Somatic and population growth responses of Ceriodaphnia dubia and Daphnia pulex (Cladocera) to changes in food (Chlorella vulgaris) level and temperature

We quantified the combined effects of three food levels (0.01 x 10(6), 0.1 x 10(6) and 1.0 x 10(6) cells ml(-1)) and three temperature levels (15, 20 and 25 degrees C) on the somatic and the clonal population growth of two cladocerans Ceriodaphnia dubia and Daphnia pulex for 24 to 42 days. The somatic growth data showed that both the cladoceran species began to increase their body size within 3 days and remained stable beyond a week. Food density had a significant effect on the body size of C. dubia while for D. pulex, food level and temperature as well as their interaction had significant effect on the body size. The population growth of both the cladoceran species was affected by temperature. At 15 degrees C, C. dubia showed little growth at the highest food density, while at low food level, there was some increase in the population abundances, especially after a long lag phase of about 2 weeks. At 15 degrees C and under the lowest tested food level, the population of D. pulex did not increase beyond the inoculation density. Optimal population growth of D. pulex was observed at intermediate temperature and at 1.0 x 10(6) cells ml(-1) of food level while for C. dubia 25 degrees C and the highest food level yielded highest growth. At low food level and low temperature, the rate of population increase (r) of C. dubia was much lower than that of D. pulex at comparable conditions. On the hand, at higher food levels and temperature regimes, the r of D. pulex was much higher than that of C.dubia. Regardless of the food levels and temperature, the r of C. dubia varied from 0.03 to 0.07 while that of D. pulex varied from 0.01 to 0.08 day(1).     

Effects of temperature on testicular cycle of wild birds Black headed munia and Spotted munia

A long term investigation was made on the effects of temperature in the reproduction of tropical wild birds, Black headed munia, Munia malacca and Spotted munia, Lonchura punctulata. In Spotted munia delayed gonadal development as well as regression were observed in 12 degrees C treated group. In 20 degrees C treated birds the testicular volume was significantly less in the month of September and October and was significantly more in November compared to the corresponding control values. In 27 degrees C treated birds delay in testicular development was observed. In Black headed munia delayed gonadal development and regression was observed in 12 degrees C and 20 degrees C treated groups. But maximum gonadal development Delayed regression was also noticed in 20 degrees C group. In 27 degrees C treated group an inhibition of the testicular development was noticed during progressive phase (September). Present findings suggest that neither temperature nor continuous illumination could alter the circannual nature of testicular cycle in spotted munia indicating that temperature acts only as supplementary factor in the reproduction of these two bird models. We further suggest that temperature effects are mediated through changes in thyroxine levels.     

Effect of temperature on growth and reproduction of the epigeic earthworm,Eudrilus Eugeniae (Kinberg)

Influence of temperature on growth and reproduction of Eudrilus eugeniae has been investigated by laboratory culturing at regulated 25.0 degrees C, 30.0 degrees C, 37.5 degrees C and 40.0 degrees C and in fluctuating (22.7-27.3 degrees C) room temperature of prevailing (winter) season over 16 weeks. All worms died during first and tenth week at 40.0 degrees C and 37.5 degrees C respectively. Weight (biomass) and growth of worms cultured at different temperature varied significantly (P<0.01). The mean growth (mg/g live weight/day) at 25.0 degrees C., 30.0 degrees C, 35.0 degrees C, 37.5 degrees C and in fluctuating temperatures was 1,074.04 +/- 6.07, 1,554.01 degrees 192.37, 148.1 +/- 15.28, 192.83 +/- 25.8 and 1450.4 +/- 162.1 respectively. Growth declined after maturity drastically with coccon production. At 25.0 degrees C though worms are sexually mature, they failed to produce cocoons within 16 weeks whereas, at 35.0 degrees C and 37.5 degrees C they did not sexually mature. Worms attained sexual maturity at a mean weight of about 1000 mg/worm. The mean per cent maturity was higher and earlier in fluctuating temperatures and at 30.0 degrees C than at 25.0 degrees C. Cocoon production was observed only at 30.0 degrees C and in fluctuating temperatures with a mean of 0.9 and 1.5 cocoons/ wom/week and the cumulative cocoon number of 10.8 and 14.7/worm over 16th week respectively. The fluctuating temperature of uncontrolled room environment and 30.0 degrees C were favorable for various life activities of the worms. Eudrilus eugeniae appears to have range of temperature optima more than 25.0 degrees C and less than 28 degrees C. The climatic conditions prevailing in whole of the peninsular India during winter season are favourable for employing this worm in intensive field scale vermiculturing practices.     

