Diurnal variations in a shallow tropical freshwater fish pond in Shahjahanpur,U.P. (India)

Summary Diurnal variations in water chemistry and plankton in this eutrophic tropical freshwater ponds were quite apparent. Large fluctuations were noted in dissolved oxygen, pH, carbonate and bicarbonate concentrations. The pond water gets oversaturated with oxygen during day (24.2 p.p.m.) and depleted in the night (1.2 p.p.m.). Diurnal migrations of plankton were not in conformity with temperate waters.     

Climate change in tropical fresh waters (comment on the paper ‘Plankton dynamics under different climatic conditions in space and time’ by de Senerpont Domis et al., )

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Survival of tropical ballast water organisms during a cruise from the Indian Ocean to the North Sea

In an assessment of non-indigenous species transported by internationalship traffic to German waters, commissioned by the German FederalEnvironmental Agency, the survival of tropical plankton organismsin ballast water was studied by accompanying a container vesselon its 23-day voyage from Singapore to Bremerhaven in Germany.Two tanks, one filled off Singapore and the other off Colombo,Sri Lanka, were monitored for their phyto- and zooplankton contentby daily sampling. As already reported in previous studies,species abundance and diversity, especially of zooplankton,decreased sharply during the first days, and only a few specimenssurvived the whole cruise. The contents of the Colombo tank,however, changed dramatically during the last week. The harpacticoidcopepod, Tisbe graciloides, increased its abundance by a factorof 100 from 0.1 to 10ind. l^–1 within a few days. Thisis the first time that a ballast water organism has been foundto multiply at such a high rate. Opportunistic species suchas Tisbe are apparently able to thrive and propagate in ballastwater tanks under certain conditions. Ballast water tanks maythus serve as incubators for certain species depending on theircharacteristics.     

Plankton studies in a lacustrine environment

Summary Weekly zooplankton samples were taken during the period February, 1972 to January, 1973 at station III in a shallow and turbulent tropical reservoir (Broa Reservoir, São Carlos, São Paulo, State-Brazil). The samples were taken by plankton standard net with 68 mesh size, and collected through the horizontal hawls during 3 min. Rotifera was the most abundant group with 77.6%; Cladocera 13.6%, and Copepoda 8.7% (adult and naupliae stages). Other forms like Chaoborus larvae and some worms occurred sporadically. The seasonal fluctuation of the total zooplankton was very irregular in warm and rainy season and more stable in the dry and cold season. The composition of the zooplankton and its patterns of seasonal variation for eutrophic and oligotrophic aquatic ecosystems, in tropical regions, may differ significantly from temperate waters.     

Observations on the transparency of the waters of the Pulicat Lake with particular reference to plankton production

Marked sectoral and seasonal variations were observed in the transparency of the waters of the Pulicat lake.No tidal effect was noticed on the turbidity of the waters.The transparency of the waters in relation to the production of plankton has been discussed.     

Video plankton recorder reveals high abundances of colonial Radiolaria in surface waters of the central North Pacific

Colonial spumellarian Radiolaria are heterotrophic protiststhat form large (up to several meters in length), gelatinousstructures in the surface waters of all tropical and subtropicaloceanic ecosystems. These species are morphologically and trophicallycomplex and some, but not all, produce silica skeletal structuresof considerable paleontological significance. Skeletonless speciesof Radiolaria are poorly sampled by plankton nets, which canseverely damage these delicate organisms. Therefore, abundancesof colonial Radiolaria typically have been underestimated inquantitative studies of zooplankton abundance and biomass. Herewe document the abundances of colonial Radiolaria in the centralNorth Pacific based on analysis of video images from a miniaturizedvideo plankton recorder. We observed abundances of radiolariancells in colonies that exceeded previous reports of total Radiolariaby more than ten-fold, and counts of skeleton-bearing Radiolariaby more than two to three orders of magnitude. Biomass (carbon)within these colonies was similar to or greater than the totalradiolarian biomass (i.e. including all solitary species) previouslyreported for the Pacific. Symbiont productivity within colonialRadiolaria was estimated to constitute a modest but significantfraction of total primary productivity (up to     

Effect of the rate of phytoplankton growth on the spaced-time dynamics of plankton communities in an homogeneous environment

We use a conceptual mathematical reaction-diffusion model to investigate the mechanisms of spatial structure formation and complex temporal dynamics of plankton in a heterogeneous environment. We take into account basic trophic interactions, namely, "prey-predator" interactions between phytoplankton, zooplankton, and fish in upper layers of natural waters. We consider plankton as a passive contaminant in turbulent waters. We show that plankton structure formation can result from the difference in phytoplankton growth rate in neighboring habitats. Phytoplankton and zooplankton biomass is shown to undergo both regular and chaotic oscillations. The fish predation rate substantially affects the spatial and temporal dynamics of plankton in a heterogeneous environment.     

