Papers by Monawwar Saleem
Nutrients measured on water bottle samples during AGHYAR cruise NASEER-1
Earth Interactions, Dec 1, 2004
The coastal area of Karachi, Pakistan, which lies at the northwestern part of the Indus delta, is... more The coastal area of Karachi, Pakistan, which lies at the northwestern part of the Indus delta, is heavily polluted particularly in the mangrove habitat. The present study traces the pathway of trace metal iron from the source to the different mangrove parts via seawater and sediment. The concentration in the sediment was as high as 34 436 ppm and as low as 0.01 ppm in seawater, while vegetative mangrove parts like pneumatophores, bark, twigs, and leaves possessed generally less than 1000 ppm. The concentration factor (CF) of mangroves was very low, indicating minimum bioavailability of iron from the sediment. The concentration of the metal decreases progressively through different sections of the mangrove habitat in the following sequence: from sediment to pneumatophores to bark to leaves to twigs to seawater.
Marine Ecology Progress Series, 1992
Benthic metabolism (sediment O2 uptake, CO2 production and sulfate reduction) and nitrogen dynam~... more Benthic metabolism (sediment O2 uptake, CO2 production and sulfate reduction) and nitrogen dynam~cs were studied in a mangrove swamp of the Indus Delta, Pakistan during fall 1990. The mangrove, whlch is characterized by large salinity fluctuations, has hlghly variable concentrations of C 1 and S o d 2 in the sediment porewater. Vertical profiles of these const~tuents reflect the historical events of salinity changes in the overlying water. Rates of O2 uptake (both measured d~rectly and estimated from 0, profiles) at intertidal creek banks were generally low and about 2 tlmes higher in airexposed than in water-covered sediment. The high rates found during air exposure was caused by a reduction in the thickness of the diffusive boundary layer and an increased area of oxic-anoxic interfaces due to drainage of water from large sediment interstices (burrows and cracks in the surface). The frequency and duration of water cover were important determinants for microbial respiration in the sediment. Highest rates during water cover were measured subtidally in creek sediment and lowest rates at intertidal creek bank sites. Desiccation may reduce overall microbial respiration at the creek banks. About half of the CO2 production measured during water cover could be accounted for by sulfate reduction in intertidal sediments, whereas only 18 "/o of the CO2 production in subtidal creek sedi m e n t~ could be ascribed to sulfate reduction. The remainder may be produced by other respiration processes. The low metabolic activity in the mangrove sediment was partly caused by the refractory nature of sediment detritus (mostly remains from tree leaves and roots). The generally low fluxes of dissolved inorganic nitrogen combined with the low nitrogen content in sediment detritus (C:N = 20) also indicated that nitrogen was a limiting factor for microbial activity in this mangrove swamp.
Marine Ecology Progress Series, 1997
We report the results of a 3 yr study on 2 tidal creeks in the northwest corner of the lndus Rive... more We report the results of a 3 yr study on 2 tidal creeks in the northwest corner of the lndus River delta (Pakistan) mangrove ecosystem. We measured light (extinction coefficients), nutrients (nitrate, nitrite, phosphate, silicate and ammonium), chlorophyll a (chl a), suspended load, primary pro-ductiv~ty (I4C uptake] and phytoplankton species In Isaro and Gharo Creeks. There was no clear seasonal cycle in any of the 5 nutrients in either of the 2 tidal creeks. NO3 ranged from l to 8 PM, NH, from 2 to 15 pM, Si04 from 3 to 20 pM, and PO, from 0.2 to 2 pM (except when it was undetectable during a bloom in lsaro Creek in June). Hence, nitrogen and silicate do not limit primary productivity, but during a large bloom phosphate may become limiting When phosphate samples were reanalyzed without removing the sed~ment (no filtration), phosphate concentrations were about 25 D/o higher. This suggests that phosphate is adsorbed to sediment particles and could potentially be biologically available. There was a high suspended load (100 to 180 mg 1-') because the sediments were fine (silt and clay) and they were kept suspended by high tidal currents (0.5 to 1.5 m S-') caused by tidal ranges of up to 4 m during spring tldes in these shallow (3 to 9 m deep) creeks. Hence, extinction coefficients were very high (1 to 2 m-') and the 1% light depth ranged from < l m in August (the rainy season) to about 4 m in January and February. Consequently, primary productivity appeared to be light-limited throughout the year. Chl a ranged from 1 to 4 pg 1-' with occasional blooms up to 40 pg I-'. Primary productivity ranged from 0.2 to over 1 g C mw2 d-' in lsaro Creek. There was no apparent seasonal cycle in chl a or primary productivity. Phytoplankton species were predominantly large centric diatoms which were presumably kept in suspension by tidal currents. Since nutrients are rarely limiting, there is an export of nutrients from the creeks to the coastal area which may stimulate phytoplankton productivity. KEY WORDS: Nutrients. Phytoplankton Mangroves. Tidal creekslndus River delta. Seasonal cycle. Primary productivity
