Modeling patterns of zooplankton diel vertical migration

Realized predation pressure, defined as the product of predationpressure and light intensity, expresses the mortality pressuredue to visual predation. The part of realized predation pressurewhich is sensed by organisms is here considered to be relatedto food level and temperature. This partly realized predationpressure is referred to as sensed predation pressure. We proposea possible control mechanism of diel vertical migration (DVM):organisms move vertically following the minimum change in sensedpredation pressure. To investigate this assumption, we presenta math ematical model of DVM. We assume that when predatorsare present, the food level is above a minimal level, and temperatureis higher than the tolerance of organisms to growth, prey organismsundertake DVM following the minimum change in sensed predationpressure. We examine how patterns of migration may be affectedby changes in water clarity, predation pressure, food leveland temperature. This work supports the assumption that minimizingchanges in sensed predation pressure can explain the wide variationin the vertical profile of zooplankton.     

Fish predators, food availability and diel vertical migration in Daphnia

Diel vertical migration of zooplankton is a highly variableand complex behaviour which apparently cannot be explained byany single factor. We determined the relative importance offish predation, food availability and water depth in shapingthe migratory behaviour of Daphnia. A modified 2x2x2 factorialexperiment provided two levels of fish density (present/absent),food availability (ambient/high) and depth (4–10 m); shallowtreatments with fish were excluded. Triplicate 1.2 m diameterenclosures for each of the six treatments were held in an 18unit array in Peter Lake, Gogebic Co., MI, USA. Repeated measuresANOVA identified significant trends in daphnid density, migrationand fitness (determined by lipid-ovary-egg index, LOE) as wellas in chlorophyll a content of the water column for part ofa 4-week experiment in July 1988. In deep enclosures with fish,Daphnia performed significantly more intense migrations thanin fishless enclosures, save those in fishless ambient-foodenclosures. Daphnia in deep fishless enclosures without abundantfood at depth performed significantly reduced migrations. DaphnidLOE index was significantly influenced only by food content.Our results were consistent with the predator-avoidance hypothesisas well as with observations of greatest migrations where largevertical differences in food abundance exist. They support ahierarchical view of vertical migration, with presence of fishthe primary factor, and food availability the secondary factor.     

Control mechanisms of diel vertical migration: theoretical assumptions

We explore control mechanisms underlying the vertical migration of zooplankton in the water column under the predator-avoidance hypothesis. Two groups of assumptions in which the organisms are assumed to migrate vertically in order to minimize realized or effective predation pressure (type-I) and to minimize changes in realized or effective predation pressure (type-II), respectively, are investigated. Realized predation pressure is defined as the product of light intensity and relative predation abundance and the part of realized predation pressure that really affects organisms is termed as effective predation pressure. Although both types of assumptions can lead to the migration of zooplankton to avoid the mortality from predators, only the mechanisms based on type-II assumptions permit zooplankton to undergo a normal diel vertical migration (morning descent and evening ascent). The assumption of minimizing changes in realized predation pressure is based on consideration of DVM induction only by light intensity and predators. The assumption of minimizing changes in effective predation pressure takes into account, apart from light and predators also the effects of food and temperature. The latter assumption results in the same expression of migration velocity as the former one when both food and temperature are constant over water depth. A significant characteristic of the two type-II assumptions is that the relative change in light intensity plays a primary role in determining the migration velocity. The photoresponse is modified by other environmental variables: predation pressure, food and temperature. Both light and predation pressure are necessary for organisms to undertake DVM. We analyse the effect of each single variable. The modification of the phototaxis of migratory organisms depends on the vertical distribution of these variables.     

Small-scale diel vertical migration of zooplankton in the High Arctic

Diel vertical migration (DVM) of zooplankton is considered less prominent at high latitudes where diel changes in irradiance are minimal during periods of midnight sun and polar night, leaving zooplankton without a temporal refuge and thus eliminating a key advantage of DVM. One of the shortcomings of previous DVM studies of zooplankton based on net sampling is that the depth resolution often has been too coarse to detect vertical migrations over short distances. We investigated DVM of zooplankton during August 2010 in drifting sea ice northeast of Svalbard (~81.5°N, ~30.5°E). Classical DVM behaviour (midnight rising, midday sinking) was observed between 20 and 80 m in young copepodite stages (CI–III) of Calanus finmarchicus and Calanus glacialis. The copepods Microcalanus spp., Pseudocalanus spp., Oithona atlantica, Oithona similis and Triconia borealis, alongside Eukrohnia hamata, Limacina helicina, and Fritillaria spp., all displayed signs of DVM. We conclude that zooplankton exhibit DVM in ice-covered waters over rather short distances to optimise food intake in the presence of predators.     

