Morphological identification of the marine cyclopoid copepod Dioithona rigida in combination with sequencing a 645 bp fragment of mitochondrial cytochrome oxidase c subunit I (mtCOI) gene, collected ...from offshore waters of Kavarathi Island, Lakshadweep Sea, is presented in this study. Kiefer in 1935 classified Dioithona as a separate genus from Oithona. The main distinguishing characters observed in the collected samples, such as the presence of well-developed P5 with 2 setae, 5 segmented urosome, 12 segmented antennule, compact dagger-like setae on the inner margin of proximal segment of exopod ramus in P1-P4 and engorged portion of P1-bearing a spine, confirmed their morphology to D. rigida. A comparison of setal formulae of the exopod and endopod of D. rigida with those recorded previously by various authors are also presented here. Maximum likelihood Tree analysis exhibited the clustering of D. rigida sequences into a single clade (accession numbers KP972540.1-KR528588.1), which in contrast was 37-42% divergent from other Oithona species. Further intra-specific divergence values of 0-2% also confirmed the genetic identity of D. rigida species. Paracyclopina nana was selected as an out group displayed a diverged array. The present results distinctly differentiated D. rigida from other Oithona species.
This study elaborates the preliminary information on the meiofaunal assemblage pattern in the Krossfjorden system of the Svalbard Archipelago based on the samples collected during the Summer Phase ...Indian Arctic Expeditions of 2017 and 2018. The results from the study divulged the meiofaunal assemblage pattern. It is diversified with the presence of ten meiofaunal groups represented by Foraminifera, Tintinnida, Nematoda, Polychaeta, Copepoda, Kinorhyncha, Tanaidacea, Ostracoda, Acarina and Priapulida larvae. Meiofaunal abundance was observed to be low during the year 2018 (5646 ± 874 ind./10 cm
2
) compared with previous reports from adjacent fjord systems and the samples collected during the 2017 study (8826 ± 1501 ind./10 cm
2
). The decrease in meiofaunal assemblage in the fjord is associated with changes in environmental constraints and organic matter availability. The diminishing sea ice habitats in the Arctic waters are expected to have pronounced impacts on meiofaunal communities and their appearances in the coming future. In this regard, data gathered during the present study will form a baseline information on meiofaunal communities in the Krossfjorden system for understanding future changes in the benthic habitat and have important implications on predicting the direction of change with regard to meiobenthic productivity.
This study presents the structural characteristics of Cochin mangroves in Kerala for proposing suitable management and rejuvenation measures of degrading mangrove habitats. The floristic diversity of ...mangroves revealed 14 species of true mangroves belonging to six families. Multivariate analysis of true mangroves belonging to selected mangrove forests of the study area based on density could be classified into four floristic groups, a water front or low–tide zonation, mid-tide preferring species, high tide and landward zonation. Shannon Weiner index of the three stations revealed that Site I was having higher value (H′ = 2.66) followed by Site II (H′ = 2.01) and Site III (H
′
= 1.595). The density of the mangroves varied significantly with sites and species (Global R = 0.537,
P
< 0.001). The diameter at breast height (DBH) in the study area revealed that most of the species came under 1–10 cm DBH class. The overall structural data (including Importance Value Index, DBH and basal area) showed that Site III, the Mangalavanam forest was having more structural development and could be considered as matured forest whereas, Site I, Aroor is a maturing forest and Site II, Malippuram is the least matured forest from the study. The Importance Value Index and basal area of each species could be used for analysing the maturity of the forest and habitat preferences for restoration programmes of the degraded ecosystems.
The current study is based on benthic samples collected as a part of the Indian Arctic Expedition, from eight stations of varying depths (29 m–292 m). The study focused on the community pattern of ...macrobenthos in the inner and outer fjord areas of Kongsfjord, with an emphasis on the bivalve community and the main factors affecting its distribution. The macrofaunal community was mainly composed of foraminiferans, nematodes, polychaetes, gastropods, bivalves, ostracods, copepods, amphipods and fish larvae. As most of the macrofaunal taxa were less sensitive to glacial-derived sedimentation process, their abundance was higher towards the inner fjord areas. Among the major taxa 14 species of foraminiferans, 18 species of nematodes, 8 species of polychaetes and 19 species of bivalves were identified. Across the entire study area, the bivalve Yoldiella sp. (15%) had the highest relative abundance. There is significant variation in the diversity and distribution of bivalves in the outer and inner fjord. The spatial distribution of bivalves showed that, stations 3, 4 and 5 had the highest numerical abundance compared to other. The canonical correspondence analysis (CCA) revealed that faunal distribution is mainly influenced by depth, salinity, sediment granulometry, and organic carbon content.