Notes on the distribution of phytoplankton in some Kenya waters

The distribution of the major plankton algae in a number of Kenya waters is described. The lakes and dams are shown to fall into ecological groups related to figures for the pH, conductivity and alkalinity of their waters and characterised by the dominance of certain types of alga. The composition of the phytoplankton collected at approximately monthly intervals from Sasumua and Ruiru reservoirs is described. Plankton periodicity is demonstrated for both waters and is shown to be related to rainfall. The periodicity of plankton in Lake Naivasha is noted.     

Diurnal variations in two shallow ponds in Delhi,India

Summary Observations on the diurnal variations in water chemistry and plankton in two shallow ponds, show large fluctuations in oxygen, pH and correlated changes in carbonate concentrations. A dissolved oxygen concentration of 28.2 p.p.m. was recorded in one pond. Plankton counts suggest that the diurnal migration pattern is not similar to that often found in temperate waters. Nocturnal depletion of oxygen killed fish in one pond.Department of Zoology, University of Delhi.     

Ocean acidification refugia of the Florida reef tract

Ocean acidification (OA) is expected to reduce the calcification rates of marine organisms, yet we have little understanding of how OA will manifest within dynamic, real-world systems. Natural CO₂, alkalinity, and salinity gradients can significantly alter local carbonate chemistry, and thereby create a range of susceptibility for different ecosystems to OA. As such, there is a need to characterize this natural variability of seawater carbonate chemistry, especially within coastal ecosystems. Since 2009, carbonate chemistry data have been collected on the Florida Reef Tract (FRT). During periods of heightened productivity, there is a net uptake of total CO₂ (TCO₂) which increases aragonite saturation state (Ω_arag) values on inshore patch reefs of the upper FRT. These waters can exhibit greater Ω_arag than what has been modeled for the tropical surface ocean during preindustrial times, with mean (± std. error) Ω_arag-values in spring = 4.69 (±0.101). Conversely, Ω_arag-values on offshore reefs generally represent oceanic carbonate chemistries consistent with present day tropical surface ocean conditions. This gradient is opposite from what has been reported for other reef environments. We hypothesize this pattern is caused by the photosynthetic uptake of TCO₂ mainly by seagrasses and, to a lesser extent, macroalgae in the inshore waters of the FRT. These inshore reef habitats are therefore potential acidification refugia that are defined not only in a spatial sense, but also in time; coinciding with seasonal productivity dynamics. Coral reefs located within or immediately downstream of seagrass beds may find refuge from OA.     

Eukaryotic plankton communities across reef environments in Bocas del Toro Archipelago,Panamá

Variation in light and temperature can influence the genetic diversity and structure of marine plankton communities. While open-ocean plankton communities receive much scientific attention, little is known about how environmental variation affects plankton communities on tropical coral reefs. Here, we characterize eukaryotic plankton communities on coral reefs across the Bocas del Toro Archipelago, Panamá. Temperature loggers were deployed, and midday light levels were measured to quantify environmental differences across reefs at four inshore and four offshore sites (Inshore = Punta Donato, Smithsonian Tropical Research Institute (STRI) Point, Cristobal, Punta Laurel and Offshore = Drago Mar, Bastimentos North, Bastimentos South, and Cayo de Agua). Triplicate vertical plankton tows were collected midday, and high-throughput 18S ribosomal DNA metabarcoding was leveraged to investigate the relationship between eukaryotic plankton community structure and inshore/offshore reef environments. Plankton communities from STRI Point were additionally characterized in the morning (~ 08:00), midday (~ 12:00), and late-day (~ 16:00) to quantify temporal variation within a single site. We found that inshore reefs experienced higher average seawater temperatures, while offshore sites offered higher light levels, presumably associated with reduced water turbidity on reefs further from shore. These significant environmental differences between inshore and offshore reefs corresponded with overall plankton community differences. We also found that temporal variation played a structuring role within these plankton communities, and conclude that time of community sampling is an important consideration for future studies. Follow-up studies focusing on more intensive sampling efforts across space and time, coupled with techniques that can detect more subtle genetic differences between and within communities will more fully capture plankton dynamics in this region and beyond.

     

Eastward and Westward Dispersal Across the Tropical Atlantic Ocean of Larvae Belonging to the Genus Bursa (Prosobranchia,Mesogastropoda, Bursidae)

Larvae of the genus Bursa are commonly found in the South Equatorial Current and the Equatorial Undercurrent of the tropical Atlantic Ocean. Identification of Bursa veliger larvae in the plankton of such tropical waters is made possible by a comparison of larval shells with protoconchs of juvenile and well-preserved adult specimens. The relationship between the average current velocity and the estimated minimum duration of larval development of Bursa thomae suggests that there is sufficient time to account for successful trans-Atlantic transport of its veligers in either direction between West Africa and South America. The dispersal of veliger larvae explains the wide geographical distribution attained by the genus Bursa.     

