Seasonal Production Cycle Research Articles

Hidden gems: Scattered knowledge hampered freshwater jellyfish research over the past one-and-a-half centuries.

Freshwater jellyfish (= limnic medusa-budding hydrozoans, FWJ) are a small group of cnidarians found on all continents except Antarctica in temperate to tropical latitudes. Members of this group belong primarily to three genera: Astrohydra, Craspedacusta, and Limnocnida. While Astrohydra and Limnocnida are typically restricted to the islands of Japan, Africa, and the Indian subcontinent, one species or potential species complex, Craspedacusta sowerbii, became globally invasive. Despite research going back about one-and-a-half centuries, little is known about their phylogeny and ecology compared to marine jellyfish. Recent species distribution modelling, however, showed that by 2050, C. sowerbii will potentially extend their distribution ranges due to global warming to high-latitude ecosystems and be present (medusa stage) for an extended time in the seasonal limnic production cycle. An increase in their relative ecological importance with temporal and spatial spreading is hypothesised. Only recently, it has been shown that the trophic roles of polyps and medusae and their prey overlap with other ecosystem members. In addition, medusa behaviour may cause trophic cascades and alter vertical nutrient distributions. However, polyps and other benthic life cycle stages are understudied. In globally, changing freshwater ecosystems that may become more accommodating for FWJ, an improved understanding of their population biology and ecosystem ecology is urgently needed. In this integrative review, we, therefore, explore reasons for the hampered historical research progress, contrast developments with those of marine cnidarians, compile and publish alongside an extensive and unprecedented literature database, and formulate avenues for future directions in FWJ research.

Regulation of a surface chlorophyll hotspot by wind-driven upwelling and eddy circulation in the Santa Barbara Channel, Southern California

While most of the U.S. Pacific coast is dominated by strong wind-driven upwelling in the spring and regular seasonal cycles of phytoplankton primary production, the Southern California Bight has weak intermittent wind-driven upwelling and low phytoplankton concentrations due to its irregular sheltered coastline. However, the Santa Barbara Channel (SBC), located in the northern Southern California Bight, contains an anomalous hotspot of phytoplankton biomass. We use 3D ocean circulation and particle tracking models, an empirical temperature-nitrate relationship, and satellite observations of surface chlorophyll from 1998 to 2007 to determine how wind-driven upwelling and cyclonic eddy circulation govern phytoplankton dynamics in the SBC. Our findings show that elevated surface chlorophyll in the spring is driven by the coupling of wind-driven upwelling and cyclonic eddy circulation and requires the presence of both high nitrate from wind-driven upwelling and prolonged residence times from eddy circulation. Long residence times, created by persistent cyclonic eddy circulation, allow nitrate transported into the surface layer by wind-driven upwelling to be retained in the SBC long enough to meet the required timescales for phytoplankton nutrient uptake and accumulation, overcoming the typically weak wind-driven upwelling of the Southern California Bight. Typical spring upwelling periods (SUPs) have high levels of surface chlorophyll, which are produced by the balanced coupling of upwelling strength and cyclonic eddy circulation. For two years of our study, 1998 and 1999, the SUP did not correlate with elevated surface chlorophyll. Corresponding to a strong El Niño event, the 1998 SUP had exceptionally weak wind-driven upwelling, which did not produce sufficient levels of nitrate to stimulate elevated surface chlorophyll. For the 1999 SUP, a strong La Niña event produced unusually strong wind-driven upwelling, which resulted in very high levels of nitrate, but suppressed eddy circulation and residence times to the point where phytoplankton biomass could not accumulate in the SBC. These anomalous SUPs illustrate that when wind-driven upwelling is too strong or too weak, the balance between wind-driven upwelling and cyclonic eddy circulation is disrupted, resulting in a dramatic reduction of surface chlorophyll, which may become more frequent with climate-driven upwelling changes in the future.

Phytoplankton Responses to Bacterially Regenerated Iron in a Southern Ocean Eddy.

