Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 16 de 16
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Mar Environ Res ; 196: 106380, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38341980

RESUMO

The largest continental shelf Oxygen Minimum Zone (OMZ) in the world is formed along the Indian western shelf in the eastern Arabian Sea during the Southwest Monsoon [(SWM); June-September], which is a natural pollution event associated with the coastal upwelling. This study examines the composition, abundance, and distribution of copepods during the Northeast Monsoon [(NEM); November to February] and SWM in 50 m depth zones along the Indian western shelf in the eastern Arabian Sea. The NEM was characterised by warm, stratified, and low-salinity waters in the southeast Arabian Sea and cold, high-salinity, and well-mixed waters in the northeastern Arabian Sea. During the SWM, cold and Dissolved Oxygen (DO) deficient waters (<22 µM/0.5 ml L-1), which are the signs of coastal upwelling, were evident all along the study zone, but with more intensity off Kochi, Mangalore, and Goa in the south than off Mumbai and Okha in the north. The zooplankton total biomass and abundance showed seasonality with a general decrease during the SWM (av. 3.68 ± 1.29 ml m-3 and av. 5711 ± 3096 Ind. m-3, respectively) compared to the NEM (av. 7.37 ± 2.17 ml m-3 and av. 14,473 ± 4966 Ind. m-3, respectively). At the same time, the abundance of Polychaeta and Siphonophora showed an increase during the SWM (av. 1187 ± 1055 Ind. m-3 and av. 169 ± 119 Ind. m-3, respectively), probably a result of the DO deficient waters associated with upwelling. Two striking seasonal features in Copepoda community were evident in this study: (a) a compositional shift from Cyclopoida dominant during the NEM to Calanoida dominant during the SWM, and (b) the coastal OMZ along the Indian western shelf during the SWM was dominated by Calanoida, which include oceanic OMZ species such as Pleuromamma indica, Lucicutia flavicornis, L.paraclausii, Eucalanus elongatus, Subeucalanus pileatus, S.subcrassus, and Clausocalanus furcatus. This forms a clear imprint for the extension of the oceanic OMZ into nearshore waters during the SWM due to coastal upwelling.


Assuntos
Copépodes , Animais , Oxigênio , Oceanos e Mares , Biomassa , Índia , Estações do Ano , Água do Mar
2.
Environ Monit Assess ; 195(7): 900, 2023 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-37380928

RESUMO

The Vembanad Lake and its associated low-lying areas and network of canals (hereafter VBL) form the major part of India's second-largest Ramsar wetland (1512 km2) located in Kerala State along India's southwest coast. The extensive VBL has a large fishery, inland waterways, and popular tourist attractions that support the livelihoods of thousands of people. Over the last several decades, the proliferation of water weeds in the VBL has alarmingly increased, causing many adverse ecological and socioeconomic effects. This study based on a review and synthesis of long-term data introduced the environmental and human dimensions of water weed proliferation in the VBL. Eichhornia (= Pontederia) crassipes, Monochoria vaginalis, Salvinia molesta, Limnocharis flava, Pistia stratiotes, and Hydrilla verticillata are the most troublesome water weeds in the VBL, with the first three being the most widespread. They were mostly imported to India long ago before becoming a part of the VBL. These weeds harmed water quality, waterways, agriculture, fisheries, disease vector management, as well as the vertical and horizontal shrinkage of the VBL through increased siltation and faster ecological succession. The inherently fragile VBL was harmed by extensive and long-term reclamation, the construction of saltwater barrages, and many landfill roads that crisscross water bodies serving as coastal dams, creating water stagnation by blocking natural flushing/ventilation by periodic tides from the adjacent southeastern Arabian Sea. These ecological imbalances were exacerbated by excessive fertiliser use in agricultural areas, as well as the addition of nutrient-rich domestic and municipal sewage, which provided an adequate supply of nutrients and a favourable habitat for the expansion of water weeds. Furthermore, because of recurrent floods and a changing ecology in the VBL, the water weed proliferation has become a more significant problem, with the potential to disrupt their current distribution pattern and spread in the future.