Local environment and connectivity are the main drivers of diatom species composition and trait variation in a set of tropical reservoirs

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Depth profiles of plankton,particulate organic matter and microbial activity in the eastern Canadian Arctic during summer

Summary Deep profiles of particulate organic matter, microplankton (phytoplankton and bacteria), zooplankton and their metabolic activities were investigated during two summer voyages to the eastern Canadian Arctic. Magnitudes and depth distributions were similar in many respects to observations from temperate and tropical waters. Strong gradients in most properties were observed in the upper 50–100 m and subsurface maxima were generally associated with the upper mixed-layer (>50 m). In addition to the general vertical decreases in plankton biomass and metabolic activity there was evidence for both rapid transport (sinking) of organic matter and for enhanced (above background) levels of microbial metabolic activity in deep waters (>500 m). Zooplankton depth distributions differed from the pattern generally observed at lower latitudes; in the Arctic, zooplankton abundance decreased to a lesser degree with depth than particulate organics and microplankton. The overwintering behavior of high-latitude zooplankton appeared to be the best explanation for their relatively high abundance at depth. Despite this, however, zooplankton apparently contributed little to the total column community metabolism.     

Potentially toxic and harmful phytoflagellates from the Mexican Pacific coasts

The phytoflagellates are a heterogeneous group of autotrophic, heterotrophic and mixothrophic flagellates of trophic importance in several ecosystems. As in the rest of Latin America, the phytoflagellates that occur in the Mexican Pacific coasts are virtually unknown except for a few records. Their study require complicated collection and analysis methods, a probable cause for the scarce knowledge of this group in tropical and subtropical areas. Material recently collected from various localities along the Mexican Pacific coasts was used to study phytoflagellates, including toxic and potentially toxic species. Plankton samples were treated by gravity and pump filtration, using different methods for fixation and analysis. The phyla Euglenophyta, Heterokontophyta and Haptophyta were found. They occur as plankton in oceanic and shallow coastal waters.     

Revision of the Genus Scopelogadus (Melamphaidae). 4. S. multilamellatus sp. n. and S. unispinis

Journal of Ichthyology - A new species Scopelogadus multilamellatus sp. n. has been described from the tropical waters of the Indian Ocean. The new species has a large number of pseudobranchial...     

The biological and physico-chemical uptake of radiocesium by particulate matter of natural origin (Baltic Sea)

The kinetics of radiocesium (¹³⁷Cs) uptake by natural suspended matter collected from coastal waters in the southern Baltic has been studied under laboratory conditions. The uptake of radiocesium from seawater by the suspended matter took place immediately after introduction of the isotope and attained equilibrium within a few hours. Summer and winter suspended matter displayed equal K_d values, indicating similar sorption characteristics of radiocesium. The amounts of radiocesium sorbed from sea water were proportional to the suspended matter concentration studied,i.e. up to 312 mg dry wt dm^–3. The relative uptake of radiocesium by live and dead plankton appeared to be the same. The desorption of radiocesium from dead plankton proceeded more rapidly and more intensively than sorption. There are no significant differences between the K_d values for plankton determined in laboratory experiments and those found for plankton populations under field conditions.     

Archaeal Communities in a Tropical Estuarine Ecosystem: Guanabara Bay,Brazil

Guanabara Bay is an eutrophic estuarine system located in a humid tropical region surrounded by the second largest metropolitan area of Brazil. This study explores the contrasting environmental chemistry and microbiological parameters that influence the archaeaplankton diversity in a pollution gradient in Guanabara Bay ecosystem. The environments sampled ranged from completely anoxic waters in a polluted inner channel to the adjacent, relatively pristine, coastal Atlantic Ocean. Partial archaeal 16S rDNA sequences in water samples were retrieved by polymerase chain reaction (PCR) and analyzed using denaturing gradient gel electrophoresis (DGGE), cloning, and sequencing. Sequences were subjected to phylogenetic and diversity analyses. Community structure of the free-living archaeal assemblages was different from that of the particle-attached archaea according to DGGE. Gene libraries revealed that phylotype identification was consistent with environmental setting. Archaeal phylotypes found in polluted anoxic waters and in more pristine waters were closely related to organisms that have previously been found in these environments. However, inner bay archaea were related to organisms found in oil, industrial wastes, and sewage, implying that water pollution controls archaea communities in this system. The detection of a substantial number of uncultured phylotypes suggests that Guanabara Bay harbors a pool of novel archaeaplankton taxa.