In the Subantarctic sector of the Southern Ocean, vertical entrainment of iron (Fe) triggers the seasonal productivity cycle but diminishing physical supply during the spring to summer transition forces microbial assemblages to rapidly acclimate. Here, we tested how phytoplankton and bacteria within an isolated eddy respond to different dissolved Fe (DFe)/ligand inputs. We used three treatments: one that mimicked the entrainment of new DFe (Fe-NEW), another in which DFe was supplied from bacterial regeneration of particles (Fe-REG), and a control with no addition of DFe (Fe-NO). After 6 days, 3.5 (Fe-NO, Fe-NEW) to 5-fold (Fe-REG) increases in Chlorophyll a were observed. These responses of the phytoplankton community were best explained by the differences between the treatments in the amount of DFe recycled during the incubation (Fe-REG, 15% recycled c.f. 40% Fe-NEW, 60% Fe-NO). This additional recycling was more likely mediated by bacteria. By day 6, bacterial production was comparable between Fe-NO and Fe-NEW but was approximately two-fold higher in Fe-REG. A preferential response of phytoplankton (haptophyte-dominated) relative to high nucleic acid (HNA) bacteria was also found in the Fe-REG treatment while the relative proportion of diatoms increased faster in the Fe-NEW and Fe-NO treatments. Comparisons between light and dark incubations further confirmed the competition between picophytoplankton and HNA for DFe. Overall, our results demonstrate great versatility by microorganisms to use different Fe sources that results in highly efficient Fe recycling within surface waters. This study also encourages future research to further investigate the interactions between functional groups of microbes (e.g. HNA and cyanobacteria) to better constraint modeling in Fe and carbon biogeochemical cycles.

Seasonal cycles of phytoplankton and net primary production from Biogeochemical Argo float data in the south-west Pacific Ocean

We present annual cycles of chlorophyll a, phytoplankton carbon, nitrate and oxygen for Subtropical (STW), Subantarctic (SAW), and Subantarctic Mode (SAMW) waters near Aotearoa New Zealand from data collected by two Biogeochemical (BGC) Argo floats. We develop two simple models of depth-integrated net primary production (NPP), tuned against 14C-uptake measurements, to compare with Vertically-Generalised Production Model (VGPM) satellite-based estimates of NPP. One model is the simplest possible, and assumes production is proportional to light multiplied by chlorophyll a concentration. The second model modifies the light response profile to account for photoacclimation. In STW at 30–35°S, enhanced production is initiated in austral autumn when the mixed layer deepens to entrain nutrients into the photic zone. For about half the year, there is substantial production within a deep chlorophyll maximum that sits below the mixed layer. Consequently, depth-integrated NPP is only loosely related to surface biomass as imaged from satellite remote-sensing, and BGC Argo-based model estimates of depth-integrated NPP are about double VGPM estimates. In SAW at 45–55°S, production is initiated when vertical mixing decreases in austral spring. Production is largely within the mixed layer, and depth-integrated phytoplankton biomass and depth-integrated NPP follow surface phytoplankton biomass. Model estimates of depth-integrated NPP based on BGC Argo float profiles are comparable with VGPM estimates for the southern water masses.

Seasonal characteristics of new production in the coastal area of Hokkaido, the Okhotsk Sea during the ice-free period

Primary production is divided into new or regenerated production based on nitrate or ammonium. New production leads to a net increase in the phytoplankton abundance. Here, we investigated seasonal variations in phytoplankton uptake rates of NO3 and NH4 to estimate the contribution of new production (f-ratio) in the coastal region of Hokkaido, Okhotsk Sea, during ice-free period. High f-ratios (> 0.7) were observed during the spring bloom period (April and May). Relatively high contributions of over 0.4, which have not been previously reported in oligotrophic regions, were frequently observed in the summer and autumn (June to October), despite oligotrophic conditions. In winter (November and December), contributions were below 0.4, despite the relatively high nitrate concentrations. Contributions of new production to that of primary were high during the spring bloom period, summer, and autumn, while being low in the winter. Despite being a relatively eutrophic season, the low contribution in the winter is important because of a significant increase of phytoplankton in the spring bloom and its increase consumption by associated organisms. This seasonal cycle of new production likely plays an important role in the high productivity of fisheries in the study area.