Assuntos
Lagos , Áreas Alagadas , Humanos , Animais , Monitoramento Ambiental , Agricultura , Proliferação de Células
3.
Environ Monit Assess ; 194(4): 303, 2022 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-35348892

RESUMO

Eichhornia crassipes and Monochoria vaginalis are waterweeds, and their uncontrolled proliferation in fresh and brackish water habitats is a serious ecological problem in many parts of the world. These weeds are quite common in the Vembanad Lake System (VLS), India's second-largest Ramsar wetland. During the non-monsoon season, the Thannermukkom saltwater barrage divides the VLS into two zones: saline water downstream and freshwater upstream. The field sampling of the current study was carried out in the upstream zone of the VLS during the Pre-Monsoon (March 2017). Fresh Eichhornia and Monochoria samples were collected, transported to the lab, and experiments were conducted under natural light conditions to determine how much extra water they transpire into the atmosphere. The results showed that the water loss in experimental tanks with Eichhornia (evapotranspiration) is roughly twice that in control tanks without them (only evaporation). Monochoria transpires fairly more water to the atmosphere than Eichhornia. These results reveal that the proliferation of waterweeds has a significant adverse effect in conserving water in all freshwater bodies infested with them. The current study also points out that the expansion of waterweeds has the potential to worsen drought conditions as they cause excess water loss into the atmosphere and a faster drying up of freshwater reservoirs. Two possible approaches for managing the waterweeds in the VLS include reducing nutrient loading upstream and more frequent opening of the Thannermukkom saltwater barrage to allow saltwater intrusion, which could inhibit the growing waterweeds.


Assuntos
Monitoramento Ambiental , Lagos , Proliferação de Células , Ecossistema , Monitoramento Ambiental/métodos , Áreas Alagadas
4.
Mar Pollut Bull ; 177: 113529, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35278904

RESUMO

This baseline study on microplastics (MPs) in calanoid copepods in the Kochi backwaters (KBW), India's largest estuary system on the west coast, focuses on (a) the spatiotemporal variations of MPs with the seasonal hydrography setting, and (b) how man-made flow restrictions of a large saltwater barrage contribute to MPs in copepods and their potential to transfer to higher trophic levels. This study found that MPs in copepods in the KBW ranged from av. 0.01 ± 0.014 to 0.11 ± 0.03 no./ind. seasonally. When the saltwater barrage shutters were fully/partially closed during the Pre-monsoon/Northeast Monsoon, MPs in copepods were considerably larger (av. 0.11 ± 0.03 no./ind., and av. 0.075 ± 0.02 no./ind., respectively) as compared to the Southwest Monsoon (av. 0.03 ± 0.01 no./ind.), when the barrage shutters were fully open. This shows the potential of man-made flow restrictions to increase the bioconcentration of MPs in copepods and their possible transfer to higher trophic levels through the food chain, adding to the region's previous discovery that much higher trophic level resources are polluted with a high concentration of MPs.


Assuntos
Copépodes , Poluentes Químicos da Água , Animais , Monitoramento Ambiental , Estuários , Humanos , Índia , Microplásticos , Plásticos , Poluentes Químicos da Água/análise
5.
Mar Pollut Bull ; 173(Pt B): 113042, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34655907

RESUMO

The baseline study of Microplastics (MPs) in zooplankton (copepods, chaetognaths, decapods, and fish larvae) from six different zones along India's west coast (off Kanyakumari/Cape Comorin, Kochi, Mangalore, Goa, Mumbai, and Okha) in the Eastern Arabian Sea (EAS) is presented here with their vast ecosystem impacts. This investigation revealed that zooplankton in all six zones accumulated MPs pellets (52.14%), fibres (28.40%), films (10.51%), and fragments (8.95%). The highest average retention of MPs (MPs/individual) was found in fish larvae (av. 0.57 ± 0.18) while copepods had the lowest (av. 0.03 ± 0.01). The presence of low-density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate was confirmed by Raman Spectra of MPs. The MPs in zooplankton found in this study (av. 22 ± 7 pieces/m3) were nearly 2-fold greater than those found in some of the world's most densely populated areas. It is shown that the strong southerly coastal currents could advect the MPs contaminated water mass too far away, having the potential to affect the fish and corals.


