A review of the zooplankton in Singapore waters

24 pages, 1 figure, 2 tablesThe island of Singapore is located between 1°09'N¿1°29'N and 103°38'E¿104°06'E at the confluence of the Malacca Straits and the South China Sea. To date, both the marine and freshwater zooplanktons of this area are poorly studied, and availability of taxonomic identification is scarce. Moreover, most of the studies were published between the 1950s to the beginning of the 1970s. The available data are mainly qualitative, with only a few studies on zooplankton biology and ecology. Here, the literature on zooplankton communities in Singapore waters is reviewed in order to provide a baseline for future zooplankton surveys, and to better understand the aquatic ecosystems of this area. Also included are recent data obtained from a one-year plankton monitoring in 2012 from two marine stations in Singapore. The temporal variation of the plankton groups was observed in the study to be similar to what was described in some works from the 1970s. The species richness increased in these more recent studies, probably due to changes in the sampling and preservation methods. Because of these changes, comparing between data-sets is challenging; however, similarities in species richness and seasonality between a recent study and previous data-sets were evident. Finally, it is argued that continuous marine plankton monitoring would be an asset for Singapore and the regionThe authors would like to thanks the National Parks of Singapore, the DHI-NTU Research Centre for the financial support of project MadeInPlankton, where the present study is framed. The work was also supported by Elite Forsk grants nb 10-093759 and 10-094773 from the Danish Agency for Science Technology and Innovation to GD, and by project PROTOS (CTM2009-08783) from the Spanish Ministry of Science and Innovation to ACPeer Reviewe

Predator-prey interactions under calm and turbulent conditions : experimental studies on planktivorous fish

Les relations prédateur-proie entre larves et juvéniles de poissons d'une part et proies planctoniques d'autre part ont été étudiées expérimentalement. Dans un premier temps, nous avons réalisé des expériences de prédation à petite échelle pour étudier la flexibilité du comportement natatoire des larves de poissons ainsi que l'effet du comportement des zooplanctonctes sur l'interaction prédateur-proie. Des techniques vidéo standard en 2D et 3D ont été utilisées pour déterminer les taux d'ingestion ainsi que les taux de capture à l'échelle de l'individu. Les nages des prédateurs et des proies ont été caractérisées par des descripteurs échelle-dépendants (vitesse, accélération, distance d'attaque, NGDR) et échelle-indépendants(dimension fractale et analyse multifractale). Les résultats ont montré que les larves de mérou passaient d'une nage anisotropique multifractale en absence de proies, à une nage isotropique orientée vers de petits volumes en présence de proies. Ce comportement servirait à optimiser les taux de rencontre dans le milieu naturel où les proies sont distribuées de manière multifractale. Nos résultats ont montré que le comportement de nage des larves de Corégone affectait non seulement le taux de rencontre mais aussi le succès de capture. En effet, les trajectoires les plus complexes avec des attaques lointaines étaient les moins fructueuses. Enfin, l'étude de l'effet du comportement de nage du copépode Eurytemora affinis sur sa vulnérabilité à la prédation a confirmé les résultats théoriques selon lesquels les proies les plus rapides seraient les plus susceptibles à être détectées par les prédateurs. La deuxième partie de ce travail a été dédiée à l'étude expérimentale en grand volume de l'effet de la turbulence sur les performances de prédation des larves de poissons. L'étude des contenus stomacaux de poissons exposés à des niveaux de turbulence croissants ont révélé que la turbulence était préjudiciable aux taux d'ingestion quand les proies proposées étaient non-évasives (Artemia sp.). De plus, il a été démontré que la turbulence réduisait les maxima des taux d'ingestion par les larves de poissons. Enfin, quand les prédateurs sont présentés à des proies évasives (copépodes vivants), les niveaux intermédiaires de turbulence ont été bénéfiques. En effet, à des niveaux turbulents intermédiaires, les avantages dus à la diminution de la capacité de perception chez les proies semblent dépasser les inconvénients de la diminution du succès de poursuite.We experimentally investigated the predator-prey interactions between larval and juvenile fish and their zooplanktonic prey. At first, we conducted small-scale predation experiments to investigate the flexibility of fish larvae search behavior as well as the effect of plankters'swimming behavior on the predator-prey interaction. 2D and 3D video techniques were used to investigate the ingestion rate and the capture success at the individual level. Swimming patterns of both predators and prey were quantified using both scale-dependent (speed, acceleration, fixation distance, net to gross displacement ratio) and scale-independent (fractal dimension, multifractal analysis) metrics. Results revealed that fish larvae switched from an anistropic multifractal search pattern in absence of prey to an isotropic spatially-restricted search behavior when prey were present. We also demonstrated that swimming behavior not only governed the encounter rate but also the capture success. In fact, less complex pursuits associated to attacks triggered from short distances yielded the highest capture successes. The investigation of theeffect of Eurytemora affinis swimming behavior on the vulnerability to Dicentrarchus labrax larvae predation corroborated previous theoretical studies that faster prey are more conspicuous to predation than slower ones. In a second part of this work, we conducted larger scale experiments aiming at the elucidation of the effects of turbulence on the feeding success of fish larvae offered realistic prey densities. The results of gut contents analysis of larval sea bass feeding under increasing turbulence levels revealed that turbulence had negative effects on the feeding rates and maximum food intake of planktonic predators when preying on a non-evasive prey (Artemia sp.). Conversely, when feeding on an evasive prey (live copepod), moderate turbulence was beneficial to fish

Egg cannibalism in Acartia tonsa: effects of stocking density, algal concentration, and egg availability

Cannibalism in copepod culture may limit its production yield and therefore affect the economic interests associated with the use of copepods as live feed in aquaculture. The effects of adult density, egg density, and algal availability were tested on the calanoid copepod Acartia tonsa to understand how these parameters affect cannibalism rates on eggs. The overall cannibalism within the range of adult densities tested (120-1,000 adult L-1) was solely influenced by the egg and algal density, and not by the adult density. The increased densities of eggs lead to higher occurrences of cannibalism. Increasing the availability of alternative diets (e.g., algae) significantly diminished the adults' cannibalistic behavior. The highest cannibalistic rates per adult were observed at low densities of adults and high densities of eggs (120 ind L-1 and 20,000 eggs L-1, respectively) and resulted in consumption rates > 20 eggs ind(-1) h(-1). In this experiment, cannibalistic behavior reached 20 % of adult weight ind(-1) h(-1) under the aforementioned parameters. Additionally, the present study suggests that at high adult copepod density, the interactions between adults result in a decreased ``time to feed.'' Finally, it is argued that the separations of eggs from adult copepods, as well as the continuous access to an alternative food source, are necessary for decreasing the effects of cannibalism in copepod cultures

Non-proportional bioaccumulation of trace metals and metalloids in the planktonic food web of two Singapore coastal marine inlets with contrasting water residence times

11 pages, 5 figures, 5 tables, 1 appendix supplementary data https://dx.doi.org/10.1016/j.scitotenv.2016.03.234.-- This work is a contribution to the consolidated research group 2014 SGR 498 of the Generalitat de CatalunyaWe analyzed the concentrations of trace metals/metalloids (TMs) in the water, sediment and plankton of two semi-enclosed marine coastal inlets located north of Jurong Island and separated by a causeway (SW Singapore; May 2012-April 2013). The west side of the causeway (west station) has residence times of approximately one year, and the east side of the causeway (east station) has residence times of one month. The concentrations of most of the TMs in water and sediment were higher in the west than in the east station. In the water column, most of the TMs were homogeneously distributed or had higher concentrations at the surface. Preliminary evidence suggests that the TMs are primarily derived from aerosol depositions from oil combustion and industry. Analyses of TMs in seston (>. 0.7 μm; mostly phytoplankton) and zooplankton (>. 100 μm) revealed that the seston from the west station had higher concentrations of most TMs; however, the concentrations of TMs in zooplankton were similar at the two stations. Despite the high levels of TMs in water, sediment and seston, the bioaccumulation detected in zooplankton was moderate, suggesting either the presence of effective detoxification mechanisms or/and the inefficient transfer of TMs from primary producers to higher trophic levels as a result of the complexity of marine planktonic food webs. In summary, the TM concentrations in water and seston are not reliable indicators of the bioaccumulation at higher trophic levels of the food webThis work was funded through grant MadeInPlankton from Singapore National Parks Board - Singapore (NParks) and DHI-NTU Research Centre and Education Hub, Ung EliteForsk grants 10-093759 and 10-094773 from the Danish Ministry for Independent Research to GD, and Projects PROTOS (CTM2009-08783), TOPCOP (CTM2011-23480) and FERMI (CGL2014-59227-R) from the Spanish Ministry of Economy and Competitiveness to ACPeer Reviewe

Effects of eutrophication on the planktonic food web dynamics of marine coastal ecosystems: The case study of two tropical inlets

13 pages, 8 figures, 3 tables, 1 appendix supplementary data https://dx.doi.org/10.1016/j.marenvres.2016.06.005.-- This work is a contribution to the consolidated research group 2014 SGR 498 of the Generalitat de CatalunyaWe studied the plankton dynamics of two semi-enclosed marine coastal inlets of the north of Jurong Island separated by a causeway (SW Singapore; May 2012–April 2013). The west side of the causeway (west station) has residence times of ca. one year and is markedly eutrophic. The east side (east station) has residence times of one month and presents lower nutrient concentrations throughout the year. The higher nutrient concentrations at the west station did not translate into significantly higher concentrations of chlorophyll a, with the exception of some peaks at the end of the South West Monsoon. Microzooplankton were more abundant at the west station. The west station exhibited more variable abundances of copepods during the year than did the east station, which showed a more stable pattern and higher diversity. Despite the higher nutrient concentrations at the west station (never limiting phytoplankton growth), the instantaneous phytoplankton growth rates there were generally lower than at the east station. The phytoplankton communities at the west station were top-down controlled, largely by microzooplankton grazing, whereas those of the east station alternated between top-down and bottom-up control, with mesozooplankton being the major grazers. Overall, the trophic transfer efficiency from nutrients to mesozooplankton in the eutrophic west station was less efficient than in the east station, but this was mostly because a poor use of inorganic nutrients by phytoplankton rather than an inefficient trophic transfer of carbon. Some hypotheses explaining this result are discussedThis work was funded through grant MadeInPlankton from Singapore National Parks Board – Singapore (NParks) and from DHI-NTU Research Centre and Education Hub Ung EliteForsk Grants10-093759 and 10-094773 from the Danish Ministry for Independent Research to GD, and Projects PROTOS (CTM2009-08783), TOPCOP (CTM2011-23480) and FERMI (CGL2014-59227-R) from the Spanish Ministry of Economy and Competitiveness to AC.Peer Reviewe

Ontogenetic dietary changes of whitefish larvae: insights from field and experimental observations

Ontogenetic changes in resource use are widespread in many fish species. This study investigated the feeding habits of whitefish (C. lavaretus L.) larvae in Lake Annecy (France) coupled with experimental behavioral studies in order to identify the underlying mechanisms of the ontogenetic shifts in the diet. The predatory behavior of wild larvae, and the escape responses of their zooplankton prey were both videorecorded in experimental tanks under controlled laboratory conditions. Ontogenetic diet patterns showed that young whitefish larvae have a preference for small cyclops, while older larvae selectively predate cladocerans. Our experimental observations showed that the capture success rate also varied in relation to ontogenetic development in fish. Young larvae were more successful in capturing small copepods, whereas old larvae were more successful in capturing Daphnia. In addition, the larvae were able to adjust their predatory behavior (speed, pursuit) according to the swimming pattern of the prey. These observations suggest that the selective predation on cladocerans observed in old larvae is the outcome of both active and passive choices depending on the escape swimming behavior of the prey, and handling time of the predator

Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950–2021, and the impact of the COVID-19 pandemic: a comprehensive demographic analysis for the Global Burden of Disease Study 2021