The Cochin estuarine system (CES) has experienced rapid changes over the last few decades from extensive urbanisation, industrialisation, agricultural development activities and aquaculture ...practices. Intense pollution and other anthropogenic disturbances have led to an accelerated increase in organic matter (OM) and dissolved inorganic nitrogen (DIN) in the estuarine complex. This study explores nitrous oxide (N2O) fluxes and its drivers in the CES. Relatively higher N2O concentrations were observed in the inner estuary when compared to the outer estuary. Higher DIN with varying salinity gradients likely controlled the production and flux of N2O into the inner portions of the system. Hypoxia was never established in the water column indicating that conditions were favourable for nitrification, which in turn possibly led to increased N2O concentrations. It was observed particularly during the monsoon season that the inorganic nutrients and dissolved greenhouse gases from the river Periyar at the head of the estuary, contributed to the increased N2O concentrations. The N2O water to air flux ranged from 0.49 to 29.73μmol m−2 day−1, which was higher than what was documented in earlier reports. Although the CES exports a substantial amount of nutrients to the adjacent Arabian Sea, the estuary effectively processes nitrogen inputs as N2O making CES a net source of N2O emissions.
•Anthropogenic activities have accelerated the nitrogen loading in the estuary.•Enriched nitrogen has led to higher nitrous oxide concentrations and emissions.•Thereby estuary significantly contributing to atmospheric nitrous oxide concentrations.
Estuaries are dynamic ecosystems that warrant detailed examination of trophic interactions due to diversified prey items contributed simultaneously from marine and freshwater environments. Most ...coastal and estuarine fisheries resources are either fully exploited or overexploited due to the involvement of increased number of fishermen, employment of more efficient fishing gears and adoption of mechanization. The present study elucidates trophic level status of fish resources exploited from Vembanad lake, S. India as an indicator of fishery-induced impacts in food web structure and thereby delineating its usefulness in describing the state of fisheries in this ecologically fragile ecosystem. Results showed that fishery resources of Vembanad lake has dwindled considerably from 115 species contributing 3068.29 tonnes during 1987–1988 to 80 species constituting 1192 tonnes during 2012–2013. The species richness has reduced to 3.78 in latter period from 6.40 in former period. A perceptible variation in composition of trophic groups was also observed in exploited fishery resources of the two periods. The number of species representing herbivores–omnivores–detritivores (Trophic Level-2.0-2.99) reduced from 31 to 28, mid-level carnivores (Trophic Level-3.0-3.99) from to 66 to 43 and the same of high-level carnivores from 18 to 9 species. Chi-square test revealed significant (p<0.05) difference in reduction of both mid-level carnivores and total species exploited from the lake. Large marine migrant predators, which showed pre-dominance during 1987–1988, declined along with a significant influx of freshwater and lower trophic fishes in fish catch of 2012-13. The significant reduction in the diversity of fishes represented in exploited fishery bring about theories like ‘fishing down the food web’ and ‘top down effect’ and change in ecology of the lake. These ecological changes are brought about by a combination of natural as well as anthropogenic causes which demand continuous monitoring of fish catch in order to ascertain the ecosystem health of Vembanad lake.
Approximately 15% of the world's wetlands are rice fields, vital in providing food for 40% of the human population. Due to farming practices-induced habitat disturbances, rice cultivation acts as a ...habitat filter that retains only taxa possessing specific traits to overcome the constraints. Being aquatic biota, benthic macroinvertebrates are also impacted by the intermittent presence of water in rice fields. The biological traits and trait combinations of benthic macroinvertebrates enabling their existence during the rice cultivation cycle in seasonal rice fields of Maranchery Kole (The Ramsar site Vembanad Kole wetland’s part) were studied. Based on the literature, 63 categories of 11 biological traits assignable at the genus level were used to characterize benthic macroinvertebrates. The taxa by traits data matrix was subjected to Gower's distance‐based hierarchical agglomerative cluster analysis to categorize faunal groups with similar trait assembly. According to the abundance weighted trait modality scores, the predominant traits were small body size, life duration of more than 1 year, multivoltine life cycle, aquatic larval stage, aquatic passive dispersal, cocoons as resistant form, locomotion by full water swimming, tegumental respiration, asexual reproduction, detritus as food and deposit-feeding. Trait-based classification of taxa resulted in 5 clusters. Characteristic trait combinations in each cluster particularly those beneficial for survival in unstable lentic freshwaters enabled the existence of taxa. Cluster I, the most abundant group (oligochaetes), was benefited from trait combinations including resistance forms to survive the intermittent presence of water in rice fields. Asexual reproduction and early onset of reproduction ensured their higher abundance from the transplanting phase. Detrital feeding also facilitated their rapid buildup in newly flooded fields rich in decomposing detritus. Cluster groups II and III, actively flying colonists characterized by competitive traits like predation, were more in tillering and preharvest phases. Apart from resistant and resilient traits ensuring survival in the temporary and disturbed habitat, exclusive trait combinations favored the faunal groups through different phases.