Assuntos
Antozoários , Poluentes Químicos da Água , Animais , Ecossistema , Monitoramento Ambiental , Microplásticos , Plásticos , Poluentes Químicos da Água/análise , Zooplâncton
6.
Mar Pollut Bull ; 168: 112447, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33971453

RESUMO

This study in the Kochi backwaters (KBW) presents the distribution of 9 trace metals (Fe, Zn, Cu, Mn, Ni, Co, Cr, Cd, Pb) in different parts (root, stolon and leaf) of the common water hyacinth Eichhornia crassipes during three different seasons [Pre-Monsoon (PRM), Southwest Monsoon (SWM), and Northeast Monsoon (NEM)]. The hyacinth was collected from 4 sections upstream of the KBW where a saltwater barrage [Thannermukkom Barrage (TB)] prevents saltwater intrusion. Results showed that regardless of seasons, all the trace metals concentration in different parts of Eichhornia varied in the following order: roots > stolon > leaves. All the trace metals except Fe showed their highest concentration during the PRM when TB introduces stagnancy of the water upstream through flow restrictions. Instead, Fe was high during the SWM associated with increased river influx at that time. Overall results showed that the hydrographical alterations of TB upstream of KBW have clear imprints on the trace metals concentrated in the hyacinth Eichhornia crassipes.


Assuntos
Eichhornia , Metais Pesados , Oligoelementos , Poluentes Químicos da Água , Índia , Metais Pesados/análise , Poluentes Químicos da Água/análise
7.
Mar Pollut Bull ; 160: 111568, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32853836

RESUMO

This study delineates the impact of a man-made hydrological barrage [Thannermukkom barrage (TB)] on the concentration of selected trace metals (Fe, Zn, Cu, Co, Cr, Mn, Ni, Pb) in mesozooplankton from the Kochi backwaters (KBW). The overall results point out that during Pre-Southwest Monsoon (PRM), the concentration of trace metals in mesozooplankton was high in the upstream due to the closure of the barrage, which essentially causes stagnancy of the waters. Trace metal concentrations in the downstream and upstream regions of KBW were found to be lower during Post- Southwest Monsoon (PSWM) compared to the rest of the seasons. In general, trace metals in mesozooplankton from the KBW showed the following order of concentration: Fe > Mn > Zn > Ni > Cu > Cr > Co > Pb. A comparison with earlier data across the globe showed that trace metal concentration in mesoplankton in the KBW is lower than the values reported from other parts of the world.


Assuntos
Metais Pesados , Poluentes Químicos da Água , Monitoramento Ambiental , Sedimentos Geológicos , Índia , Metais/análise , Metais Pesados/análise , Poluentes Químicos da Água/análise
8.
Environ Monit Assess ; 192(2): 107, 2020 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-31927668

