Migration Of Zooplankton Research Articles

Zooplankton diel vertical migration and contribution to deep active carbon flux in the NW Mediterranean

The diel vertical migration (DVM) of zooplankton contributes to the biological pump transporting material from surface to deep waters. We examined the DVM of the zooplankton community in different size fractions (53–200μm, 200–500μm, 500–1000μm, 1000–2000μm and >2000μm) during three cruises carried out in the open NW Mediterranean Sea. We assessed their metabolic rates from empirical published relationships and estimated the active fluxes of dissolved carbon to the mesopelagic zone driven by migrant zooplankton. Within the predominantly oligotrophic Mediterranean Sea, the NW region is one of the most productive ones, with a seasonal cycle characterized by a prominent spring bloom. The study area was visited at three different phases of the seasonal cycle: during the spring bloom, the post-bloom, and strongly stratified oligotrophic conditions. We found seasonal differences in DVM, less evident during the bloom. Changes in DVM intensity were related to the composition of the zooplanktonic assemblage, which also varied between cruises. Euphausiids appeared as the most active migrants in all seasons, and their life cycle conditioned the observed pattern. Immature stages, which are unable to perform large diel vertical movements, dominated during the bloom, in contrast to the higher relative importance of migrating adults in the other two sampling periods. The amount of dissolved carbon exported was determined by the migrant zooplankton biomass, being highest during the post-bloom (2.2mmol C respiredm−2d−1, and up to 3.1mmol C exportedm−2d−1 when DOC release estimations are added). The active transport by diel migrants represented a substantial contribution to total carbon export to deep waters, especially under stratified oligotrophic conditions, revealing the importance of zooplankton in the biological pump operating in the study area.

Diurnal Migration of Zooplankton in Inner Ambon Bay, Indonesia

The study aims to analyze diurnal migration of zooplankton in Ambon Bay. Data sampling method which is conducted stationary utilizes pontoon mooring as floating platform for acoustic data sampling. Based on the analysis, diurnal migration of zooplankton occurs at noon, zooplankton swims in water surface to epipelagic zone (0-20 m) with value of scattering volume value -90.13 dB to -100.30 dB; it indicates sparse and scattered aggregation (N=128). At night, scattering volume of -90.01 dB to -100.30 dB indicates dense and concentrated aggregation (N=75). Scattering volume is numerical expression of zooplankton density. Chlorophyll a concentration in depth of 0-10 meter having the highest value of 5.16 ppb highly affects the existence of zooplankton. It functions for food availability of pelagic fish as its carnivore.

Arctic complexity: a case study on diel vertical migration of zooplankton.

Diel vertical migration (DVM) of zooplankton is a global phenomenon, characteristic of both marine and limnic environments. At high latitudes, patterns of DVM have been documented, but rather little knowledge exists regarding which species perform this ecologically important behaviour. Also, in the Arctic, the vertically migrating components of the zooplankton community are usually regarded as a single sound scattering layer (SSL) performing synchronized patterns of migration directly controlled by ambient light. Here, we present evidence for hitherto unknown complexity of Arctic marine systems, where zooplankton form multiple aggregations through the water column seen via acoustics as distinct SSLs. We show that while the initiation of DVM during the autumnal equinox is light mediated, the vertical positioning of the migrants during day is linked more to the thermal characteristics of water masses than to irradiance. During night, phytoplankton biomass is shown to be the most important factor determining the vertical positioning of all migrating taxa. Further, we develop a novel way of representing acoustic data in the form of a Sound Image (SI) that enables a direct comparison of the relative importance of each potential scatterer based upon the theoretical contribution of their backscatter. Based on our comparison of locations with contrasting hydrography, we conclude that a continued warming of the Arctic is likely to result in more complex ecotones across the Arctic marine system.