Seasonal variations in zooplankton abundances in the Iturbide reservoir (Isidro Fabela, State of Mexico, Mexico)

This studywas undertaken to quantify the seasonal variations of zooplankton (rotifers, cladocerans and copepods) and selected physico-chemical variables (temperature, pH, conductivity, Secchi disc transparency, dissolved oxygen, ammonia, nitrate and phosphate concentrations) in the Iturbide dam. Monthly zooplankton samples (50 l filtered through 50 microm mesh, in duplicates from each of the 4 stations) were collected from February 2008 to January 2009. Simultaneously physico-chemical variables were measured. The zooplankton samples were fixed in 4% formalin in the field. In general, the temperature ranged from 9 to 16 degrees C, rarely exceeding 20 degrees C. Secchi transparency was nearly 100% since the reservoir was shallow (< 2 m) even during the rainy seasons. Dissolved oxygen was generally high, 13-18 mg l(-1). Nitrate levels (10 to 170 microg l(-1)) were low while phosphates were relatively high (9 to 35 microg l(-1)). The Iturbide reservoir was dominated by rotifer species. We encountered in all, 55 taxa of rotifers, 9 cladocerans and 2 copepods. The rotifer families Trichocercidae and Notommatidae had the highest number of species (7 each) followed by Colurellidae and Lecanidae (6 and 5 species, respectively). Trichocerca elongata, Ascomorpha ovalis, K. americana, K. cochlearis, Lepadella patella and Pompholyx sulcata were the dominant rotifers during the study period. On an annual average, rotifer density ranged between 50-200 ind.(-1). Among crustaceans Chydorus brevilabris and Macrothrix triserialis were most abundant. The maximal density of these cladocerans was about 50 ind. l(-1). Copepods were much lower in numbers (< 20 ind. l(-1)). In general the density of zooplankton was higher during summer months (April to July) than during winter. Shannon-Wiener diversity index varied from 1.0 to 4.3 depending on the site and the sampling period. Based on the data of Secchi transparency and nutrient concentrations, the Iturbide reservoir appeared to be mesotrophic.     

Effects of diazinon on serum calcium and inorganic phosphate levels as well as ultrastructures of parathyroid and calcitonin cells of Rattus norvegicus

Daily intramuscular administration of two doses--0.50 LD550 (150 mg/kg b w) and 0.75 LD50 (225 mg/kg b w) of diazinon for 14 days induced progressive hypocalcemia without altering serum inorganic phosphate value in Rattus norvegicus. Hypocalcemic response of the pesticide was dose- as well as time-dependent. Parathyroid chief cells of the experimental rats exhibited degranulation, vacuolation, loss of secretory granules and lipid droplets, decreased chromatin, and degenerative changes in endoplasmic reticulum, Golgi complex as well as cristae of the mitochondria. Not much of ultrastructural changes could be seen in the C cells of the rats treated with diazinon.     

