Limmer D.R.,University of Aberdeen |
Bning P.,University of Oldenburg |
Giosan L.,Woods Hole Oceanographic Institution |
Ponton C.,Woods Hole Oceanographic Institution |
And 4 more authors.
Geochemistry, Geophysics, Geosystems | Year: 2012
We present a multiproxy geochemical analysis of two cores recovered from the Indus Shelf spanning the Early Holocene to Recent (<14 ka). Indus-23 is located close to the modern Indus River, while Indus-10 is positioned ∼100 km further west. The Holocene transgression at Indus-10 was over a surface that was strongly weathered during the last glacial sea level lowstand. Lower Holocene sediments at Indus-10 have higher ε Nd values compared to those at the river mouth indicating some sediment supply from the Makran coast, either during the deposition or via reworking of older sediments outcropping on the shelf. Sediment transport from Makran occurred during transgressive intervals when sea level crossed the mid shelf. The sediment flux from non-Indus sources to Indus-10 peaked between 11 ka and 8 ka. A hiatus at Indus-23 from 8 ka until 1.3 ka indicates non-deposition or erosion of existing Indus Shelf sequences. Higher ε Nd values seen on the shelf compared to the delta imply reworking of older delta sediments in building Holocene clinoforms. Chemical Index of Alteration (CIA), Mg/Al and Sr isotopes are all affected by erosion of detrital carbonate, which reduced through the Holocene. K/Al data suggest that silicate weathering peaked ca. 4-6 ka and was higher at Indus-10 compared to Indus-23. Fine-grained sediments that make up the shelf have geochemical signatures that are different from the coarser grained bulk sediments measured in the delta plain. The Indus Shelf data highlight the complexity of reconstructing records of continental erosion and provenance in marine settings. Copyright 2012 by the American Geophysical Union.
Clift P.D.,Louisiana State University |
Giosan L.,Woods Hole Oceanographic Institution |
Henstock T.J.,University of Southampton |
Tabrez A.R.,National Institute of Oceanography
Basin Research | Year: 2014
The transport of sediment from the mouth of the Indus River on to the deep-water submarine fan is complicated by temporary storage within large clinoforms on the shelf on either side of the submarine canyon, where most of the sedimentation since the start of the Holocene has occurred. In contrast, shelf edge clinoform deltas represent the products of forced regression and not the progradation of highstand clinoforms as far as the shelf edge. Clinoform sediments have a mixed provenance that involves significant reworking of older sediment deposited during or before the last glacial maximum. Recent sedimentation in the canyon head has been very rapid in the last few centuries (ca. 10 cm year-1), but has been starved of sand probably because of 20th century damming. Sandy layers appear to represent annual monsoonal floods with a particularly large flood every 50-70 years. This canyon head sediment is also reworked by currents flowing along the canyon axis before being deposited deeper into the canyon. The last sandy sediment to reach the mid-canyon (ca. 1300 m depth) was transported around 7000 year BP at a time of rising sea-levels, and might reflect reworking by the transgression, or local slumping from the walls of the canyon. Dating of the uppermost in a series of terraces in the mid-canyon area suggests that the canyon may have been partly filled and emptied of sediment at least three times since ca. 50 ka. We conclude from the Holocene record that sediment flux to the deep-water fan experiences major buffering, reworking and recycling both on the shelf and within the submarine canyon prior to its deposition, so that turbidite sands in the deep Arabian Sea cannot be used to correlate with climatic or tectonic events onshore over timescales of 103-105 years. © 2014 John Wiley & Sons Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists.