Shine a light: Under-ice light and its ecological implications in a changing Arctic Ocean

The Arctic marine ecosystem is shaped by the seasonality of the solar cycle, spanning from 24-h light at the sea surface in summer to 24-h darkness in winter. The amount of light available for under-ice ecosystems is the result of different physical and biological processes that affect its path through atmosphere, snow, sea ice and water. In this article, we review the present state of knowledge of the abiotic (clouds, sea ice, snow, suspended matter) and biotic (sea ice algae and phytoplankton) controls on the underwater light field. We focus on how the available light affects the seasonal cycle of primary production (sympagic and pelagic) and discuss the sensitivity of ecosystems to changes in the light field based on model simulations. Lastly, we discuss predicted future changes in under-ice light as a consequence of climate change and their potential ecological implications, with the aim of providing a guide for future research.

Ovarian dynamics, batch fecundity and spawning phenology of the lessepsian migrant Etrumeus golanii DiBattista, Randall & Bowen, 2012 (Clupeidae: Dussumieriinae)

The Golani’s round herring Etrumeus golanii is an Erythraean small pelagic fish (lessepsian migrant) that entered into the Mediterranean Sea through the Suez Canal. It has expanded its distribution from the east to the western Mediterranean with well-established local populations. We investigated basic aspects of its reproductive biology off the island of Crete (eastern Mediterranean) using ovarian histology and analysis of oocyte size-frequency distributions. The species exhibited a protracted breeding period (winter to early summer), with all ovaries examined during the main spawning season having markers of recent (postovulatory follicles, POFs) or imminent spawning (advanced oocyte batch in germinal vesicle migration or hydration). The advanced batch (AB) increased rapidly in size and was fully separated from the remainder, less developed oocytes in 95% of females with “old” POFs (POFs with signs of degeneration) and all females in final maturation. The growth of the subsequent batch (SB) was arrested at sizes <630 µm until full maturation of the AB. Mean diameter of hydrated oocytes ranged from 1181 to 1325 µm and relative batch fecundity was low ranging from 56 to 157 eggs g-1. The simulation of a coupled hydrodynamic/biogeochemical model (POM/ERSEM) provided evidence that E. golanii takes advantage of the seasonal cycle of planktonic production to reproduce and exhibits monthly changes in batch fecundity that appear to be closely related with the seasonal cycle of mesozooplankton concentration.

The Potential of Depleted Oil Reservoirs for High-Temperature Storage Systems

HT-ATES (high-temperature aquifer thermal energy storage) systems are a future option to shift large amounts of high-temperature excess heat from summer to winter using the deep underground. Among others, water-bearing reservoirs in former hydrocarbon formations show favorable storage conditions for HT-ATES locations. This study characterizes these reservoirs in the Upper Rhine Graben (URG) and quantifies their heat storage potential numerically. Assuming a doublet system with seasonal injection and production cycles, injection at 140 °C in a typical 70 °C reservoir leads to an annual storage capacity of up to 12 GWh and significant recovery efficiencies increasing up to 82% after ten years of operation. Our numerical modeling-based sensitivity analysis of operational conditions identifies the specific underground conditions as well as drilling configuration (horizontal/vertical) as the most influencing parameters. With about 90% of the investigated reservoirs in the URG transferable into HT-ATES, our analyses reveal a large storage potential of these well-explored oil fields. In summary, it points to a total storage capacity in depleted oil reservoirs of approximately 10 TWh a−1, which is a considerable portion of the thermal energy needs in this area.

Impact of climate change on the primary production and related biogeochemical cycles in the coastal and sea ice zone of the Southern Ocean