Acquisition and loss of cold-tolerance in adult barnacles (Balanus balanoides) kept under laboratory conditions

In the laboratory, Balanus balanoides (L.) barnacles maintained without food at 5°C over the winter to summer period remained cold-tolerant. Winter animals maintained at 5°C and fed Artemia nauplii under a controlled light-dark regime until mid-summer lost this cold-tolerance. Summer animals, maintained without food at 5° or 15°C until midwinter, became cold-tolerant. Summer and winter animals subjected to increased (or decreased) ambient salinity for 48 h showed a small decrease (or increase) in their lower median lethal temperature (MLT—defined as the temperature at which 50% of the animals die after 18 h exposure to air). Summer animals subjected to desiccation for 48 h also showed a small decrease in their lower MLT. It is concluded that the seasonal changes in cold-tolerance of adult barnacles are probably induced by a combination of environmental factors including food availability, light intensity, day-length and changes in ambient sea-water temperatures. Development of cold-tolerance in the winter did not depend upon fertilisation. Changes in intra-cellular solute concentration which accompany adaptation to changes in ambient salinity or desiccation do not appear to be related to the seasonal changes in cold-tolerance.     

Some effects of temperature on the growth and metabolic rate of juvenile blue crabs,Callinectes sapidus,in the laboratory

Juvenile blue crabs, Callinectes sapidus Rathbun, were grown in the laboratory at different temperatures, and metabolic-rate determinations were made. Growth is shown to be dependent upon temperature. Crabs kept at high temperatures (34° and 27°C) grow faster than those kept at lower temperatures (13°, 15°, and 20°C). Increase in size per molt is less at higher temperatures than at lower ones. Mortality is directly proportional to temperature between 13° and 34°C and is very high during ecdysis at elevated temperatures. Metabolic rate increases with temperature, but various degrees of acclimation are seen after 4 weeks exposure. No acclimation of general activity to temperature was found. The findings are applied theoretically to crabs living in the region of heated discharge canals of electrical generators: the motile blue crab could extend its growing season without decreasing size at maturity by active selection of thermal surroundings.In part based on a thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science at the University of Florida, USA.     

Abundance and seasonal variations of phytoplankton in the creek waters of western mangrove of Kachchh-Gujarat

The phytoplankton was assessed quantitatively and qualitatively in regard to their abundance in creek waters at three sites along the western mangrove of Kachchh. In total one hundred and four species of phytoplankton were identified. Among them 82 species diatoms (Bacillariophyceae), 16 species dinoflagellates (Dinophyceae), 3 species blue greens (Cyanophyceae) and 2 species were green algae. The density in all the three sites varied from 94,166.67 to 2,44,500 cells l(-1). The salinity ranged from 36 to 44 per thousand, temperature 17 to 35 degrees C and pH ranged from 7 to 8.9 respectively. These semi arid zone mangrove creek area having high densities were recorded during monsoon and early winter season.     

Seed germination of three provenances of Pinus brutia (Ten.) as influenced by stratification, temperature and water stress

Seeds from three provenances of Pinus brutia were stratified for 0 or 45 d (days) at 4 +/- 1 degrees C and then germinated at 15 degrees C or 20 degrees C on filter paper saturated with polyethylene glycol solutions to provide water potentials of 0, -0.2 and -0.4 MPa (mega Pascal). Regardless of stratification, germination was lower at 15 degrees C than 20 degrees C for seeds of all provenances. Stratification significantly increased germination percentage at all water potentials regardless of the germination temperatures. Lowering the water potential to -0.4 MPa reduced germination for all three provenances in unstratified and stratified seeds when averaged for two temperatures, but reaction to the increased water stress was different among the provenances. Combined over two temperatures, stratified or unstratified seeds from the highest elevation (Cehennemdere) had the lowest germination performance at all water potentials, and stratified and nonstratified seeds from a coastal elevation (Silifke) had the highest germination parameters at the lowest water potential (-0.4 MPa). It might be concluded that seed germination and resistance to water stress vary according to provenance and stratification.     

