Vertical Migration Rhythms Research Articles

Diel vertical migration and feeding rhythm of copepods under sea ice at Saroma-ko Lagoon

Abstract Diel vertical migration and feeding rhythm of copepods were investigated in Saroma-ko Lagoon, Japan, one of the southernmost areas covered by seasonal sea ice in the Northern Hemisphere. Copepods were collected under sea ice every 4 h for 24 h at five depths (0, 1, 3, 6 and 9 m from the under-surface of the sea ice) to examine their density and ingestion rate. Distinct changes in the vertical distribution and ingestion rate of copepods were observed at dusk, when they migrated upward from the near-bottom layer to the food-abundant sub-ice layer. However, most copepods left the food-abundant sub-ice layer by midnight and reached near bottom again before sunrise. The ingestion rates of copepods increased after sunset throughout the water column as in areas without ice cover. The ingestion rates at the food-poor near-bottom layer were higher than those during the day in the food-abundant sub-ice layer. The estimated grazing rate by zooplankton, predominately copepods, was between 0.056 and 0.08% of the chlorophyll standing stock in the water column per day. This estimate is lower than that observed under Arctic sea ice, due to the lower biomass of copepods under sea ice at Saroma-ko Lagoon.

Heritability of circatidal vertical migration rhythms in zoea larvae of the crab Carcinus maenas (L.)

Previous studies showed that in the crab Carcinus maenas, endogenous circatidal vertical migration rhythms are exhibited by zoea-1 collected from the field and by larvae newly hatched in the laboratory from field collected ovigerous females. In the present studies, non-ovigerous females were brought into laboratory and kept in non-tidal conditions until eggs were produced. About 100 such females spawned in the laboratory during 1992–1994. Observations were then made on swimming behaviour patterns of groups of larvae hatched, either naturally or from detached eggs, from more than 20 of these laboratory-spawned females, some of which had been kept in the laboratory for nearly a year and one of which spawned twice with an interval of 8 months. Most groups of larvae hatched under such circumstances exhibited vertical migration rhythms of circatidal periodicity despite never having experienced tidal conditions in their life time, even as embryos. Such behaviour is particularly surprising in larvae hatched from detached egg masses. The results indicate that the periodicity of larval circatidal rhythms is inherited and raise the question as to how such rhythms are synchronised. In exceptional cases larvae hatched from detached eggs of two laboratory-spawned females, and which had been incubated under light-dark cycles, showed weak circadian swimming rhythms. In contrast, exposure of detached eggs from one of those females to successive 2 h episodes of water agitation every 12 h, resulted in expression of circatidal rhythmicity in the newly hatched larvae. This simulated tidal agitation appears to mimic the mechanical stimulation produced by females during the hatching process which has been shown previously to set phase of the larval circatidal swimming rhythms. Synchronisation of circatidal migration rhythms in larvae hatched from detached eggs remains speculative but could occur by mutual entrainment. The study appears to be the first to demonstrate artificial entrainment of a circatidal rhythm in a planktonic organism.

Daily and seasonal vertical migration rhythms in Daphnia

1. Clones of Daphnia longispina (O.F.M.), collected from ponds with different levels of predation, were monitored using video techniques in order to test the effects of temperature and visual cues on vertical migration behaviour.2. Endogenous rhythms were found to have a part in the control of vertical migration in some clones but responses were highly variable.3. Low temperature caused a marked increase in the amplitude of vertical migration in D. longispina, consistent with field studies.4. Clones from ponds with fish predators had larger vertical migration amplitudes than clones from ponds with no fish, providing further evidence for the genetic basis of this mechanism.

Synchronization of endogenous tidal vertical migration rhythms in laboratory-hatched larvae of the crab Carcinus maenas

Previous studies showed that freshly collected zoea-1 larvae of the shore crab Carcinus maenas from coastal waters possessed endogenous circatidal vertical migration rhythms. Present experiments demonstrate that zoea-1 larvae released by crabs which extruded eggs in the field but were then kept in laboratory constant conditions since collection, also exhibited endogenous circatidal vertical migration rhythms. Such rhythms were shown by newly hatched larvae from nearly all of 50 females which released larvae in the laboratory, some of which had carried eggs in the laboratory for up to 3–4 months. Thus, since entrainment by tidal variables could not have occurred during embryonic development in these cases, other synchronising factors must set the phase of the larval circatidal rhythms. Present results suggest that the hatching process itself is the main synchroniser; upward swimming occurred just after hatching and at 12.4 h intervals thereafter. This is consistent with previous observations of peak hatching in Carcinus primarily around nocturnal high tide, with larvae in the field exhibiting tidal vertical migration rhythms of ebb-phased upward swimming associated with dispersal during ebbing tides. The results appear to be the first to characterize a synchroniser for tidal swimming rhythms of planktonic larvae and to provide experimental evidence that the hatching process can serve as the synchroniser for a larval swimming rhythm.