News Article | December 5, 2016
Large areas of the global ocean, so called marine "dead zones" contain no oxygen and support microbial processes that remove vast amounts of nitrogen from the global ocean. Nitrogen is a key nutrient for life. These dead zones are well known off the western coasts of North and South America, off the coast of Namibia and off the west coast of India in the Arabian Sea. New research published in the journal Nature Geoscience shows that the Bay of Bengal, located in the northeastern Indian Ocean, also hosts a "dead zone" of an estimated 60,000 km2 and occupying water depths of between 100 and 400 meters. This research was conducted as cooperation between the University of Southern Denmark (SDU), the Max Planck Institute (MPI) for Marine Microbiology in Bremen and the National Institute of Oceanography (NIO) of India. Lead author of the study Laura Bristow, a former postdoc at SDU and now a scientist at the MPI explains "the Bay of Bengal has long stood as an enigma because standard techniques suggest no oxygen in the waters, but, despite this, there has been no indication of nitrogen loss as in other 'dead zones' of the global ocean". Using newly developed oxygen-sensing technology, the researchers demonstrated that some oxygen does exist in the Bay of Bengal waters, but at concentrations much less than standard techniques could detect and some 10,000 times less than found in the air-saturated surface waters. The researchers also discovered that the Bay of Bengal hosts microbial communities that can remove nitrogen, as in other well-known "dead zones" and even some evidence that they do remove nitrogen, but at really slow rates. Bristow continues "we have this crazy situation in the Bay of Bengal where the microbes are poised and ready to remove lots more nitrogen than they do, but the trace amounts of oxygen keep them from doing so". Wajih Naqvi, former director of NIO, and a co-author of the study, adds "remove the last amounts of oxygen, and the Bay of Bengal could become a major global player in nitrogen removal from the oceans". Removing more nitrogen from the oceans could affect the marine nitrogen balance and rates of marine productivity. Globally, warming of the atmosphere through climate change is predicted to lead to an expansion of "dead zones" in the global ocean. It is currently unclear whether climate change would lead to the removal of these last traces of oxygen from the Bay of Bengal waters. However, the Bay of Bengal is also surrounded by a heavy population density, and expected increases in fertilizer input to the Bay may increase its productivity, contributing to oxygen depletion at depth. Bristow warns "Time will tell, but the Bay of Bengal is at a "tipping point", and we currently need models to illuminate how human activities will impact the nitrogen cycle in the Bay of Bengal, and also globally".
Mahmood T.,East China Normal University |
Mahmood T.,National Institute of Oceanography |
Fang J.,Chinese Academy of Fishery Sciences |
Jiang Z.,Chinese Academy of Fishery Sciences |
Zhang J.,East China Normal University
Chemistry and Ecology | Year: 2016
Seasonal distribution of dissolved nutrients ((Formula presented.) , (Formula presented.) , (Formula presented.) , (Formula presented.) , (Formula presented.)) was measured in the Sanggou Bay (SGB), China. In order to understand the impact of rivers and of the Yellow Sea (YS) and the role of integrated multi-trophic aquaculture (IMTA) in nutrient reduction and dynamics. Seasonal surveys were conducted in spring (April), summer (August), autumn (October) and winter (January) in 2011–2012 along 19 stations covering culture areas. The summer was highly impacted by excess water discharge and aquaculture activities than benthic sediments source; however other seasons were mostly influenced by the YS. Results showed that nutrients were vertically mixed and IMTA helped in reducing the elevated nutrient concentration generated by water discharge and the mixing process. The N/P ratio indicated phosphate as a limiting nutrient. Historical values of nutrient data showed that the concentration of (Formula presented.) , (Formula presented.) and (Formula presented.) increased while (Formula presented.) decreased with slightly higher uptake rate of (Formula presented.) in the bay during the last decade. A simple mass-balance model was employed to determine the nutrient budget which showed that nutrients were mostly from the river input. This implies an increase in the anthropogenic activities and assimilation of (Formula presented.) in the SGB. Such increasing trends in nutrient concentration could cause eutrophication in the bay. © 2015 Taylor & Francis.
PubMed | TERI University, National Institute of Oceanography, Cochin University of Science and Technology and National Institute of Oceanography of India
Type: Journal Article | Journal: Marine pollution bulletin | Year: 2014
Total organic carbon (TOC) (in sediment) and dissolved organic matter (DOM) (in water column) play important roles in controlling the mercury sequestration process by the sediments from the central east coast of India. This toxic metal prefers to associate with finer size particles (silt and clay) of sediments. Increasing concentrations of DOM in overlying water column may increase complexation/reduction processes of Hg(2+) within the water column and decrease the process of Hg sequestration by sediments. However, high concentrations of DOM in water column may increase Hg sequestration process by sediments.
Limmer D.R.,University of Aberdeen |
Kohler C.M.,University of Aberdeen |
Hillier S.,James Hutton Institute |
Moreton S.G.,Natural Environment Research Council |
And 2 more authors.