Climate change in the Southern Hemisphere has exerted impact on the primary production in the Southern Ocean (SO). Using a recently released reanalysis dataset on global biogeochemistry, a comprehensive analysis was conducted on the complex biogeochemical seasonal cycle and the impact of climate change with a focus in areas within the meridional excursion of the sea ice boundary—coastal and continental shelf zone (CCSZ) and seasonal sea ice zone (SIZ). The seasonal cycles of primary production and related nutrients are closely linked with the seasonal changes in sea ice and sea surface temperatures. As sea ice retreats and allows energy and gas exchange across the sea surface, phytoplankton growth is initiated, consuming accumulated nutrients within the shallow depth of ~40 m. The seasonal evolutions of physical, biological and chemical variables show both spatial and temporal consistency with each other. Climate change has altered the timing and amplitude of the seasonal cycle. While primary production has generally increased along with an intensified uptake of CO2, some areas show a reduction in production (e.g., Prydz Bay, eastern Indian Ocean). In the CCSZ, increased iron utilization and light availability allowed production to be increased. However, the mechanism by which these factors are altered varies from one location to another, including changes in sea ice cover, surface stratification, and downwelling/upwelling. In the SIZ, where iron is generally a limiting factor, iron supply is a key driver of changes in primary production regardless of other nutrients. There is a clear influence of climatic change on the biogeochemical cycle although the signal is still weak.

Seasonal variations in downward particle fluxes in Norwegian fjords

Seasonal cycles of primary production and freshwater run-off contribute to elevated particulate matter fluxes of marine and terrestrial origin in fjords. In Norwegian fjords, aquaculture operations and jellyfish carcasses may further enhance these particulate matter fluxes. In this study, sediment traps were deployed in four Norwegian fjords (Lurefjorden, Masfjorden, Hardangerfjorden and Kaldfjorden) to quantify seasonal variations in downward particle fluxes and to investigate the contribution of aquaculture operations to these fluxes. Sediment traps were deployed in Lurefjorden, a fjord heavily populated by the deep-sea coronate medusae Periphylla periphylla, in Masfjorden, a nearby fjord without mass occurrence of P. periphylla, in Hardangerfjorden, a fjord with high density of salmon farms, and in Kaldfjorden, a northern fjord also hosting aquaculture activities. Measurements of total particulate matter (TPM), particulate organic carbon (POC), chlorophyll a (chl a), and diatom fluxes indicated the export of a diatom bloom starting in March or April and a large input of land-derived inorganic matter during rain and snowmelt events in all fjords sampled. The highest annual POC flux was recorded in the nearly landlocked Lurefjorden. In Hardangerfjorden, export fluxes suggested a local impact of aquaculture operations but freshwater run-off and water exchange had a larger influence on export fluxes than the release of aquaculture waste. In Kaldfjorden, nearly absent TPM, POC, chl a, and diatom fluxes in late spring-early summer suggested that strong stratification prevented the export of particulate matter to depth. Overall, sediment trap-derived fluxes reflected the spatial and temporal variations in the sources of particulate matter in Norwegian fjords.

Seasonal cycles of phytoplankton biomass and primary production in a tropical temporarily open-closed estuarine lagoon — The effect of an extreme climatic event

Temporarily open-closed estuaries and estuarine lagoons are among the most complex aquatic ecosystems, prone to undergo rapid changes in response to global change and other anthropogenic impacts. Nonetheless, studies on the factors that control annual cycles of phytoplanktonic biomass and primary production in such systems, especially tropical ones, are still scarce. Even less information exists on the effect increasingly frequent extreme climatic events (ECE) might have on their dynamics. For this purpose, we monitored the changes in ecological conditions in the Los Micos estuarine lagoon (Honduras) by sampling monthly during an annual cycle that included several changes in the lagoon's mouth phase and attempted to understand which environmental factors affect phytoplanktonic biomass and primary production. We also evaluated the impact of, and recovery from, a tropical storm ECE. Annual mean net production (Pn), integrated for the euphotic zone, (4.3 ± 2.8 gC m−2 d−1) and Chlorophyll a (27.1 ± 19.1 mg m−3) values in Los Micos place it as one of the more productive estuaries worldwide. The physico-chemical characteristics of the lagoon clearly depended on mouth phase; however, the values of Chla and Pn did not show significant differences between the open and closed phases. The application of distance-based multivariate linear models did not show any clear dominant model being able to explain the observed Chla and Pn patterns. The most parsimonious models included among others, salinity, particulate organic carbon and PO43−, which suggests that primary production is controlled by multiple factors. During the ECE, about 19% of DIN, 91% of DSi and PO43−, 60% of particulate organic carbon and nitrogen, and 86% of Chla were exported to the sea, greatly reducing Pn. However, Chla and Pn values recovered to pre-storm levels within 30 days, indicating that these biological variables are highly resilient in Los Micos Lagoon.