Occurrence in coastal waters and endogenous tidal swimming rhythms of late megalopae of the shore crab Carcinus maenas:implications for onshore recruitment

Previous studies have shown that newly released zoea larvae of the shore crab Carcinus maenas (L.) exhibit ebb-phased tidal vertical migration rhythms of upward swimming associated with transport offshore in ebb tidal flows. This gives rise to the question as to how later larvae of the species return to the intertidal zone. Repeated surface plankton sampling in coastal waters revealed that megalopae, the last larval stage of the crab, swarmed in surface waters mainly during flood tides and particularly at night. It is likely that flood-phased upward swimming ensures onshore transport of the larvae. Employing an infra-red actography system, endogenous circatidal rhythms of swimming activity were detected in constant laboratory conditions in freshly collected megalopae from inshore waters. However, in such conditions, upward swimming occurred at the times of expected ebb, not flood. It is proposed that inshore flood transport of megalopae is driven primarily by exogenous factors, which result in swarming of pre-moult megalopae towards the upper intertidal zone where settlement of first stage juvenile crabs occurs. It is suggested that the ebb-phased endogenous circatidal rhythm of upward swimming is adaptive in reducing the risk of premature stranding of megalopae, permitting them to oscillate between the intertidal and near shore waters until moulting is imminent and a suitable substratum is encountered. Of megalopae collected in inshore coastal waters, and maintained in the laboratory at water temperatures close to those of the field, nearly 60% moulted in 2 d, 95% in 4 d and 100% in 7 d after collection. Since the average development time for C. maenas megalopae is reported to be 13 d, the data provide evidence that only late megalopae return to coastal areas.

THE SPEED OF DIATOM MIGRATION THROUGH NATURAL AND ARTIFICIAL SUBSTRATA

The speed of diatom locomotion during cell migration was investigated in laboratory experiments using natural assemblages of intertidal diatoms inhabiting the upper intertidal mudflat at Portishead on the Severn Estuary in winter. Persistent vertical migration rhythms were verified for the epipelic diatom assemblages in the field and the migratory behaviour was successfully maintained in a tidal laboratory experimental system. No migratory behaviour was apparent for salt marsh assemblages at the same site and a brief investigation indicated that this behaviour was not overtly related to the water content of the sediments. The dominant diatom on the intertidal mudflat at the time of the investigation was Gyrosigma spencerii (W. Smith) Cleve which was used for the investigation of locomotion through sediments. Initial measurements of surface progression were made which compared well with values taken from the literature. G. spencerii was found to move over an artificial sediment (kaolin) at an average speed of 4.7 μms−1. Migration speed through, rather than over, kaolin and natural sediment was examined by deposition of kaolin and sediment, free from diatoms, onto the surface of diatom assemblages inhabiting cores of natural sediment maintained in the laboratory. Determination of the thickness of the deposited layer by freeze-fracture techniques allowed the calculation of the rate of upward movement. The results suggest much lower locomotion speeds for diatoms moving through substrata than on horizontal surfaces. Vertical migration of G. spencerii was found to be 25 times slower than surface speeds over kaolin and natural sediment with average values of 0.17 and 0.19 μms−1, respectively. Diatom species showed a synchronous emergence at the surface of the sediments with G. spencerii first to appear. The significance of these findings to diatom microspatial vertical distribution within sediment, endogenous rhythmic behaviour, frustule streamlining and energy budgets are discussed.

RHYTHMS OF VERTICAL MIGRATION AND MOTILITY IN INTERTIDAL BENTHIC DIATOMS WITH PARTICULAR REFERENCE TOPLEUROSIGMA ANGULATUM

The surface population densities of epipelic algae inhabiting the intertidal mud of the Menai Straits were studied in the field during low water exposure of the sediment. Navicula cf. miniscula, Pleurosigma angulatum and Gyrosigma sp. migrated onto the surface of the sediment following tidal exposure and burrowed back into the mud prior to inundation by the incoming tide during the day; decrease in incident irradiance at dusk during periods of tidal exposure of the sampling sites also resulted in movement of the diatoms back into the sediment. In conditions of constant irradiance and temperature in the laboratory away from the influence of tides, the rhythm of vertical migration in and out of the sediment was maintained for eight days. This rhythm was therefore endogenous and it remained tidal: the rhythm of vertical movement remaining in phase with the tidal exposure of the field sites. As the time of low tide approached the evening, the migration of P. angulatum became rephased, involving movement of th...

