Papers by Mandar Nanajkar
Seven stations were sampled within the Mormugao harbour area for benthos and environmental variab... more Seven stations were sampled within the Mormugao harbour area for benthos and environmental variables from September 2003 to July 2004. A total of 71 polychaete taxa were identified from the area. Polychaete abundance, biomass and species number was highest during post monsoon, mainly due to new recruitment. Pre monsoon is the most stable period for community development when, the fauna was dominated by opportunistic deposit feeding polychaete species. Average abundance ranged from 652-4096 ind m -2 reported at channel and harbour station respectively. Harbour station was dominated by P. pinnata, Magelona sp., Tharyx sp. and Cossura sp. Univariate and multivariate analyses showed clear demarcation of outer harbour, inner harbour and channel stations. Correlation of physico-chemical and biotic parameters did not show a significant correlation. Dominance of opportunistic deposit feeding species and low polychaete diversity in the inner harbour indicate negative impact of harbour activities on the species composition.
Italian Journal of Zoology, 2011
Meiofaunal nematodes are among the most important components of the benthic environment. They hav... more Meiofaunal nematodes are among the most important components of the benthic environment. They have unusually high abundance and diversity. They are largely understudied in many parts of the world and explored very little from the Indian subcontinent, possibly due to lack of expertise. Meiofauna was investigated with emphasis on nematodes, which were the most dominant group and one species -Terschellingia longicaudata (De Man, 1907) -along the central west coast of India, stretching between Ratnagiri and Mangalore, during 2004. Maximum nematode diversity was found at the offshore location at the water depth of 35 m, while the minimum was found in the estuarine region. Nematode density was positively correlated with sediment organic matter (r = 0.73, p < 0.05). Among the 94 identified nematode species, T. longicaudata was one of the dominant species comprising >21% of nematodes and 15% of the total meiofaunal population. The species had high abundance at the stations mostly characterized by silty sediment. T. longicaudata has been hypothesized to have a global distribution and the present study, for the first time, adds to the inventory of its distribution along the central west coast of India.
Journal of Experimental Marine Biology and Ecology, 2011
Although organic matter (OM) settling on the seafloor is generally rapidly recycled, a key ecolog... more Although organic matter (OM) settling on the seafloor is generally rapidly recycled, a key ecological process, large scale burial events manifests itself in the marine sedimentary record as organic carbon (C org )-rich layers. Presently, this prevails under certain oceanic settings such as the oxygen minimum zones (OMZ) where OM accumulates in underlying sediments. A basic question that remains is to what extent does accumulation reflect a shunting of ecological processes: a niche unconquered? Experimenting with eastern Arabian Sea OMZ sediment we demonstrate that C org accumulation here is not due to trophic satiation or low tolerance of biota to severe oxygen depletion but that sediment C org has very low bioavailability that probably impairs biological transformation.
Environment International, 2006
The ecotoxicological effects of oil spill from the grounded vessel MV River Princess on the inter... more The ecotoxicological effects of oil spill from the grounded vessel MV River Princess on the intertidal benthic organisms of Sinquerim -Candolim beach at Goa were investigated. An intertidal expanse of 1km on either side of the grounded vessel was selected to evaluate the concentration of Total Petroleum Hydrocarbon (TPH) in the sediment and its effects on the composition, abundance and diversity of micro-, meio-and macrobenthos. TPH in the intertidal sediment ranged from 7.8 to 89 µg g -1 (mean35.44 ± 26.35 SD). Microbenthos comprised of microalgae, protozoans and juvenile forms of meiobenthos. Apart from juvenile nematodes, which were abundant, Coscinodiscus spp, Navicula spp, and Nitzschia spp. representing microalgae were also observed in microbenthic samples. Meiobenthos was represented by 13 taxa and their total density ranged between 92-1057 no. 10cm -2 . Maximum meiobenthic abundance of 1057 no.10cm -2 was observed at Sinquerim. Nematodes were the dominant meiobenthic taxa followed by turbellarians and harpacticoid copepods. The macrobenthoc was numerically dominated by polychaetes, followed by crustaceans whereas bivalve molluscs were less represented. There was substantial increase in the petroleum concentration in the beach sediment compared to the previously reported values and highest TPH (89µg.g -1 sediment) values were in the vicinity of the grounded vessel. The polychaete/amphipod ratio and cumulative and partial dominance abundance-biomass curves showed significant negative impact of TPH on macrofauna. The benthic community structure also showed measurable changes, as there was significant decrease (60%) in the number of species. Given that the microalgal counts were low in sediment, it is assumed that the intertidal meiofauna was possibly using oildegrading bacteria as alternate food source. In conclusion, the results reported here suggest that the grounded ore carrier is not only detrimental to the beach community, that may take longer time for recovery, but also affect the beach morphology which may have long-term impact on local fishery.