A coupled pelagic–benthic–sympagic biogeochemical model for the Bering Sea: documentation and validation of the BESTNPZ model (v2019.08.23) within a high-resolution regional ocean model

Abstract. The Bering Sea is a highly productive ecosystem, supporting a variety of fish, seabird, and marine mammal populations, as well as large commercial fisheries. Due to its unique shelf geometry and the presence of seasonal sea ice, the processes controlling productivity in the Bering Sea ecosystem span the pelagic water column, the benthic sea floor, and the sympagic sea ice environments. The Bering Ecosystem Study Nutrient-Phytoplankton-Zooplankton (BESTNPZ) model has been developed to simulate the lower-trophic-level processes throughout this region. Here, we present a version of this lower-trophic-level model coupled to a three-dimensional regional ocean model for the Bering Sea. We quantify the model's ability to reproduce key physical features of biological importance as well as its skill in capturing the seasonal and interannual variations in primary and secondary productivity over the past several decades. We find that the ocean model demonstrates considerable skill in replicating observed horizontal and vertical patterns of water movement, mixing, and stratification, as well as the temperature and salinity signatures of various water masses throughout the Bering Sea. Along the data-rich central portions of the southeastern Bering Sea shelf, it is also able to capture the mean seasonal cycle of primary production. However, its ability to replicate domain-wide patterns in nutrient cycling, primary production, and zooplankton community composition, particularly with respect to the interannual variations that are important when linking variation in productivity to changes in longer-lived upper-trophic-level species, remains limited. We therefore suggest that near-term application of this model should focus on the physical model outputs, while model development continues to elucidate potential mechanisms controlling nutrient cycling, bloom processes, and trophic dynamics.

تقدير الدورات الموسمية وأهم العوامل المؤثرة على الإنتاج السمکي بمصايد البحر الأحمر في مصر

تقدير الدورات الموسمية وأهم العوامل المؤثرة على الإنتاج السمکي بمصايد البحر الأحمر في مصر

Sensitivity of a 3D Shelf Sea Ecosystem Model to Parameterizations of the Underwater Light Field

The inherent optical properties of water over the North Sea vary widely in space and time. Their impact on the performance of 3D-ecosystem-model of the North Sea needs to be critically evaluated, which is the major research issue in the present paper. We have performed a sensitivity analysis to a modification of a common approach of light treatment that is both valid for the North Sea, as well as computationally efficient to implement and run within a 3D-ecosystem-model. Using a coupled hydrodynamical model (Regional Ocean Modelling System, ROMS) and biological model (Carbon Silicate and Nitrogen Ecosystem model, CoSiNE), we found that simple changes to the original parameterization can yield significant improvements. ROMS is shown to be suitable for application in the North Sea. The model accurately reproduces the seasonal cycle of primary production in terms of timing and magnitude, while still being more affordable in comparison to full hyperspectral treatment or solving the radiative transfer equation. The modification introduces vertically increasing attenuation that is stronger in shallow domains, in a way that is similar to attenuation due to sediment. The resulting reduction of light availability leads to strongly reduced phytoplankton growth in shallow areas with high turbidity. Areas of depths between $50m$ and $100m$ show greatest relative change with respect to their total ranges, while the deepest areas remain largely unchanged. We found that the consideration of spacial varibility of light attenuation is necessary when modelling a heterogeneous domain, such as the North Sea.