VERTICAL MIGRATION RHYTHMS OF NEWLY HATCHED LARVAE OF THE ESTUARINE CRAB,RHITHROPANOPEUS HARRISII

Zoea larvae of the estuarine crab Rhithropanopeus harrisii were maintained in constant conditions in the laboratory, and their vertical migrations were followed for two or more days. Larvae which hatched in the laboratory, but which underwent embryonic development in an estuary having semidiurnal tides, often expressed circatidal rhythms in vertical migration. However, first-stage zoea larvae collected by plankton net in the same estuary had circatidal vertical migration rhythms of much greater amplitude and with a constant phase with respect to the natural tidal cycle. Laboratory-hatched larvae of crabs from an estuary with aperiodic tides had more variable vertical migrations, and field-caught larvae from the same habitat never expressed clear migration rhythms. When reared to the third zoeal stage in the laboratory under a diel light:dark cycle, larvae from both estuaries usually migrated arhythmically under constant conditions. Vertical migration rhythms of larvae of this species appear to be strongly predisposed to entrainment by natural tidal cues. Such migrations probably contribute to estuarine retention of the developing larvae.

Tidal Vertical Migration: An Endogenous Rhythm in Estuarine Crab Larvae

Field-caught larvae of the estuarine crab Rhithropanopeus harrisii have a tidal rhythm of vertical migration when maintained in constant conditions. Laboratory-reared larvae do not show this rhythm. Endogenous tidal vertical migrations aid the retention of these planktonic larvae in estuaries near the parent populations.

On rhythmic movement of the diatomAmphora ovalis

The vertical migration, motility and cell division rhythms of the diatom Amphora ovalis Kutz from Lake Kinneret, Israel, have been studied under laboratory conditions and results compared with comparable rhythms of other unicellular algae. The vertical migration rhythm exhibits two peaks during the light period, both when the cells are kept in continuous light or continuous dark. There is a single peak of motility occurring in the first half of the natural light period and a single peak of cell division in the latter half of the dark period. Rephasing of the rhythm by means of delayed start up time is illustrated and the possible interaction of phototactic and geotactic rhythms discussed.

Vertical migration rhythm in freshwater diatoms

Epipelic diatoms of a pond undergo a vertical migration rhythm moving to the surface of the sediment in the morning and downwards again in the afternoon.

Phototaxis by the dinoflagellate Gymnodinium splendens Lebour.

SYNOPSISA microscope‐television system was used to monitor quantitatively the behavior of Gymnodinium splendens Lebour in response to light. The predominant behavioral sequence upon stimulation is (a) an initial 2–5 sec cessation of movement (stop‐response) followed by (b) positive phototaxis. The action spectra for each response are identical, having maxima at 450 and 280 nm. Upon measuring the percent response to a range of stimulus intensities, it is apparent that a stop‐response is not a behavioral prerequisite for phototaxis. An identical circadian rhythm in photoresponsiveness is observed for phototaxis and for the stop‐response with greatest light sensitivity occurring during the first 4 hr of the entrained light period. The implication of phototactic sensitivity and the phototactic circadian rhythm in diurnal vertical migration is discussed.

TIDAL RHYTHMS: THE CLOCK CONTROL OF THE RHYTHMIC PHYSIOLOGY OF MARINE ORGANISMS

TIDAL RHYTHMS: THE CLOCK CONTROL OF THE RHYTHMIC PHYSIOLOGY OF MARINE ORGANISMS

Photosynthetic rhythms in epipelic algal populations

Laboratory studies using freshwater and intertidal epipelic algal populations have shown that the vertical-migration rhythm displayed by the populations is in phase with a rhythmic change in the photosynthetic capacity. These rhythms are diurnal for freshwater algae and tidal superimposed on diurnal for intertidal algae. Maxima of cell emergence and photosynthetic capacity are coincident but the increase in photosynthetic capacity precedes cell emergence. Decreasing photosynthetic capacity occurs at a constant light intensity, increasing photosynthetic capacity occurs both in the light and the dark. These changes are thought to reflect changes in rate of the light reactions of photosynthesis.