RESUMO

Cladocerans are ecologically important as active grazers at the secondary trophic level, and they are economically important in aquaculture as potential live feed for many commercially valuable fishes. This study deals with the effect of salinity on grazing of the rare cladocera Latonopsis australis. The experimental specimens were collected from the lower reaches of the Kochi backwaters, the largest estuarine system along the west coast of India, during the Pre-Southwest Monsoon (May 2015), and their cultures developed in the laboratory. Eight experimental salinity treatments (freshwater, 2, 4, 6, 8, 10, 12 and 14 salinity) with three life phases of the specimens (phase I: neonates with a developed digestive tract, phase II: adults carrying egg and phase III: adults carrying developing neonates) were carried out to measure their grazing rates. Two different approaches, namely individual-specific and biovolume-specific grazing measurements, were adopted in the study. The results showed a significant influence of salinity on the size and grazing rates of L. australis, irrespective of their life phases. Filtration and ingestion rates of the specimens also varied significantly between different life phases with the lowest rates in phase III. Irrespective of the life phases, grazing rates were the highest in freshwater conditions, which decreased to 25-84% in medium salinity (4-8) and 65-93% in high salinity (10-14). Further, the study demonstrated that size/biovolume/weight-based quantification of cladocera grazing provides a more precise method for the estimation of feeding rates compared to the individual-basic approach. This study emerges as the first attempt to quantify the grazing measurements of a cladocera from Indian waters.


Assuntos
Cladocera , Comportamento Alimentar , Animais , Monitoramento Ambiental , Água Doce , Índia , Salinidade
9.
Sci Rep ; 8(1): 11282, 2018 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-30050043

RESUMO

An interesting physiological response of phytoplankton to large fluctuations in underwater photosynthetically active radiation (PAR) levels in the northern Bay of Bengal has been presented here. This study is primarily based on a 12-day time series observation in the northern Bay of Bengal during the peak Southwest Monsoon (July 2012), when the study region was recurrently exposed to alternating cloudy and sunny sky conditions. On overcast days, the PAR available underwater at the time series location (TSL) drastically decreased, with the noontime PAR at the surface water (2 m) usually being ~600 µmol m-2 s-1 on sunny days and declining to ~50 µmol m-2 s-1 on heavily overcast days. Closely linked with the sunny and cloudy days at TSL, chlorophyll a concentration in the water column showed noticeable features; it increased in the upper water column (surface-40 m) and decreased in the lower water column (41-80 m) on cloudy days, while the reverse was the case on sunny days. Based on in-situ and laboratory experimental data, it was observed that these temporal changes in the vertical distribution of chlorophyll a in the northern Bay of Bengal were due to the short-term physiological acclimation of phytoplankton to large changes in underwater PAR.

10.
Environ Monit Assess ; 190(5): 295, 2018 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-29675726

RESUMO

The distribution ecology of microzooplankton in the Kochi (Cochin) backwaters has been presented. Emphasis has been given to the micro-rotifers present in the environment, considering they were a hitherto ignored component of the microzooplankton in the past studies. Three seasonal samplings were carried out at six locations along the salinity gradients in the Kochi backwaters during the Pre-Monsoon (March), Southwest Monsoon (August), and Northeast Monsoon (December). A total of 48 species of microzooplankton were recorded, of which 35 were ciliates, 10 were rotifers, and 3 were heterotrophic dinoflagellates. The study also reports the swarm of a microzooplankton species from the Kochi backwaters, which was formed by a tintinnid ciliate, Tintinnopsis uruguayensis, during the Northeast Monsoon. Very high microzooplankton density (11,990 No. L-1), as swarm in the downstream location was associated with the mesohaline condition and high availability of food. Rotifers were the major component of microzooplankton in the limnohaline/oligohaline region, whereas ciliates dominated in the polyhaline/mesohaline region. Hence, in the present study, salinity appeared to be a major factor affecting the composition of the microzooplankton community in the Kochi backwaters. As rotifers have a wide food spectrum, they can feed on almost all components of the microbial food web, including small ciliates. They also share the same food spectrum with larger ciliates and crustacean nauplii. The present study, for the first time, recorded the importance of rotifers in the microzooplankton community in the plankton food web in the Kochi backwaters.