Diurnal (24 hours) observations of dissolved nutrients, Chlorophyll-a, water quality (salinity, d... more Diurnal (24 hours) observations of dissolved nutrients, Chlorophyll-a, water quality (salinity, dissolved oxygen, temperature, pH and suspended solid matter) were recorded at one site in the Hajamro Creek of Indus Delta during the North East Monsoon period. The zoo-and phyto-plankton were recorded during low and high tides. Primary productivity was measured only during the day time. Dissolved nutrient concentration ranges were NH4 (1.81 µM-12.30 µM), NO3 (0.03 µM-1.48 µM), NO2 (0.04 µM-0.122 µM), PO4 (0.45 µM-1.69 µM), SiO3 (4.84 µM-24.49 µM) and averages were 6.41, 0.28, 0.055, 0.722, 12.12 µM respectively. The suspended load ranged from 36.0 mg/l to 87.8 mg/l, pH from 8.24 to 8.38, temperature from 18.73 o C to 22.37 o C and salinity from 35.995 ppt-37.062 ppt. Higher Chlorophyll-a concentration was recorded during the high tide in daytime and its range was 0.45 µg/l-1.69 µg/l while its average concentration was 1.94 µg/l. T he moderate value of primary productivity was recorded to be (0.475 g C/m 3 /day). Eleven groups of zooplankton were identified. Copepods were the main species which were abundant during high tide. Bivalve, fish eggs, crab and polychaete larvae were observed during low tide. The present study shows that high amounts of suspended solids, dissolved nutrients (phosphate, silicate, nitrate and ammonia) and relatively more salinity in sea water were recorded during low tide. Presence of adequate dissolved nutrients and high turbidity is probably restricting productivity in the Hajamro Creek.
Kahkashan_et_al._Suppporting_Information – Supplemental material for Holocene organic geochemical record from the Western Indus continental shelf (northern Arabian Sea)
Supplemental material, Kahkashan_et_al._Suppporting_Information for Holocene organic geochemical ... more Supplemental material, Kahkashan_et_al._Suppporting_Information for Holocene organic geochemical record from the Western Indus continental shelf (northern Arabian Sea) by Sanober Kahkashan, Jianfang Chen, Xinhong Wang, Peter D Clift, Bassem Jalali, Asif Inam, Monawwar Saleem, Javed Aftab, Zhongqiang Ji, Youcheng Bai, Zhongqiao Li, Jin Haiyan, Hongliang Li and Lihua Ran in The Holocene
Benthic communities of the Gwadar east bay (Balochistan) was surveyed during the onset of S.W. mo... more Benthic communities of the Gwadar east bay (Balochistan) was surveyed during the onset of S.W. monsoon. A total 1030 specimens were collected which represented Phyla of Arthropoda, Mollusca, Annelida, Echinodermata. The most abundant class observed was that of Bivalvia. Seawater parameters such as dissolved oxygen, temperature, pH, salinity together with sediment characteristics were measured. Analysis of variance between observed stations and fauna do not show any significant difference (P<0.05). The present observation forms a baseline study in the area
Evaluation of Marine Sediments Contamination by Polycyclic Aromatic Hydrocarbons (PAHs) along the Karachi Coast, Pakistan after Tasman Spirit Oil Spill Sanober Kahkashana,c, Xinhong Wanga*, Chen Evaluation of Marine Sediments Contamination by Polycyclic Aromatic Hydrocarbons (PAHs) along the Kara...
Chlorophyll a measured on water bottle samples during AGHYAR cruise NASEER-1
Fractionated primary productivity in the water column during AGHYAR cruise NASEER-1
Study of Heavy Metal Pollution Level and Impact on the Fauna and Flora Of the Karachi and Gwadar Coast
Chemosphere, 2019
PFAS and OCPs were determined in surface sediments of the adjacent Arctic Ocean. OCPs were orders... more PFAS and OCPs were determined in surface sediments of the adjacent Arctic Ocean. OCPs were orders of magnitude greater than the observed PFAS. PFOA was the main compound, and the most abundant OCPs were HCHs and DDTs. Industrial activities may be responsible for high levels of PFAS in the Bering Sea. An increasing latitudinal trend of OCPs were observed.
Chemosphere, 2019
On July 27, 2003, a spill of approximately 31,000 tons of Iranian light crude oil affected the co... more On July 27, 2003, a spill of approximately 31,000 tons of Iranian light crude oil affected the coast of Karachi, Pakistan. Approximately 11 years after the spill, we analyzed polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues (alkyl-PAHs) as the indicators to evaluate the residual effect of oil spill to the sediment along the Karachi coast. The total concentrations (dry weight) of parent PAHs and alkyl-PAHs ranged from 121.9 to 735.4 and 42.3 to 1149.9 ng/g, respectively. The estuary and harbor were the two regions with the highest levels of PAHs in the sediment. Conversely, sedimentary PAHs in the oil spill areas and remote coastal areas showed significantly lower levels. Although the results of the source identification indicated the up to 75.2% of the contribution from petroleum and its derivatives, this could only reflect the direct impact of the Karachi city on the presence of PAHs in the coastal sedimentary environment and did not indicated that the oil spill continues to stay 11 years later. Compared with 11 years ago, the sharply reduced PAH content, great changed composition, and the degradation driven trend of diagnostic ratios all indicated a sharp decrease in the influence of PAHs caused by the oil spill. Finally, the ecological risk caused by the PAH residual in the marine sedimentary ecosystem had disappeared along the Karachi coasts, Pakistan.