Temperature influences carbon accumulation in moist tropical forests

Evergreen broad-leaved tropical forests can have high rates of productivity and large accumulations of carbon in plant biomass and soils. They can therefore play an important role in the global carbon cycle, influencing atmospheric CO2 concentrations if climate warms. We applied meta-analyses to published data to evaluate the apparent effects of temperature on carbon fluxes and storages in mature, moist tropical evergreen forest ecosystems. Among forests, litter production, tree growth, and belowground carbon allocation all increased significantly with site mean annual temperature (MAT); total net primary productivity (NPP) increased by an estimated 0.2-0.7 Mg C x ha(-1) x yr(-1) x degrees C(-1). Temperature had no discernible effect on the turnover rate of aboveground forest biomass, which averaged 0.014 yr(-1) among sites. Consistent with these findings, forest biomass increased with site MAT at a rate of 5-13 Mg C x ha(-1) x degrees C(-1). Despite greater productivity in warmer forests, soil organic matter accumulations decreased with site MAT, with a slope of -8 Mg C x ha(-1) x degrees C(-1), indicating that decomposition rates of soil organic matter increased with MAT faster than did rates of NPP. Turnover rates of surface litter also increased with temperature among forests. We found no detectable effect of temperature on total carbon storage among moist-tropical evergreen forests, but rather a shift in ecosystem structure, from low-biomass forests with relatively large accumulations of detritus in cooler sites, to large-biomass forests with relatively smaller detrital stocks in warmer locations. These results imply that, in a warmer climate, conservation of forest biomass will be critical to the maintenance of carbon stocks in moist tropical forests.     

Chaetognatha in the Bahía Magdalena lagoon complex, Baja California Sur, México: species composition and assemblages

The chaetognaths from 187 zooplankton samples collected from the Bahia Magdalena lagoon complex, Baja California Sur, Mexico during March, June, July, August, September, November, and December 1982 were studied. Twelve species belonging to two genera were identified. Sagitta euneritica and S. enflata were the most abundant and most frequent species with maximum abundance in July (40,000 org/100 m(3) and 6100 org/100 m(3) respectively). Sagitta pacifica, S. regularis and S. pseudoserratodentata were stenothermic (21 to 25 degrees C), whereas the rest of the species were eurythermic (15.5 to 29.5 degrees C). Sagitta euneritica contributed considerably to the zooplanktonic biomass, increasing the density in particular in BahíaAlmejas. The analysis of the species assemblages (Morisita index) showed that S. pacifica and S. regularis interact more frequently in August when there is a change of the water masses that converge in this zone during summer, when the California Countercurrent predominates. The composition of taxa during winter is characterized by the dominance of S. euneritica. Entering the warm period, an abrupt change occurs in taxa composition of the three zones studied: channels, Bahía Magdalena, and BahíaAlmejas. The amplitude and distribution of S. peruviana was influenced possibility by the oceanographic conditions of ENSO 1982.     

Acute toxicity of mercury to the fingerlings of Indian major carps (catla, rohu and mrigal) in relation to water hardness and temperature

In the present study short-term (96 hr) toxicity of mercury in relation to water hardness (270 and 560 mg/l) and temperature (16 degrees C and 35 degrees C) to the fingerlings of Indian major carps, i.e. catla, rohu and mrigal has been evaluated using static bioassay. The LC5o indicates that both water hardness and temperature played significant role in mercury toxicity. The test fishes were found most resistant with water hardness of 560 mg/l at 16 degrees C as compared to that of water hardness of 560 mg/l at 35 degrees C and water hardness of 270 mg/l at both the temperatures, i.e. 35 and 16 degrees C. Whereas the order of relative sensitivities of these fishes for mercury ions were recorded as catla>rohu>mrigal. The safe concentrations of mercury were ranged in between 12.133 to 19.689 microg/l for catla; 64.039 to 82.555 microg/l for rohu and 73.510 to 89.585 microg/l for mrigal for both the water hardness and temperature.     