Light, temperature and nitrogen as interacting factors affecting diel vertical migrations of dinoflagellates in culture

Diel vertical migrations of the marine dinoflagellates Gonyaulaxpolyedra Stein and Ceratium furca (Ehr.) Clap, et Lachm. werefollowed in a laboratory tube (2.02 m x 0.25 m) under a 12:12hlight:dark cycle. The effects of temperature stratification,two levels of surface irradiance and nitrogen depletion on patternsof vertical migrations were examined. At temperatures between22–26°C with small temperature gradients, both speciesmigrated at a rate of 0.7 –1.0 m h^–1. Steeper thermoclines(ca. 0.8°C 0.1 m^–1) with temperatures below ca. 20°Ccaused a marked decrease in swimming speed which resulted inaccumulations of cells in these thermocline regions. Under conditionsof nutrient sufficiency both algae migrated into the surfacelayers at irradiance values of over 1000 µE m^–2s^–1. Increasing nitrogen depletion caused the downwardmigration of both algae to commence progressively earlier inthe day and before the end of the light period. The earlierdownward migrations enabled a more complete descent throughthe thermocline. Nitrogen depleted cells of Gonyaulax continuedto undertake vertical migrations but avoided high irradiancesthus forming subsurface maxima at irradiance levels close to150 µE m^–2 s^–1. Ceratium cells which exhaustedboth inorganic nitrogen and phosphorus ceased to migrate accompaniedby a large change in cellular fluorescence.     

Laboratory models of diel vertical migration in the dinoflagellate Ceratium hirundinella

SUMMARY. Diel vertical migrations of a dinoflagellate, Ceratium hirundinella , were induced in a laboratory tube (1.63 × 0.15 m) under a light-dark cycle. The timing of vertical migrations differed between cultures in the exponential and stationary phases of growth; the latter showed a greater coincidence with the light regime.
Migration of cells into the surface layers occurred at low values of surface irradiance (<550 μeinsteins m⁻² s⁻¹). At irradiances more closely approaching summer sunshine (> 1300 μE m⁻² s⁻¹) there was a marked avoidance of surface waters, and population maxima were found at depths associated with a relative irradiance level of 10% or c. 150 μE m⁻² s⁻¹). Thermal stratification restricted downward movement of cells into the cooler layers. The combination of high surface irradiance and thermal stratification resulted in large, stable, sub-surface maxima of Ceratium , similar to those observed in natural waters under comparable environmental conditions.     

Partial diel vertical migration in an omnivorous macroinvertebrate,Mysis diluviana

Hydrobiologia - Partial migration, whereby only a portion of a population migrates, has just recently received attention in aquatic systems. Partial diel vertical migration (DVM) has received even...     

Seasonal vertical distribution and diel migration of zooplankton in a temperate stratified lake

The investigation of the vertical distribution of the zooplankton community in the temperate Lake Trichonis during four seasons in 2005, showed the existence of vertical segregation among species, ontogenetic stages and sexes within and between the major groups. In each season, the two or three more abundant rotifer species distributed at separate depth layers, while this feature was maintained during the entire 24 h period, since no diel vertical migrations (DVM) were performed. In contrast, the crustacean community, comprised mainly by the calanoid copepod Eudiaptomus drieschi and the cladoceran Diaphanosoma orghidani, showed various patterns of DVM, being more pronounced in spring and summer. Females of E. drieschi distributed deeper than males, while the copepod nauplii were found mainly in the surface layer in all four seasons. Temperature was the most important abiotic factor affecting directly and indirectly the vertical distribution and migration of various species. During stratification, the metalimnion was the most productive layer in Lake Trichonis, having maximum values of dissolved oxygen and low transparency due to high concentration of organic matter and phytoplankton. The DVM patterns of the crustaceans indicate that the metalimnion acts probably as a daylight refuge against predation by Atherina boyeri, which is the dominant planktivorous fish in the lake.     