Turbulence and internal waves in Patricia Bay, Saanich Inlet, British Columbia

The physical environment in Patricia Bay of Saanich Inlet, British Columbia, is characterized. Turbulence and internal waves were measured over September 2010 using a moored Acoustic Doppler velocimeter and Acoustic Doppler Current Profiler, while diel vertical migration of zooplankton was recorded with an echosounder to test for possible biological generation of turbulence. The average turbulent dissipation rate 〈ϵ〉 was O(10−8Wkg−1) with the corresponding diapycnal eddy diffusivity K of ~5×10−6m2s−1. Barotropic velocities responded to forcing outside Saanich Inlet in the Strait of Georgia and Haro Strait. Subtidal baroclinic velocities were southward at the surface and northward at mid-depth during spring tides, the reverse during neaps. Mode-2 M4 frequency in cross-inlet velocity u was more energetic than any mode-1 diurnal or semidiurnal frequencies in both u and v, which may be a signature of cross-inlet seiches. Spectral energy levels of baroclinic velocities and shear were weakly correlated with ϵ. No relation was found between turbulent events and diel vertical migration.

Daily Migration and Contribution of Calanoida Zooplankton to Scattering Volume in Banda Sea, Indonesia

The study aims to analyze daily migration of zooplankton in Banda Sea and contribution of Calanoida to scattering volume. Applied method is exploratory description through direct survey toward zooplankton by using Baruna Jaya VII vessel as floating platform. The findings show that daily migration of zooplankton in surface layer occurs in every observation period, average value of scattering volume in stratified depth of 0-25 meter is -84.19 dB. For stratified depth of 25-50 meter, scattering volume reaches -81.81 dB. At 00:00-03:00, zooplankton is concentrated densely at three water layers by SV value of 84.25, -81.88, -83.9 dB. Zooplankton aggregation is always almost at surface layer of 0-25 meter at every observation time. Allegedly, oceanographic factor with high concentration value of chlorophyll a are the reason. Concentration value of chlorophyll a in this depth may reach 2.1 mg/m 3 . Calanoid contributes to value of scattering volume by regression formulation of Y=-8.93+0.01 Calanoida -0.001 Cyclopoida .

Methane sources and sinks in the subtropical South Pacific along 17°S as traced by stable isotope ratios

We analyzed the concentration and stable carbon isotopic ratio (δ13C-CH4) of methane in the atmosphere and in dissolved methane in water column along 17°S in the subtropical South Pacific. Additionally, the hydrogen isotopic ratios (δD-CH4) of some water samples were analyzed. The sea–air CH4 flux is high in the eastern region and off the west coast of Australia, which is related to the high concentrations of dissolved CH4 and high wind speeds. Moreover, there is a positive correlation between the CH4 and chlorophyll a concentrations at the surface. This consistency suggested that active CH4 productions related to the primary production cause surface CH4 accumulation. CH4 shows a decrease in concentration and an increase in δ13C-CH4 and δD-CH4 values from the surface to the depth of about 1000m. The relationship between δ13C-CH4 values and CH4 concentration indicates that the isotopic enrichment of CH4 reflects microbial oxidation of CH4 with isotopic fractionation during vertical transport via vertical sinking and/or zooplankton migration. East of 120°W, δ13C-CH4 values at around 1000m exceed −30.0‰. The relationships among the δ13C-CH4 values, CH4 concentrations, and oxygen concentrations indicate that the 13C-enriched CH4 originates not only from in situ CH4 production and oxidation but also from CH4 transported from the eastern margin off Peru. Furthermore, at a site near the Central Lau Spreading Centers in the Lau Basin, high δ13C-CH4 values (up to −21.4‰) are observed in the benthic water, suggesting a hydrothermal field source.

Understanding diel-vertical feeding migrations in zooplankton using bulk carbon and nitrogen stable isotopes

We used bulk stable isotope analysis (SIA) to examine diel feeding activity in two vertically migrating krill species, Thysanoessa gregaria and Euphausia similis, off eastern Australia. SIA indicated feeding by both species above the thermocline at night, potentially on both particulate organic matter and microzooplankton. Our results support the use of SIA to investigate vertical migration and feeding in zooplankton.