Population dynamics of the tropical cladoceran Ceriodaphnia rigaudi Richard, 1894 (Crustacea: Anomopoda). Effect of food type and temperature

The knowledge of population effects of food on tropical, filter-feeding cladocerans is scarce because a reduced number of species has been extensively studied. Ceriodaphnia rigaudi Richard 1894, a small-sized cladoceran distributed mainly in tropical and subtropical regions of the world, was studied. The aim of this study was to contribute to the knowledge of the reproductive biology of a poor-known Cladoceran; for this we assessed the effect of feeding and temperature on the reproduction and life cycle of this species. Three microalga species (Pseudokirchneriella subcapitata, Ankistrodesmus falcatus, and Chlorella vulgaris) were supplied as food each at a concentration of 12 mg l(-1) (dry weight, equivalent to 1.3 x 10(6), 0.4 x 10(6) and 1.35 x 10(6) cell m1(-1), respectively, and equivalent to 7.8 microg C ml(-1), at two temperatures (20 and 25 degrees C). We evaluated, among other responses, longevity, total progeny, survival, life expectancy at birth and fecundity. Organisms fed with the microalgae A. falcatus and P subcapitata presented both higher longevity (30.7 +/- 5.91, 26.6 +/- 3.59 days, respectively) and total progeny (45 +/- 13.80, 40.7 +/- 0.66 neonates female (-1) values than those organisms fed C. vulgaris (13.5 +/- 4.63 days and 17.6 +/- 6.19 neonates female (-1), respectively). On the other hand, temperature affected significantly the population parameters of C. rigaudi, recording maximal longevity values (56.1 +/- 9.41 days) at 20 degrees C in organisms fed A. falcatus; however, age at first reproduction and total progeny were negatively affected by this temperature: sexual maturation of the females was delayed until the age of 16 days and the number of neonates produced was smaller (9.8 +/- 3.45 with C. vulgaris; 24.7 +/- 6.01 with P subcapitata, and 35.5 +/- 8.59 neonates female(-1) with A. falcatus). The best reproductive responses for C. rigaudi in this study were obtained with A. falcatus at degrees 25 degrees C.     

Production of valued materials from squid viscera by subcritical water hydrolysis

Subcritical water hydrolysis was carried out to produce valued materials from squid viscera, the waste product of fish processing industries. The reaction temperatures for hydrolysis of rawand deoiled squid viscera were maintained from 180 to 280 degrees C for5 min. The ratio of material to water forhydrolysis was 1:50. Most of the proteins from deoiled squid viscera were recovered at high temperature. The protein yield in raw squid viscera hydrolyzate decreased with the rise of temperature. The reducing sugar yield was higher at high temperature in subcritical water hydrolysis of both raw and deoiled squid viscera. The highest yield of amino acids in raw and deoiled squid viscera hydrolyzates were 233.25 +/- 3.25 and 533.78 +/- 4.13 mg g(-1) at 180 and 280 degrees C, respectively. Most amino acids attained highest yield at the reaction temperature range of 180-220 degrees C and 260-280 degrees C for raw and deoiled samples, respectively. The recovery of amino acids from deoiled squid viscera was about 1.5 times higher than that of raw squid viscera.     

Counterintuitive density-dependent growth in a long-lived vertebrate after removal of nest predators

Examining the phenotypic and genetic underpinnings of life-history variation in long-lived organisms is central to the study of life-history evolution. Juvenile growth and survival are often density dependent in reptiles, and theory predicts the evolution of slow growth in response to low resources (resource-limiting hypothesis), such as under densely populated conditions. However, rapid growth is predicted when exceeding some critical body size reduces the risk of mortality (mortality hypothesis). Here we present results of paired, large-scale, five-year field experiments to identify causes of variation in individual growth and survival rates of an Australian turtle (Emydura macquarii) prior to maturity. To distinguish between these competing hypotheses, we reduced nest predators in two populations and retained a control population to create variation in juvenile density by altering recruitment levels. We also conducted a complementary split-clutch field-transplant experiment to explore the impact of incubation temperature (25 degrees or 30 degrees C), nest predator level (low or high), and clutch size on juvenile growth and survival. Juveniles in high-recruitment (predator removal) populations were not resource limited, growing more rapidly than young turtles in the control populations. Our experiments also revealed a remarkably long-term impact of the thermal conditions experienced during embryonic development on growth of turtles prior to maturity. Moreover, this thermal effect was manifested in turtles approaching maturity, rather than in turtles closer to hatching, and was dependent on population density in the post-hatching rearing environment. This apparent phenotypic plasticity in growth complements our observation of a strong, positive genetic correlation between individual body size in the experimental and control populations over the first five years of life (rG - +0.77). Thus, these Australian pleurodiran turtles have the impressive capacity to acclimate plastically to major demographic perturbations and enjoy the longer-term potential to evolve adaptively to maintain viability.     