Marine Geology | Year: 2012
We present a multi-proxy mineral record based on X-ray diffraction and diffuse reflectance spectrophotometry analysis for two cores from the western Indus Shelf in order to reconstruct changing weathering intensities, sediment transport, and provenance variations since 13. ka. Core Indus-10 is located northwest of the Indus Canyon and exhibits fluctuations in smectite/(illite. +. chlorite) ratios that correlate with monsoon intensity. Higher smectite/(illite. +. chlorite) and lower illite crystallinity, normally associated with stronger weathering, peaked during the Early-Mid Holocene, the period of maximum summer monsoon. Hematite/goethite and magnetic susceptibility do not show clear co-variation, although they both increase at Indus-10 after 10. ka, as the monsoon weakened. At Indus-23, located on a clinoform just west of the canyon, hematite/goethite increased during a period of monsoon strengthening from 10 to 8. ka, consistent with increased seasonality and/or reworking of sediment deposited prior to or during the glacial maximum. After 2. ka terrigenous sediment accumulation rates in both cores increased together with redness and hematite/goethite, which we attribute to widespread cultivation of the floodplain triggering reworking, especially after 200. years ago. Over Holocene timescales sediment composition and mineralogy in two localities on the high-energy shelf were controlled by varying degrees of reworking, as well as climatically modulated chemical weathering. © 2012.
Khan N.,National Institute of Oceanography |
Muller J.,University of Queensland |
Khan S.H.,National Institute of Oceanography |
Amjad S.,National Institute of Oceanography |
And 2 more authors.
Journal of the Chemical Society of Pakistan | Year: 2010
Mangrove swamps, intertidal mudflats and creeks of backwaters represent main feature of Karachi harbour area. Karachi harbour sediment is under continuous influence of untreated industrial effluents and domestic waste discharged into the Harbour area vra Lyari River Sediment samples from sixteen locations were collected to evaluate the levels of contamination of organochlorine pesticides (OCPs) in Karachi harbour and adjoining areas. It has been observed that residual concentrations of various organochlorine pesticides were considerably higher in the semienclosed area of the upper Harbour in the vicinity of the discharge point of Lyari River. The residue of DDT mainly its metabolites (DDE and DDD) were widely distributed and have been detected in most of the sediment samples in relatively higher concentrations as compared to other OCPs. The higher levels of the DDTs would attribute to low tidal flushing of the area The high proportion of pp'-DDE in the most sediment sampled (41-95%) suggested old inputs of DDTs in the environment. Ratio of SDDT and DDT was in the range of 0,04 -0 24 at all locations which also reflects that the discharges of DDT were negligible in the Harbour area. This may be due to the restrictions being implemented on the use of DDTs and Pakistan has also switched over to natural pest control or using safer formulas. The data obtained during the study showed that concentration levels of other pesticides such as HCHs, HCB and Cyclodienes in the sediment were generally lower than the threshold levels known to harm wildlife by OCPs. The results clearly indicate that elevated concentration of organochlorine pesticides (OCPs) in the marine sediment of Karachi harbour and adjoining area was localized and much lower than the concentrations reported from neighbouring and regional countries which suggests/confirms that the present use of pesticide in Pakistan is environmentally safe.
News Article | January 4, 2016
One whale spotted in the wrong ocean seemed merely odd. But a second misplaced whale looked more like a sign of an ecological shake-up: Pacific Ocean fauna moving into the Atlantic Ocean and vice versa. As the Arctic’s icy barriers melt, new waterways may soon allow many formerly separated animals to move and mix. “We do believe we’re seeing a faunal exchange,” says Seabird McKeon of the Smithsonian Marine Station in Fort Pierce, Fla. Species moving from one ocean might disrupt life in the other — competing with some longtime residents, preying on others — or maybe change hardly anything. “We just do not know what’s going to happen,” McKeon says. He and seven other scientists compiled from various sources several years’ worth of wrong-ocean sightings of whales and birds suspected to have crossed the Arctic or mingled with counterparts from the opposite ocean. The compilation, published online November 30 in Global Change Biology, isn’t big. But for long-lived creatures such as whales and some seabirds, a trickle of animals could establish a new population. Unusual sightings of birds and mammals (a selection below) suggest that once-blocked populations of animals might already be moving now that enough Arctic ice is melting to allow it. Expansion of an Arctic population into Hudson Bay as ice blockades melt allows the whales to prey on beluga whales, narwhals