Chaetoceros calcitrans is widely present as a dominant marine diatom in estuarine and coastal waters and therefore a potential target to the toxicity effects exerted by trace metals. Copper induced ...changes in growth and chlorophyll content in C. calcitrans were analysed. At all the concentrations above 320 μg/L, the pro-oxidant copper caused a significant decrease in growth rate and chlorophyll concentration. The 96 h IC50 value of copper based on percentage growth inhibition of C. calcitrans was 450 μg/L. Copper concentration in the ambient water ranged from 2.38 to 608 μg/L. The kinetics of copper accumulation in intracellular and extracellular compartments of the cells were determined and correlated with the corresponding antioxidant enzyme activity (catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase) on exposure to 50, 180 and 450 μg Cu/L for 168 h. Copper adsorption to binding sites on the cell surface is relatively fast but further uptake into the cell is slow and considered as the rate limiting step. At sublethal concentrations as 50 and 180 μg/L, intracellular accumulation of copper increased linearly over 168 h. The intracellular accumulation of copper showed significant positive correlation (p<0.05) with catalase (CAT) and superoxide dismutase (SOD) activity when exposed to 50, 180 and 450 μg/L. The reduction in the CAT and SOD activity on prolonged exposure to 450 μg/L could be due to inactivation of enzyme as a result of higher reactive oxygen species (ROS) production. The extended period of exposure as in the present study resulted in sufficient accumulation of copper to activate CAT and SOD activity. The transient reduction in GR activity at 450 μg/L could be due to the inactivation of enzyme by copper. The results suggest that slower uptake together with an efficient antioxidant system is to some extend contributes to the tolerance of the species to copper.
•In Chaetoceros calcitrans, copper adsorption to cell surface binding sites is relatively fast but further uptake into the cell is slow.•At sublethal concentrations the intracellular copper concentration increased linearly over the exposure period.•To induce antioxidant enzyme activity, the intracellular concentration has to reach a threshold level in C. calcitrans.•The catalase and superoxide dismutase are the important antioxidant enzymes produced due to accumulation of copper inside the cell.
The functional feeding groups of macrobenthos in the Kodungallur–Azhikode estuary were studied on a monthly basis for a two year period (2009–2011). The main aim of the study was to understand the ...distribution pattern of macrobenthic functional feeding groups and their relationship to environmental drivers in the estuary. Malacostracan crustaceans dominated the system (60%) by numerical density, while molluscs contributed significantly to macrobenthic biomass (63%). Many species exploit the same class of resources within an assemblage of macrofaunal groups. The suspension feeding corophiid amphipod Americorophium triaeonyx was the most represented macrofaunal species. Other dominant macrofaunal feeding groups were the suspension feeding hydroid colonies of Obelia bidentata, surface deposit feeding polychaetes Prionospio cirrifera, suspension feeding mussels Arcuatula senhousia, carnivorous isopods Cirolana fluviatilis and sub-surface deposit feeding polychaetes Capitella sp. The sampling stations were compared using taxonomic distinctness (AvTD), and variations in taxonomic distinctness (VarTD), the values of AvTD and VarTD for all stations during the entire monthly survey fell within the confidence intervals of probability funnel (95%, p<0.05). However, a significant variation was noticed in the values between stations (AvTD: F (6,161) = 3.105, p=0.007; VarTD: F (6,161) = 2.489, p=0.025). The abundance biomass curves were plotted separately for each site as well as combined for the entire estuary. The relatively high negative trend was observed in the station 5 (W=−0.139) which indicates potential for the relatively high disturbance among all other stations. However, the W-value for the entire estuary was -0.079, which depicted moderate disturbance.
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