Effect of temperature on the microdistribution of the isopod Sphaeroma rugicauda from a saltmarsh habitat

The saltmarsh isopod Sphaeroma rugicauda (Leach) is subjected to widespread diurnal and seasonal temperature fluctuations under natural conditions. Laboratory studies on its activity show that there is a relationship between behaviour activity and exposure temperature between 2.5° and 25°C. Although S. rugicauda has no complex metabolic adaptations, this isopod is able to maintain a rate of aerial oxygen consumption which is similar to that in water within the temperature range 5° to 25°C. The responses of S. rugicauda to changes in environmental temperature are discussed in relation to the seasonal microdistribution of the isopod in the salt-marsh habitat.     

Riparian shading and groundwater enhance growth potential for smallmouth bass in Ozark streams.

Moderation of stream temperatures by riparian shading and groundwater are known to promote growth and survival of salmonid fishes, but effects of riparian shade and groundwater on to be growth of warmwater stream fishes are poorly understood or assumed to be negligible. We used stream temperature models to relate shading from riparian vegetation and groundwater inflow to summer water temperatures in Missouri Ozark streams and evaluated effects of summer water temperatures on smallmouth bass, Micropterus dolomieu, growth using a bioenergetics model. Bioenergetics model simulations revealed that adult smallmouth bass in non-spring-fed streams have lower growth potential during summer than fish in spring-fed streams, are subject to mass loss when stream temperatures exceed 27 degrees C, and will likely exhibit greater interannual variation in growth during summer if all growth-influencing factors, other than temperature, are identical between the two stream types. Temperature models indicated that increased riparian shading will expand the longitudinal extent of thermal habitat capable of supporting adult smallmouth bass growth in spring-fed stream reaches when mean daily air temperatures exceed 27 degrees C. Optimum growth temperature (22 degrees C) will be present only in spring-fed streams under these conditions. Potential for increasing shade through riparian restoration is greatest for streams <5 m wide and along north-south reaches of larger streams. However, temperature models also indicated that restoring riparian shading to maximum levels throughout a watershed would increase the total stream mileage capable of supporting positive growth of adult smallmouth bass by only 1-6% when air temperatures are at or near average summer maxima; increases in suitable thermal habitat would be greatest in watersheds with higher spring densities. Riparian management for maintenance or restoration of the thermal habitat of adult smallmouth bass during summer should be focused in areas strongly influenced by groundwater. Restoring riparian shading along spring-fed warmwater streams will likely benefit adult smallmouth bass growth and may ultimately influence population sizes.     

Life-history trade-offs influence disease in changing climates: strategies of an amphibian pathogen