and at least four seal species. An Atlantic subspecies was spotted in California in 2011; Pacific subspecies were found in Newfoundland and Norway in 2014. The Northern Pacific seabird was seen in England in 2009. The North Atlantic seabird may now be breeding in the Pacific. “Even if the strays are few, even if it’s a very slow process, there is a chance of establishment,” McKeon says. “That’s why we’re excited for people to really start watching this process.” Birders, whale watchers and other citizen scientists offer the best hope for catching early signs of any species moving across the Arctic. “If an individual bird ends up in an alternative ocean basin, that is not something that is likely to be picked up by standard scientific programs,” McKeon says. In the past, thick permanent sea ice in the Arctic plus potentially lethal water temperatures, scarce food, unusual salinity and other menaces have acted as a barrier between oceans, largely blocking animal journeys for the last 3 million years. But climate change is opening up a path. The 10 skimpiest minimums for summertime ice observed since the satellite era began have all occurred in the last 11 years, NASA analyses show. Summer ice has dwindled enough on occasion, such as in 2012, to raise commercial hopes of workable waterway passages for shipping. Feasible paths are opening in successive years through the archipelago of islands in eastern Canada, and other routes may form, too, so trade ships in coming decades may be able to shortcut through the summertime Arctic. Human commerce and the politics of climate change get more widespread attention than the chance that animals will venture along the new routes. But rearranging species’ ranges could have sweeping consequences, too. A notorious example of the unintended troubles that range changes can cause comes from the Suez Canal in Egypt. The canal “has been singularly successful as an invasion corridor,” says Bella Galil of the National Institute of Oceanography in Haifa, Israel. Of nearly 700 alien species now found in the Mediterranean Sea, half have arrived through the canal since it opened in 1869, Galil reported in the April Biological Invasions. In summer, swarms of nomad jellyfish (Rhopilema nomadica), originally from the Red Sea, clog fishing nets and block intake pipes at desalinization and power plants in Israel. Another newcomer, the poisonous Lagocephalus sceleratus puffer fish, puts several people in the hospital each year. And introductions such as the goldband goatfish and a kind of spiny oyster have wiped out their native counterparts. In contrast, the Panama Canal shepherds traffic through locks filled with freshwater, which reduces the risk of saltwater Pacific species sloshing through to the Caribbean Sea and vice versa. And thank goodness. McKeon says he has heard discussions about whether a saltwater canal in Panama would have let the venomous sea snakes from the Pacific wriggle their way into the Caribbean. In the rapidly changing Arctic, at least one Pacific species has already established populations on the North Atlantic side for the first time in about 800,000 years. Microscopic strings of silica-encased Neodenticula seminae diatoms turned up in the late 1990s in the Labrador Sea, an international research team reported in 2007. The researchers argue against the notion that the diatoms merely hitchhiked in some ship’s ballast water. Instead, the diatoms’ presence could be a sign that ocean circulation patterns are changing in the Arctic, swirling water and its living residents across the pole. What the diatoms will do Atlanticside isn’t clear, but they have now spread to northern Nordic waters, a paper published in 2013 reports, where there’s no sign they have ever been before. Of perhaps more popular interest than transplanted diatoms are potentially Arctic-crossing whales. Gray whales persist in the Pacific but went extinct in the Atlantic more than two centuries ago. In 2010, a marine-mammal monitoring program photographed a gray whale off the coast of Israel. “It was really a huge surprise to everybody,” says Elizabeth Alter of York College CUNY in Jamaica, N.Y., a coauthor with McKeon on the new paper. “There was discussion at first of whether the photos might have been photoshopped.” (They were not, it turned out.) In 2013, a monitoring group sighted another gray whale along the coast of Namibia. It seems improbable that gray whales from the northern Pacific had looped down to the Southern Hemisphere to swim around continents and then into the Atlantic, Alter says. She suspects the whales were feeding along the Arctic coastline as they normally do, and without much ice to block their progress, inadvertently hugged the coast all the way to the Atlantic side. Should gray whales eventually recolonize the Atlantic, McKeon expects that their new neighbors would notice. Unlike similar whales with baleen plates in their mouths, grays gulp whale-sized mouthfuls of soft sea-bottom gunk to savor its hidden crustaceans. In the course of dining, the whales stir up sediment, scattering clouds