Concomitant diel vertical migration of a predatory leech and its amphipod prey

SUMMARY.

• 1 The concomitant diet vertical migrations of the predaceous leech Erpobdella montezuma and its pelagic amphipod prey (Hyalella montezuma) were monitored for 1 year in Montezuma Well, Arizona, U.S.A.
• 2 High densities of H. montezuma occurred in the subsurface strata of the water column during the day, but a substantial portion of the population migrated into the surface 1 m at sunset. E. montezuma remained in the lower water strata during the day, but migrated vertically after sunset to exploit the high densities of H. montezuma near the surface. Densities of E. montezuma progressively increased in the upper strata of the water column after sunset as light energy fell below 1 μEin m^?2 s^?1.
• 3 It is suggested that the synchronized nocturnal migrations of the predator E. montezuma in relation to its prey H. montezuma, increases the foraging efficiency of the leech in the highly predictable environment of Montezuma Well.

     

A mechanism of predator-mediated induction of diel vertical migration in Daphnia hyalina

Predator avoidance is generally thought to be the most importantultimate reason for diel vertical migration in zooplankton.Combining field observations and experimental results, it isshown, first, that a phototactic reaction to relative changesin light intensity is at the base of a diel vertical migrationand, secondly, how this phototaxis is enhanced by a chemicalmediated by juvenile perch.     

Quantification of diel vertical migration by micronektonic taxa in the northeast Atlantic

Analyses of day/night changes in the bathymetric distribution of micronektonic biomass at 16 stations in the northeastern Atlantic, sampled between 1978 and 1994, provided quantitative estimates of the organic carbon fluxes associated with diel vertical migration of individual taxa of micronekton. Gelatinous taxa contributed 50–80% of the integrated standing crop by volume but, apart from tunicates, contributed relatively little to the active migratory fluxes when expressed in terms of carbon. Total micronektonic migratory fluxes into the upper 200 m ranged from 12.5 to 58 mgC per m². At 15 stations, fish and pteropods provided 50–80% of the fluxes into the upper 100, 200 and 400 m. At one station, tunicates (pyrosomes) contributed substantially. Wherever tunicates or the medusa Pelagia were swarming, migrations by other taxa appear to be suppressed. The mean proportions of the stock (in terms of biomass) of each of the dominant migratory taxa entering and leaving the upper 100 m were 23% for tunicates, 18% for fish, 22% for pteropods, 8% for decapod crustaceans and 23% for euphausiids. The maximum proportions for these five taxa were 90%, 60%, 75%, 25% and 75%, respectively. Similar estimates of the mean fluxes into and out of the upper 400 m were generally higher: 19% for tunicates, 39% for fish, 28% for pteropods, 49% for decapods and 55% for euphausiids; the respective maxima were 99%, 74%, 99%, 72% and 91%. It is estimated for fish that if these migrations occur throughout the year, they will result in an active carbon export (both POC and DOC) from the wind-mixed layer and immediate sub-thermocline depths of about 500% of the mean annual standing stock. If this estimate can be extended to other taxa, then the material fluxes resulting from these active migrations will be quantitatively similar to those resulting from the deposition of phytodetritus at temperate latitudes.     

Caridina nilotica in Lake Victoria: abundance, biomass, and diel vertical migration

Caridina nilotica (Decapoda: Atyidae) in offshore waters of Lake Victoria were investigated with both day and night sampling over a period of two years. Offshore populations are mainly planktonic rather than benthic, and the animals exhibit diel vertical migrations into near-surface waters at night. These changes in diel abundance as well as the size-frequency distribution of the migrating shrimp suggest that the migratory behavior is in response to visual planktivory, because only the very smallest individuals (2–4 mm) remain in surface waters during the day. During October 1992, abundances were estimated both by vertical net sampling and by underwater video transect methods. Concordance was established between abundances estimated by the two methods. Only about 9% (night) to 14% (day) of the Caridina population appeared to be epibenthic. We suggest that the behavior of the animal is consistent with the hypothesis that it is not a strict detritivore as previously reported; rather it may engage in facultative planktivory, especially at night.     

