strategies and analytical methods to determine these compounds differ. To assess performance on the determination of airborne polyfluorinated compounds, an intercomparison comprising four international research groups was established. Instrumental and analytical comparability between laboratories varied depen...

The present study deals with the physical and chemical characteristics of the water of the Suez Canal. Water temperature, total suspended solid (TSS), pH, salinity, OOM, DO and BOD as well as NH 4 ; NO 2-, NO 3-, and PO 4 3-were me a s u r e d seasonally

Application of in situ membrane introduction mass spectrometry (MIMS) to quantification of aqueous chemicals was evaluated in the laboratory and the field. Laboratory experiments were performed to examine the influence of sampling parameters on mass-resolved time-series data. Results were applied to field data to quantify concentrations in a chemical plume. ª

Environmental context Arsenic concentrations and species were determined in seagrass ecosystems where the food web was established using carbon and nitrogen isotopes. There was a clear increase in the proportion of arsenobetaine in tissues of higher trophic level organisms, which is attributed to an increasing arsenobetaine content of the diet and the more efficient assimilation and retention of arsenobetaine over other arsenic species. The results provide an explanation for the prominence of arsenobetaine in higher marine animals. Arsenic concentrations and species were compared in biota from two Zostera capricorni ecosystems. Mean arsenic concentrations were not significantly different for non‐vegetative sediment, rhizosphere sediment, Z. capricorni blades, roots, rhizomes, epiphytes, amphipods, polychaetes, molluscs, crustaceans and fish, but were significantly different in detritus. Sediments and plant tissues contained mostly inorganic arsenic and PO4–arsenoriboside. Detritus c...

Enhanced release of alkalinity from the seafloor, principally driven by anaerobic degradation of organic matter under low-oxygen conditions and associated secondary redox reactions, can increase the carbon dioxide (CO2) buffering capacity of seawater and therefore oceanic CO2 uptake. The Baltic Sea has undergone severe changes in oxygenation state and total alkalinity (TA) over the past decades. The link between these concurrent changes has not yet been investigated in detail. A recent system-wide TA budget constructed for the past 50 years using BALTSEM, a coupled physical–biogeochemical model for the whole Baltic Sea area revealed an unknown TA source. Here we use BALTSEM in combination with observational data and one-dimensional reactive-transport modeling of sedimentary processes in the Fårö Deep, a deep Baltic Sea basin, to test whether sulfate (SO42−) reduction coupled to iron (Fe) sulfide burial can explain the missing TA source in the Baltic Proper. We calculated that this burial can account for up to 26 % of the missing source in this basin, with the remaining TA possibly originating from unknown river inputs or submarine groundwater discharge. We also show that temporal variability in the input of Fe to the sediments since the 1970s drives changes in sulfur (S) burial in the Fårö Deep, suggesting that Fe availability is the ultimate limiting factor for TA generation under anoxic conditions. The implementation of projected climate change and two nutrient load scenarios for the 21st century in BALTSEM shows that reducing nutrient loads will improve deep water oxygen conditions, but at the expense of lower surface water TA concentrations, CO2 buffering capacities and faster acidification. When these changes additionally lead to a decrease in Fe inputs to the sediment of the deep basins, anaerobic TA generation will be reduced even further, thus exacerbating acidification. This work highlights that Fe dynamics plays a key role in the release of TA from sediments where Fe sulfide formation is limited by Fe availability, as exemplified by the Baltic Sea. Moreover, it demonstrates that burial of Fe sulfides should be included in TA budgets of low-oxygen basins.

Environmental Context. Selenium (Se) is one of the most serious problems confronted in agricultural soils derived from Se-containing rocks. This metalloid, an essential nutrient for animals and humans, may be toxic at relatively low concentrations. Se removal from soil and water using plants is a promising alternative to traditional chemical or electrochemical techniques. However, very few plant species are able to accumulate Se at high concentrations. Since Se and sulfur (S) have similar chemical properties, sulfate (SO42−) in the plant growth media may interfere in the process of Se uptake by plants. Thus, plant species able to uptake more Se than S when both elements are present are desired for Se phytoremediation purposes. . Hydroponic experiments were performed to study several aspects of Se uptake by C. arvensis plants. Ten day old seedlings were exposed for eight days to different combinations of selenate (SeO42−), sulfate (SO42−), and selenite (SeO32−). The results showed th...