of invertebrates that other species eat and leaving behind whale-gouges as habitat. It’s impossible to know the impacts, but McKeon speculates on what could happen to the blue crabs that bury themselves in the mud at the mouth of the Chesapeake Bay in winter: “I can’t imagine anything much better as a snack for a wintering gray whale than sleepy blue crabs.” Melting may also bring new opportunities to another whale species, the bowheads, which live in the Arctic full time. “They can break ice that’s 2 feet thick with their heads,” Alter says. The Atlantic and Pacific bowhead populations have shared genes over the last several thousand years, Alter’s DNA studies show. And in 2010, biologists tracking both populations by satellite found a whale from each population feeding near each other. After about a week, the whales retreated in opposite directions, but left clear evidence that the melting Arctic permits populations from separate oceans to mix. Also on McKeon’s list of possible vanguards of Arctic crossovers is a northern gannet, a plunge-diving, fish-eating seabird that soars over the Atlantic with a wingspan of about 2 meters. “What every gull dreams of being,” he says. In 2011, one of these gannets showed up off the coast of Alaska. Possibly the same bird reached the Farallon Islands along northern California. The most plausible explanation, McKeon says, is that the bird had worked its way through some avian northwest passage with open water for fishing along its flight path. Open water in the Arctic could also move animals indirectly. As summer sea ice shrinks more and more, shipping could boom along Arctic routes. These ships take on ballast water in one place and release the ballast in another, letting animals (smaller than whales) catch a lift, says Jacqueline Grebmeier of the University of Maryland Center for Environmental Science. The prevailing wisdom has been that stowaways wouldn’t survive the harsh Arctic, but as the Arctic climate changes, Grebmeier can imagine circumstances now in which ballast creatures might. Whales and charismatic seabirds may be easier to spot when they switch oceans, but ballast stowaways may turn out to be more common. And as important.
Ismail S.,PCSIR Head Office |
Saifullah S.M.,University of Karachi |
Khan S.H.,National Institute of Oceanography
Pakistan Journal of Botany | Year: 2014
In the present study monitoring of heavy metal pollution was done in the mangrove habitats of Indus Delta. Different levels of four heavy metal (Pb, Cu, Cd, and Zn) in abiotic component (sediments and water) and biotic components (mangrove plants parts like, (Pneumatophores, bark, leaves, flowers, and fruits) were determined. The highest average concentration of heavy metals (111 ppm Zn, 60.0 ppm Pb, 52.2 ppm Cu, 1.43 ppm Cd) were measured in sediments and the lowest in the water (0.13 ppm Zn, 0.0014 ppm Cu, 0.0007 ppm Pb, 0.00061ppm Cd). Among the four heavy metals, Zn was the most abundant metal in all components of the ecosystem, followed by Cu, Pb, and Cd (Zn>Cu>Pb>Cd), and hence A. marina can be proposed as a hyper-accumulator for Zn, which opens doors for further research. The pollution load index (PLI) had values higher than 1 and varied between 2.02-1.70 at Indus Delta, whereas at MianiHor the PLI was 0.65, which indicated that Indus Delta mangrove Ecosystem was under threat of pollution under the present scenario.
Shaheen A.,National Institute of Oceanography |
Baig H.S.,National Institute of Oceanography |
Kazmi S.U.,University of Karachi
Pakistan Journal of Botany | Year: 2016
Marine pollution has now become worldwide environmental concern. Continuous discharge of untreated industrial effluent, municipal and power plant’s contaminated wastewater has been a serious threat to marine habitat, aesthetic values and interest of visitors to coastal areas. Karachi is the largest city of Pakistan and industrial hub of the Arabian Sea. In this investigation, samples of sediment, water, flora and fauna were taken from nine selected stations on Karachi coast included three stations represented major creeks i.e. Korangi, Gizri and Chinna Creek. These samples were taken during north-east and south-west monsoonal period in 2014. Bacterial flora isolated and identified from samples collected from these sites by conventional method. Among isolated and identified bacteria e.g. Vibrio alginolyticus, Escherichia coli and Streptococuss anginosus were the most dominant species contributing 21.43, 19.64 and 15.18 percent of total assemblage respectively. Among selected sample stations, Korangi creek station was found to be most polluted with coliform and other pathogenic bacteria. These results clearly indicate that threats from these pathogens are not only to marine life but also to the large number of visitors coming to beaches and residents of surrounding area. Moreover; immediate action should be taken to restrict the growth of these pathogens by taking measures to treat the municipal and industrial effluent to avoid outbreak of any disease in future. © 2016, Pakistan Botanical Society. All rights reserved.