Environmental Monitoring and Assessment, 2011
Natural disturbances along with human interference make the tropical estuaries amongst the most d... more Natural disturbances along with human interference make the tropical estuaries amongst the most disturbed areas globally. In spite of this, information on the seasonal variability of macrofauna from tropical estuaries is few. Temporal variability of macrofaunal community from Mormugao Bay, Zuari estuary, on the west coast of India was examined from 2003 to 2004 at seven stations. Environmental variability was assessed through physicochemical parameters of water and sediment. The changes in macrobenthic community were assessed using abundance, biomass and species diversity indices. The environmental parameters showed a significant seasonal variation influenced by monsoonal changes. The changes in the environmental conditions brought about variation in the macrobenthic community. Macrofaunal abundance, biomass and species diversity were the highest during post-monsoon influenced by recruitment. In monsoon, the macrobenthic community was dominated by polychaetes (92.17%), whereas bivalves dominated during the post-monsoon (57.7%). The macrofauna showed drastic decline during the stable pre-monsoon season, a period when the highest abundance of fauna is observed in the tropical estuary. Therefore, the macrobenthic community in the area did not follow the seasonal trend generally observed in a tropical estuary. Further, the community during pre-monsoon season was dominated by the opportunistic polychaete species indicating a possible influence of harbour activities in structuring the benthic community of the area.
Marine Ecology, 2010
Patterns of macrofaunal distribution were studied along the western Indian continental margin to ... more Patterns of macrofaunal distribution were studied along the western Indian continental margin to distinguish the role of habitat heterogeneity in generating and maintaining community structure. A transect perpendicular to the coast at 14°N latitude was selected for seabed sampling. Eight stations were sampled in the depth range 34–2546 m and characterized with respect to macrofaunal composition, abundance, biomass, diversity and feeding type. The sediments in the shelf region (34, 48, 100 m) and upper slope (525 m) were characterized by silty and sandy facies, whereas the mid slope (1001 m), lower slope (1524 m) and basin (2001, 2546 m) consisted of clayey silts. The highest value of sediment chlorophyll-a (Chl-a) and total organic carbon (Corg) were recorded from the mid slope areas. Faunal abundance and biomass increased from the shallow to deeper depths in the shelf region, and decreased in the slope region (525–1001 m) due to the reduced bottom-water oxygen. The community parameters showed an overall increase in both the lower slope and basin areas. A total of 81 macro-invertebrate species belonging to five major groups represented the macrofauna of the area. Polychaeta was the major group at all depths. Among polychaete families, species of the Spionidae, particularly Prionospio pinnata, predominated at the oxygen minimum zone (OMZ) core and Cossuridae dominated in the lower part of the OMZ in sediments of the mid slope region (1001 m depth). Species diversity was higher in the basin than in the slope region. Fluctuations in diversity appear to be partly due to the bottom-water dissolved oxygen (DO) gradient which includes values that are below the oxygen tolerance of many benthic species. Further, Margalef’s index (d) and Shannon–Wiener index (H′) showed a significant negative (P < 0.01) relationship between sediment Chl-a and Corg, suggesting food availability as a critical factor in species dominance. Results of multivariate analyses suggest that for continental margin fauna, different physiographic provinces and an oxygen gradient have a higher influence on the species composition and diversity than other oceanographic conditions.
Environmental Monitoring and Assessment, 2009
Harbours are heavily stressed coastal habitats characterised by high concentration of contaminant... more Harbours are heavily stressed coastal habitats characterised by high concentration of contaminant and low diversity of benthic community. The west coast of India harbours most of the major harbours compared to the east coast. Very few studies have compared the macrobenthic community between different Indian harbours. The present study was therefore conducted in three important harbour (Ratnagiri, Goa, Karwar) along the central west coast of India. The paper discusses the health status of the three harbours diagnosed using various biotic indices. Sediment samples were collected using van Veen grab (0.11 m2) on board CRV Sagar Sukti. A total of 55 macrobenthic taxa were identified and were numerically dominated by polychaete. Biomass was high (0.14–145.7 g m–2) and was made largely by echiurans (>80%). Overall, polychaete dominated the macrobenthic diversity. Opportunistic P.pinnata, Notomastus sp. and Mediomastus sp., dominated the macrobenthic community responding to the increased in the harbour. Biotic indices (Polychaete:Amphipod ratio, ABC curve and geometric class abundance) and the dominance of opportunistic species indicate that, the three harbours are under stress from anthropogenic activities.
Marine Biology Research, 2009
The deep-sea is well known for high benthic biodiversity despite being a low-food environment. Ho... more The deep-sea is well known for high benthic biodiversity despite being a low-food environment. However, most deep-sea organisms are very small in size as an adaptation to food limitation. Macrofauna are generally considered to be organisms larger than 0.5 mm and smaller than 3 cm. However, the smaller body size of fauna in the deep sea has led to the use of mesh sizes ranging between 0.25 to 0.5 mm to collect macrofauna, 0.3 and 0.5 mm being the most commonly used mesh sizes for deep-sea sampling. In this study, we tested the effectiveness of sieves of two different mesh sizes (0.3 and 0.5 mm) in assessing macrofaunal diversity, density and biomass. A total of 66 species were obtained with the smaller mesh (0.3 mm), while the larger mesh (0.5 mm) retained only 40 macrofaunal species. Thus, use of larger mesh resulted in the loss of 39% species over the smaller mesh (p=0.0001). However, both sieves yielded high densities of organisms, high species diversity and steep rarefaction curves for nematodes and polychaetes. Using the larger mesh resulted in a significant loss in biomass of 90% and 78% for polychaetes and nematodes respectively. Vertically in the sediment, faunal density was sampled more effectively with the smaller mesh sieve. Our results show a significant reduction in the 2 number of species, organism density, and biomass of macrofauna with use of a 0.5 mm mesh rather than a 0.3 mm mesh and that a sieve of lower mesh size is more suitable for evaluation of deep-sea macrofauna.
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Papers by Mandar Nanajkar