Phosphate metabolism during diel vertical migration in the raphidophycean alga, Chattonella antiqua

The ecological advantage of diel vertical migration on the nutrition and accumulation of Chattonella antiqua, which is one of the dominant red-tide forming phytoplankton species in the Seto Inland Sea of Japan, was examined using a large axenic culture tank, in which vertical stratification of salinity, temperature and nutrients was maintained, analogous to natural conditions observed when red tides occur. C. antiqua was capable of migrating through very sharp salinity and temperature gradients. At night the species migrated to the deep nutrient-rich water and assimilated nutrients. During the daytime it migrated to the nutrient-depleted surface water and used the accumulated nutrients for photosynthesis. Nitrogen uptake was synchronized with phosphate uptake. ³¹P-NMR spectroscopy during the migration experiment revealed that C. antiqua has the capability of nocturnal phosphate uptake in the deep nutrient-rich water, but no capability of synthesizing polyphosphate, which was considered to be the intracellular phosphate pool. These findings were compared with those reported for another raphidophycean, Heterosigma akashiwo. Although both species carry out vertical migration and nocturnal nutrient uptake, only H. akashiwo has the capability of making an intracellular polyphosphate pool. This revised version was published online in July 2006 with corrections to the Cover Date.     

Distribution and diel vertical migration of the euphausiid Thysanoessa macrura in Gerlache Strait,Antarctica

Thysanoessa macrura was found throughout Gerlache Strait, Antarctica, during four surveys carried out from 30 October to 23 November 1989, with the highest abundance being 332 individuals m^–2 (0–290 m). Reproduction had begun just before the surveys took place, as indicated by the presence of females with attached spermatophores and of larvae. Thirteen-month old females were reproductive. Larvae in 9 depth strata between 0–290 m were dominated by calyptopis stages, and developed from calyptopis 1 to furcilia 1 during November. Larval abundance was not correlated to chlorophyll a concentration, which showed a consistent east-west gradient in Gerlache Strait with highest concentrations (>30 mg chlorophyll a m^–3) in bays of the Antarctic Peninsula. Survival of larvae appeared to not be affected by phytoplankton abundance. Older T. macrura showed strong diel vertical migration between the surface at night and depths to 120 m during mid-day. Larvae were consistently found in the chlorophyll a-rich upper 50 m during night (90%) and day (81%), while adults and juveniles were found in the upper 50m at night (83%), but only 16% remained there during the day.     

Observations on diurnal vertical migration and phased cell division for three coexisting marine dinoflagellates

An experiment was performed in the beginning of September 1988in the Gullmar Fjord, eastern Skagerrak, in order to study diurnalvertical migration and phased cell division for a natural phytoplanktoncommunity dominated by the dinoflagellates Prorocentrum minimum,Prorocentrum micans and Cerattum furca. A 1 80 m high and 0.30wide non-transparent PVC cylinder was filled with surface watercontaining the dominant dinoflagellates. An artificial haloclinewas created by adding high salinity, nutrient-rich bottom waterto the bottom of the cylinder Cell densities were measured atseven depths at 11 times during 48 h Physical parameters (temperature,salinity, phosphate, nitrate, ammonia and silicate) were measuredat the start and at the end of the experiment in the water columnabove and below the halocline. Strong diurnal vertical migrationpatterns were found for all three species with an aggregationof cells at the surface in the morning and during the day andat the bottom at night. The descent and ascent seemed to startbefore sunset and sunrise respectively and all species wereable to migrate through the strong artificial halocline. Somedifferences were found in the speed and timing of migrationbetween the species with P.minimum having the most pronouncedand fastest migration of the three Cell division frequency washighest at 05.00 at the bottom and also at the surface At othertimes and depths the division was always close to zero. Thedecrease in especially nitrate concentrations in the bottomwater of the cylinder suggests that these dinoflagellates arecapable of dark nitrogen assimilation.     

Predator specificity of kairomones in diel vertical migration of Daphnia: a chemical approach

Daphnia responds to chemical cues released by fish with diel vertical migration (DVM) as a behavioural predator avoidance. We used a bioassay to characterize the chemical nature of the kairomone. Cues released from stickleback ( Gasterosteus aculeatus , Gasterosteidae) and a piscivorous pike ( Esox lucius , Esocidae) were enriched from incubation water by reversed-phase sorbent extraction and were reversibly inactivated by acetylation. HPLC yielded only one active fraction with identical retention times for the kairomones of both species. Chemical features did not differ from those previously reported for Cyprinidae, indicating that the active compounds are very similar if not identical. From further investigation of the kairomone released by crucian carp ( Carassius carassius , Cyprinidae), glucuronic acids and carboxy-, sulphate- and phosphate-groups can be excluded as essential for biological activity. The response of Daphnia increased with increasing concentrations of extracted kairomone. The kairomone was not released from mucus by digestion with hyaluronidase. Adsorption of the kairomone to food particles seems to be of minor importance suggesting that the cue is perceived as a freely dissolved molecule.     