Environmental forcing of the Campeche cold-water coral province, southern Gulf of Mexico

Abstract. With an extension of > 40 km2 the recently discovered Campeche cold-water coral province located at the northeastern rim of the Campeche Bank in the southern Gulf of Mexico belongs to the largest coherent cold-water coral areas discovered so far. The Campeche province consists of numerous 20–40 m-high elongated coral mounds that are developed in intermediate water depths of 500 to 600 m. The mounds are colonized by a vivid cold-water coral ecosystem that covers the upper flanks and summits. The rich coral community is dominated by the framework-building Scleractinia Enallopsammia profunda and Lophelia pertusa, while the associated benthic megafauna shows a rather scarce occurrence. The recent environmental setting is characterized by a high surface water production caused by a local upwelling center and a dynamic bottom-water regime comprising vigorous bottom currents, obvious temporal variability, and strong density contrasts, which all together provide optimal conditions for the growth of cold-water corals. This setting – potentially supported by the diel vertical migration of zooplankton in the Campeche area – controls the delivering of food particles to the corals. The Campeche cold-water coral province is, thus, an excellent example highlighting the importance of the oceanographic setting in securing the food supply for the development of large and vivid cold-water coral ecosystems.

Effects of the proximal factors on the diel vertical migration of zooplankton in a plateau meso-eutrophic Lake Erhai, China

To study the proximal factors inducing diel vertical migration (DVM) in large and small zooplankton species in a plateau lake in China, we investigated the DVM of crustacean zooplankton in Lake Erhai bimonthly from November 2009 to September 2010. We hypothesized that the factors affecting DVM behaviour in different-sized zooplankton were different. A linear regression was used to assess the relationships between environmental variables and the vertical distribution of zooplankton. All crustacean zooplankton exhibited normal DVM patterns (down during the day, up at night) across sampling months. The weighted mean depth (WMD) of all zooplankton did not show a significant correlation with the WMD of the dominant phytoplankton and chlorophyll-a. However, a negative relationship was observed between the distribution of zooplankton and water temperature in January, March, and July 2010, but the relationship was relatively weak (R-2 between 0.1 and 0.4). The vertical distribution of zooplankton was primarily affected by water transparency (P0.05), whereas the factors inducing DVM behaviour differed between large and small zooplankton. Predation avoidance and phototactic behaviour may be the dominant factors influencing DVM of large species, whereas only phototaxis contributed to the migratory behaviour of small species.

Twilight vertical migrations of zooplankton in a Chilean fjord

Time series of acoustic backscatter and vertical velocity profiles were obtained at three sites along a Chilean fjord with the purpose of determining dominant structures of vertical migrations of the sound scattering layer. Ancillary data obtained with stratified net samples indicated that the sound scattering layer may have been dominated by euphausiids and decapods. Therefore, distributions of acoustic backscatter anomalies and vertical velocities were attributed to vertical migrations of predominantly these organisms. Migration patterns were dominated by twilight excursions in which organisms swam toward the water surface at sunset, spent <0.5h at a depth near the pycnocline (∼10m) and then swam downward to depths between ∼20 and ∼60m. After congregating at those depths during night-time, organisms swam upward again toward the pycnocline at sunrise, spent <1h near the pycnocline and swam downward to their day-time depths (>100m). This migration strategy can also be termed ‘semidiel migration’ as two double excursions were linked to light levels. The reasons for this twilight migration remain uncertain. But it is possible that the up and down motion around sunset was related to predation avoidance, hunger–satiation state, ontogeny, seaward transport evasion, or reaction to the environmental shock from the pycnocline, or a combination of all or some of them. In contrast, the sunrise double excursion was probably linked to feeding requirements by organisms that need to spend the day at great depth with no food available. This study demonstrated the existence of semidiel patterns throughout the fjord and through prolonged periods. In addition, identification of this pattern by acoustic backscatter was complemented by direct vertical velocity measurements. It is proposed that twilight vertical migration is a common strategy in Chilean fjords.