ВОЗМОЖНОСТИ ЛАНДШАФТНОЙ АРХЕОЛОГИИ В ИЗУЧЕНИИ ЛОКАЛЬНОЙ МОБИЛЬНОСТИ СТЕПНЫХ СКОТОВОДЧЕСКИХ КУЛЬТУР ЭПОХИ ПАЛЕОМЕТАЛЛА

The article is devoted to testing the effectiveness of methods of cultural landscape archaeology for studying the local mobility of steppe pastoral cultures of the Paleometal Epoch (Eneolithic — Bronze Age) of Central Eurasia. In the paradigm of landscape archaeology comprehensive studies of a series of reference polygons have been recently carried out in the North-Western Caspian region, the Middle Don region, the Southern Trans-Urals, the Ural-Mugodzhary region. The research protocol included the use of GIS technologies, means of shallow-depth geophysics, geoarchaeology, archaeobotany, archaeozoology, paleoanthropology, paleosurface science, paleoclimatology, the study of isotope archives, etc. As a result, it was found that the life support system in the reconstructed economic and cultural models was based on various forms of mobile cattle breeding with seasonal rotation of pastures and water sources with a subsidiary role of hunting and gathering. In areas where copper ore sources were located, they were harmoniously combined with mining and metallurgical production due to the coincidence of seasonal economic and production cycles. This economic system allowed achieving a dynamic balance between human needs and the natural resource potential of the developed steppe and mountain-steppe geosystems, relying on their ability to regenerate without losing their ecological function. The research has shown that landscape archaeology can claim to be a methodological basis for studying local mobility of steppe pastoralists of the Paleometal Epoch. At the same time, none of its the methods, including the most effective isotope studies, can claim to be universal. Only a comprehensive application of the entire arsenal of landscape archaeology methods can lead to the reconstruction of economic and cultural models based on mobile forms of cattle breeding.

Impact of aerosols on the spatiotemporal variability of photovoltaic energy production in the Euro-Mediterranean area

The increase in the photovoltaic energy installed capacity over the world leads to the need of a better understanding of solar resource and its variability. The aim of this work is to assess the influence of aerosols on photovoltaic energy production from seasonal to multi-decadal time scales. For this purpose we use various coupled aerosol-climate simulations that take into account the complex spatial and temporal patterns of natural and anthropogenic aerosols over the Euro-Mediterranean domain.The results show that aerosols strongly influence the spatial pattern, seasonal cycle and long-term trend of PV production. The most affected area is Central Europe where sensitivity of PV production to aerosols is higher. The annual production loss due to aerosols ranges from no impact to -16% in The Netherlands, with variation depending on the area and on the typology of the tracking system. The summer production loss can even reach -20% over regions of Africa and Syria-Iraq.We conclude that aerosols cannot be neglected in the assessment of PV production at large time scales over the Euro-Mediterranean area. Besides, the potential increase in energy due to reduction in the anthropogenic aerosols is shown in the simulation of the brightening period over Europe, with an increase of 2000 kWhkWp in a PV lifetime for the most affected areas. It illustrates the evolution that PV potential could follow in highly polluted areas through the effective implementation of pollution control measures.

A 55-Year Time Series Station for Primary Production in the Adriatic Sea: Data Correction, Extraction of Photosynthesis Parameters and Regime Shifts

In 1962, a series of in situ primary production measurements began in the Adriatic Sea, at a station near the island of Vis. To this day, over 55 years of monthly measurements through the photic zone have been accumulated, including close to 3000 production measurements at different depths. The measurements are conducted over a six-hour period around noon, and the average production rate extrapolated linearly over day length to calculate daily production. Here, a non-linear primary production model is used to correct these estimates for potential overestimation of daily production due to linear extrapolation. The assimilation numbers are recovered from the measured production profiles and subsequently used to model production at depth. Using the recovered parameters, the model explained 87% of variability in measured normalized production at depth. The model is then used to calculate daily production at depth, and it is observed to give on average 20% lower daily production at depth than the estimates based on linear extrapolation. Subsequently, water column production is calculated, and here, the model predicted on average 26% lower water column production. With the recovered parameters and the known magnitude of the overestimation, the time-series of water column production is then re-established with the non-linearly-corrected data. During this 55-year period, distinct regimes were observed, which were classified with a regime shift detection method. It is then demonstrated how the recovered parameters can be used in a remote sensing application. A seasonal cycle of the recovered assimilation number is constructed along with the seasonal cycle of remotely-sensed chlorophyll. The two are then used to model the seasonal cycle of water column production. An upper and a lower bound on the seasonal cycle of water column production based on remotely-sensed chlorophyll data are then presented. Measured water column production was found to be well within the range of remotely-sensed estimates. With this work, the utility of in situ measurements as a means of providing information on the assimilation number is presented and its application as a reference for remote sensing models highlighted.