Assuntos
Monitoramento Ambiental , Estuários , Cadeia Alimentar , Rotíferos/fisiologia , Animais , Cilióforos , Crustáceos , Dinoflagellida , Índia , Plâncton/fisiologia , Salinidade , Estações do Ano
11.
Sci Rep ; 8(1): 2544, 2018 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-29416064

RESUMO

Considering Alappuzha Mud Bank in the southern Kerala coast as a typical case of biologically productive Mud Banks that form along the southwest coast of India during the Southwest Monsoon (June - September), the present study addresses several pertinent missing links between the physical environment in Mud Banks and their influence on plankton stock. This study showed that very strong coastal upwelling prevails in the entire study domain during the Southwest Monsoon, which manifests itself in the form of significantly cool, hypoxic and nitrate-rich waters surfacing near the coast. The upwelled water persisting throughout the Southwest Monsoon period was found to have fuelled the exceptionally high phytoplankton stock in the entire study area, including the Mud Bank region. Having accepted that Mud Banks are special because of the calm sea surface conditions and relatively high turbidity level in the water column around them, the present study showed that except at points close to the sea bottom, turbidity level in the Alappuzha Mud Bank was below the critical level to inhibit the plankton stock. The suspended sediments that form in the Mud Bank occasionally could be attributed to the disturbance of the bottom fluid muddy layer and their vertical spurts.

12.
Environ Monit Assess ; 189(10): 503, 2017 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-28894990

RESUMO

Results of the experimental studies on the feeding habit and daily ration (DR) of 12 dominant copepods from a tropical coastal water (off Kochi, Southwest coast of India) on different food items (phytoplankton, rotifers, and detritus) are presented. Even though, all species of copepods consumed all types of food items in the experiments, they showed noticeable feeding preferences, having important ecological implications. Calanoid Paracalanus parvus and Acrocalanus gracilis consumed phytoplankton and rotifers equally in mono diets (74-89% of DR) and mixed diets (53-82% of DR), which indicated their ability to shift their diet in natural environment based on the availability of food items. Calanoid Acartia erythraea and A. danae consumed more phytoplankton (DR 83 and 72%, respectively) than rotifers (DR 51 and 46%, respectively) in mono diets, and in mixed diets, their consumption was high in phytoplankton combined food mixtures (P + R DR and P + D DR) rather than the R + D food type, indicated their preference for mixed diets of phytoplankton. Similarly, Calanoid Temora turbinata, Pseudodiaptomus serricaudatus, and Centropages tenuiremis preferred a herbivorous diet as evidenced by their high ingestion rate on phytoplankton mono (70 to 87% to their DR) and mixed diets (58 to 80% of DR). On the other hand, Cyclopoid Oithona similis and Poecilostomatoid Corycaeus danae preferred a carnivorous diet, consuming more rotifers (> 80% of DR) than phytoplankton (18-20% of DR) and detritus (5-6% of DR). Harpacticoids Macrosetella gracilis and Euterpina acutifrons equally preferred phytoplankton (78-92% of DR) and detritus (65-89% of DR). The study showed that the dominant copepods in the coastal waters off Kochi occupy different trophic niches available in the environment, which may be applicable in other similar environments as well.


Assuntos
Copépodes/fisiologia , Dieta , Monitoramento Ambiental/métodos , Preferências Alimentares , Fitoplâncton , Rotíferos , Animais , Ingestão de Alimentos/fisiologia , Índia , Oceanos e Mares , Especificidade da Espécie , Clima Tropical
13.
Environ Monit Assess ; 189(7): 351, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28646438