Annual net community production and the biological carbon flux in the ocean

AbstractThe flux of biologically produced organic matter from the surface ocean (the biological pump), over an annual cycle, is equal to the annual net community production (ANCP). Experimental determinations of ANCP at ocean time series sites using a variety of different metabolite mass balances have made it possible to evaluate the accuracy of sediment trap fluxes and satellite‐determined ocean carbon export. ANCP values at the Hawaii Ocean Time‐series (HOT), the Bermuda Atlantic Time‐series Study (BATS), Ocean Station Papa (OSP) are 3 ± 1 mol C m−2 yr−1—much less variable than presently suggested by satellite remote sensing measurements and global circulation models. ANCP determined from mass balances at these locations are 3–4 times particulate organic carbon fluxes measured in sediment traps. When the roles of dissolved organic carbon (DOC) flux, zooplankton migration, and depth‐dependent respiration are considered these differences are reconciled at HOT and OSP but not at BATS, where measured particulate fluxes are about 3 times lower than expected. Even in the cases where sediment trap fluxes are accurate, it is not possible to “scale up” these measurements to determine ANCP without independent determinations of geographically variable DOC flux and zooplankton migration. Estimates of ANCP from satellite remote sensing using net primary production determined by the carbon‐based productivity model suggests less geographic variability than its predecessor (the vertically generalized productivity model) and brings predictions at HOT and OSP closer to measurements; however, satellite‐predicted ANCP at BATS is still 3 times too low.

Sediment mapping and long-term monitoring of currents and sediment fluxes in pockmarks in the Oslofjord, Norway

Abstract Pockmarks in the Oslofjord, Norway, show no evidence of recent expulsion of gas or water, but have still experienced reduced sedimentation rates through the Holocene. They are therefore suitable model systems for studying the currents and sedimentation in pockmarks. Mapping of sediment in a single pockmark using a large number of precisely positioned cores shows thickening of an unconsolidated, almost flocculent layer inside the pockmark. X-ray fluorescence logging of anthropogenic metals indicates higher sedimentation rates and mass accumulation rates inside the pockmark with respect to the surrounding seafloor. Furthermore, the cores taken near the pockmark centre contained relatively coarser material than those from outside the depression. Sediment traps collected substantially more sediments inside than outside of the pockmark when positioned close to the seafloor. This agrees with resuspension of sediments from the seafloor being enhanced inside the pockmark. Moreover, the traps deployed in the pockmark intercepted relatively coarser sediments. Acoustic backscatter near the seabed varies in a diurnal cycle, not related to the tide. This is interpreted as a probable result of vertical migration of zooplankton or fish. Inside the pockmark there is also a diurnal cycle in current velocity with high values in the daytime, possibly because of swimming fish. The data indicate that pockmarks collect particles, which may be largely due to deposition of sediments transported as bedload. This process should be dominant for pockmarks found in proximity to fluvial coarse-grained sediment input. The suspended fine material, however, is kept in suspension by turbulence and possibly biological activity, and can be transported away before settling. Whether an inactive pockmark will behave as a sediment depocentre or will be maintained by the action of currents, is likely to depend on the relative importance of bedload versus suspended load transport.

EFFECT OF KAIROMONE ON PREDATOR–PREY DYNAMICS — A DELAY MODEL

In most of the predator–prey systems, prey individuals make transitions between vulnerable and invulnerable states or locations. This transition is regulated by various inducible defense mechanisms. Diel vertical migration (DVM) in zooplankton is the most effective and instantaneous defense observed in zooplankton population. Zooplankton shows downward vertical migration in the daytime in the presence of predators (or predator kairomones) to avoid predation (i.e. refuge use), and it enters into the surface water again at night to graze phytoplankton. The dynamics of the planktonic ecosystem under DVM of zooplankton along with fish kairomone and the multiple delays due to migration for vulnerable and invulnerable prey and reproduction in the predator population is of considerable interest both in theoretical and experimental ecologists. By developing mathematical model, we analyze such a system. The conditions for which the system enters into Hopf-bifurcation are obtained. Moreover, the conditions for which the bifurcating branches are supercritical are also derived. Our results indicate that DVM along with the effect of kairomone and multiple delays with a certain range are responsible to enhance the stability of the system around the positive interior equilibrium point.