Fish and mucus-dwelling bacteria interact to produce a kairomone that induces diel vertical migration in Daphnia

1. Bacterial populations associated with fish have previously been documented to be crucial for the production of chemical signals governing the interactions between predator fish and zooplankton prey. 2. In this study, we investigated the roles of fish and mucus‐dwelling bacteria in kairomone production by conducting two sets of experiments related to elimination of bacteria with antibiotics and using fish mucus in bioassays of Daphnia pulex’s diel vertical migration. 3. Daphnia’s migratory response to the antibiotic‐treated fish was about half the strength of the response to the fish cue treatment. Furthermore, when the same antibiotic‐treated fish were removed from the antibiotic‐containing water and transferred into control water for 24 and 48 h, the extent of D. pulex’s migration depended on the length of the incubation period, apparently corresponding to the regeneration of bacterial colonies associated with mucus. The migration pattern observed in the 24 h treatment was similar to that of antibiotic‐treated fish. On the other hand, a pronounced migration occurred in the 48 h following antibiotic treatment; here, we found a higher density of fish surface dwelling bacteria than at the start of the experiment. 4. In the experiment involving fish mucus, the mucus‐enriched control water induced a weak response similar to antibiotic‐treated fish. 5. On the basis of the results from the two experiments, we suggest that both fish and fish mucus‐dwelling bacteria interact in the release of kairomone in ecologically relevant quantities.     

In situ grazing pressure and diel vertical migration of female Calanus euxinus in the Black Sea

Gut pigment and abundance of the female Calanus euxinus (Hulsemann) weremeasured from several water layers (defined by density values), with3–5 h intervals during 30 h and 21 h at a station in the southwesternBlack Sea in April and in September 1995, respectively. The female C.euxinus was observed to begin migration to the upper phytoplankton-richlayer approximately 3 or 4 hours before the sunset. Only a fraction of thefemale Calanus population (0.2% in April and 3.6% inSeptember) did not migrate but remained at the depth of the oxygen minimumzone during the nighttime. The migrating population was determined to havespent 7.5 h in the euphotic zone in April and 10.5 h in September. Thegrazing rate of female Calanus euxinus was measured from the gut contentdata collected from the layers which contain the euphotic zone. Thepercentage of primary production grazed by the female C. euxinus wascalculated as 14.5% in April and 9.5% in September. This revised version was published online in July 2006 with corrections to the Cover Date.     

The thermoregulatory function of diel vertical migration for a juvenile fish,Cottus extensus

Juvenile sculpin (Cottus extensus) less than 30 mm long exhibit a diel vertical migration in the limnetic zone of Bear Lake (Utah-Idaho). Using mid-water and bottom trawls we found that these fish inhabit the bottom of the lake (5° C) during the day but migrate 30–40 m into the water column at night where they reside in the metalimnion or epilimnion at temperatures near 13–16°C. Larger fish do not migrate into the water column. Stomach analyses demonstrated that the young-of-the-year fish do not migrate into the water column to feed: from July to October their diet is 70–93% benthic ostracods and copepods, and pelagic prey are rarely consumed. Furthermore, gut fullness of the sculpin increases through the daylight period and decreases through the night, reaching minimum levels just before the dawn descent. Laboratory experiments demonstrated that the diel migration would increase digestion rate from 3%/h at profundal temperatures, to 22%/h in the warmer surface water, thus allowing the fish to empty their guts overnight and permit feeding the following day. Additionally, sculpin held in a temperature and feeding regime that mimicked that experienced by migrating fish grew 300% faster than those reared at 5° C. Given the overwhelming importance of fast growth for juvenile fishes, a post-feeding thermotaxs that increases digestion may be a common phenomenon increasing growth, and affecting the distribution and bioenergetic relationships of fish.