RESUMO

The relative grazing impact of Noctiluca scintillans (hereafter referred only Noctiluca) and copepods (Acrocalanus gracilis, Paracalanus parvus, Acartia danae and Oithona similis) on the phytoplankton community in an upwelling-mudbank environment along the southwest coast India is presented here. This study was carried out during the Pre-Southwest Monsoon (April-May) to the Late Southwest Monsoon (August) period in 2014. During the sampling period, large hydrographical transformation was evident in the study area (off Alappuzha, Southwest coast of India); warmer Pre-Southwest Monsoon water column condition got transformed into cooler and nitrate-rich hypoxic waters during the Southwest Monsoon (June-August) due to intense coastal upwelling. Copepods were present in the study area throughout the sampling period with a noticeable increase in their abundance during the Southwest Monsoon. On the other hand, the first appearance of Noctiluca in the sampling location was during the Early Southwest Monsoon (mid-June) and thereafter their abundance increased towards the Peak Southwest Monsoon. The grazing experiments carried out as per the food removal method showed noticeable differences in the feeding preferences of Noctiluca and copepods, especially on the different size fractions of phytoplankton. Noctiluca showed the highest positive electivity for the phytoplankton micro-fraction (av. 0.49 ± 0.04), followed by nano-fraction (av. 0.17 ± 0.04) and a negative electivity for the pico-fraction (av. -0.66 ± 0.06). In total ingestion of Noctiluca, micro-fraction contribution (83.7%) was significantly higher compared to the nano- (15.7%) and pico-fractions (0.58%). On the other hand, copepods showed the highest positive electivity for the phytoplankton nano-fraction (av. 0.38 ± 0.04) followed by micro- (av. -0.17 ± 0.05) and pico-fractions (av. -0.35 ± 0.05). Similarly, in total ingestion of copepods, nano-fraction (69.7%) was the highest followed by micro- (28.9%) and pico-fractions (1.37%). The grazing pressure of Noctiluca on the total phytoplankton was found to be 27.7% of the standing stock and 45.6% of the production, whereas in the case of copepods, it was 9.95% of the standing stock and 16.6% of the production. The study showed that the grazing pressure of Noctiluca on the total phytoplankton as well as larger phytoplankton fraction was 2.8- and 8-folds higher than that of the copepods. This suggests the leading role of Noctiluca as an effective grazer of larger phytoplankton along the southwest west coast of India, especially during the Peak/Late Southwest Monsoon.


Assuntos
Copépodes/fisiologia , Dinoflagellida/fisiologia , Monitoramento Ambiental , Fitoplâncton/fisiologia , Animais , Biomassa , Comportamento Alimentar , Água Doce , Índia , Nitratos/análise , Estações do Ano , Água do Mar
14.
Mar Pollut Bull ; 121(1-2): 201-215, 2017 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-28602311

RESUMO

Trichodesmium is a bloom-forming, diazotrophic, non-heterocystous cyanobacteria widely distributed in the warmer oceans, and their bloom is considered a 'biological indication' of stratification and nitrogen limitation in the ocean surface layer. In the first part of this paper, based on the retrospective analyses of the ocean surface mesoscale features associated with 59 Trichodesmium bloom incidences recorded in the past, 32 from the Arabian Sea and the Bay of Bengal, and 27 from the rest of the world, we have showed that warm-core features have an inducing effect on bloom formation. In the second part, we have considered the environmental preferences of Trichodesmium bloom based on laboratory and field studies across the globe, and proposed a view about how warm-core features could provide an inducing pre-requisite condition for the bloom formation in the Arabian Sea and the Bay of Bengal. Proposed that the subsurface waters of warm-core features maintain more likely chances for the conducive nutrient and light conditions required for the triggering of the blooms.


Assuntos
Temperatura , Trichodesmium , Baías , Cianobactérias , Oceanos e Mares , Dinâmica Populacional , Estudos Retrospectivos , Água do Mar
15.
Environ Monit Assess ; 189(3): 105, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28205106