Light intensity and the vertical distribution of algae in tertiary oxidation ponds

Studies on the use of oxidation ponds for the tertiary treatment of municipal waste waters had shown that solar heating results in thermal stratification. Under these conditions there is probable short circuiting of flow. Installation of weirs to minimize stratification by forcing an under-over flow pattern was followed by the development of two distinct algal associations as a result of the skimming action of the surface weir. Upstream of the surface weir a thick algal mat developed which consisted of an interlocking complex of cysts of Euglena rostifera Johnson and filaments of Oscillatoria tenuis. Downstream of the skimming weir, the surface of the pond was free of the mat but deep green in appearance. This color was due to a population of a single species, Euglena rostifera. The green color of the clear pond areas was observed to change considerably in intensity in the course of the diurnal cycle. Detailed investigation of this phenomena revealed a vertical migration rhythm of the Euglena associated with the diurnal cycle. Examination of the diurnal migration and associated factors showed the following: 1. (1) The Euglena moved from the bottom sludge, where it settles at night to levels in the pond where light intensity measurements did not exceed 75 c ft −2. 2. (2) Diurnal temperature changes did not affect the vertical migration of the Euglena. 3. (3) Under the algal mat, consisting of Oscillatoria tenuis and encysted Euglena rostifera, there was no vertical migration. Isolation and growth of single cell isolates of E. rostifera showed that optimum growth was at the same light intensity range found in the ponds where the maximum populations were located. At higher light intensities the proportions of chlorophylls a, b, and c decreased and carotenoid pigments increased. Growth in total darkness produced complete loss of chlorophylls but also a sharp increase in carotenoid pigments.

PERSISTENT, VERTICAL-MIGRATION RHYTHMS IN BENTHIC MICROFLORA. VI. THE TIDAL AND DIURNAL NATURE OF THE RHYTHM IN THE DIATOM HANTZSCHIA VIRGATA

1. The diatom, Hantzschia virgata, appears on the surface sands of Barnstable Harbor, Mass., during daytime low tides. Surface accumulations of this organism reach such concentrations that the sand takes on a golden-brown color. As the tide returns the cells re-burrow into the sand.2. The cells can be prevented from emerging onto the surface sands at low tide by artificially darkening the area with an opaque covering just as the tide recedes. Cells already on the surface can be made to re-burrow by similarly placing them in darkness.3. The vertical-migration rhythm will persist in the laboratory in constant illumination, constant temperature, and away from the influence of the tide for as long as eleven days. During this time the cells remain in approximate synchrony with the feral cells in nature.4. In nature, when the times of low tide approach sunset, the cells rephase their rhythm to the early morning hours of daylight. Cells collected during late afternoon low tides and returned to L:D or L:L in the laboratory, undergo a similar rephasing in an interval of just three days.5. To explain the various unique properties of this rhythm, it is postulated that the rhythm is a manifestation of an interacting dual-clock system: a lunar-day clock which measures periods of 24.8 hours and is responsible for a bimodal migration rhythm; and a solar-day clock responsible for the suppression of the night-time supra-surface phase of the migration rhythm.

Persistent, vertical-migration rhythms in benthic microflora. 1. The effect of light and temperature on the rhythmic behaviour of Euglena obtusa: Palmer John D. and Frank E. Round, 1965. J. mar. biol. Ass., U.K., 45 (3): 567–582

Persistent, vertical-migration rhythms in benthic microflora. 1. The effect of light and temperature on the rhythmic behaviour of Euglena obtusa: Palmer John D. and Frank E. Round, 1965. J. mar. biol. Ass., U.K., 45 (3): 567–582

Persistent, vertical-migration rhythms in benthic microflora: I. The effect of light and temperature on the rhythmic behaviour of Euglena obtusa

During daytime low tides on the River Avon at Bristol, England, the exposed river banks become a deep green colour owing to the presence of enormous numbers of Euglena obtusa which emerge out of the black mud. Cell densities on the surface surpass 105 cells/cm2. Before the tide returns to cover the area, the cells re-burrow back into the mud and remain there during high tide and throughout the night.The cells can be prevented from emerging on to the surface mud at low tide by artificially darkening the area with an opaque covering just as the tide recedes. Cells which are already on the surface can be made to re-burrow by similarly placing them in darkness.The vertical-migration rhythm will persist in the laboratory in constant illumi-nation, constant temperature, and away from the influence of the tide, for nearly one month. In these conditions the rhythm is diurnal, rather than tidal. The rhythm will not persist in constant darkness.Because of the excessive turbidity of Avon water, each high tide imposes a period of darkness on the surface mud. It is thought that these dark periods transform the fundamental diurnal rhythm into one of tidal frequency.Various intensities of constant illumination alter the form and amplitude of the rhythm, but not the period. The stable nature of the period, under different light intensities, is thought to be due to a unique, self-stabilizing feature inherent in this type of rhythm.The rhythm is inhibited at 2° C. Between 5° and 15° C, the period of the rhythm is virtually unaltered; it remains approximately 24 h in length.