Horizontal distribution of Fukushima-derived radiocesium in zooplankton in the northwestern Pacific Ocean

Abstract. The magnitude of the 9.0 Tohoku earthquake and the ensuing tsunami on 11 March 2011, inflicted heavy damage on the Fukushima Dai-ichi nuclear power plant (FNPP1). Fission products were emitted, falling over a broad range in the Northern Hemisphere, and water contaminated with radionuclides leaked into the ocean. In this study, we described the horizontal distribution of the Fukushima-derived radiocesium in zooplankton and in seawater in the western North Pacific Ocean (500–2100 km from the FNPP1) 10 months after the accident. 134Cs and 137Cs were detected in zooplankton and seawater from all the stations. Because of its short half-life, the 134Cs detected in our samples could only be derived from the FNPP1 accident. The highest 137Cs activity in zooplankton was the same order of magnitude as it was one month after the accident, and average activity was one or two orders of magnitude higher than 137Cs activities observed before the accident around Japan. Horizontally, the radiocesium activity concentrations in zooplankton were high at around 25° N while those in surface seawater were high at around the transition area between the Kuroshio and the Oyashio currents (36–40° N). We observed subsurface radiocesium maxima in density range of the North Pacific Subtropical Mode Water and the occurrence of many diel vertical migratory zooplankton. These suggested that the high activity concentrations in the subtropical zooplankton at around 25° N were connected to the subsurface radiocesium and active vertical migration of zooplankton. However, the high activity concentrations of radiocesium in subsurface seawater did not necessarily correlate with the higher radiocesium activity in zooplankton. Activity concentrations of radiocesium in zooplankton might be influenced not only by the environmental radiocesium activity concentrations but also by other factors, which are still unknown.

Plankton research in the ROPME Sea Area, Achievements and Gaps

Plankton studies are one of the major items of the marine scientific activities in the ROPME SeaArea, whereas numerous investigations have been conducted on the plankton during the past century. Forphytoplankton, species composition, abundance and biomass, primary production, harmful algal blooms, redtide, toxic species, and eutrophication were considered. Zooplankton studies included species compositionand abundance, certain zooplankton groups and few studies on certain species. The main achievement of these studies was the identification of large number of phytoplankton and zooplankton species in different parts of the RSA and estimation of their abundance.The survey of these studies revealed the occurrence of several gaps in the plankton research in ROPME Sea Area. For example, the majority of these studies were carried out in the inner part, while some of them were done in the middle part. Several studies were based on samples collected once only during certain time of the year or on samples collected from localized areas. The role of the function groups of the both phytoplankton and zooplankton, the harmful algal blooms, toxic phytoplankton species, the role of small phytoplankton groups rather diatoms and dinoflagellates and vertical migration of zooplankton were little concerned. In addition, the continuous record of the Indo-Pacific species entering the inner RSA from the Sea of Oman appeared to be completely missed.The present study attempts to stress the achievements as well as the gaps in the earlier plankton studies in the ROPME Sea Area in order to propose a scientific plan for comprehensive study of plankton community relative to the prevailing environmental conditions in the concerned area.

The Atlantic spiny lumpsucker Eumicrotremus spinosus: life history traits and the seemingly unlikely interaction with the pelagic amphipod Themisto libellula

AbstractDuring a cruise to Svalbard in September 2012 a unique collection of the little known but widely distributed Atlantic spiny lumpsucker (Eumicrotremus spinosus) was made in the Hinlopen Strait. A total of 140 individuals (36-101mm total length) were collected using a bottom trawl. All individuals were sexed and 26 of these were also analysed for gonadosomatic index (GSI), hepatosomatic index (HSI) and stomach content. The sex ratio of the entire sample showed a strong bias towards females (75% of all examined specimens). The GSI ranged from 1.4 to 5.8% except for one female with a GSI of 20%. All females carried gonads in which eggs were clearly visible, independent of size, indicative of an early sexual maturation and an iteroparous life cycle of females. All examined specimens had almost an exclusively pelagic diet, with Themisto libellula constituting 100% of the stomach content in 80% of the examined fishes. The results are discussed in relation to diel vertical migration of Arctic zooplankton and deep migrating layers.