BackgroundEstimates of demographic metrics are crucial to assess levels and trends of population health outcomes. The profound impact of the COVID-19 pandemic on populations worldwide has underscored the need for timely estimates to understand this unprecedented event within the context of long-term population health trends. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 provides new demographic estimates for 204 countries and territories and 811 additional subnational locations from 1950 to 2021, with a particular emphasis on changes in mortality and life expectancy that occurred during the 2020–21 COVID-19 pandemic period.Methods22 223 data sources from vital registration, sample registration, surveys, censuses, and other sources were used to estimate mortality, with a subset of these sources used exclusively to estimate excess mortality due to the COVID-19 pandemic. 2026 data sources were used for population estimation. Additional sources were used to estimate migration; the effects of the HIV epidemic; and demographic discontinuities due to conflicts, famines, natural disasters, and pandemics, which are used as inputs for estimating mortality and population. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate under-5 mortality rates, which synthesised 30 763 location-years of vital registration and sample registration data, 1365 surveys and censuses, and 80 other sources. ST-GPR was also used to estimate adult mortality (between ages 15 and 59 years) based on information from 31 642 location-years of vital registration and sample registration data, 355 surveys and censuses, and 24 other sources. Estimates of child and adult mortality rates were then used to generate life tables with a relational model life table system. For countries with large HIV epidemics, life tables were adjusted using independent estimates of HIV-specific mortality generated via an epidemiological analysis of HIV prevalence surveys, antenatal clinic serosurveillance, and other data sources. Excess mortality due to the COVID-19 pandemic in 2020 and 2021 was determined by subtracting observed all-cause mortality (adjusted for late registration and mortality anomalies) from the mortality expected in the absence of the pandemic. Expected mortality was calculated based on historical trends using an ensemble of models. In location-years where all-cause mortality data were unavailable, we estimated excess mortality rates using a regression model with covariates pertaining to the pandemic. Population size was computed using a Bayesian hierarchical cohort component model. Life expectancy was calculated using age-specific mortality rates and standard demographic methods. Uncertainty intervals (UIs) were calculated for every metric using the 25th and 975th ordered values from a 1000-draw posterior distribution.FindingsGlobal all-cause mortality followed two distinct patterns over the study period: age-standardised mortality rates declined between 1950 and 2019 (a 62·8% [95% UI 60·5–65·1] decline), and increased during the COVID-19 pandemic period (2020–21; 5·1% [0·9–9·6] increase). In contrast with the overall reverse in mortality trends during the pandemic period, child mortality continued to decline, with 4·66 million (3·98–5·50) global deaths in children younger than 5 years in 2021 compared with 5·21 million (4·50–6·01) in 2019. An estimated 131 million (126–137) people died globally from all causes in 2020 and 2021 combined, of which 15·9 million (14·7–17·2) were due to the COVID-19 pandemic (measured by excess mortality, which includes deaths directly due to SARS-CoV-2 infection and those indirectly due to other social, economic, or behavioural changes associated with the pandemic). Excess mortality rates exceeded 150 deaths per 100 000 population during at least one year of the pandemic in 80 countries and territories, whereas 20 nations had a negative excess mortality rate in 2020 or 2021, indicating that all-cause mortality in these countries was lower during the pandemic than expected based on historical trends. Between 1950 and 2021, global life expectancy at birth increased by 22·7 years (20·8–24·8), from 49·0 years (46·7–51·3) to 71·7 years (70·9–72·5). Global life expectancy at birth declined by 1·6 years (1·0–2·2) between 2019 and 2021, reversing historical trends. An increase in life expectancy was only observed in 32 (15·7%) of 204 countries and territories between 2019 and 2021. The global population reached 7·89 billion (7·67–8·13) people in 2021, by which time 56 of 204 countries and territories had peaked and subsequently populations have declined. The largest proportion of population growth between 2020 and 2021 was in sub-Saharan Africa (39·5% [28·4–52·7]) and south Asia (26·3% [9·0–44·7]). From 2000 to 2021, the ratio of the population aged 65 years and older to the population aged younger than 15 years increased in 188 (92·2%) of 204 nations.InterpretationGlobal adult mortality rates markedly increased during the COVID-19 pandemic in 2020 and 2021, reversing past decreasing trends, while child mortality rates continued to decline, albeit more slowly than in earlier years. Although COVID-19 had a substantial impact on many demographic indicators during the first 2 years of the pandemic, overall global health progress over the 72 years evaluated has been profound, with considerable improvements in mortality and life expectancy. Additionally, we observed a deceleration of global population growth since 2017, despite steady or increasing growth in lower-income countries, combined with a continued global shift of population age structures towards older ages. These demographic changes will likely present future challenges to health systems, economies, and societies. The comprehensive demographic estimates reported here will enable researchers, policy makers, health practitioners, and other key stakeholders to better understand and address the profound changes that have occurred in the global health landscape following the first 2 years of the COVID-19 pandemic, and longer-term trends beyond the pandemic