Pakistan Journal of Chemistry, 2013
To assess the contamination levels of organochlorine pesticides (OCPs) fifteen type (alpha, beta,... more To assess the contamination levels of organochlorine pesticides (OCPs) fifteen type (alpha, beta, gamma and delta HCH, Heptachlor, Heptachlor-epoxide, Endosulfan-I, Endosulfan-II, Aldrin, Dieldrin, Endrin, Endrin aldehyde, 4-4΄ DDT, 4,4΄ DDE and 4,4΄ DDD) of OCPS in samples of sea water, sediments, four fish and two crab species were determined in Damb (Sonmiani) coastal area. DDT, HCH and its metabolites found most dominating while Endrin, Dieldrin and Heptachlor recorded higher among the fifteen monitored pesticides in Damb (Sonmiani) coastal water. All these pesticides are found below the chronic concentration levels as set by the Coastal Water Quality Criteria for Washington State. HCH and Heptachlor were observed to be highest in the coastal sediments of Damb (Sonmiani) coastal area and these values are higher than the Canadian Interim Sediment Quality Standard. DDT, Endosulfan, its metabolites and isomers detected high concentration in marine biota, while α-BHC, Heptachlor and Endrin were also detected in low concentration. A preliminary risk assessment indicates that the daily intake of chlorinated pesticides by people consuming fish from the Damb (Sonmiani) coastal area is still very low and, therefore, is not likely to cause an immediate risk.
Heavy Metal Dynamics in Karachi Harbour
A study to measure the heavy metal pollution level in the sediment of coastal and offshore area i... more A study to measure the heavy metal pollution level in the sediment of coastal and offshore area indicates that high concentration of heavy metals were found around Manora channel and eastern coast of Karachi. In comparison with coastal areas, relatively low concentration of heavy metals was recorded in the offshore area. The result shows that sewage and industrial wastes are the main source of heavy metal pollution in the coastal area. The concentration of heavy metals in the sediments is as follows: Chromium 10.4-33.69, nickel 13.3-47.6, lead 10.0-39.04, cadmium 0.08-0.21, zinc 7.4-73.2 and copper 9.44-18.56 mg/kg. In the offshore areas strong correlation was observed between copper and organic carbon, and calcium carbonate and cadmium. In the shore area such correlation has been recorded among nickel, chromium, zinc, and chromium and copper. The Karachi. coast is viewed as moderately polluted when compared to other continental coastal areas.
Toxicity levels, Ecological risk assessment of Heavy metals and distribution in the surface sediment of Hub River, Hub River estuary and Gadani coast, Baluchistan, Pakistan
Fourteen sediment samples were collected from three sites (Hub River, Hub River estuary and Gadan... more Fourteen sediment samples were collected from three sites (Hub River, Hub River estuary and Gadani coast) for examining the concentrations and toxicity levels of heavy metals (Cadmium, Chromium, Copper Lead, Cadmium, Zinc, Manganese and Iron) and their concentrations. Furthermore, some factors and indexes, Contamination Factor, MERM-Q, Geo-accumulation Index, and Potential Ecological Risk Index were used for their environmental assessment and pollution status of surface sediments of the study area. The present data has also been compared with the sediment quality guideline. All the values of heavy metals of the study sites lie in the LEL (Lowest Effect Level) except for Cadmium but its values were also below the ERL (Effects Range Low). The results of the Geo-accumulation index of Cadmium indicate that the sediments in most studied stations of the three sites were moderately to strongly polluted (1.72-2.99). According to Geo-accumulation index all studied stations were found unpollu...
Nutrients measured on water bottle samples during AGHYAR cruise NASEER-1
Holocene organic geochemical record from the Western Indus continental shelf (northern Arabian Sea)
Primary production on the Western Indus continental shelf has been linked to the large quantities... more Primary production on the Western Indus continental shelf has been linked to the large quantities of nutrients delivered to the shelf by the Indus River. Multiple geochemical tracers and biomarker records, including stable isotopes (δ13C and δ15N), total organic carbon (TOC), total nitrogen (TN), molar carbon/nitrogen (C/N) ratio, the branched and isoprenoid tetraether (BIT) index, and glycerol dialkyl glycerol tetraether (GDGT), have been analyzed from the Indus-23AP sediment core recovered from the northern Arabian Sea. Our records show evidence of a mixture of marine and terrestrially derived organic matter (OM) during the last 14,000 years, as indicated by the C/N ratio, δ13C, δ15N, and the BIT index. The three sterol biomarkers (brassicasterol, dinosterol, and cholesterol) show concurrent enrichments during the last 3 millennia reflecting increased phytoplankton abundance because of increased Indus river discharge of nutrients during the summer monsoon. GDGT crenarchaeol enrich...
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Papers by Monawwar Saleem