Diel vertical migration: Ecological controls and impacts on the biological pump in a one‐dimensional ocean model

Diel vertical migration (DVM) of zooplankton and micronekton is widespread in the ocean and forms a fundamental component of the biological pump, but is generally overlooked in global models of the Earth system. We develop a parameterization of DVM in the ocean and integrate it with a size‐structured NPZD model. We assess the model's ability to recreate ecosystem and DVM patterns at three well‐observed Pacific sites, ALOHA, K2, and EQPAC, and use it to estimate the impact of DVM on marine ecosystems and biogeochemical dynamics. Our model includes the following: (1) a representation of migration dynamics in response to food availability and light intensity; (2) a representation of the digestive and metabolic processes that decouple zooplankton feeding from excretion, egestion, and respiration; and (3) a light‐dependent parameterization of visual predation on zooplankton. The model captures the first‐order patterns in plankton biomass and productivity across the biomes, including the biomass of migrating organisms. We estimate that realistic migratory populations sustain active fluxes to the mesopelagic zone equivalent to between 15% and 40% of the particle export and contribute up to half of the total respiration within the layers affected by migration. The localized active transport has important consequences for the cycling of oxygen, nutrients, and carbon. We highlight the importance of decoupling zooplankton feeding and respiration and excretion with depth for capturing the impact of migration on the redistribution of carbon and nutrients in the upper ocean.

Mathematical modeling of cascading migration in a tri-trophic food-chain system

Diel vertical migration is a behavioral antipredator defense that is shaped by a trade-off between higher predation risk in surface waters and reduced growth in deeper waters. The strength of migration of zooplankton increases with a rise in the abundance of predators and their exudates (kairomone). Recent studies span multiple trophic levels, which lead to the concept of coupled vertical migration. The migrations that occur at one trophic level can affect the vertical migration of the next lower trophic level, and so on, throughout the food chain. This is called cascading migration. In this paper, we introduce cascading migration in a well-known model (Hastings and Powell, Ecology 73:896-903, 1991). We represent the dynamics of the system as proposed by Hastings and Powell as a phytoplankton-zooplankton-fish (prey-middle predator-top predator) model where fish affect the migrations of zooplankton, which in turn affect the migrations of motile phytoplankton. The system under cascading migration enhances system stability and population coexistence. It is also observed that for a higher rate of cascading migration, the system shows chaotic behavior. We conclude that the observations of Hastings and Powell remain true if the cascading migration rate is high enough.

Behavioral responses of zooplankton to solar radiation changes: in situ evidence

It is known that copepods can sense solar UV and avoid it vertically or horizontally, but no in situ studies have been documented to monitor their responses to diurnal solar radiation changes. Here, we provided in situ evidence that zooplankton sense changes in solar radiation during a diurnal solar cycle. By comparing the abundance of the zooplankton in a shaded water column with that in the non-shaded adjacent area, we found that, on a cloudy day with low solar radiation levels, the ratios of zooplankton biomass in the shaded areas to those in nearby non-shaded water ranged from 0.90 to 1.49. However, on sunny days with high solar radiation levels, the ratios ranged from 0.83 to 2.88, with the amount of zooplankton in the shaded water being higher than that in the non-shaded area and higher during the periods of higher irradiance levels. These results indicated that the horizontal migration of zooplankton may be a protective strategy against stressful solar radiation.

Diurnal vertical distribution of zooplankton in a newly formed reservoir (Tahtalı Reservoir, Kocaeli): the role of abiotic factors and chlorophyll a

Although water level fluctuations and related environmental variations occurring within reservoirs have a considerable effect on the zooplankton community, studies on zooplankton dynamics of reservoirs are very limited. In the present study, we aimed to elucidate the diurnal vertical migration of zooplankton in relation to the concentration of physicochemical factors and chlorophyll a content in a recently formed water reservoir (Tahtalı Reservoir, Kocaeli, northwestern Turkey). During the sampling period 20 zooplankton taxa were identified, which were mostly indicative of eutrophic waters, as confirmed by the physicochemical factors of the water in the reservoir. Rotifera was the most abundant group, followed by Copepoda and Cladocera. Statistical analyses indicated that all the zooplankton species showed a similar distribution pattern throughout the study. They declined in abundance in the water column from the surface to a depth of 6 m, and then increased relatively again towards the deepest part of the water (9 m). Abiotic factors, chlorophyll a, time of the day, and depth significantly impacted the abundance of zooplankton, whereas they jointly had no effect. The results suggested that abiotic factors and chlorophyll a were controlling factors on the vertical distribution pattern of the zooplankton in the Tahtalı Reservoir.