Oceanic uptake of anthropogenic CO2 leads to decreased pH, carbonate
ion concentration, and saturation state with respect to
CaCO3 minerals, causing increased dissolution of these minerals
at the deep seafloor. This additional dissolution will figure prominently
in the neutralization of man-made CO2. However, there
has been no concerted assessment of the current extent of anthropogenic
CaCO3 dissolution at the deep seafloor. Here, recent databases
of bottom-water chemistry, benthic currents, and CaCO3
content of deep-sea sediments are combined with a rate model to
derive the global distribution of benthic calcite dissolution rates
and obtain primary confirmation of an anthropogenic component.
By comparing preindustrial with present-day rates, we determine
that significant anthropogenic dissolution now occurs in the western
North Atlantic, amounting to 40–100% of the total seafloor
dissolution at its most intense locations. At these locations, the
calcite compensation depth has risen ∼300 m. Increased benthic
dissolution was also revealed at various hot spots in the southern
extent of the Atlantic, Indian, and Pacific Oceans. Our findings
place constraints on future predictions of ocean acidification, are
consequential to the fate of benthic calcifiers, and indicate that a
by-product of human activities is currently altering the geological
record of the deep sea.

The measurable supply of 232 Th to the ocean can be used to derive the supply of other elements, which is more difficult to quantify directly. The measured inventory of an element divided by the derived supply yields a replacement time estimate, which in special circumstances is related to a residence time. As a proof of concept, Th-based supply rates imply a range in the replacement times of the rare earth elements in the North Atlantic that is consistent with the chemical reactivity of rare earth elements related to their ionic charge density. Similar estimates of replacement times for the bioactive trace elements (Fe, Mn, Zn, Cd, Cu, and Co), ranging from <5 years to >50,000 years, demonstrate the broad range of elemental reactivity in the ocean. Here we discuss how variations in source composition, fractional solubility ratios, or noncontinental sources, such as hydrothermal vents, lead to uncertainties in Th-based replacement time estimates. We show that the constraints on oceanic replacement time provided by the Th-based calculations are broadly applicable in predicting how elements are distributed in the ocean and for some elements, such as Fe, may inform us on how the carbon cycle may be impacted by trace element supply and removal.

Li/Ca in calcitic benthic foraminiferal tests has been suggested to co-vary with both temperature and carbonate chemistry, but these two influences have been difficult to disentangle. We use several new downcore records of Li/Ca in Cibicidoides wuellerstorfi and Uvigerina, paired with the carbonate proxy B/Ca, to further elucidate this behavior. We also combine the downcore measurements with a compilation of coretop Li/Ca data. Uvigerina B/Ca presumably records pore water saturation with respect to calcite (DCO 3 2À), though downcore data show that it partially reflects bottom water DCO 3 2À (inferred from C. wuellerstorfi B/Ca), with a relationship that is consistent with a previous global coretop calibration. Downcore Li/Ca is significantly correlated to B/Ca in both taxa, implying a positive relationship between Li/Ca and carbonate chemistry. This connection breaks down in the coretop compilation however, likely due to the confounding influence of temperature on Li/Ca. We attempt to isolate the temperature influence using a negative exponential equation previously derived from abiotic calcite precipitation experiments, and introduce a new quantity DLi/Ca, which is the observed departure from the temperature-based prediction. This transformation brings the downcore and coretop Li/Ca measurements into alignment, with up to 90% of the DLi/Ca variance explained by DCO 3 2À. Finally, we perform preliminary tests of Li/Ca as a paleo-proxy for both DCO 3 2À and temperature.

The ocean moderates anthropogenic climate change at the cost of profound alterations of its physics, chemistry, ecology, and services. Here, we evaluate and compare the risks of impacts on marine and coastal ecosystems—and the goods and services they provide—for
growing cumulative carbon emissions under two contrasting emissions scenarios. The current emissions trajectory would rapidly and significantly alter many ecosystems and the associated services on which humans heavily depend. A reduced emissions scenario—
consistent with the Copenhagen Accord’s goal of a global temperature increase of less than 2°C—is much more favorable to the ocean but still substantially alters important marine ecosystems and associated goods and services. The management options to address ocean impacts narrow as the ocean warms and acidifies. Consequently, any new
climate regime that fails to minimize ocean impacts would be incomplete and inadequate.

Se realizó un estudio preliminar sobre el contenido
de cadmio (Cd), plomo (Pb), mercurio (Hg) y
arsénico (As) en muestras de fi letes de pescado
congelado de elevado consumo en El Ecuador
como, corvina (Cynoscion phoxocephalus), dorado
(Coryphaena hippurus), tilapia (Oreochromis
niloticus) y atún (Thunnus obesus); adquiridos en
diversos supermercados de la ciudad de Machala,
Provincia El Oro. Los resultados preliminares
muestran la contaminación de estos productos por
As, Pb y Hg, superando las Normas Internacionales
establecidas para el consumo humano. En todas
las muestras examinadas los valores de Cd
fueron inferiores al límite de detección del método
(0,0042 mg. kg-1). La correlación signifi cativa entre
el contenido de Hg, Pb y As en las muestras de
músculo de pescado evaluadas, puede sugerir
que estos contaminantes tienen un origen común
ya que las elevadas concentraciones de As, Pb y
Hg son consecuencia de las aguas domésticas e
industriales vertidas sin tratamiento alguno en la
zona costera así como, la escorrentía proveniente
de las zonas de cultivos y al aporte atmosférico.