RESUMO

The grazing rate of copepods on the total and size-fractionated phytoplankton biomass in a coastal environment (off Kochi, southwest coast of India) were measured during pre-monsoon (PRM), peak southwest monsoon (PKSWM), late southwest monsoon (LSWM) and post-southwest monsoon (PSWM). The phytoplankton standing stock (chlorophyll a-Chl. a) and growth rate (GR) were less during the PRM (Chl. a 0.58 mg m-3; GR 0.23 ± 0.02) and PSWM (Chl. a 0.89 mg m-3; GR 0.30 ± 0.05) compared to PKSWM (Chl. a 6.67 mg m-3; GR 0.43 ± 0.02) and LSWM (Chl. a 4.09 mg m-3; GR 0.40 ± 0.04). The microplankton contribution to the total Chl. a was significant during the PKSWM (41.83%) and LSWM (45.72%). Copepod density was lesser during the PRM (1354 No m-3) and PSWM (1606 No m-3) than during PKSWM and LSWM (4571 and 3432 No m-3, respectively). Seasonal changes in phytoplankton biomass, phytoplankton size structure, and copepod community were closely related to the hydrographical transformations in the study domain. Dominant calanoid copepods in the study region ingested 8.4 to 14.2% of their daily ration from phytoplankton during the PRM and PSWM, which increased to >50% during the PKSWM and LSWM. The cyclopoid Oithona similis was abundant during the PKSWM, ingesting only 21% of their daily ration from phytoplankton. Temporal variation in the phytoplankton biomass and copepod species composition caused differences in community level top-down control. The copepod community ingestion on phytoplankton was high during the LSWM (18,583 µg C m-3d-1), followed by PKSWM (9050 µg C m-3d-1), PSWM (1813 µg C m-3d-1), and PRM (946 µg C m-3d-1). During the low Chl. a period (PRM and PSWM), dominant calanoid copepods showed a positive selectivity for the micro- and nano-phytoplankton size fractions, whereas during the high Chl. a period (PKSWM and LSWM), they showed a positive selection for nano-phytoplankton fractions. Irrespective of the seasons, dominant calanoid copepods showed a negative selection of pico-phytoplankton fraction. The cyclopoid O. similis and Poecilostomatoid Corycaeus danae showed a positive selection of nano- and pico-phytoplankton fractions rather than micro-fraction. The grazing pressure of copepod community ingestion on micro-fraction was less (0.56% of the phytoplankton biomass and 1.06% of the phytoplankton production) during the PKSWM. This study provides, for the first time, clear findings on the seasonal variation in the top-down control of phytoplankton by copepods in a tropical coastal water ecosystem and discusses its implications on phytoplankton blooming, plankton food web, and biogeochemistry.


Assuntos
Copépodes , Ecossistema , Fitoplâncton/crescimento & desenvolvimento , Animais , Biomassa , Clorofila/análise , Clorofila A , Monitoramento Ambiental , Cadeia Alimentar , Índia , Plâncton , Estações do Ano , Água do Mar/química
16.
Environ Monit Assess ; 187(10): 643, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26403706

RESUMO

Latonopsis australis is a rare Cladocera inhabiting the entire stretch of the Cochin backwaters, the largest monsoonal estuary along the West Coast of India, during the summer monsoon, but restricted to the upper reaches during the non-monsoon periods. Here, we present the results of an experimental study, which assessed the influence of salinity on the life table demography of the species at different salinity levels. The life table demographic parameters such as net reproduction rate, generation time, intrinsic growth rate, gross reproductive rate, and survivorship of the species were measured in different salinities ranging from freshwater to mesohaline levels (salinity 14). The study showed that higher salinity had a significant negative effect on all life table demography parameters of the species, whereas freshwater to low saline conditions (salinity up to 8) favored the survivorship, life expectancy, net production, and growth rate. It was also noticed that salinity above 8 caused a significant decrease in the survivorship, life expectancy, and reproduction rate of the species, which clearly explained the seasonal distribution pattern of the species in the Cochin backwaters. The present study suggests salinity 2 to 6 as the optimum range for the large-scale production of L. australis for purposes like live feed in aquaculture.


Assuntos
Cladocera/crescimento & desenvolvimento , Monitoramento Ambiental/métodos , Água Doce/química , Água do Mar/química , Animais , Demografia , Estuários , Índia , Tábuas de Vida , Reprodução , Salinidade , Estações do Ano , Cloreto de Sódio
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA