Increase In Zooplankton Biomass Research Articles

Natural food base of fish culture ponds and its use in growing fellow of carp

A study of the natural food supply of the nursery ponds of Ecopark LLC’s fish farm in the Moshkovsky district of the Novosibirsk region was carried out in July–August 2022. Carp fingerlings were raised in the ponds with a stocking density of 34.77 and 57.73 thousand/ha. During the growing period, carp fingerlings were fed 5000 kg of feed mixture in equal parts of crushed barley and wheat grains. The species composition of zooplankton in the studied reservoirs is monotonous and is represented by nine species. Variable species diversity was observed in all reservoirs. The number of zooplankton in July in ponds No. 5 and No. 2 was 76344.45 and 48311.11 ind./m3, in August – 56800 and 48616.67 ind./m3; biomass – in the range of 2724.88-5777.86 and 1618.65-2258.73 mg/m3, respectively. Analysis of variance showed a relationship between the mass of under-yearlings and zooplankton biomass. It is 0.70, which indicates that the mass of carp under-yearlings increases with an increase in zooplankton biomass. The identified differences in the rates of linear growth and weight depending on the stocking density make it possible to establish fish productivity - in pond No. 2. It was 806.4. In pond No. 5 - it was 878.4 kg/ha. Planting 37.33 ind./ha is more productive and gives better growth indicators (average length and weight of carp fingerlings at the end of the study are 10.91 cm and 26.96 g, respectively) than planting 57.77 ind./ha (average length and weight at the back of the study 9.70 cm and 18.67 g, respectively). The planting density of 37 thousand specimens/ha makes it possible to grow fingerlings with a standard weight of 25-26 g. The influence of the stocking density factor on the weight of fingerlings is 0.92 (at a level of P > 0.001). Fish productivity in Pond No. 2 was 806.4 kg/ha, and in Pond No. 5, it was 878.4 kg/ha.

Особливості росту дволіток веслоноса (Polyodon spathula Walbaum, 1792) в умовах ставового господарства Лісостепу України

Purpose. To investigate the peculiarities of growth of age-1+ paddlefish depending on water temperature and quantitative parameters of zooplankton development in ponds of the forest-steppe zone of Ukraine. Methodology. Age-1+ paddlefish, a North American zooplanktophagus were reared in polyculture with cyprinids in a 72-hectare pond using semi-intensive technology. The stocking density of age-1 paddlefish with an average weight of 86.5 g was 59 fish/ha, with a total stocking density of 2,402 fish/ha for all objects of polyculture. The intensification measures included fertilization of ponds with traditional organic fertilizers and feeding of carp with feed mixtures based on waste from the processing of agricultural raw materials of plant origin. The study of the intensity of development of the natural food supply and physicochemical parameters of water was carried out according to the methods generally accepted in hydrobiology and hydrochemistry. Determination of piscicultural parameters and growth characteristics of age-1+ paddlefish was carried out using methods common in ichthyology based on the dynamics of body weight gains in absolute and relative values. Findings. The conditions of the pond environment during most of the period of rearing of age-1+ paddlefish met the biological requirements of this species. A periodic decrease in the content of oxygen dissolved in water to 3.3-3.5 mgO2/dm3 was noted, which could negatively affect the growth of fish. Water temperature during the fish breeding period varied between 9.8-26.5oC. The average seasonal biomass of phytoplankton and zooplankton of the pond was 16.49 mg/dm3 and 3.92 g/m3, respectively, with a predominance of Cladocera and Copepoda (respectively, 61.0 and 34.5% in the average seasonal biomass) in the quantitative composition of zooplankton. As a result, age-1+ paddlefish reached an average weight of 1318.3 g with a fish productivity of 45.6 kg/ha and a total pond fish productivity of 1162.6 kg/ha. Maximum relative weight gains of paddlefish of 4.25–4.37% per day were observed during the first half of the growing season (mainly in June) at a water temperature of 22–25oC during the period of increase in zooplankton biomass from 3.79 to 10.11 g/m3. Originality. New data were obtained on the growth characteristics of paddlefish depending on environmental conditions of the ponds of the Forest-Steppe zone of Ukraine. Practical value. The study results can be used in the process of improving pond aquaculture technologies in Ukraine. Key words: pond aquaculture, paddlefish, growth, zooplankton, water temperature.

Factors regulating phytoplankton biomass along the Indian coast: elucidation with long-term data.

Long-term variations in phytoplankton biomass from nine coastal states along the Indian coast were studied and co-related with biotic and abiotic factors. Surface water temperature, dissolved inorganic nutrients (nitrogen and phosphorous), and plankton (phytoplankton and zooplankton) biomass data were collected between 1992 and 2015. Linear regression analysis showed a considerable increase in dissolved inorganic nutrients. A substantial increase in the frequency and intensity of phytoplankton blooms (> 3mg/m3) was observed along the Indian coast. The considerable increase in dissolved inorganic nutrient concentrations could be the major reason for an increase in phytoplankton bloom occurrences. Availability of light and periodicity in zooplankton population were also regulating phytoplankton biomass. Our results revealed that multiple factors are influencing phytoplankton biomass along the Indian coast; particularly, the increase in nutrient concentrations is promoting plankton biomass. Moreover, significant increase in zooplankton biomass can have substantial impact on the biogeochemical cycling and energy transfer to higher trophic levels.

Seasonal and plurennial changes of POPs repository in freshwater zooplankton: A 10-year study in the large deep subalpine Lake Maggiore (Italy)

Determining the concentration of POPs (Persistent Organic Pollutants) such as total dichlorodiphenyltrichloroethane (DDTtot) and polychlorinated biphenyls (PCBs) in the zooplankton is essential for evaluating the level of toxicity in the environment and the risk to ecosystem health. The extent to which POPs persist in the environment and affect human health depends on accumulation in the different components of the zooplankton community such as particle feeders and/or predators and their subsequent consumption by fish, which varies seasonally.We analyzed ten-years (2011–2020) of seasonal data on POPs in the crustacean zooplankton community of Lake Maggiore (Italy). The concentration of total DDTs, as sum of all congeners ranged between 23.5 and 156.9 ng/g dry weight, while sumPCB14 ranged from 24.4 and 133.6 ng/g dry weight. We traced particle feeders' vs predatory taxa within the zooplankton community using carbon and nitrogen stable isotopic values. POPs concentration was significantly related to the nitrogen isotopic values. The zooplankton biomass increase in Spring was important, both through this being a period of increased metabolism and activity of planktivorous fish and also as it was the period when the zooplankton repository of POPs was at a maximum. DDTtot stocked in zooplankton ≥450 μm was up to 275 ng/m2, while sumPCB14 was 285 ng/m2 in 2013. A decrease of DDTtot stocked in the zooplankton repository characterized the last five years examined, when mean annual values (14.8–56.9 ng/m2) were less than half those of the previous period (50.7–128.6 ng/m2).

Terrigenous subsidies in lakes support zooplankton production mainly via a green food chain and not the brown food chain

Terrestrial organic matter (t-OM) has been recognized as an important cross-boundary subsidy to aquatic ecosystems. However, recent evidence has shown that t-OM contributes little to promote secondary production in lakes because it is a low-quality food for aquatic consumers. To resolve this conflict, we performed a field experiment using leaf litter as t-OM. In the experiment, we monitored zooplankton biomass in enclosures with and without addition of leaf litter under shaded and unshaded conditions and assessed food web changes with stable isotope analyses. We then examined whether or not leaf litter indeed stimulates lake secondary production and, if it does, which food chain, the detritus-originated food chain (“brown” food chain) or the algae-originated food chain (“green” food chain), contributes more to this increase. Analyses with stable isotopes showed the importance of t-OM in supporting secondary production under ambient lake conditions. However, the addition of the leaf litter increased the zooplankton biomass under unshaded conditions but not under shaded conditions. We found that phosphorus was leached from leaf litter at much faster rate than organic carbon and nitrogen despite its low content in the leaf litter. These results showed that leaf litter stimulated the increase in zooplankton biomass mainly through the green food chain rather than the brown food chain because the leaf litter supplied limiting nutrients (i.e., phosphorus) for primary producers.Our results indicate that the functional stoichiometry of the subsidized organic matter plays a crucial role in determining the relative importance of brown and green food chains in promoting production at higher trophic levels in recipient ecosystems.

Global Distribution of Zooplankton Biomass Estimated by In Situ Imaging and Machine Learning

Zooplankton plays a major role in ocean food webs and biogeochemical cycles, and provides major ecosystem services as a main driver of the biological carbon pump and in sustaining fish communities. Zooplankton is also sensitive to its environment and reacts to its changes. To better understand the importance of zooplankton, and to inform prognostic models that try to represent them, spatially-resolved biomass estimates of key plankton taxa are desirable. In this study we predict, for the first time, the global biomass distribution of 19 zooplankton taxa (1-50 mm Equivalent Spherical Diameter) using observations with the Underwater Vision Profiler 5, a quantitative in situ imaging instrument. After classification of 466,872 organisms from more than 3,549 profiles (0-500 m) obtained between 2008 and 2019 throughout the globe, we estimated their individual biovolumes and converted them to biomass using taxa-specific conversion factors. We then associated these biomass estimates with climatologies of environmental variables (temperature, salinity, oxygen, etc.), to build habitat models using boosted regression trees. The results reveal maximal zooplankton biomass values around 60°N and 55°S as well as minimal values around the oceanic gyres. An increased zooplankton biomass is also predicted for the equator. Global integrated biomass (0-500 m) was estimated at 0.403 PgC. It was largely dominated by Copepoda (35.7%, mostly in polar regions), followed by Eumalacostraca (26.6%) Rhizaria (16.4%, mostly in the intertropical convergence zone). The machine learning approach used here is sensitive to the size of the training set and generates reliable predictions for abundant groups such as Copepoda (R2 ≈ 20-66%) but not for rare ones (Ctenophora, Cnidaria, R2 < 5%). Still, this study offers a first protocol to estimate global, spatially resolved zooplankton biomass and community composition from in situ imaging observations of individual organisms. The underlying dataset covers a period of 10 years while approaches that rely on net samples utilized datasets gathered since the 1960s. Increased use of digital imaging approaches should enable us to obtain zooplankton biomass distribution estimates at basin to global scales in shorter time frames in the future.

Impacts of sediment resuspension on phytoplankton biomass production and trophic transfer: Implications for shallow lake restoration

Wind-induced sediment resuspension in shallow lakes may enhance nutrient availability while reducing light availability for phytoplankton growth, thereby affecting the entire food-web. Lake restoration projects that reduce wind-induced resuspension are expected to enhance trophic transfer efficiencies, thereby improving food-web structure and functioning. Yet, reduced resuspension may also lead to lower nutrient concentrations in the water column, promote benthic algae development, reduce phytoplankton biomass production and thereby reduce secondary production by zooplankton. Lake Markermeer is a shallow delta lake in The Netherlands subject to wind-induced sediment resuspension. Restoration project Marker Wadden consists of newly built islands aiming to reduce sediment resuspension and promote higher trophic levels. Here, we tested the effects of reduced sediment resuspension on phytoplankton biomass build-up, benthic algae development, and zooplankton abundances at different temperatures in a 14-day indoor microcosm experiment. We used Marker Wadden sediment with three resuspension intensities combined with three temperatures, to also test effects of higher temperatures in shallow sheltered waters. Reduced sediment resuspension decreased nutrient concentrations and phytoplankton biomass build-up, while increasing light availability and enhancing benthic algae biomass development. Reduced sediment resuspension furthermore increased zooplankton biomass. Enhanced sediment resuspension and higher temperatures synergistically interacted, maintaining a high level of inorganic suspended solids. Our experimental results are in line with long-term seasonal observations from Lake Markermeer. Our findings demonstrate that for shallow lakes suffering from wind effects, measures such as Marker Wadden aimed at reducing sediment resuspension can be effective in restoring secondary production and supporting higher trophic levels.

Effects of nitrogen enrichment on zooplankton biomass and N:P recycling ratios across a DOC gradient in northern-latitude lakes

We used data from whole-lake studies to assess how changes in food quantity (phytoplankton biomass) and quality (phytoplankton community composition, seston C:P and N:P) with N fertilization affect zooplankton biomass, community composition and C:N:P stoichiometry, and their N:P recycling ratio along a gradient in lake DOC concentrations. We found that despite major differences in phytoplankton biomass with DOC (unimodal distributions, especially with N fertilization), no major differences in zooplankton biomass were detectable. Instead, phytoplankton to zooplankton biomass ratios were high, especially at intermediate DOC and after N fertilization, implying low trophic transfer efficiencies. An explanation for the observed low phytoplankton resource use, and biomass responses in zooplankton, was dominance of colony forming chlorophytes of reduced edibility at intermediate lake DOC, combined with reduced phytoplankton mineral quality (enhanced seston N:P) with N fertilization. N fertilization, however, increased zooplankton N:P recycling ratios, with largest impact at low DOC where phytoplankton benefitted from light sufficiently to cause enhanced seston N:P. Our results suggest that although N enrichment and increased phytoplankton biomass do not necessarily increase zooplankton biomass, bottom-up effects may still impact zooplankton and their N:P recycling ratio through promotion of phytoplankton species of low edibility and altered mineral quality.

Associations between timing and magnitude of spring blooms and zooplankton dynamics in the southwestern Barents Sea

During the past decades, many high-latitude marine systems have experienced a strong warming trend with poorly understood consequences for trophic coupling and ecosystem functioning. A key knowledge gap is how timing and magnitude of phytoplankton blooms influence higher trophic levels. We investigated associations between timing and magnitude of phytoplankton blooms and dynamics of 3 size fractions of mesozooplankton from 1998 to 2019. The study focused on the southwestern Barents Sea, an Arctic shelf sea area that is dominated by relatively warm Atlantic waters and which remains ice-free year-round. Results showed that an early spring bloom (late April to early May) was associated with high biomass of medium-sized (1-2 mm) zooplankton in areas ‘downstream’ of the phytoplankton bloom, along the prevailing currents. Conversely, a late spring bloom was associated with high biomass of small-sized (0.180-1 mm) zooplankton, with no spatial shift. High peak magnitude of the bloom (>5 mg chl a m-3) was associated with low zooplankton biomass, suggesting either top-down control or that the zooplankton utilized intense and presumably short blooms inefficiently. For small- and large-sized (>2 mm) zooplankton, the relationship was nonlinear, as zooplankton biomass was also low when bloom peak magnitude was very low (<4 mg chl a m-3). Our findings imply that if phytoplankton blooms in the region occur earlier, this will increase the biomass of medium-sized zooplankton that are important prey for planktivorous fishes. Moreover, our study highlights that increased biomass of phytoplankton does not necessarily translate into increased zooplankton biomass.

Zooplankton variability in the Strait of Georgia, Canada, and relationships with the marine survivals of Chinook and Coho salmon.

The Strait of Georgia, Canada, has complex interactions among natural and human pressures that confound understanding of changes in this system. We report on the interannual variability in biomass of 12 zooplankton taxonomic groups in the deep (bottom depths greater than 50 m) central and northern Strait of Georgia from 1996 to 2018, and their relationships with 10 physical variables. Total zooplankton biomass was dominated (76%) by large-sized crustaceans (euphausiids, large and medium size calanoid copepods, amphipods). The annual anomaly of total zooplankton biomass was highest in the late 1990s, lowest in the mid-2000s, and generally above its climatological (1996-2010) average after 2011, although many individual groups had different patterns. Two latent trends (derived from dynamic factor analyses) described the variability of annual biomass anomalies underlying all zooplankton groups: a U-shaped trend with its minimum in the mid-2000s, and a declining trend from 2001 to 2011. Two latent trends also described the physical variables. The variability represented by these four latent trends clustered into two periods: 1996-2006, with generally declining zooplankton biomass and increasing salinities, and 2007-2018, with increasing zooplankton biomass and decreasing salinities. ARIMA modelling showed sea surface salinity at Entrance Island in the middle Strait of Georgia, the Pacific Decadal Oscillation, and the peak date of the spring phytoplankton bloom were significantly related to the two latent zooplankton trends. ARIMA models comparing zooplankton and physical variables with the marine survivals of four salmon populations which enter the Strait as juveniles (Chinook: Cowichan River, Puntledge River, Harrison River; Coho: Big Qualicum River) all included zooplankton groups consistent with known salmon prey; prominent among the physical variables were sea surface salinity and variables representing the flow from the Fraser River. These regressions explained (adjR2) 38 to 85% of the annual variability in marine survival rates of these salmon populations over the study time period. Although sea temperature was important in some relationships between zooplankton biomass and salmon marine survival, salinity was a more frequent and more important variable, consistent with its influence on the hydrodynamics of the Strait of Georgia system.

Cascading effects of freshwater salinization on plankton communities in the Sierra Nevada

AbstractRunoff containing road salt (sodium chloride, NaCl) causes the salinization of inland freshwaters, with potentially severe impacts on aquatic species. We performed a mesocosm experiment to test the effects of salinization on plankton community structure in an oligotrophic mountain lake with a limited history of elevated salt concentrations. We exposed plankton communities to a gradient of 30 salt concentrations ranging from 1 to 2900 Cl− mg L−1 for 6 weeks. Adding salt increased zooplankton biomass at concentrations < 500 mg Cl− L−1 while reducing phytoplankton biomass. Zooplankton biomass declined precipitously at higher concentrations, with phytoplankton biomass showing a mirror image increase. The initial increase in zooplankton biomass with salt addition suggests that zooplankton are salt‐limited at low ionic concentrations. Additionally, the inverse response of zooplankton and phytoplankton suggests that salinity mainly affects phytoplankton biomass via changes in top‐down regulation by grazers.

Zooplankton biomass around marine protected islands in the tropical Atlantic Ocean

Zooplankton biomass (as wet weight) was studied around marine protected islands in the tropical Atlantic Ocean. The study was based on 96 zooplankton samples collected during a 3-year period; specifically, 2010 was considered a year of thermal stress, and 2012 and 2014 were considered years without thermal stress. The analysis showed that zooplankton biomass varied significantly among protected areas, where the smallest and most isolated archipelago among the tropical islands, Saint Peter and Saint Paul Archipelago (SPSP), had approximately twice the biomass of Fernando de Noronha Archipelago (FN) and three times that of Rocas Atoll (RA). The position of SPSP near the equatorial divergence zone, the seasonal occurrences of phytoplankton blooms east of the Equator, the contribution of the productive waters that SPSP receives from the African coast under the influence of the South Equatorial Current (SEC) system and the local upwelling effect induced by the presence of the island were considered to be the factors responsible for the high pelagic productivity in this remote archipelago. Differences between day and night were also recorded. The high nocturnal biomass was considered an effect of the capture of larger-sized animals, which are considered to be strong migrators. The lowest zooplankton biomass was recorded in 2010 and was considered an apparent effect of the high sea surface temperature observed in that year. However, the interaction between spatial and interannual factors showed that, in FN and SPSP, the zooplankton biomass was lower in the year under thermal stress (2010). In contrast, RA presented a higher biomass value in this period. We suggest that this increase in zooplankton biomass is the result of the contribution of autochthonous sources (e.g., as a consequence of local physical events, such as current wakes, recorded during this period at RA and responsible for the increase in local planktonic productivity) and allochthonous sources (e.g., organisms supplied by FN via the zonal current).

Seasonal variability in plankton food web composition in Tuticorin coastal waters, south east coast of India

To understand the impact of seasonal variability on plankton food web composition in tropical coastal waters, samples were collected from three locations along Tuticorin coastal waters during postmonsoon, summer, and northeast (NE) monsoon seasons. During the NE monsoon, the total suspended matter (TSM) and nutrient concentrations were relatively higher, whereas salinity and plankton (phytoplankton and zooplankton) abundances were lower. Cluster analysis also revealed that the NE monsoon formed into a separate cluster because of the lower phytoplankton abundance caused by higher loads of TSM; this arrests light penetration, thereby resulting in a decrease in plankton abundance. The increase in zooplankton biomass coincided with the decrease in diatoms (p < 0.05), and the increase in cyanobacteria may reflect that grazers food choice has a significant impact on the base of the food web composition. The present study states that the phytoplankton biomass was greatly influenced by seasonality and associated changes rather than the huge supply of nutrient loads.

Effects of increased zooplankton biomass on phytoplankton and cyanotoxins: A tropical mesocosm study

Zooplankton are important biocontrol agents for algal blooms in temperate lakes, while their potential in tropical and subtropical environments is not well understood. The aim of the present study was to evaluate the influence of increased zooplankton biomass on phytoplankton community and cyanotoxins (microcystins and saxitoxin) content of a tropical reservoir (Ipojuca reservoir, Brazil) using in situ mesocosms. Mesocosms consisted of 50L transparent polyethylene bags suspended in the reservoir for twelve days. Phytoplankton populations were exposed to treatments having 1 (control), 2, 3 and 4 times the biomass of zooplankton found in the reservoir at the beginning of the experiment. Filamentous cyanobacteria such as Planktothrix agardhii and Cylindrospermopsis raciborskii were not negatively influenced by increasing zooplankton biomass. In contrast, the treatments with 3 and 4 times zooplankton biomass negatively affected the cyanobacteria Aphanocapsa sp., Chroococcus sp., Dolichospermum sp., Merismopedia tenuissima, Microcystis aeruginosa and Pseudanabaena sp.; the diatom Cyclotella meneghiniana; and the cryptophyte Cryptomonas sp. Total microcystin concentration both increased and decreased at different times depending on zooplankton treatment, while saxitoxin level was not significantly different between the treatments and control. The results of the present study suggest that zooplankton biomass can be manipulated to control the excessive proliferation of non-filamentous bloom forming cyanobacteria (e.g. M. aeruginosa) and their associated cyanotoxins.

Deep-sea benthic habitats modeling and mapping in a NE Atlantic seamount (Galicia Bank)

This study presents the results of seafloor habitat identification and mapping of a NE Atlantic deep seamount. An “assemble first, predict later” approach has been followed to identify and map the benthic habitats of the Galicia Bank (NW Iberian). Biotic patterns inferred from the survey data have been used to drive the definition of benthic assemblages using multivariate tools. Eight assemblages, four hard substrates and four sedimentary ones, have been described from a matrix of structural species. Distribution of these assemblages was correlated with environmental factors (multibeam and backscatter data) using binomial GAMs. Finally, the distribution model of each assemblage was applied to produce continuous maps and pooled in a final map with the distribution of the main benthic habitats. Depth and substrate type are key factors when determining soft bottom communities, whereas rocky habitat distribution is mainly explained by rock slope and orientation. Enrichment by northern water masses (LSW) arriving to GB and possible zooplankton biomass increase at vertical-steep walls by “bottom trapping” can explain the higher diversity of habitat providing filter-feeders at slope rocky breaks. These results concerning vulnerable species and habitats, such as Lophelia and Madrepora communities and black and bamboo coral aggregations were the basis of the Spanish proposal of inclusion within the Natura 2000 network. The aim of the present study was to establish the scientific criteria needed for managing and protecting those environmental values.

Composition and seasonal dynamics of the parasite communities of Scyliorhinus canicula (L., 1758) and Galeus melastomus Rafinesque, 1810 (Elasmobranchii) from the NW Mediterranean Sea in relation to host biology and ecological features

The parasite communities of Scyliorhinus canicula and Galeus melastomus are studied for the first time in the Mediterranean. Their seasonal and geographical variations, and their relationship with environmental and fish biological data were tested. The parasite communities of both sharks were characterized by low richness and diversity, and high dominance. Infracommunity structure and composition differed between both species probably due to the consumption of different prey associated with their different bathymetric distributions. For G. melastomus, parasite infracommunity structure and the abundance of some parasites differed across seasons and/or localities due to different dynamics of intermediate hosts populations, in turn linked to different environmental conditions. While Ditrachybothridium macrocephalum was more abundant in juvenile specimens of G. melastomus as a result of ontogenic diet shifts, Grillotia sp. accumulated in adult hosts. The abundance of Proleptus obtusus was significantly higher in S. canicula, likely due to its shallower distribution coupled with higher consumption of reptantian decapods with respect to G. melastomus. Monogenean parasites were associated to high turbidity and temperature levels, which are known to enhance monogenean infection and reproductive success. Cestodes of G. melastomus were linked to high turbidity and O2 levels, which increase zooplankton biomass, favouring the transmission of heteroxenous parasites.

Nutrients associated with terrestrial dissolved organic matter drive changes in zooplankton:phytoplankton biomass ratios in an alpine lake

Summary Dissolved organic matter (DOM) is increasing in many lakes due to climate change and other environmental forcing. A 21‐day microcosm experiment that manipulated terrestrial DOM was used to determine the effect of DOM on zooplankton:phytoplankton biomass ratios (z:p). We predicted that if DOM additions increase the amount of fixed carbon available for higher trophic levels through stimulation of the microbial loop and hence zooplankton, the z:p will increase. However, if DOM additions increase other nutrients besides fixed carbon, we predict stable or decreasing z:p due to nutrient stimulation of phytoplankton that subsequently enhances zooplankton. The effects of experimental additions of terrestrially derived DOM on zooplankton, phytoplankton, z:p and zooplankton net grazing were assessed in microcosms (sealed bags) incubated in the epilimnion (shallow; 1.5 m) and hypolimnion (deep; 8.0 m) strata of an alpine lake. DOM addition treatments (DOM+) had a 6.0‐ to 7.5‐fold increase in phytoplankton biomass relative to controls, but only a 1.3‐ to 1.5‐fold increase in zooplankton biomass, on day 21 of the experiment. The z:p was, thus, lower in the DOM+ treatments (ratios: 2.3 deep and 4.4 shallow) than in the control treatments (ratios: 13.4 deep and 17.5 shallow), providing evidence that DOM additions provide nutrient subsidies besides fixed carbon that stimulate phytoplankton biomass accumulation. The increase in zooplankton biomass during the experiment was similar in magnitude to the total amount of dissolved organic carbon (DOC) in the DOM added in the sealed bags at the beginning of the experiment, which suggests zooplankton biomass stimulation due to increased phytoplankton biomass, and not from DOM through the microbial loop, which would have greater trophic transfer losses. The consumer net grazing effect in the DOM+ treatments was reduced by 2.8‐fold in the shallow stratum and by 2.9‐fold in the deep stratum relative to the control treatments, indicating that zooplankton were unable to exert strong top–down control on the primary producers. The role of nutrients needs to be considered when examining the response of pelagic ecosystems to inputs of terrestrial DOM, especially in lakes with lower DOC concentrations.

Biomass changes and trophic amplification of plankton in a warmer ocean

Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3-D coupled physical-biogeochemical models to explore ecosystem responses to climate change with a focus on trophic amplification. The response of phytoplankton and zooplankton to global climate-change projections, carried out with the IPSL Earth System Model by the end of the century, is analysed at global and regional basis, including European seas (NE Atlantic, Barents Sea, Baltic Sea, Black Sea, Bay of Biscay, Adriatic Sea, Aegean Sea) and the Eastern Boundary Upwelling System (Benguela). Results indicate that globally and in Atlantic Margin and North Sea, increased ocean stratification causes primary production and zooplankton biomass to decrease in response to a warming climate, whilst in the Barents, Baltic and Black Seas, primary production and zooplankton biomass increase. Projected warming characterized by an increase in sea surface temperature of 2.29 ± 0.05 °C leads to a reduction in zooplankton and phytoplankton biomasses of 11% and 6%, respectively. This suggests negative amplification of climate driven modifications of trophic level biomass through bottom-up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. Simulations suggest negative amplification is the dominant response across 47% of the ocean surface and prevails in the tropical oceans; whilst positive trophic amplification prevails in the Arctic and Antarctic oceans. Trophic attenuation is projected in temperate seas. Uncertainties in ocean plankton projections, associated to the use of single global and regional models, imply the need for caution when extending these considerations into higher trophic levels.

The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves.

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing summer cyclone activity if the Arctic continues to warm and the ice cover continues to shrink.

Effects of a tropical cyclone on a pelagic ecosystem from the physical environment to top predators

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 484:1-16 (2013) - DOI: https://doi.org/10.3354/meps10378 FEATURE ARTICLEEffects of a tropical cyclone on a pelagic ecosystem from the physical environment to top predators Paul C. Fiedler1,*, Jessica V. Redfern1, Joel Van Noord1,2, Candice Hall1,3, Robert L. Pitman1, Lisa T. Ballance1 1Marine Mammal & Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 8901 La Jolla Shores Drive, La Jolla, California 92037, USA 2California Wetfish Producers Association, PO Box 1951, Buellton, California 93427, USA 3Ocean Associates, Inc., 4007 N. Abingdon Street, Arlington, Virginia 22207, USA *Email: Paul.Fiedler@noaa.gov ABSTRACT: Tropical cyclones are environmental disturbances that may have important effects on open-ocean ecosystem structure and function, but their overall impact has rarely been assessed. The Stenella Abundance Research Line Transect and Ecosystem (STARLITE) survey, in August-November 2007, investigated spatial and temporal ecosystem variability in the eastern tropical Pacific Ocean off southwestern Mexico. Oceanographic, plankton, flyingfish, seabird, and cetacean sampling was conducted along eight 170 km transect lines, each of which were surveyed on 2 consecutive days at ~3 wk intervals. Tropical storm Kiko passed though the study area on 15-17 October and forced changes in the physical environment and in the ecosystem, from plankton to top predators. Kiko mixed water from beneath the strong, shallow thermocline to the surface. As a result, surface temperature decreased by 0.6°C, the thermocline and chlorophyll maximum layer shoaled by 10-20 m, stratification decreased by 27%, and chlorophyll increased by 33% at the surface and 35% over the euphotic zone. These changes persisted for at least 4 wk. Zooplankton biomass increased by 59% about 3 wk after the phytoplankton increase. Changes in the stomach fullness and diet composition of planktivorous flyingfish were consistent with the increase in zooplankton biomass. Among top predators, the sighting rate of dolphins declined, while the response of seabirds varied by species and was confounded by seasonal migration patterns. Tropical cyclones are a recurrent disturbance in this region. They initiate a bottom-up forcing of the ecosystem, creating persistent patches of higher primary and secondary production, and may be regarded as a disturbance regime. KEY WORDS: Pelagic ecosystem · Eastern tropical Pacific · Top predator · Storm · Disturbance · Bottom- up forcing Full text in pdf format Information about this Feature Article NextCite this article as: Fiedler PC, Redfern JV, Van Noord J, Hall C, Pitman RL, Ballance LT (2013) Effects of a tropical cyclone on a pelagic ecosystem from the physical environment to top predators. Mar Ecol Prog Ser 484:1-16. https://doi.org/10.3354/meps10378Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 484. Online publication date: June 12, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.