Diatom blooms and primary production in a channel ecosystem of central Patagonia

0 0 1 293 1617 CIEP 13 3 1907 14.0 Normal 0 21 false false false ES-CL JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Times New Roman; mso-ansi-language:ES-TRAD;} Here we report on the seasonal productivity cycle at a fixed station in the Puyuhuapi Channel (44oS, 73oW), Chilean Patagonia. The analysis of in situ water column data and longer-term records of satellite derived surface ocean color (Chl-a) highlighted two contrasting seasons. A more productive period occurred between August and April, where depth-integrated gross primary production (GPP) estimates ranged from 0.1 to 2.9 g C m -2 d -1 , and a shorter, less-productive season lasted from May to July with GPP ranging from 0.03 to 0.3 g C m -2 d -1 . Diatoms of the genera Pseudo-nitzschia , Skeletonema and Chaetoceros dominated the phytoplankton, and showed a pronounced seasonality greatly influenced by prevailing environmental conditions. Warmer waters were associated with high concentrations of Pseudo-nitzschia spp., while high abundances of Skeletonema spp. and Chaetoceros spp. were associated with fresher silicate-rich waters. A marked Skeletonema spp. bloom characterized the onset of the productive season in August 2008, and with some exceptions, the highest levels of GPP (1.5 to 2.9 g C m -2 d -1 ) were measured when Skeletonema dominated the phytoplankton community. Reduced production (low GPP) was observed during periods of increased discharge from the Cisnes River, whereas the “spring” diatom bloom (or late winter bloom in Puyuhuapi Channel) observed during August 2008 coincided with a ~50% drop in the freshwater discharge. We therefore suggest that periods of intensive freshwater Input, that increase the silicic acid concentrations in the upper layers, provide ideal growing conditions for diatoms as the freshwater flow subsequently recedes. Principal component analysis (PCA) suggests that a decrease in salinity, increase in silicic acid concentration, and growth of Skeletonema spp. and Chaetoceros spp., are probably key factors in the annual cycle of GPP in Puyuhuapi Channel.

Avian influenza epidemiology in semi-intensive free ranging duck flocks of the Moyingyi Wetland in Bago East District, Myanmar.

Highly pathogenic avian influenza virus subtype H5N1 first entered Myanmar in 2006 in the Mandalay District. Several H5N1 outbreaks followed and the one of Bago East District (2007) required post outbreak surveillance in the at-risk domestic duck population of the Moyingyi Wetland. A field epidemiological study based on a randomised prospective stratified study with five surveys provided the serological evidence that the avian influenza H5 subtype circulates in the domestic duck population and spreads to almost all the newly housed (and negative) flocks in the time span of a seasonal production cycle. Virological investigation was negative. The survival analysis showed that the probability of seroconversion increased rapidly over the study period, without significant difference among different agro-ecosystems. The analysis suggests that viral spread in the new cycle could be limited if control measures were adopted at the time new flocks are housed. The study recommends that future surveillance schemes for ducks are designed in a way to get as much information as possible from serological results which should drive virological sampling to determined farms.

Environmental structuring of marine plankton phenology.

Seasonal cycles of primary production (phenology) critically influence biogeochemical cycles, ecosystem structure and climate. In the oceans, primary production is dominated by microbial phytoplankton that drift with currents, and show rapid turnover and chaotic dynamics, factors that have hindered understanding of their phenology. We used all available observations of upper-ocean phytoplankton concentration (1995-2015) to describe global patterns of phytoplankton phenology, the environmental factors that structure them, and their relationships to terrestrial patterns. Phytoplankton phenologies varied strongly by latitude and productivity regime: those in high-production regimes were governed by insolation, whereas those in low-production regimes were constrained by vertical mixing. In eight of ten ocean regions, our findings contradict the hypothesis that phytoplankton phenologies are coherent at basin scales. Lastly, the spatial organization of phenological patterns in the oceans was broadly similar to those on land, suggesting an overarching effect of insolation on the phenology of primary producers globally.