Life-history trade-offs allow many animals to maintain reproductive fitness across a range of climatic conditions. When used by parasites and pathogens, these strategies may influence patterns of disease in changing climates. The chytrid fungus, Batrachochytrium dendrobatidis, is linked to global declines of amphibian populations. Short-term growth in culture is maximal at 17 degrees-25 degrees C. This has been used in an argument that global warming, which increases the time that amphibians spend at these temperatures in cloud-covered montane environments, has led to extinctions. Here we show that the amphibian chytrid responds to decreasing temperatures with trade-offs that increase fecundity as maturation rate slows and increase infectivity as growth decreases. At 17 degrees-25 degrees C, infectious zoospores encyst (settle and develop a cell wall) and develop into the zoospore-producing stage (zoosporangium) faster, while at 7 degrees-10 degrees C, greater numbers of zoospores are produced per zoosporangium; these remain infectious for a longer period of time. We modeled the population growth of B. dendrobatidis through time at various temperatures using delayed differential equations and observational data for four parameters: developmental rate of thalli, fecundity, rate of zoospore encystment, and rate of zoospore survival. From the models, it is clear that life-history trade-offs allow B. dendrobatidis to maintain a relatively high long-term growth rate at low temperatures, so that it maintains high fitness across a range of temperatures. When a seven-day cold shock is simulated, the outcome is intermediate between the two constant temperature regimes, and in culture, a sudden drop in temperature induces zoospore release. These trade-offs can be ecologically important for a variety of organisms with complex life histories, including pathogenic microorganisms. The effect of temperature on amphibian mortality will depend on the interaction between fungal growth and host immune function and will be modified by host ecology, behavior, and life history. These results demonstrate that B. dendrobatidis populations can grow at high rates across a broad range of environmental temperatures and help to explain why it is so successful in cold montane environments.     

Forest to reclaimed mine land use change leads to altered ecosystem structure and function.

The United States' use of coal results in many environmental alterations. In the Appalachian coal belt region, one widespread alteration is conversion of forest to reclaimed mineland. The goal of this study was to quantify the changes to ecosystem structure and function associated with a conversion from forest to reclaimed mine grassland by comparing a small watershed containing a 15-year-old reclaimed mine with a forested, reference watershed in western Maryland. Major differences were apparent between the two watersheds in terms of biogeochemistry. Total C, N, and P pools were all substantially lower at the mined site, mainly due to the removal of woody biomass but also, in the case of P, to reductions in soil pools. Mineral soil C, N, and P pools were 96%, 79%, and 69% of native soils, respectively. Although annual runoff from the watersheds was similar, the mined watershed exhibited taller, narrower storm peaks as a result of a higher soil bulk density and decreased infiltration rates. Stream export of N was much lower in the mined watershed due to lower net nitrification rates and nitrate concentrations in soil. However, stream export of sediment and P and summer stream temperature were much higher. Stream leaf decomposition was reduced and macroinvertebrate community structure was altered as a result of these changes to the stream environment. This land use change leads to substantial, long-term changes in ecosystem capital and function.     

Water quality and phytoplankton characteristics in the Palk Bay, southeast coast of India

The present study was carried out to determine the water quality in terms of physicochemical characteristics and plankton distribution in the coastal waters of Kattumavadi, Palk Bay for a period of one year from April 2002 to March 2003. Air and surface water temperatures varied from 28 degrees C to 32.50 degrees C and from 27.5 to 32.0 degrees C while light extinction coefficient (LEC) varied between 0.95 and 1.85. Salinity ranged from 26.0 to 34.5 per thousand and the pH ranged between 7.95 and 8.35. Variation in dissolved oxygen content was from 4.15 to 7.18 ml(-1), and the particulate organic carbon (POC) content varied between 0.49 and 2.28 mgCl(-1). Concentrations of nutrients viz. nitrate (2.15 to 8.28 microM), nitrite (0.12 to 0.62 microM), inorganic phosphate (1.28 to 2.15 microM) and reactive silicate (5.15 to 12.52 microM) also varied independently. Chlorophyll a content ranged from 0.28 to 1.48 mg m(-3) and the primary productivity, from 4.19 to 16.08 mgCm(-3) hr(-1). The present study recorded a total of 43 species of planktonic diatoms and two species of blue-green algae. Population density of phytoplankton varied from 18,000 to 34,000 cells l(-1). Percentage composition, of the diatoms showed minimum values during the monsoon season and the maximum values during the premonsoon season.